1. Introduction
1.1 What You Will Find in this Hyperscript
1.1.1 The "What" Questions
1.1.2 The "Why" Questions

1.2 How This Hyperscript Works
1.2.1 A Word to the Style of Writing
1.2.2 How to Use this Hyperscript

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1. Introduction
1.1 What You Will Find in this Hyperscript

1.1.1 The "What" Questions
If you have ever tried to get some information about swords and steel, the Internet provided you with plenty of stuff. You
have found hardcore science articles, more or less incomprehensible, and straight balderdash, to use a polite word thatstarts with "b". Between those extremes you ran across many good contributions. Some dealt with general points aboutsteel technology or sword making, and others revolved around some special topics like "wootz steel", "martensite", or"carbon and hardness". If you are not sure about some of the terms I'm using here, refer to the "glossary" module orthe "Index".
In general, many good articles can be found that are descriptive. They deal mostly with what I am going to call the"what" questions. They answer questions you might have in a descriptive or empirical way. Sometimes they
explain something not-so-clear by referring to something that is actually completely unclear but sounds or looks
good.
Let's look at a few examples of good questions and typical answers:
What is steel? Iron with a little bit of carbon in it!
A perfectly true answer. It is even useful, provided you have some idea about
what iron and carbon is. Now you know that mixing iron and carbon might
get you steel. But you still do not know anything about steel.
What is a "Berliner Weiße"? Beer with some raspberry syrup in it!
Once more a perfectly true answer. It is even useful, provided you havesome idea about what beer and raspberry syrup is. Mix the stuff and you get
a Berliner Weiße. However, as long as you didn't taste a Berliner Weiße,
you still don't know anything about it.
What is carbon doing in iron? Making it harder!
What is raspberry syrup doing in beer? Making it tastier!

Basic
ModuleGlossary

Aha! You get the idea now. Let's go on.
What is the advantage of damascene technology? It combines hard and brittle steel with soft and toughsteel, producing hard and tough steel!
What is the advantage of a Berliner Weiße? It combines the best of beer and juice!

Aha once more! You got answers. But are they true? Mixing something might also bring out the undesirable
properties of the constituents, after all. You rarely run across "cheese and spinach ice cream", for example.
To get closer to the truth, you first need to define and measure the properties "harder" or "tastier". But let's go on:
What is wootz steel? Some kind of more or less mysterious ancient Indian high-carbon steel with special
properties from which superior blades with a "watered pattern" could be produced! Good answer. Now you
know. Or do you?
What happens if you "quench" (rapidly cool) hot steel? It gets very hard because somehow martensite isformed!
What is martensite? A particular hard kind of steel. Aha.
I guess you get the idea by now. None of the answers is totally wrong but none of the answers really explains much.
They deal with the matter the same way you deal with your child when it asks: "what is this bird?" Your answer mightbe: "a sparrow". Your child will be satisfied—but it hasn't really learned a thing about sparrows. How they live, what kindof nest they build, how they raise their young, if the couple stays together or just meets accidentally for raising offspring,
what they eat, if they migrate south in the winter, how they relate to other birds, and so on and so forth. Having a namefor something does not mean that you know anything about the thing you named (except, of course, if you know thehidden "true name").
Your child, by the way, probably would also have been satisfied by answers like: "a sperling" (German for sparrow),"some kind of finch" (correct) or "it's a young thrush; it will grow bigger when it gets older" (wrong, but plausible to achild and probably many adults).

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Have you ever been satisfied with answers like those above to your questions about steel? Could you tell if
somebody giving those answers was out of his depth? How can your child tell that you are out of your depth when
you provide answers to its questions? In particular, when you're not even sure yourself if your answer is right orwrong—after all, a sparrow might be some kind of thrush. Your child can't tell. Neither can you, the non-scientists
out there, when you encounter information to steel and swords that is a bit off or just wrong but looks reasonable.
You find this kind of (mis)information for example in all museums—without fail!
Being a Materials Scientist who practiced and taught the field for many years, I do notice if what I read about steel andswords is wrong or not quite convincing.
However, there is no such thing as complete knowledge when it comes to the nitty-gritty. I do not claim that I know all
there is to know about iron, steel and swords. I'm very grateful about this because scientists like me would not be able
to hold nice jobs if everything there is to know about steel (or aluminum, or silicon, or superconductors, or organic
semiconductors, or ...) would be already known.
This means that I have to make educated guesses on occasion because I don't know for sure. I even might be proved
wrong here and there. Either because what scientists think they know at present about some particular topic will prove
to be not quite correct in the future (then I couldn't know better) or because I personally got it wrong or presented it
somewhat skewed (more likely).
Rest assured, however, that there will be no major mistakes in the core of what you will read here.
One day in the not too distant future we shall know (almost) all there is to know about steel. However, we will neverknow all there is to know about swords for the simple reason that most swords forged in the past do not exist
anymore. They have died and turned to rust, achieving steel nirvana. At best they left a rust-colored spot in theearth.
The same is true for the people who made and used them. They are all dead too. Most of them didn't leave a single
trace. From a few we might find a bone or two but that will not tell us much about the person and how he made orused swords.
So as soon as I look back into ancient times, without much recorded history and few surviving iron artifacts, I needto do what all historians do:

I guess a lot

However, I don't just make wild guesses but educated guesses like serious archeologists and historians. Thatmeans that I do take into account all the information accrued over the years from analyzing artifacts and the ancient
lore that has survived. While I certainly know far less about that than professional archeologists or historians, I cancompensate this deplorable weakness to some extent by knowing more about what can be done, and what cannot
be done, with materials like iron and steel.
Now let's look at the hard questions, the "why and how" questions. This Hyperscript is about the answers to thosequestions. Let's look at the "what is?" questions from above once more but now with with why and how in mind:
So a little bit of carbon makes iron hard? Indeed—but why? And how ?
Why, if you put a bit more carbon into your iron than just "a little bit" (to be more precise: more than about 1 %), will
it now tend to be brittle?
Why does carbon harden iron while sulfur does not? How about phosphorous? Or boron, oxygen, lead or some ofthe other easily available 80 elements from the periodic table?
Why are damascene swords supposed to combine just the good properties of the two kinds of steel they are madefrom, and not the bad ones? Or do they?

Did you miss something? No? You're not paying attention. A written something of this kind usually comes with apreface where the author goes on and on about his inner workings and who contributed to his work. I spared you that.
Well—not quite. Here it is.

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1.1.2 The "Why" Questions
In this Hyperscript I will focus on "why questions". I need to take you to the very roots of Materials Science so you canunderstand the answers. We need to talk about atoms, why they stick together to form iron or steel in the structure of acrystal, and how defects in this crystal determine some of the important properties of iron. Things like the second law ofthermodynamics, phase diagrams, precipitates and dislocations will come up.
Some of you may not have encountered these fancy words before; some of you might see them as synonymous for"boring" or "things I will never understand". Don't worry, be happy! I will introduce those things patiently, slowly
and—promise! —without math. You will understand to the extent you should, and I will do my best not to make itboring.
So do not worry about fancy words coming up that you do not (yet) understand. What you should worry about isthat you probably don't know the exact meaning of some everyday words like temperature or hardness.
Funny enough, it appears that going to the very roots of those simple "why" questions has never been done before
for a general, non-specialist readership. Nobody thought it worthwhile to tell you in sufficient detail about swords,
metals and steel. There are good reasons for this.
1. It is not something easily done.
2. There is not much to be gained in terms of scientific recognition. My peers in the science community will
hardly take notice of what I'm doing here.
3. Lack of scientific recognition can always be compensated by large amounts of money. But there isn't muchmoney in a hyperscript (or paper book) about iron, steel and swords either.
4. Some years ago, interest in swords and sword lore was not keen, and active smiths were almost extinct. So
why bother?
5. It's a lot of work and takes a lot of time out of doing science or drinking beer, whatever comes first.
Item 4 has changed in recent years, about the others I'm not so sure. But it looks to me that the time might havecome, when an in-depth hyperscript about iron, steel and swords might be appreciated by enough people to makewriting it worthwhile.
I do acknowledge some valiant efforts to address the general matter by somescientists. Take, for example, the books of Rolf Hummel or Steve Sass, two
authors I know and esteem. However, they did not go deeply enough into thematter I want to pursue here. This link gives some information about some books I
have read and that might benefit you too.
It also gives a few of the major Internet sources that I used and that are of interestfor the whole Hyperscript.

ScienceModuleBooks

The science behind many everyday topics was never properly explained to a general readership. But interestingly
enough, a lot of effort has been made to educate you, the average reader, about far-out stuff like black holes, time
travel through worm holes, exotic elementary particles like the naked bottom quark (one of my daughters was quite
stricken with it), string theories in 11 dimensions, or the big bang at the beginning of the universe.
Take "The Grand Design", the newest book of Stephen Hawking. It is actually frowned upon in the physics
community—so why did Steven write it? I don't know but can think of several good reasons:Because it was fun to do.
Because being the physics celebrity in polite (but ignorant) society feels good (even if your colleagues give
you those looks).
Because you feel that it's your duty to educate as many as possible about the subject dearest to you.
And, perhaps, because there is a lot of money in any book you write—if you are Steven Hawkings.
I let you guess at my reasons for writing this book. Drink (lots of) your favored beverage while you guess, and you
may get closer to the truth.
The "what is " questions around iron, steel and swords have been discussed in many good books and publications forquite some time, in contrast to the "why " questions. A lot of more or less superficial answers have been supplied aswell.
The emphasize here is on "good". I most certainly don't want to imply that a book is automatically bad if it does notaddress the deepest layers of knowledge about its topic. Just before 1900, for example, Ludwig Beck wrote "DieGeschichte des Eisens" (The history of iron). The 5 ponderous volumes still provide for good reading (provided you're
fluent in German) even so the author never answers any of the "why" questions from above. He wasn't stupid or lazy;
he simply couldn't—the answers weren't in around 1900.
In the 1962 book of T. A. Wertime, entitled "The Coming of the Age of Steel", you will not find key words like"dislocations ", "precipitates" or "phase diagram". The importance of whatever those terms mean for really
understanding steel (or just about any metal) was known by then—but only by some scientists, and not yet by theengineers. Nevertheless, Wertime's book still provides for good reading.

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I could go on enumerating and discussing books and articles forever, but I won't. I have made my point. Also, to behonest, I haven't read most of the books about iron, steel and swords that are out there. Nobody has; there are simply
too many. I will, however, refer to some of the literature that was relevant for me in footnotes.
So please note that I'm not even remotely saying that books dealing on an empirical level with iron, steel and the artof sword making are worthless, outdated, unscientific or wrong, and that it's me, and only me, who gives you thegood stuff. Quite the opposite. Some of the people who wrote these books actually might be able to make steel or
to forge a sword—in pronounced contrast to me. Many authors certainly know far more about some science issue
than I do, for example about the thermodynamics or mechanics of steel. Then there are people who can wield asword in a fight and thus are far better judges of the fighting quality of a sword than I am.
On the other hand, many engineers and scientists involved in actually making steel probably know less about thebasic principles behind steel properties than I do. The reason is simple. You don't need to know all the fundamental
stuff for producing all kinds of steel and to make the most amazing things with steel. Scientific knowledge aboutiron, steel and just about all other materials emerged in the 19th century and was consolidated no earlier thanaround 1960. Yet more than 2000 year before that time some artisan-artists already made most amazing steel
product: swords.
Looking at steel before about 1960, one looked at the empirical knowledge gained during the last 2000 years or so, plus
some insights from classical physics disciplines like mechanics and thermodynamics that emerged in the 17th century.
Before (roughly) 1960 only a few theoretical Materials Science specialists (who could not have forged a sword if their live
depended on it) knew the fundamental answers to the "why" questions raised above. These guys had some ideas about
our topic because they actually discovered the scientific principles that allow us to answers the "why" questions now.
Of course, you have never heard their names. You wouldn't even connect scientists whose names you have heard to
steel and sword making. Galileo Galilei and steel? Albert Einstein and steel? Well, we shall see (provided you keep
reading).
Let me emphasize again that there are still scientists and engineers out there that work with steel but do not knowmuch more about steel then what I'm going to tell you here. They simply don't need to know that for doing their jobs.
Understanding iron and steel on the level I will pursue here is not yet going to help you very much in making
thousands of tons of steel every day, fine objects like swords or sewing needles, or the landing gear of a Jumbo jet.
For making a baby you don't need to know the working of nature on the deepest level either. It might even distract
you from your enterprise if you think too much about what the DNA of your sperm (or egg; I'm certainly not writing
this only for the males of the species) is going to do in the near future.
Nevertheless, if you want to get the ultimate answers to the "why" questions, you must go to rock bottom—and down
there you find the atoms. All properties of steel derive from the way its atoms hang together.
So nothing helps. You first need to know a bit about atoms—that they really and truly exist, for example—and someof the tricks involved in making solids by sticking a lot of atoms together. If you don't know about the breakthroughs
in science made in the first half of the 20th century, let's say Albert Einstein (here he is again!) proving once andforever the reality of atoms, you simply cannot understand the answers to the "why" questions.
I grant you that it is more fun making a baby than understanding exactly how it comes into being. I don't want tokeep you from making babies or just practising it, nor from forging your sword. But it won't hurt to read up a bit on
the "theory" of whatever you are doing, whenever you take a break. It actually might be entertaining or just plain old
fun. Try me.
Considering that it takes a while before discoveries in basic physics trickle down to engineering (especially if a world
war provides for some distraction), the year 1960 may be seen as a fuzzy starting point for the emergence ofMaterials Science, the science that investigates and understands properties of all materials (including steel) on the
deepest possible level.
You got it by now. Only by looking at the very atoms that constitute a piece of steel (and anything else) we will beempowered to understand the properties of steel (and everything else) on the deepest and most fundamental level. So
what I'm going to do in this book is to look at the atoms. And if I say "look", I mean it.
I will ask and answer the "why" and "how" questions that come up as soon as we look at steel from the viewpoint of
the atoms in the steel. Going into the depth of this matter, far more "why" questions of a more general type will
come up than you would have imagined in your wildest dreams. Why do things melt?, for example. I'm also going toaddress these deceptively simple questions in some detail.
Dear reader, I assume that you are not overly familiar with quantum theory, statistical thermodynamics, chemistry,
crystallography, metallography, electron microscopy, and all the other topics that are at the heart of "Materials
Science and Technology", the discipline that deals with topics like steel forging or semiconductor technology. Taking
you to the very roots of steel technology without cutting corners thus will not be a quick and easy undertaking.
I strongly believe that it can be done, however, and what follows is my first shot at this issue. If you will come withme I will take you on a long and (I hope) fascinating journey to the very roots of our civilization. Because that's what
Materials Science and Technology is! Without "technical" materials like wood, fur, leather, flintstone, bronze, iron,and combinations like pianos, Mercedeses, microchips, (I skipped a few development stages), there is no
civilization.
I'll try to make it easy reading. But let's not fool ourselves: it will be an arduous journey with pitfalls and strenuous
uphill walks.

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If you make it to the end, you will be wiser but also a bit exhausted. That is only natural. The rewards for yourperseverance will include a much better appreciation of the beauty of swords and of the artistry that went onto theirmaking. You will also have a better understanding and appreciation of all the many metal things that you use everyday (I hope this doesn't include a sword), and of some other key materials like silicon. In short:

You will have a better understandingof your culture.

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1.2 How This Hyperscript Works

1.2.1 A Word to the Style of Writing
If you have ever seen a scientific paper, you have already noticed that my style here is quite different from proper
scientific diction. I will continue in this way. I will make a point of writing in a very unscientific style, risking the scorn of
my peers.
There won't be plenty of footnotes. There won't be disclaimers to every statement either, discussing the exceptions
to the rules.
I'm also going to address you directly, and I will ask you to just believe me most of the time rather than hiding
myself behind unassailable authorities that I quote a lot.
The basic idea is to present the topic in such a way that everybody with a halfway decent general education canfollow my train of thoughts.
Since in my experience even a fully decent general education no longer includes some non-trivial math (defined asanything beyond counting to hundred), there will be no equations in these pages. Equations will appear, however,in the "Science" part of the hyperscript.
I also will be redundant to some extend. I won't throw big ideas at you just so; I will lead up to them gradually, and I
will mention key concepts more than once.
Moreover, I promise to do my best to make this easy reading, if not outright entertaining. There will be little
anecdotes, some jokes, frequent "by the way's", some irony or tongue-in-cheek, and some really weird hidden
modules that you need to make an effort to find.
Now and then we will also take a quick look into some related materials science terrain, in particular silicon microelectronics will come up more than once.
Finally, I will spice the whole thing with a bit of my "philosophy" on occasion. I will also lash out at some
philosophers, scientists or museums if I think they earned it (or if it's fun to do).
The first law of thermodynamics states that there is no such thing as a free lunch. You can't get easy reading for freeeither; there is a price to pay for not being scientific.
Niels Bohr, one of the celebrated fathers of the quantum theory, always maintained that clarity and truth arecomplementary like the two sides of a coin. Bohr based quantum theory on his "complementary principle", so heshould know. In other words, you can't have your cake and eat it.
In this article I go for clarity. That does not mean that I'm going to make things up just to make it easy reading. It
does mean that I'm going to simplify things as far as possible, loosing scientific rigor in the process on occasion.
Just to give you an idea what more scientific rigor would look like, some topics are dealt with in parallel in a morescientific way in the "Science" part, including equations and proper terminology. You can switch back and forth
simply by activating a link. If you choose not to activate these links, for example because you are afraid that yourgirl friend might catch you looking at complex equations, which will induce her to dump you because she suspects
concealed nerdiness, that's fine with me. The science part is not needed to understand the main part of this
hyperscript.
To make for easy reading, there will be almost no footnotes. Instead I give you all kinds of secondary information bylinks or right in the Hyperscript. Details can be found in this link
The format of this hyperscript will be dealt with in the next paragraph.

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1.2.2 How to Use this Hyperscript
Specialities in the Text
If you have read so far you noticed that there are some recurring peculiarities in the format of the hyperscript.
There are all thoseandsigns structuring the flow of prose in a somewhat hierarchic way:

= main topic,= subtopics.
Those symbols have no particular meaning and just express my personal feeling that long texts are hard to read ona screen. They are simply supposed to make reading easier.
Some words are black and bold. This means that you will find exactly these words in the key word Index of thescript. If you click on any word or short sentence in the index, you jump to the bold-faced word in the text.
Some words are red and bold . This means that you will find exactly these words, which are always last names, in
the Name Index of the script.
Some terms are bold and italic. That means there is a German translation for that word that appears if you holdthe cursor on it. You can also look it up in the dictionary.
Some abbr. are also bold and italic. That means there is an explanation for that word that appears if you hold the
cursor on it. You can also look it up in the Abbreviation Index files.
Some words are in red italics. That simply intends to emphasize those words or sentences in the text.

Sentences in this green box are really important.

A little blue box like this one emphasizes a link to a major module that is relevantto the topic in the main text in one of the other columns of the content matrix or, as
I call it, the module matrix of this hyperscript . You may not agree to my choice ofwhat is relevant but that's your problem.
What I mean with "column in the module matrix" will become clear if you activate
the link in the box and look around.

Link
Matrix ofModules

There are far more links in the hyperscript than just the ones in the blue box. They lead to less important modules in
one of the other columns or to earlier modules in the main or backbone column. They are kept unobtrusive in orderto keep the text blocks from looking too unruly.
The menu provides for easy access to the main parts of the hyperscript. If there is no menu on the left, click on "Menue"
on top of the Hyperscript or the
button at the bottom of the page.
All but one of the menu entries are self-explaining; just click on it if you are in doubt. The entry "Project", however, is not
so much for you but for me. It helps me to keep track of what I'm doing and identifies problems that need to be fixed.
I need that "project" information because:

A Hyperscript is never finished!

In contrast to writing a printed book, I can constantly change, correct, update, amend, augment or embellish it. And
as long as it is fun I will keep doing that.

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Structure of the Hyperscript
The menu has an entry called "Module Matrix". This is the most important button for accessing this Hyperscript in a
general way.
If you click on it, a large table opens up. It looks basically like this:Basics

Backbone

Science

Illustrations

Word and pdf

Miscellaneous

1. Introduction
1.1 What You Will Find in this Hyperscript
b1_1_1Glossaryb1_1_2
Periodic tableb1_1_3
Sword types

r1_1_1The "What"
Questions
r1_1_2The "Why"
Questionss1_1_1
Books andliterature

1.2 How This Hyperscript Works
r1_2_1A Word to the
Style
r1_2_2
How to Use thisHyperscript

If it doesn't look exactly like this I may have changed details it since I wrote this module.
In a regular book the "Matrix of Modules" would be the linear "Table of Contents". We need to be more involved here,
because the Hyperscript contains not only a linear flow of text like book, but much more.
The general ordering principle is clear from the picture above:
Horizontally you have rows for chapters and subchapters. Vertically you find 6 columns. The have headlines orlabels called:
Basics. These modules contain basic and potentially boring background information. They supply somedetails you may want to refer to on occasion.
Backbone. This contains the text etc. that would constitute a normal book.
Science. In this column you find modules that enlarge in a more scientific way upon what is treated in the
backbone. There will be equations! Nevertheless, the science modules can still be understood by anybody
with a math background going just somewhat beyond being able to count to 100.
Illustrations . Here you find more pictures, text or other stuff that illuminates some particular point in the
backbone in more detail.
Word and pdf. Here you find links to some "Word" or "pdf" files, usually from other authors, that relate to
the topic at hand. All those documents are from the Net but stored in the files of this Hyperscript to makesure that you will have a working link.
Miscellaneous. You guessed it. In this column all kind of stuff is collected that goes beyond what is treatedin the backbone. That doesn't mean that it is incomprehensible. Sometimes the content of these modules
may appear to be a bit removed from the topic presented in the backbone part (try this link for a taste treat).
Sometimes these modules are very long and sometimes they are short. Sometimes they may enrage you
and sometimes they may bore you. So be it.
Hidden Modules They are hidden. But you can find them if you don't drink too much beer while readingalong.
Browse a bit in the the matrix of modules and you will understand.
All modules outside of the "backbone" have links at the bottom that lead you to modules with links to the module inquestion.
The Matrix of Modules has some formatting peculiarities of its own that are explained right there.

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Using the Hyperscript
Do I have to tell you? Just try it out. You have many options:
1. Start at the beginning and keep reading. Don't look left or right (in other words: don't click on anything) and it's
like reading a regular book.
2. Look at the index and jump to any entry you find interesting. Use the links in the module containing this entry
and keep going. You will do a kind of random walk between the modules of the Hyperscript. This is the exact
opposite of reading a book—and possibly fun.
3. Do whatever you like. I neither know nor care.

Iron, Steel and Swords script - Page 10

2. Swords, Iron and Steel
2.1 Swords
2.1.1 What, Beyond the Obvious, are Swords?
2.1.2 What Swords Are for Me

2.2 Let's make a Sword
2.2.1 Bang it!

2.3 Some Definitions
2.3.1 Let's get to Work.
2.3.2 What Makes Steel so Special?

Iron, Steel and Swords script - Page 11

2. Swords, Iron and Steel
2.1 Swords

2.1.1 What, Beyond the Obvious, are Swords?
What, exactly, are swords? Stupid question - don't we all know? Well, we shall see about that.
Just to give you a taste treat of what follows, I make this claim:

Some swords are pieces of art
and part of your cultural heritage.

Read on if you do believe me, and in particular if you don't believe me.
Some swords are pieces of art, not all. You will find examples of the former on display in major museums. Whilemost of those museum pieces were also perfect weapons for combat, changes are that they have never been used
for killing or wounding people.
Be that as it may, it is also absolutely necessary to point out that most swords were not primarily pieces of art but justtools for killing or wounding "the enemy". Most of those "utility" swords have rusted away by now or get dusty in attics
and minor museums (including army museums).
If you think a bit about that you realize that killing or wounding people is pretty much the only direct use of asword.
You could kill or wound people with your knife too, not to mention your car. But in contrast to your knife, you can't
use your sword to butter your bread, to cut your steak, to clean your fingernails or to cut a hiking staff from the next
hazelnut bush.
I want to be very clear about the following:

Swords are evil objects if you consider only
their intended or actual use as weapons.

Of course, you might argue that you are a peace-loving, anti-violence kind of person, and that you only carry your sword
so you can defend yourself against being attacked. Many Americans use exactly this argument for carrying guns.
This seems to make some sense. The reality is that 3 people out of 100.000 get killed by guns every year in theUSA, while in Germany (guns are strictly illegal) the number is around 0.5, one-sixth of what we have in the USA 1).
I fully sympathize with all of you who look a bit askance at weaponry of all kind. Yet, if you stay with me for a while
longer, you will find that there is far more to swords than pain and death, and that studying their history and technology
can be rewarding.
Whatever swords are, one fact is undisputable. Men of all ages are far more fascinated by swords of all kinds than
women. Some castle museums have a sword or two around that the men are allowed to handle. The hope is that thiswill induce them to keep their hands off the exhibition pieces.

Iron, Steel and Swords script - Page 12

Doing the sword bit at Coburg castle, Germany
The sword, by the way, is "Prince Valiants original
singing sword", as the guy explained to his fascinatedaudience.
Women, generally speaking, are not much interested in swords. There must be areason for this. Siemund Freud, if still alive, would mumble something about "swords
are phallus symbols " or "swords symbolize power by penetration". Maybe he is nottotally wrong for once. Keeping this in mind I've speculated a bit about the real
meaning of sword names. The result can be seen as amusing, outrageous, or justplain stupid; take your choice.
A lot more to the topic "swords as symbols" can be found in the special module.

Misc.
ModuleSwords as
symbols

So let's face it: Swords always were more than just weapons for fighting. Look at cars nowadays. For most men andsome women cars are certainly more than pieces of hardware designed to get you from A to B. On a similar note, formost women but very few men, shoes seem to be more than just cases for protecting your feet if you want to to walkfrom A to B.
I certainly can't tell you what is so fascinating about shoes besides using them for walking around. Your wife or girlfriend might be able to tell you about that.
However, I do have have some ideas about what swords were good for besides fighting, and I will share these ideas
with you. For starters I state a simple truth:

Swords were and are powerful symbols for something else
Here is my quick list of what swords symbolize. The link gives more information about swords as symbols.

1. Swords were and are powerful symbols of a state, often found on flags or crests.
Every queen (not to mention king) has at least one sword of state at her disposal, just like a scepter, a crown, acastle, and a Rolls Royce (or the equivalent thereof). Queen Elizabeth II even has three swords of state. One
embodies the (former) life-and-death power of the queen, another one, named "Curtana", demonstrates mercy.

Swords as symbols of state
Flag of Saudi Arabia"Curtana", sword of state of
the Queen of England.

Curtana is actually broken. This symbolizes that royal justice ought to be tempered by mercy. Curtana also comeswith some mythology: it is supposed to be Tristan's sword (it isn't). Tristan was one of the more notorious knightsfrom King Arthur's round table, a supreme fighter, full of testosterone. He lived (if he lived at all) around the sixth
century AD.
In King Arthur's case the "sword in the stone" (sometimes equated with his"Excalibur") was a direct and powerful symbol for the rightful king. It actually madehim King. The possession of a special swords thus announces power or a powerful
Iron, Steel and Swords script - Page 13

In King Arthur's case the "sword in the stone" (sometimes equated with his"Excalibur") was a direct and powerful symbol for the rightful king. It actually madehim King. The possession of a special swords thus announces power or a powerful
blood line.
More to King Arthur and other real and saga heroes in the special module.
The Queen, by the way, uses one of her three swords as a tool in the only known
civilian way: she will touch my shoulders with it when she knights me.

Misc.
ModuleSagas andHeroes

2. A sword advertised rank or class. Not everybody was allowed to carry a sword, and the kind of sword you carriedoften announced your rank.
This is true for many ancient (and not so ancient) societies. The cavalry man in the roman army had a long sword (a"spatha"), while the common legionary had a short sword (the "gladius") as standard issue. While that may have
had practical reason in the beginning, it eventually evolved into a status thing.
Even outside the army proper a sword signified your class. If you weren't allowed to carry a sword in merry old
England and pretty much everywhere else, you couldn't challenge a Gentleman for a duel, nor could you bechallenged. The gentlemen then just thrashed or killed guys like you and me unceremoniously.

Comparison of Gladius and Spatha
Note that the two pictures do not have exactly thesame scale; this is only a qualitative comparison.
Source: Internet at large

3. A sword was good for showing off.
As an officer you could carry a standard-issue sword or an expensive showy damascene sword - if you could afford
it. Manfred Sachse's wonderful book " Damascus Steel" gives many examples for this. Most of the elaborately
decorated swords in museums were only used for showing off or for demonstrating rank.
That is quite fortunate. The world of art (including architecture, and so on) would be indescribably poorer today ifmost people in power or money did not like to show off.
Of course, all three points might appear mixed up somehow, for example here:

Ceremonial swords of Copenhagen town judges
around 1500 or so.
My wife gives an idea about the size of those things.
Iron, Steel and Swords script - Page 14

The Copenhagen judges left no doubt about who had the biggest. We have a symbol for the power of the city, an
advertisement for rank and power, and certainly a bit of showing off.

4. Old swords might be national treasures, closely guarded and displayed in museums.
This is quite prominent in Japan but the French also treasure the sword of Charlemagne (named "Joyeuse"), andSpaniards value El Cid's sword "Tizona".
More to swords with names in the special module.
El Cid Campeador (1043-1099) lived in what is now Spain. He defeated the "Moors", islamic rulers, who governed
the southern part of the Iberian peninsula (when he wasn't fighting for them). His famed sword Tizona survived
through various Spanish noble houses When the impoverished present owner tried to sell it in 2003 (asking 6 MioEuro), the Spanish government interfered. The city of Burgos eventually acquired it (at a bargain prize of 1.6 MioEuro) and Tizona is now on display in the museum in Burgos, close to the birth place of El Cid.
It is also a safe bet that the Turkish government would not be easily persuaded to part with Mohammad's sword
either. It is displayed in the Topkapi museum in Istanbul (it's authenticiy, however, is a bit open to doubt).
The Copenhagen swords in the picture above, like most swords in museums, are not national treasures, however,
but just curios or tokens of history.

5. Swords, next to rings, were often assigned magical properties in many legends, myths, and fairy tales. Looking
closely, one can detect two varieties of the magic involved: Old-fashioned black magic because the sword was made bysome (now defunct) God, cobold, dwarf, giant and so on, or wholesome Christian magic based on miracles due tohaving, for example, a small piece of a Saint enclosed in the hilt. And we have mixtures of the two, of course.
Everybody knows about the magic "sword in the stone" from the King Arthur saga,
and about his "Excalibur" (the two, incidentally, were not the same).
North European mythology knows "Balmung", Siegfried's magical sword that heforged from the parts of "Notung", the, needless to say, magical sword that broke in afight with Wotan , the top God of Valhalla. This link recounts the story of Richard
Wagner's "Ring des Nibelungen" in a slightly unorthodox way.
Eventually, the despicable heathen magic imbued in swords like Excalibur or Notung
gave way to admirable Christian miracle swords like Charlemagne's Joyeuse. Many
warriors had some piece of a relic inside the hilt of their swords as late as the 14 th
century.

Illustration
ModuleSwords withnames

We find a tale similar to Wagner's "Ring" in the modern "Lord of the Ring" saga, where "Anduril", the sword of the
returned King Aragorn, was forged by the elves from the remains of "Narsil", the magical sword that broke in a fightwith evil Sauron .
Just to be complete, let's enumerate a few more famous named swords.
We have "Mimung ", the sword that enabled "Wieland the smith", another northern hero of old, to win a contest
between smiths. He cut his opponent so neatly in half that said opponent failed to notice this until he made his next
move and fell apart. Here is the full tale (in German).
El Cid had another famous sword, the "Colada", and Theodoric the Great owned "Eckesachs" and "Nagelring".
Roland, Charlemagne's nephew and paladin (sort of closest ally or personal body guard; I had to look it up, too)
who comes with his own saga, fought with "Durendal". Shamshir e Zomorrodnegar "("the emerald-studded
sword") was the sword of King Solomon.
Most prominent is also "Zulfiqar", the sword that the Prophet Muhammad gave to his son-in-law Ali. A long list ofnamed swords can be found in the link. Note that all "magical" swords were "lost" in antiquity; famous surviving
swords have no particular magical powers.

6. Swords made great (and expensive) gifts from king to king or king to vassal.
We have an old letter originating from Theoderic the Great, expressing his gratitude for a gift of marvellous swords.
The most likely pattern-welded blades achieved far more gratitude than a number of "foreign pageboys of noble birthand fair complexion".
The famous Japanese nihonotos (swords) , especially the "Dai - Sho" (long - short), the matched pair of a longkatana and a short wakizashi always associated with Samurai, was essentially a gift from the Samurai's boss toassure loyalty etc. It could be used for fighting but that was not the main point.
Swords still serve as tokens of appreciation in some parts of the world. In Eastern Europe, after the Berlin wall came
down in 1989 and one could go there, I have seen swords displayed in offices. Those swords were given, forexample, to the "manager of the year" instead of some decadent plaque or goblet. Right now (2018) you can bit at
an auction for a magnificent sword that the Saudi-Arabian princess Hessa al Saud gave to her German doctor as atoken of her appreciation some time in the second half of the 20th century.
In Arabic countries, a sword may still be the trophy for the winner of a camel race.
Here is an example from 1833:

Iron, Steel and Swords script - Page 15

Trophy sword from 1833
The inscription expresses gratitude to the winner ofsome tournament
Source: Photgraphed in Bamberg,
Germany,

Large size

I stop here but there is far more. I have written several long special modules to the points made above (check the matrix
of modules) so you can believe that I do find these topics rather interesting. Nevertheless, the major point about whatswords mean to me still needs to be made—in the next paragraph.

1)

According to "Die Zeit" (a leading German newspaper) from Nov. 2012, almost 15.000 people get shot per year in
the USA (about 300 million citizens). In Germany (about 80 million citizens) it's about 700.

Iron, Steel and Swords script - Page 16

2.1.2 What Swords Are for Me
Swords are Paradigms for Metallurgy
While all the points about swords considered previously make sense and provide for some entertainment (I promised!),the major point I want to make is still missing. Here it is:Swords were always at the
cutting edge ofiron and steel technology
The pun is intended. The cutting edge of a sword did embody the status of the metal technology in a given culture.
How sharp was it? Did it stay sharp? Could it cut through the sword and the armor of the enemy without sufferingmuch damage?
Studying old sword blades, together with the technology for making them, allows us to get a good glimpse at thedevelopment of our most important technology now and then. Let's read out loud:The making of iron and steel products
was and is our most important technology!
I promised to give you a good reason to read on, and that's it. No matter what uses a sword has seen when its ownerstill lived, by now it reflects the technology and artistry of his days.
Why, you might ask, don't I use more civilian iron things like ancient knives, pots,
pitchforks, scythes, nails, or chastity belts to reflect about iron technology?
Well, not only are pitchforks rarely works of art, there aren't too many old ones around.
Pitch forks were not passed on as treasured heirloom or put into the grave with its
owner. More important: they simply do not reflect the cutting edge of steel technology.
When your pitchfork, knife or chastity belt broke while baling hay, spreading butter,cleaning your nails, or trying to do you-know-what, your chances of surviving thatmishap were pretty good. If your sword broke while fighting the infidels (of either
denomination), you had a serious problem, if only for the short time of your remaining
life span.

Illustration
ModuleOld ironthings

A scythe bears some similarities to a sword and in this illustration module you find a particular interesting picture tothat. However, as far as properties were concerned, a scythe wielder needed to have his tool repaired orreconditioned far more frequently than a sword wielder.
Anyway, having the best possible steel hardware intended for battle was important. The following picture from the12th century shows this quite drastically. Note that good steel seems to cut easily through helmets and chain mail.
Maybe it's true, maybe not. The winners write the history books (and illustrate them), and one shouldn't believe all
one reads and sees in these volumes.

Fighting the Infidels (of either denomination)
Large size picture
Source: "Morgan Bible" (Pierpont Morgan Library, New York); amedieval picture bible.

Iron, Steel and Swords script - Page 17

In battles like this you were much better off with a good sword and other steel hardware. If you had to participate in abattle, you certainly made sure that your sword was the best you could possibly afford. I do believe that I'm justified inclaiming that the best old swords represent the top iron and steel technology of their time. They do that for all culturesand for a time span from about 1.200 BC to 1.800 AD or roughly 3.000 years.
Unfortunately, we do not have a lot of old swords or other iron artifacts in our possession since iron and steel rusts,
as everybody knows who ever owned a .... (insert the car maker of your choice). Many old swords therefore are justlongish rusty objects that do not look particular impressive or artistic. Other old iron has simply been recycled since
it was valuable. Add to this the unfortunate fact that ancient smiths didn't write up what they were doing. They
couldn't write anyway, and what they did was probably semi-secret if not top-secret. The people who could write,and had the leisure to do so, didn't know how it was done. If they wrote anything about a science / technology topic,
chances are very high that it was simply wrong. Take Aristotle, for example, who got science issues always
wrong without a single exception, as far as I can tell.
Many details of the ancient art of iron and steel making are therefore lost or shrouded in mystery. Mystery is always
interesting, and new myths about "lost" technologies are a dime a dozen. For unfathomable reasons many modern
people are convinced that some ancients knew more about iron and steel, medicine, pyramid building, etc. thanmodern nerds like me.
There are certainly many aspects of the ancient iron and steel technology that we don't know about. New
discoveries yet to be made might unearth exciting new steel artifacts and force us to change parts of the presently
held believes about ancient technologies. One thing, however, we do know for sure:

All iron and steel technology,
for all cultures and all ages,
follows basic principles ofMaterials Science and Technology
Swords are Works of Art
Do you agree? Are swords works of art or instruments of the devil? You may not perceive swords as works of art rightnow but I hope you change your mind after having read this Hyperscript.
Appreciation of art always requires some knowledge about the artwork you are contemplating. How was it made,how was it embedded in the culture of its time and place? How does it connect to artwork of other periods andplaces? And so on.
Some art cannot be fully appreciated outside of its cultural context. Take Japanese haikus, for example, or religious
topics in medieval paintings. Moreover, appreciation of art is always done within some personal frame of reference
that is based on your specific culture. A Turkish Muslim will perceive Leonardo's last supper quite differently froman Italian Christian or a Japanese Agnostic. Not to mention Attila the Hun.
Swords can be works of art just like haikus or paintings. They are expressions of particular cultures and ages and,considering that they always must be longish steel objects, amazingly varied in appearance. All of them have acommon denominator, however: the art of making their steel blades. I use the word "art" here quite intentionallybecause for me some of the old smiths were not just artisans but true artists. You will at least understand if notshare my point of view after you have appreciated what it takes to forge a supreme sword blade.
Now you might think: "OK. So some swords might be works of art - but if you have seen one, you have seen them all".
Nothing could be farther from the truth. If you have seen one of Monet's lily ponds you haven't seen them all, even sothey all appear to look alike. Swords do look alike too, but are nevertheless quite different. Not only is the production ofa "true damascence" wootz shamshir totally different from that of a Japanese katana or a pattern welded sword, thefinished products are quite different too, if you know what to look for.
If you don't know the English language, all Shakespeare sonnets are the same to you. If you have seen one, you haveindeed seen them all—but comprehended nothing whatsoever. If you go through the pain and labor to learn the English
language, you cannot only comprehend Shakespear's sonnets now—a whole rich new world opens up to you!
I'm going to teach you the language of iron, steel and swords. That will enable you to really appreciate the art of swords
and it will open the door to a whole rich new world!

Iron, Steel and Swords script - Page 18

Works of art
Reproduction of patternwelded (Viking) blade by
Patrick Bárta

Oriental Wootz blade (endof 18th century / beginingof 19th century)

Source: Patrick Bárta's
homepage; with permission

Source Weapons of warriors

Iron, Steel and Swords script - Page 19

2.2 Let's make a Sword

2.2.1 Bang it!
You're the smith in ancient times (from 500 BC to, let's say, 1800 AD) and you have a lump of iron or steel. Maybe it
fell down from the sky like in ancient Egypt, where iron was known as "ba-en-pet" or "metal of heaven". It is generally
believed that before about 1300 BC, extremely rare meteor iron was the only iron the ancient Egyptians knew. Vagn
Fabricius Buchwald doubts that and I tend to believe him as you will see later. If your iron did not fall down from thesky, maybe you or some specialist of your town, made it from iron ore, charcoal, secret magic ingredients, plus prayers
or spells. Maybe you imported steel from what is now India, because the ancient Indians could make some particularly
good stuff called ""wootz" steel, or maybe you still have the pieces of your father's magical sword that broke when hefought someone or something while having unclean thoughts; whatever.
Now make a sword from your iron or steel.
How do you do it? Most contemporary people have never pondered that question. If pressed, they tend to weasel
and guess that's it's done by casting, rolling, or by pressing it into a form. You might have seen that in a car factory,
where the car body is made from sheet metal that way.
All of that is wrong. Completely, utterly wrong.
Let's start with something easier. You have your piece of iron and you want to make a pitchfork or the pieces of achastity belt because your spouse needs one. What you do is: heat up your piece of iron until it has a certain red
color. Then, while it is still hot, you bang it into the wanted shape with your trusty hammer. Repeat heating andbanging until you have the final shape. Then you are done.
Now you want to make a decent sword. You're going to heat and bang your material too but that is only a small partof the total process now.
You, the smith, will spend far more time on making a sword than on making pitchforks, pots and pans.
Nevertheless, no matter how involved your forging technology might be, one essential fact remains:

Everything, I repeat: EVERYTHING thatwas made from iron or steel up to andbeyond about 1800 AD, some smith hadbanged into its final shape with a hammer.

All the iron or steel swords, knifes, axes, suits of armor, chastity belts, chain links, locks and keys, needles and so on
were made this way. No exceptions .
Next time you see a complete suit of armor in some museum, you will look at it with a new kind of perception.
Imagine making it with nothing but a hammer, an anvil, a fireplace (a smith's hearth, actually, coming with bellows
and charcoal) and some simple tools like tongs and files.
Could you do it? Neither could I!
Nowadays you need to go through "a long and grueling training phase of almost 3 months" if you want to become a
top model—I'm quoting from a TV show. The producers of that show left no doubt that this kind of ordeal entitles you
to a sizeable income. If you want to make real money, however, you might need a year or even two of involved
training, including squandering other people's money by the billions, as investment banker.
In contrast, a humble smith, able to produce one of the swords we discuss here, had to learn and practice for many
years. Thousand and some years ago and today!
At a Viking show in Schleswig, Germany (home of major Viking artifacts, including swords, in its large museum), I
watched a young smith forging a simple sword. "Could you make a replicate of one of those fancy pattern-welded
damascene swords I see in the museum?" I asked him. He laughed and replied: "I've been at this for three years.
Come again in about 5 to 6 years; then I might be up to a fancy kind of damascene sword". As an afterthought headded: "And don't forget to bring along several thousand Euros in cash if you want to buy one".
You might tell me: "this is vaguely interesting—but is it true? After all, I have seen superior steel swords made bycasting molten steel into a mould when I watched "Conan the Barbarian" in the movie theatre, not to mention good old"Siegfried" of Wagner fame in the opera. And what about those old Chinese guys who were famous for their huge castiron cauldrons 2.000 years ago? In the Bronze Age, everything was cast; I have seen the moulds for swords in themuseums. I also know that during the last war that you Germans won (1870, against the French), huge cast steel
cannon from Krupp , a company name almost synonymous with "Gussstahl" (cast steel), was used. So how about
that?"
Iron, Steel and Swords script - Page 20

What you tell me is absolutely correct. But you still got it wrong. Let me tell you:

Conan, as well as Richard Wagner's
Siegfried, and plenty of others,
simply got it wrong.

Conan (alias Arnold Schwarzenegger ), not knowing how swords were really made, had to become a politician.
Being clueless is acceptable if not actually required for that job. Siegfried is dead (spear in the back; forged point,
not cast).
"Cast-iron", the name for a material quite different from iron or steel, can be cast, indeed. But cast-iron is neither
iron nor steel but some brittle stuff. Cast-iron sword bearers, if there were any, did not enjoy a long life.
Bronze, an alloy of about 90 parts Copper (Cu) and 10 parts tin (Sn) was cast with ease indeed, but iron and steel
were never cast before the middle of the 19th century.
The reason for that is simple: the old smiths' couldn't get it up.
They could not get up the temperature of their fires to the 1536 oC (2732 oF) required to melt iron. For comparison,copper (Cu) and gold (Au) melts at 1084 oC (1983 oF) and 1064 oC (1947 oF), respectively; and bronze comes in at
a low 800 °C -1000 °C (1472 oF - 1832 oF), depending on composition.
Make a nice fire and blow into it a bit (through hollow reeds like the old Egyptians), and you might get up to 1100 oC(2012 oF). But blow as hard as you can and you will not even get close to 1536 oC (2732 oF).

Melting gold in ancient Egypt
Source: Photographed in-situ

The picture shows a relief in the Mastaba of Mereruka in Sakkara, Egypt. It goes back to the 6th dynasty and isabout 4.400 years old. It shows probably gold smiths (or more likely their apprentices / employees / slaves) blowing
into a kind of hearth intending to melt (a little bit) of gold. It take six guys for that particular blow job just to get alittle bit of gold up to 1064 oC (1947 oF)! There is no way whatsoever to melt a lump of iron or steel large enough formaking a sword in this way.
By the way, I will debase myself to the point where I give temperatures in degrees Celsius and in degrees Fahrenheit
instead of Kelvin to help you non-scientific and possibly non-metric folks out there. All you need to know abouttemperature and how to measure it is found in this module.
I will also spell out the full names of elements and compounds and give their chemical symbols to help thechemically challenged out there.
Out of the goodness of my heart I even give you a complete periodic table, from which many secondary links will
give you plenty of data about all chemical elements.
I will, however, not give inches, pounds and other nonsense next to centimeters and kilograms . I will also not
insult your intelligence by referring to nanometers (nm) and so on as "one hundredth of a millionth of a centimeter","a fiftieth of a thousands part of the diameter of a hair" or other crap like that.
I will give you this basic module for the essentials of the metric system and for figuring out yourself how to convert
length scales if you must.
Now back to the ancients not getting the temperature up. Think about it: What would you do to get very hightemperatures?
You won't be successful with an open fire. You need involved constructions around your fire and you need to blow
plenty of air (or even better: oxygen) into it. In other words: you need a blast furnace.
Iron, Steel and Swords script - Page 21

I bet you couldn't build a blast furnace. Neither can I. But all of us can make very high temperatures with the switchof a finger: by turning on a light bulb, for example. We use electricity, in other words.
The temperature of the tungsten (W) wire in your light bulb is around 3000 °C (5400 °F) and you get that by justthrowing a switch.
Unfortunately you, the ancient smith or iron smelter, did not have electricity at your disposal. At best you had abunch of slaves (or wives) for working the bellows. A good water wheel working your bellows is much better, and asteam engine is better still.
Electricity beats all that. But steam engines and electricity haven't been around all that long; the other options are
not all that effective. It is no accident that there was no mass production of steel before the advent of powerful steam
engines in the middle of the 19th century.
In the words of Franz Sales Meyer, who around 1888 wrote the "Handbuch der Schmiedekunst" (handbook of thesmiths' art) that my grandfather (a smith) used:"Wrought iron can't be melted".

Iron, Steel and Swords script - Page 22

2.3 Some Definitions

2.3.1 Let's get to Work.
Enough small talk, we need to do some work now. We have used everyday words like iron, cast-iron, wrought iron,steel, and so on, and we now need a few definitions in order to avoid confusion and to be sure that we really know what
we are talking about.
Iron
Iron is simply a chemical element; its symbol is Fe (from Latin "ferrum" = iron).
Pure iron, and that means iron containing only very small amounts of impurities, melts at 1536 oC (2732 0F). We
already know that this is a rather high temperature, not easily reached with "natural" means.
What we don't know yet are the answers to some of the more general "why" questions. Why do things melt? And why
at quite different temperatures?
We need to look into that a bit and for that we need to discuss first what "temperature" actually means. You may
now feel a bit amused; thinking that you sure know what temperature means. Well, we'll see if you do.
Wrought Iron
Pure iron (Fe), in a chemist's sense, is a rather recent thing. For a very long time the best approach to half-way pureiron is what we still call "wrought iron".
"Wrought" is just old-fashioned English for "worked", and the term "wrought iron" simply refers to the way it was
made: the smith banged together the little lumps of relatively pure iron found in the "bloom " of ancient smelting
furnaces after the smelting process. In German, by the way, wrought iron is called "Schmiedeeisen" ("forged iron")because it was forged together.
Talking about impurities in iron, we first talk about carbon, another chemical element. Wrought iron does not containmore than about 0,1% of carbon. There is no clear-cut definition, however, and a lot of times when people (orarchaeologists) use the expression "wrought iron" they might refer to what is known as mild steel with up to 0.4 %carbon.
By the way, concentrations given in percent (%), if not otherwise stated, always refer to "weight percent". A
concentration of 0.5 % carbon in iron, for example, means that you have 5 grams (g) of carbon in 1 kilogram (kg =1000 g) of the stuff; leaving 995 g for the iron. This leads us to the next item:
CarbonCarbon (from Latin "carbo", meaning charcoal), is simply another chemical element (symbol C).
In its purest and most stable form carbon is found as graphite but there are many other modifications or phases ofpure carbon like
1.
2.
3.
4.

Diamonds; very exciting for females.
Carbon nanotubes (CNT); very exciting for materials scientists.
"Bucky balls" made from Carbon.
"Graphene", a sheet of just one atomic layer of carbon atoms; extremely exciting for physicists andmaterials scientists.
5. "Amorphous" diamond, very annoying for people trying to clean their ovens (it's part of that hard black stuff).
Coal, by the way, is not even coming close to being pure carbon; it's full of all kinds of impurities. Only after it has
been thoroughly cleaned could we call it carbon but for historical reasons we then call it coke. You can test yourskills in working with this Hyperscript by finding the special modules dealing with much of the above; I did not makethe links on purpose.
Carbon is a great element not only for carbon-based life forms like slime mold, mosquitoes or you and me, but also
for illustrating a supremely important concept:

Iron, Steel and Swords script - Page 23

One and the same element(or compound)might exist in modifications as different
as diamond and graphite.

We need a good name for that phenomena. From now on we will call those different modifications, structures,
manifestations, different states of being, or whatever you like to call different forms of the same stuff by one word:
different phases of the same material.
This is something very important that you need to remember. So let me repeat:

One and the same material might exist in different phases.

Phases
The concept of "phases" is supremely important for making iron, steel, and swords (and about anything else). So, what
exactly is a phase ? We will get into that in great detail later, for now we just ascertain the following examples:
Graphite is a distinct phase of pure solid carbon; diamond is another phase of pure solid carbon.
Ice is a distinct solid phase of aitch-two-o (H2O). Liquid water and steam are other phases of the substance or
chemical compound H2O, consisting of one oxygen (O) atom and two hydrogen (H) atoms. Whatever phase you
look at—it's still aitch-two-o. I must call it aitch-two-o or H2O in chemical shorthand because—surprise!— there isno common name for this substance. There are only names for some of its phases.
If one and the same material exists in different phases, logic dictates that we must be able to induce phase changes .
That will be a decisive thing for sword making.
So let's look at phase changes in iron right away. Iron (Fe) crystallized in one way and then called "ferrite" is adifferent phase from iron crystallized in a different way called austenite. In contrast, iron carbide (called "cementite"(Fe 3C)) and rust (a mixture of iron oxides and hydroxides) are not different phases of iron. They are different
chemical compounds and thus different materials
Phase Changes
Phase changes actually are rather common. When the ice in your whisky melts, the material H2O undergoes a phasechange from a solid phase called ice into the liquid phase called water. We also call that a phase transformation or aphase transition.
When iron melts, or if anything else melts, there is also a phase transformation from solid to liquid, for that matter.
Phase changes from solid to liquid are a bit trivial, you might think, so let's look at phase changes from one solid
phase to another one.
The phase change from carbon in its diamond phase to carbon in its graphite phase, for example, is easy to do:heat up a diamond without admitting air (otherwise it just burns) and you get graphite. It is easy to do because
carbon prefers to be in the graphite phase at room temperature, and the diamond phase just needs a little incentive
to change to graphite. You can try an experiment in your kitchen when your wife is not around. Women tend to
oppose experiments that turn their diamonds into coal. That's probably while few experiments along that line havebeen performed. Reversing the process, making diamonds from graphite, is not quite that easy, by the way.
Different phases of the same material may have very different properties. Tell your betrothed-to-be that the lump ofgraphite in that engagement ring you gave her is practically the same as a diamond, and she will tell you far more
about the relative merits of different phases of the same element than you ever wanted to know.
Pure solid iron (Fe), as it happens, comes in different phases, too, just like carbon. Phase changes occur whenever you
heat it up beyond a certain temperature and when it cools down again.
Some of the different phases of pure iron have names like some of the different phases of H2O or carbon. The pureiron phase prevalent at room temperature is called "ferrite". If we heat the ferrite phase to 912 oC (1674 oF) it
changes to a phase called "austenite". Ferrite and austenite are just as different as diamond and graphite.
Some really big "why" questions come up now. The answers will come up later:

Iron, Steel and Swords script - Page 24

Why would something consistingof a bunch of identical atoms manifest
itself in different phases?
Why can different phases sometimes coexist ?
Why do phase changes happen
at some specific temperature?

Steel and Cast-Iron
If we add a bit of carbon to (otherwise pure) iron, we obtain a range of materials that we call:(Carbon) steel if the carbon concentration is around 0.3 % to 2 %.
Cast-iron if we have carbon concentrations in the range of 2 % to 4 %.
Note that "cast-iron" is a name for an iron-carbon alloy. That's why I'm going to write it with a hyphen. Cast-iron is not
pure iron that has been cast into some mold; it is an iron alloy that got its name because it is easy to cast, in contrast
to pure iron or steel.
There are a lot of iron alloys (mixtures of iron and other elements) around since there are a lot of other elements you
can mix iron with. Some of those alloys we call steel and some others we call cast-iron. These names are thus justgeneric or collective names for a whole bunch of quite different iron alloys with different compositions.
The only common denominator is that all steel and all cast-iron varieties contain iron.
There are qualifiers for special steels and a plethora (= a hell of a lot) of names for it.
Steel names might be historical ("Wootz" steel, Sheffield steel, Tamahagane), scientific (hypoeutectoid vs.
hypereutectoid steel), relating to people (Bainite, Martensite, Ledeburite) or describing appearances, processes orproperties (pearlite, maraging steel, spring steel, mild steel, stainless steel, TRIP steel).
I'm just showing off here. We need to go into some of that later, however.
What we note right here is the essential "why" question concerning (carbon) steel

Why does a little bit of carbon inside ironchange its properties so dramatically?

A carbon concentration somewhere between 0 % and 4 % determines if we have:
Relatively soft pure iron with a high melting point of 1538 oC (2800 oF).
Hard but tough or ductile steel with a still rather high melting point around 1500 oC (2730 oF).
Very hard and rather brittle steel.
Completely brittle cast-iron with a low melting point around 1150 oC (2102 oF).
Why? And how does the carbon work this miracle?
Melting Point of Alloys
What we should note right here is a simple truth: The melting point of (almost) all alloys, e.g. the alloy of iron and 4 %carbon that we count among "cast-iron", is always substantially lower than the melting point of the major pure element.
The same is true if we don't have a technical "alloy", implying that we mixed the constituents for the alloy
intentionally, but just "dirty" or impure iron, implying that whatever is in there is not of our doing, and likely notwhat we want.
This makes clear why copper (Cu) alloys like bronze and brass were easier to deal with than the pure metals at theadvent of metal technology.
Now why does the melting point go down if you add a bit of this or that? That's a really tough question that we
nonetheless need to answer.

Iron, Steel and Swords script - Page 25

2.3.2 What Makes Steel so Special?
Before we tackle all those "why" questions, we must look a bit deeper into the "what" questions. What properties,
exactly, make steel so special?
Let's first look at a world without iron and steel, to see what's it all about.
The Iron Age started about 3.000 years ago and lasts until this very day. Before
that we had the Bronze Age that succeeded the Copper age, and way back we
had the Stone Age. Before that we had Ages with names like "Jurassic Age", but"we" weren't there.
It's of course a bit silly to keep track of time that way, and one should note that theBronze Age overlapped with the Iron Age for 1000 years or so. We still have bronze
for many applications, come to think of it.
Are we entering the Silicon (Si) age now? I doubt it, despite the fact that I earn
my living by advancing silicon technology and not by writing popular science books.

Misc.
Link
The "Ages"

We certainly have plenty of fun (and aggravations) with semiconductor products like personal computers, radio,
TV, cell phones, video and the Internet, not to mention solar cells and instant financial crashes. My children do notbelieve that human life without Internet and cell phones is actually possible but I know it is. I was there.
Nevertheless, you didn't need silicon or other semiconductors to run big ships, airplanes, cars, railroads and, quite
important, elevators. You didn't need semiconductors either to conquer half the world as the Germans tried and theBritish did.

You needed steel products.

If you are not convinced, ask yourself two questions:
1. What would you rather miss? Your car or your cell phone?
2. What would be that one object you would take to that desolate island, if you are given a choice?
In our age, whatever its name will be in hindsight, we not only have steel and silicon, we also have aluminum, titanium,
and many other metals and alloys; Teflon and many other polymers; carbon fiber composites (CFC) and glass fiber
composites (GFC); and above all, we have electricity .
We have a plethora of high-tech materials enabling wonderful things like artificial knee and hip joints (wait until you
need one to appreciate this), lightweight bicycles and airplanes, Lasers and the possibility to send e-mails all overthe globe in bulk, but we still would make a sword from steel . Or, if you like that better: a knife, a pair of scissors,
sewing needles, an axe, saw blades, car bodies, ships, high risers and their elevator cables, machines of all kinds,and so on, are still made from steel.
If you think about it, not all that much that was made from steel some time ago, is now made from something else.
Steel is just a great material!
It's the properties that count, of course. Whenever we look at a product, we must ask ourselves: what kind of
material properties do I need for my sword, my rails, my turbine blades, my sewing machine needle, my gear
wheels in the sewing machine, my hip transplant, my wheel chair?
Note that in Materials Science and Engineering, properties of materials include banal things like: availability of thematerial, ease of recycling after use, aging / longevity, and, of course, the costs.
As far as your sword is concerned, the first important property is:

It must not break!
If it does, you give your opponent a break he is certain to use.
Making an unbreakable sword is easy, of course. You could even make the blade from brittle cast iron and it won't
break—as long as you make it rather thick.
It also won't break because now you can't swing it anymore - it is too heavy. This is trivial but makes clear that weneed to consider specific properties that are tied to weight or size.
Making an unbreakable lightweight sword is also easy too: just make it from some tough wood like ash or yew. It could
be rather light but won't break easily. Needless to say, your customer will still not be satisfied.
You need just the right weight for the right length, and your sword should certainly be harder than wood.
Iron, Steel and Swords script - Page 26

As hard as possible, come to think of it. You want it to cut through armor and bone, at least in principle, and this is notpossible with swords made from soft materials. A glass sword meets these requirements. Quite hard, sharp, and easilyadjusted to the right length and weight.
Aha - it should be hard but definitely not brittle. Glass is lightweight and hard but will break on first impact for sure.
So it should be the opposite of brittle, which is: ???
Is "tough" the right word, maybe? Yes, tough could be the right word, but leather is also quite tough and so is my wife
on some occasions. We need a better word.
The opposite of brittle is "ductile". A material is ductile if it does not break when overloaded by mechanical stress,
like glass, china or concrete, but just deforms somewhat. Ductile materials are also called malleable; you canchange their shape with a mallet or hammer.
That's why the body of your car twists and bends when you hit a tree, or your sword suffers a notch if you hit a hard
object like the blade of another good sword. We don't like this bending or notching, to be sure. If you look at yourcar after you hit a tree, you are inclined to use four letter words.
Now imagine that your car body would have been made from a brittle material like glass, and you will be grateful thatsteel (or any other metal) is ductile. The same goes for your sword. A notch is preferable by far to fracture.
We need to compromise here. You can't have a cake and eat it any more than you can have a perfect undamaged
sword and use it.
Here we have the central problem of sword making. The blade should be hard but not brittle. It must have the right weight
and length.
And the only way to meet these criteria is to use an optimized ductile material. A metal in other words.
The sword smith of old came up with an amazing variety of ways to deal with the "optimized" in the sentence above.
Combining two or more kinds of iron or steel was quite prominent all over the planet. Hard but rather brittle steel was
combined with soft and ductile wrought iron, for example. Let's call such swords "composite swords" for starters.
Pattern welded swords or Japanese swords belong to that category.
Another approach was to start with hard and fairly brittle "wootz steel" but to work it in such a way that the result is
hard but no longer brittle. Wootz blades, sometimes also called "true damascene swords" belong to thatcategory.
Good swords made with incredibly complex technologies thus existed almost 2000 years ago. But after roughly 800
AD, some smiths in the West stopped to make elaborate pattern welded swords and in essence just laminatedharder steel on a softer core. Why? What was wrong with those beautiful patern welded swords?
Whatever their reason was, they still banged their steel into shape with a hammer. Not before around - roughly 1850 mankind was able to cast steel. Casting steel is our major technology today. All knives, scythes, cutting
tools, submarine bodies, and so on (not to mention swords, wherever they are still used) are made from uniform
cast steel.
There is one last important optimization used on top of all the techniques described above: harden only theimportant part, the cutting edge of the blade in a special process called "case hardening".
We have a non-trivial "why" question here: Why did sword blade forging develop from an extremely complex process
to an apparently quite simple one?
Is there anything else we need to consider with regards to important properties of a sword? Of course; the list goes on:
You want a specific shape : straight and double-edged, bent like a sabre, or theother way around like a yagatan.
You want a specific cross section of the blade: elliptical like a Celtic sword,
wedge-shaped like a Japanese katana; with one, two or three fullers or grooves.
Maybe your blade should be hollow?
You may want the blade to be extremely sharp and stay this way.
You would like your sword not to rust like crazy, and it shouldn't turn dull with age.
You sword should be affordable, and a smith should be able to repair some minor
damage it suffered in battle.
Very important: the blade should be flexible or elastic. In other words, it should be
able to bend if forced, but it should snap right back to being perfectly straight if theforce is off.

Basic Link
Sword types

Old sword lore praised swords that could be bend into a semicircle around the body of its bearer without breaking or
staying bent.
We call that an elastic deformation, a deformation that is not permanent but allows the material to regain its
original shape. Springs or rubber bands deform elastically and with ease, your sword, however, should be able todeform elastically but not with ease. So elasticity or stiffness as a property needs more thoughts, too.
We are still not done. So far we only looked at the blade. But you also need a hiltwith a cross guard, a pommel, and so on.
Your complete sword—blade plus hilt—now has a center of gravity that should be
not too far from the hilt. The location of the center of gravity together with its
weight defines its moment of inertia (we come to that). All of that together withthe kind of grip your hilt provides determines how it "handles".
How a sword handles depends on the sword and you, of course. One size doesn't
Iron, Steel and Swords script - Page 27

with a cross guard, a pommel, and so on.
Your complete sword—blade plus hilt—now has a center of gravity that should be
not too far from the hilt. The location of the center of gravity together with its
weight defines its moment of inertia (we come to that). All of that together withthe kind of grip your hilt provides determines how it "handles".
How a sword handles depends on the sword and you, of course. One size doesn't
fit all, for sure. Handling as a property is only important for swords intended for
actual battle—but then it is extremely important. The best steel doesn't do you
much good if you can't swing your sword like it is a part of your arm.

Basic Link
Sword parts

The last point is: Your sword should have all the properties described above but it should also be a work of art. That's
especially true in our enlightened age, where we don't own a sword as a tool for our jobs anymore but only for what it
symbolizes.
But even in times when you actually used your sword, you liked it to have some aesthetic value. I use my car for movingfrom A to B but I also like it to be aesthetically pleasing. You use your wife - ouch that really hurt (my wife was looking
over my shoulder).
Theodoric, the famous Ostrogoth king was raving about the beauty of the swords he obtained as a gift fromThrasamond , King of the Vandals in most of his one-page "Thank You" letter. In comparison, the gift of "pageboys
of noble birth and fair complexion" rated exactly the 7 words quoted here.
Let's have a quick look at ancient bronze swords. They are usually not very long. Too long, and they break or bend
severely - if not, they are too heavy. There isn't much one could do about that 4000 years ago, and there isn't much one
could do about it today either.
You could change the properties of your bronze to some extent with exactly the same basic mechanism that workso well with iron and steel. But there are limits one cannot overcome. We are going to look at bronze swords ingreater detail later
Iron with a little bit of carbon—steel or cast-iron in other words—is a far more complex material than bronze. It canhave extremely good or extremely bad properties, and that makes it difficult to master this material by trial anderror. But for exactly the same reason it also offers many opportunities for coming up with many different kinds ofsteel, one of which might be what you are looking for.
You can't have your cake and eat it and you can't have a material that is easy to understand and use it for all kindsof different things either.
It is clear what we need to do next. We must get a better grip on the key properties described by words like hard ,brittle, ductile, stiff, elastic and so on. In order to do this we must first define these properties in a way that allows us tomeasure them and thus to describe these properties by cold hard numbers. This will be the topic in the next chapter.

Iron, Steel and Swords script - Page 28

3 How to Measure Important Properties
3.1 The Basic Tensile Test
3.1.1 Breaking Things in Style
3.1.2 Stiff or Hard?
3.1.3 Just For You
3.1.4 A Bit More About Tensile Testing

3.2 Fracture Toughness
3.2.1 A Few Basics about Fracture
3.2.2 The Charpy Impact Test
3.2.3 Fracture and Microcracks

3.3 Hardness
3.3.1 What, Exactly, is Measured by Hardness?
3.3.2 Ways to Measure Hardness
3.3.3 Let's Summarize

Iron, Steel and Swords script - Page 29

3 How to Measure Important Properties
3.1 The Basic Tensile Test

3.1.1 Breaking Things in Style
A guy named Procrustes did the first tensile tests if we are to believe Greek mythology.
The basic idea of a tensile or pulling test is to pull at your specimen from both ends, making it longer and longer
until it eventually breaks. The fancy word for this is: to put the specimen under tensile stress.You can do the samething in reverse by pushing, making it shorter. The fancy word is to put your specimen under compressive stress.
Procrustes used both methods on his specimens. Good old Procrustes' experiments don't count, however, because
not only were his experiments unscientific (no numbers taken or graphs recorded), worse, he didn't use steel orother well-defined metal specimens. He used what scientists nowadays elegantly call "soft matter" (or lesselegantly slime bags) in the form of humans.
The first scientists doing it (almost) right were Leonardo da Vinci of universal fame around 1493, and Galileo Galilei
of "and yet it moves" fame around 1630. They didn't do a tensile test exactly, but they did consider how a wooden beam
or board will bend if loaded, how that relates to its cross-sectional shape, and so on. They didn't get it quite right butthat is no wonder. Doing it right is rather complicated. Just look at the science modules where this is covered and you
will get a good idea why those guys could not possibly get it right at their time.
The tensile test is now the paradigm, the model case for mechanical material testing, and we need to look at it in somedetail. The reason is simple. What we learn from just pulling at a straight bar of some material will allow (some of) us tocalculate what will happen when we push and pull in any way whatsoever on any piece of material of any conceivableshape.
Bang on glass, steel, or camembert cheese with a hammer, wrap your car around a tree (be sure to wear your safety
belts when you do that experiment), or perform any experiment where you deform some object. Provided we have thematerial data from a tensile test and the "shape" and composition of your object, some of my colleagues can calculate
what kind of shape your specimen will assume when you do one of the experiments mentioned above. They need a bit
more information about the material than what you get from simple tensile testing alone, and they need big computers,
but tensile testing provides the core information.
Modern machines for doing tensile tests are shown below.

Tensile Test Equipment
The machines are from different companies but lookquite similar. That's because they are engineered toperform the same task: breaking things in style.
Specimen such as shown below, with standardized shape and dimensions, are clamped into the heavy jaws of themachine. The idea is to pull so that the specimen gets longer, while simultaneously recording and displaying the pulling
force and the elongation.
It's also possible to push or squeeze but the data you get are not much different from pulling. More to that in the science
module.

Iron, Steel and Swords script - Page 30

Broken specimen (Al, Cu, Graphite)
Of course, if you rip a steel paper clip apart, you need far less force than when you rip a steel sword blade apart. Since
we want to get numbers for the properties of the material or specific properties, we want to test in such a way that the
numbers we get do not depend on the specimen shape and dimensions. This requires three special measures:
1. The specimen is standardized, usually it is a cylindrical rod. The top and bottom part are much thicker than themain part so the heavy clamping does not influence the results. Just look at the picture above and you get theidea. The length and diameter of the rods are not very important even so we usually keep them at some definedvalues. It is enough, in principle, to know those two numbers so they can be fed to the machine's computer.
2. We measure the elongation not in absolute units like cm, but simply in percent of the initial length. We don't
call it elongation any more either but strain. I must point out that in polite scientific circles strain is actually notmeasured in percent but for reasons of simplifying math, in 1/100 of a percent. If a scientist talks about a strain of
0.01 (without saying percent or anything else, it would be a strain of 0.01 · 100 = 1% for us.
That takes care of specimen with different lengths. A long specimen will elongate more than a short specimen forthe same applied force, but the strain measured in percent of the original length will be the same for both.
3. For the same reason we will not measure the force but the stress.
Stress is simply force divided by the cross-sectional area.
It's stress and not force we need to know, because the results then are independent of the cross-sectional area.
For cylindrical specimen that means that their diameter or thickness doesn't matter.
A specimen with twice the cross-sectional area of our standard sample would need twice the force for the sameelongation or the same strain. In other words: The same stress gives the same strain, no matter how long andthick the specimen is.
Measuring stress and strain with cylindrical specimen thus makes the results we get specific for the material andcompletely independent of the specimen size.
It's essential that you understand this. So let's repeat it:

Stress = force per area
Strain = Elongation in percent
Equal stress gives equal strain
Stress, strain, elongation and so on are common words of the English language but here they become not only avery special meaning but can be expressed in numbers. That will also be true for some words / special expressions
coming up. That's why I give you a quick reference module in the link.
Our present-day machines are quite smart but not yet quite as smart (I hope) as you, their Boss. So before you turn on
the machine and start to pull, you must tell the machine exactly how it should proceed. Now think about that. What are
you going to tell your machine?

Think!
Did you realize that you can do a tensile test in many different ways? For example:
You could tell the machine to apply a certain constant stress. That will produce some strain, your specimen
elongates by a certain percentage. Record that strain. After that is done the stress should be increased a bit,
producing a somewhat larger strain, and so on.
Alternatively, you could tell the machine to strain the specimen to some extent, for example 0,1 %, andrecord the stress needed for this. After that is done, the strain should be increased, and so on.
You could tell your machine to increase the stress at a constant rate from zero to some final value and tomeasure the strain while it does that.
Modern machines will listen, and you can program them to do your worst. They will not complain. My engineer incharge of the equipment won't complain either if you suggest one of the above procedures, he will just kick you out
Iron, Steel and Swords script - Page 31

without much words.
So you should do your best. That means you should do the smart thing—if you can figure it out.
Yes? You have no other suggestions? Sorry to hear that.
So just believe me (that's pretty smart, too).
What you tell the machine is that you want it to apply a certain constant deformation rate or strain rate and that itshould see to it that the strain rate chosen is kept absolutely constant until the end. That means that the machineneeds to adjust the stress at any instant to the value needed at that point in time. Next, it is to record the stress it
needs at any moment and display strain vs. stress on its monitor.
That simply means that you instruct the machine to elongate or strain your specimen a defined amount per second(that's a rate). You may want a strain rate of 0,1 % per second, for example. That means that a 100 mm sample will
now be pulled in such a way that every second it becomes 0,1 % or 0,1 mm longer. The strain then is a simple
function of elapsed time: after 1 second it would be 0,1 %, after 10 seconds it is 1 %, and so on.
Our present-day machines are fairly smart. They can measure the strain somehow, keep track of the time, andcalculate the strain rate from this. If it deviates a tiny little bit from what it should be, the machine adjusts (andrecords) the stress to a level where the desired strain rate is achieved again. There is an active feed-back control
loop, in other words.
Doing a tensile test this way is quite important. If you let me have your fancy wootz steel blade, I can cut off a piece, put
it in my machine and rip it apart. If I tell the computer of the machine the cross-sectional area and the initial length of thespecimen, it will give me solid numbers for specific properties of your wootz steel for the particular strain rate (andtemperature) chosen.
However, I will get different numbers for different strain rates or temperatures. Maybe those numbers are not terribly
different but the differences aren't negligibly small either. Sorry. Tensile testing is a bit more involved as it appearson the outset.
This teaches us a little lesson:

Assigning only one number
like hardness to a blade
oversimplifies the case quite a bit.
Stress, by the way, must have the dimension of force divided by area. This comes out as Newton/square meter or N/m 2.
Force per area is also known as pressure but we only use the word "pressure" when it's the same everywhere andnot just in one direction. When you dive, you feel the same water pressure from all directions. Every surface
segment of your body experiences the same stress. When Procrustes or its successor, the holy inquisition,elongated you on the rack, you feel "pressure" only in one direction and that is why we don't call it pressure but
quite aptly (uniaxial) stress.
Uniaxial stress, by the way, is far more punishing for specimens than pressure from all sides. The pressure you
experience at a diving depth of some 10 meters is bearable. If it would be applied uniaxial, you're dead. That effect is
not specific to soft matter like you but is felt by all materials.
A stress of 1 Newton per square meter is also called 1 Pascal (P). Pascals are quite unfortunate units (you may
blame it on the French) because 1 Pascal is a tiny stress or pressure. In real life we always encounter Mega orGiga Pascals, more about that later.
A Newton, as you certainly know but can't remember right now, is the one and only internationally allowed unit forforce. It's defined as the force that accelerates a mass of 1 kg by 1 m/s 2. 1 Newton (1 N) therefore is defined as 1
N = 1 kgm/s2.
In other words, since you know (I hope) that the earth with its gravitational pull provides for an acceleration of 9,81
m/s2 on its surface, it thus exerts a force of 9.81 N on a mass of 1 kg. If your mass is 100 kg like mine, thegravitational force of the earth that keeps me from floating off into space equals 981 N.
By the way, you Americans, Liberians and Myanmarians out there: No, there is no such thing as a pound, an inch orworse, pounds per square inch (psi); not to mention ounce, yard, mile or any non-metric unit of length and weightmeasurements.

Iron, Steel and Swords script - Page 32

BasicLink
SI System

All these quaint old units have been outlawed byinternational treaties, signed by all countries
except the three above, long ago. Why? Because
the SI (Standard International) meter - kilogram second system is far, far better for measuring
things, not to mention science and engineering,
than your God-fearing, outmoded, old and stupid, if
time honored system non-system.
Why do a few people still use it? Could it be for thesame basic reason that caused people a whileback not to use superior iron but inferior bronze?
Too damn lazy to learn a new trick?

Basic
Link
Length,Conversion

Now that you remembered your Newtons and so on, you can forget them again. Just bear in mind that I know exactly
what's going on during a tensile test and that you can believe the data I will give you.
My machine, while straining the specimen with considerable power if needs be, still has time to construct a highlyinteresting graph and display it. This is the stress - strain diagram, produced for the particular strain rate chosen,
and usually for room temperature. A stress - strain diagram is what we really are after in a tensile test. It gives us alot of specific data about the specimen.
I give you a simple example of a stress-strain diagram done without costly equipment. You know that particularstress - strain diagram from many experiments that you did yourself. You just never put it on paper.

Stress - Strain diagram for a rubber band
I'm pulling at a regular rubber band with my finger. The
resulting stress-strain diagram is shown in a qualitativeway (no or guessed numbers!). A crusader-type(Templar) sword replica provides the "clamping" on one
end.
Pulling out a rubber band by hand is exactly the same as doing a tensile test with a fancy machine. Except thatyou don't get precise numbers. But we don't need that here. You can easily pull a rubber band to 4 times and moreof its original length, i.e. induce a strain of 400 % and more. Starting from strain 0 %, you have to increase the force
or stress as we call it now about linearly for keeping the strain rate constant. In other words: twice the length takes
twice the force stress, three times the length takes thrice the stress.
If you let go, the strain goes right back to zero. In other words, it doesn't matter if you go up or down with the stress;
you are always on the same curve. This is indicated by the two arrows in the drawing above.
Eventually, for very large strains, you come to the end of what you can do with a rubber band. The rubber band
seems to get harder; you have to increase your pull stress quite a bit now to increase its length just a little bit more.
This is a warning that something is going to happen if you go on. If you ignore the warning and keep going, therubber band will snap or fracture without straining much more.
The stress-strain curve belonging to this behavior must look as shown. In the beginning it increases linearly; near to
the end it goes up steeply.
Here is your homework:

Iron, Steel and Swords script - Page 33

Ponder what basic kind of stress -strain diagram you would get while pulling at:i) a diamond rod,ii) a glass rod or any other brittle substance,iii) a rubber band (let's see if you remember),iv) a copper, gold, or any soft metal rod,v) a sword blade or any hard but tough metal.
Consider first what will happen if you just pull a little and then let go. Then pull some more, until
fracture.

But first appreciate the beauty of thought experiments like the ones in your exercise.
You don't need to go out and buy a diamond rod (not cheap) and the costly equipment
to destroy it with. You just have to imagine all that - correctly, of course. You don't evenhave to get up. You can do the exercise while sitting in your easy chair, drinking beer.
I just recommend access to pencil and paper. Sometimes my students do thought
experiments like that upon my request; we call that an oral examination. Only theprofessor gets to sit in an easy chair and drink beer in this case.
But that doesn't apply to you. I won't even give you a bad grade if you get it wrong or if
you don't do it at all. That's shows what a great a guy I am. Maybe you should send mesome money?

ImportantmoduleBeer and
SwordsWhen you now hook up your diamond rod and your other specimen to your brain machine, or a real paper clip toyour hands, and start pulling, you might feel that nothing happens at all. But that only means that you are notstrong enough, or that your vision is not good enough. If you cannot apply sufficient stress to produce strain that isvisible to the naked eye, you simply need to look at your specimen through a microscope (low magnification will
be sufficient) to see its elongation.
If you apply stress, small or large, something must happen. The strain might just be too small to be "obvious"!
Just don't use a scale with 100 % strain in your diagram, go, perhaps, for just 1%.
By the way, a brain microscope is also good enough for your experiments; you still do not have to get up. Use a
bit more beer, whisky or red wine if your brain microscope doesn't seem to focus properly on your first try.
Now get to it. Give it your best shot.

Think!

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3.1.2 Stiff or Hard?
Pulling at Brittle Materials
I hope you did your homework. Now let's look at the answers to the questions and see how well you did.
Let's start with the first two questions: Ponder what basic kind of stress-strain diagram you would get while pullingat: i) a diamond rod, ii) a glass rod or any other brittle substance. Here is what it could look likeStress - strain diagrams for brittle materials
The "slope" part will be explained further down.

While my diagram shows numbers on the axes, you didn't need to worry about that. There is no way you can know
those numbers. I don't know them either but know where to look them up (and how to cheat a little to come up withthe figure).
What your diagram (with no numbers on the axes) should show are at least two straight lines. A steep and long one
for diamond, and a somewhat less steep and shorter one for a glass rod or any other brittle substance. Let's see
why you could have figured that out.
If you pull at brittle materials like diamonds or glass they will strain just a tiny bit while applying only small stress. So
what - it is measurable, even if you don't see it. If the stress is doubled, the strain doubles. If the stress exceeds some
limit called fracture stress, the material simply breaks. There is no warning in the stress - strain curve that brittle
fracture is imminent.
Since you probably never pulled at a glass rod you may not have experienced that first hand. But you know thatwhen you bend glass - or any brittle material: It breaks without warning if you reach a small but critical deformation.
Bending experiments are far more messy for calculations than just pulling or pushing experiments but qualitatively
not all that different. Double the effort and bending doubles. Too much bending and fracture happens. So you could
have guessed at some straight line for the tensile test.
There is more. If you release the strain at any point below the fracture stress, strain and stress go right back tozero; the arrows indicate this. In other words, the material has exactly the same length it had before the test.
We call that kind of response to stress " elastic deformation".
All brittle materials show only elastic behavior as longs as they don't break.
Now let's see why you could have guessed that diamond has a steeper and longer line than other brittle materials.
Diamond is the hardest material out there, you know that. That can only mean that it deforms less for equal stressthan other, less hard materials. In other words, it shows less strain for the same stress then glass or china, andthus its curve must be steeper.
Why should it be longer or going to higher stresses before it breaks? Well - guess! What will be probably harder tobreak, everything else being equal? A piece of diamond or a piece of glass? Don't tell me you would go for glass if
asked this question.
My figures actually give numbers on this behavior. First of all, those numbers show, as you suspected, that you can't
elongate brittle materials much before they break. Than we have something like a maximum stress for fracture of 7 GPaor seven Giga Pascal or 7 ·109 Pa. How much is that in everyday terms? Well , imagine me in drag. If I borrow my wife's
high heels and put all my weight on just one heel, the stress is about 10 MPa. We need about hundred guys like me ona 1 cm2 heel, or a pin-head sized 1 mm2 heel with me alone, to produce 1 GPa.
I've already admitted that I cheated a little on two points, so now I'm going to confess. First, materialwise, there issimply no such thing as "glass" or "china". There are many different kinds of those materials, and they all differ
somewhat in their behavior. The curves given are thus typical but not specific. Some other glass or china specimen
might show quite different curves. Nevertheless, the diamond curve is always steeper and longer then the china curve,
Iron, Steel and Swords script - Page 35

and so on.
Second, nobody in her right mind would do a tensile test with brittle specimen. For starters, they would already breakwhen you clamp them into the machine. Moreover, even if you manage to do that with some kind of tricks, they would
fracture at values that are not characteristic for the material but just for the quality of its surface. In real life we therefore
do compressive tests for those materials, and the numbers I used come from compressive tests, indeed. But in athought experiment, where you don't need to worry about the boring problems just described because you can imagine
ideal surfaces and ideal clamping, the curves would come out as shown.
Now let's proceeed to the third task: Ponder what basic kind of stress -strain diagram you would get while pulling at iii) a
rubber band (let's see if you remember).
In the figure below I look at rubber once more. Rubber at room temperature can be strained a lot and behaves
always fully elastic. Stop pulling and it always resumes its original length.
But in contrast to diamond and glass, or just about all the "common" brittle materials, it gives you a fair warningwhen it is about to break: it's stress - strain curve deviates from a straight line and goes "up". After pulling it to aconsiderable length, it rather suddenly feels that it will "give" no more. That simply means that you now have toapply far more stress to induce a bit more strain. If you ignore that warning and increase the stress, it breaks.

Stress - strain diagrams for brittle materials

In the figure above I also included the stress - strain diagram you would find at (very) low temperatures. Rubber than
behaves pretty much like glass or other brittle materials.
I did not expect you to know that. However, you may have seen experiments where somebody puts a rubber hose, aflower, or some other soft stuff into some liquid nitrogen and then shatters the cold things to a million pieces byhitting them with a hammer. So what, you might have thought, the stuff now is frozen and everybody can shatter ice
with a hammer, while it's not possible with water (in bags). You're right as far as flowers are concerned but not as far
as rubber and its relatives are concerned. There is no water inside rubber that could freeze.
The "low temperature embrittlement" of rubber led to the 1986 space shuttle "Challenger" disaster, by the way.
What is going on in inside rubber when you pull at it would be a fascinating tale on its own but since we are notoverly interested in rubber swords, I'll drop this subject right here. However, I will not drop the "low temperatureembrittlement" of steel, when I get to it!
Some First Conclusions
Let's describe brittle behavior in other words. Brittle materials are not given to permanent or plastic deformation(besides fracturing). You cannot give brittle materials a different shape by pulling or pushing at them.
We all know that. Nobody sober has ever tried to convert a beer glass into a wine glass by banging it with ahammer. With a metal beer goblet , things would be entirely different. Let's put that in large print:

Brittle materials deform only elasticallyand never permanently or plastically.

Now let's generalize a bit. When you bang things with a hammer, or squeeze them with pliers; when you pull at yourhair or kick your ... (insert the target of your choice), you are doing a deformation experiment. It's just a very unscientificexperiment because you stress an irregular specimen in an irregular way. It is nevertheless a deformation experiment.

Iron, Steel and Swords script - Page 36

Your specimen will react to whatever local stress it feels by experiencing local strain. The kicked object will feel alot of stress wherever it's contacted by the tip of your boots and not much (physical) stress anywhere else. It will
respond with a lot of strain at that point and react to that by some deformation (and, if your specimen is an
animated object, by making noises and kicking back).
Let's formulate a simple but important truth:

Any deformation can be calculated byconsidering the local
stress - strain conditions

Note that I did not say "easily calculated". It is in fact a rather difficult task. Nevertheless, if you break your diamondin a (virtual) tensile test or by banging it with a hammer, the material "diamond" responds to the acting stress via its
specific properties that describe this material. And so does your sword.
The next thing to note is that temperature must be considered, the rubber example demonstrates that rather
dramatically. On the other hand, our brittle materials from the first tasks do not change their behavior very much withtemperature.
All I want to do here is to make you aware that temperature might be important. Some materials like rubber (andpossible your sword) become far more brittle at low temperatures, others like glass or silicon (Si), lose theirbrittleness at higher temperatures and become viscous or ductile. This will be of major importance for what follows.
Maybe you noticed that so far I did not bring up the "strain rate" that I used for our virtual experiments. Strange,
considering that I made such a fuss about that in the preceding subchapter.
Well, it turns out that for the experiments we did so far, the strain rate doesn't matter much. We get essentially thesame curves for different strain rates, just believe me on this. It is nevertheless important that you do theexperiments in a well-defined way.
Some space above I made a big deal about the length and the slope of the straight lines describing the elastic
deformation of brittle materials. That are, of course, the two properties that distinguish different brittle materials. We suremust look at this in more detail.
Fracture Stress and Young's Modulus
Let's start with the "length" of the stress - strain curve. It simply tells you where the curve ends or, in other word, at whatstress and strain the material breaks.
Great. Let's define a fracture stress and a fracture strain for the material in question and tabulate it as in intrinsic
and important property of that material. Well - no, let's not! As hinted at above, fracture of real brittle material occurs
for all kinds of reasons that are not properties of the material itself. You cannot shatter you car window glass bybanging it as hard as you can with a hammer (try it). Then scratch it just a tiny little bit with something hard like thediamonds in your ring, and it will now fracture immediately on the slightest impact. That's why you have these little
hammer in busses and trains with a very hard tip to scratch and shatter the windows in an emergency.
I will have a lot to say about fracture in modules to come. Here we just note that tensile (or compressive) tests(done right and with all kinds of tricks) will give you only a very rough idea about the fracture properties of materials
and that is why I won't go into that any more.
So let's look at the slope of the stress -strain diagrams. As long as we have straight lines, the slope is the same
everywhere and that's why we will give it a name:

Slope of a stress - strain curve= Young's modulus

How one measures a slope is shown for the diamond curve in the top figure. Draw some triangle to the curve asshown and divide the length of the vertical part by the length of the horizontal part. As long as you do that with astraight line, it obviously doesn't matter how large the triangle is. For diamond, a Young's modulus of 125 GPa
results.
Iron, Steel and Swords script - Page 37

Young's modulus is also called tensile modulus; or a bit sloppily elastic modulus or modulus of elasticity. The
sloppiness comes from the fact that there are several elastic moduli for a given material. Young's modulus is justone of them but the most important one.
By the way, if you know the least little thing about calculus, you realize that the definition above applies to all
curves, not just straight lines. If calculus is not something you know and enjoy, forget this remark.
The five curves in the two figures above represent substantial differences with respect to Young's modulus of thematerials tested. For the first three curves you can derive Young's modulus yourself, for the rubber case you can't
because I didn't give numbers on the axes'. What you can appreciate, however, is that Young's modulus of cold rubber
is much larger that that of rubber proper. It can easily be more than 1000 times larger!
Young's Modulus is instrumental for the stiffness of your blade, so we need to look at it in some detail. Let's re-express
the definition from right above:

Young's modulus measures how much stressit takes to deform a material by 0.01 %Young's modulus thus describes a special stress and thus is given in units of stress = force per area. It is typicallygiven in "Gigapascals" or GPa, meaning one billion (= 109 = Giga) Pascals. Pascals are force (= Newton = N) per
area. I covered that already but I promised repetitions.
Materials with a large Young's modulus take a lot of stress to make them a bit
longer, materials with a small Young's modulus elongate easily. The same is true
for bending something elastically.
As ascertained before, Young's modulus is directly related to the slope or the
steepness of the curve in a stress - strain diagrams or their derivative inmathematical terms. Now I have used the d-word. Since the "derivative" (of afunction) is a dirty word for many, I will not go on but refer the brave to the science
module that deals with the issue.

Science
Link
Tensile test

The simple rule is: Steep curves relate to large Youngs' moduli, flatter curves to smaller ones as shown in the figure
above. Rubber at room temperature has an extremely small Young's modulus.

Characterizing Materials by Their Young's Modulus
Now that we have characterized materials by their Young's's modulus, we need a name for the property assessed in thisway. What would you call the property described by Young's modulus?
Toughness ? No! That word we have already equated with ductile behavior.
Hardness? Nice try! A diamond has a larger Young's modulus than glass and is harder, indeed. So thanks - but
no! Hard materials tend to have a large Young's modulus but there is no direct relations. Young's modulus has
not much to do with what we call hardness and measure with hardness tests.
Elasticity? Wouldn't you rather reserve that word for assessing how much you can elastically elongate or bend
something, and not for how much force you have to apply for elongating / bending?
Let me help you:

We call the material-specific property measured by Young's
modulus:
Stiffness

Iron, Steel and Swords script - Page 38

Note right away that what you would conceive as the stiffness of your blade is probably not the same thing as
what I introduced here. What you might see as the stiffness of your blade depends on two completely unrelated
things:1. The specific stiffness of the material it's made from, or Young's modulus of the material, or what I consider as
stiffness only , and:2. The precise cross-section of your blade, or a purely geometrical parameter.
A thick broad blade is "stiffer" of course than a thin and slender one, even so the material for both has the same
stiffness. The dependence of blade stiffness on geometry is "trivial", however, from a materials point of view. It is justa number you need to get and then it is trivial to use. It's not quite so trivial, however, to calculate that number. I willdeal with that here.
The important thing is to realize and remember that "stiffness" as described by the numerical value of Young's modulus
has nothing to do with fracture strain, hardness or ductility.
So a material with a large Young's modulus we would call very stiff material. It might be hard, too, but you cannot
derive the hardness from a known stiffness, just as you cannot tell if a material is silvery or red from knowing its
stiffness. It's just not the same.
Now to the next problem:
The word "stiff" is used when we describe a large Young's modulus or a high degree of stiffness. So what do we call amaterial with a small Young's modulus like rubber?
Soft ? No!
Soft is the opposite of hard—and not the opposite of very stiff.
I must admit that there is no good name for that. Pick what you like, for example docile, pliant or resilient. On
second thoughts, be careful about resilience. That name is already taken for the ability of a material to absorb
energy when deformed elastically.
What I'm driving at is that you should be careful about what is meant if somebody uses well-known everyday words like"strong", "hard", "tough", "stiff", "resilient", or "soft" for describing mechanical properties of a material. It's often not goodenough and prone to cause confusion.
Just to remind you that this is a scientific article, albeit without equations and fancy language, I will give you now an
idea about numbers for Young's modulus. In science we like to be quantitative.

Young's modulus for some materials - Graphic

Material

DiamondWC

Al 2O3Al

BronzeBrassConcrete

Glass

Iron
Steel

Fe3C

Y (Gpa)

1220

≈600

435

69

95 - 1120

≈20

50 90

190 210≈200

Young's modulus for some materials - Numbers

Iron, Steel and Swords script - Page 39

What you see is that, yes, hard materials like diamond or tungsten carbide (WC), taking "hard" for the time being in theregular sense of the word, tend to have a large Young's modulus. But there are still big differences.
Diamond (C) and Tungsten carbide (WC) are both very hard and both have large but substantially different Young's
moduli. Sapphire, also known as Aluminum oxide (Al2O3, the hard little crystals on emery paper that scratch mostmaterials when you "sand" them), is also quite hard but has an even smaller Young's modulus.
Polystyrene ("Styropore") as one representative of the large number of polymers out there is soft and has a verysmall Young's modulus.
So, yes again. There is a certain common trend between stiffness and hardness. But, once more, it is not thesame. Far from it—as we will see in the context of swords right below.
First, however, I must address the question you might have. So you wouldn't have thought of polystyrene, or iron (Fe),magnesium (Mg), steel, rubber and so on as being brittle?. So why did I assign a Young's modulus to them, consideringthat we are discussing only brittle materials at that moment and that I only defined Young's modulus as the slope of thestress-strain curve of brittle materials?
If you really ask that question you didn't do your homework - or you got it wrong. I'll come to that in a minute.
Now you must, I repeat must note something quite relevant to our topic here:

Pure and rather soft iron has the same
Young's modulus or stiffness as hard steel!

All steels have the same specific stiffness! I just claim this without giving a reason. Do you believe me? Yes? You'rea sucker. You should believe me, of course, but not without asking: why?
Why do all steels have the same specific stiffness?
I'm going to tell you why it can't be otherwise - but not before chapter 4.1.3.
Let's look at some other materials in the figure above. CFC, short for carbon fiber composite, the stuff of modern
airplanes, tennis rackets and Formula 1 cars, has a relatively large Young's modulus compared to GFC, glass fiber
composites , the stuff for boat hulls, swimming pools, and so on. Wood has a small Young's modulus and tooth enamel
and nacre (= mother of pearl) are doing fine compared to magnesium or polymers. Both consist of high-modulus
calcium phosphate or calcium carbonate, respectively, encased in a low-modulus matrix of bio-polymers or proteins.
Aha - we are talking composite properties here. Young's modulus of the composite materials given in the table issome average of the moduli of the components and often much larger than that of the low-modulus matrix.
Pattern welded "damascene" sword blades are usually conceived to be composite materials of hard and soft steel.
It's not quite true and in any case both steels have the same Young's modulus. Now you should wonder what
advantage this composite technique offers. It is certainly not an improved stiffness of the blade.
Now don't forget: we are talking Young's modulus here, not hardness. When we bend a blade elastically, Young's
modulus (and its shape) tells us how difficult that is going to be. We always hope that it deforms exclusively
elastically since the only other options are breakage or plastic deformation (staying bend) and we hate that.
Bend? By now I have used a new if familiar term several times for a special kind of deformation. It's time to look at it a
bit more closely.
So far I just discussed mainly tensile testing, straight pulling or pushing. Specimen got longer of shorter but they did not
bend. This gave us Young's modulus. But what does Young's modulus have to do with bending?
Relax. Even so I do not give equations here, you realized; I hope, that with Young's modulus it is fairly easy andstraightforward to calculate what would happen to a specimen if you pull or push.
It is just as possible, if far less straightforward, to calculate what would happen elastically to a specimen if you try
to bend it or to mutilate it in other way—as long as you know its Young's modulus (and its shape, of course).
Now comes the "tough", "hard" or "stiff" question: How does a pattern-welded Celtic "damascene" blade, or a hard-softhard cross-section Japanese sword blade, bend elastically when compared to a geometrically identical blade that is
made from uniform soft or hard steel?
The answer shouldn't surprise you anymore: All blades with the same cross-section bend pretty much the sameway.
Since elastic deformation for a given shape concerns only Young's modulus, and since Young's modulus is thesame for all kinds of iron and (carbon) steels, there is no appreciable difference.
So what's the advantage of damascene and other tricky techniques? It cannot influence a swords stiffness and thus its
bending behavior.
We have a really tough (sic) question. The answer has to wait for quite a while. First we need to look at yourremaining assignments. This quick reference module might help
Iron, Steel and Swords script - Page 40

3.1.3 Just For You
We still have to look at questions iv) and v) of your homework, the tensile testing of soft metals like copper (Cu) or gold(Au) and hard metals like steel. Did you come up with a result?
The figure below gives the answer in the form of real stress-strain diagrams for a bunch of different metals. To
demonstrate a few points of tensile testing with respect to steel and sword making, I have done a number of tensilestress experiments just for you, the reader of this hyperscript.
That's a damned lie, of course, because it wasn't me but my able assistants who actually did the experiments they wouldn't let me ruin their treasured (and expensive) testing equipment.

Stress - strain diagrams of various metals.
For clarity, the zero point for strain has been shiftedsomewhat for each curve.
The scale shows "Megapascals" (MPa) and, as promised, I give you another idea here of what that means.
Consider your weight. If you are a guy like me, we take it to be 100 kg (OK, just once: about 220 pounds). If you
climb up a rope (I doubt that you can do this if you are a guy like me, but let's just assume you can), you are pullingat that rope with a force of 100 kg × 9,81 m/s2 = 981 kgm/s2 = 981 N. That's about the maximum force you can
produce: pulling with all your weight.
How thick should the rope be to take your weight?
If you don't use extremely strong monofilament, somewhat less than a square centimeter should be fine, let's say
0,3 cm2 (= 3 · 10–5 m2). That corresponds to a rope with a diameter of about 0,6 cm = 6 mm. Sort of like this: O
The stress in the rope then would be 981 N / 3 · 10–5 m2 = 32,7 MPa. So take note: The maximum stress you can
produce pulling with all your weight on a 0,3 cm2 cross-section is about 30 MPa. There you have it. When real men
produce mechanical stress by pulling at ropes, Mega Pascals are what you need to measure it with.
Of course, the psychological stress that professors like me can produce in undergraduates taking an oral exam will
exceed that by far— but it's not measured in MPa. That's just another reminder that mere words are just mere
words. Real men scientists need clear definitions and numbers if one is to know what is really talked about.
Now let's focus on the major point: The stress - strain curves we get for ductile materials as shown above arecompletely different from the ones we had before for brittle materials

The stress -strain curves show
plastic deformation
Plastic deformation is any deformation
where the shape has permanently
changed after releasing the stressThis is indicated for the steel ST 37N curve. Stop your machine at some point like the one indicated, release thestress and the strain will be permanent (about 15 % for the example shown). The specimen is now permanently
longer. It has been plastically deformed.
Iron, Steel and Swords script - Page 41

Now let's look at the other major features of those curves.
1. Eventually, after the specimen have been elongated to some final value indicated by the star, all specimen
fracture as shown before. This is just an expression of the first law of materials science that we will encounter in fullglory presently.
2. There are four kinds of steel in the figure. One (St 37N) is just as easily deformed as copper or aluminum, while
the C45 type seems to be much harder in the sense that you have to apply far more stress to elongate it a few
percent permanently or plastically.
So, in pronounced contrast to their stiffness , all steels are not equal when it comes to their resistance to plastic
deformation.
You know, of course, that there are different kinds of steel with respect to hardness from what you know or haveheard about swords. The question then is if there is some kind of relation between hardness and what we have here.
There is. I'm coming to that. But first let's look at what else is of interest.
3. All curves run through a maximum stress shortly before they break. That means that if you elongated thematerials up to that maximum, it now becomes easier to elongate them some more up to fracture. In other words:
the ductile materials give you a fair warning that they are about to break, just like rubber. But in contrast to rubber,that becomes stiffer just before it breaks, ductile materials appear to become "weaker" (once more we lack a proper
word) right before fracture.
4. Once more: if you release the stress at any one point to the right of the "perpendicular " part in the beginning, thestrain does not go back to zero. The specimen stays elongated.
The curves shown are thus the "upward curves", showing what happens if you increase the stress, strain and thus
elongation. They are completely different from the "downward" curve. The downward curve simply goes almost
straight down as indicated for the steel (ST 37N) curve at one point.
Now let's look at the not-so-obvious features. As a little surprise for you, I had a few more tests done; look at the next
figure:Stress - strain curves of one and the same kind ofsteel.
For clarity, the zero point for strain has been shiftedsomewhat for each curve.
What we see is that one and the same kind of steel shows rather different behavior in tensile testing.
That's good. What that means is that you can change the properties of a given piece of steel by doing proper things to it
like hammering it, or heating it, cooling it rapidly, and so on.
Here we are at the very beginning of the science of making swords.
So what was done to the steel in the figure above and what has changed?
Well, curve 1 shows the properties of the steel "as bought". That's what you get when you buy C15 steel. The steel
is pretty hard to deform. The machine needs to apply something like 700 MPa to elongate it just 1 %. It fractures
after it was strained to about 1,5 %.
If you would pull at the specimen with all your might, your measly 30 MPa or so applied to a wire of that steel would
just elongate it by about 0,04 %. You wouldn't notice this.
Curve 2 shows the steel after I annealed or normalized it. That simply means that the steel was kept at atemperature around 900 oC (1652 oF) for at least 30 minutes. "Annealing" means to do something by hightemperatures, and "normalizing" means that you follow some prescribed recipes specifying how long you anneal atwhat temperature. More about the upcoming "why " questions to these procedures later.
What you see is that after annealing / normalizing the steel, we need only half the stress from before to elongate it
1%. We can also strain the steel now to more than 3% before it breaks.
It appears that keeping steel hot for some time tends to make it easier to deform or "softer".

Iron, Steel and Swords script - Page 42

Curve 3 is exactly the same annealed steel as that in curve 2 but some devious person (might have been me)
secretly strained it to about 2 % before giving it to the engineer in charge of the tensile test machine without telling
him.
Being smart, he might see that this piece of steel has been in a tensile test machine before (the big jaws of themachine leave traces), but being smart myself, I had removed all traces before I pass on the specimen.
For my engineer (or anybody else), this specimen looks no different from the ones he tested before. There is no(easy) way of telling that it had been pre-stressed.
We have a major point here. Somebody gives you a piece of metal for a tensile test, and there is just no (easy) way ofknowing if somebody hasn't pulled at it, banged it with a hammer, or done God knows what to the specimen, changing
its properties in a major way before it was given to you.
In other words:

The history of a piece of metal is importantfor its mechanical behavior.
This is a major point. Consider the difference to brittle materials:
Somebody might have deformed a brittle material like glass (without breaking it, of course) in any conceivable way
to his hearts contents. But when you come into possession of that glass, it behaves exactly as if all of that had not
happened. It's history is not important at all.
Ductile materials obviously have a kind of "memory" where information about what has happened in the past is
stored. This is rather weird, think about it! The corresponding "how?" question is obvious and doesn't need to bespelled out in detail. The answer to it will contain much of what you need to know about the art of sword making.
That will exercise us quite a lot in what follows.
There are two more interesting points to be made about our three stress - strain curves from above:

1. If we move curve 3 to the right, it matches perfectly with curve 2 if we start it at around 2 % deformation.(curve3a). In other words: if we stop the deformation of the sample represented by curve 2 at the circle and then release
the stress, the strain would go down as shown by the green arrow. The sample is now permanently or plastically
deformed, it is longer than it was before the test by about 1,9 %.
If we take this sample and test it again, counting the strain from 0 %, we get curve 3.
In essence we just continued where we left off. Our specimen "remembered" its past; its history is somehow stored
in its structure. But if you don't know the history of your piece of steel, you would tend to see it as something
different from the steel of curve 2. It is "harder" but less ductile, and it breaks earlier.

2. Looking once more at the stress- strain curves above for the C15 steel, we note another peculiarity: In the
beginning - for about the first 0,1 % of elongation - all three specimen behave exactly the same way. The stress strain curves are linear and have the same slope. When we looked a brittle material, we identified the slope of astress - strain curve with its Young's modulus. Can we do the same thing here again?
Yes, we can. In the straight parts of the diagrams above we just deform the steel elastically. Release the strain andthe specimen goes right back to its original length as indicated by the arrows.
So we can assign a Young's modulus modulus to ductile materials too, we just need to keep the stress /strain at alevel low enough to have only elastic behavior. We are going to look at this more closely in the next sub-chapter.
Now you know why I could discuss Young's modulus for all materials in the preceding sub-chapter.
By the way, I also proved now experimentally the claim I made before: Three rather different kinds of steel have one
and the same Young's modulus because the slope of all three curves is the same, indeed.
What the experiment has given us is a first glimpse at hardening mechanisms and softening mechanisms.
There are several mechanism to harden metals. What we did to the C15 steel in the figure above is called
deformation hardening, strain hardening or work hardening. Different words but meaning the same Workhardening is just one of several hardening mechanisms we will encounter.
Temperature treatments known as annealing or normalizing, meaning that you keep your steel hot for a while, seemto soften steel. Well, they do—but only if you do it right (furnace with controlled atmosphere and temperature, very
slow cooling down, ...).
If you just shove your steel it into a fire and take it out again, you might be in for a surprise. For example, if you cool
your steel down rapidly after it was hot some time, it might not be softer but much harder—provided the temperatureand the carbon content was high enough.
In a fire, you also might either add a bit of carbon or remove some, depending how exactly you hold your steel into
the fire or coals. What you take out of the fire then is a different material since a little bit of carbon, as you know ofcourse, typically hardens steel.
So working with iron and steel is tricky. What about the remaining 90 or so elements of the periodic table? Or just the
20 or so major metals? Can we also make them harder or softer like iron / steel?
The answer to this "what" question is: yes, in principle.
And now we are stuck with a lot of "why? and "how?" questions!
Iron, Steel and Swords script - Page 43

3.1.4 A Bit More About Tensile Testing
We now give general or typical stress - strain curves of metals a closer look and define some terms. For that we look at
the figure below. Let's go through major properties not yet discussed.

Typical stress-strain curve for a metal and shapeof the specimen.
With this drawing I define the most importantparameters.
All metals deform purely elastically for small enough stress. That's not surprising. It is exactly what you hope thatyour metal object—your sword, your car part, your fork, your elevator cable —will do when used. You don't want it tochange its shape permanently.
You sure enough put stress on those parts when you use them, and you certainly assume that the engineers in chargeof designing those objects knew how to make them in a way that they will only deform elastically under the various
stresses you are going to challenge them with.
As far as sword forging goes, that is the key. As long as your sword only deforms elastically when you hit somethingwith it, all is well. It will then neither come close to fracture, nor will it remain bend and out of shape. That is your thebest option for sword behavior.
Alas! If you hit another good sword edge on edge, you get a lot of force on a small area, or a very high stress . You
will quite definitely exceed any limits for elastic deformation locally. The only options left are fracture or plastic
deformation.
Of course you go for the plastic deformation option: Suffering some plastic deformation locally is bad but far better
than fracture. You have a local change of shape—a nick or dent—but still a usable sword.
Come to think of it, local plastic deformation is always a good option if the alternative is fracture. Run your car
against a tree and you are much better off with just the front part dented than with everything broken.
I will get back to this later again because it is quite important.
If we go beyond the maximum stress for only elastic deformation, we will reach some special stress that is called theyield stress or the yield strength; often abbreviated RP for historical reasons (we also have already used up the letter"Y" for Young's modulus).
As soon as the applied stress reaches the yield stress, the material starts to "yield", it starts to deform plastically . Up
to this point it behaves purely elastically. This is important:

Plastic deformation begins as soon as
the yield stressof a material is reached

Once again, because it is so important: Stress your materials but stay below the yield stress. It doesn't matter if
you do this by pulling, pushing or any combination. Now release the stress and your material goes back to strain
zero, assuming its old dimension.
That is the reason why ductile materials (and just about every material) can be assigned a Young's modulus.
After reaching the yield stress, further pulling (or pushing) will increase (or decrease) the length of ductile materials
considerably. If you release the stress now (dashed blue lines in the figure above), the material shortens a little
because the elastic part of the strain relaxes but it remains longer. It is now plastically deformed.
By the way:

Iron, Steel and Swords script - Page 44

What is commonly known as "hardness"
is nothing more than the yield stress,
just measured in different units.
There you have it. Expressions like "hard to deform" do make sense after all. Provided you mean "hard to deform
plastically ". Here is a link illustrating this point with experimental results.
We will go into this in more detail later. What we note here is that hardening steel first and topmost means to increase
its yield stress.
Put simply, you need more force or stress to plastically deform hard steel then you would need for mild or "soft"
steel. It is harder to bend a paper clip made from hard steel into some strange shape than one made from soft
copper. Note that the word hard appears here with two different meanings. It denotes the well-defined measurable
quantity "hardness" and some feeling expressed in colloquial language.
I hope you got it that the sentence in the green box up there is nothing less than an epiphany or enlightenment! You
now have a first idea about what hardness is in terms of materials properties. We will delve much deeper into the
topic in chapters to come.
After I have written a lot of words about the critical yield stress, or "RP", or hardness, we now move on to the next
interesting feature of the stress - strain diagram. We note again that there is some maximum in the stress - strain
curve that gives us the ultimate tensile strength usually abbreviated RM.
More stress than that the material cannot take. If you apply more stress than RM, the material would elongate
quickly and break.
A well-programmed tensile test machine would never do that because it is keeping the strain rate constant,remember? After the strain going with RM is reached, the machine needs to decrease the stress to increase thestrain. That's why the curve has a downwards slope after RM.
You might force the machine to apply a stress larger than the ultimate tensile strength, you're the boss, after all.
You will then invariably produce a larger and larger strain rate, leading quickly to fracture.
Let's define some terms now.
The total change in length before fracture we call ductility. Ductility thus simply measures the maximum elongationin percent that you can get on top of the purely elastic deformation (always at best 0,1 % - 0,3 %).
Ductility typically will be between a few percent and a few ten percent for metals, but there are exceptions. Some
metals—and wootz steel might be one of them—show the phenomena of super plasticity, exhibiting very large
ductility up to or even above 100 % - at high temperatures, that is.
For reasons well understood the cylindrical rod we are pulling just gets uniformly longer and thinner while we
increase the stress until we reach the ultimate tensile strength. If we keep pulling at the given constant strain rate(and for that the machine must actually release the stress a bit now), "necking" will start.
Necking in this case has nothing to do with what you and your girl friend might have done way back on the backseat of your Volkswagen. Here it simply means that a "neck" develops: the specimen gets locally thinner andthinner until it breaks at the thinnest part.
The stress - strain diagrams for all materials are hiding a last important property. It is the specific fracture energy,
the amount of work = energy per cubic cm (J/cm3) you need to invest in you specimen so it finally breaks in a neattensile test.
Oops! Sorry! The "J/cm3" or "Joules per cubic centimeter" right above just slipped in. Joules; abbreviated J, as I
sincerely hope you know or at least knew, is the basic unit for energy. If electrical energy is involved, we also use
the unit "Watt second " (Ws), and 1 Ws = 1 J. In case of doubt, look it up.
The fracture energy is simply given by integrating the stress as a function of strain - excuse me; I almost slipped
into an equation involving the really dirty "i" word.
Let's try again: The specific fracture energy is simply given by the area under a stress-strain curve. This is illustrated
below.

Iron, Steel and Swords script - Page 45

Fracture energy = area under the stress strain curve.
Brittle materials with large
Young's modulus (steep slope)and large fracture stress do notnecessarily have a higher
fracture energy (area under the
curve) compared to less stiff
materials fracturing more easily

The fracture energy ofductile materials isalways much larger thanthat of brittle materials.
Note difference in scale

By the way, if you ever wondered what all that incomprehensible calculus, that sadistic math teachers forced on you inhigh school, is good for: stress-strain diagrams provide a good example.
The fracture energy is just the integral of the stress-strain curve taken from zero strain to the fracture strain.
Young's modulus results from taking the derivative of the curve at the elastic part for small stress.
The ultimate tensile strength is determined by setting the derivative of the curve to zero.
The tensile test machine knows how to do this. How about you?
Why are we interested in the fracture energy?

Because it is one of the reasons why you
may want to put "soft" steel
inside a hard steel sword blade

Whenever your sword hits something or gets hit, it has to absorb a certain amount of energy, possibly in a rather small
area of impact and thus small volume.
If the energy deposited locally exceeds the specific fracture energy your sword breaks. It is (almost) as simple as
that.
Nevertheless, I will not emphasize the specific fracture energy as derived from stress-strain curves too much. Why?
Because it's a great number for characterizing nice uniform specimen in a nice careful test, but it doesn't do so well formessy real materials under violent ill-defined conditions.
When you hit another sword with your sword, or when King Richard (Lion Heart) cleaved the iron handle of a mazeto demonstrate the quality of his sword to Sultan Saladin (here is where that particular myth comes from), theconditions are quite different from a neat tensile test with low strain rates. I will therefore give fracture a sub-chapter
of its own.
But before I do this, we need to consider a few last points on tensile testing.
First, let's look at the strain rate a bit more closely. What you get in terms of the stress-strain curves depends on
how fast you strain. Above a certain (rather low) strain rate, faster deformation always means that the material
appears to be "harder".
If you hit your opponent's sword with your sword, the deformation on the swords, if there is any, will happen rather
fast. That seems to be positive because the material appears harder, but there is always a price to pay. It's a good
guess that during a short impact time you can't absorb as much energy as when you pull or press on your material
slowly. So instead of having some deformation (which is bad) you might have fracture (which is far worse). So wemust take strain rates into account when we look at sword blade properties.
Now a word to the opposite of the tensile test: compressive stress testing. Instead of pulling we push. We havecompressive stress instead of tensile stress and now we compress the specimen until it fractures or, better word,
bursts.

Iron, Steel and Swords script - Page 46

Compressive testing is a bit messy for large stresses because your specimen thenwill tend to bow. Press on your sword with the point fixed on the floor, and it will
bow out elastically (we hope).
Apart from that, compressing the specimen means doing just the opposite of
tensile testing. A ductile specimen under compressive load first deforms elasticallywith a stiffness given by the same Young's modulus you find on tensile loading.
After reaching the same yield strength as in tensile testing, it will begin to deform
plastically. The stress strain-curve for not too large stress looks the same, justinverted, as in tensile testing. Well, no—only if you take a little care to adjust forthe changed geometry.

Science
Link
Compressive
test

For example the specimen gets thicker and not thinner and that needs corrections that involve logarithms and other
hated math subjects, so I will not get into that. Look up the science module if you can bear the (simple) math.
If you do that and you know what happens for simple straight pulling, you also know what will happen for simple
straight pushing .
Now comes a big theorem.

If you know what happens for
simple straight pulling, you cancalculate what will happen forany mechanical loading
Pulling in one direction and pushing in another one, for example, bending, shearing or banging with a hammer, whatever.
Concerning your job as smith for making swords, that is what you need. You never just "pull" at your sword; you rather
bend it or suffer complex stress distributions in all directions if you hit something hard with the edge of the blade.
Note that I haven't said that those calculations are easy. They are not. Things like tensor calculus are involved, thesame kind of math you need for Einstein's theory of general relativity, which isn't known for being particularly easy.
It's always good to have powerful theorems. It's even better to test them experimentally.
Given that real materials are never uniform, simple and well-behaved like "theoretical" materials, we don't just do tricky
calculations and believe them unconditionally. We always measure major properties experimentally, and compare themeasured values with the (needless to say, computer run) numerical calculations. "We", needless to say, means
scientists and not, for example, economists or theologians, for comparison. They just believe, and that's why the
economy (or moral rectitude) crashes far more often then structural designs like building, bridges, and so on.
When you, the ancient smith forges a sword blade, you apply stress in a complex way and consequently you deformthe material in a complex way. You do not just elongate a cylindrical piece of iron like in a tensile test. When you workwith your hammer, you rather are closer to pushing instead of pulling.
No matter. From the viewpoint of some tiny piece of iron inside the whole big piece
you are about to crash you hammer down upon, it just feels some compressive
stress; it is violently pushed down. It's neighbors are also pushed down to someextent, and all want to bulge out a bit to the sides. All those little connected pieces
might feel different forces from the hammer, react to it, and pass on some stress totheir neighbors.
The total effect is some total or global deformation resulting from the various local
deformations of the connected pieces of iron. And all of that can be calculated if weknow the data from the tensile test. The link tells more.

Science
Link
Deformation

The so-called "metal-bending industry", about the biggest industry we have, depends completely on the ability ofsome materials to be able to undergo plastic deformation.
Isn't it strange that until about 1934 nobody had the faintest notion of what exactly is going on inside a material
when it deforms plastically ? Isn't it even stranger that hardly anybody knows the unsung heroes of science who
unraveled the big mystery in 1934 and beyond?
The very persons whose ground-breaking work not only led the metal-bending industry to unprecedented progress
but also opened the door for the electronic revolution?
Not to mention that based on their insights, we can now start to understand why the ancient smiths did what theydid?
You get to meet some of those great people in the next chapters.

Iron, Steel and Swords script - Page 47

3.2 Fracture Toughness
3.2.1 A Few Basics about Fracture
It's time to introduce the first law of materials science:

You can break anything if you're brutal enough
Just kidding, of course. Or am I?
The first law of Materials Science states that everything will break if sufficient force is applied. It certainly applies toswords.
With a tensile test you can always fracture your specimen if your machine is powerful enough. If we keep on pulling,
the specimen will be broken in the end.
The stress-strain curve gives us quantitative data (meaning numbers) about the maximum stress a material cantake, the maximum strain or elongation it suffers before breaking, and the work we have to do (the fracture energy)
to deform it up to the final fracture.
The picture below gives an idea of what machines look like that can break almost everything. It also shows that a lotof effort and money is going into tensile testing. We simply need the data.

Monster machine for breaking things
Data from tensile testing are sufficient for describing all kinds of material deformations. Unfortunately they are not goodenough by far to tell you everything about fracturing your material. After all, you and I know that things, including all
metal things and thus sword blades, don't just fracture by being slowly and lovingly, if forcefully, being pulled apart.
If a sword fractures, it is almost always a violent and fast affair resulting from sudden and violent stress applied to just asmall part of the blade.
Let's look at few examples. Even "tough" sword blades might fracture and not bend if deformed very quickly. The
sword of an officer who was dishonorably discharged was often ceremonially broken by bending it rapidly over yourknee. Bending slowly may not have done the trick.
If you press a somewhat dull chisel slowly into a metal sheet, you will get a dent. If you do it rapidly (bang on thechisel with a hammer) you get a dent and a hole = fracture.
Things are even worse than that. Metal constructions that stood stable under some load for many years sometimes
suddenly collapse without any outside influence like a big storm. Whenever metals break by fracture for no apparent
reason, we call that failure.
I don't know if old swords that were very good at their times fracture more easily when tried some hundred years later,
but I would not be surprised. Things like that happen more often than we like with other steel objects.
The roof of the rather big congress hall in Berlin suddenly collapsed in 1980 after it stood there for 23 years. Thatdisaster was due to stress corrosion cracking in the steel beams, an especially treacherous failure mechanism.
Another creepy mechanism for things that are under steady mechanical load but otherwise do nothing is aptly
called "creep ". Creep, given time, will lead to slow deformation and sudden fracture.
On top of all that we have fatigue, causing sudden fracture of metals after some time of active service. Fatigue may
occur if some parts experience low-level oscillating forces. In other words, fatigue might occur if the metal vibrates toIron, Steel and Swords script - Page 48

some small extent for some time
The most spectacular example of this kind of fracture you can find in the Internet, looking under "Boeing roofless"where you will find an airplane that converted itself into a convertible in mid-flight. Parts of the cabin just flew off, due
to fatigue, and the passengers found themselves suddenly in a roofless airplane but did not really enjoy the fresh air.
I need to say a lot more to creep and fatigue, answering the obvious "why" questions you must have by now. But
before we get there, we need to do some work first.
It is true, we don't care all that much about slow processes on time scales of many years in connection with sword
blades; I just thought I let you know that fracture has man facets. Nowadays we understand them quite well, but not aswell as we would like. Otherwise major disasters concerning sudden and unexpected fracture of metal things would not
happen as they do.
By the way, if I claim we "understood" something, I mean that the science of that topic has reached a point where
we can predict what will happen under certain circumstances with great confidence. I do not mean that we can only
explain retrospectively what has happened (like your stock broker).
Understanding fracture, however, means understanding structural changes in materials. Understand structuralchanges in materials means understanding the structure of materials first. That will take a few chapters; after that
we will return to the subject.
For the remainder, let's look at fracture only in an experimental way and see how one can do some useful fracture tests
besides uniaxial pulling and pushing. What we need, for example, are experimental assessments of how fracture prone
a given piece of steel like a sword blade would be.
One simple way of doing this is to fracture a sample under conditions reminiscent of a sword fight. We will look atthat in the next sub-chapter.

Iron, Steel and Swords script - Page 49

3.2.2 The Charpy Impact Test
So how do we test a piece of steel in ways reminiscent of a sword fight?
You typically notch your specimen a bit on the backside and clamp it securely in the jaws of the machine. The
notch is important because it makes sure where the specimen is going to fracture. You just "override" all othersmall surface flaws that might be there.
Then you hit the specimen with your sword. Actually, you don't. You hit it with what is called a "hammer" but thathammer has a pointed edge and just as well could be part of a massive sword.
You just as well could describe this as hitting the specimen with a good sword blade.
This is the "Charpy " test. It doesn't fool around with first drawing out your specimen like in a tensile test but fractures itright away and rather fast. Schematically, it looks like this:.

The Charpy impact test
The securely clamped standard size specimen is hit
by a pivoting "hammer" with a pointed edge. The inset
shows the specimen geometry.
In order to do this right every time, you fix your hammer at a point just above your specimen around which it can rotate
freely.
The hammer then hits the specimens always in exactly the same spot in exactly the same way with exactly thesame "force" or better energy. For an experiment you move up your "hammer" to the same position 1 at a height h1, as shown above, and then let go.
The hammer will come down, gain speed, whack right through your specimen, and run up to a height h2 on theother side.
Now we need a little physics:
The hammer will hit the specimen with an energy that's directly given by its initial height h1 times its mass m times
standard gravity acceleration on this planet known as g = 9,81 cm/s2. Remember "potential energy"? If not, justimagine that I would jump down from some height right on top your toes. It's going to hurt more if I jump from alarger height.
The hammer cleaves the specimen and ascends on the other side to a height h2 that's always smaller then h1. The
difference in height /energy before and after cleaving the sample ((h1 - h 2)mg) is easy enough to measure andcalculate. It is usually given in units of Joule (J).
The energy "lost" by the the hammer is quite obviously the energy , or in other and synonymous words, the "work"or "effort" needed to fracture the sample.
Its just like chopping wood. You hit the block of wood with all your might any time, and what's left of the energy after
you cleave it, determines how deep your axe sinks into the block.
What we get with the Charpy test (and with similar tests) is once more a number for the fracture energy.
In the Charpy test we get the energy needed to fracture a sample with a typical cross-sectional area of 1 cm2practically instantaneously.This is quite different from the energy it takes too fracture a specimen after it has beendrawn out leisurely to the maximum length it can bear.
The two numbers obtained by the two methods can be quite different—even so they must be closely related. If weMaterials Scientists are as good as I keep claiming, we should be able to calculate one from the other. Well we
can't and it doesn't worry us. You see, Charpy tests are not very precise. If different people with different machines
test the same material, the numbers they get might be rather different. That's simply due to the fact that a lot ofsmall factors influence the final result: how you make the notch, the precise geometry of the notch, and so on. But
then the numerical value of one test is not very interesting, anyway. What counts are series of test. If series aredone in the same way and with the same machine, the results are very meaningful because they show trends thatare independ of the exact numbers. Here is an example.

Iron, Steel and Swords script - Page 50

So why are we doing a Charpy test? For the same reason we do hardness tests: Those test are easy. The Charpy
test, like a hardness test, is easier to do than more sophisticated test like tensile pulling. And that is particularly
true if your specimen is small or if you want to go to temperatures substantially different from room temperature. All
you have to do is to heat or cool your specimen to the desired temperature and then quickly test it. Since thespecimen is rather large it will not change its temperature very much during the time needed to take it it to themachine and shatter it.
When we do just a simple Charpy impact test and measure the impact fracture energy at different temperatures for one
kind of material (again, far easier to do than with more demanding methods), we learn that some steels shows somerather peculiar behavior called cold shortness. This link provides more information about cold shortness than you want toknow at this point in the narrative, so you use it with caution.

Some steels show a tendency to become
quite brittle at low temperature.
This was known as coldshort
If some material becomes more brittle", it simply means that it takes less energy for fracture than in its less brittle
state. Look at those diagrams again if you don't see it.
The word "short ", by the way, doesn't relate to size here but is old English for: "having a tendency to break or
crumble". The shortcake you like so much means "crumbly "cake and not "size-wise challenged" cake.
For reasons of symmetry let's quickly look at some other effect of temperature on the behavior of steel that worriedpeople for millennia:

Some steels show a tendency to become
more brittle at (medium) high temperature.
This was known as redshort
The "red" in "redshort" refers to a temperature where the iron glows red. You don't need to do a Charpy impact test
to figure that out. It was sufficient to hit hot steel with your regular hammer as a smith to experience the effects ofredshortness first hand.
How unique is this peculiar behavior of some steels?
Many other metals like gold, (Au), copper (Cu), Aluminum (Al) or nickel (Ni) never show this kind of behavior.
Some other metals like titanium (Ti), magnesium (Mg), or cobalt (Co) are rather brittle under the Charpy hammer at
all temperatures—even so they can be quite ductile in the tensile test.
In general, most materials become more ductile with increasing temperature (or more brittle with decreasing
temperatures. Some, like silicon (Si) and other semiconductors are perfectly brittle at low temperatures and nicely
ductile at high temperatures.
Logic dictates that there must be a "brittle-to-ductile transition" at some temperature.
For coldshort carbon steels, this brittle to ductile transition happens around or just a bit below room temperature.
This means that your steel will fracture easily in ice cold water while being ductile at somewhat more higher
temperatures. That actually happened to certain ships. In cold water they broke apart.
Now we have a puzzle.

WHY?
Why is temperature having such a big influence on fracture behavior? And why is there a fundamental difference
between groups of metals that are otherwise quite similar like nickel (Ni) and cobalt (Co)?
The good news is that I could tell you; the bad news is that you're not yet at a level where you would understand. I
therefore will get back to this question as soon as I explained a few basic facts of life inside a crystal to you.
Now to more bad news:

Fracture energy is still not sufficient
to describe all fracture modesof materials including sword blades.
Iron, Steel and Swords script - Page 51

3.2.3 Fracture and Microcracks
You simply cannot descibe the fracture behavior of a material in just one number. When we nevertheless do just that, it
is akin to bankers describing you in just one number like "net worth". The number is not necessarily wrong but does not
do justice to all aspects of you (I hope).
If Materials Scientists describe fracture behavior in just one number, they do not use the easily measured fractureenergy but a more sophisticated measure called "fracture toughness ". The unit of fracture toughness is Pam½
(Pascal times square root of meter) and now you know that you don't want to know more about that - yet.
However, if you are a reckless enterprising spirit, you find more about that in the science module "Fracture
Mechanics".
Fracture mechanics belongs to one of the most difficult fields of Materials Science.
It is supposed to be able to calculate under which kind of mechanical loading
things break right away. That's tough enough but it also supposed to be able tocalculate under which kind of conditions things, fail, i.e. break eventually.
Generalizing a bit, the really tough question for Material Science to answer, is:Why do things go kaput? Why does pretty much everything, including you, failsooner or later? This is transcending just fracture mechanics since it includes
topics like:

Science
Link
Fracture
Mechanics

Why can you bend your sword a hundred times to some extend and at the hundred-and-first try it snaps?
Why do tightly wound screws come loose after a while?
Why do your computer chips die after some time of use? I'm talking hardware here, not software.
Why does your light source eventually fail? And I'm not just considering the good old light bulb but any
source, including modern LED's.
Why do your cells stop to work properly as you get old?
I will give answers to some of "why" questions coming up in this context but not before we covered far more ground.
As far as fracture mechanics is concerned, I will go only one notch above of what I covered already. Looking at serious
fracture mechanics would need several notches. I thus will only look at fracture that occurs right away under someconditions of overloading to relatively brittle materials. Relatively brittle materials are either really brittle materials likeglass or ductile materials like iron that have been strained close to the breaking point.
The general experience is that some swords (or other objects) if hit hard will fracture while some other swords, madefrom virtually identical steel, do not. Virtually identical might mean, for example, that the yield strengths or hardnessesof the two steels are quite similar.
The major reason for this different behavior can be expressed as follows:

Fracture of all materials, including
ductile metals, depends sensitively
on the presence of what wewill call nanocracks
Strange enough, nanocracks are generally called microcracks in serious literature about fracture. It is strange because
nowadays many rather ordinary things that are not nano at all (meaning smaller than 100 nm) are called "nano this-orthat". But the cracks causing fracture, which are truly in the nanometer dimensions, we call "micro". How come?
Simple. Back in the good old times, everything very small was called micro this-or-that. We scientists didn't have toinvent new fancy names like nano this-or-that to get funding in those good old times.
A nanocrack is any small area inside your material where your material does not stick together properly; I'll get tothat later in more detail. Nanocracks might be "true" cracks like the cracks propagating into glass whem it breaks,
just much, much smaller, or an inclusion of something with not much strength, for example graphite in (cast) iron.
Nanocracks thus are "defects" in the material and typically so small that you can't see them, not even in the mostpowerful optical microscopes at thousandfold magnification. Even if your microscope would be a hundred times
better, magnifying things hundred-thousand times, you would have a hard time to see the nanocracks that makesome steels more fracture prone than others.
Unfortunately, there are a lot of reasons why materials should contain or develop nanocracks with different if small sizes,
shapes and densities (number per cubic centimeters). What that means is that there are a lot of reasons why identicalmaterials might show different fracture behavior.
That it is always the largest nanocrack in the material that initiates fracture doesn't make things easier.
In other words: a steel that contains one largish (still invisible) nanocrack and a few smaller ones will break moreeasily than a steel that contains a hell of a lot of medium sized ones. One bad apple spoils the bunch, as thesaying goes.
Iron, Steel and Swords script - Page 52

It's time for a epiphany:

Minimizing nanocracks in your blade isdone by folding and hammer-weldingof your primary steel.
You, the ancient smith, couldn't avoid the nanocracks and all kinds of other defects inside the steel pieces you pickedfrom the smelter. Your nanocracks were actually not even so "nano", they were rather large. Your best bet was tohomogenize your material and make sure that its properties were the same throughout. This needed a lot of heating,folding and banging, and that helped to erase nanocracks, or at least make them smaller.
You, the ancient smith, certainly did not know what kind of nanocracks your material contained.
You didn't even know what yourmaterial was for God's sake.
You just had a common name like"iron" for it. You did not have the true
name of your material because thatwould have meant

Attention! I'm getting
fundamental; veering
off the topic!

that you would have power over it. The
word "nano", if you understood Greek,
meant simply "dwarf" to you. "Steel"
was another word for, perhaps, somekind of especially pure iron.

I, a modern day materials scientist, do know what my material is. I know the true name of the object. In the olddays that meant I held power over the object and could do magic. It means the same thing in the new days. We do
hold incredible power!
You, the ancient smith, had to deal with your material empirically since you did not know its true name. You gained
knowledge by learning from your master and by trial and error of your own. With time you became experienced anddeveloped a feeling of what could be done with the material at hand.
You never deviated from recipes that worked. If all of sudden they didn't work anymore (and that happened for sure;it still happens in "High Tech" work of today), you were puzzled and frightened. Your only recourse was to sacrifice
to your Gods and hope for the best, like that your bosses wouldn't sacrifice you.
In most cases some solution was found or imported from somewhere else. Empirical knowledge grew and eventuallythings like locomotives with many steel parts ran on some iron-related (more cast-iron than steel) rails. The earlytrains derailed and failed a lot—but the industrial revolution, based on steel, had begun. And it began on almost
exclusively empirical knowledge that had accumulated through the millennia.
In our modern times some magicians (also called scientists) do know the true names of things. That's why the canproduce magic like cell phones. You don't believe that? Then prove to me that an i-phone and its brethren do not operate
on magic! I bet you can't.
What was the issue again? Right, nanocracks and fracture!
I can do some magic here because in contrast to you, the ancient smith, I typically know my material and what kind ofnanocracks it contains. Knowing that I can calculate the fracture behavior of my material.
If I don't know what kind of nanocracks my material contains, I look at it with a powerful electron microscope orother sophisticated apparatus and find out.
But there is a catch. The catch is that I can only investigate extremely small regions this way. Worse, I destroy the
specimen by investigating it. So I still don't know with certainty what kind of nanocracks the left-over piece of steel
has that I did not investigate but use for forging a sword or a railroad wheel.
However, looking at many specimen, doing statistics and all that, I will gain objective knowledge and a quantitative
data base about what the material most likely can do.
Most likely, however, does not mean: for sure. Some small uncertainty and residual risks remain.
For example, one out of thousands of lots of a well-known steel did contain a critical nanocrack. That piece of steel
ended up in a train wheel and killed 101 people in 1988, when a high-speed ICE train derailed because of thesudden failure (=fracture) of the wheel after many hours of use.
Horrible accidents like this one seem to cast some doubt on our understanding of materials. Just the opposite istrue. Since we can never completely test the materials we want to use, we need to know about them. In otherwords: we need theory.
What I'm driving at here is the second law of Materials Science and Engineering:

Iron, Steel and Swords script - Page 53

There is nothing more practical than a good theory
Theory tells you exactly if a piece of steel (or whatever) will fracture under some load, provided you know whatever it is
you need to know for doing the calculations. Theory also tells you unambiguously that concerning fracture, you deal withsomething that has intrinsically a statistical component. You only can come up with probabilities.
If you now think that the theory of fracture mechanics is rather useless because it could not prevent the train
accident mentioned above, you are utterly wrong.
Consider how often something critical could break, and how often things actually do break. A railway car wheel, thewheels of your car or of any car. The steel cables of elevators, cranes, or suspension bridges. The steel beams ofhigh rise buildings. The bricks and stones of pyramids, cathedrals or houses. Whatever.
Failure of critical parts happens almost never for two reasons.
1. The parts in question are so much oversized that they can easily bear the load they are subjected to. This
was the time honored way of structural design for millennia. Pyramids, cathedrals, temples, houses, bridges
and so on that could not take the stress have collapsed long ago. What we have left today are the survivors.
The problem with "design by trial and error and large safety margins" is that you use more material andenergy than you would have needed.
2. For some time now we can calculate facture behavior well enough to allow for intelligent design. That's one ofmany reasons for the huge progress made in optimizing the weight - performance ratio. The crucialcomponents of your car are much lighter now than 50 years ago but can take much more punishment. The
ICE train where the disastrous wheel fracture occurred goes 300 km/h; the trains 50 years ago, running onmuch heavier wheels, were far slower. Jumbo jets actuall can fly, for God's sake!
Where does that leave you, the ancient smith? Caught between a rock and a hard place! You did not have scientificknowledge about assessing the properties of your steel and to work it to the best of its properties. You couldn't use
the pyramid builders recipe of making it solid and heavy either. You could have made an unbreakable sword, it justwould have been too heavy to use.
That's why swords are such great objects for studying the history of metal technology. Swords were always at the
cutting edge of technology. Sword makers couldn't play it safe like pyramid builders by using large safety margins.
Let's look at little bit more on what theory is telling us about nanocracks and fracture.
When materials fail after years of flawless service, the small and harmless nanocracks they originally contained
slowly grew bigger and bigger over the years. Eventually one of them reached critical size and —boooom!
There are a number of mechanisms that make nanocracks grow and preventing that can be difficult. That's what
happened in the train wheel.
One way of looking at sudden fracture is therefore the "critical size of nanocrack" concept or what I like to call the"Griffith " concept, after its inventor.
Looking at the fracture toughness of steel or anything else, to introduce the proper word right here, "simply" means toknow under what kind of mechanical loading conditions nanocracks start to grow.
If they grow, fracture is unavoidable; it's just a matter of time. Now if you apply tremendous force or stress (pulling,pushing, banging, whatever) you can break anything quickly.
Look at a car shredder for example. It simply breaks the metal parts of your car into little metal pieces almost
instantaneously by brute force. In this case nanocracks grow with maximum speed, which is the speed of sound in
the material or 5,12 km/s=3,81 miles/s in iron.
If you dive deeply into Griffith theory and don't drown, you may emerge with a way to put a material-specific number on
its fracture toughness as determined by the relative ease of nanocrack growth.
You will even find a way to measure that property, the fracture toughness from above. It gives you at least a goodidea of what you can expect from given materials with flaws called nanocracks.
Fracture toughness too is measured in units of energy; in this case it is the energy needed to enlarge a crack acertain amount. It is a number different from that of a Charpy impact test. It is also more useful for serious
calculations
So what's the difference? The long and short of it is that the fracture energy from the Charpy test tells you how hard
you have to hit your blade (or your opponents blade) so it fractures at the point of impact.
The Griffith fracture toughness tells you if and where your blade will fracture if you bend it too much or apply randommechanical forces that are not just focused at a given "point".
One last point. The energy of a mass of 1 kg falling down from a height of 2 m is about 20 J. As we know from thevarious fracture tests, this is enough to induce fracture in some not-so-good steels

Iron, Steel and Swords script - Page 54

So, yes, King Richard "Lion Heart" could have fractured the iron handle of a mace with a cross section of at besta few cm2 with his heavy (a few kg) sword swinging it down real hard.
The "famous" meeting between him and Sultan Saladin (who cut through a falling silk scarf with his ultra-sharp"wootz" scimitar) is pure fiction, however. It comes from Sir Walter Scott's novel "Talisman" from 1825. It never
took place in reality.

Iron, Steel and Swords script - Page 55

3.3 Hardness
3.3.1 What, Exactly, is Measured by Hardness?
All of us have a pretty good notion of what "hardness" means in the context of materials properties.
Only a select few people, to whom you now belong, have a decent notion of what the terms " yield stress", "ultimate
tensile strength", or "ductility " tells us about materials properties. As you just learned, these properties are very
well defined and measurable by tensile testing.
There is a catch, however. You need expensive equipment and standardized specimen that must be cut from thematerial you want to investigate.
If you own some blade and want to know its mechanical properties, you have to destroy it completely in order toproduce a specimen that can be tested in a tensile test. That's not something you like to do.
Hardness is different. It is easy to measure for any specimen and only "destroys" a tiny part by leaving a barely visible
indentation
There is a catch, however. The first law of economics applies:

First Law of Economics
There is no such thing as a free lunch.
Nothing is for free. Somebody always pays. Mostly it is you. You usually pay for your free lunch sometime after it
took place, directly or indirectly.
Even if you are lucky and don't pay now or ever, somebody else pays. It's never free. "Free gifts" are not only an
oxymoron but even worse. They are neither free nor gifts.
You should therefore not be surprised that there is a price to pay for the ease of hardness testing: it measures a jumbleof primary properties, all mixed up somehow.
As far as metals are concerned, hardness measures in some lumped way a combination of elastic, plastic, and fracture
properties. Hardness then combines somehow yield stress, Young's modulus and fracture parameters.
The bad news is: There is no simple equation that relates the hardness number of some material to the far more
fundamental primary parameters obtained by tensile testing or other clean tests. The best one can do is to provide
some approximate relations for certain classes of materials
The good news is: For most metals including steel there is a very simple relation between the Vickers Hardness
HV and the yield stress (or the ultimate tensile strength if the stress-strain curve goes right up to it).

What is commonly known as hardness
is nothing more than (approximately) theyield stress, just measured in different units.
That's straight from subchapter 3.1.4; I thought you liked to see that really important statement once more. Here aresome data to illustrate this important point.
The figure below shows the (approximate) relation between the various hardness scales and the yield strength. Again:
be aware that this is only approximate!

Hardness scales and relation to yield strength

Iron, Steel and Swords script - Page 56

Getting a number for hardness is far easier (and cheaper) than getting a complete stress-strain curve. So life becomeseasier if you just measure and discuss hardness. That explains why you find a lot of hardness numbers concerningsteel out there in the Net and rather few numbers for yield strength and so on. But you also miss a lot.
In the inner circle of the cognoscenti (that's me and my buddies) it is the other way around. You, the tax payer, havegiven us all that money to buy the expensive machinery needed for going beyond hardness, and we sure use it. I
hope that this hyperscript will convince you that we used that money wisely.
The reason why hardness is not so popular among working engineers is that you can't do the necessary
calculations with just a hardness number. It is simply not sophisticated enough because you just cannot describe
the response of a material to mechanical stress by just one number.
Life would be even easier if we all would use the same hardness scale. Life would be easier too if we all would use thesame scales for lengths weight and so on.
Of course, we don't. In the case of hardness there is even a good reason fort this If we want to measure hardness for
all kinds materials, including very soft and very brittle stuff, one method is not good enough to cover the whole range
encountered.

Iron, Steel and Swords script - Page 57

3.3.2 Ways to Measure Hardness
When you measure hardness, you press some hard and small object (the indenter) into the material to be tested with
sufficient force to leave a permanent impression. The means that you always deform plastically or fracture you specimen
locally. The "size" of the indentation gives you the hardness number.
Methods differ by the material used for the indenter, its size and geometry, how you press, and how you measure.
Since hardness plays a big role in sword blade lore, I give you an overview of the various methods employed.

TypeIndenter
Description

Geometry

Procedure
Shape

Brinell

10 mm sphere
Variable load

Hardness number from load, depth anddiameter of indentation.

Vickers

Diamond pyramid; squarebase

Hardness number from load and width ofindentation.

Knoop

Diamond pyramid;
rectangular baseHardness number from load and depth ofindentation.

RockwellA
CD

Diamond cone

Hardness number from fixed load anddepth of indentation.

Rockwell
B
FG

1/16 inch
steel sphere

RockwellEH

1/8 inchsteel sphere

The fact that there are many ways to measure hardness, producing different numbers for the same specimen,graphically demonstrates that each method has it pros and cons. I won't go into that, however.
As far as steel is concerned, numbers are usually given in either Vickers or Rockwell. With the figure from before youcan easily convert from one scale to the other.
Once more: No hardness test can compete with a tensile test; the latter gives far more information and numbers
useful for calculations. But hardness tests are relatively cheap, easy to do, and in particular applicable to very small
samples and samples with weird shapes.
Just to put hardness in perspective, the following table gives the Vickers hardness of some common materials. Notethat there are variations for one and the same material not only for steel but for almost everything. The number given
thus must be seen as a typical harness.

Iron, Steel and Swords script - Page 58

Metals

Vickers
hardness

Ceramics

Vickers
hardnessTin (Sn)

5

Limestone

250

Aluminum (Al)25

Magnesia (MgO)

500

Gold (Au)35

Window glas

550

Copper (Cu)40

Granite850

Pure iron (Fe)80

Quartz (SiO2)

1200

Good tin bronze (Cu + 10% Sn)

220"China" (Mostly Al2O3)

2500

Mild steel

140

Tungstencarbide (WC)2500

Hardened steel

900

Polymers
Polypropylene

7

Polyvinylchloride (PVC)

16

Polycarbonate

14

Epoxy

45

Iron, Steel and Swords script - Page 59

3.3.3 Let's Summarize
Let's summarize by going from the simple to the difficult.
A perfectly brittle material like glass, with no internal nanocracks or other flaws, will fracture suddenly as soon as anultimate critical fracture stress is reached.
If the brittle material does contain nanocracks or other flaws it will fracture suddenly at some lower stress.
For stresses below the fracture stress it will deform purely elastically and its stiffness is given by its Young's
modulus.
If the stress is released, it assumes exactly its old shape again.
The energy needed to fracture the material is small.
You cannot bang brittle materials into shape. They have the shape they have or they are broken.
A ductile material like any metal with a "perfect" internal structure in the sense that there are no nanocracks, will deformpurely elastically exactly like a brittle material for stresses lower than the yield stress.
It's stiffness in the elastic region is given by its Young's modulus.
If the stress exceeds a critical value named "(critical) yield stress", it starts to deform plastically.
If the stress is released, before the critical yield stress is reached, it assumes exactly its old shape again.
If the stress is released after the critical yield stress has been reached and plastic deformation took place,its shape has permanently changed.
Eventually, for large stresses or strains, fracture occurs.
You can bang ductile materials into shape. Smiths shape a blade by inducing plastic deformation of the iron or
steel.
What exactly happens in the plastic part of the stress-strain curve for one and the same ductile material depends on
many things.
There are "hardening mechanisms", increasing the yield stress while simultaneously decreasing ductility .
Plastic deformation itself is a hardening mechanism; called "work hardening". That means that the plastic propertiesof a given material that you measure in tensile test depend on its history that may be unknown to you. That makes
plastic deformation a rather complex property.
The parameters of plastic deformation like the yield stress also depend on the temperature , very much so in manycases. Some materials like silicon that are perfectly brittle at room temperature become plastic at elevatedtemperature. Iron and steel are much easier to deform and shape at high temperatures as every smith will testify. At
temperatures low enough they will turn brittle.
Fracture thus occurs in two basic modes:
Brittle fracture, needing not much energy and therefore easy to induce.
Ductile fracture, the eventual failing after plastic deformation, taking lots of energy and therefore not so easy
to do.
For any fracture we also have to look at how fast things happen and if the material contains nanocracks or otherinternal flaws that make it more prone to fracture.
Taken all together we can draw two simple conclusions:

1. The precise internal structure of the material matters quite a bit.
2 The role of temperature is also
something that needs
to be looked at.
Now we have our topics for several chapters to come!

Iron, Steel and Swords script - Page 60

4. Iron, Crystals, and the Second Law
4.1 A Close Look at Real Iron
4.1.1 Microscopes
4.1.2 Metals are Crystals
4.1.3 Young's Modulus and Bonding

4.2 A Powerful Threesome
4.2.1 Be Dense!
4.2.2 Being Iron

4.3 The Second Law
4.3.1 Nirvana for Crystals

4.4 Inside a Perfect Crystal
4.4.1 Perfect Crystals and the Second Law
4.4.2 Moving Atoms Around

Iron, Steel and Swords script - Page 61

4. Iron, Crystals, and the Second Law
4.1 A Close Look at Real Iron

4.1.1 Microscopes
Get a piece of iron. Any kind of iron, including "mild steel" with just a little bit of carbon. In case of doubt, cut off a pieceof your car body or take a regular nail.
Now look at it. Not just so but with magnifying glasses or a good microscope.
You don't have one? No matter - just look with your brain not with your eyes. It is easier and far cheaper.

Important News:
Thanks to me you now own a powerfulbrain microscope.
You can crank up the magnification
to at least ten million.
Ten million magnification power! That's well beyond the magnifying power of a standard-issue optical microscope.
Those will give you about thousand-fold magnification at best.
If you're not satisfied with your personal brain microscope at ten million magnification (all brains are not equal, after all),you need to buy a so-called "High Resolution Transmission Electron Microscope", or HRTEM for short, if you want
to be able to keep up with your peers.
The mighty transmission electron microscopes are not to be confused with the lowly "Scanning Electron
Microscopes" or SEM. Those can only show you the surface of your specimen at magnifications rarely exceedinga few hundred thousand. With a HRTEM you can actually look inside the specimen at magnifications exceeding 10
million.
If you want very high magnification or resolution but are satisfied to see just the surface of your iron, you may wantto get a "Scanning Tunneling Microscope" or STM.
Microscopes are not exactly cheap. A simple run-of-the-mill optical microscope,
the kind of microscope all those movie actors pretending to be weird scientists witha German accent are always looking into, slightly frowning because they don't havethe faintest idea of what they are doing, will only set you back 50.000 $ to 100.000$. Those cheapies will also be of no use for what we are about to do.
You need to cough up at least 3 Million $ for a decent HRTEM if you're not satisfied
with your brain microscope. A decent SEM will be around 600.000 $. Simple STM's
you may get already at a bargain price of a few 100.000 $; better ones will take amillion or so

Link Hub

Science ofMicroscopes

If you can come up with that kind of cash, figuring perhaps that some fancy hardware is much showier than your brain
anyway—think again. There is always the first law of economics, remember?
There is no such thing as a free lunch, particularly in science. Even if you can pay for the microscopes, you won't
understand the manual. You must spent at least 5 years of your life (full time) for learning how to work yourmicroscopes.
You can avoid all this expense of money and time if you just use your "brain microscope". All you have to do is toimagine what there is to see. I will help you by telling you what it is that you see.
Of course, if you already know what you will see, you don't have to read on. But changes are you don't, in contrast
to me. OK—I will now help you to operate your brain microscope. First you need to turn it on.

Think!
What are you going to see if you look at your piece of iron at very high magnification with your brain microscope? Given
your halfway decent education, you should know this without me telling you!
Iron, Steel and Swords script - Page 62

OK—since you're still with me, I'm going to tell you. You see:

Iron atoms, of course!
What did you expect? Everything you can see: the stars in the sky, your wife, the TV set, the mountain range, theocean, your boss or your underlings, the dust mites dancing in a ray of light, everything—and that includes
you—consists of atoms and photons.
That's it. There is nothing else for non-scientists like you. It's my and my fellow
scientists privilege that on rare occasions we can also "look" at things that are different
from atoms (including their constituents) and photons. We have, for example:
positrons, muons, quarks and gluons, or some other weird elementary particles.
We have to make those guys with great effort (and plenty of your, the tax-payer's
money), and they usually stick around for only rather short times.
So forget them. Those particles need not concern you at all beyond paying our bills.
You might object and say that if you want to make and run a decent universe, youalso need gravitation. But that is "just" a property that all atoms and photons carryaround with them, and it need not concern us at all as long as we study a piece of ironor steel that is considerably smaller then a small moon.

Advanced
Link
Elementary
particles

What needs to concern you besides atoms is only the photon, the "particle of light".
If you have learned that light is not a particle but an electromagnetic wave, that's fine. The photon as an object ofquantum theory encompasses all of that wave stuff too, and that's why we don't need to worry about electricity andmagnetism here either. It's all in the photon. Light is not just a wave or just a particle, it is light. It was always very
difficult to explain to non-physicists what is meant by photon or wave. But now we have a new word: Waves orparticles are avatars of light. The represent some but not all aspects of the real thing.
We really need the photons so we can see. But they have many other uses too, because
they come in many kinds.
The light that our eyes can perceive consists of photons, and so does the infrared or
ultraviolet light that some animals can see (and my colleagues and I with proper
instrumentation). The microwaves heating your food consist of photons, and so do the
TV and radio waves that soften your brain after prolonged exposure. Of course that's
not done by the photons directly, to be sure, but by the content they were forced totransport.
Photons also come as X-rays and Gamma rays. In this case they are produced byproper machinery, decaying atoms, or exploding stars. All electromagnetic radiationconsists of photons; they are only differentiated by their energy.

Basic
Link
Waves

In case you wondered: I haven't mentioned the electrons that we obviously need for an electron microscope because I
don't need to.
Electrons are part of atoms . If we have atoms, we have electrons. All we need to do is take one out of its atom bybeing a bit brutal (remember the first law of materials science?) The sorry atom, bereaved of one electron, we thencall a positively charged ion but we needn't really to know this for what follows.
We have a big thought here, probably the biggest there is in science:

All that exists around us (including us)
consists of atoms and photons.
There are about 90 different atoms (arranged in the periodic table) that we might encounter when we are looking atthings at very high magnification. As long as we look at our piece of iron, we are going to see iron atoms, andpossibly an occasional carbon (C) or manganese (Mn) atom if we have mild steel. If we look very closely, we findthe occasional atom of everything else, too.
What does a single atom, iron or otherwise, look like?
Nobody knows that from looking at one. You simply can't see it. Not for lack of magnification of your microscope but
because you cannot hold a single atom in the proper position inside your microscope. If you just put it there andthen let go, it will run off.
Also consider: how would you get it there in the first place? All you have to manipulate your single atom with areother atoms.

Iron, Steel and Swords script - Page 63

You now get the idea: We can look at a single atom only when it sits on the surface of a solid formed by a bunch ofother atoms like in this picture.
Alternatively, we can look at a whole bunch of atoms that constitute a solid if, in the direction we are looking, they sit
exactly on top of each other.
If we make our iron specimen thin enough so the electrons of our HRTEM can pass right through, we can put it
inside the microscope and keep it in a fixed position oriented in such a way that we look at a whole column ofatoms.
So if you crank up the magnification of your HRTEM to about 10 million fold, you are going to see atoms as whitish
blobs on your screen. What we are going to see below are gallium (Ga) and arsenic (As) atoms arranged into acrystal called Gallium arsenide (GaAs).

HRTEM picture of columns of Ga and As atoms in
a GaAs crystal
The lines in the left picture are just to guide the eye.
The crystal obviously contains a defect.
Source: from my friends at the KFA Jülich, Germany

This is one of the better pictures of atom (columns) presently available, taken in the "KFA Jülich"; a large German
research institution that was instrumental in developing a new brand of HRTEM's with superior performance.
Every white blob is either a row of Gallium (Ga) atoms or arsenic (As) atoms standing exactly edge-on. I use apicture of Gallium arsenide and not of iron to demonstrate my point because iron pictures are not quite as nice forsome technical reasons that are not important here.
The picture nicely illustrates two important points:
1. The atoms of the substance gallium arsenide (GaAS) are arranged in an orderly pattern. If you have seen afew, you have seen them all. Expressed in other words: if you have seen a few columns of atoms, you know
exactly how to continue their arrangement. Gallium arsenide, in other words, is a crystal .
2. There is some disturbance of the orderly pattern in the center of the picture. Our crystal contains a crystal
defect. Drawing some lines that connect neighboring atoms as done in the right part reveals the nature ofthis defect: it is a dislocation . Jump ahead if you want to know now what a dislocation is.
The two "important points" expressed by the buzz words: "crystal" and "crystal defect" are actually so important that wewill spend this and the next chapter to look into crystals and their defects in some detail. Your sword blade, by the way,
is a crystal. It has the properties it has because of the defects in that crystal.
Oh, I almost forgot: Gallium arsenide (GaAs), a substance you probably never have heard off, is not just something
Materials Scientists use to test their microscopes with. It is nothing less but the paradigmatic material for
optoelectronics, the father and mother of a group of semiconductors that include materials like Gallium aluminium
arsenide (Gax Al 1-xAs), Gallium nitride (GaN) or Gallium phosphide (GaP).
So what is optoelectronics? If you ever used a Laser, e.g. in your DVD player, a light emitting diode (LED), or
optical communication via glass fibers, you used optoelectronic products. No more needs to be said.

Iron, Steel and Swords script - Page 64

4.1.2 Metals are Crystals
What are Crystals?
Now we have the first key to some of our "why" questions. Many of the properties of metals come straight from the factthat all metals are crystals.
In particular, ductility, i.e. the ability to deform plastically, is tied to metals being crystals. The big question then is:

What, exactly, is a crystal?
The first thing you must learn is that a real crystal has nothing to do with the fancy glasses, known as "crystal", thatyou put on your festive dinner table. These so-called "crystals" are in fact the exact opposite of real crystals. They are
made from amorphous glass.
Exactly the same thing holds for all those cute "crystal" things at airport shops all over the world.

Not crystals

Crystals

Crystals and Non-crystals
What I mean by real crystals are all solid materials with an orderly arrangement of most of their atoms as shown
schematically below.

Schematic drawing of a crystalline andamorphous solid.
On the left we have crystalline quartz (SiO2), known
as rock crystal, with an orderly and repetitive
arrangement of the silicon (Si) and oxygen (O) atoms.
On the right is amorphous glass with no apparent
order, consisting once more essentially of SiO2 plus
some incorporated "dirt" like sodium (Na).
On occasion you find obvious crystals in nature. Things like rock crystals (= quartz), diamonds, rubies, and so on. Moreoften, however, you find these kind of crystals in jeweler's shops or in mineral exhibits in museums.
These gemstones and minerals are commonly addressed as "crystals" because
they have some peculiar geometric shape; they come as cubes, pyramids,
octagons, and so on.
You might believe that crystals are rare since most of us find crystals rather
Iron, Steel and Swords script - Page 65

These gemstones and minerals are commonly addressed as "crystals" because
they have some peculiar geometric shape; they come as cubes, pyramids,
octagons, and so on.
You might believe that crystals are rare since most of us find crystals rather
infrequently outside jewelry stores. When did you find your last diamond or ruby on
the beach or in the mountains?
Your believe is wrong. The exact opposite is true.

Misc.
Link
Gemstones

Almost everything that is not somehow
related to biology is a crystal.
Wood, jellyfish, coconuts, fingernails and you are not crystals. Outside of biology, things like obsidian aren't
crystals either. But amorphous minerals are the big exception. Crystals are the rule.
Most of the rocks around us and every metal is a crystal. So how come nobody noticed this?
Because the overwhelming majority of natural crystals are not showy single crystals with an easily recognizable"crystal" shape, but poly crystals, an agglomeration of small crystals stuck together haphazardly. On top of that,these crystals are as full of defects as a politician of BS.
The figure below illustrates that much better than many words:
Schematic
and twodimensional
drawing ofan ideal
perfect
single crystal

Schematic
and twodimensional
drawing of anormal poly
crystal full ofdefects.

It's hard to draw a three-dimensional version of the crystals above. If I would attempt that, the picture would be utterly
confusing.
It's easy, however, to imagine what a three-dimensional perfect single crystal could look like. Just stack manylayers of atoms as seen in the figure above on top of each other and your three-dimensional crystal looks in thisprojection exactly like the two-dimensional case.
The only difference is that instead of just one atom you now have a whole stack. And that's what we are going tosee in a suitable microscope. We must take care to orient the crystal in such a way that we look down a row ofatoms. What we then will see for iron is shown below.

Iron, Steel and Swords script - Page 66

High Resolution
Transmission Electron
Microscope picture of aniron crystal.
Each white spot is a columnof atoms.

How the (cubic)
iron crystal isoriented in thiscase.

Just to demonstrate the point a bit more, I will also show you some pictures of my other favored material: silicon (Si).
The figures below shows images taken with a scanning tunneling microscope or STM. We see only the atoms of
the surface here.
You do not just see the atoms on the surface with an STM, you can even use it to move atoms. In this way you canmake the smallest possible drawings, e.g. the Japanese sign for "atom"

Scanning TunnelingMicroscope (STEM)
picture of a siliconsurface.

Drawing with the STM

The surface of a Si crystal
as seen with an STM (inultra-high vacuum). The
red-white circles are single
silicon atoms. Note that
there are vacancies, too.

Si atoms (the red cones)
on some "featureless"blue substrate. They havebeen individually placed
to form the Japanesesign for "atom"

Source: Omnicron Corp.

Source: IBM STM image galery

In some of the pictures the scale is given in nanometers (nm). Nano is Greek for midget and means really, really small.
We don't need a scale, however, since we know that atoms, roughly, are about 0.3 nm large.
As promised I will not insult your intelligence by always going on about a "thousandth part of a millionth part of ameter", and so on. I presume that you know that "nano" means "billionth part" of whatever, or "whatever multipliedby 10–9".
A nanometer is the billionth part of a meter or the millionth part of a millimeter, and yes, it is really small but not"unimaginably" small. Use the link to refresh your memory if needs be.
Note that right now you do not need to unimagine what a nanometer is. You actually see it. Just keep in mind:

A nanometer is the natural scale for atoms
An atom is roughly 1 nm large (it's more like 1/3 of a nanometer actually), and a nm is therefore also the natural scale
for crystal lattice dimensions.

Iron, Steel and Swords script - Page 67

Single vs. Poly Crystals
Single and rather perfect crystals are indeed quite rare. Dirty poly crystals, full of defects, are all over the place.
If we definitely need single crystals, for example in silicon micro technology or for titanium alloy turbine blades, wehave to make them with great effort.
Usually, however, we are much better off with poly crystals. Not only are they far easier to make and thus far
cheaper than single crystals, they are actually better for many products, like car bodies or swords. Perfection is notalways good; being disordered and messy like the poly crystal in the drawing above, does have advantages formaking swords, as we will see.
Just to make sure you remember: not everything is a crystal. You, just as about all other inwardly slimy biologicalobjects, are not crystalline, neither is glass (typically silicon dioxide with some "dirt", see the figure above).
Man-made polymers like Teflon, nylon, vinyl, acrylic, or "PET" (polyethylenterephthalat, the stuff plastic bottles are
made from), are not crystalline either but also amorphous.
Nevertheless, crystalline materials are far more common than amorphous materials and, remember, all metals are
crystals! Well, almost all. But we need not worry about the few and rather weird exceptions to the rule.
A big "why" question comes up at this point.

Why does a bunch of metal atoms stick
together in an orderly fashion?
Re-phrased and generalized, the question is:Why do most atoms form a crystal most of the time whenever they
stick together?
Going a bit beyond that questions, the next obvious questions is

Is the arrangement of the atoms
in a crystal the same for all metals?
In a first step to getting answers we simply note that most of our 90 or so different atoms like to bond to other atoms.
Bonding between atoms is just another word for saying that the atoms like to share some electrons in some way.
Bonding with a suitable partner (or with more than one partner for the more promiscuous atoms) via exchanging or
sharing electrons, simply makes a better state of being. Bonding with a suitable partner is just more comfy, as
most of us know. Atoms, it appears, are human, too. Or was that the other way around?
While the majority of atoms likes to bond with other ones, a few atoms prefer to be antisocial and stay in splendid
isolation at all circumstances. Those snobs we call "noble" elements. Foremost in this group we have the noble
gases, for example helium (He), argon (Ar), or xenon (Xe). Then we have the noble metals, in particular gold (Au)and platinum (Pt). It makes you wonder how the antisocial behavior of "noble" atoms relates to human nobility, thekind of people who typically induced other people to work for them in exchange for letting them live. The common
denominator might be found in the word "antisocial".
How do we define a "better state of being" or being "comfy" in cold scientific terms? You know when you feel comfy
but how can you put a number on it?
In the world of atoms or other particles, being comfy simply means having as little (free) energy as possible. If you
are a couch potato, why should your atoms be otherwise?
The energy of bonded atoms is usually lower than that of atoms hanging around in isolation, and that's why atoms
like to bond. If you know your atom, you can actually predict its bonding preferences and behavior.
With some quantum theory we can calculate how much energy atoms will gain by pairing up, by forming threesomes,
and so on. This means we have chemistry covered (in principle).
Chemistry, after all, is about getting atoms together to form something new. Take one silicon (Si) atom and two
oxygen (O) atoms, get them close enough, and they will combine to form a Silicon dioxide (SiO2) molecule. Get abunch of those and they will produce solid quartz, one of our most important materials in electronics.
One hydrogen (H) atom and two oxygen (O) atoms produce water (H2O), quite important too. 2 atoms of carbon (C)plus 5 atoms of hydrogen (H) and 1 atom of oxygen (O) produce ethanol (C2H4OH). Mix ethanol with water and add
a little bit of this and that and you have red wine, extremely important for making me comfy.

Iron, Steel and Swords script - Page 68

4.1.3 Young's Modulus and Bonding
You need quantum theory to calculate the bonding between atoms, but you don't need it at all to envision the bonds
between atoms. That's because the result of all those calculations is surprisingly simple. The bonds between atoms
behave just like tiny little springs connecting the bonded atoms. This is shown schematically in the figure on the right.
Of course, if you look a bit more closely, it is not quite that simple. But as long as we only consider "normal" behavior,
like the response to a bit of pulling, we don't have to worry much.
The spring model actually has a lot of explanatory power. Even in serious science
we use it for all kinds of involved calculations. This link explains how one should"read" highly stylized figures like the one on the right.
The strength of a spring simply mirrors the strength of a bond. If you want to makeyour crystal longer or shorter, you must make the springs longer or shorter. You
are, in other words, pulling the atoms apart or squeezing them together a bit.
This takes some force, and force times the distance you pulled measures thework you need to do.
Now we have a first magical word: work! Changing the dimensions of your sword
requires to do some work.
We all have some direct relation to mechanical work. You know that you do a lot of work if you lug heavy things around,and that you're not doing all that much (mechanical) work when you are sitting at your desk, bending a paper clip backand forth to pass the time. The work needed to do something will be in the center of what follows. But before I go on,
you need to appreciate the big magical word now coming up:

Another word for "work" is:EnergyAssume that the bonding springs will "let go" or break if you pull them out to a large distance. This requires somework, and and the work you need to invest we will not call work but bonding energy.
Chemistry is not only about forming some compounds but also about ripping something apart. Take silicon dioxide(SiO2), a material rather plentiful on this planet, rip it apart, and you get silicon (Si) and oxygen (O). Doing that takessome work or, as we call it now, energy, and the bonding energy is a measure of how much work you need to do.
In exactly the same way we make iron and many other substances.
Take some iron oxide (e.g. Fe2O3 or Fe3O4) and rip it apart. On paper you get iron and oxygen; in reality it is bit
more complex but that doesn't matter here. The bonding energy between iron and oxygen atoms tells you howmuch effort, work, or, to use the proper word, energy you must invest in the enterprise.
Take aluminum oxide and rip it apart... OK, you get the drift.
I have credited you with a halfway decent education. So I'm sure you now remember the most important general law
concerning the running of this universe:

Energy is conserved!
The energy contained in some system might change from one kind to another one—but never will it increase or
decrease.
An immediate consequence is that if it takes some defined amount of energy to rip bonded atoms apart, exactly thesame amount of energy must be released if they team up again.
Try it with a mixture of hydrogen and oxygen. You make those atoms by ripping water molecules apart; see above.
This takes a lot of energy. The mating of your isolated hydrogen and oxygen atoms then releases exactly thatenergy rather suddenly, an unforgettable experience for the survivors.
You need to invest the bonding energy for ripping molecules apart and you get exactly the same energy back when
they combine. That's why we call that kind of energy also "chemical energy" When you burn your gasoline in yourcar, you essentially oxidize carbon to CO 2, releasing a lot of chemical or bonding energy because carbon just"likes" to associate with oxygen more than with the partners it had in gasoline (essentially hydrogen).
We are not chemists and we don't like to rip our swords apart. All we might consent to do is to pull at it a little or bend it
a little.
Iron, Steel and Swords script - Page 69

In this case we just elongate (or shorten) the bonding "springs" a little bit. We do a tensile test so we invoke
Young's modulus.
How about an epiphany now?

Young's modulus measures thestrength of the bonding springs
Of course, Young's modulus is not given by the strength of just one spring. It is rather the force you have to apply toelongate all bonding springs found in an area of 1 cm2 by 0.01 %. But that is trivial That's simply the strength of one
spring multiplied by the number of springs involved.
So why did Young define the modulus named after him not in terms of bonding? Because he had no idea aboutatoms and the bonding springs between them. He didn't explain it (as I just did), he just gave a recipe for measuring
a useful property. He had no idea why different materials had different Young's moduli while I have just answered this"why" question.
The insight that Young's modulus represents the strength of the bonds between all the atoms in a crystal has a firstimportant consequence for the elastic properties of sword blades.
As long as we have mostly iron - iron bonds in a sword blade, Young's modulus will
be about the same.
A few percent of other bonds, for example to carbon atoms in steel, will at best
make a difference of a few percent in Young's modulus. This is not open to doubt. It
simply can't be otherwise.
The science link will show how to calculate Young's modulus from bonding spring
properties in great detail. In addition, it will also show how to calculate a few more
properties:

Science
Link
Springmodel

Thermal expansion.
Vibration frequencies of the atoms in a crystal.
Ultimate fracture strength.
Did you experience the required epiphany here?
Did you realize that I have answered the first big why question? Why is Young's modulus about the same for all
steels as claimed in chapter 3.1?
This so important that I illustrate it below once more just to make sure you get the point.

Schematic view of bonds = springs and what happens if
you deform elastically
All springs get elongated. A few different springs (= bonds to foreign atoms) don't make a big
difference.
Why is Young's modulus about the same for all steels, as we noted in chapter 3.1. Because the overwhelming majorityof the bonds = springs that determine Young's modulus are iron - iron bonds. The few iron - carbon bonds in steel simply
cannot make a big difference.
Understanding this makes our top "why" question even more mysterious:

Why does a little bit of carbon makeno noticeable difference forelastic deformation
but a tremendous difference forplastic deformation?

Iron, Steel and Swords script - Page 70

As you know, less than 1 % of carbon turns soft into very hard steel, many times harder than pure iron. And
hardness, as you remember, simply measures the onset of plastic deformation

Why?
By the end of the 5th chapter you will know.

Iron, Steel and Swords script - Page 71

4.2 A Powerful Threesome

4.2.1 Be Dense!
Most atoms, like most people, like to bond. The only party poopers among atoms are the noble gases. They will never
ever associate with anybody else, not even their own kind, except when it is really, really cold.
Noble metals like Gold (Au) and Platinum (Pt) are a bit more social; at least they hang together with their own kind,forming solid gold and platinum. If needs be and you really force them, they also might get together with some of thelesser breeds like chlorine (Cl), but they don't like that very much. They like even less to associate with the proletarian
oxygen (O). That's why they are typically found as pure metal and not as oxides like pretty much everybody else.
Gold, by the way, has not much practical uses. All it can do is to be decorative, just like certain heiresses, duchesses,
princesses, models and so on.
It appears that hanging out only with members of your own class, and looking down at the vast majority of otherelements (antisocial behavior in other words), was conceived to be a "noble" thing when the "noble" elements got
their group name.
But let's not be too tough with our noble elements. Yes, they do loath association with the lower classes, just likehuman nobility—but they didn't rob and kill like real noblemen.
Most of our regular, hard-working metal atoms enjoy very much to consort with oxygen (O) atoms; take aluminum (Al),magnesium (Mg), titanium (Ti) and iron (Fe) as examples. When those metals bond with oxygen, lots of bonding energy
is released. You have seen this. Whenever you watch fireworks, you watch magnesium (and other metals) being burnt(= combined with oxygen). The release of plenty of bonding energy provides the spectacular effects.
Some other metals also like oxygen but aren't too hot about it. Examples are copper (Cu) and silver (Ag). What thatmeans is that their union with oxygen is still favorable but does not release all that much energy. That's why you dofind them as oxides (or other compounds) but also as pure metals.
Most atoms aren't fundamentalists. They do not insist that there is just one way to eternal bliss but keep their options
open. If no sexy and very desirable oxygen atoms can be had as partners, they take whatever they can get. Sulfur (S) or
phosphorus (P), for example. Or something a bit more complex like carbonates (C + O; e.g. FeCO3), hydroxides (H +O; e.g. Fe(OH)2) or silicate (Si + O; e.g. FeSiO3).
What's more, they are not even fixed on being heteros, on getting close only with partners of some other sex. You
got to realize that hetero atoms have far more fun than humans. There are 90 different other sexes out there to playaround with instead of just one for humans! And all of them also like their own kind as a partner just fine, even if
most would prefer oxygen or sulfur. That's why pure metals can exist, too.
Since at this point we are not yet much interested in the various iron oxides (known as iron ores), hydroxides (known asrust), or the more perverse associations, we now look exclusively at the homo-erotic side of iron or all the metals. This
makes life easier because we can deduce a few things.
Consider yourself to be a lonely atom, ready to bond to something. You look around but all you find are other atomsof your own kind. In this case a general rule of thumb applies to many (but not all!) atoms, in particular a lot of metal
atoms. This rule is simple:
You want as many partners as possible.
You want your partners as close as possible.
I just ask you to believe me here. Those rules are reasonable anyway, and easy to substantiate with just a tiny bitof quantum theory. Even without quantum theory, you can see that the two rules result if an atoms attracts someother atom with a force that is the same in all directions. It will then attach other atoms as closely as possible. Aslong as there is still a free space in its surroundings, it can attract more atoms until it is completely surrounded byothers and that implies close-packing as many partners as possible.
If you consider an atom to be a little sphere, applying these rules will now tell you why and how they form a crystal.
You even know what kind of crystal. Think!

Those atoms are just doing what you
would be doing when you stack a bunchof oranges (or canon balls).
Here is the proof:

Iron, Steel and Swords script - Page 72

Stacking of canon balls
Source: Photographed somewhere in Copenhagen

When stacking oranges, without ever thinking about it, you sure like hell form a close-packed arrangement. In otherwords, you arrange spheres in such a way that each sphere has as many neighbors as possible as close as possible.
You follow the rules from above.
So let's do it now - to the extent it can be done on a screen. Take a bunch of cannon balls, oranges, marbles, pingpong balls, atoms, or whatever spherical objects with identical sizes you can find and, as a first step, arrange themas close as possible in a plane. In other words, generate a layer of spheres with the highest packing density
possible.

Evolving the two types of close-packed crystals
Closest possible packingof (blue) spheres or atoms
in one layer.

Adding a second layer(pink) and starting a third
one (blue or red)

How to arrange the first (blue) layer is absolutely clear. The same is true for the second (pink) layer) You just put a first(pink) sphere on the natural place - the indent - on top of the first layer and keep going.
The problem starts with the third layer - and you may not even notice it. What you and I would do is to put somesphere on the natural place - the indent - on top of the second, just as before. Then we go on and add the others
laterally.
You will not encounter any problem doing that. However, you are now generating just one out of the two possible
arrangements that are completely different, except for being close packed.
Let's just look and see what happens if we continue stacking next to the blue and red balls in the right hand part of
the figure above:

Two types of close packed crystals
The third layers with blue / red spheres do not matchat the "seam".
Both variants are fine. You are packing as closely as possible. But they are different. Very different, indeed.

Iron, Steel and Swords script - Page 73

I did not color the third layer blue and red because I was running out of colors. The blue layer is blue because thosespheres sit exactly on top of the first blue layer which I now call an A-plane. The stacking sequence of layers, if wewould go on with this, is ABABAB...
The red spheres are red because the do not sit right on top of the A-plane spheres, and of course they cannot sit on
top of the B-plane spheres either. They are thus something new: the C-plane. Only the 4th plane can be an A-plane
once more so the stacking sequence is ABCABCABC...
Both versions have exactly the same packing density but are otherwise quite different. And please note that in bothcases you get a crystal , and orderly arrangement of spheres = atoms. There is just no way not to get a crystal
following the rules. Here is the answer to one of our bigger why questions:

Why do many atoms form crystals? Because they want to be close
packed!

Why do they want to be close packed? See above.
Both versions, we are sure, have the highest possible packing density. You can't get more balls into a given spacethan arranging them in one of the two ways.
Think about that a bit. Is that really true? If you can disprove that statement by finding some arrangement with aneven higher packing density, you would be an instant super star in the world of math and science. But don't try.
Trust me. You cannot disprove this. Unfortunately you (and I) cannot prove it either (see below).
So stacking atoms in a neat ordered way on top of each other will unavoidably produce not only a crystal, it actually can
produce two types of crystals - and thus gave a first answer to another big why question. "Is the arrangement of theatoms in a crystal the same for all metals?" No, it isn't!
The question we have now is: what kinds of crystals do we get by stacking in the two possible ways?
While it is rather obvious how the blue - pink - blue ABABA... stacking sequence produces the hexagonal crystal
lattice shown in the figure below, it's not so obvious what we get by stacking the blue - pink - red - blue ABCABC...
sequence.

The two close-packed crystals Lattcie points =atoms here.
ABABAB... sequenceor hexagonal close
packed lattice

ABCABC... sequenceor cubic close packed
lattice

It may take you a while to figure out that the ABCABC… stacking sequence generates a nice cubic kind of crystal as
shown above. That's OK. It takes my student quite some time, too.
Your two options are
Sit down and ponder this. Hint: the planes on which we stack the atoms in the blue - pink - red - blue - … or
ABCABC... sequence are the pink diagonal planes bordered in red in the cube above.
Believe me.
We call the crystal units shown in the figure above the elementary cell or unit cell of the crystal lattice with the term"lattice" being self-explaining at this point, I hope.
We have produced two different kinds of crystal lattices by just stacking atoms as tightly as possible. And, yes, topreempt your question: it matters a lot for the properties of a metal if it crystallizes in one way or the other.
I hope you noticed that I have started to answer those questions that came up not long ago?
Thinking hard (very hard) about ways to stack atoms (no longer as close as possible), we will find several more lattice
types. There are 14 altogether, and it is good practice to give those lattices a name.
The ones in the figure above we call "hexagonal close packed", and "face centered cubic".
The distance between the lattice points we call lattice constant(s); 0.3 nm is a typical number for that. One number
will do for a cube; two are needed for a hexagonal lattice.

Iron, Steel and Swords script - Page 74

The terms "cubic", "close-packed ", and "hexagonal" are self-explaining, and so is "face-centered" as soon as you
realize that in that lattice we have an atom each at the corners of the cube and one atom in the center of every faceof the cube.
Scientists like to abbreviate things and henceforth these two types of lattices will be addressed as "hcp" for "hexagonal close packed" and "fcc" for "face centered cubic".
By the way, any atom in both lattices has exactly 12 close neighbors if you start to count. Again, you either believeme or count yourself. More close neighbors you cannot have if you and your neighbors are perfect spheres.
By the way once more, our little exercise did not only produce a lot of new words and abbreviations, it also provided aninteresting (or boring, as the case may be) little conundrum and an acute embarrassment to mathematicians.
Let's say you are the doubting type and ask: are there, maybe, even better ways to pack spheres as closely as
possible than the two ones we came up with, just by fooling around with circles on paper? You're not the first to ask
this (obvious) question.
The question of how to pack as many spheres as possible (with identical diameters) in as little space as possible isquite old. If you have to pack canon balls into cramped ships, you actually like to know the answer.
Johannes Kepler (1571 - 1630), of "earth around the sun" fame, gave the first decisive answer. Kepler theorem:
you do it as shown above, there is no better way. Nobody since has come up with a better arrangement, so
reasonable and practical people tend to believe that Kepler's theorem is true.
There are, however, people who are not reasonable and practical; they are called mathematicians. This people
want a cold, hard, logical and thus mathematical prove that there is no better arrangement.
Kepler could not rigidly prove his theorem. The mathematicians weren't surprised. They thought of him as aphysicist from which you couldn't expect even the simplest math, and set out to prove Kepler's theorem themselves.
Piece of cake, it seemed—but they couldn't do it for more than 400 years. Kepler's theorem, the truth of which is
obvious, proved to be a really tough nut to crack.
In 1998 Thomas Hales announced that he has proved Kepler's theorem, but the mathematical community at large
is still checking if he is really right.
This is perhaps a bit embarrassing for the mathematicians but we, being reasonable and practical people, know forsure that there is no better arrangement. We are thus not surprised that the two kinds of close-packed crystals asshown above - fcc and hcp - are the preferred crystal lattices for roughly two thirds of our common metals.
Now you know how a lot of metals condense into a crystal. How about the remaining third?
The rest, including iron, turns out to be a bit touchier about the number of close neighbors they like to have.
They feel that having 12 close neighbors like the fcc and hcp metals is a bit vulgar. They prefer to be a bit lesscrowded and go with just 8 next neighbors.

Iron, Steel and Swords script - Page 75

4.2.2 Being Iron
Again: About 30 % of all the metals, including iron, do not want to be close packed. They feel that having 12 close
neighbors like the vulgar fcc and hcp metals is a bit too much; 8 should be good enough.
Why ? You know as soon as you know the true name of those atoms. This is secret, of course, so all I can say is thatthose atoms attract other atoms in all directions too, but somewhat more in 8 special directions
How can we take that into account when we start stacking balls once more?
It's easy: Just start with packing your oranges squarely on the bottom layer instead of hexagonally. What you getthen is what we call a "body centered cubic" crystal lattice, or bcc for short, as shown below. Why this type of
crystal lattice is called "body centered" is obvious if you look at the right-hand figure. You also see that the special
bonding directions are not in the plane where we do square packing but in the diagonals.

The body centered cubic (bcc) crystal
How we stack the atoms
when we make an ironcrystal.

The resulting bodycentered cubic (bcc)
crystal lattice. The redlines show the preferredbonding directions.

We now covered attractions in all directions, giving close-packed element crystals and attractions in all directions butwith some preferences in special directions, giving (among others) the bcc structure from above. If, just for the hell of it,
we look at the other extreme of attraction only in some special directions, we get, for example, the diamond structure,
the favored structure of most semiconductors. Once more, there is no choice but to form a crystal when those atoms
get together.
Now we have three basic crystal lattice types, and if you find that confusing, consider that there are actually fourteen
fundamentally different lattice types or Bravais lattices.
You better believe me on this; I in turn believe Auguste Bravais who proved that in 1849. Figuring it out by yourself isquite tedious and involves the hated "new math".
So far I have avoided to explain the subtle but essential difference between theterms "lattice" and "crystal" but now we need to give this topic a quick look. The
science link gives in-depth information, this link will just illustrate and enlarge on
what is following here.
A lattice is a mathematical concept, a repetitive sequence of points in space. A
crystal results when you put atoms on those lattice points. You always can put asingle atom at the lattice points of one of those 14 lattice types, than you get anelement crystal. But nobody keeps you from putting more complex objects likemolecules there, however. Take water (H2O) molecules and you make an ice
crystal, for example.

Science
Link
Lattices,
Crystals

Considering that you could put your water molecule on some lattice point with the oxygen up or with the hydrogenup, and that there might be other ways as well, you now realize that there are altogether exactly 230 possibilities tomake different basic arrangements of entities like molecules on the lattice points of the 14 basic lattices.
Haha - just joking. I'm rather sure that you could not figure out that number. I certainly couldn't; at least not off-hand.
I can, however, look it up and check if the good people who are into this, got it right. They did. Just believe me. Use
this link to de-confuse you a bit if you think that's indicated.
If you look at little deeper, and I don't recommend it, even more possibilities emerge that you definitely don't want toknow about. It just serves to show how tremendous complexity—a DNA crystal, a sword blade, a car body—canemerge from a few very simple principle.

Iron, Steel and Swords script - Page 76

Mineralogists know all about Bravais lattices and so on, and they like to talk about it. So you should avoid them atparties if you're not into symmetries , point groups, space groups , sets, intersection of sets, and more stuff fromthe "New Math" that you hated so much way back in high school.
And no, it's not almost all the same. If you look at the table below, where some metals and their lattice types are listed,
and compare this to the older list of metals where I differentiated between always ductile behavior, always rather brittle
behavior, or in-between behavior with a brittle-to-ductile transition, you realize that the more ductile metals are fcc, themore brittle ones are hcp, and the bcc metals are in between.
Do you feel that we are getting closer to some answers? Well, we do, but we also come up with new big questions:

Why do metals crystallize in
different lattice types?
Why does this happen even for metals that are quite similar in all other aspects like nickel (Ni; fcc) and cobalt (Co;hcp)? If you read on for quite a while, you are eventually going to find out.
Right now let's make a little list of the lattice types that the more prominent metals and elements like to crystallize into.
However, first I must give you a few hints about how to "read" figures like the ones coming up:
The figures show lattices or crystals. The little blue spheres in the figures may represent lattice points in space oratoms. Since true mathematical points are infinitely small and atoms extremely small, the real things are simply not
visible and we need to represent them by some symbol - a circle for example. It is then up to you how you interpretthe symbol.
The lines are only there to guide the eye so it can see the spatial relation of the points that form the lattice. Sorry,
we can't do better. If I would draw real (tiny) points for the lattice and no lines, you just wouldn't see much; checkhere .
A crystal results if you put atoms on lattice points! If you symbolize atoms by circles, the resulting crystal figures
looks just like the lattice figures but is showing something entirely different! More about how to "read" figures likethat in this link

Lattice: fcc
Crystal: fcc, elementary, closepacked
12 next neighbors

Lattice: bcc
Crystal: bcc, elementary

Ag (silver)
Au (gold)
Al (aluminum)Cu (copper)
Si (silicon)
Ge (germanium)
Co (cobalt)
Fe (iron)Mn (manganese)
Sr (strontium)
C (carbon)

Fe (iron)
Cr (chromium)
W (tungsten)
Ta (tantalum)
Mn (manganese)
Ti (titanium)
Zr (zirconium)
Sr (strontium)

8 next neighbors

Lattice: hex
Crystal: hcp, elementary, close
packed.
12 next neighbors
Cd (cadmium)Co (cobalt)
Mg (magnesium)Ti (titanium)
Zn (Zinc)Zr (zirconium)
C (carbon)

Lattice types / crystal structure of common metals
and some other common elements
Blue circles = atoms and lattice points. Pink circles = atoms only (two atome per lattice point). Note that ahexagonal close-packed (hcp) crystal results only when you put the "pink" atoms in positions where there are no
lattice points. This is deceiving. You are actually putting an ensemble of 2 atoms onto 1 lattice point. Details canbe found here.

Iron, Steel and Swords script - Page 77

Surprise! Some metals (and many elements not listed) come in more than one crystal type— in the table they are
identified by col or. The big word for that is "allotropy " (of course from the old Greek, meaning changing, different
kinds, growing into something else). Those crystals then are "allotropic".
How come?
Before I answer this question, I first need to point out that it is primarily the temperature that determines whatcrystal type you will find. The pressure is also important. Carbon provides for a good example of this: a diamond
forms from graphite at high pressure (and temperature).
Pure iron switches from a bcc structure to an fcc structure at 912 oC (1674 oF) and back again to bcc at 1394 oC(2541 oF), while Cu or Au stick to their fcc structure at all temperatures.
Cobalt (Co), manganese (Mn), titanium (Ti), and so forth also undergo some kind of phase change (also calledphase transition) from one lattice kind to another one, if you change the temperature.
Of course, you now need to vent a big question: "How do you know all that! Afterall, you can't possibly look at the atomic structure of some metal at very hightemperatures with an electron microscope. Not to mention that all of this was
known long before electron microscopes even existed".
True. You are absolutely right. Even today we do not investigate the basic
crystalline structure of materials with an electron microscope. We use interference
effects of X- rays.
If you have seen a CD or DVD producing a spectrum of colors whenever you shine
some bright light on, you have seen so-called interference effects.

Science
Link
X-ray
diffraction

The regular array of tiny grooves on the disc interferes with the light to produce rainbow colors. Come to think of it,
water droplets interfere with light to cause a rainbow. There - you have seen interference effects!
The regular array of atoms in a crystal does exactly the same thing with X-rays that the regular array of tiny grooves
on a DVD does with light. Shine an X-ray beam onto a crystal and it will produce phenomena akin to what produces
all kinds of "rainbows" with visible light. Recording that with proper detectors and throwing a lot of math at the data
allows to compute the structure of a crystal in minute details.
This is called X-ray diffraction. X-ray diffraction machines are a kind of mathematical microscope. They do not
produce some direct picture of the crystal, just abstract data - numbers - about the crystal. The science module will
give details.
But back to the phase changes that we just learned about. The phase change of carbon from diamond to graphite,come to think of it, is simply a change from carbon atoms arranged in a fcc (diamond) lattice to carbon atoms arranged
in an hex (graphite) lattice. The illustration link shows details.

Illustr.
Link
CarbonphasesNobody doubts anymore that diamonds andgraphite are just two different phases of carbon
and not different elements / compounds / atoms
or whatever!
Our forebears, however, had a hard time to figureout that a diamond is just graphite in disguise.
Can you imagine a claim harder to believe? Will
your wife believe it? That her diamonds are soot in
drag?

Misc.
Link
History
carbon

It was not before 1772 that Antoine Lavoisier showed that the only product of the combustion (= burning) of diamonds
was carbon dioxide (CO2), proving that diamonds consist of carbon and nothing else. The story of figuring that out isinteresting enough to rate it's own module.
Of course, nobody believed this kind of nonsense right away. Since Lavoisier committed other grave errors ofjudgement, like intervening on behalf of a number of foreign-born scientists including the (now extremely famous)
mathematician Joseph Louis Lagrange, he was tried, convicted, and guillotined on 8 May 1794 in Paris at the ageof 50.
Appeals to spare his life, so that he could continue his important experiments, was cut short by the judge: "La
République n'a pas besoin de savants ni de chimistes; le cours de la justice ne peut être suspendu." ("The Republic
needs neither scientists nor chemists; the course of justice cannot be delayed") is the infamous quote that goeswith it. There are reasons why scientists are not all that fond of lawyers.
To be sure, in our enlightened age something like that can't happen, our modern lawyers will see to that. All thosescientists (and artists, almost same thing) who in many countries are spending time in jail right now are there forgood reasons, we must assume.
Change the lattice type and you change diamond to graphite. We have exactly the same thing for fcc and bcc iron! The
bcc room temperature phase (named ferrite, by the way) is quite different from the high temperature fcc phase (named
austenite), as far as properties are concerned. You are not aware of that because fcc iron only exists at hightemperatures and then everything looks the same (glowing yellow-red) anyway. But properties are very different. Ask asmith.
But you don't have to ask, you know that. You have witnessed the dire consequences of that phase transition taking
place. When the steel in the World Trade Centers became so hot that the transition from tough bcc-phase steel to
weak fcc-phase steel took place, disaster was unavoidable.
Iron, Steel and Swords script - Page 78

On the other hand, the bcc-fcc phase transition is one of the several reasons why iron is such a wonderful material.
When the sword smith heats up his iron or steel, he makes good use of the phase transition bcc-fcc in iron, as we willsee
We have come to a point where I can't weasel around the really big "why " question anymore.

Why do things happen the way they happen?
What is the guiding principle? I only consider "things to happen" in the inanimate world, of course, since you
already know some of the guiding principles in the animated world. For example, when your wife asks if she shouldwear costume A or B to some function, the guiding principle for the ensuing discussion is: You can't win! Never.
Ever.

Iron, Steel and Swords script - Page 79

4.3 The Second Law

4.3.1 Nirvana for Crystals
Peter W. Atkins, a well-known textbook and public science writer, has put it this way: "When you first encounter the
SECOND LAW, you ought to kneel down and worship".
He is right, up to a point. Since I'm a cool and tolerant guy, I let you keep worshiping whatever deity or deities you
presently like best. I only request that you should now ponder the essential "why" question:

WHY do metals come inthree lattice types,
and why do some change their typeif you make them hot, while others don't?

You may ask your deity of choice for an answer, or go for my answer, which is: it's all in the second law ofthermodynamics or second law, for short.
Now, if there is a second law, there ought to be a first one. There is a first law of thermodynamics, indeed. I've
already covered it.
The first law simply states that energy is conserved, and that heat is a form of energy.
It's nothing but the good old energy conservation law, just including heat as a form of energy.
For example, the first law states that you can't get more mechanical energy out of your car engine than you put
chemical energy in (in the form of the bonding energy of gasoline and oxygen).
In colloquial terms the first law states that you can't win forever, that somebody always looses if you win.
This is depressing, especially if you are the loser; sometime also known as tax payer or believer of financial gurus.
It is essentially the same as saying that there is no such thing as a free lunch, and we already know that as the firstlaw of economics.
The second law makes things even worse. It says that you can't even get all the energy contained in your gasolinetransformed into mechanical energy; it will always be less.
Quite a lot less, in fact. For example, if your car engine transforms just 50 % of the energy contained in the fuel toforward motion, it's doing extremely well.
In colloquial terms, while the first law says that you can't win on the long run; the second law states that you can'teven break even.
In other words: there is not only no free lunch, you don't even get your somebodies money's worth. Some of what
you invest is always funneled off and dissipated. In physics we call it entropy, in normal life we call it taxes (orrelatives, banks, governments, ...).
The first and second law can be expressed in many smart quips but—far more important—also in precise equations.
With the first and second law you can calculate precisely what can be achieved with all kindsof machinery where energy is jiggled around—steam engines of old, your car engine, airplaneturbines, an electric generator. Provided, of course, you know your calculus, including partial
differential equations, and so on.
And what, you might ask a bit piqued, does all that have to do with our "why" question fromabove?

Science
Link
Second law

Well - everything! Let's formulate the second law in a way where we can use it—but still without equations. I
promised.

Iron, Steel and Swords script - Page 80

Every system (like a large bunchof atoms), if left to its own devices,
will strive to assume a most stable statethat is a compromise between
keeping the energy low
and being disorderely

If the system ever achieves this most stable and most preferred state, and most of the time it will not, it will not "do"anything anymore, it just "is".
This is very easy to understand. If you (the system or you, personally) actually do something, things must change.
If they don't, you might as well have spared yourself the bother.
So if you do something while you are already in the best possible state you can be in, you can only change it to aless desirable state, so you better stop doing altogether.
If you are not in this best-of-all-state, then you do whatever it takes to get there.
This best-of-all-states is known among connoisseurs as: "absolute minimum of the "free enthalpy", or"thermodynamic equilibrium ".
I thought you should have seen those fancy words at least once. I will give this "absolute minimum and so on" statea better name here. I call this best-of-all states, where everything is peaceful and nothing changes anymore, by itstrue name:

Nirvana

Nirvana will be obtained if you keep your energy as low as sensible at all temperatures while allowing for increasing
disorder as the temperature rises.
Now I have connected two magic words that make for real (as opposed to magical) swords:
Niravana, the best-of-all states or arrangements the atoms will want to assume, andTemperature, the agent of change.
The rule is, and I want you to read that out loud:The hotter the system,
the more it needs to be disorderedto achieve nirvana.

If you are a male of our species, you recognize fun when you see it. Fun is often tied to disorder, here is an example:

Iron, Steel and Swords script - Page 81

Very orderly array offolks.
Some fun to watch,very little fun toparticipate in(especially if you are
not a North Korean).

Rather disorderly
array of folks.
Good fun to watch,
great fun toparticipate.

The general relations between fun and oderlinessIf you are a male of our species, you recognize fun when you see it, but not necessarily disorder—in contrast to yourwife. However, since we want to be precise, we won't rely on your wife. We must now find a way to measure disorder,
not just talk about it in so many words.
Measuring something always means to assign a number to whatever you measure. If you have numbers you can do
calculations. If you have natural laws (like the second law) in the form of equations and some numbers, you can doscience. If you can do science you need not consult crystal spheres or (worse) consultants if you want to find out
what will happen.
Being able to assess disorder by numbers is quite useful in other contexts, too. For example in computer science,
not to mention in everyday life ("Paris, your room today is 4,7 time more disorderly than yesterday, when it was at a
16,3 level. Clean up at least to a disorder level of 5! That means you must cast out two used lovers and you must
put your used underwear in the hamper").
Measuring and calculating disorder is actually rather easy, provided you like to wallow inmathematical things like logarithms, factorials, combinatorics and some calculus. Just look up
the science module or ask your friendly physicist down the block to see how it is done.
She will tell you to use one of the famous fundamental equations of statistical
thermodynamics that goes back to one of the big if unknown heroes of physics: Ludwig
Boltzmann (1844 - 1906). We will get back to him later again, but here is his grave stone forstarters:

ScienceLink
2nd Law

Boltzmann's grave stone in the famous Vienna"Zentralfriedhof"(central cemetery)S, by the way, is short-hand for entropy, k for
Boltzmann's constant
and w for the probability of a state.
You must admit that I kept my promise of "no equations" here. Boltzmann never promised anything like that.
For the special kind of disorder that we find in crystals and that we can calculate and measure precisely, we will now
use a different word, and that word isIron, Steel and Swords script - Page 82

Entropy =measure (in numbers) of disorder.
If that sounds Greek to you, that's because it is: "Tropae" means "metamorphism" or "transformation", and that is what
entropy does: it forces things to change, sometimes rather suddenly.
Entropy, for reasons even I don't know, is always abbreviated with the capital letter "S" inequations or otherwise, and I will use that abbreviation every now and then in what comes up.
Like right now, because we need to be a bit more precise about that compromise between
low energy and high disorder, the way you must balance the two for achieving nirvana.
Without using equations, here is what you do: multiply the number that tells you how
disorderly things are (the entropy S) by the absolute temperature T as measured in degrees
Kelvin (K).
What you get is the product TS, a number, and that's the quantity you balance against theenergy (another number).

Science
Link
Entropy

Balancing is simple: You subtract the number TS from the number giving the energy. The resulting number is yourcomfort account (measured in terms of energy). In contrast to your investment account (measured in terms of in
Dollars), you want your comfort account to be small. If it is as small as possible under the prevailing circumstances
you have achieved nirvana. See it like your tax account. The smaller the better.
By the way, it's easy to convert Centigrade to Kelvin: just add 273 to whatever oC temperature you have in order toobtain the absolute temperature. Room temperature is about 21 oC; on the absolute scale we thus have 21 + 273=294
Kelvin (K).
Being magnanimous about details, we take 300 K to give room temperature.
If you like Fahrenheit best, you figure out the conversion to Kelvin yourself. That's the proper punishment for weird
tastes. This link may help.
So once more: T times S is the number that you balance against whatever number describes the energy of yoursystem.
While that looks easy it is, in fact, a bit tricky. If the energy would be constant, all you have to do is to create asmuch disorder as possible to achieve nirvana. However, generating disorder and thus a large S may cost you interms of energy.
Your problem thus is to figure out just how much investment in some additional energy will give you the best returnin terms of TS. If you do it right (don't let investment bankers help you), you will achieve nirvana.
Let's look at a simple example. If your present state is described by having an energy of 12 and a TS of 4, yourbalance is 12 - 4=8. If an investment of 3 in terms of additional energy buys an additional TS of 5, your balance isnow (12 + 3) - (4 + 5)=6. You are then better off to raise your energy because the return on that investment gets you
closer to nirvana.
For iron and steel crystals, the only systems we are interested in here, low energy means perfect order. Then you havethe maximum energy gain by bonding to as many neighbors as possible. Energy gain means that the energy goes outof the system (think about the bonding of hydrogen and oxygen described before), and that's why the system energy
goes down and becomes smaller.
Perfect order means that the entropy S is zero and therefore TS is also zero.
For an iron crystal or better, for any crystal, you simply can't have low energy and a lot of disorder at the same time.
We need to compromise. Invest some additional energy and reap the benefits in a sizeable TS. If a certain
investment in energy (say 3 units) buys a certain S (say 5 units), then the best return on investment obviously
occurs at high temperature T .
Congratulations! Now you suddenly understand why things melt at high temperature. And you understand why themelting point always goes down when you alloy a pure element with something else, as already claimed in chapter
2.3.1.
Or do you?
Well, things melt because at the melting point it "pays" to invest heavily into entropy, to make things far moredisordered. Atoms milling around in a liquid are certainly far less orderly than being nicely kept at fixed crystal
positions.
It always takes a lot of energy (the melting energy or heat of melting) to turn a crystal into a liquid; it is a big
investment. You must, after all, take all the atoms apart. At the melting point the product of temperature T andentropy S exactly balances the melting energy; for temperatures higher than the melting point it thus pays to beliquid. TS is then larger than the energy investment.
If you go the other way around, it works the other way around. Upon freezing or solidification, things get far moreorderly and you loose out on the TS term. For that you gain energy, the heat of solidification.

Iron, Steel and Swords script - Page 83

So when you melt something, you must invest energy. That's everyday experience. You know that because things
don't melt all of a sudden. You have to keep heating (investing energy) your frozen dinner quite a while before it is nolonger solid.
Contrariwise, when you freeze something, you release energy—exactly the same amount it took to liquefy it. That's
why it takes a while to make ice cubes from water. The energy released when the first part freezes heats up thewater again and you need to take that energy away. That's all your refrigerator / freezer does: sucking out theenergy released when things cool down or freeze.
Why does the melting point always come down if we alloy our material with something else? Put some salt into waterand it is still liquid somewhat below 0 oC (32 oF).
Easy. If the crystal is alloyed with something, it is automatically more disorderly than in its pure state (all these
foreign atoms not fitting in properly, loitering around at random). S is always larger for a dirty crystal than for thepure state. So the product TS now balances the not much changed melting energy already at lower temperatures.

The melting point of any mix of atoms
with a little bit of B in A
always comes down because theentropy is always larger for the mix.

That is important! Adding a little bit of something (like carbon to iron) makes the system always more disorderly andthus increases the entropy.
Now we start to get somewhere. This is the precise moment where we can start to look seriously into the big "why "question:Why does adding a little bit of something
to iron produces a material with radically changed properties called"steel"?

Iron, Steel and Swords script - Page 84

4.4 Inside a Perfect Crystal

4.4.1 Perfect Crystals and the Second Law
Let's take a hypothetical perfect iron crystal (a brain crystal, in other words), or just any perfect crystal, for finding out
what crystals will do when you heat them up.
No real iron crystal will ever come close to being perfect, but the silicon crystals grown for microelectronics actuallyare not so bad. Whatever, it's no problem for us here. We work with a "brain-and-paper crystal" and it's ridiculously
easy to keep those perfect.
First we look at our crystal at very low temperatures, close to absolute zero (=0 K). It's not so easy to do this in reality
but it's no real problem either if you have the right equipment.
Disorder then hardly counts for achieving niravana. Whatever disorder or entropy S you have, the product TS at verysmall temperatures close to zero is always very small; for T=0 K it would be zero, no matter how large S would be
So coughing up some energy to produce disorder doesn't make any sense when it's really cold. The return on thatinvestment cannot be large. It is thus clear that whenever it's very cold, you thrive for perfect order as shown on theleft in the (schematic!) figure below.

Law and order for crystals
Schematic drawing of aperfect crystal at very low
temperature. Perfect order,
with atoms sitting (almost)still.

Same crystal at hightemperature. Atoms arevibrating wildly (hard todraw) and two vacancies
have formed.

Now we increase the temperature a little bit. What is our crystal to do?
To answer that question, we first have to answer that particular question that kept nagging you subconsciously all
this time, giving wild dreams about hot things and keeping you from sleeping well:What, exactly, is TEMPERATURE ?
You think that is an easy question? You think that any idiot can tell the difference between hot and cold water, or a hot
and cold day? Allright. Tell me about it!
Aha. Hot water is hot because you burn your fingers when you stick them in. And it's a cold day when your a..
freezes off, and hot day when you get a sunburn.
Fine, but how can your a.. tell that it's freezing? And I hope you will excuse my saying so, but science doesn't givea fart about how your fingers or your a.. feels about temperature.
Considering that you consist mostly of water (and some beer and red wine in my case) the question is: how do thewater molecules in your a.. know that it's cold enough to start freezing?
Remember, all we have so far are atoms, molecules, crystals and whatever else you can make from atoms, plus
photons (the particles of light), and the first and second law.
Maybe there is something like a "temperature particle"? Let's call it phlogiston (ancient Greek of course;
phlogistón="burning up"), so we have a name and feel better about it. Having invented phlogiston makes things
simple: shove some phlogiston around and things get hotter or colder. You could also call it "caloric" and assume itis an element like carbon, if that makes you feel better. The eminent Antoine Lavoisier, the "father of modern
chemistry", did that in 1789, not all that long ago.
Tough luck! There is no phlogiston, or caloricum, or any substance of heat—notwithstanding the fact that a largepart of humankind believed that for quite some time; use the links for details. Atoms, molecules, crystals andwhatever else you can make from atoms, plus photons (the particles of light) is the complete list. No phlogiston,caloricum, heatstuff or whatever.

Iron, Steel and Swords script - Page 85

Looking at a perfect crystal you see atoms, and nothing but atoms! The question then must be: What is different in thearrangement of atoms at low and high temperature? The arrangement is the only thing that could be different!
Please commit to memory:

Temperature is just another word for"average energy contained in the
random movementof elementary things
like atoms or molecules".
Let's whip out your brain microscope and give the air around you a close look. Ready? Then you should see a lot of
nitrogen and oxygen molecules (N2 and O2, respectively) flitting around at high speed and bumping into each other all
the time.
The animated figure below shows schematically at very high magification (around 10.000.000×) and inv e r y s l o w motion what you are supposed to see:

The air as seen with your brain microscope
Colors are only used to make it easier for you to keep
track of some particle. In real air the spheres would be(elongated) oxygen or nitrogen molecules, there would
be far more of them then shown here, they move on
average with the speedof sound, and they would movein three dimensions.
Source: English Wikipedia, author A. Greg

The molecules bump into each other (and into the atoms of the wall) all the time, and that makes their motion rather
random. Their total energy then is just the average kinetic energy of one molecule times the number of molecules.
Their average kinetic energy, of course, is determined by their mass and average speed squared.
The average random energy of those atoms or molecules is exactly what we call the temperature of the gas, it justhappens to be measured on a different scale for historical reasons.
Note that the gas molecules in your car, traveling along with you at whatever speed you are driving at, also havesome additional kinetic energy because of the car motion. This is, however, not a random motion. All molecules
travel with the same speed you are traveling with on top of their random motion—and this does not count!
We can measure this kind of energy in "Kelvin" (we never say "degree Kelvin, by the way), "degree Celsius", "degree
Fahrenheit", or whatever temperature scale you prefer. The numbers are quite different but it is always the same energy.
This might be a bit confusing but it is nothing new.
You can measure your wealth in Dollars, Pounds, Euro, or the number of Ferraris it can buy. You will produce quite
different numbers for each scale, but it is the same wealth and you can always switch from one number into theother one.
Converting energy measured in barrels of oil, British thermal units (btu) Joules (J), kilowatt-hours (kWh), electron
volts (eV), or temperature (T) produces quite different numbers too, but it is the same energy and you I can easily
convert from one unit to another one. It's just as easy as switching from one currency to another one, with theadditional advantage that the exchange rates never change.
By the way, how fast on average are the molecules of air at room temperature? What's your guess? Faster or slower
than your Ferrari at top speed?

Guess! Do try!
Iron, Steel and Swords script - Page 86

Here is the answer: they run around with the speed of sound, about 330 m/s.
It can't be otherwise because sound is a local disturbance in the running–around pattern of the gas molecules, andthis disturbance cannot possible mover faster than its parts, the air molecules.
Now whip out your brain microscope once more and look at molten steel . At the magnification required this can actually
only be done with a brain microscope. It will be rather hot work so, for starters, let's look at a more convenient liquid likewater at room temperature. Beer or red wine is just as good, if that helps your looking.
What are you going to see?
Water molecules in liquid water are flitting around randomly and bumping into each other all the time! The bumping
into each other makes their motion random, and so on. Schematically it looks exactly as in the animation above.
The animation above could also be used to schematically illustrate water vapor , a gas. It is pretty much fine for all
liquids and gases.
So what is the difference between a liquid like water and a gas like water vapor?
In a liquid the atoms or molecules are closer together and still stick to each other a bit. If given more room, theywould not thin out like water vapor or any gas but still occupy the same volume. Nevertheless they move aroundfreely but always feel some attraction to the other guys, not unlike people at a party in a crowded room. They movearound freely but also stick together.
If we extend the analogy from a a party to a crowded movie theatre where people sit on the same chair all the time,
we changed from liquid to a crystal. Nobody is running around, everybody, including you, sits at a fixed position.
All you can do is to wiggle around that position a bit. Only people with a vacancy (=unoccupied seat) next to themcan move—one place at a time.
Now back to our perfect crystal. In contrast to gases or liquids, the crystal atoms cannot move around to acquire someof the energy we call temperature. All they can do is to wiggle around their position. They do that very quickly so we
don't call it "wiggle" but oscillating or vibrating . Those atoms or molecules thus oscillate around their proper position abit.
The maximal deviation from their position at rest we call amplitude. The rest is easy:
Low temperatures=small amplitudes.
High temperatures=large amplitudes.
Oscillations or vibrations are hard to draw. I did the best I could in the figures here and there. What we can see,however, is that the hot crystal above, with its atoms oscillating wildly, would look a lot less orderly than the cold
one next to it—even if there weren't any vacancies.
Vibrations of the atoms evidently induce disorder or, as we agreed to say, entropy .
Here we have the full answer to the question from (far) above! When we raise the temperature, the energy goes up,
yes - but so does the entropy. At the raised temperature we can always find a proper balance of energy and entropy
and achieve nirwana again. Everybody is happy.
Now we get our crystal going and raise the temperature a lot. We give more thermal energy to the crystal, to introduce
a new buzz word.
The atoms now must vibrate wildly, with large amplitudes, and that is part of the reason why the crystal becomes a
bit larger by thermal expansion.
Entropy increases too, but not enough for nirvana purposes. There is only that much disorder you can make bykeeping things not exactly at their proper place but always nearby. Think of your spice rack. Not having the spices
in alphabetical order but still on the rack produces some disorder or entropy. Allowing some spice containers to be
off the rack for good (they might now be in the refrigerator, the underwear drawer, or God knows where; it doesn't
matter) offers far more possibilities for making things messy.
In very hot crystals we need more massive disorder for achieving nirvana than we can make with vibrations, and for that
we have to misplace things.
The only things we can misplace are the atoms; we have nothing else. So let's misplace atoms and create
vacancies—it was done already in the figure above. I have misplaced two atoms. They are gone, no longer with us.
They might now be in the refrigerator, the underwear drawer, or God knows where; it doesn't matter. In their place
we now have our first crystal defect, the vacancy. We are going to become very familiar with these little nothings
because they are important for sword making.
Since we cannot really loose atoms completely, you might wonder were they really are now. Well, consider for thetime being that they went to that mysterious place where the missing single socks go. Like those socks our atoms
have not really disappeared into thin air. Your wife could find your single socks for you, I could find the missing
atoms for you. I will eventually—but you don't need to care about that here; it is irrelevant for what I want to get
across here.
Our crystal looks really messy now and we have plenty of entropy. For making the vacancies, as we will call themissing atoms now, we had to invest some energy but as a return on the investment we got substantial entropy.
If we invest just right, we make exactly the right amount of vacancies to give the best balance between energy andentropy for the temperature we have chosen. We have achieved nirvana once more.
"What the hell", you might be inclined to yell out now. "Wen I drive around with my girl friend in search of a vacancy insome motel, I might care about vacancies. This here looks like some crazy little game for academically inclined
eggheads but certainly does not relate in some important way to my girl friend or to making a sword."
Iron, Steel and Swords script - Page 87

Well, you're wrong. Utterly wrong.
Without vacancies in crystals you would not drive in a car. You might not even exist, because Columbus would nothave discovered America. The likes of you would live in what we call the stone age.

Iron, Steel and Swords script - Page 88

4.4.2 Moving Atoms AroundWhy do vacancies relate in some important way to making a sword?
The answer is simplicity in itself! If we have vacancies, we have the "vehicles" that we need to move atoms .

At the particularinstance in time shown
here, the red atoms
happens to move to theleft while it oscillates,
and the two neighbors
to its left happen to
move up or down,
respectively, as
indicated by thearrows. The red atomthen can moveunhindered into thevacancy to its left.

The situation after the
red-marked atom has
jumped. The net result
is that an atom has
moved one atomic stepto the left, and thevacancy has moved
one atomic step to theright.

How atoms in a crystal move
Vacancies are extremely important since moving atoms is a big deal, just wait. The major reason why we heat up ouriron and steel a lot during sword making (or Si for making microchips, or most everything else for making mosteverything else; excluding babies), is the need to make vacancies so we can move atoms around.
It's a good bet than whenever a (crystalline) material is heated up to a temperature
higher than, let's say, half of its melting point (as measured in Kelvin), you do it
because you need vacancies. By heating you produce vacancies. It's unavoidable,
the second law will see to that.
My buddies and I, by the way, know exactly how many vacancies you will produce
in a given material at a given temperature.
It's quite easy to calculate (with a bit of calculus, logarithms and combinatorics,
involving factorials), the link shows how. Even so the math may look a bit involved,
it is about the most simple calculation you can do when invoking the second law
with Boltzmann's super-famous formula. Calculating vacancy concentrations is akind of paradigm for statistical thermodynamics.

Science
Link
Makingvacancies

Please look it up! Like Wagner's music1), it is better than it appears.
Now let's deal with that big "why" question you have on your mind:

Why do I need to move atoms aroundin order to make a sword?
(or a microprocessor?)
Because whatever you do to make something, you must change the way the atoms are arranged in your material. You
must rearrange the atoms in your crystal somehow, and for that you need to move atoms around.
If you don't move atoms around when you try to do something to your material, it is exactly what it was before you did
something to it—so why bother? That's so important that I will repeat it in huge letters:

Iron, Steel and Swords script - Page 89

If after some processing no atom has moved, then nothing haschanged!

If you think about that for a moment, you will realize that there aren't so many ways to move atoms around in a
crystal without invoking vacancies. Let's look at some options that may occur to you:
1. You can scrape some atoms off the surface of your steel (with a file, for example). The atoms inside then
won't even notice that something has happened. Well - yes, you can do that! And you don't need to invoke
vacancies for that. But you only changed the shape of a material by reducing its volume in this way, but notits properties.
2. You can bang your material with a hammer. The material will crack it if it is brittle or changes its shapewithout loosing volume if it is ductile.
Changing the shape of a crystal without changing the number of its atoms can only happen if some atoms
are now somewhere else. So plastic deformation is indeed the other major way to move atoms. We will see
presently how that is done without vacancies.
3. You might corrode your iron by throwing it in acid or just by letting nature takes its course. It will certainly
change. But that's once more doing things at the surfaces like in item 1, and we already covered that.
4. Then you could — Yes? Any suggestions? I bet you are at the end of your tether now because I am
(almost). If you find another way to move atoms around without using vacancies, let me know. I'm reallycurious. I will present your idea as my own and get the Nobel prize.
I'm going to assert that insight with a big green box:

Moving atoms in a crystal randomly
is done via vacancies !

Note the "randomly " in the statement above. Moving atoms via plastic deformation (No. 2 above), from the viewpointof the afflicted atoms, is not a jolly, free-spirited, hopping-around-at-random thing but an orderly and forceful process- and that's why we are going to call it "military movement" later on.
It is easy to see how the vacancy mechanism of atom movement works. One of the atoms bordering a vacancy jumps
into the empty space that is the vacancy, see the figure above, or the more schematic figure below. As a result, one
atom has moved and is now somewhere else, and so has the vacancy.
Which one of the neighboring atoms will jump into the vacancy, and when it's going to do this, is a purely statisticalor random event. Randomness always means that you can simulate what is going on by casting dies and following
some simple rules. For example, get a 12-sided die, make the rules like: 1 = atom on top moves, 2 = atoms on theupper left moves, …) and you now can cast a die to determine which one of the 12 neighbors to a vacancy in an fcc
or hcp crystal is going to jump. For a bcc element crystal you need a 8-sided die. Of course it is far easier andfaster to your program your computer to simulate those dies. Just utilize its "random number" generator.
Again, even so it gets a bit repetitive: we can calculate precisely what will happen on average. It's not called"statistical thermodynamics" just for fun; there is an awful lot of chance, randomness, and statistics involved. But"stochastics", to give it its proper name, is a precise mathematical discipline and we know precisely how often, on
average, atoms jump around in their crystal or, same thing, vacancies jump around in their crystal.
For example, in pure iron at 900 o C (1652 oF), just below the temperature where it turns into a bcc crystal, avacancy will jump about 100 million times per second, while at room temperature it essentially sits still . Thatmeans that at the high temperature about 100 million atoms per vacancy in there will be somewhere else after just
one second.
The whole process of atoms moving around randomly is called "diffusion". Diffusion happens naturally all the time inliquids and gases because there the atoms move randomly by definition. It is the reason why you might smell your
Beloved before you see him—the smell "molecules" just move or diffuse faster than he moves. But diffusion of gases or
liquids is not of much interest to us here.
Diffusion in crystals via vacancies is at the root of changing properties of solids, and that's what we are actually
discussing, remember?
Let's look at the importance of diffusion via vacancies in the light of modern technology. Let's make a microchip
and not a sword for a change.
The basic task is to take a perfect silicon (Si) crystal and to replace a few of its atoms (one out of 10 million, let'ssay) by Arsenic (As) atoms in a certain region. That's called "doping" the silicon, and doping is the process at thevery heart of microelectronics.
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How are you going to do this? You only can "go in" via the surface, so let's put some arsenic atoms on the surfaceof the silicon crystal. This is shown schematically on the right-hand side in the figure below; the arsenic atoms arecolored red.

Diffusion and the making of a chip
If you have some arsenic on the surface at room temperature, you're not getting anywhere. The arsenic atoms would besitting on the silicon surface forever, give or take a small eternity.
What you are going to do now is to produce some mobile vacancies as shown in the middle picture. For that you
must heat your silicon to a sufficiently large temperature (at least 800 oC (1472 o). In the picture we have generated
two vacancies. The vacancies move around at random because silicon atoms are jumping into them all the time.
Eventually, as shown in the middle figure, one vacancy happened to move next to an arsenic surface atom, giving ita chance to make a first jump into the silicon. And so on.
The picture on the right shows the two arsenic atoms now inside the crystal. Most of the time they are just sitting
there, waiting for vacancies to come by. If that happens, they might make another jump, always provided if they canbeat the silicon atoms that are competing for a jump into the vacancy. If they jump, they might make it deeper into
the crystal or back to the surface; it's all equally likely, after all.
This looks like some truly awkward process for going places. Well, it is—but it works. It works quite nicely, in fact.
Look into your silicon microprocessor with your brain microscope. The structures you will find inside the silicon are
far more complex then you could imagine in your wildest dreams - but they were produced mainly by this vacancy
diffusion process.
The vacancy diffusion process also works for iron. It is the cornerstone of iron and steel technology, and of any other"crystal changing" technology.
By the way, how fast do you think those atoms oscillate ? What's your guess?
Back-and-force a few hundred times per second like a tuning fork? A few thousand, million, billion, … times per second?
Well, you either know or you don't. You can't really guess that number intelligently. If you don't know it, you must dosome calculations. Since we don't do calculations here, I will tell you.
Those atoms are small and nimble; they actually oscillate with a frequency of about 1013 Hertz (Hz) or 1013 times
back and forth per second. In other words: 10 billion times per second in Europe, or 10 trillion times in the USA. By
the way, that's about 1 % of the frequency of light if you consider it to be an electromagnetic wave.
What that means is that all this jumping around can be quite fast. An atom next to a vacancy "tries" 10 trillion times
per second to move over to the vacancy position. So even if the probabilities for making that big jump are very low, it
still could happen rather often per second.
All in all, atoms can move around quite swiftly at high temperatures despite single jumps being very small (about 1
nm; remember?).
Let's summarize:
A perfect element crystal is an ordered assembly of one kind of atom (for example iron). Its lattice type (bcc
for iron at room temperature) is the one belonging to its "nirvana" state.
The atoms oscillate around their basic lattice position with a rather high frequency. The energy contained inthese oscillations we call "temperature ". When the temperature increases, the amplitude of the oscillations
increases.
Depending on temperature, a certain number of vacancies must also be present and their concentration
increases sharply (a better word is: exponentially) with increasing temperature.
Oscillating atoms and vacancies exist because the second law commands with absolute authority that byincreasing temperature, things must become more disorderly; the entropy must increase. And that is good!
Being perfect all the time is boring.
The vacancies can move around and that provides for movement of the atoms, something we call diffusion .
Diffusion is the key to processing crystalline materials.
Now read out loud to yourself:

Iron, Steel and Swords script - Page 91

If my steel changed - from soft to hard or the other way around,
whatever - the internal atomic structure must have changed.
This means: atoms must have moved. Diffusion via vacancies
provides one of the two ways to move atoms in a crystal.

So far, so good. But we still have a major why question open that has no obvious relation to vacancies and diffusion:

Why does pure iron change its
phase from a bcc crystal to an fcc crystal
at precisely 911 oC (1.672 oF)?
This question applies equally well to all elements that change their crystal structure upon heating (or cooling), forexample like Cobalt (Co), Strontium (Sr) and carbon (C) – look up the table with the list to find more.
We might ask just as well why elements like Ag (silver), Au (gold), Al (aluminum), Cu (copper), Si (silicon), and soon, do not change their structure at some temperature?
The answer is simple in principle. In practice it will provide work for generations of materials scientists to come. Here it
is: A crystal of any material can be considered to be an extremely powerful analog computer that at any instant in timeassesses the following items:
1. The present situation, including, for example, the actual temperature, pressure and the availability of foreign
atoms.
2. Its actual structure, including the actual crystal structure, the number of vacancies and other defects we willencounter later.
3. The balance between energy and entropy for the present situation and the actual structure.
4. The balance between energy and entropy for the present situation and any conceivable possible structure.
If one of the conceivable states is nirvanawise better than the actual state, the crystal implements all the measuresat its disposal to change its present state to that more desirable state. And that may be a different crystal structure
at some changed temperature.
Of course, the crystal does not really compute. It is mathematically just as challenged as your average banker orpolitician; it might just be a little bit ahead when it comes to large numbers.
The crystal just does whatever it does because every atom simply does what comes naturally, like an ant in ananthill. All the possible structures are continuously tried out on a very small scale. Some atoms just assume somestate, purely at random, and if it "feels good", it spreads. All possible states always "compete" with each other, andthe winner takes all.
Only if you look at the big picture with regard to crystals or ant colonies, something meaningful emerges that is not
visible on the atom or single ant level.
It's only us curious humans who have to go through an algorithm (in the form of a computer program) as outlined
above to figure out what is going on. The four-step procedure above is simple enough in principle but outrageously
difficult in detail. What are the possible potential structures? If challenged, you probably could come up with a
few—but rest assured that there are far more than you could imagine in your wildest (Material Science) dreams. The
link gives an example of what previously unimaginable wonders we have already encountered.
So, to answer the question, it just so happens that in iron, cobalt, and few other metals it is necessary to change thecrystal structure at some temperature for achieving nirvana, while for aluminum gold, and so on it's not.
Simply speaking, the crystal has one more trump card up his sleeve for balancing energy and entropy than justadjusting atomic vibration amplitudes and vacancy concentrations. It can also change its basic crystal lattice
structure. Doing that also changes vibrations and vacancy numbers. That makes it a bit difficult for us to compute ifchanging the basic structure, meaning to initiate a phase transition, would be a good move.
Now for the good news. Being engineers, we don't have to compute all that! The crystal, after all, can and will dothat for us. We just have to measure what it is doing by designing some suitable experiments.
What we will note already here is that the fcc phase that iron assumes at high temperatures is actually only a little
bit closer to nirvana than the bcc phase, while at low temperatures the bcc phase is a lot better than the fcc phase.
Come to think of it, we actually know about this already. Pretty much all crystals change their basic structure at a very
special temperature that we call melting point. This particular phase transition just looks more dramatic compared tochanging from one crystal lattice structure to another one, but in essence it is the same thing.
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If an element crystal undergoes one or more phase transitions before the final big one called melting, and at what
temperature this happens, we know from experiments. But not only did we measure it in great detail, we canactually (almost) calculate it. Essentially we know how to calculate it (see above), and we get good approximate
numbers. Getting precise numbers is still beyond our ken (but not for much longer) because you need to do
extremely tricky math and that's not only tough but needs more computing power than we command right now.
Not many elemental crystals undergo a phase change in the solid state, and very few do it more than once like iron.
Now you have a first indication why iron is just about the most complicated crystal among the major metals. Its bag oftricks for achieving nirvana is rather larger than that of most other crystals.
Iron is also magnetic in its bcc state—but not in its fcc state. This provides for a
few more tricky ways to play with energy and entropy. Being (ferro) magnetic is arare treat among elements. Only nickel (Ni) and cobalt (Co) are ferromagnetic, too! I
won't go into this here because it is not very important for sword making.
There is a science module about magnetism, however.
All things considered, iron is just a rather special material, already in its ideal form
as perfect "brain" crystal.

Science
Link
Magnetism

In reality, however, there is no such thing as a perfect iron crystal in a state of nirvana, utterly at peace with itself andthe world.
There are only real iron crystals out there, not brain crystals, and none of them can ever achieve perfect nirvana, justlike you and me. They only can get close. Their desire to get as close as possible is what makes things happen.
So we now need to look inside a real iron crystal and see what happens there.

1)"Wagner's music is better than it sounds", Mark Twain

Iron, Steel and Swords script - Page 93

5. Inside Real Crystals
5.1 A Close Look at Real Iron
5.1.1 Nobody is Perfect
5.1.2 The Defect Zoo

5.2.1 Point Defects
5.2.1 The Gang of Four5.2.2 Defects that Get Around

5.3 Two-Sided Defects and Bulky Things
5.3.1 Grain Boundaries
5.3.2 Phase Boundaries
5.3.3 Stacking Faults
5.3.4 Bulky Things and Nucleation

5.4 Weird Denizens of the Defect Zoo
5.4.1 The dislocation
5.4.2 Dislocation, Plastic Deformation and Hardness

5.5 Mixes
5.5.1 What's in a Name?

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5. Inside Real Crystals
5.1 A Close Look at Real Iron

5.1.1 Nobody is Perfect
Get a piece of real iron. Any iron or even "mild steel" (with just a little bit of carbon) will do. Cut off a piece of your car
body, or take a regular nail, etc., etc. Let's look at our piece of real iron once more.
Except that this time we do not crank up our brain microscope to the high magnification level where we see the ironatoms. Here we make do with magnifying just a few thousand to a few hundred-thousand times.
At that low magnification we will not see the atoms. The truth is that looking at atoms is only fun when you do it for
the first time, after that it tends to get a bit boring. All iron atoms not only look the same, they are exactly thesame. If you have seen one you have seen them all. Worse, most of the time they aren't doing anything exciting
either.
You simply won't notice a tree, not to mention a forest, if you only look closely at leaves. Watching only atoms inyour sample you may miss the action somewhere else in your specimen since you only watch an extremely tiny
part of it.
The total amount of material investigated at atomic resolution so far is less than one cubic millimeter (1 mm3 ) of
material, and electron microscopists started watching atoms around 1975. That's around the volume of a pinhead.
You agree, I hope, that they might have missed something.
What they tend to miss are lots of wonderful defects (more properly called crystal lattice defects) contained in theircrystals, because on an atomic scale they are so far apart that most of the time you miss them.
If you have one gold nugget per square meter (1 m2 equals about 10 sqf) in your claim, you will have to search along time if you comb the ground with a high-power microscope, seeing about (100 × 100) µm2 at one go. Covering
one 1 m2 means you have to search 100.000.000 of those patches, and that will take a while.
Electron microscopists are no fools, however. I used to be one, after all. They know that they are going to misssomething if they only work a high magnification. That's why they invented many other ways to look at a sample, andthat's what we are going to do now.
So crank down your magnification and look again. What are you going to see?
Not all that much that will excite you. There are two reasons for this:
1. First, most of the defects we are after are invisible. You need to use some little tricks to make them visible.
2. Second , even the ones you happen to see by accident don't have little labels attached saying, for example,"I'm a grain boundary", or "I'm an iron-carbide particle", so changes are that you don't recognize what you
see.
Without some background knowledge you might not notice that the grayish smear you see is actually something
exciting. I did not exaggerate when I mentioned that it takes at least 5 years of training (studying Materials Sciencean Engineering, for example) before you can start using an electron microscope and related equipment in a sensibleway.
So with a little help from me you are going to see defects now. Since the defects in the iron crystal turn iron into steel,and since those defects determine almost all the properties of steel, we now must delve into the systematics of defects
in crystals.
It's actually not that difficult, just a bit mind-boggling. Boggling the mind can be fun, for the boggler and the bogglee.
I suspect you do it routinely with a bottle of the good stuff, movies, soccer, football or other sports, not to mention
women. Now let's do it with defects.
Let's start by defining defects:

A defect is anything in the crystal
that destroys the ideal perfectionof the crystal locallyThat sounds a bit pompous in theory but is easy in reality. Just imagine that you are one of the atoms in a perfect ironcrystal. Have a glass or two of your good stuff and you should have no problem imagining to be an iron atom.
Iron, Steel and Swords script - Page 95

Now look around you. What you see in a perfect crystal are your next neighbors, eight other iron atoms in precisely
determined (average) positions. Those next neighbors are also you, by the way, since all iron atoms are exactly
alike. You and your neighbors flit back and forth at high speed because you vibrate if you feel warm so you only seeeach other as a fuzzy blur.

Being an iron atom
Now if you see anything different from that, it can only mean that a defect is present.
It's clear from that analogy that atoms find defects quite exciting. Defects break the monotony of hanging around all
the time with people exactly like yourself. It's the best possible company of course but it gets a bit boring at times.

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5.1.2 The Defect Zoo
There are a lot of different defects, we have a veritable zoo . There is also an easy way of sorting "defects in crystals"
into some meaningful categories.
We do that all the time with other things. For example, we like to differentiate the basic category "living beings" into
animals, plants, fungi, and so on; after that we differentiate "animals" into, for example, birds, lions, fish, slime
worms and bankers (however small the difference between the latter two might be).
With defects the simple and time-honored sorting principle is:
1. "Zero"-dimensional defects or "point defects".
These defects are very small in all three directions of space. As small as they can possibly be ("zero" dimension),and that means atomic dimensions.
Our old friend the vacancy is a good example of a zero-dimensional defect, and so is an interstitial carbon atom
in iron (we'll see in a moment what that means).
2. One-dimensional defects.
This means that along some (virtual) line running through the crystal, something is wrong. Atoms sitting on (or closeto) that line see an environment different from that of a perfect crystal.
There is only one basic kind of one-dimensional defect in existence, which we will call a "dislocation".
Dislocations do tend to boggle the mind quite a bit as soon as we give them a closer look, sorry. However, they areof prime importance. Read the following sentence loud to yourself or whoever you can force to listen to you:

Adjusting the properties of your steel
ultimately means that you
deal with the dislocations in there.
Now repeat it, just to make sure you got it.

Adjusting the properties of your steel
ultimately means that you
deal with the dislocations in there.
So if we want to get answers to our still open "why" questions, we must deal with dislocations. They are at the very
heart of the metal bending industry.
Sorry. There is no shortcut. You must turn on your brain.
3. Two-dimensional defects.
Something goes awry with your crystal on some (virtual) plane.
We already know one defect of this type; we just haven't thought about it in these terms: it's simply the surface.
Atoms there, if they look around, certainly do not see only proper neighbors in their proper positions.
Another two-dimensional defect easy to conceive is the good old grain boundary between two crystallites or grains
in a poly crystal.
4. Three-dimensional defects
They are easy to conceive. For example, just make a hole in your crystal by taking out many atoms. You don't
know how to do this without messing up the crystal? It's easy. There are two ways of doing it:
1. Make a lot of vacancies (you know how to do this: just make your crystal hot). Then see to it that they all
cluster together, forming a vacancy agglomerate that is simply a little hole, better known as a "void".
2. Take a magic knife or, better, brain knife that allows you to cut around in a crystal any way you like. Then
scoop out a hole. Rest assured that whatever you can imagine doing to a crystal with you brain knife, mothernature can and will do in reality. You simply need not worry about how it is done.
Working through that list is going to be our program for the next sub-chapter.
So gird you loins, fetch your favorite poison for relaxation, and beear with me.

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5.2.1 Point Defects

5.2.1 The Gang of FourWe start with zero-dimensional defects; the smallest denizens of the defect zoo. Here they are - all four of them:

The gang of four.
It's pretty simple. More than those four "point defects" we cannot make by playing with atoms inside an elemental
crystal, meaning a crystal made from just one of the elements like iron or silicon.
The question we need to answer now is "why " and "how many"?
Why should a crystal contain those defects and if there is some reason, how many should it be?
Well, we already know that any crystal can and will make vacancies because it needs to produce disorder to achieve
nirvana. If you glimpse ahead a little bit, you can see how the crystal makes vacancies.
For exactly the same reasons —creating increasing disorder with increasing temperature—it also can and will make"self-interstitials", atoms of its own kind that squeeze themselves into the interstices or interstitial positions in thelattice.
The first question thus finds an easy answer for two of the four point defects. We are left with figuring out how manyvacancies and self-interstitials we must have at some temperature.
Disorder is more important at high temperatures. This can only mean that the
number or the concentration of both vacancies and self-interstitials must increase
with increasing temperature. If you bothered to look at the science module about
vacancies, you know that the concentration increases exponentially . If you didn't,
you may want to check the "science" module to get some idea what "exponential
growth" means.
Just a hint: If you hate exponentials and logarithms but like money, you should
reconsider. It's those dreaded math objects that will tell you how your money will
go down the drain with the coming inflation (or through the roof if you invest it
wisely).

ScienceModuleExponentials;
logarithms

OK—for those of you who can't overcome their fear of math: Exponential growth of the vacancy concentration withtemperature means that the concentration goes up rapidly with temperature. Here is a calculated curve showing theapproximate vacancy concentration in iron as a function of temperature:

Approximate vacancy concentration in iron as function of(absolute) temperature. Tm=melting point.
In order to calculate curves like this one needs to know aparameter called "vacancy formation energy" that is not all thatwell known for iron. That's why there are two curves for the twovalues shown. The "real" curve is probably somewhere in between.
0.01 would be 1 %; 0.0001 is 1/100 of 1% or 100 ppm
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So, yes, the concentration is indistinguishable from zero over most of the temperature regime. Only at rather hightemperatures it goes up rapidly. That doesn't mean that there is nothing at lower temperature, you just can't see it inthis plot. If you plot the total earnings in your country versus time, your salary of 2.654 € (or of whatever you
currency might be) this July will simply not show either—even so it was very meaningful to you.
In the science module you can look up how to make better plots of vacancy concentration.
OK—now you know more about vacancies than you ever fancied in your wildest dreams. How about self-interstitials?
It is exactly the same thing. Self-interstitials do the same thing as vacancies: they introduce disorder and thus raise
the entropy. They just don't do it quite as well as vacancies in almost all common crystals.
Most crystals, including all metals, therefore prefer vacancies to self-interstitials by far, and only make a tiny
amount of self-interstitials that we can simply forget about.
Iron self–interstitials thus are completely unimportant to sword making and we won't mention them ever again(except in the science module).
The big exception, by the way, is Silicon (Si). In silicon crystals the self-interstitial is of major importance. How thatwas found out and drummed into the heads of the non-believers, would be a long story of its own. I'd love to tell it
because I had a hand in it. I will restrain myself here—but not in this link.
The vacancy and the self-interstitial are the two zero-dimensional defects that we subsume under "intrinsic point
defects" for obvious reasons. "Intrinsic" is one of those fancy Latin words we scientists like to use in order to show off.
It means "innate", or "incarnate" in the sense that the crystal needs nothing from the outside for making them—incontrast to the extrinsic (extraneous, foreign) point defects shown on the right in the figure above.
So let's look at the two extrinsic guys now, some foreign atom in an interstitial position, or some foreign atom at an
substitutional position.
We also call them impurity or dirt atoms, and sometimes doping atoms or alloying elements, I'll come back to that.
I know. Those names suck. If you can come up with better ones, let me know. And while you are at it, find betternames for other outlandish expressions like: democracy, republicans, maitre'de, caucus, anonymous,dermatologists or ophthalmologist, too. Or simply accept that it's not worth the bother to rename things that alreadyhave good working names, however weird. All our intrinsic / extrinsic / interstitial / substitutional stuff is reasonably
clear and you got to have some names, after all.
If you could live with things having names like "George Walker Bush", you shouldn't have a problem with dirt goingby the name "substitutional foreign atom" either.
As far as dirt is concerned, foremost on our mind is of course Berlusco carbon in iron. Carbon, it turns out, lives as
an extrinsic interstitial in between the iron atoms as long as it is "dissolved", meaning incorporated as a single
atom.
In silicon, carbon would be a substitutional foreign atom, replacing ("substituting") one of the silicon atoms, so it
depends on the host crystal which of the two possibilities a given foreign atom will assume.
Let's summarize:

Intrinsic point
defects

Extrinsic point
defects(impurity atoms,
doping atoms,
dirt, alloy
element...)Vacancy
Self-interstitial

Substitutional
atom

Interstitial atom

When we talk about carbon in iron, we usually consider concentrations between 0 % and 1,5 %. Those are always
weight percent (written wt % if you want to be precise) if not otherwise stated (remember?).
This makes a lot of sense in material engineering because you can easily makedesired mixes by weighing the ingredients.
In materials science , however, we look at atoms. In order to assess foreign atoms
in a host crystal, we need their concentration in atom percent (at %). In otherwords, we want to know how many percent of all the atoms present are carbon
atoms?
There is no easy way to switch from one to the other; consult the link for how it's
done.
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In materials science , however, we look at atoms. In order to assess foreign atoms
in a host crystal, we need their concentration in atom percent (at %). In otherwords, we want to know how many percent of all the atoms present are carbon
atoms?
There is no easy way to switch from one to the other; consult the link for how it's
done.

Basic link
Concentr.
wt%⇔ at%If we take, for example, the "magical" 6.7 wt % of carbon and express it in atom
percent, we get 6.7 wt %=25 at % . A quarter of all atoms then are carbon atoms.
Why 6.7 wt % of carbon of carbon is "magical" we will see later—but you arewelcome to make a guess, now that you know it corresponds to a mix of iron :carbon=3 : 1 in terms of atoms. Hint: one could write that Fe3C.
What a schematic iron crystal would look like with 1.75 at % (≈ 0.3 wt %) or 5 at % (≈1 wt %), respectively, of carbon
atoms dissolved in the volume of the iron, is schematically shown below.

Schematic view of some atomic plane inside aniron crystal with dissolved interstitial carbon
10 carbon atoms for 625 Fe 32 carbon atoms for 625 Fe
atoms
atoms
≈ 1.75 at % or ≈ 0.3 wt %≈ 5 at % or ≈ 1.1 wt %Blue dots symbolize iron atoms, red dots the carbon
atoms. The lattice is simple cubic for ease of drawing
and thus not correct—but the relation between thenumbers of atoms is about correct.
You are looking at a virtual cut through the crystal, of course, and at any plane inside the crystal it would look like this,just with the carbon atoms distributed at random at interstitial positions. We also call this "the carbon is dissolved " or it
is in solid solution.
Now why should that be virtual? I stated some time ago that there are special microscopes that allow you to look at thesurface with atomic resolution. Yes—but:
If we look at a real surface of almost anything you wouldn't see much because a real surface of almost all crystals in air
is oxidized . With an iron sample you always would look at "rust", even if to your eye it looks bright an shiny. An ironoxide layer just a few atoms thick, totally invisible to the eye, is all it takes to completely obscure a surface from atomic"view".
Even if we use the common (and expensive) technique of putting our sample in ultra-high vacuum (UHV) where it
can't oxidize, and "somehow" take off the original rust layer in there, we would still have a hard time seeing
anything! Why? Because iron is magnetic! That tends to mess up many microscopes, including the STM we would
need to employ here. I have therefore no iron surface pictures taken at atomic resolution that looks remotely like theschematic picture above. The best I can give you are pictures of point defects in a gallium arsenide (GaAs) surface.
Note that despite the rather small weight percent concentrations of about 0.3 wt% or 1 wt%, respectively, in the figures
above, it's actually quite a bit of carbon if you think about it. Nevertheless, most "bonding springs" still connect ironatoms and thus Young's modulus is hardly changed relative to that of pure iron.
Note that this not a theoretical prediction open to some doubt. This is as hard a fact as you like them to come.
Now that we have played around a bit with an extrinsic defect like carbon in iron, the same question as above for the
intrinsic defects comes up:
Why should a crystal contain those extrinsic defects, and if there is some reason, how many should it be?
In an ideal crystal world the answers to those questions would be exactly the same as for intrinsic point defects:
Extrinsic defects increase disorder, and a certain number of all the other 90 or so elements should be part ofany nirvana-seeking crystal.
The proper "nirvana" number of extrinsic defects depends, among other things, strongly on the temperature.
Generally, the concentration should increase with increasing temperature.
In an ideal world you would have the proper amount of money necessary for achieving your personal nirvana
conditions. But neither you nor the crystal exist in an ideal world. A crystal cannot make foreign atoms at will, justas (most of) us cannot print money all that easily.

Iron, Steel and Swords script - Page 100

So in the real crystal world, the answer to these questions is different from the one describing the ideal word. It isextremely simple but will have formidable consequences:

You got it, you keep it!
Tough luck. The number of any atoms forming extrinsic point defects—interstitial carbon in iron, substitutional
carbon in silicon, substitutional phosphorous in iron, ..., (the list here would contain about (90 · 90)=8.100 entries;
can you see why?)—is whatever it is. Mostly that number simply comes from the original process used for making
the material.
The crystal can neither make more foreign atoms or impurities if it wants too, nor can it easily get rid of the ones it
has. It needs a little bit of help from friends like you for this task
The consequences are dramatic:

If a crystal contains impurities in any
form, it can no longer achieveabsolute nirvana. Never. Ever.
Our steel blade or crystal with 0,5 wt% carbon in it, or just any crystal containing impurities, is stuck now. It wants tohave a certain precise number for nirvana but chances are extremely high that the number it actually has is far off thatnirvana number.
The crystal is stuck. What is it going to do?
Exactly what you would do if your 9 children are running all about the place, producing far more disorder thanneeded, and keeping you from achieving you preferred state of being (easy chair, peace and quiet, good wine, agood book like this one). You round 'em up and lock them into a room somewhere else. Crystals do the same thing;
they imprison their impurity atoms or, as it is properly called, precipitate them. We will see how that works shortly.
But before we do that I want to generalize a bit.
It should be clear that as far as extrinsic point defects go, we are not restricted to carbon. I can take whatever else theperiodic table has to offer (about 90 elements) and put it into my iron. I know how to do it in reality, for you it's an easy
thing to do in your brain lab.
Now let's look at how these impurities have settled in the iron. The good news is that the foreign atoms can assume
only three different configurations:
1. They could be dissolved as interstitial impurity atom. Then they are somehow wedged in between the regularatoms.
2. They could be dissolved as a substitutional impurity atoms. Then they "substitute", i.e. replace an iron atomin the crystal lattice.
3. Only a few are dissolved in one of the two possible ways and and the rest is securely put away in a
precipitate (I'll come to that shortly).
Let's look at few examples
Carbon (C), nitrogen (N), and hydrogen (H) are always dissolved as interstitial impurity atoms in iron.
Phosphorus (P), Sulfur (S), Manganese (Mn), Nickel (Ni), Chromium (Cr), Vanadium (V) and most otheratoms are always dissolved as substitutional impurity atoms in iron.
Oxygen (O) and boron (B) can be dissolved in both ways.
All of them will be imprisoned in precipitates if they exceed a certain specific concentration.
Which elements we have inside the iron crystal, how many, and in what kind of configuration determines most of theimportant properties of your steel.
So, without a little bit of help, the concentration of extrinsic point defects—impurities— in crystals won't change, incontrast to the intrinsic point defects that the crystals can make and dispose of on its own.
This is great because that's where you and I come in. If you know how to do it, you can change the impurity
concentration of a given crystal, no matter if the crystal likes it or not. That's where technology starts. Let's look at two
examples:Iron, Steel and Swords script - Page 101

Building a silicon microprocessor or most anything else from silicon (Si) needs tostart with a very clean and perfect silicon crystal, as close to nirvana as it can be.
This involves producing extremely clean liquid silicon first. In a second step analmost perfect crystal is grown by rather involved methods.
Then we mess up the crystal by putting substitutional impurities like phosphorous(P), arsenic (As), or boron (B) inside well defined parts of it.
So the concentration of extrinsic point defects does change: it goes up. The crystal
doesn't like it, of course, because that takes it rudely off his near-nirvana state ofbeing. It fights back in many ways, and it fights dirty! That is one of the reasons
why microelectronics technology is not a simple enterprise.

Advancedlink
Nirvana Si

When we make steel in modern times, we start with rather dirty liquid iron, it is actually cast-iron. We remove mostof the unwanted dirt already in the liquid state and we add some wanted dirt. Crystallization is not controlled on a
microscale so we get (huge) polycrystals. Certain processes in the solid crystalline state (like "case hardening") willchange the concentration of some impurities (mostly carbon) to some extent.
One last word to impurities in crystals. Without going into more details, one thing becomes clear: it is far easier tomess up a crystal then to keep it clean or to clean it up if its messy. It's not so difficult to get impurities inside.
Crystals, after all, like to have some at high temperatures. It is just far more difficult or well-nigh impossible to get themout again.
It is just the reverse of opening a can of worms, or squeezing tooth paste or your heir out of a tube. The problem
there is to get the stuff back in.

Iron, Steel and Swords script - Page 102

5.2.2 Defects that Get Around
Point defects are the easy-going defects in our defect zoo. They can move around in the crystal easily in contrast to thetwo and three-dimensional defects which are almost immobile and move rather slowly if at all. I've introduced you to thisalready in the preceding chapter. Here I'm gong to get serious about diffusion, as we called it.
Only one-dimensional defects or dislocations can also move around in a crystal, moving atoms in the process. They
do that in a way completely different from that of point defects, as we will see shortly.
All interstitial atoms—extrinsic or intrinsic—as we cursorily call all the fellows sitting on interstitial places, can movearound randomly as shown below. All they need to do is to squeeze from wherever they are to one of the neighboring
places. Which one of the eligible places they pick for their move is completely random. So interstitial atoms, in contrast
to proper lattice atoms, don't need vacancies as vehicle if they want to move; they just jump from one place to aneighboring one, see the animated figure below.
All they need for jumping around is a bit of energy=temperature. Make your crystal hot and its interstitials will getaround. The proper atoms of the crystal, however, are not involved in all that interstitial frolicking. They stay where
the are—except if a vacancy drops by.
We have essentially the same thing for the vacancies. They can hop around at random like interstitials, see the figure
below. But there are major differences to the interstitial jumping mechanism, too:
1. First, interstitials are usually more lively than vacancies. They jump far more frequently at a given temperaturethan vacancies.
2. Second, if a vacancy moves by jumping to some neighboring place, it was really an atom of the crystals that has
jumpedJumping is what interstitials and vacancies actually do. It is a good word for the mechanism by which atoms movebut it is a bit too simple for scientific purposes. The word "jump", after all, might stem from Gallo-Romanic dialectsof southwestern France: "jumba", meaning "to rock, to balance, swing" or even "to do the sex act with" (or bump).
We scientists certainly don't want to get mixed up in that; it might have prevented us from becoming scientists, for
God's sake!
So we came up with a serious word and called the random jumping around of atoms "diffusion" and themechanisms by which they do it "diffusion mechanisms ".
The word "diffusion" comes from the Latin "diffusionem", meaning "pouring forth," "scatter", "apart, in every
direction" and thus is much more high-browed than the lowly "jump" or "jumping mechanism".

Direct interstitial diffusion

Diffusion via vacancies

Animated diffusion mechanisms
Diffusion or the random movement of atoms is an extremely important major point for sword making—that's why I haveintroduced it before. In case you forgot, here is the quote from chapter 4.4.2:

The major reason why we heat up ouriron and steel a lot during sword making
is the need to make vacancies
so we can move atoms around.
Diffusion of atoms thus can happen in two ways:
Diffusion of interstitial atoms or interstitial diffusion mechanism.
Diffusion via vacancies or vacancy diffusion mechanism.

Iron, Steel and Swords script - Page 103

Either mechanism moves atoms around in a random fashion, and moving atoms around is what is needed if we dosomething to our steel - you know that by now.
Like it or not, the diffusion of carbon interstitials in the iron crystal and the diffusion of the iron atoms
themselves are the major reason why we heat (or cool) our steel during forging a sword.
In consequence, we really need to understand diffusion if we want to tackle the big "why" questions.
Let's start by considering how far a diffusing entity—a vacancy or an interstitial—has moved after it jumped aroundrandomly for some time in its crystal lattice. That's not an academic question at all, it has straight bearings to real life.
Imagine a crowded bar somewhere in the desert, discharging rather drunken but happy regulars all the time. They
will stumble around at random in two dimensions: one step forward, two steps to the left, another step forward, a
step to the left, two steps back, .... For perfect model drunks it is equally likely that their next step will go forward,
backward, left or right. They are doing what is called a random walk in sober science. Now comes the decisive
question:
You know where the bachelor party took place. Where are you going to look for your husband the helpless persons
after they left the party, did 1.000 random steps, each on average 50 cm long, and then decided to lie down and go
to sleep?
You're not going to look for that slimeball? I can understand this. So let's assume that you are the owner of the bar
who depends on the business of those random walkers and goes out to collect them.
Let's look at the figure below to get an idea of what it is all about. Instead of your drunken spouse, I have a vacany
move about, it is far easier to draw.

Random Process of Vacancy Diffusion andDistances Covered.
The average distance covered by the vacancy or the
diffusion length is far smaller than the total distancecovered or the path length. The arrows show thejumps of the atoms into the vacancy.
The figures above and below show it all schematically in two dimensions (you're welcome to supply a good and clear
drawing of these processes in three dimensions. If it is really good, I will use it in the next edition of the hyperscript).
Right now you must imagine what it looks like in three dimensions.
Hint: In bird heaven there is a bar, discharging rather drunken but happy birds all the time. They will fly around at
random in three dimensions: one step up, one to the right, two down, one to the left, .... For perfect model drunken
birds it is equally likely that their next swoop will go forward, backward, left, right, up or down.
You also can imagine drunken sharks if you are fearless.
If you want it easy on your (by now drunken?) brain: just watch a single fly in one of those swarms of flies hanging
around my and your garden in late summer, buzzing around apparently at random in three dimensions.
All those random walker, flyers or swimmers cover some total distance or path length that is simply given by the
number of steps time the average step length. But that was not the question. The question can be phrased inseveral ways; in what follows I'm going from the specific to the general:
Where are you going to look for your husband the helpless persons after they left the party, did 1.000 random
steps, each on average 50 cm long, and then decided to lie down and go to sleep? That was the originalquestion.
Where are you going to look for a random walker who did N random steps, each on average a cm long, andthen decided to lie down and go to sleep? That is the original question rephrased and generalized
How far, on average, does a random mover in 1, 2, or 3 dimensions move away from its starting point?
What is the radius of the circle (sphere), drawn around the origin of a random mover, where it is most likely tofind the mover after N steps?
What is the diffusion length of some random movement?

Iron, Steel and Swords script - Page 104

When a smith case hardens a sword, he diffuses carbon atoms from the surface of the blade into the interior of theblade. We know that carbon hardens steel (we still don't know why, however), and now we know that the thicknessof the hardened part is given by the diffusion length of the randomly diffusing carbon atoms. That's the distance they
go on average into the blade from their starting point somewhere on the surface of the blade.
So it would be neat to be able to calculate the diffusion length. Can we do it? Well, I don't know about you, but I
certainly can.
How long is the diffusion length of some randomly perambulating particle about which we know a few things? You
probably wouldn't guess that it was Albert Einstein who first figured that out. The extremely simple answer to the rather
tricky question is:
The diffusion length L of randomly moving objects scales with the (average) width a of one step and the square root of
the number of steps N they made; L=aN ½. Sorry, I almost forgot my promise (too many beers at the bar).
Let me give you an example: Your drunken spouse, after doing 1000 steps with an average lenght of 0,5 m will on
average have covered a distance of (1000)1/2 × 0,5 m=15.81 m from the bar.
There is no square root sign in HTML, so I will always use the mathematically equivalent "power of ½" notation.
Just to be on the safe side, let's emphasize an extremely important, if obvious, point. You will, for almost sure, notfind your spouse at a distance of 15.81 m from the bar, just as you for almost sure will not find a women, whodelivered her baby exactly at the predicted distance in time. Try to find the guy who personally has exactly theaverage income for your peer group. You can be almost sure that individual incomes are never the same amount as
the average income. Same for diffusion lengths.
Below you can watch what getting away by random walk looks like. Just imahine that we start a lot of random
walkers at some place in a street and watch their progress. They will ony be be able to go left or right (it's a very
narrow street). Just press "Run", pick your favorite red dot, and see how it does in the race of drunken red dots.
The great drunkards race
Details here.
Ignore everything except the "Run", "Stop" and "Reset" buttons.
How is it done? Your PC flips a coin for evey red dot. Head means "go left", tail means "go right". The PC can dothis rather fast for a lot of red dots, and it can keep track of what is going on. That allows to display the distributionof the red dots and to produce the bar chart, telling you how many red dots you will find in the interval given (the"distribution function"). I hope it doesn't come as a big surprise that eventually the typical bell-shaped curve
emerges, also known as "Gaussian distribution", that you find for many statistical phenomenae.
Now let's make a little table to see what happens if your spouse keeps stomping around for longer and longer times:
Number Steps Diffusion Lenght [m] Path Lenght [m]
10

1.58

5

100

5

50

1.000

15.81

500

10.00050

5.000

100.000

158

50.000The step width is 50 cm=0,5 m
This makes rather clear that you don't get all that far with random walking. After he has covered a total length of 5km, he just will be 50 m away from his starting point - on average ! Ten times that distance - 50 km, hard to do in
one fell swoop even when sober - and he will just be 158 m away.
So keep in mind that average distance covered and now called a diffusion length increases only slowly with the timeor number of steps our random walker or flyer is able to do.
Now let's turn the question around. We want a 10 µm thick outer layer of our blade case-hardened by diffusing carbon
into the steel. 10 µm is about a quarter of the thickness of a hair, so it is not very much. The step width of carbon atoms
is about 0.3 nm or 0.0003 µm. How many jumps are needed? And how long is the path length, the total distance a
carbon atoms covers?
Sounds suspiciously like one of those dreaded math problems (one banker can embezzle 50 Mio Dollars in three hours.
How much money can 3,5 bankers destroy in 3 month?). Try nevertheless - or look at the answer:
It takes 1 110 000 000 or 1.1 ·108 or 111 Mio jumps. The jumping atoms covers atotal distance of 33 000 000 nm or 33 000 µm or 3.3 ·104 µm or 33 mm or 3.3 cm
or somewhat more than an inch!
We are getting dangerously close to using equations and thus math, and that I
promised not to do. So look up the "random walk" science module if you areinterested in a bit more of that.
Iron, Steel and Swords script - Page 105

It takes 1 110 000 000 or 1.1 ·108 or 111 Mio jumps. The jumping atoms covers atotal distance of 33 000 000 nm or 33 000 µm or 3.3 ·104 µm or 33 mm or 3.3 cm
or somewhat more than an inch!
We are getting dangerously close to using equations and thus math, and that I
promised not to do. So look up the "random walk" science module if you areinterested in a bit more of that.

Science
Link
RandomWalk

Now let's look a bit more closely on how those interstitials move about:

Random Process of Interstitial Diffusion andDistances Covered
The average distance covered or diffusion length
obviously follows the same rules we had for thevacancy movement.
It's essentially the same picture as for the vacancy movement, and all statistical rules apply just as well. We usedthat already in the hardening example above.
There is a big difference, however: the crystal atoms do not move.
To make things more realistic, I will now give you a few numbers for vacancy concentrations. There will be more later
on, after we learned that iron comes in more than one structure.
Vacancy concentration
10-5=1 out of 100 000 atoms is missing=0,001 %=10 ppm

Close to melting point at 1811 K(1538 oC, 2800 oF)

2 × 10 -8
or 20 ppb

Around 1.000 K(727 oC, 1340 oF)

1,5 · 10-29
or simply zero because
there are less than
1029 atoms

At room temperature
300 K

A concentration like 2 × 10 -8 seems to be negligible, too, but that is wrong. Just as a tiny percentage of the
population, take terrorists or scientists, for example, can cause a lot of pain or joy, respectively, to the rest of thehuge population, just a few vacancies make a world of difference to a crystal.
Here are a few more numbers:
Moving Things
Diffusion length@ 700 oCTime

CarbonVacancyinterstitial
1s

25 µm

2 nm

100 s

250 µm20 nm

1.000 s800 µm65 nm

Now that is interesting if you compare that to the example from above. The carbon atom had to cover a huge
distance for a lousy diffusion length of 10 µm. Here we get substantially large diffusion lengths and that's because acarbon interstitial actually makes about 300 million jumps per second at 1000 K! The total distance covered, thepath length in other words, is then 80 mm.
Iron, Steel and Swords script - Page 106

The vacancies, in comparison, are rather sluggish. At 1000 K they jump just a few
times per second. It needs higher temperatures to get them going.
At room temperature, our carbon atoms still make one jump or two per second,
while the iron atoms are not doing anything anymore (except vibrating a bit).
More to that in the science super link.
We'll have a little break now. I will be back shortly

Link HubDiffusion

I'm back. I hope you checked out the super science module in the meantime. It's a "super" module because it acts as a
hub to more modules.
But even if you're the type who ignores commercials and rather uses the time to drink beer or to make room for morebeer, we can arrive at a simple conclusion as far as sword making (and about making everything else) is concerned:

We need to heat up our steel for diffusion
to happen! Things speed up a lot("exponentially") with increasing
temperature.
We need diffusion so atoms can move. We need to move atoms so things change. We just have answered one ofthe "why" questions: Why do we almost always need to heat things to make things? Edible food, pottery, fire,
metals, microelectronic chips, and so on. Now you know.

Iron, Steel and Swords script - Page 107

5.3 Two-Sided Defects and Bulky Things

5.3.1 Grain Boundaries
If I would follow the order put down in the beginning of this chapter, one-dimensional defects or dislocations would benext. I won't do that. I will skip the one-dimensional defects for the moment and go right to two-dimensional defects.
Besides the two-dimensional defect "surface" (which is a bit trivial) we need to look atGrain boundaries
Phase boundaries
Stacking faults
Grain boundaries go first. They are easy to conceive; we have a lot of them by definition if we look at a poly crystal.
Whenever you look at crystals, chances are that you actually look at poly crystals and thus at grain boundaries - even if
you can't see them because your brain microscope is off.
You don't see grains boundaries, even with you brain microscope on, whenever you look at single crystals . There
aren't all that many of those around, however. What we have are:Gemstones like your wife's diamonds and rubies.
Some special turbine blades inside jet engines.
Some very special optical components.
Major semiconductors like silicon (Si), gallium arsenide (GaAs) or gallium nitride (GaN) found inside
electronic products like microchips or LED's.
The latter ones are the most perfect and ubiquitous ones. You must open up a chip if you want to see them. Go
ahead, do it. It is fun, even so you kill the device by doing it. You finally revenge yourself on all those chirping andbeeping gadgets that keep you from drinking beer. Also, it's less dangerous than fiddling around with your wife's
diamonds. What you are going to see is shown (in its original state) in this link
You have seen many grain boundaries without noticing. Mostly because they are invisible to the naked eye, but also
because you didn't know what you saw.
If you look at almost everything around you that is not glass or biology, you see poly crystals, which, by definition,
contains plenty of grain boundaries. You just don't see them because the surface typically doesn't show the internal
crystal structure. Even if it does, chances are that the grains are so small that without a microscope you can't see
them.
Both points hold for your sword blade. First, it is probably polished, and that is just another way of saying that there
is no visible structure on the surface. Second, the grains are so small that you couldn't see them anyway, not tomention the boundaries that separate them.
There are exceptions, however. When a puddle freezes over in the more northern countries you look at frozen water
called ice. There you might see grain boundaries as the line separating different large grains.
Grain boundaries are definitely visible if you look at a lamp post or any other "galvanized" metal object, i.e. metals
with a thin coating of zinc (Zn). The zinc grains can be very large and they are clearly visible, see below. The socalled "multi-crystalline" silicon used for solar cells has huge grains, too, and also shows the grain structure rather
nicely as shown below.

Visible poly crystals and grain boundaries
Galvanized sheet metal with clearlyvisible grains of the zinc (Zn) coating.

Slice of multi-crystalline silicon (Si)used for making solar cells withvisible grains of silicon.

Iron, Steel and Swords script - Page 108

Actually, what you really see are the grains. You see them because different grains of zinc (Zn), silicon (Si), or
whatever, with different crystal orientation, reflect light differently. In between different grains there must be a grainboundary; look at our old picture again if you can't quite "see" it. So what does a grain boundary proper look like?
That's a rather difficult question. First we need to rephrase it a little: What is the atomic structure of a grainboundary? How do the atoms stick together if you cross from one grain to a another one? The answer leads into oneof the more complex area of materials science with rather heavy math and still unclear parts; this link to anadvanced module gives a little taste treat.
You don't quite see why this should be a difficult and complex part of Materials Science? Then you should have noproblem with a very simple exercise
You don't want to know all that much about grain boundaries, you just want to see some? OK— in this link aresome pictures.
All you need to know about grain boundaries right now is that they cause massive disturbances in a crystal. In otherwords, they introduce planes or "sheets" with rather high energy in the crystal. There cannot be proper nirvana if grainboundaries are present; the disorder they produce never balances the huge additional energy they carry with them. It isjust as in the case of extrinsic impurity atoms: You got 'em, you pretty much keep 'em! So let's note down in big letters:

Grain boundaries like all defects except
for intrinsic point defects prevent
nirvana conditions.
They just have too much energy.
We call the energy coming with two-dimensional defects "grain boundary energy" or phase boundary energy, or
surface energy. We always give it as a specific energy per cm2. The energy of two dimensional defects thus is their
specific energy times the area they occupy. For the nirvana state this is bad. The crystal doesn't want either of them.
Too bad that it is very difficult for a poly crystal to get rid of its grain boundaries. Too bad for the crystal, but good for us
as we shall see.
The crystal certainly tries to get rid of its grain boundaries by trying to make the grains larger and larger, until only
one grain remains. Grains, however, will only grow at very high temperatures, and rarely enough to produce a single
crystal. If you are not inclined to wait at high temperatures until hell freezes over, your poly crystal will still be a poly
crystal, albeit with larger grains.
And all is well! For making good swords we need grain boundaries for various reasons. One is shown right below:
Let the atoms jump as
indicated and the twogreen "vacancies" hidingin the grain boundary
move into the crystal.

Grain boundary emitting vacancies
Let the atoms jump as
indicated by the redarrows and the two green
vacancies in the crystal
move into the grainboundary. The green
arrow indicates an atom
after the jump
Grain boundary absorbing vacancies
First I want you to appreciate that it is impossible to draw a grain boundary "edge-on" in two dimensions without
producing some "thinned-out" regions, with fewer atoms in a given volume compared to the perfect crystal.
Now we can "see" why grain boundaries are high energy defects. Atoms sitting in a grain boundary (or close by) just
can't get as many partners as they want and where they want them. It takes a lot of work or energy to produce such anarrangement and that's why grain boundaries are high-energy defects.
What about their entropy or the amount of disorder they introduce into a crystal? Well—forget it. Obviously they do
produce disorder but the balance of energy vs. disorder is always very lopsided. There is no way to compensate for theheavy increase in energy by gains in the TS product (remember?). For the crystal, grain boundaries are therefore just as
unwelcome as extrinsic point defects.
Iron, Steel and Swords script - Page 109

From contemplating the figures, you may now have experienced a certain epiphany or enlightenment! Grainboundaries (and other "big" defects) are the places where those "missing" atoms go when you make vacancies!
Yes. That's correct. Now you know! It only remains to figure out where those missing single socks go but I will leavethat task to you.
Next , I ask you to look at the figures above and imagine many vacancies going in (or coming out) of a grain boundary(there is a limit to my drawing skills). What happens to the grain boundary in this case? You then realize that the only
thing that happens is that the grain boundary moves .
And now you also know why you need to heat your steel (or any crystal) to allow for grain growth or to "anneal" or"normalize" it. You simply need a lot of vacancies moving about to "heal" the crystal of all its other defects. Another"why" question has found an answer.
One more big thought. A question I asked before is how the crystal knows how many vacancies it needs to have fornirvana? The answer was: it doesn't, and so on.
Now we see a bit better what happens. Grain boundaries emit and absorb vacancies all the time in a completely
random fashion. If on average they emit more vacancies per second than they absorb, the vacancy concentration in
the crystal goes up; the other way around it goes down. What happens depends on the temperatures and maybe a
few other things. But it just happens, no "thoughts" must be given to this business.
It's more or less like your bank account (or the state "bank account" called economy): it emits money at someaverage rate to you (or to all of us). This is simply the money you withdraw or that is taken out of your account byothers like the IRS. Your account also absorbs money (whatever goes into your account). If the money
concentration in your environment goes up or down depends on the difference between the two rates. The rates
change if the economic climate or temperature changes; in crystal the rates change with temperature proper. And
you don't really control all of this closely or think much about it. You just react to general conditions.
Now let's generalize a bit: Grain boundaries are something like garbage cans for all unwanted point defects. Selfinterstitials and vacancies disappear at grain boundary without any direct traces; all that happens is that the boundary
has moved a bit.
Extrinsic point defects or impurity atoms cannot disappear without a trace at a grain boundary; it's exactly like yourgarbage. It might be in the can—but it still exists. In normal life, you probably like your garbage better in the
garbage can than all over the place; your wife most certainly does.
The crystal also likes to imprison his surplus impurity atoms in grain boundaries just the same. The disturbancethey cause in the perfect crystal is simply larger than the disturbance they cause in the already disturbed grainboundary. However, grain boundaries are not very efficient garbage cans for impurity atoms. They are useful if there
are only a few impurity atoms around but if there are many, the crystal needs to find better "prisons" for impurity
atoms than grain boundaries.
If grain boundaries do manage to capture impurity atoms and hold on to them, new problems might come up. For
example, if your grain boundaries have sucked up all the sulfur atoms that were roaming around in the grains, you
now have clean grains and grain boundaries that consist of thin sheets of sulfur. Heat up such a steel, and when thesulfur melts at just about 113 oC (235 oF), your grains will fall apart. It's a bit more complex than that but that isessentially the mechanism that causes "red shortnes". We will get to this later in more detail.
Anyway, looking at grain boundaries, we learn a big truth. The crystal wants to get rid of those defects but can't quite
make it, it thus can never ever reach the true nirvana state. So what is it going to do about that situation? Exactly what
you and I would do:

If you can't achieve nirvana,go for the second best option!
Lower the energy as much as you can. If you can't get rid of certain defects, mix and combine them in the best
possible way. The pain of having too much energy then is relieved to some extent, in particular at low temperatures
where the substantial disorder or entropy produced by all these defects hardly counts any more.
It only remains to ask: Why do we almost unavoidably get poly crystals with grain boundaries if that is not what the
crystal likes? That's easy to see.
Whenever a solid crystal forms because a liquid freezes, this doesn't happen in one fell swoop but gradually, startingfrom tiny nuclei (Latin for seed or germ). That's so because the first step in going from being liquid to being solid, or if
we generalize a bit, from one phase to another one, is always a very difficult thing to do.
Phase changes (that's what freezing is, remember?) almost always occur first at places where there is a little help
to be had. For solidification or crystallization the wall of the container helps a lot. It's colder there than in the insideof the liquid (the inside is always hotter than the outside as you know if you ever ate a hot potato) and there might
be convenient spots where an atom can get some rest (they are running around in the liquid state, remember?)
Nucleation, the forming of the first tiny crystals of the solid phase, then starts independently all over the place at"good" places or nucleation sites at the container walls.
Then the initially formed nuclei grow—the crystallized parts become larger—and eventually bump into each other.
Since the crystal orientation usually is random, the crystal lattices do not fit wherever they finally meet and a grain
Iron, Steel and Swords script - Page 110

boundary must form, see below.
Solidification in progress
Nuclei formed randomly andindependently at some tiny
irregularities on the container
wall and grow into the remaining
liquid. The color symbolizes
different orientations of thecrystals / grains.
Solidification is finished
The independently formed
crystals with random orientation
grew together, forming thegrains of a poly crystal.
Steps in uncontrolled crystallization of a meltVery
schematic and far too simple. I'll get back to this later.
While the schematic figures above give an idea of what happens, this picture shows reality:

Grain structure in copper
Huge size
Source: Wikipedia / The Net at large

Crystallization obviously proceeded from the outside to the inside. Whenever growing grains met, a grain boundary
formed. Also something needed to happen because there was not enough place for all grains to continue growing.
What happened is clearly visible: some grains stopped growing.
The figures and the picture are two-dimensional. Grain boundaries, however, enclose a complete three-dimensional
grain. They thus must curve around in three dimensions—but that is difficult to draw, and not so easy to show in
pictures either. It is not so difficult, however, to imagine the whole thing. Just think of the foam on your beer, forexample, imagining that the thin membranes of the bubbles are rain boundaries, and you have an idea of what a threedimensional grain boundary structure could look like.
Here I always draw grain boundaries "edge on". On rare occasions you also can see a real grain boundary exactly"edge on", indeed, in some thin slice of a material. Then you might be able to take a HRTEM picture.
The picture below shows the atomic structure of an actual grain boundary exactly edge-on in gold (Au), comparethat to the figure above.

Iron, Steel and Swords script - Page 111

Grain boundary in Gold (Au) standing "edge-on"
and imaged
at atomic resolution.
The insets show schematically the orientation of the
cubic fcc elementary cell (not at the same scale as
the picture).
The picture once more illustrates nicely that grain boundaries are good places to imprison impurity atoms in. There isjust more room than between the atoms of a regular crystal.
Grain boundaries are also great places to nucleate something . They are a kind of internal "wall" with plenty of
distortions. So making a bit more distortion by starting something new there—for example a precipitate—is not as
difficult as inside the perfect crystal.
Nucleation is a key word not only for sword making but for making most everything from technical materials. It evengoverns your very existence. Did you ever wonder why you (or a piece of wood, a bucket full of oil, ... ) do notspontaneously self-combust? That would release a lot of energy and thus bring the collection of atoms that
constitute you, a piece of wood, and so on, much closer to nirvana.
I will come back to this a lot; it's a cornerstone in all of Materials Science! Meanwhile you can ponder the question
what kind of structure the collection of atoms that constitute you might assume for nirvana. You might even want tojump ahead to the science module about nucleation.
Finally, let's take a quick look at why grain boundaries matter directly in sword making. A grain boundary, as the word
implies, separates different grains of the same material. The grains are three-dimensional objects with a certain size.
If the grains are enormous, (several millimeter (mm)) you can see them by just looking (as in the pictures above). If
they are just large like several ten micrometers (µm), you can't see them with your unaided eye but easily with astandard optical microscope or some fancier microscope as in the pictures below. If they are small and "nano" (farbelow 1 µm) you need an electron microscope.

Iron, Steel and Swords script - Page 112

Grain structures in steel made visible by optical
microscopy
Source:Top: Anne Feuerbach
Bottom: BAM; Germany; with permission

The top pictures shows the grain structure in a 5th - 6th century AD double-edged sword from Kislovodsk. Black
corrosion proceeds from the upper left, with cracks running down grain boundaries. This blade was made from rather
soft wrought iron. The black dots are slag inclusion
The bottom picture shows the grain grain structure in hot-rolled modern steel. Fancy optical or electron microscopy
provides for color. Grains with the same orientation have the same color. Note the elongation of the grains by therolling process.
Let's note right now that grain size matters a lot for sword blades! If you somehow succeed to reduce the average grain
size by a factor of 100 (from 50 µm to 0,5 µm, say), your blade will be about ten times harder (yes, there is a squareroot law in this). The obvious "why" question going with this statement I will tackle later.

The message is clear:
We want small grains in sword blades!
When you first crystallize a material from the liquid state, you almost always end up with a poly crystal that has someaverage grain size. This may or may or may not be the grain size that you would like it to have. In either case you must
now do battle with the crystal:

You want the grains to be small. The crystal,for the usual nirvana reason, likes to haveits grains as large as possible.
A crystal is a tough opponent. It is not easy to make grains very small (say below micrometer) and quite often you
find grain sizes in the 10 micrometer range. For millennia we had to live with this (without knowing, of course). Therewas just no way to make grains much smaller by trial-and-error.
The situation has changed. The present "nano" madness in science and engineering is also a bit about finding more
an more ways to outsmart crystals and to make tiny "nano" grains. Not by trial-and-error but by understanding andcalculation before acting.
If we want to change the grain size in a given material, the grain boundary need to move. That is a simple but farreaching truth. If some grains gets larger, its grain boundary must move outwards, and other smaller grains must get"eaten up" in the process. If you want to make the grains smaller, same thing in reverse.
The obvious question coming up now is: how can a grain boundary move? Well, we have already dealt with some
aspects of the answer right above.
A bit more generally the answer, like ever so often, is:Iron, Steel and Swords script - Page 113

Grain boundaries generally move byatoms jumping around or,as we now call it, by diffusion of atoms.
Here is the magic word once more. Friendly vacancies need to come by, helping atoms on one side to move to a newposition that now belongs to the other side.
Vaguely recalling the relevant numbers, we realize that appreciable movement of grain boundaries and thus grain
growth will only happen at rather high temperatures.
For the usually "achieve nirvana" reasons, the grains will invariably get larger (and thus fewer) at high temperatures.
There is no way you can make them smaller by just heating and waiting.
For making grains smaller we need some other tricks, involving "dirt". I will give you more about that later.

1)

Ann Feuerbach: An investigation of the varied technology found in swords, sabres and blades from the Russian Northern
Caucasus" iams 25 (2005) p. , 27 - 43.

Iron, Steel and Swords script - Page 114

5.3.2 Phase Boundaries
Now let's look at phase boundaries, the second important two-dimensional defect.
Like a grain boundary it has two sides but now different things (or, as we call it, different phases ) are separated bya phase boundary. After all, our iron comes in more than one phase and on occasion we have both phases
simultaneously .
Between two atomically connected phases we then must have a phase boundary by definition.
You have seen a lot of phase boundaries. Or maybe you didn't. There are none so blind as those who will not see. Fine,
let me help you. In the following picture you can see a lot of phases and therefore also phase boundaries between thephases:Phase boundaries in the granite top of mykitchen counter
Granite is always a mixture of quartz (SiO2) and some feldspar (silicates like (KAlSi3O8, NaAlSi3O8, CaAl2Si 2 O8,
and many more) and, in this particular granite, some mica (the black stuff; rather complex sheet silicates,e.g. KAl 2[AlSi3O 10(OH)2] or muscovite). So we have at least three phases mixed rather haphazardly.
The boundary between the melt and a growing (or melting) crystal also constitutes a phase boundary, so you haveseen phase boundaries whenever you have an ice cube in your whisky.
Your skin (loosely speaking) is a phase boundary. On one side is air, on the other side is you (in the form of bones
and some slimy stuff).
More to the point, the boundary between a crystal of type A (for example pure bcc iron) and a crystal of type B (forexample an iron carbide particle) is a phase boundary and so is the boundary between bcc iron and fcc iron that isshown below:

HRTEM picture of a phase boundary separating
fcc and bcc iron.
Source: T. Moritani et al.

The white line shows the position of the phase boundary and the insets show schematically the orientation of the
cubic elementary cells. The white dots are columns of iron atoms.

Iron, Steel and Swords script - Page 115

Phase boundaries standing "edge-on"
Source: MeThis HRTEM picture shows a phase boundary between fcc silicon (Si) and hexagonal palladium silicide (Pd2Si). The
white dots, just about recognizable, are columns of atoms once more.
I admit that the phase boundary between fcc silicon (Si) and hexagonal palladium silicide (Pd2 Si) might appear a bit outof phase here. Silicides from one of those material classes that you have never encountered before and are notimportant for swords. Nevertheless. they are are quite important, e.g. for micro electronics.
Chances are that you, personally, are a also direct user of a silicide without knowing that (hint: look for"molybdenum silicide" in the Net).
Be that as it may, I just happen to like the Pd2Si picture a lot. First, because to the best of my knowledge, it is thevery first high-resolution TEM picture of a phase boundary ever taken, second, because it was taken by me in 1980.
So, now you have seen two pictures of actual phase boundaries at atomic resolution. Or have you? Looking at twodimensional things only edge-on is a bit deceiving. Here is an example that needs no further comment:

Edge-on view and top view of one of ny rug
Since you asked: It is a (modern version of ) a Sivas
Sal
You are going to miss something for sure, if you look at planar defects only edge-on!
So let's look at some phase boundary in both views, too. I take some of my own pictures since I don't have to worry
about copyright problems then.

Iron, Steel and Swords script - Page 116

Edge-on view and top view of a phase boundary
betweensilicon (Si) and nickel silicide (NiSi2)
Wow! In the bottom picture a dense network of misfit dislocations is present. There certainly is a lot to see in the
top view that you don't see edge-on! What you see is even more complicated than in the case of the grainboundary structure, and you really don't want to know about this.
You do? Good. Maybe you have a feeling that the detailed structure of phase boundaries could be important?
Boy are you right! Pretty much all of semiconductor technology and in particular optoelectronics relies on phaseboundary engineering. Turn to this advanced module after you have finished chapter 5.
What the picture also shows in a visual if qualitative way is that phase boundaries are high-energy defects, just likegrain boundaries. We just learned this but it is good to repeat it.
It should be clear by now that the crystal doesn't want phase boundaries any more than it wants grain boundaries.
However, while it could get rid of grain boundaries in principle if not in practice, it cannot get rid of phase boundaries
as long as it wants to have precipitates (meaning a completely enclosed second phase; look a chapter ahead if you
don't know what that means) for nirvana reasons. In certain conditions the crystal needs to have precipitates forachieving nirvana; we will learn about that presently.
The crystal now faces the classical problem that you can't have your cake and eat it. It can't have precipitates
without having phase boundaries that envelop the precipitates. All it can do is to optimize the situation and that calls
for having just a few large precipitates. All we can do in metal technology is to interfere with the this optimization
process and coerce the crystal to do it in a way we like.
Large precipitates result by the growth of originally small ones. What that means is that the phase boundary must
move—just like grain boundaries when the grains grow.
Now back to the topic. You guessed it: in sword making we need to move phase boundaries around quite a lot too, so
we answer the standard question right away:

Phase boundaries move as soon as
atoms can move aroundWe have another phenomenon that depends on some diffusion process.
The best examples for phase boundaries coming with precipitates are the iron carbide (Fe3C) particles invariably foundinside steel. Whenever they grow or shrink, the phase boundary separating their surface from the crystal must move.
And for doing this, carbon atoms must move, too.
I'm not talking "theory" here but, for example, the making of wootz steel blades where the smith must grow theiron carbide particles to a rather large size.
So just accept it. We will encounter phase boundaries a lot when we attempt to make any sword blade, and they will
come up right again in the next paragraph.

1)

T. Moritani, N. Miyajima, T. Furuhara, T. Maki: "Comparison of interphase boundary structure between bainite andmartensite in steel" Scripta Materialia 47 (2002) p. 193–199

2)

FÖLL, H., HO, P., TU, K.N.: "Cross-sectional TEM of silicon-silicide interfaces" J. Appl. Phys. 52 (1981) o. 25

Iron, Steel and Swords script - Page 117

5.3.3 Stacking Faults
In chapter 4.2.1 we generated simple crystals (with just one atom per lattice point) by stacking spheres in exactly theway you would do when you put up a mound of oranges or cannon balls. You start by arranging the spheres on a plane
as densely as you can. Than you start the second or B layer on top of the first or A layer. Naturally you put the spheresof the second layers in the hollows or dents of the first layer.
When you go for the third layer you have a choice. You can go for the option where the spheres of the third layer arein those hollows of the second layer that the third layer sits right on top of the first layer and thus is an A layer
again.
Or you go for the other option where you produce a C- layer. We found that two kinds of stacking sequences bothlead to a close-packed crystal:
The stacking sequence ABABABA... produces an hexagonal crystal (hcp; hexagonal close packed)
The stacking sequence ABCABCA... produces a cubic face-centered fcc crystal.
Before we looked at all this stacking stuff from the top. Now let's restrict ourselves to the fcc lattice / crystal and look at
it sideways. Here is what you would see (schematically, of course!)

Perfect and faulted stacking sequence for an fcc
crystalOn the left-hand side we look at a perfect fcc crystal. The A-layers are on top of the C -layers, the B-layers..., and soon. Rather boring.
Now look at the right-hand side. A devious person has put an A-layer on top of a B-layer and thus broken themonotony by creating a planar defect that is aptly called: stacking fault.
Well, why shouldn't one do this? If you look at the contraption from the top the proper C-layer or the faulty A layer
look pretty much the same. Stacking faults thus should occur all the time?
Well - no! At least not for the reasons you may have in mind. Atoms "in" a stacking fault do see an environment
different from atoms in the perfect bulk, in particular if they look beyond just their nearest neighbors. That means
they have not the best possible environment and this are not in a nirvana state.
In other words, a stacking fault has some stacking fault energy (per area unit) just like grain boundaries andphase boundaries. Nirvana will not be attained if stacking faults are around, just as nirvana will not be attained withgrain boundaries around.
So why are we doing this? Because stacking faults are very important defects, in particular in fcc and hex crystal. And
where are they coming from?
Good question! One might assume that they simply are formed when the material is formed and that they cannot be"taken out" again later - just like grain boundaries. That is true enough in some cases but the full truth is more
complex:

Stacking faults occur:
1. during crystal growth,
2. as part of other defects
3. because they evolve from other defects
Three reasons for stacking faults. Let's look at them one by one:
1. Stacking faults occur during crystal growth
Just one example: Silicon carbide (SiC), an extremely interesting material for electronics, comes in many different
types of lattices. The figure below shows just six. It is is obvious that about any stacking sequence can exist. It isjust as obvious that you can have any number of stacking faults in there too.

Iron, Steel and Swords script - Page 118

Six different silicon carbide (SiC) crystal
structures (or polytypes)
Here is the reason why you (most likely) don't have silicon carbide electronic components in your possession. It isjust too damn difficult (and expensive) to make a perfect crystal as needed for electronic applications.
You also need to be careful not to produce stacking faults when making silicon or other important crystals while thematerial solidifies. It is not too difficult, however, to avoid stacking faults in these cases so nothing more shall besaid about this point.
2. Stacking faults are part of other defects
If I would have already introduced the one-dimensional defects called dislocation, and if, in discussing that defect, I
would go all the way to what is called "partial dislocations" and "split dislocations", I now could enlighten you about
stacking faults being an integral part of dislocations, interfering mightily with their properties.
I didn't and I won't - so forget it. All that stuff is very important for intimately understanding materials - but way
beyond what I'm dealing with here. Consult the dislocation science module if you want a taste treat.
3. Stacking faults evolve from other defects
Now that is easy. Imagine a crystal at high temperatures. It will be full of vacancies because that is part of nirvana.
In the schematics I have adopted here, it looks like the upper half of the figure below.
Now crank down the temperature. The point defect concentration needed for nirvana decreases sharply. But how?
Where do the surplus vacancies or self-interstitials go? Well - to the grain boundaries as we just asserted!
Absolutely true. That's what they do in normal fine-grained poly crystals.
But how about single crystals or crystals with large grains, where the grain boundaries are far, far away?
In this case vacancies (and self-interstitials, if around) tend to agglomerate or cluster, often in a small disc. This isshown below on the right-hand side for vacancies.
The rest is obvious. If the vacancy disc gets large enough, the two "surfaces" just collapse and bond to each other,
forming a stacking fault disc in the process as shown on the left hand side.

How stacking faults evolve from vacancy
agglomeration.
This is quite serious if you are into defect-free crystals like silicon or all the other ones needed for all kinds ofmicrochips.
The electron microscope pictures below show stacking faults formed by agglomerating silicon self-interstitials.
Forming a layer of atoms squeezed in between the regular layers is their only way of escape; this link provides a
picture. The vacancies, while also agglomerating into stacking fault discs as shown above if they feel like it, have analternative: they could also form a three-dimensional hole or void.

Iron, Steel and Swords script - Page 119

Stacking faults as seen in an electron
microscope.
This is a projection of an inclined plane - the stacking fault plane - onto the screen. The upper picture shows tworather huge stacking faults produced during processing silicon. The lower picture shows a small hexagonal stacking
fault loop produced during crystal growth. The "zebra" pattern is a result of the inclination.
Stacking faults in silicon like the ones above kill an electronic device, so they are much feared and investigated.
They wouldn't do much to a steel sword, however, so I'm not going on about this - except to make one major point:
You have just witnessed how small zero-dimensional point defect can generate a huge two - dimensional defect. It
is just one example for relations between defects. The rule is:

All defects interact and are somehow connected

Iron, Steel and Swords script - Page 120

5.3.4 Bulky Things and Nucleation
Three-dimensional defects are next on our list. They are rather common and you simply cannot have decent steel
without them. Since they are large in all three directions, they can be rather bulky and we call might call them bulk
defects on occasion.
Voids, small holes in the crystal, are also three-dimensional defects. They might come into being because a lot of
vacancies cluster, or by some other mechanism. Voids are not important for us; I just mention them to be complete.
The three-dimensional defects that are important to us, very much so, are precipitates or small particles of a different
phase contained in a host crystal.
To get a first idea of what it's all about, we give the steel with about 1 %carbon as shown before a second look; the picture here is a reminder. The
news is that there is no iron - 1 % carbon steel that looks like that at room
temperature. Neither schematically nor in reality.
It is important to appreciate that while the iron crystal is happy with 1 %dissolved carbon at high temperatures, it really doesn't want to have thatmuch loose carbon around at room temperature. Disorder does not muchgood at low temperatures and it takes simply too much energy now to keep
the carbon atoms dissolved.
Nirvana-wise, one atom, perhaps, would be fine in the area shown above at room temperature, but no more! Since thecrystal can't get rid of the surplus carbon anymore than you can get rid of your unruly offspring, it will round up thesurplus carbon atoms and imprison them. Some will be locked up in grain boundaries but 1 % carbon is too much forthe grain boundaries.
The crystal, searching for but not getting the best—nirvana—goes for the second best and invents something new:

A new phase will form,
consisting of iron-carbide (Fe3C)
We call this new phase a carbon precipitate, and the process by which it forms precipitation. Note that thisinvolves a lot of iron too. In an iron-carbide precipitate there are three iron atoms hooked up with one carbon atom,
They are still iron atoms but no longer iron, just like the oxygen atoms in water (H2O) are still oxygen atoms but nolonger air. In principle the surplus carbon atoms could also precipitate as pure carbon (graphite in this case) andthey actually do it: in cast iron but not in wrought iron or normal steel.
Iron-carbide precipitates forms because the surplus carbon atoms, while wandering around at random, will get stuckat some tiny Fe3C carbide nuclei that then grows into a large precipitate.
Of course, we now have a hen-egg or nucleation problem:

You need a precipitate to make a precipitate?
Carbon atoms only can get stuck somewhere if there is at least a small precipitate, or, to give it its proper name, a
nucleus (singular of nuclei ). So the question is: how does the nucleus come into being?
The first tentative answer is: The carbon atoms move around at random. On occasion two will accidentally run into
each other and then stick together. Six of the surrounding iron atoms join the two carbon atoms, so that two Fe3C
molecules can be formed. The 8 atoms are somehow squeezed into the iron crystal. When another carbon atom
drops by, the cluster grows to 3 Fe3C molecules, and so on.
If that sounds like it would be an unlikely and difficult process, that's because it is an unlikely and difficult process.
It is not impossible, though, and nucleation in this way does happen on occasion.
So take note:

Nucleation is always
a very difficult enterprise.

Iron, Steel and Swords script - Page 121

If nucleation rarely happens as described above, how does it happen? The answer is: nucleation is always much easierwith some outside help. For nucleating a baby, almost all mothers need a bit of outside help too. For nucleating
precipitates and other stuff, grain boundaries for example offer that outside help (they are "outside" the crystal grain,
after all) and make good nucleation sites. Let's see how that applies to making an iron carbide (Fe3C) precipitate:
Carbon atoms move around at random, and once in a while hit a grain boundary. Looking at all the pictures I
provided in chapter 5.3.1, you will appreciate that at a grain boundary there is just more space available for lonely
carbon atoms that feel somewhat cramped-in and unloved between all the iron atoms. So the carbon atoms stays awhile in the grain boundary, far longer than in the lattice, before it moves on again.
The chances of meeting a second carbon atom that happens to come by are thus much larger than in the lattice,where everybody always jumps around at high rates. More women / men come by and talk to you for a while when
you hang out at the bar compared to jogging around at random in the park.
An additional advantage is that the iron atoms at the bar in the grain boundary are not so solidly bonded to otheriron atoms as the iron atoms at home in the lattice, and thus more amenable to engage into some iron-carbon
bonding, the very first step on the way to an iron carbide precipitate.
This first pre-nuclei (it's not an iron carbide crystal yet) is now immobile. All it needs to do is to wait until morecarbon atoms come by, to grow into a nuclei proper (tiny crystal), and finally into a precipitate with a diameterconsiderable larger than the unit cell of the Fe3C crystal. This link gives a first glance at what an iron carbide or
Fe3C crystal looks like. Just get used to the fact that iron carbide or cementite, as we will call it, is an integral partof steel.
Needless to say, we can calculate all of that, using equations that contain the energy of interstitial carbon in a grainboundary and in the lattice, the probabilities for jumps in the lattice and at the grain boundary, and so on.
Of course, the meeting of carbon atoms and so on inside the grain, as described above, is not forbidden. We even havea name for it, we call it like homogeneous nucleation in contrast to the heterogeneous nucleation that relies onsome defects as nucleation sites.
Homogeneous nucleation as described could and would happen, it's just unlikely. Two or a few more carbon atoms
meeting accidentally will easily stick together but just as easily break apart again. If they meet at a grain boundaryor some other suitable defect, they just like it there better and hang around until a third and fourth one comes along.
There is simply a competition between homogeneous and heterogeneous nucleation. Heterogeneous nucleation at
defects always wins, provided that there are enough suitable defects like grain boundaries around.
If you remember what I claimed way back about the silicon crystal for micro electronics (or even looked up the"single crystal silicon" module) you have a question now: What happens nucleation-wise in the rather perfect single
silicon crystals? There are no grain boundaries or other big defect that could help nucleating whatever needs tonucleate. Tricky! Look up this module for an answer.
But iron and steel are always polycrystals, full of defects. If we talk about nucleation of something in iron and steel,
it is sufficient to remember:

Precipitates need to nucleate somehow.
In iron /steel they always nucleate at grain boundaries or otherdefects
and rarely "just so"
I can't emphasize it enough, so once more: We need some process of "nucleation" to get the things that want to happen
to really happen. Nucleation of carbide precipitates is one of the very important but also quite tricky parts when a sword
blade is forged. It will typically happen at grain boundaries or other defects.
This is nothing special. "Seeding" clouds with silver iodine (AgI) so it rains, isworking with nucleation in the same way. Before a water drop can grow to a size
large enough to fall down (= rain), water vapor must condense on a nucleus, a verysmall water droplet, and those nuclei are very difficult to form. Some "defects",
small silver iodine particles in this case, might be helpful to get nucleation going.
By the way, all of that is difficult but there is nothing mysterious to it. I cancalculate exactly what is going on. The science super module has a lot to say
about nucleation, make sure to check it out. There is no problem in understanding
nucleation.

Science
Super
Link
Nucleation

The only problem is that the halfway decent education, that I credit you with, does not (yet) include the basics ofeveryday life.
Now let's assume for the time being that the nucleation of carbon precipitates in our sword blade was somehow takencare off. The crystal can now precipitate as much carbon as it likes to. In other words, the crystal can now form an ironcarbide crystal—something as different from iron or carbon as sodium chloride (common salt) is from sodium orchlorine—that is completely contained inside the iron crystal lattice.
How will it proceed?
Iron, Steel and Swords script - Page 122

Locking up the surplus carbon or, using our new and fancy word, precipitating it, can be done in many ways after
the nucleation problem was solved.
For example, you could produce a lot of small precipitates or just one big one, as shown schematically below.
33 carbon atoms are locked
up in several small
precipitates.
The real precipitate structure
is somewhat different but thatis too hard to draw.
3 atoms stay dissolved.

29 carbon atoms are locked
up in in just one big
precipitate; its phase boundary
is outlined in blue.
3 atoms stay dissolved.

Schematic view of possible precipitates and phaseboundaries
Now a word of warning is in order (once more). Looking at the figure above or others like these, you should realize that
there is no such thing as a fully correct drawing of precipitates in crystals.
First of all, the best I (and everybody else) can do most of the time is a two-dimensional cut through a threedimensional structure. Ask yourself: is the big precipitate shown above a cut through a roughly spherical precipitate
or a cross section through a long needle? There is no way of telling just from the picture.
Worse, drawings that are both to scale and correct in the sense of showing the proper lattice of iron, the proper sizeof the atoms, the proper structure of the precipitate, the defects inside that provided for nucleation, and so on and soforth, would be so complicated that I simply refuse to do them. They also would not show much because the firstlayer of atoms would obscure everything behind. So take all those figures with a grain of salt.
It doesn't matter much, however, that the figures cannot show all there is to precipitates. If you don't get the basic
ideas I'm driving at with all the imperfect drawings (and I don't assume for a moment that you do not), changes arerather slim that you would get them with better drawings.
Moreover, in real steel, as contrasted to the figures above, you might have to compare one precipitate containing acouple billion atoms (still only a few 100 nm in diameter), or 1000 precipitates with just a couple of million atoms
each. Hard to draw.
Whatever. The important thing to note at this point is that the total area of all phase boundaries enclosing the
precipitates, is always much larger for many small precipitates compared to a few big ones that contain the sameamount of precipitated stuff.
You know that. You get more potato peel from 20 small potatoes than from one big one.
To make things a bit more complicated so we don't get bored: in three dimensions you could make the precipitatesround and ball shaped ("spheroidal"), looking more like needles ("acicular"), plate-like as a coin, or just irregularlike a ginger root. They all would look the same in the drawings above.
So how do you, the crystal, like you precipitates? Chunky (a few big ones) or smooth (many little ones)? Spiky(shaped a like a sea urchin) or round like a ball? Donut shaped, perhaps?
The long and short of the precipitation business is that a crystal has many choices for locking up surplus impurity
atoms in precipitates. The way the crystal actually does it will decide, for example, if your sword blade is useless brittle
steel or superior wootz steel.
So what will the crystal do? Even more important: What can you do? How can you induce the crystal to do yourbidding (you're the smith, after all—remember?). And what would your bidding be? Do you go for just a few big
precipitates or lots of small ones? Round ones ("spherical") or longish ones ("acicular"), and so on?
You can't give me an answer? So go on for a few more chapters.
In contrast to you, the crystal knows exactly what it wants. It lives faithfully by the second law and thus knows what
would be best for it.
For the best of all worlds or perfect nirvana at low temperatures like room temperature, it would get rid almost
completely of the surplus carbon, just keeping the precise (extremely small) concentration that the second law
demands for the particular occasion.
If that is not possible, it will go for the second best state of being and that is to have few and then necessarily big
precipitates with spherical shape. If you don't see why, it will come to you later.
Iron, Steel and Swords script - Page 123

The problem with the crystal's choice is that we don't like it. Not at all! You and I usually prefer a lot of small
precipitates; just as we like small grains better than bigger ones.
What we take from this is that a lot of what we do when we forge a sword is to keep the crystal from making large
precipitates.

Except if we make a wootz steel sword.
Then we like our iron carbide precipitates to be rather large, and in the "right" places; I'll come to that.
Precipitates always have a phase boundary around them. They cannot avoid this any more than you can avoid having askin around yourself if you like to stay "inside".
The interface between the precipitate and the crystal is by definition a phase boundary, and phase boundaries are
high-energy defects, just as grain boundaries and surfaces. We have an unavoidable combination of two kinds ofdefects here. Three-dimensional defects are always surrounded by two-dimensional defects. That is the reason why
nucleation is always difficult as we shall see presently. Go ahead, if you like; or jump to the science module.
Phase boundaries come with unwanted energy. We have already ascertained that the crystal hates them just as
much as it hates grain boundaries. It doesn't want them at all. However, while it could get rid of grain boundaries inprinciple if not in practice, it cannot get rid of phase boundaries as long as it wants precipitates.
We will learn presently that in certain conditions the crystal needs to have precipitates for achieving nirvana. But you
can't have precipitates and not have phase boundaries just as you cannot have your cake and eat it. Compromises
are called for.
As a last and now rather trivial point, we realize that when a precipitate grows, its phase boundary has to moveoutward and its total area increases. Here we are again: movement of our two-dimensional defects occurs quite
often and it needs atoms to be mobile for that.
Now the time has come that we can dare to give the last defects on out list a thorough look: one-dimensional defects or
dislocations . These defects, while crucially important for sword making (and the whole metal-bending industry plus
semiconductor industry) are also the most difficult ones to come to term with—so I saved them till the end.

Iron, Steel and Swords script - Page 124

5.4 Weird Denizens of the Defect Zoo

5.4.1 The dislocation
I can no longer avoid to introduce you to one-dimensional defects. There is only one kind: the dislocation.
A dislocation, when you first meet one, appears to be rather fascinating but weird. You don't know how to handle it,what it is good for, and what to do with it. It's just like a new-born baby. So let's just make one (a dislocation, not ababy). That's relatively easy, even if you don't know exactly what goes on during the first few tries. Go through the
moves a few times, and you will get the drift, just like - well you also get this drift.
First we look at a schematic drawing of a three-dimensional perfect crystal as shown below. It's schematic because I
spared you (and me) all the atoms inside the crystal. It's also a cubic primitive element crystal that doesn't really exist
but is easy tro draw. Since just showing atoms is a bit confusing, I also indicate some particular planes in blue.
Here is a schematic
perfect cubic primitive
crystal .
One plane of atoms ismarked in light blue.

The crystal is clamped
into a vise and subjected
to some shear stress (redarrows).
The shear stress isapplied because we try tomove the upper part to theleft.
Generating a dislocation; part 1
We put our model crystal into a vise and now press like crazy on the upper right hand part. Bang it with your hammer if
you like, but the stress distribution generated in this way tends to be a bit messy (the red arrows would have different
lengths and would not be exactly at right angles to the crystal plane) .
Essentially we want to move or shear the upper part of the crystals somewhat to the left. If enough force, pressure,bang, or to call it by the correct name: stress is exerted on that outmost plane of atoms, it will eventually do aninteresting thing as shown in the next picture of our little comic strip:
The upper part of ourschematic crystal has yieldedto the shear stress. The
outermost plane of atoms has
curved inwards and connectedto the atoms in the lower part.
There is now a step and one"half-plane" of atoms ends
inside the crystal.
A dislocation has been
generated.
Keep stressing and thedislocation from above will
move through the crystal as
shown.
For simplicities sake we are
only looking at the front sideof the crystal.
Generating a dislocation, part 2, and moving it

Iron, Steel and Swords script - Page 125

The outermost plane with all the atoms on it is squeezed so much to the left that it eventually squeezes the neighboring
planes of atoms so much to the left that the bonding between one row of atoms snaps. The outermost plane takes thepart of the second plane, bonding with the atoms below. The second plane then ends inside the crystal.

We have generated a dislocation!
To be more precise, we have generated a particular kind of dislocation, called an edge dislocation.
If we keep pressing, the dislocations moves. The ending plane of atoms joins up with the plane next to it and thus
moves deeper into the crystal. The animation shows that schematically, but be aware that this happens all along aline at right angles to the screen..
What an edge dislocation deep in a crystal finally looks like is shown below in a thee-dimensional rendering .

Perspective view of an edge dislocation
If we keep pressing, the dislocation will move all the way from left to right, finally emerging on the right (look at the
animation). The net result is that the upper part of the crystal has been displaced relative to the lower part.
In other words:

The crystal is now plastically deformed!
In yet other words: We have moved a big object—half a crystal—not in one fell swoop that would have required tobreak a lot of bonds and thus a lot of energy, but step-by-step, with rather little effort. We have sheared off the top
relative to the bottom and that's why we call that kind of deformation a shear deformation , the kind of deformation
you get when you exert force parallel to a surface.
Dislocations can only produce shear deformations and never what we call normal deformations, the kind of
deformation you get by pressing normal to the surface on things. This link illustrates and explains that in moredetail.
Mother nature, of course, has discovered the principle of moving big objects the easy way long ago and implemented
many variants of that basic principle.
In our case we want to move the whole top of the crystal to the left. The idea is not to move the whole body withbrute force, but only small parts of it at any given time with far less effort.
To say it a bit differently: Localize a certain deformation in a small part of the body and then move that "defect"
through the body.
The following pictures show this principle for two biological objects and a man-made object (big rug). In all cases it
is far more efficient to move a "fold" through the object than the whole object. In crystals, dislocations do just that.

Iron, Steel and Swords script - Page 126

Moving big things with little effort
The basic principle in all cases is to move a localized
defect through the structure rather than moving thewhole structure at once.
Crystals knew all along, for the better part of 10 billion years, that life with defects like dislocations is much easier thanbeing perfect.
Humans, however, did not figure out that dislocations are absolutely essential to sword forging before 1934; we shallsee why in a moment. About 3.000 years had to pass for iron technology, and far more for general metal
technology, before we first understood what was going on when "bending" a metal. Dislocations are not only
essential for sword forging but for all the bending done by the "metal bending industry, as we call our still largest
and most important industry. Compare that to the first "use" of electricity by Volta around 1770, and a full-fledged
industry based on an almost complete understanding of electricity around 1900.
Dislocations are also extremely important for most of semiconductor electronics because there you must not havethem! Since you can only avoid something if you know what it is, silicon technology would be impossible without athorough knowledge of dislocations (and other crystal lattice defects), including how one can avoid having any in thesilicon wafers one starts with, and how not to produce them during processing.
Nevertheless, lots of peoples missed the big moment when Taylor, Polyani and Orowan discovered dislocations in
1934.
Worse, it took even until about 1960 before dislocations became common-place in scientific and engineering circles.
The big breakthrough was the invention of the transmission electron microscope (TEM). Do you know who inventedit?
I thought so. Go to this link. Do not collect 100 Dollars.
Anyway, since about 1960 one could see dislocations, and seeing is believing.
I will allow that a lot of people were a bit distracted beeen 1930 - 1950. Some other events like the Second World War
happened in this period of time and no Noble prizes were awarded. After the war, lots of Nobel prizes went to the heroesof atomic and nuclear science who unveiled major secrets of nature and produced atom bombs on the side. That wasfine. It is nevertheless inexcusable that no Nobel price was ever awarded to the scientists who dug down to the veryroots of mankinds most important technology.
The Nobel price committee tried to make up for this oversight by awarding a Noble
price in 1986 to Ernst Ruska (1906 - 1988). He was one of the heroes around theinvention of the electron microscope and in 1986 the only survivor from the heroic
times when dislocations and other defects in crystals were discovered and we
finally understood what is going on inside a metal when you bang it with a hammer
or work with it in any possible way.
So if you, like me, haven't been awarded a Nobel price so far, you are in very goodcompany.
The special module gives you an idea of the people who were instrumental forunderstanding sword forging.

Advanced
Link
Dislocation"Heroes"

Just to make sure, let's look once more at how dislocations achieve plastic deformation in a schematic way.

Iron, Steel and Swords script - Page 127

1. Formation of a small 2. Moving thestep by generating a
dislocation
dislocation.
through the
crystal. The
upper half has
slipped some.

3. Emergence ofthe dislocationon the otherside, after thedislocation has
moved all theway through the
crystal. The
upper part hasslippedcompletely

The three major steps in plastic deformation as seenfrom above and sideways.
We produce a dislocation by pressing as shown below (or above); next it moves through the crystal. When it emerges
on the other side, the total effect is that we moved all the atoms in the upper part of the crystal with respect to the lower
part by one atomic distance. As long as the dislocation is still inside, only parts of the upper half has moved.
Did bells ring in your brain? Did you note the magic word? Here it is: "we moved all the atoms". We moved atoms
with a dislocation!
Moving atoms, I'm sure you will recall, was at the root of changing something in a crystal and that was the key tochanging properties. The magic word was diffusion, or the random movement of atoms by some mechanism.
With a dislocation we move a lot of atoms too, but pretty much in lockstep , the exact opposite of random atom
movements in a diffusion process. We shall call this kind of moving atoms around a military movement. Moving
atoms around individually and at random by diffusion, we then shall call a civilian movement on occasion.
The dislocation itself is the region where things don't fit anymore. It is a line defect,with an extension in just one direction. Along the dislocation line, atoms would not see
their usual environment, so we have a one-dimensional defect.
There is far more to dislocations than I can relate in this introductionary
subchapter. The (two) science modules give a small taste treat of some of the moreelementary stuff encountered when looking a bit closer at dislocations.
Now get ready for the climax!

Iron, Steel and Swords script - Page 128

ScienceSuper
ModuleDislocation"Theory"5.4.2 Dislocation, Plastic Deformation and Hardness
We are getting close to our first climax (we will experience multiple ones in due course, something you can lookforward to). Here it comes.
Read the following sentence out loud to yourself or whoever you can force listening to you, and then repeat it:

Plastic deformation of all crystals
is done by moving dislocations
through the crystal!
Now stop hyperventilating and commence thinking.
Excuse me? You don't think that this is a Big Deal? You are wrong. It is a big deal. We shall see why
presently.
But I actually like you to be a bit sceptical. Let's go through some of the questions that should have come to yoursceptical mind:
First question: "You must be kidding! I might accept that one of those things, after running through the length of mylarge iron crystal, makes a little step when it emerges on the other side. But his step is tiny! It is obviously just thesize of an atom and that would look small even at million-fold magnification. I assure you that if I bang a piece ofiron with my hammer, you will see the result with your unaided eye"!
Answer: You are absolutely right. If you bang a piece of iron with a hammer, you don't need a microscope to
see the deformation produced. Still, your piece of iron changes its shape only because dislocations moved
about. It's simply a hell of a lot of dislocations that moved about, and their effects add up! At least a few million
dislocations must move to make a dent of just about a mm. Actually, a lot of the dislocations that react to yourbanging with your hammer will move somewhat but will not come out on the other side. They get stuck inside.
We have seen them with an electron microscope.
A good way to get some idea of how many dislocations are around in your crystal is to measure their total
length. You may find something like 10.000.000 cm/cm3, or a total length of 1000 km of dislocations inside a
cm cubed. Now for you Americans: Around 600 miles in a crystal the size of a sugar cube. With that many
dislocations you get visible results!
Second question: "OK—but what I get if I bang my piece of iron with my hammer depends very much on how hard I
bang. If I'm gentle, it might not deform at all—despite all those dislocations in there. So how about that?"
Answer: You are right. And your question is stupid naive, you could know better. Look at the stress - strain
diagrams I gave you! Plastic deformation commences as soon as the yield stress is reached. For lower
stresses you only have elastic deformation. What that means should be clear:

The yield stress is the minimum
stress required to make dislocations moveSo, yes, you do need to bang with some force if something should happen. The harder the material, the morebang you need (remember?).
Third question: "Fine. But where do all these dislocations come from? Does the crystal make them to achieve
nirvana, like vacancies?"
Answer: No! Never ever. Crystals don't like to have dislocations anymore than they like grain boundaries or
precipitates. They would rather do without them.
But most crystals are not born perfect and with only a few exceptions they always contain dislocations, like itor not.
The big exception, you guess it by now, are the huge man-made dislocation-free silicon crystals we use forelectronics. They are completely free of dislocations and as close to a perfect crystal in a state of a nirvana asa real crystal can be.
In all natural crystals, including single "gem stone" crystals, all poly crystals, and pretty much all other manmade single crystal besides silicon (and germanium (Ge)), there are always dislocations.
In the "martensite" part of hard steel (we'll get to that), you have a huge number of them. Their total length within
one cm3 would cover the distance earth - moon several times!

Iron, Steel and Swords script - Page 129

If you think that is amazing or just plain unbelievable, consider: The length of your DNA molecule is a few
meters, and the whole thing is cramped into a small nucleus just a few µm cubed. In terms of length per volume
it's comparable to dislocation length in heavily deformed crystals.
Fourth question: "Still, one possibly could have crystals with many dislocations and crystals with not so many.
Shouldn't they behave differently if I bang them?"
Answer: Yes, they should behave differently. And that's what they actually do.
The difference, however, would be only noticeable at the very first moment of impact. That's so because
dislocations are like rabbits. They multiply rabbitly if you don't watch them (I know what I'm talking about; mydaughters were into rabbits for many years). So when iron with just a few dislocations is banged with ahammer, enough dislocations will be made rather quickly on the moment of impact, and you will hardly notice a
difference to iron with lots of dislocations.
Now if you let me do a controlled experiment with my tensile test machine. Then you can actually see what
happens, this is shown in the figure below:

Stress - strain diagram of specimen without andwith dislocations
The dark-blue curve is what you get if you start with noor few dislocations. If you stop the experiment rightafter the peak, and then repeat it with the predeformed specimen, you get the red curve.
In the most extreme case, when you pull a completely dislocation free silicon crystal at elevated temperatures
where it is no longer brittle, we find a rather large yield stress in the first experiment. We simply need morestress in this case then necessary to move dislocations because we first need to to produce them.
After the first dislocations have formed, they rapidly multiply and the stress needed for further elongation comes
down to substantially lower values compared to the yield stress needed to initiate plastic deformation.
If we stop pulling the crystal right after the peak that signifies dislocation production, the specimen looks prettymuch the same, it is just a tiny bit longer. It now contains a lot of dislocations and when we take it and repeat
the experiment, it behaves quite "normal" now. The yield stress is much lower and there is at best a small peakat the onset of plastic deformation.
Fifth question: "Good enough" you might say, "but when I work iron, I can give it any shape. With your dislocations
running through, I would just get steps on one side".
Answer: True, but my dislocations can run through the crystal in many ways.
In fcc and bcc crystals there are actually 12 different possibilities or "glide
systems", only in hexagonal crystals you have less than that (3 or 6,
depending a bit on details).
From tricky math (euphemism for "I don't know how to do this") it can beshown that you can get any shape if you have at least 5 different possibilities ofshearing your work piece. So we have no problem for bcc or fcc iron.
Hexagonal crystals now, like magnesium (Mg), cobalt (Co) or zinc (Zn); they
have a bit of a problem. And sure enough, hexagonal crystals tend to be lessductile, harder to get into shape, and easier to fracture eventually as wealready ascertained early on in the context of the Charpy test. We haveanswered another "why" question.

Illustr.
ModuleGlidesystems

Now comes the sixth and tough question: "One and the same piece of iron can be soft or hard, depending what I,
the smith did to it. So if I hit some steel with my hammer, the results can be quite different. Shouldn't it be always
the same, if all that happens is that I make dislocations and move them through the crystal?"
Answer: The answer can only be a resounding: No! It should not be the same.

Iron, Steel and Swords script - Page 130

The reason is that it may be easy or difficult for a dislocation to move through its crystal. If dislocation
movement is so difficult that they can't move at all, the crystal is brittle, no plastic deformation can take place.
That's why there are perfectly brittle crystals. The have dislocations like all crystals but the buggers just can't
move (at low temperatures).
We have the following easy relations:
Dislocations can move easily and cover large distances: The material is ductile and soft.
Dislocations cannot move easily but still cover large distances: The material is ductile and hard.
Dislocations cannot move easily and get stuck after moving a bit: The material is still a little bit ductileand hard but comes across as rather brittle.
Dislocations cannot move at all. The material is completely brittle
Now get ready for the next climax:

Hardening iron and steel (or any metal
for that matter) simply means to put
obstacles in the way of the dislocations,making it harder for themto move through the crystal.
The final seventh question: Is it really true? Are you really sure that, to quote you: "Plastic deformation of all
crystals is done by moving dislocations through the crystal!"?
No. I'm not. Sorry. There are two more mechanisms, related to each other, that
could produce plastic deformation without dislocations. They are the(important) exceptions to the rule and called:
Twinning deformation.
Shear deformation.
There are people out there who would fight me for that statement, claiming thatin both cases we have dislocations at work, too. In a formal way they are right.
In principle, however these modes of plastic deform our crystal, exactly thesame deformation could be achieved by moving special dislocations around ina special way.

ScienceModuleTwinning /Shear

But it also can be done without dislocations; the results in the end are identical. Since whatever happens
proceeds real fast, nobody has ever seen it happening and thus we don't know "the truth" from experiments. We
only know the results of what happened—and quarreled about the detailed mechanism. It does appear,
however, that the "no dislocation" faction is carrying the day
If you ever read anything about hard steel, the term "martensite " came up for sure. Martensite forms by a shear
transformation , whatever that will turn out ot be. I'll look into that much later.
More about the essence of twinning and martensite formation can be found right now in the science module.
Now we are done. If you are still there, you have arrived at a first summit of our long uphill climb. You now know thebasics of engineering properties like hardness. Time to open a bottle of the good stuff.

(Good stuff break)

Back to work. We now can start answering a lot of those "why " questions in a simple way:
Why does adding a little bit of carbon make iron much harder?
Because it's making dislocation movement more difficult.
Why does deforming an initially soft piece of steel make it much harder? (look at the relevant figure again).
Because during the first deformation you produced a hell of a lot of dislocations and many of them did not moveout of the crystal but are still there. They are now hindering each other at moving.

Iron, Steel and Swords script - Page 131

Why is the steel soft again after tempering it for some time at high temperatures?
Because you produced vacancies that make the atoms mobile. The crystal now can go to work, trying toachieve nirvana again. It rounds up all those defects that tie down the dislocations and kicks out most of thedislocations too, if given time. The remaining ones now can move with ease.
Why do nanocracks in ductile materials not induce instantaneous fracture if acritical stress is surpassed; look at the first science module about fracture toappreciate that question.
Because plastic deformation blunts the crack tip. This is not so obvious, so
there is an extra science module about thisWhy do some materials (including some steels) show the "ductile-to-brittle
transition syndrome, i.e. become more brittle at lower temperature withsometimes disastrous consequences?

ScienceModuleFracture
Mech. II

Because more vigorous vibrations of the atoms in the crystal (that's what temperature is, remember?) helps
dislocations to move. If its cold, they move more sluggishly and my not be fast enough to "outrun" spreading
nanocracks that induce fracture.
Let's finish this paragraph by looking at real dislocations (with a transmission electron microscope or TEM).

Dislocations in silicon at medium magnification(TEM)
I like these pictures because I took them many years ago. We are looking through the thin silicon specimen.
Dislocations are imaged as black lines. The three-dimensional dislocation arrangement is projected on a twodimensional screen, just like the X-ray pictures of your bones that your doctor shows you.
The top pictures show a kind of dislocation nest or cluster in otherwise perfect silicon. Imagine it as a tangle ofdislocation lines in three dimensions. If you estimate their total length, you find a lot of length in a very small
volume (look at the scales!).
By the way, these dislocations are there because somebody touched that piece of silicon ever so lightly with asharp needle, making a little indentation—the white rectangle in the center. This is a bit like a hardness test,
just on a much smaller scale. That produced the dislocation tangle—and completely killed a microchip!
The lower picture shows dislocations in silicon that were produced because a thin layer of something produced
some stress. At room temperature, this only induces some elastic deformation. During some processing athigh temperatures, however, silicon became sufficiently ductile to allow production and movement of
dislocations. Needless to say that this wafer goes into the garbage bin.
Iron, Steel and Swords script - Page 132

Of course, we can also look at dislocations at atomic resolution with HRTEM (always provided the dislocationline is "edge-on"). Here is a picture:

Dislocations in silicon at atomic resolution
Red lines outline the ending crystal planes. Compare
to the schematic picture of a dislocation!
The lower picture shows a HRTEM picture of dislocations in silicon portrayed "edge-on" just as drawn in thepreceding chapter.
I love this picture too because not only did I take it in 1979, it also happens to be once more among the very
first, if not the first HRTEM pictures of dislocations. It took until about 1975 before electron microscopes weregood enough to enable us for the first time to see the crystal structure directly. The red lines indicate the latticeplanes that end at the dislocation lines.
What you can see quite clearly is that even an enormous density of dislocations (that's what we have here)
does not really disturb the crystal all that much—you hardly notice them if you don't look closely.
Why do I show pictures taken from silicon and not from iron or steel samples? Because it is far more difficult to get
this kind of pictures from (magnetic!) iron. You also don't get pictures as clear as the ones shown here, since in iron
there is always a lot of other stuff around.
Also, using my own pictures, I don't have to bother about getting copyrights from all over the place.
What we have learned so far applies to the deformation of all crystals, not just iron and steel. If we would be
discussing swords made from most other metals, we would be almost done now with the basics.
Iron, however, still has several additional tricks up its sleeves. If you think what we covered so far wascomplicated (but enlightening, I hope), you're in for a surprise:

The complications start now.

Iron, Steel and Swords script - Page 133

5.5 Mixes

5.5.1 What's in a Name?
What are You?
"The complications start now", I just threatened (or promised) at the end of the preceding chapter. That's because so far
I only dealt with simple and rather perfect crystals that contained some comparatively simple defects. What we will do
now is to consider mixes of all kinds of materials.
The first complication that comes up are the names for complicated materials. Let's ponder a few easy questions to see
what I mean:
What do you call the following things (the first four are crystals):
Aluminum oxide or corund (Al 2O3) containing a few substitutional chromium (Cr) or titanium (Ti) atoms?
Copper (Cu) mixed up with 10 % tin (Sn)?
Silicon with a tiny bit of substitutional phosphorous (P) or boron (B)?
Iron containing about 1 % of carbon (C) ?
A human with a Y chromosome instead of an X chromosome?
You do not call it what it actually is: the ideal thing plus a defect. You call it:
It's ruby or sapphire, respectively, instead of corund with a substitutional amount of extrinsic point defects.
It's Bronze, instead of: dirty copper.
It's n-type or p-type silicon, resp., and these two basic silicon versions are at least as different as males andfemales. More generally we call it doped or extrinsic silicon but never (intrinsic) silicon with some point
defects.
It's Steel instead of iron with some carbon.
It's a male instead of: defective female.
In other words: where exactly is the change-over from copper (Cu) with some impurity tin (Sn) atoms to the copper - tin
alloy that is called bronze? From slightly dirty wrought iron to steel?
In yet other words: When do we change from one reference system (iron, copper) to another one (bronze, steel)?
The answer is simple: there is no clear answer. These letters are black. These here are grey, and those are white.
Are the ones here grey or still black? They are actually a tiny bit grey. You could call them ideal blackcontaminated with a tiny bit of white. In the next sentence the degree of "white contamination" changes slowly from
0 % to 100 %.
I n this s entence the whit e increa ses slow ly. OK - once more with a different back ground color:
I n this s entence the whit e increa ses slow ly
At which letter is the turnover from contaminated black (or white) to grey? There is simply no way of telling! It is amatter of "taste" or convenience.
I'm talking about names for certain materials and mixtures of materials. In essence, there are many words for special
materials, and there is no harm done in using them whenever the meaning is sufficiently clear. Before I introduce someof the more important names and classifications of materials, I want to point out that the problem of defining a kind ofclear boundary for a mix of things, with pure "A" being on one side, and pure "B" on the other, is very common and thesource of many misunderstandings not only in science but also in society. Here are some examples:One vacancy (= white) is a point defect and so is a double vacancy—two vacancies next to each other. A
tri-vacancy will still be a point defect but a 45.631-vacancy we call a void (= black), and this is a three-dimensional
defect. Where is the switch-over?
Copper (Cu) is definitely a metal , so is lead (Pb). How about their neighbors in the periodic table? To the right ofcopper we find zinc (Zn), gallium (Ga), germanium (Ge), and germanium is most definitely a semiconductor. Whatabout gallium?
Above lead to we find tin (Sn), germanium (Ge), silicon (Si). Once more we move form a metal to a semiconductor.
Is tin a metal? It is often called a "semi-metal". This is just to show that even a name like "metal", absolutely
unambiguous as you might have thought, has a "grey" side. Nevertheless, we sure know a real metal (= white) or
non-metal (= black) when we see one. How about the grey ones?
"Soziale Gerechtigkeit" (social fairness or justness) is a big word in German politics. It boils down to money beingtransferred from the more prosperous to the more disadvantaged people. When will politicians consider that social
fairness (= white) has been established, considering that right now it is not? The relevant department of the Federal
Government presently transfers about 40 % of the total (tax) income from rich to poor. By (almost) general consent,
this is not enough. How can you find the right number?

Iron, Steel and Swords script - Page 134

In today's (May 2012) newspaper I read in an interview with the art director of a huge art show in Kassel, Germany:"There is no fundamental difference between women and dogs. Neither between dogs and the atoms of my bracelet.
A tomato is the cultural product of the tomato plant (and thus art)".
Well. Just because some women, if compared to some (female) dogs....
I think I made my point.
A knife has a short blade and and sword a long one. Then there are long knifes and short swords. At what length,
exactly, changes a long knife blade into a short sword blade?
Now let's look at some notations concerning materials in this context. This is essentially an exercise about the namesthat signify the "nature" of the objects we encounter in daily life. It is unavoidable that we always encounter the "black white" problem from above, and that means that you have to take these words with a grain of salt.
The first list of names concerns, in a general way, the structure and composition of materials.

Names Related to Structure and Composition
Metals, Non-Metals, Natural Materials
This is the classical threesome, used in all old materials science text books, with examples like:
MetalsIron (Fe)Copper (Cu)Gold (Au)Bronze
brass
Steel
..

Non-Metals
Glass (dirty Si2O)
Quartz (SiO2)
Ceramics like Al2O3, ZrO2,
UO 2
Polymers
Graphite

Natural Materials
Wood
Coal (very dirty carbon)
RubberSand, gravel,
Rocks,
MarbleGemstones

Designations like "metals" or "rocks" do have some value, of course, for communication with other people.
Everybody has some idea what you are talking about. I will keep using words like "metal" and so on as long as it isreasonably clear what is meant.
Otherwise forget that classification system. The world is no longer as simple as it used to be.
AlloysThe name is typically (but not exclusively) applied to mixes of metals with a whole range of concentrations. Mostly
one element dominates, and we talk then for example about copper alloys.
If we only consider alloys of copper and one other element, we have, in principle about 90 possibilities to makecopper alloys, since we have 92 elements. In practice, a number of elements will not alloy with copper (e.g. thenoble gases) but there is still a large number of possibilities if we only consider all the other metals as alloying
partners. For any combination Cu - metal X, we can look at a whole range of concentrations for X.
Then we can alloy not just one, but several other elements with copper (always making sure that copper accounts
for more than 50 % of the mix, so we are justified to call it a copper alloy).
In other words: While we have "only" 92 elements (about 70 of which are metals), we can produce close to infinitely
many combinations. These include chemical compounds like Copper chlorides (CuCl, CuCl2, Cu3Cl2(OH)4,...) for
exactly defined concentrations of X that are neither alloys nor metals, but also an infinity of alloys that are metals more or less (see above).
Chemistry, as a discipline worries more about well-defined chemical compounds; alloys are more in the domain ofMaterials Science.
How could you tell if given substance is an alloy (= white) or a chemical compound (= black)? A simple carbon steel
would be counted among the alloys, but if you look at it closely (at room temperature) you find that it actually a mixof the chemical compounds iron (Fe) and cementite (Fe3C).
To some extent we avoid the problem by giving some special mixes names. "Bronze" for some copper alloys,"brass" for some others. "Steel" is the name for all kinds of iron alloys as long as iron is being dominant. It might bedifferentiated by qualifiers like "high-alloy steel, low carbon steel, ultrahigh carbon steel, ... , but those are justnames giving an idea of what we talk about and not precise definitions. Where, exactly would you put the switchover between low-carbon steel ("white") and medium carbon steel ("black")?
Chemical Compound
Well - I already gave you that right above. In a proper (= white) chemical compound the ratios of the atoms involved
have precise (integer) numbers. There is some "grey" here too, but I won't go into that.
I might add that chemical compounds can have properties that are radically different from that of their constituents.
Hydrogen (H) and oxygen (O) are gases, liquid H2O is known as water, solid H2O we call ice. Chlorine (Cl) is adeadly gas, sodium (Na) is a (dangerous!) metal. NaCl, known as (rock) salt, is a relatively harmless and useful
insulator.
Iron, Steel and Swords script - Page 135

In contrast, copper alloys like bronze (typically with tin (Sn) as partner) or brass (zinc as partner) are also quite
different from pure copper, but not radically so.
Composite Materials
Composite materials consist of a mix of at least two other (solid) materials on a scale much larger than the atomic
scale. Usually the term is used in connection with materials where the constituents where deliberately mixed byhumans and not by nature. Sometimes the term Compound material is used for composites but that is not a goodname and should be avoided.
Examples are:Concrete, consisting of stones embedded in cement. Cement is already a composite material in its own
right; stones might be. already a composite material. Add some steel to concrete and you now have acomposite material with at least three different constituents.
And yes, the constituents of a composite material could be alloys, chemical compounds or othercomposites. "Stones", for example, are quite often composites of different minerals.
Carbon or glass fibers in epoxy, i.e. the stuff used for modern air planes, Formula 1 cars, boat hulls and soon.
Composite bows, containing at least two different kinds of wood (plus things like sinew, horn, ...)
Wood; actually a natural composite material consisting of cellulose and lignin.
Composite swords made at least from two different kinds of steel. I won't call them composite swords,
however, since this produces wrong associations.
Single Phase and Multi Phase Materials
A phase is an expression of some material that is well-defined and uniform on an atomic scale. A chemicalcompound like water or rock salt is always a single phase but more complex stuff could also be a single phase. We
are going to spend a lot of time on that so I won't say more at this point.
A multi-phase material is a composite of several phases. In contrast to what we generally call composites, theingredients cannot be other composites and they usually "make themselves", for example when steel cools down.
Names for Properties and Functions
We have a different set of names for materials that concern not so much their structure but primarily their properties andfunctions.
Examples are
Superconductors, Conductors , Semiconductors, Insulators, Dielectrics. These names refer to directelectrical properties.
Ferromagnets, Ferrimagents, Paramagnets, Diamagnets. You guessed it.
Thermoplasts, duroplasts, elastomers for basic kinds of polymers.
In the world of steels there are many qualifiers relative to some function or property: Stainless steel, austenitic
steel, machining steel, tool steel,Names for Processing
DopingDoping typically means that you introduce small amounts of well-defined foreign atoms into a semiconductor; mostly
as substitutional impurity atoms. However, in other branches of Materials Science, the word "doping" might also be
used for relatively large amounts of some stuff introduced into some material, for example when "organic
semiconductors" are concerned.
Quite frequently the word is simply used to refer to an electronic property. "My gallium nitride (GaN) is n-doped", forexample, only refers to an effect of doping and leaves open how it was done.
Doping typically changes the properties of the material more or less in a way you like.
Never confuse doping with:
Contamination
Pretty much the same as doping - getting some other atoms in there - except that you don't like it. The properties
may change a lot, just as with doping, but not in the way you want it.
Ceramics
You might wonder why I list "ceramics" under processing. The reason is that the word typically refers to materials
that have been made by sintering, a powder processing technique. It is, however, an ambiguous designation. Somepeople call everything that's brittle a ceramic, for example.

Iron, Steel and Swords script - Page 136

Then we have words like alloying, tempering, annealing, normalizing, quenching, ... . Sometimes the meaning is rather
general, sometime it is specific.
I won't go into this any more except to point our that some names for steel hint at the processing involved, for example"maraging steel" (short for "martensitic aging" steel) or "austempered steel" (short for "tempering in the austenite
region").

Iron, Steel and Swords script - Page 137

6. The Iron-Carbon Phase Diagram
6.1 A Map for Steel
6.1.1 It Takes Two to Tango
6.1.2 Reading Phase Diagrams: Single Phases and Boundaries
6.1.3 Reading Phase Diagrams: Mixed Phases and Boundaries

6.2 Things Get Complicated
6.2.1 Creamy or Chunky?
6.2.2 Solidification and the Art of Casting
6.2.3 Welding with Hammer and Fire

6.3 Surprise?
6.3.1 Nirvana once moreIron, Steel and Swords script - Page 138

6. The Iron-Carbon Phase Diagram
6.1 A Map for Steel

6.1.1 It Takes Two to Tango
Famous First Words
Perfect crystals are boring. They have the properties they have, and you can take it or leave it, but you cannot change
them without destroying perfection. What we want in a first step now are almost perfect crystals that contain some
defects.
Even diamonds (relatively perfect carbon single crystals) are more valuable if they
contain a few defects that give them some color. A perfect aluminum oxide (Al2O 3)
crystal is not even seen as a gemstone. Contaminate it with a tiny bit of chromiumor titanium, and now it's a ruby or a sapphire, respectively.
Gemstones are quite useful for obtaining favors from desirable ladies, so I give you
a special module that might help you to score without having to actually buy one ofthose expensive baubles.
You might, for example, expostulate about the fact that the first Laser was madefrom a (synthetic) ruby, and that the decisive thing for getting rubies to be red is tohave a few chromium atoms in there, dissolved as substitutional point defects in anotherwise boring aluminum oxide crystal.

Advanced
Link
Gemstones

You should be able to score without actually having to buy a ruby, in particular if the female in question is of theAngela Merkel type 1).
If I'm right and perfect crystals are boring, you might wonder why we are going through great pains to make silicon
crystals as perfect as possible? It's for the same reasons why some time ago my forebears, and possibly yours too,wanted their women to be "perfect", i.e. virgins: you want to destroy the perfection in a controlled way. As far as
silicon is concerned, doping it with suitable impurity atoms in precise amounts doesn't make much sense if all
kinds of other unknown defects have already left their traces in there.
It needs two to tango, and if we want things to get a bit more interesting, we must bring our prissy perfect crystal into
intimate contact with atoms of a different kind.
Making swords or any other steel objects in antiquity meant to put at least one other kind of atom into the rather
pure iron. Typically this was carbon but there was also a lot of phosphorous (P) steel. It matters very much exactly
how much carbon (or phosphorus) atoms are put into the iron crystal, and what they are doing in there.
It also matters very much what else is in there in terms of defects.
I'm talking about the core process for much of materials engineering. The best example besides iron and steel
technology is semiconductor technology. It's all about defect engineering.
If we make microchips from perfect silicon crystals, we put a precisely defined number of phosphorous (P), Arsenic(As) or boron (B) atoms in precisely defined tiny volumes (about 0,1 µm2 square and 0.01 µm deep). More, we needto make sure that the crystal accepts and keeps them there as substitutional impurity atoms. We also want to be
sure that there are no other defects present.
Things are far more relaxed with iron and carbon. Nevertheless, when we put carbon atoms inside iron crystals, thekind of their arrangement is important for what we have in mind .
Crystals, however, have a mind of their own and usually don't like what we do to them. They will fight back. They always
stick to the second law in letter and spirit as much as they can, and they don't care about your desires. It's like having avirgin who wants to be a nun.
Whenever you put foreign atoms inside some crystals in some particular way, it might not be the way they wantthings to be. Then they will do their best to rearrange everything in such a way that they get as close as possible tonirvana once more. All they need is some temperature and some time to move atoms around, and you should bequite aware of that.
The first order of business now is to find out what a crystal, if left to its own devices, will do with those foreign atoms you
doped, contaminated or alloyed it with
So ask yourself: If the foreign atoms cannot be gotten rid of, what would a nirvana-seeking crystal do with them?
Well, we have dealt with that already. In an ideal world or crystal, surplus extrinsic point defects precipitate or are
stuffed into grain boundaries. How about in reality? Reality meaning that we now look at some defined material A
that contains a defined and possibly large amount of a material B at a defined temperature T.
In other words, we are now looking at the whole range of compositions: from pure A via alloys or chemicalcompounds of A and B all the way to pure B.
Iron, Steel and Swords script - Page 139

What are we going to find for, say, 86,5 % B alloyed with 13,5 % A at 675 0C or 395 0C? A and B could be iron(Fe), carbon (C), nickel (Ni), gold (Au) copper (Cu), molybdenum (Mo) silicon (Si), ..., everything from the periodic
table.
With about 90 elements in the periodic table, we have 90 × 90=8100 basic possibilities and for each of these
possibilities the whole concentration range. There is a lot of work ahead!
Never fear. Material scientists and engineers have already done the work. They came up with an ingenious way toillustrate what happens in all these cases (and more):

They invented phase diagrams
Phase diagrams are for second-year students of materials science what garlic is for vampires: they scream and run forcover when we whip one out during a lecture course.
They have good reasons for being scared by phase diagrams but that need not concern you, the reader.
Have you ever looked at a map before you go places? I bet you did. On your map you saw major and minor streets,
forests, cities and towns, railroads, rivers, lakes and oceans. The map even told you how to get to your destination,
including possible alternative routes.
What an outrageous lie! You certainly did not see roads etc. on the map! All you saw were lines of various colors
and styles, shaded and colored areas, and so on, printed on a piece of paper.
"Seeing" roads and rivers and finding your way resulted from your interpretation of map symbols, based on some
simple rules that about half of humankind figured out early in life.
First you find your present location on a map, which in case of doubt is given by two numbers: the vertical (northsouth by convention) and horizontal (west - east) distance from some zero point. You also may call these numbers
latitude and longitude if you get your scales right.
Then you figure out how to get from where you are to where you want to go. The map also tells you what you willencounter on your chosen path. Maybe there is a river to cross, you will ride through a forest, or you encounter
some towns on the way. It's all there. All you need to know is how to interpret the symbols on the map.
Phase diagrams are pretty much the same thing. They provide a kind of map that tells you what you will find in a certain
location in the world of materials (mostly crystals) that are made from two kinds of atoms, A and B.
There is a big difference to geographical maps, however. Phase diagrams only show the ideal state of crystals, notnecessarily the structure as you will find it. In other words:

Phase diagrams show only the"nirvana" state.
A good geographic map shows slums, for example, which in an ideal world would not exist. A phase diagram, incontrast, does not show structural "slums", e.g. crystal structures that the crystal hates and would never assume
on its own. That doesn't mean that those structures do not exist.
As in a geographic map, two numbers give the starting "location" in a phase diagram. Instead of latitude and longitude
we have something different.
1. The first number gives the composition, the ratio of A : B. An example for a composition is the percentage ofcarbon in iron. 1 wt% carbon in iron is a certain composition, and so is 10 wt% tin (Sn) in cupper (Cu). These
composition actually have names: steel or bronze, respectively, but most compositions don't.
2. The second number gives the temperature T in some scale.
Both numbers are variables that could have any values. Well, not really. Temperatures below the absolute zero point do
not exist and temperatures above the melting point are irrelevant in most cases. You also cannot go below 0 % or above
100 % for concentrations, but these limits are rather trivial.
Easy enough. So why do our students run for cover when we get to phase diagrams? Because we don't just expectthat they can "read" a phase diagram, we expect that they can make one.
You can read a map? Cool—but can you make one?
Making a map of Istanbul is a lot of work and needs a lot of skill. In comparison, reading it is laughably easy. I won't
try to teach you how to make a phase diagram but I teach you how to read one. Only simple ones, of course. This
will be sufficient to find out what you can do with a phase diagram.
Enough small talk. Let's jump into the cold water (or rather a heat of steel)) and look at the phase diagram of thebinary iron-carbon system. Here it is:Iron, Steel and Swords script - Page 140

The iron - carbon phase diagram
The colors are usually not there. They only serve togive you, the smith, an idea what the work piece looks
like at the temperature indicated.
I used big words above but they are rather self-explaining, I hope. "Binary " is Latin for "twofold" and thus means thatthe system we consider consists of a mix of just two different atoms. With about 90 different elements, we have 90 ·90=8.100 different binary systems we can play with. The system iron - carbon is just one oft these.
The Basics About Phase Diagrams
Now come back - don't run away. It's not as bad as it looks. Let's go over it bit by bit.
First we note what is depicted.
From left to right we simply have the concentration of carbon in iron. At the bottom it is given in weight percent(wt %), at the top, out of the goodness of my heart, I give it in atom percent (at %) too.
We only go up to 7 wt % carbon because nothing of interest to sword making happens beyond this carbon
concentration.
Second, from bottom to top we have the temperature. On the left it is given in the absolute temperature scale(Kelvin; K), on the right, out of the goodness of my heart, I'm doing a very unscientific thing and give you the Celsius(degree Celsius; oC) and the Fahrenheit (degree Fahrenheit; oF), scale, too.
I have omitted temperatures below 600 K (327 oC, 621 oF)) because nothing of interest happens there as far as thephase diagram is concerned.
As far as sword making is concerned, interesting things may still happen below that temperature; I'll come to that
The Greek letters α, γ, and δ, the "L", and the chemical shorthand Fe3C in the phase diagram simply refer to thedifferent phases one encounters in the iron - carbon system.
The background color is a feeble attempt to reproduce the color that hot iron shows when it glows. It's red-hot
around 1100 K (827 oC, 1520 oF) and bright yellow around 1350 K (1077 oC, 1971 oF).
By the way, the color of a hot body does not depend very much on what that body is composed off. If we would heatyou, dear reader, to a temperature of 1400 K (1127 oC, 2061 oF), you would glow bright yellow, just the same as iron or
anything else. OK - I agree that you might sizzle a bit, giving off various aromas during the process of heating. But thatis not important. Whatever is left will be glowing bright yellow.
It was Max Planck, who first came up with an explanation for this strange fact in 1900 (in terms of a precise
mathematical equation), opening the gate to quantum theory and thus to Materials Science.
Now you have seen one phase diagram—for iron-carbon—but there are many more. If you think about it once more for asecond, you realize that for all materials consisting of just two kinds of atoms, about 90 × 90=8.100 phase diagrams
exist, since we have about 90 different kinds of atoms.
We actually know most of those binary phase diagrams, thanks to all these students spending a lot of time
constructing them. Coming up with a new phase diagram is a typical PhD thesis; it does take a lot of brain andeffort.
We can, of course, come up with roughly 90 × 90 × 90=72.900 tertiary or three-fold phase diagrams for materials
with three different kinds of atoms (kind of hard to draw). Iron with some carbon and some manganese (Mn) would
be a relevant example.
We have about 65.610.000 quaternary phase diagrams for materials with four kinds of atoms (impossible to draw but
possible to express in formulas), and so on.
Our common "alloy steels" of today comprise at least four kinds of atoms, usually more. You would run for cover, too, if
you suspect that you would be called upon to construct one of those.
Relax. The good news is that after materials scientists mastered the art of turning silicon crystals into
microprocessors and the like, we now command tremendous computer power and we are increasingly calculatingphase diagrams with little effort.
All you need is the second law and some good idea of how different kinds of atoms relate to each other (and, ofcourse, about 5 - 6 year of your time to learn how it's done).
Iron, Steel and Swords script - Page 141

If we just limit ourselves to the most simple binary systems (two kinds of atoms), the essential input into our phase
diagram calculations is how those atoms relate to their own kind and to the other one.
Do they only love each other ("I don't want to be close to this stranger; I want to be with you"), do they like the otherkind ("so he is a foreigner, but I just love him more than you"), or do they not give a damn ("I don't care about you or
anybody else")? If you could deal with your teenagers, you shouldn't have much of a problem with this.
If we know these relations, we can calculate precisely what the atoms of a crystal are going to do. Even so thesingle atoms may do their thing at random, we can predict with certainty what they will do as a group. Teenagers,
while being chaotic individually, are also quite predictable as a group.
So gird your loins and follow me. We will now plunge into the intricacies of the iron-carbon phase diagram and find out
how it relates to sword making.

1)

Dr. Angela Merkel, the present chancellor (or is to chanceleress?) of Germany and thus the most powerful lady on thisplanet, is a physicist by training. She is (happily!) married to Professor Sauer, a quantum chemist, who is actively
working and well known in his field. He would never even dream of playing "first husband".

Iron, Steel and Swords script - Page 142

6.1.2 Reading Phase Diagrams: Single Phases and Boundaries
Now let's go to work. First I redraw the iron-carbon phase diagram in a way that will help you to better appreciate thedifferent phases.

Iron -carbon phase diagram
Different colors denote different phases. Mixe d colors= mixed phases

What we have now is a simple rule: different phases = different colors. M ixed colors = mixe d phases. You remember,of course, what a phase is? Thanks; otherwise go back to chapter 2.3.1.
Let's start to "read" the iron-carbon phase diagram. First we pick some particular concentration ofcarbon, let's say 1,3 %. I like that concentration because it is easy to draw into the phase diagram
as a vertical line. The relevant part is shown on the right for immediate reference. Along the redline we have the same composition but different temperatures.
From 600 K (328 oC; 620 oF) and below (not shown) up to just about 1000 K (727 oC; 1341 oF) wehave the mix ed phase "blue and pink".
At 1000 K (727 oC; 1341 oF) there is a phase transformation to the mixed phase "pink andyellow".
This first phase transformation is the most important one for you, the ancient (or modern) smith.
Most of the time when you stick your work piece into the hot coals on your hearth, you do it toinduce this phase transformation. We will call the temperature of about 1000 K (727 o C; 1341 oF)
where this phase transformation occurs "the " transition temperature (usually abbreviated A1)
because it is the most important one.
If you keep going up with the temperature, another phase transformation occurs around 1170 K(897 oC; 1447 oF). The mixed phase "pink and yellow" now transforms to the pure phase "yellow".
Then, around 1550 K (1277 oC; 2331 oF), we hit the mixed phase "yellow-white" and around 1730
K (1457 oC; 2655 oF), it's all white, meaning that the phase transformation at this temperaturesimply denotes complete melting because white is the liquid phase, always abbreviated "L".
It's time to look a bit more closely at what, exactly defines a single phase . What I offered you long ago in this respect
is a bit too wishy-washy to suffice us here. So here goes.

A phase is a region of space where allphysical properties of a material(e.g. density, hardness, chemical composition)
are essentially uniform.

A phase therefore is a piece of material that is chemically uniform, physically distinct, and often (or at least in
principle) mechanically separable from its environment.
Now we know what the lines in a phase diagram mean: They denote "where", i.e. at what compositions andtemperature, a phase transformation takes place. They separate different phases or different mixtures of phases incomposition - temperature "space".
Iron, Steel and Swords script - Page 143

If we do the same procedure for pure iron (all the way to the left for 0 % carbon), we run throughthree single phases (blue, yellow, bluish) as we go up with the temperature. The small part of thephase diagram on the right shows only the first two phases.
We know already what they signify: blue = bcc (body centered cubic) crystal, yellow = fcc (facecentered cubic), bluish = bcc once more.
Of course, we can only have single phases in this case, and it's time to give them names. The
ironclad rule is that solid phases are always assigned a Greek letter. For historical reasons, aphase might have a more or less fancy name in addition. Sometimes there are even two names,
often involving dead white guys. What we have in the case of pure iron is:Blue = α (alpha) phase = ferrite = bcc iron crystal .
Yellow = γ (gamma) phase = austenite = fcc iron crystal .
Bluish = δ (delta) phase = bcc crystal once more; too unimportant to rate a name.
What we have in the case of iron plus some carbon is exactly the same. As long as you "are"within a one-phase region, shown here by one color, you have the phase going with that color. To
make that perfectly clear, I repeat the list above for iron plus some carbon:
Blue = α (alpha) phase = ferrite = bcc iron crystal with some dissolved carbon.
Yellow = γ (gamma) phase = austenite = fcc iron crystal with some dissolved carbon .
Bluish = δ (delta) phase = bcc crystal once more; too unimportant to rate a name, withsome dissolved carbon
Names like Ferrite or austenite thus do not refer to pure iron but to iron with some dissolved carbon in it. How muchcarbon that could be at some given temperature is shown by the single-phase regions in the phase diagram.
Generally speaking, the composition of single phases in binary alloys is always A (or B) with dissolved B (or A,
respectively) in it.
This is important. We must allow single phases to contain two kinds of atoms as long as they are atomically"mixed". This is, after all, the definition of a phase as given above, if you think about it. Dissolved single atoms are
distributed uniformly and cannot be separated.
Let's repeat:"Ferrite", "austenite" and so on does notmean pure iron with some specific crystal
structure, but iron with some specificcrystal structure and somedissolved carbon in it

How much carbon can be dissolved in a phase is something that the phase diagram tells you.
Dissolved means that the foreign atoms are sitting as individuals in the crystal (interstitial places for carbon in iron) insome random distribution. In other words: they are extrinsic point defects. Any point inside the blue area in the phase
diagram above (the α-phase or ferrite phase) denotes an allowed combination of the solid solution of carbon
concentration and temperature. The carbon then is definitely dissolved.
Note that if it is hot enough, the carbon atoms don't "sit" still but move around at random. They diffuse, as we calledthat process. We will also have vacancies moving around and thus the atoms don't sit perfectly still either.
Nevertheless, a snapshot would always look like our old figure with just the right number of carbon atoms showing.
The composition, in other words doesn't change by all this moving about.
So any point within the slender blue region in the phase diagram denotes alpha phase or ferrite, and ferrite always has a
bcc lattice and various but invariably small carbon concentrations (including zero) at some temperature.
Any point in the yellow region denotes the gamma phase or austenite, and austenite always has a fcc lattice andvarious carbon concentrations from zero to a maximum of about 2 % at some temperature.
The name ferrite derives from the Latin "ferrum" for iron. It is always a bcc crystal and the best it can do withrespect to dissolving carbon is about 0.1 % around 1000 K (727 oC, 1341 oF). This we call the solubility limit.
Austenite was named after Sir William Chandler Roberts-Austen, a British metallurgist (1843-1902), who
conducted extensive studies on the effects of impurities on the mechanical properties of pure metals. Austentite or
the γ phase is always a fcc crystal. It can dissolve carbon much better than ferrite - almost 2 % around 1400 K(1127 oC, 2061 oF), and still about 0,7 % around 1000 K (727 oC, 1341 oF).
The difference in carbon dissolving "power" between austenite and ferrite is at the core of steel making and blade
forging, and we will spend much time at unraveling the consequences.
Iron, Steel and Swords script - Page 144

Now let's look at the melting point of iron with some carbon in it. The line between the yellow-white and the white "L"region gives us that information. L = "Liquidus" always denotes the liquid phase (why use a simple word if there is a
Latin one?). Of course the liquid phase can also contain carbon.
The line separating the liquid phase from the other phase "below" that line gives the melting point as a function of the
impurity concentration = carbon concentration in our case here .
As I claimed long ago and explained to some extent not so long ago, the melting point comes down indeed withincreasing carbon content to a minimum of 1403 K (1130 oC, 2066 oF) for a carbon concentration just a bit above
4 wt%.
So an iron-carbon alloy with about 4 % carbon would be your ideal composition for casting iron. Why? There are
actually two good reasons:
1. First: at that composition you have the lowest melting point you will ever find in the Fe - C system. Low
melting points are good because it is not so easy to achieve temperatures above 1100 oC (2012 oF).
2. Second: this is an eutectic composition .

??? If this looks Greek to you, that's because it is.
Alright. I admit that even a decent general education in most countries does not include ancient Greek anymore.
Even one of my daughters, who did time in a classical German "Gymnasium" and certainly learned ancient Greek(together with a lot of Latin and a bit of (ancient, of course) Hebrew), didn't know what "eutectic " meant. So you are
definitely excused for not knowing that either.
I will get to it soon. But first we look once more at what happens at the 1,3 % carbon concentration I marked with a
red line in the phase diagram above.
For a composition of 1,3 wt% carbon in iron, the phase just below the line that defines the melting point is a mixed
phase, denoted by γ + L. That can only mean a mixture of solid γ phase or austenite and the liquid .
That's not as strange as it might appear: At 0 oC (32 oF) you can keep a mixture of liquid water and ice (= solid
water) stable as long as you like. Try it. You are allowed to use whisky instead of water.
Inside the (γ + L) mixed phase you can keep a mixture of liquid steel and solid steel stable as along as you like(and can take the heat). If you go to different locations inside the mixed phase region, you only change the relative
amounts of liquid and solid (lots of ice and a little whisky or lots of whisky and a little ice). But whatever you have is
still a mixed phase.
When you, the smith, make a sword blade, you have steel with some defined carbon concentration that you subject tovarious temperatures while forging it. Assume for simplicities sake that the carbon concentration doesn't change duringforging, all the heating and cooling simply means that you move up and down a vertical line in the phase diagram.
If you go above 1000 K (727 oC, 1341 oF) for carbon concentrations in the usual range (about 0,1 wt% - 2 wt%),
your steel will run through at least one phase transformation. And you will go above that temperature for sure; doingthat it is what forging is all about.
So here comes an epiphany in one line that you should read out loud:What you have on your anvil above about1000 K is a completely different material
from what you have at room temperature.

How different is "completely different"? Well, you will agree that a diamond is completely different from a lump of coal (atleast your wife will), so why should it be otherwise with ferrite and austenite?
They are two different phases of the same material (iron + some carbon) and there is no reason whatsoever that
their properties couldn't be just as different as those of graphite and diamond. Their electrical conductivities or themagnetic properties, for example are different, and so are their mechanical properties like hardness.
It's only because nobody has much use for a 1000 K hot iron wire or magnet that we don't care much about thesedifferences and are not aware of them.
Nevertheless, the lattice type, the ability to dissolve carbon, and the mechanical "hardness" and the generaldeformation behavior are quite different in ferrite or austenite. Austenite is actually a bit harder than ferrite at hightemperatures. Both phases, however, are far softer at high temperatures than ferrite at low temperature That is the
major reason why you heat your steel when you want to shape it by forging.

Iron, Steel and Swords script - Page 145

6.1.3 Reading Phase Diagrams: Mixed Phases and Boundaries
The next rule we need to learn is about two-phase regions. What happens there?
At a first glance something quite strange. While we still can define a proper location in the phase diagram, and draw
it as a point or small circle called a "state point", it doesn't make much sense anymore.
Our system, after all, contains two different phases and that's why it decomposes into two state points, always
positioned on the boundaries separating the two–phase region from the one-phase regions to its left and right.
To understand this, we look at an example. We take two steels: a low carbon one (around 0,35 %) and a"eutectoid" one (around 0,8 %) or " composition 1" and "composition 2", respectively.
This is drawn into the phase diagram below, where I also have added some additional information.
Now fire up your brain smithy and heat both steels to a temperature of about 1200 K (927 oC, 1701 oF), where you letthem sit for a while. This state of being is symbolized by the green and red state points in the phase diagram.
At the high temperature where we start our two steels, we have plenty of vacancies running around. The carbon
interstitials run around extremely fast too, and our two steel crystals achieve nirvana with respect to their carbon
distribution rather quickly.
The carbon atoms then are uniformly dissolved into the fcc crystal structure that the iron always assumes at thattemperatures, no matter what kind of structure it might have had before we heated our steel. The crystal goes fornirvana and even tries to get rid of all the grain boundaries and dislocations that might be in there.
The crystal will work hard at doing this but it will not be totally successful in your or my lifetime. Nevertheless,unwanted defects will be removed to some extent during the time you wait, and we will have relatively large
austenite grains with few dislocations.

Cooling two different compositions from about1200 K.

Now an evil person—you, the smith—takes the steel pieces out of the fire where they were happily approaching nirvana.
Their temperature starts to go down, and that means that our red and green state dots move down the vertical linewith some "speed" that is given by the cooling conditions. As long as they stay in the yellow area that marks theaustenite phase, they don't care all that much about getting colder. As long as their state dots are in austenite
phase region, they are close to nirvana.
Sooner or later the red composition 1 steel will come to a critical temperature (second red state point) that
separates the pure γ phase from the mixed α + γ phase region; soon after that it comes to a second criticaltemperature (black point) separating the α + γ phase region from the α + Fe3C phase region.
The composition 2 steel too will have come to that critical temperature by then. As soon as steel No 1 gets inside
the blue-yellow triangle that marks the region where we have a mixture of the α phase and the γ phase, it needs toassume that "state", whatever it is. Nirvana now means you must be α + γ, so that's what the steel is endeavoring
to be.
There is no choice now but to decompose into some parts that are still γ = fcc, and some parts that must change
into α = bcc.
But how can that be? There is no α phase with a carbon concentration like that of our two steels. It there must be an αphase, it must have far less carbon inside than what composition 1 brings along.
Well, crystals go through whatever it takes to obey the second law. The carbon is expelled from the parts thatassume the α phase, and the remaining γ phase must take the surplus. That is not as tricky as it sounds.
Illustrated it looks as shown below
Iron, Steel and Swords script - Page 146

Growth of ferrite in the two-phase region ferrite austenite
The lines in the structure pictures are grainboundaries. Blue areas are ferrite

As soon as a phase transition to the mixed α + γ phase becomes necessary (we still call it a phase transition even so,technically it is a transition from one to two phases), small specks or nuclei of ferrite start forming at some good
nucleation points. That means grain boundaries, of course, or even better, the nodes of grain boundaries as shown.
The carbon is redistributed. Very little remains in the ferrite, most is now in the austenite.
How much precisely? Exactly as much as the two new blue and yellow state points on the boundaries between themixed α + γ phase and the neighboring phases to the left and right will have.
The phase diagram even tells us how much of α + γ we will need. That relates to the length of the red horizontal
lines in the figure above to the left and right of the black state point; I'll come to that shortly
So the rule for two-phase regions obviously must be:

In two-phase regions the state dot will
always decompose into two state dots.
These are situated at the intersection of
the horizontal " tie-line " with theboundaries separating the two-phaseregions from the one-phase regions

The tie-line is simply the horizontal line defining a constant temperature.
The mind now boggles a bit and thus is very receptive to new little theorems:

1.

For a binary system there are never more than two phases in amixed phase region

2.

To the left and right of a two-phase region there are always onephase regions

Now that's a relief! Complicated structures like mixtures of ferrite, austenite and cementite are now forbidden!

Iron, Steel and Swords script - Page 147

Those are not obvious little theorems, by the way; they are actually rather hard toprove. They come out of a more general theorem called Gibbs' phase rule.
I will not go into the intricacies of Gibb's phase rule here; consult the science
module if you are interested.
I will point pout, however, that the geographic maps you know also go with a major
theorem that you probably don't know. It also says something about how manydifferent areas you can find.
Here is the key word: "Four color theorem".
Use the link if you want to know.

Science
Link
Gibb's phase
rule

Back to two–phase regions, knowing now that there are no three-phase regions. What you, dear reader, must have been
wondering about if you looked at the picture (otherwise do it now), is that during its travel through the two-phase region
the actual composition of the steel must change all the time!!!.
The ferrite regions must get larger, the austenite region must shrink, and both of them must change their carbon
concentration all the time while the temperature goes down. That's what the phase diagram states. And that's whatmust happen for nirvana!
Evidently that implies that a lot of atoms need to move.
That's exactly what it means. If the temperature is high enough long enough, so all those atoms can move, eitherwith the help of vacancies or by direct diffusion in the interstitial lattice, your steel can cope. It might feel a bit
harassed by being put through this ordeal but it only needs sufficient time to move a lot of atoms about. Doing that it
establishes closeness to nirvana once more.
Now comes your great moment to show that dump piece of inanimate matter who is the Boss!
You, the ancient (or modern) smith quench your steel, meaning you cool it very rapidly, typically by throwing the
red-hot piece into cold water.
Your steel hates you now but can't do much about it. Nothing in there can move anymore after the short time ittakes to get down to just a few hundred centigrade.
That is true at least for the outer parts because the inside of a big piece of iron always will stay hot far longer thanthe outside, of course. There is only that much you can do with quenching.
The structure you find now at room temperature might be quite different from what your steel had in mind for its nirvana
state, or at least for some second-best state.
Your work piece may even shatter into fragments because large stresses built up that exceed the fracture stress atsome point. If it doesn't fracture, it might bend into weird shapes because dislocations react to the stress, move around,and cause plastic deformation.
Why should stress build up? Because the cold parts on the outside contract (the opposite of thermal expansion)and "squeeze" the hot parts inside so much that a lot may happen. "Squeezing" is, of course, just another word forexerting stress on the inside.
We definitely must expect plastic deformation to take place during quenching, and possible even fracture

Here is a first reason for the "soft"
steel core inside sword blades.
It can easily "give" and thus keeps
the blade from fracturing during a quench.

You noticed, I hope, that I have started discussing what you, the smith, can do, in contrast to what the steel wants to
do. I'm starting right now to move from the science of "happy" metals close to nirvana, to the technology or engineeringof metals. That typically means that we need to make them unhappy but useful. Sometimes I wonder if women feel thesame way about men.
Before we go deeper into this, I will explore what happens to steel No. 2 with the eutectoid composition of 0,8 %carbon.
You know the rules by now. You do it. I help you by providing a suitable picture in the next figure.

Iron, Steel and Swords script - Page 148

What happens at this eutectoid composition?

"Well, upon reaching about 1000 K, the steel enters the two-phase α + Fe3 C region and must decompose into thephase to the left (α or ferrite) and the phase to the right (Fe 3C). Right?" Right! Good answer.
"And what exactly is Fe3C in this context?" Good question!
In our phase diagram it is shown as a solid vertical red line at 6,7 wt% carbon. What's so special about the"magical" 6,7 % carbon?
Look at the scale above! It happens to be exactly 25 atom %, and that's what counts.
In other words, we have a composition with exactly one carbon atom for three iron atoms. If you have that, you canactually form iron carbide , a chemical compound with the chemical shorthand Fe3C and the name "cementite".
The properties of cementite, or iron carbide, or Fe3C, or whatever you want to call it, relate to the properties of pureiron (Fe) or pure carbon (C) just as much as, for example, table salt (NaCl) relates to pure sodium (Na) or purechlorine (Cl): Not at all!
Cementite by itself is some hard and brittle stuff. Its name was introduced by Osmond and Werth in 1885, when theyrealized that at high temperatures steel contained what we now call ferrite and austenite, and that at low temperatures
there were "cells", somehow cemented together by some carbide that they aptly called cementite.
You're getting a bit woozy now; I'm getting tired, too. But before we take a break with our favorite liquid poison, youmust realize two important things:
1. You don't yet know all there is to know with respect to the iron-carbon phase
diagram; e.g. that all of the above contains a big lie. Continue with thescience link if I haven't reached your yield point yet.
2. You did realize a major truth about plain carbon steel: It's iron with just alittle bit of carbon in it (something like 0,3 % - 1,5 %), Yes, but did you
realize that carbon steel cannot be a uniform smooth substance at room
temperature?
The phase diagram insists that it is a mixture of relatively pure and soft iron (theferrite) and something rather alien: hard and brittle cementite, a crystal with a rather
complex crystal lattice. We are forced to conclude:

Science link
Phase
diagramSteel is a composite material on a
microscopic scale. It is a mixture of hard(cementite) and soft (ferrite) components.

Steel in its most simple form as plain carbon steel already consists of hard cementite and soft ferrite pieces if you
look at it with a microscopic. It's already a kind of "damascene " material even if it appears to be perfectly smooth
and uniform to the unaided eye.

Iron, Steel and Swords script - Page 149

6.2 Things Get Complicated

6.2.1 Creamy or Chunky?
Many materials consist of hard and soft phases, for example chunky chocolate ice-cream, peanut butter, nacre ("motherof pearl") or steel. Hard particles —chocolate chips, peanuts, calcium phosphate or cementite—are embedded in thesoft smooth background of ice cream, butter, proteins or ferrite, respectively.
So let me ask you: As far as steel for your sword blade is concerned: do you want it creamy or chunky? Do you
want a lot of very small particles or rather a few large ones in your ice-cream, excuse me, ferrite?
Since you only have a certain amount of the hard stuff, you can turn it into a lot of little particles, into just a few big
ones, a mixture of big and small ones, or anything in between.

What's the best?

This is an extremely far-going question, that's why it's emphasized.
The answer is clear, of course: It's a matter of taste as far as chocolate ice cream or peanut butter is concerned. As
far as nacre or steel is concerned, it's also a matter of taste with regard to the properties you want.
As far as steel is concerned, the general agreement is that you want it hard but ductile .
Hardness , as we have learned before, is simply a measure of the yield stress, the force per area at which
dislocations begin to move. Hard but still ductile steel means that it's difficult but not impossible for the dislocations
to move. If dislocation movement is impossible (like in cementite) you have a brittle material, and that's not what wewant.
The long and short of this is that we must allow the dislocations to move around a bit. Movement shouldn't be easy,
however, and we want to be in full control.
It's a bit like keeping teenagers under control. If you ground them completely, things break. You must let them roamaround a bit but it is wise to slow them down, e.g. by keeping in control of car keys and money.
For slowing down dislocations in steel, we use our hard cementite particles.
Let's generalize this insight into the next epiphany:

Hardening steel (or any other metal forthat matter) means to put obstacles in
the way of its dislocations.

Let's review the tools we have for this. There are essentially five major types of obstacles that make dislocation
movement difficult but not impossible:
1.
2.
3.
4.
5.

Extrinsic point defects or foreign atoms dissolved in the matrix.
Precipitates, made from the foreign atoms we have inside the steel.
Grain boundaries.
Other dislocations.
A metastable fourth phase of iron called "martensite".

Martensite (whatever that is), our fifth tool, is rather unusual and specific to steel (and some other crystals). It isespecially tricky but provides for the ultimate in steel hardness (and increased brittleness).
I you want to use martensite hardening you really must torture the crystal. You must force it to make something
it really, really hates: martensite!
Now what is a metastable phase? It cannot be part of a real nirvana state because the system, by definition, could do
better.
A metastable phase is a phase that is not really stable at the given temperature but bound to decay into the reallystable phase, meaning a phase that is part of a nirvana state.
A metastable phase is often just a transient structure encountered on the way from one clean and desired phase toanother one. In other words, it's something like a teenager—no longer a child but not yet an adult.
Iron, Steel and Swords script - Page 150

A diamond, by the way, is a metastable phase of carbon. So you teenagers out there can stay cool and refrainfrom sending me hate mail. Metastable states can be quite valuable and they can last a long time. In this case wetreat them like a stable phase and use them even in phase diagrams.
Nevertheless, they are not the nirvana states or the best of all possible states. You might perceive them in terms ofan extremely simple diagram:

Stable and Metastable States

The diagram shows the free energy; the lower the better. The black curve shows what is possible. Moving to theright towards nirvana, you might get stuck in a side valley that does not have the lowest possible free energy. If it isdifficult to get out of there, you are stuck in a metastable state.
Words like "position" and "way" do not exclusively refer to common space but might be metaphors for more
abstract entities.
A system of atoms as seen by the second law can behave just like a "mass point", a ball, or you in a mountain
range. You want to be as far down as possible. Gravity pulls us down, and the nirvana state we try to achieve is way
down.
However, you might get stuck in a side valley that does not have the lowest possible free energy. If it is difficult to
get out of there, you are stuck in a metastable state. You only get out of it and over to the deepest point by firstworsening your situation again. You must first go up to be able to get down to nirvvana.
If you don't have the energy any more to do this you are now trapped in the metastable state until you can get it up
again. That might take quite a while, depending on circumstances.
If we now look at a diamond crystal instead of you, it is pretty much the same thing. The fcc diamond lattice is notwhat the carbon atoms would like to have. They would much prefer the hexagonal graphite structure. But to get"there", a lot of reshuffling of atomic arrangements is required and at room temperature the energy for doing that isjust not available. Diamond is thus a metastable structure of carbon. And, as women know, diamonds are girl's bestfriends. And that's because they last forever. Well, if kept around room temperature, they last at least as long as thegirl and that is good enough. Heat it up sufficiently (= supplying energy) and they will turn into graphite.
Cementite in iron, by the way, is also only metastable. The stable state of carbon in iron would be graphite.
Cementite is, however, stable enough not to do anything in your and my and our offsprings lifetime, so we do notneed to worry about this.
I will come to martensite in more detail shortly when I discuss hardening mechanisms in detail. Since hardening steel isa major part of the smith's art, I will dedicate a whole chapter to the basics of hardening mechanisms in steel or justabout any crystal
But before I do that, I'll answer that pressing question that must have been on the back of your mind all this time:

What happens when we go from theliquid phase to a two-phase region?

Iron, Steel and Swords script - Page 151

6.2.2 Solidification and the Art of Casting

What happens when we go from theliquid phase to a two phase region?

That was that pressing question on the back of your mind! Or was it? Why should this be a pressing question? You
know what happens when we go from the liquid phase to whatever solid phase: the stuff solidifies!
Indeed—but how? If you look at our iron-carbon phase diagram again and stay rightwith the 1,3 % carbon composition line we used before, you realize that uponcooling from the liquid ("L") state you run through several phasefields before you
are at room temperature:
1. γ + L
2. γ
3. γ + Fe3C
4. α + Fe3C.
The stuff solidifies, alright. But how is that going to happen?
To put the question in other words: You and about everybody else too, has a far too
naive view of what is implied in casting something. Ask around and you will findout that
the askee has never ever given the topic a single thought.
If pressed, most people would guess that whatever the melt consists of just"freezes".
Let's say the melt consists of iron and 1.3 % carbon. Almost everybody out there
would expect that upon "freezing" you get solid iron with 1.3 % carbon "somehow"
dissolved in it. Almost nobody would guess that at room temperature you haverather pure iron with some embedded iron carbide but that at higher temperatures
the solid would be completely different from that.
Nobody (well, almost nobody) would guess that the science of casting is a rather complex field.
I grant that you, the ancient smith, did not cast sword blades or anything else made from pure iron or steel. So why
should you worry? Because in order to understand wootz steel, we need to look at what really happens when wego from the liquid phase to a two phase region! We will find that the basic difference between wootz steel blades
and all others stems from the fact that wootz steel was liquid once.
Of course, all we need to do is to learn a few more things about phase diagrams. Then we give the iron-carbon phase
diagram a close look and figure out what happens when we go from the liquid phase to the solid phases. It should
contain that information, after all. It does, indeed, but the iron-carbon phase diagram is also a rather complex one. Youmight wonder if most of the other ≈8.000 binary phase diagrams are much simpler? Maybe only iron and carbon produce
such a complicated mess?
The squiggly lines "≈", by the way, mean simply "about". I'm going to use common science abbreviations more often
from now on because at this point the faint of heart or soft of brain are no longer with me.
So does the iron-carbon phase diagram belong to the more complex ones?
Unfortunately or luckily, depending on your point of view, this is not the case. There are plenty of phase diagramsout there that are far more complicated than the iron-carbon one; take, for example the phase diagrams for copper(Cu) and tin (Sn), producing what we call bronze, or copper (Cu) and zinc (Zn), producing what we call brass. They
are shown in an illustration module. Both phase diagrams plus plenty of others are easily found in the Internet.
If you start to feel sorry for our students, consider that this will give them jobs. Having a lot of complicated phase
diagrams is actually good luck because it will give us opportunities for engineering novel and useful materials for along time to come.
Simple phase diagrams are not only intellectually boring, there is just not much you can do with those materials.
Fortunately for you, there are simpler phase diagrams, too, and they make it easier to get the point across that I want tomake now.
Examples for most simple phase diagrams include the gold - silver, or copper - nickel systems. Here we give a quick
look at a slightly more complicated phase diagram: a mixture of lead (Pb) and tin (Sn), including common solder.

Iron, Steel and Swords script - Page 152

The lead-tin (Pb-Sn) phase diagram
Solder is the Pb-Sn composition at the eutectic point(≈ 73% Sn)
Let's start with a composition around 73 % tin (Sn) (the green state point in the figure above). Cool this mixture down
and it will solidify directly from the melt at the "eutectic point" into a two-phase solid. It will not go through a phase field
where it decomposes into a mixture of liquid and solid with different compositions as we had before. The solid thus has
exactly the same composition as that of the melt. It decomposes into two different phases (α and β in the example
above) but the composition is the same as the melt.
That's what the phase diagram tells you. As you can also see, the eutectic composition that we have at an eutectic
point is by necessity the composition with the lowest possible melting point of a binary system.
Now you realize why "eutectic " is such a magic word in working metals! If there is an eutectic composition in yourphase diagram, it makes for easy casting:
The melting point is as low as it will ever get.
The composition of your melt will be the composition of your solid - everywhere!
"Eutectic", by the way, is from ancient Greek and means: "easily melted". Aha!
To be sure, the solid just below the eutectic point does decompose into tin-rich lead and almost pure tin as shownin the phase diagram. But the over-all composition is unchanged.
What a typical eutectic microstructure looks like is shown in the following picture:

Eutectic microstructures
Solder (Sn-Pb)
Al-Cu (33 wt%)
Steel.
Lamellae of tineutectic alloy.
Eutect oid(with a bit ofLamellae ofcomposition (I'll get
dissolved lead)
aluminum (with a to that).
and lead (with a bit bit of dissolved
Lamellae ofof dissolved tin)Cu) and copper
cementite and ferrite
form a "zebra(with a bit of(with a tiny bit ofstripe" patterndissolved Al) form dissolved carbon)
a "zebra-stripe"
form a "zebra-stripe"
patternpattern

Two things are obvious:
1. There seems to be a very special "zebra stripe" structure for eutectic compositions.
2. This "zebra stripe" structure seems to occur for all (?) eutectic systems as demonstrated by the three
examples, one of which is eutectoid (?) steel.
I'll get to the question marks in due time. Nevertheless, if you want to understand steel, you must acquire a bit offamiliarity with eutectics and close relatives.
What you realize by now is that solidification in general and casting in particular is notas simple as it looks, indeed.

Iron, Steel and Swords script - Page 153

What you realize by now is that solidification in general and casting in particular is notas simple as it looks, indeed.
Let's look now at non-eutectic compositions, for example the red composition atabout 33 % tin as shown above and on the right. The melt, according to the phase
diagram, decomposes into some lead-rich solid stuff and a tin-rich liquid as shown
exemplary by the two red state points in the L + α phase field.
By the time when the last droplet of the remaining tin-rich liquid has solidified, thesolid has a very inhomogeneous over-all composition as shown below.
This is nothing new. When you freeze the binary system H2O - NaCl (also known
as salty water), the first solid that crystallizes from the "melt" is sweet ice that
contains very little salt. The more ice you form, the saltier the water must get. The
last bit of water to solidify then must contain all the salt and that ice then is salty.
Your ice, in other words, is not uniform with respect to its saltiness.
If you don't believe me, look up this illustration module.
But back to the Pb - Sn system. The chunks crystallizing first are lead-richcompared to the over-all composition; the remaining liquid then is enriched in tin.
Now comes the crucial questions

How should one imagine a mixtureof lead-rich solid and tin-rich melt?
Are solid pieces floating aroundin the liquid?

No, no, no!!! Not at all! Consider:First, the solid in this case would be "heavier" than the liquid and sink "like lead" to the bottom.
Second , and more important: solidification or crystallization will always start at the coldest places, and thecoldest places for starters are always the walls of the container or the surface.
Third: This is obviously true for all mixed solid - liquid phases with the exception that on occasion the solid
pieces could also swim on top. Only if the density of solid and liquid is identical (very rare) would the solid
float in any depth.
As the temperature goes down, more and more liquid crystallizes and the newly crystallized parts get increasingly
tin-rich. The final result is a lump of lead-tin alloy that is lead-rich on the outside and tin-rich in the inside relative to
its gross composition. Schematically, it looks like this:Solidification of an alloy and the phenomena ofsegregation
There will be a lot of grain boundaries (indicated in theleft picture)and dislocations as we have seen before.

We have now encountered the phenomenon of segregation, meaning that the composition of the solid material is not
the same everywhere (as you probably would have liked it to be). It varies considerably on a "macroscopic" scale, likefrom the outside to the inside of the crucible or die that is used for solidification. If we just describe what we get, we saythat the components of our mixture got segregated or separated. And what that means is:Iron, Steel and Swords script - Page 154

We have no longer the same composition
everywhere. That means that we have nolonger the same properties everywhere.
This is generally not so good!

Even worse, besides this more "macroscopic" segregation that leads to variations in the composition of the solid ona large scale, there is also something called "micro segregation" on a small scale. This is shown below for our
example from above

Macro segregation and micro segregation

On the left the variation of the lead and tin concentration due to macro segregation , coming right from the phase
diagram, is shown schematically. On the right we look at just the lead concentration in a small region (millimeter orsmaller) The concentration fluctuates more or less periodically, due to micro segregation effects, around theaverage values (dotted line) given by macro segregation.
Micro segregation results from reasons not contained in the "nirvana" phase diagram. We will give it a closer lookbecause it is directly responsible for the "water " structure of wootz steel blades.
So you better get used to the term segregation. It is is a key phenomenon for
sword making (and for most everything else).
In human affairs segregation is usually considered to be bad. In Materials Scienceaffairs, segregation is neutral.
From the viewpoint of the material, macro segregation is good because it brings thesystem closer to nirvana. And everybody is entitled to pursue happiness, after all.
From the viewpoint of the Materials Engineer, segregation is often bad. However,you couldn't make wootz blades without it, so for this purpose it is good. It is also
great if you want to clean your material. If you want sweet ice from watercontaminated with salt, let if freeze and take only the parts that froze first. They areclean. The same principle applies of you want extremely clean silicon, and so on.

Science
Super
Link
Segregation

Nothing helps, you need to understand at least the basics of macro- and micro segregation because we need tomanipulate that behavior quite a bit to make sword blades. If we deal with segregation the right way it will not bother us
too much anymore, and we might even use it to our advantage like in wootz steel. I will give you some hints here, use
the science module if you want to learn (a lot) more.
We already know that macro segregation is a direct consequence of a phase diagram, which in turn is a directconsequence of the second law.
So let's now give a first quick look at some of those many new things that might cause micro segregation.

Iron, Steel and Swords script - Page 155

Nucleation of grains and dendritic growthUpper figure::
Schematics of nucleationand first grain formation.
Lower figure: Better
schematics of first
dendritic grain formation;a kind of "enlargement" ofthe yellow grain above.

Scanning electron microscope(SEM) picture of dendrites in anickel-based super alloy. You
get a picture like that by starting
solidification and then quickly
spilling the melt during theprocess
Source: S.A. David et al.

When I introduced you to grain boundaries, we looked at solidification at some solid - liquid boundaries advancing into
the material from various nucleation points typically found at the surface of the container. Look at the relevant figure
once more to recall what I mean. Now notice that the way it is drawn is far too simple with respect to reality.
In the figure above parts of the old figure are shown once more. If we would look a bit closer at one of the growing
crystals like the yellow one, it would often look like the "dendrite" shown above.
Dendritic or "tree-like" growth is fairly common whenever the "driving forces" are large (I'll come to that). For thetime being, just note that you have large "driving forces" when you cool down quickly.
What happens then is fairly complex, if well understood. I'll give you details later. In essence the solidifying part
releases "heat of solidification " and thus heats up itself plus the liquid around it. That makes solidification moredifficult and slows down the advancement of the dendrite tip into the liquid.
Heat of solidification is simply the energy no longer needed if the atoms don't run around in the liquid anymore.
As soon as we have a solid, the atoms are tied down to a place in the crystal lattice where they can only vibrate somuch. We covered that already.
You know that effect quite well, you just didn't give it fancy names. Put some very cold water close to the freezing
point into your freezer. It won't freeze instantly because the energy released as "heat of solidification" heats it up
again. Your freezer must transport this energy to the outside world, and that takes a while.
Same thing in reverse. Put your frozen soup into a pot and put it on your range going at full blast. It will not liquefy
instantly; it actually takes quite some time. Now you have to supply the heat of solidification or the heat of melting,same thing, and that takes a while.
We already have a first reason why solidification could be a stop-and-go process even for pure materials. Let's say
the solid-liquid phase boundary advances rapidly into the liquid part at some time. Then a lot of heat of solidification
is produced, the temperature goes up and things slow down. Now less heat of solidification is produced, thetemperature goes down, and things speed up once more. And so on.
If the melt contains any impurities, things get more complicated. Impurities usually like it better in the liquid (look at thephase diagrams!) so the solid will have a lower concentration at first. A heat of steel always contains all kind of
impurities, so solidifying steel is always rather complicated from a segregation point of view.
The liquid close to the solid-liquid phase boundary thus will get impurity-richer because it "get's" all impurities not
accepted by the solid. The impurity concentration close to the the solid-liquid boundary is thus larger than it ought
to be. That always means that the local melting point is now lower than it ought to be. This makes solidification
more difficult, it slows down or comes to a stop.
Meanwhile, the surplus impurities in the melt diffuse into the bulk of the melt and their concentration close to thesolid-liquid phase boundary goes down. That means the local melting point goes up, and solidification speeds up.
Once more, good reasons for a stop-and-go process of solidification or, to put it more precisely, a fluctuating growth
speed of the solid.
To summarize and generalize: There are reasons why the solid-liquid boundary should not advance with constant speed
into the liquid. In other words, there are reasons why the growth speed of the interface should fluctuate or oscillate.
There are also reasons why this should not happen in lock step everywhere but in different ways at different places.
Be that as it may, the decisive parameter in the end is the (local) growth speed, meaning how fast the solid-liquidinterface advances into the liquid. The reason for that is simple: How much impurities are incorporated into the solid
depends on that growth speed.
You should protest here and tell me that how much of an impurity end up in a solid depends on the phase diagram andnothing else! It should thus not depend on the growth speed of the interface!
Iron, Steel and Swords script - Page 156

You are right! And I'm right, too. We both can be right about a mutually exclusive item because, as I stated long
before, "Phase diagrams show only the "nirvana" state". A freshly solidified piece of material may not be in thatdesirable state, however!
Looking at this a bit more closely (with equations), it turns out that the phases predicted in the phase diagram will
only come into their ideal being if the solid-liquid boundary advances v e r y s l o w l y. If it advances with normal
speed, the expelled impurity atoms close the solid-liquid boundary do not have enough time to move away from theboundary into the depth of the liquid. What then solidifies next is a liquid different from that in the phase diagram.
You will now incorporate more impurities in the growing crystal.
That's sounds more complicated than it really is. All it means is that the fraction of impurities ending up in the
crystal relative to those in the melt goes up with increasing growth rate. Keeping this in mind, let's see what
happens now if we solidify a melt containing two kinds of atoms.
Let's assume that we have some fast crystallization at the solid-liquid interface of some growing grain. We have alreadyseen that several things conspire to cause the growth rate to fluctuate or oscillate, meaning that crystallization happens
in a stop-and-go fashion. Let's look at this again but now also keeping in mind the impurity incorporation into the crystal:
1. During fast crystallization many of the impurities contained in the melt will end up in the crystallized part
because there is just not enough time to keep them all in the melt or to expel them from the solidified
crystal. Those parts of the crystal that solidified fast therefore will have a relatively high impurity
concentration; above of what the phase diagram predicts.
However, while crystallizing fast, a lot of heat of crystallization is released that heats up the melt next to thesolid-liquid boundary to a temperature possibly above the melting point. Crystallization has no choice but tostop or at least to slow down.
2. During slow crystallization most of the impurities remain in the melt, enriching it locally beyond theconcentration of the basic composition. That means that locally the melting point now comes down, slowing
down crystallization even more.
3. Now the impurity atoms in the impurity-rich part of the melt have enough time to move away into the depth ofthe melt; their local concentration goes down. That means your local melting point goes up while the generaltemperature still goes down because you keep cooling your system. Crystallization speeds up and becomes
fast again.
4. Back to 1.
OK - I admit that the phenomenon of constitutional supercooling is a bit hard to understand when first encountered. It
is even hard to calculate if we look at it in three dimensions and not just one-dimensionally as implicitly done in theprose above.
In the final result, however, it is quite likely that the sold-liquid interface moves in a stop-and-go fashion in not just one
but in all three dimensions. This produces not only the characteristic dendritic shapes but also a more or less periodic
variation of the impurity concentration in the solid.
Here is the reason for all kinds of what we call "pattern formation" in solidmaterials, and that includes the patterns found in wootz steel. We like that patternand see it as aesthetically pleasing and a sign of quality.
It also includes pattern we find in the ultra-pure silicon (Si) crystals we use formaking chips. We hate those patterns but must live with them. More about that in
the science link.
Segregation is rather the rule and not the exception when you solidify liquids. We
will look at this some more in later chapters.

Science Link
Segregationin SiliconPattern formation by segregation effects comes with many names. They may be called "banding", or "striation"
and always involve a non-uniform distribution of impurities. Of course, the effects of segregation have been observed
and described centuries before they were understood.
Sorry. I now destroyed your naive view that solidification and casting is a simple process. Just pure some liquid into themold, wait a while, and take out the solid product? Ha!

1)

S.A. David, S.S. Babu, and J.M. Vitek; "Welding: Solidification and Microstructure", JOM (2003) p. 14. By kindpermission of S.A. David

Iron, Steel and Swords script - Page 157

6.2.3 Welding with Hammer and FireAll the old sword blades we marvel at in museums or books have not been cast. Some welding may have been
involved, though. We thus must consider welding to some extent. We will do that right here and then come back to it in
the context of making swords.
Welding for most people means to join two metals of the same kind by filling the gap between the metal pieces withliquid metal of the same kind. You do it be pressing the two pieces together and heat the seam until things melt. In
addition, you may feed some material to the seam.
Whatever you do, parts of the metals to be joined will be liquefied too to some extent. Let's call that kind of welding
liquid welding.
By the way, if we join two metals by filling the gap between the two with a liquid metal of a different kind that has a far
lower melting point, we call that process soldering . And by the way once more, if we use something other than ametal at low temperatures as intermediate for joining two work pieces we call it gluing. We also have "sintering" (=heating a compacted powder for some time) as a joining technique for metals ("powder metallurgy") but thattechnology is more prominent with ceramics.
In all these cases the metals to be joined are not liquefied.
We also may join metals by riveting or by screwing them together. If you ponder this a minute, you realize thatjoining metals (and other materials) is at the very heart of making machines or just about everything more complex
than a flint stone tool.
Back to liquid welding. So first it's liquid, now it's solid - there is no principal difference in what we now call liquid welding
to casting, the amazingly complex process we just covered.
This means that all the problems discussed above in the context of casting and general solidification apply just as
well to liquid welding.
In particular, the structure and thus the properties of the solidified parts of the weld seam might be completely
different from the structure in the unaffected metal. Moreover, the structure in the heat affected zone next to what
was liquefied might be different too. After all, that part, though not molten, was heated up to very high temperaturesand cooled down again rather quickly.
Almost anything can happen. If your weld seam is far softer, far harder, or even brittle compared to your metal, you
got a problem.
It is a big problem. So big that we must accept that a lot of metals cannot be welded at all - and that includes somesteels!
Next time you go places with an airplane, look at it closely. What you will see is that it's metal parts are riveted
together, not welded. Airplane bodies consist mostly of an aluminum alloy and those are very difficult if not
impossible to weld.
Is the body of your car welded, soldered, glued, riveted or screwed together? Do you know? Yes? Good! Now go andask your wife; she probably neither knows nor cares. You know, of course that your car parts are welded together or possibly glued? This apparently asinine question is not quite as stupid as is sounds; ask your BMW dealer, forexample.
Pretty much all cars (except for some high-end Audis) are made from weldable steel. If you can't weld the body
together, you have a big cost problem. Same thing for ships and plenty of other steel constructions. One of the
problems encountered when big things like ships were welded together for the first time, supplanting timeconsuming and expensive riveting, can be found in this link.
By the way, next time you encounter an old iron construction like a bridge or a train
station, look at it closely, too. The whole thing is riveted together for sure. People
couldn't weld steel before 1920 or so, and all the huge steel construction coming
into being in the late 19th century were riveted together because solidification ofsteel hasn't been mastered.
Even with modern technology, the weld seam is the weak point in a steel
construction as some pictures in the link, including a horrible one, amply
demonstrates.
The picture below, showing a cut through a weld seam, makes clear why. The
visible structure is mostly from the cut; the microstructure would not be visible athis low magnification (maybe 10 fold). Nevertheless, it is clear that there are major
disturbances of the microstructure. If you optimized the microstructure of yourmaterial, it can only be worse at the weld.

Iron, Steel and Swords script - Page 158

Illustration
Link
Riveting,
Soldering,
WeldingGood weld seam
Source: Internet; sorry can't find it again

However, liquid welding is not so interesting in the context of sword blades. You, the ancient smith, couldn't melt youriron and steel anyway, remember? So you could neither cast it nor liquid-weld it.
We will not pursue it any more except for pointing out the epiphany we just had

You cannot simply weld the piecesof your broken blade together
by using liquid steel.

So liquid welding is out. But weld we must if we are to make a "pattern welded" damascene blade or just about any ironor steel object for the first 3.000 years of iron and steel technology.
How about just banging two pieces of the same material together? For chewing gum or wax this kind of works. It doesn't
work for iron or other metals, however. Try it. Take two nails, two sheets of aluminium foil, whatever, put the pieces on
top of each other and bang away with your hammer.
However hard or cunningly you hit the pieces, they will not weld together. But you, the smith, knew that anyway. You
also know how to do it right: You must heat your two iron or steel pieces to a rather high temperature before you start
your banging. Then the two pieces might stick together. If you sprinkle some "magic" stuff on the hot surfaces to bewelded together, it works even better.
This is a kind of "fire" welding that pretty much all smiths did it and still do to this very day.
You take two pieces of iron or steel, make them hot, sprinkle some "sand" on them, and bang them together withyour hammer. If properly done, the effect is the same as liquid welding: two pieces have been joined to form just one
piece without any intermediate layer of solder or glue.

Just to know what we are talking about,
let's call this procedure: hammer welding
or fire welding
It is also called pressure welding,forge welding, or contact welding.

Iron, Steel and Swords script - Page 159

So how does hammer welding at high temperature work? Before we look at that, let's consider the reverse question:
Why will two pieces of iron brought into close contact at room temperature not stick together and get "contact-welded"
just so? Or at least after some severe banging?
After all, a metal atom at the surface has some free space around it that it would love to fill with other metal atoms. We
know that it always wants to have a lot of neighbors around: 12 for the fcc and hex crystal structure and still 8 for thebcc structure (back to chapter 4.2.2 if this doesn't strike a chord).
The answer, of course, is simple. Metals (and most anything else) do not contact
weld if brought into close contact for three reasons:
1. There is usually no such thing as metal-metal contact. With the exceptionof noble metals, there would always be a metal oxide (green) - metal oxide
contact, with plenty of dust and dirt particles (red) in between. And atoms
in metal oxides, in contrast to metals, do not necessarily want to have as
many neighbors as possible.
2. Even if your surface would be clean, pretty much all surfaces are rough on
an atomic scale (even if they appear to be highly polished). Contact only
happens at a few irregular spots. Even if some bonding occurs at thesespots, the total effect would be very weak.
3. Even if some clean and perfectly flat metal pieces would be put together,joining the grains on both sides needs to produce a grain boundary
because it would be unlikely that the grains touching have the sameorientation. That means that at least some surface-near atoms must movearound a bit. This takes some energy, which might not be available at low
temperature.
Easy to understand. However, we also might argue in reverse: two materials withatomically flat surfaces and no dust in between should stick together at medium
temperature if brought into contact. Does this happen?
You bet. It's called "wafer bonding" and done routinely nowadays in clean
rooms (no dust) with rather perfect and ultra-flat silicon (Si) wafers. Contact
welding cannot possibly be easier or better with other materials. If you bondwafers at room temperature, the wafers will stick together but are not strongly
bonded yet.
Some heating is still required to provided the energy for the necessary grain boundary formation. What you get forsilicon (Si) is shown below:

Grain Boundary after contact welding rather perfectsilicon.
Left: Looking at the "seam" edge-on with atomic
resolution. The two crystals have joined rather perfectly inparts.
Right: Looking at the contact welding seam from above(top view). A complex network of dislocation is present,
constituting the unavoidable grain boundary. Some oxide
inclusions are seen too. More in this link.

I tried to align the two wafers with respect to their crystal orientation, but you can never do it so they have exactly thesame orientation. A ("small angle") grain boundary still is needed, and it is a complex creature as you can see in the
picture above.
What, exactly, do we see in the picture?
Iron, Steel and Swords script - Page 160

The left-hand atomic resolution picture shows a perfect weld seam with some little mismatch of the crystal lattices.
It does not show much else for the reasons given before.
In the right-hand picture we have the top-view and look at the weld-seam area from above. The complex looking
network is nothing but the required dislocation structure needed for the kind of grain boundary we have here. Moreinteresting are the shapeless gray blobs, circled in red. They are small silicon oxide (SiO2) particles that got
embedded in the weld seam despite all my efforts to keep the welding nice and clean. They correspond to the slag
inclusions incurred when hammer-welding steel.
Without some heat and pressure one only gets weak welding for the reason given in item 3 above. Nevertheless, thebest we can do in contact welding nowadays is to use ultra-clean, ultra-flat, single-crystalline silicon wafers with thesame orientation as far as possible. I show you the results here just to demonstrate that even for the best possible
conditions, you get a rather huge mess. If you bang the whole package with your hammer, the mess will not get
smaller.
Now let's consider contact welding for steel. We certainly don't have atomically flat surfaces, the steel at all times iscovered with a thin (some nanometers) oxide, and the crystal orientations don't match because it is a poly crystal
anyway.
If you now heat up your steel to red-hot temperatures in air and thus in oxygen, it simply burns, forming
comparatively thick iron oxides called "scale". Scale can grow rather thick; you can get fractions of a millimeter inminutes!
If you bring scale-covered steel in close contact, not much will happen. However, if you put your iron in the reducing
part of you fire (deeper inside) in contrast to the oxidizing part (more on top of the flames) you minimize scaling. If
you also pour fine-grained "sand" that contains silicon dioxide (SiO2) on the hot steel, you may liquefy the scale. If
you now hit the two pieces hard with your hammer, the liquid stuff squirts out at the seams and you get the ironatoms into close contact. Plenty of thermal energy does the rest. Iron atoms will move and bond to other ironatoms. Welding is achieved.
If you keep your material hot enough for a while, grains grow. The grain boundaries formed during welding thus moveand become unrecognizable from the other ones. Taken all of that together, there are plenty of reasons why you
need to do hammer welding at elevated temperatures.
Of course, hitting hot steel with a hammer also produces a lot of dislocations—but so what! At high temperatures
they are likely to disappear quickly, and the steel structure changes completely anyway as soon as you go below
the austenite-ferrite transformation temperature at about 720 0C (1.328 0F).
However: Any slag particles locked in the seam will remain there.
So hammer welding works. But if you look at the silicon figure again, and consider that this was done under far more
perfect conditions than contact welding with steel but still has some "dirt" (silicon dioxide (SiO2) particles) in the weld
seam, you must expect that the a seam after hammer welding will not be overly perfect either.
This is indeed the case. Old pattern-welded blades, for example, are often more corroded down the hammer-weldseam than in the bulk of the blade. This signifies imperfect seams. If you can see a pattern in an X-ray image, it
signifies that corrosion was different in different parts because all kinds iron and (carbon steel) look exactly thesame in an X-ray image. Contrast differences then are exclusively due to differences in thickness since slag
particles are too small to show.

What the blade looks
like. Three layers of
torsion damascene arevisibleX-ray image. White
corresponds to thinnerparts.

Parts of a Viking blade (8th - 9th century)
Source: The wonderful book of Manfred Sachse

You also can see slag particles in hammer-welded seams in a standard metallographic analysis. Here is one
example from Buchwald's first book

Iron, Steel and Swords script - Page 161

Seams in a hammer welded (heavily corroded)"Nydam" blade (300 AD)
Source: Buchwald's 1st book; p. 285 Not sure

On top the steel is carbon-rich "regular" steel. On the bottom the steel contains carbon and major amounts ofphosphorous. The arrows indicate weld seams. They all contain slag inclusions.
The ancient smiths' weren't doing badly, however. Relative to what I could do under
optimal condition with silicon in 1977, they were even doing fabulously! The few
investigations made into ancient pattern-welded seams show extremely high quality
and almost perfect hammer welding in some cases - and extremely lousy jobs inothers.
I will have much more to say about hammer welding in the context of pattern-weldedswords. In particular that the ancient smiths', for all we know, could not possibly havedone it.
Since pretty much all remaining iron and steel artifacts from antiquity prove beyond
doubt that these smiths did hammer weld their iron and steel object, it becomes clear athis point that we do not know enough!

Iron, Steel and Swords script - Page 162

Advanced
Link
Fire welding6.3 Surprise?

6.3.1 Nirvana once more
Did you get what I did in the preceding chapters? Did you notice that I quietly and unobtrusively changed the topic? I
moved from nirvana considerations to real life where nirvana is rarely achieved.
Let's recall: Nirvana for all materials, including iron and steel, is this best-of-all states, the best way to arrange youratoms. Or, if you want to read the more fancy definition again: the state with the absolute minimum of the "freeenthalpy" or simply "thermodynamic equilibrium".
For a piece of pure iron, nirvana would imply an infinitely large perfect single crystal containing only the required
number of vacancies if it has some temperature.
For a piece of carbon steel, i.e. iron plus about 1 wt% carbon in the iron, nirvana would be the basic structure as
outlined in the phase diagram. It would consist of a perfect ferrite single crystal with just one and then necessarily
big iron carbide (Fe3C, called cementite) precipitate in it. No grain boundaries, no dislocations, no nothing—except
the required vacancies according to temperature and a very few atomically dissolved carbon atoms according to thephase diagram.
Let's CAPITALIZE this:Phase diagrams outline
only the nirvana structure.

In other words: From the phase diagram we know what (structure-wise) the steel should be.
We also know what you should be and a lot of people have told me what I should be. Worse, some people never tire totell me this every day (Daddy, don't drink so much beer!). The problem is: I'm just not what I should be, and I never willbe. I suspect the same is true for you.
I do try do improve, however. At least that's what I tell others. But despite strong or feeble efforts, we never seem toquite get there.
The problem is that in order to get more perfect, we must change something. This requires some effort and sometime. Even if I seriously start dieting, I will not lose excess material over night. It takes time and energy to get
results. If you need to lose a lot of surplus you, it takes more time and energy.
How hard we try to get better depends on the magnitude of the "driving forces" we experience. If you cough a lot
and your doctor tells you that you are developing lung cancer, the driving force for quitting smoking is a lot stronger
than when you feel in top conditions.
The grand total of this little consideration is:
The path to nirvana is the interesting part of your existence. It is a process that requires change.
All changes start with a first step, and that is often the most difficult part of the process. A little help from theoutside can be very valuable.
Where you will find yourself on the way to nirvana depends on:- How far from nirvana you presently are.
- How large the driving force is that pushes you there.
- The help or the obstacles you might encounter.
I'm not sure if Buddhists would agree with my point of view here as far as people are concerned. As far as materials
are concerned: this is it!
Crystals are no smarter than most humans and behave as outlined above. The big differences to humans are:All crystals are equal (really!) under the (second) law.
All crystals in identical circumstances do exactly the same thing.
We (meaning a few humans) can calculate precisely what they are going to do. At least in principle, if not (yet) inreality.

Iron, Steel and Swords script - Page 163

Take your average steel crystal. It's a poly crystal for reasons already discussed , and it is full of dislocations for many
possible reasons. Maybe because you, the smith, beat it up.
Its surplus carbon may have precipitated. If so, it's certainly not just one big lump but many smaller ones.
In other words: our average real steel crystal is not enjoying nirvana at all—just like you and me. It is trying toachieve nirvana, however—just like you and me. It will never quite reach it—just... OK. you get the point. To drivethat point home, let's reconfigure the list from above:
The way to nirvana is the interesting part in processing steel. The structure must change on going there, andfor this atoms must move .
All structural changes start with initiating or nucleating the required structure (e.g. a new lattice type) insome small region. This first step is often the most difficult part of the process. A little help from the outside
can be very valuable. I have covered that here.
Where you will find your steel on its way to nirvana depends on:- How far away from nirvana is it? (In scientese: How much higher is the "free enthalpy" compared to what it
would be at nirvana?)- How large is the driving force for inducing changes. This is similar to the point above and roughly given by
the "distance" to nirvana.
- Do you have some help like vacancies that make the atoms mobile or are there obstacles like slag
inclusion?
All in all, the pathway of a material to nirvana is a process, too. Things need to change and for a crystal that means thatits structure needs to change. This can only happen if the distribution of its atoms changes and that involves that atoms
move.
Here we go again. But now we know a thing or two and can give the kinetics of sword making a closer look.

The way things change on the way
to nirvana is called kinetics

In the preceding chapters I have inched more and more away from just looking at nirvana and moved closer and closer toprocesses and their kinetics. For the rest of this book that will be our main topic. There is a simple reason:

Nirvana is boring!

Did you ever notice that in all medieval paintings depicting heaven and hell, it is always far more lively down in thepit? OK, it's hot and doesn't smell so good but at least there is some action. How long can you take it to sit on a
cloud in a white night gown, singing hosanna, and not doing much else? In particular not doing a bit of sinning along
the time-honored wine, women and song line? Right. Me neither.
And let's not forget that members of the other sex, who are very pious and close to God / nirvana, are usually boring
if not outright useless already in this life for what you may have in mind.
It's the same thing for steel. Nirvana steel is bad steel as far as sword making is concerned. However, steel far off
the nirvana state is not necessarily good sword steel either. While there is only one proper nirvana state, there are
zillions of non-nirvana states and some are better than others for what we have in mind.
It is a little bit like women. Most are not perfect (fortunately) but what kind of non-perfection is best for you depends
on what you want to do. Conceive and raise a true-blooded heir? Have an intellectual discussion about gendermainstreaming? Getting your laundry done? Engage into you-know-what, possibly repeatedly, without generating
heirs of any kind? That's why in the good old times the sword bearers often had several ladies in attendance.
Nowadays we have at least several kinds of steel.
So what the modern smiths Materials Scientist and Engineers need to do, after they figured out the properties that theirwomen steel needs to have, is:
1.
2.
3.
4.

Figure out what kind of state the steel you want needs to be in.
Figure out what kind of state the steel you have is in.
Figure out how to get from here to there,
and, being practical, figure out how one gets from here to there cheaply. That might mean to compromise a bit,maybe, and getting only almost there.
Iron, Steel and Swords script - Page 164

4.
Unfortunately, this didn't help you, the ancient smith, very much. Mostly because you didn't even know what steel
is. What you , the ancient smith, needed to do is:
1. Learn and practice for many years, following the time honored "learning by doing and getting kicked in therear by the master" concept.
2. Do everything exactly as taught by your master. Give him gifts. Find a better master if you want to makebetter swords. Give him more gifts.
3. Hope that the quality of the iron / steel you buy or make is not going down for unknown reasons. Pray a lot.
Live a quiet life.
4. If you are the enterprising type, try small variations of the process as you learned it from your master, andthen hope for the best. Pray to your God to collect your customers if the swords you made for them proved to
be inferior, keeping them from getting back at you. Pray a lot more and bribe somebody
5. If your swords break frequently and your customers survive, run and hide. Pray a hell of a lot, makesacrifices, bribe important people. If you still have money, have a (fitted) sarcophagus made.
What I am are going to do now, schlepping you along if you like, is to look a bit more closely into the kinetics of steel
making.

Iron, Steel and Swords script - Page 165

7. Rubbing It In
7.1 Phase Diagram and the Structure of Carbon Steel7.1.1 Experimental Evaluation of Structures and Relation to Phase Diagram
7.1.2 A Lustrous Surprise

7.2 How Do You Like Your Mix?
7.2.1 Hypo and Hyper
7.2.2 Mixed Blessings

Iron, Steel and Swords script - Page 166

7. Rubbing It In
7.1 Phase Diagram and the Structure of Carbon Steel7.1.1 Experimental Evaluation of Structures and Relation to Phase Diagram
Looking at Structures
In the preceding chapters you learned a lot about phase diagrams. No let's apply that to steel. Let's see what we canlearn about the general structure of steel from the phase diagram and from other resources.
How do we assess the structure of steel? Or of any other material? Well, you need to look at it. In chapter 4.1.1 wealready looked at steel - with a transmission electron microscope at very high magnifications (> 10.000.000) and we saw
a few of its atoms. They had a size of about 0.2 nm or 200 picometer (pm) and if you like, you can now impress your girlfriend (your wife is probably not any more impressed by anything you do or say) by stating that you, personally, know
about the pico structure of steel, something way better than just the ubiquitious nano everybody talks about.
But beware! You can't impress me or my buddies. We know that at very high magnification all crystals look pretty muchthe same. It's just like looking at, for example, this major piece of art at high magnification. Whatever part you look at, it
looks pretty much like the pictures shown here. You really miss something by looking too closely!
Same thing for steel. Looking at its atoms is fun when you do it for the first time but quickly becomes boring. All atoms
are rather alike after all; if you have seen one, you have seen them all. So now we take steels samples and look at their(comparatively coarse) micro structure with an optical microscope at magnifications not exceeding 1000-fold. That was
the best one could do up to about 1960, and it is still the first thing you do when you want to find out about the structureof steel.
Anything smaller than about 1 µm (or about 4.000 atoms in a row) is invisible in an optical microscope. But neverfear, enough structural details are visible to make your mind boggle - provided we first prepare the specimen for
the examination.
For that we first polish the specimen to a high sheen. This can be done in several
ways and the results may look the same to the naked eye - but not to themicroscope! You can, for example, achieve a nice shiny surface by just holding
your specimen against a rotating brush for a while. Easy - but useless for structuralinvestigations
Polishing properly for structural investigations is not all that easy. This is why I
decided to give you an extra module for this topic.
After perfect polishing we have a perfectly flat and structureless surface that justterminates the crystal without producing any damage of its own in surface nearlayers. You can now look at it with your optical microscope and what you will see
is exactly nothing . That's the meaning of the word "structureless".

Advanced
Link
Polishing

Now we need to invoke a bit of black art. We concoct a potion, called a defect etchant, that has certain magicalproperties. For example, if you drink it during a full moon at midnight in a cemetery, you will be dead. It even works
if there is no full moon, everywhere and at any hour! Defect etchants are typically rather aggressive so don't foolaround with defect etching if you don't know exactly what you are doing.
Let's not drink it but apply it to our polished steel (after we cleaned the polished surface in more or less trickyways). If your "etchant " (for short) for carbon steel was cooked up the right way, and you immerse your polishedsample in it, it will now do the following:
It dissolves the ferrite (the relatively pure iron) a little bit, meaning very slowly and with somewhat different
rates depending on the crystal orientation of the grains.
It dissolves the cementite (iron carbide or Fe3C) precipitates not at all.
It dissolves the ferrite next to grain boundaries rather quickly.
It dissolves the ferrite around other defects coming up to the surface rather quickly, too.
Schematically, this is what happens

Iron, Steel and Swords script - Page 167

Defect or structure etching
The light blue stuff is cementite, the line symbolizes
a grain boundary or dislocation, and the red thing issome precipitate.

In reality you might see something like this:Optical micrograph of etched medium carbon
steel

The black stuff is cementite; grain boundaries are not really visible here. The cementite shows a kind of "zebra"
structure (I'll come to that soon). If the lamellae in that structure would be a little bit smaller, the light microscope
couldn't resolve the structure anymore. What you see then looks like this:Optical micrograph of etched low carbon steel
The black patch is a grain filled with cementite
lamellae too small to be resolved. The grain boundaries
are well visible now because the sample was etchedmuch longer..

Nowadays we have scanning electron microscopes (SEM) that allow to look at surfaces with a resolution far better
than that of a light microscope. They are also far more expensive than a light microscope and it is more time
consuming to use one.
This is what you might see in a case where you wouldn't see much in a light microscope:
Iron, Steel and Swords script - Page 168

SEM micrograph of etched low carbon steel
It is clear that the (white) cementite has resisted
etching and sticks out. At grain boundaries are steps,
indicating that different crystal orientations etch at
different rates.

The two examples already show that structure etching (also called defect etching) is an extremely powerful
technique! Generations of Materials Scientists (then also called Metallographers ) relied on it and most of ourempirical knowledge base about steel and pretty much all other metals, semiconductors and ceramics comes fromstructure etching.
However, you only see the structure that the etchant was designed to reveal. What will happen if you use theetchant that produced the pictures above for "carbon steel" when you use it for phosphorous steel? Or for stainlesssteel? Or...? There is no guarantee that some "carbon steel" etchant works for these materials too.
You get it: there is work to be done.
Every material requires its own etchant. Since there are no simple guidelines forconcocting these potions, and since tiny details matter a lot, defect etching still
counts among the black arts in modern science. Of course, after long years ofapplying it to iron and steel, the art of brewing and applying the various concoctions
for steel are now taught in undergraduate classes at Hogwarts and at all Materials
Science and Engineering Institutes. But it is still very advanced magic to come up
with a new brew for some new kind material. Take gallium nitride (GaN) as an
example for a material that became very important recently (look it up!). There is
not yet a good defect etchant out there.
The science module gives you details about defect etching of steel.

Science Link
Etching steel

What I just did was to give you an idea that when you stare into your microscope, most of the difficult work has alreadybeen done. Every idiot actor or actress pretending to be a scientist can stare into a microscope. If there is a decent
specimen under the lens, he or she cannot avoid to see something. But specimen preparation comes first and that
requires time and some skills that are not all that easily acquired. Same thing for the interpretations of what you see.
In chapter 3 we have tortured steel and innocent bystanders by pulling them up to the breaking point. Now let's look atwhat has happened to the microstructure of the specimens sentenced to a tensile tests. We want to know how the
microstructure changes during the various phases of plastic deformation and fracture. This is going to be real work!
We have specimens from several types of steel and we need to look at their structure before we did the tensile test
and after we elongated them plastically just a little bit, a bit more, up to a lot . We should look at the pieces after
they fractured, and on elongated specimens after we heated them for a while at some temperature, including theprocess called normalizing, and so on.
Each time we have to cut a sample, grind and polish it, etch it, look at it, take pictures and discuss them. Not a big
deal scientifically - but a lot of work.
You should certainly do that yourself for a while. It's the only way to get a feeling for what can be done. But when
you become a Professor, it is better to train a lab technician for the job. He (and especially she) will be far better(and cheaper) than you at doing this kind of work.
Going through the program above she will also produce far more pictures than I can include here. It is also not muchfun to go through umpteenth pictures, discussing every one at length. You know this if you have ever been the targetof a slide show by a well meaning relative.
Iron, Steel and Swords script - Page 169

It's also a lot of work to find out what kind of structural changes occur between high and low temperatures for a given
piece of steel from only evaluating all these pictures. So let's invoke our central science dogma. Since there isnothing more practical than a good theory, let's first look at the phase diagram and see if we can deduce what weshould see. If we can do this with confidence, we don't need to look at too many pictures. Same thing for
deformation experiments. If you know the theory, you only need to analyze a few relevant samples to get you
oriented.
Predicting Structures
Below is the relevant part of the iron-carbon phase diagram around the especially important eutectoid composition. Let'ssee if we can predict what kind of structure we will get, taking into account that the crystal will never make it to nirvana
proper. Why? Because for nirvana we know the structure: Just perfect big crystals of whatever phases we need.

What happens at the eutectoid composition.

First, we look at a steel with the so-called eutectoid composition, meaning the composition at about 0,7 wt % carbon.
That's where the γ phase can change into the mixed α+ cementite phase directly, without having to go through the α + γ
or γ + Fe3C region. This is indicated by the green line.
This is exactly the same thing that we found for the case of an eutectic composition not so long ago - except that thephase change here is not from liquid to solid but from solid to solid. That's why we call it eutectoid instead of eutectic,
just as you might call (insert politician or banker of your choice) humanoid (= similar to humans) instead of human.
While we are at it, here are two more "oids":
Steel with less than 0,7 % carbon we call hypoeutectoid. Should there be more than 0,7 % carbon, the steel is
hyper eutectoid.
Sorry for throwing Greek at you once more, but in this case it's easy:"Hypo" means "below" or "under" as in "hypodermic", under the skin.
"Hyper" means "above" or "excessive", as in "hyperactive ".
OK - once more so you get it: (">" and "<" mean "larger as" or "smaller as", respectively):
Hypereutectoid steel has more carbon than the eutectoid composition; i.e. a carbon concentrations > 0,7 %Hypoeutectoid steel has less carbon than the eutectoid composition; i.e. carbon
concentrations < 0,7 %Yes, I could have used everyday words like "proper", "low" and "high" instead of "eutectoid", "hypoeutectoid" and"hypereutectoid" carbon steels, respectively. But if you want to be a member of the gang you must learn its slang.
If we have the eutectoid composition and hold it above the transition temperature around 1000 K (727 oC, 1341 oF), we
will find the γ structure called austenite. At this temperature we also have enough mobile vacancies to allow somemotion or diffusion of the atoms. Our steel will then happily work on changing the microstructure of the austenite to anirvana structure. It will not succeed in finite times but getting close.
If we allow it some time, we could reasonably expect that its structure will consist of big grains of the pure γ-phaseor austenite, and that it will be rather free of dislocations or other big defects.
I'd love to show you a picture of this serene state of being, but it's rather hard to look at red-hot things close-up witha microscope. It is actually impossible. We could get a picture with tricky and expensive equipment involving X-rays
and so on, but why should we bother? Why should we spend a lot of (your) money and (our) time to show thatthings really are what they simply must be? Behold the wisdom of the central dogma!

Iron, Steel and Swords script - Page 170

The best I can do is to show you a picture of the austenite structure as we find it in some alloy steels ("stainlesssteel" or "austenitic steel" variants) at room temperature. If you add substantial amounts of alloy elements likenickel (Ni) and chromium (Cr) to the iron-carbon mix, the transition temperature for the austenite → ferrite + Fe3C
phase transition goes down to values where it cannot take place anymore (too cold to move). Austenite then exists
at room temperature as a metastable phase. We cannot expect it, however, to be as perfect as the real thing at
those low temperatures.
Nevertheless, here goes. The following picture shows what a rather perfect austenite structure looks like under alight optical microscope at low magnification:

Structure of metastable austenite at room
temperature.
Big grains, a few blackish things (whatever they mightbe; I don't know either, we haven't been introduced)
and some "grizzle" in the background signifying a bit
less than perfect polishing or God knows what.

This could be austenitic stainless steel from your kitchen sink. It looks polished because it is polished and thus would
show no structure under the microscope. We know already why we see something here.
Once more we see the structure after defect etching. As stated above, in order to render the bigger defects visible,
we need to etch our specimen after we polished it to a high sheen. Grain boundaries then typically produce tiny
grooves and steps that appear as the black lines in the optical micrograph above.
Note that I could easily cheat on you. I would never do that, of course, but what you see above could just as well bea picture of the microstructure of copper (Cu), gold, (Au), aluminum (Al), silicon (Si),..., whatever. There is no way oftelling just by looking at the picture. But you know that Materials Scientists and Engineers don't cheat people out of
their money since you rarely see them driving Lamborghinis or Porsches. So you can trust us in science matters,too.
If you're now inclined to send me (large) amounts of money, I will happily invest it for you.
So defect etching does help you to see at lot of structure on the surface - butbeware! You will not see everything. With a light optical microscope you cannot
see small "nano" things at all, even it they are properly etched. Then otherstructures might be there but might not have been revealed by the etchant. And
beware of the bane of all metallographers: artifacts! Things that are not there but
nevertheless show up.
Defect etching was and is crucial not only for iron and steel but also, for example,
in silicon technology. The link takes you deep into defect etching in silicon, theprobably most thoroughly investigated material in this respect.

Science Link
Etching Si

Be that as it may, what we see in the picture above is pretty much what we would have expected: We see a nice poly
crystal with irregular and rather large grains. Grain sizes around 40 µm - roughly the thickness of a hair - are considered
large
Nothing spectacular otherwise. The faint structure in the background may have some significance but it also could be an
artifact.
Nevertheless, the fact that we can see a good part of the structure of austenitic fcc steel (or other materials) after some
defect etching is of utmost importance: it started Materials Science!

Iron, Steel and Swords script - Page 171

Before about the middle of the 19th century, working with iron and steel was apurely empiric enterprise, based on experience and not much else. With the adventof microscopy, the science and technology of materials like steel started.
Researchers then had only optical microscopes to look at the microstructures ofthings (and no quantum theory, statistical thermodynamics and other basic tools).
Electron microscopes hadn't been invented (that had to wait until around 1960), notto mention high-resolution electron microscopes (HRTEM), that allow to see crystal
structures or atom columns directly, which were not available before 1975.
Come to think of it, even atoms hadn't been "invented" yet in the 19th century.
Ludwig Boltzmann, one of the most outspoken proponents of "atoms" assomething real, was ridiculed as late as the turn of the century (1900) not only by
Wilhelm Ostwald (of "Ostwald ripening" fame; I'll get to that) and Ernst Mach (ofsupersonic velocity fame) but also by no less a celebrity than Max Planck, who
opened the door to quantum theory but had a hard time to believe in the existenceof atoms.
It was Albert Einstein in 1905 who put an end to that and firmly established atoms
as being not only real physical entities but the only entities that exist besides
photons (which, incidentally, he introduced at the same time).

Science
Link
Microscopy

Misc. Link
Discovery ofatoms

Now I have a question for you: Did atoms (or about anything else in science) get "invented" or "discovered "? Arethey just figments of human thinking; social constructs that will be laughed at by scientists in the future, or are they
real entities, existing independent of humans at all times? This link will tell.
Without knowing about atoms you can't fully understand crystals. Without crystals you can't have crystal defects.
Without crystal defects you can't describe the microstructure of materials. Not knowing the microstructure of materials
prevents you from understanding most of their properties.
It doesn't prevent you from describing them, however. For example, by just doing measurements you can correlate thecarbon concentration and hardness and thus answer the "what" question. "What is carbon doing in iron"? "It makes it
harder"! You can even do that quantitatively with numbers. What you cannot do is answering the "why" questions. "Whyis carbon making steel harder"? "I don't know"!
So you, the not-so-ancient smith in the 19th century (now called Engineer), will prepare specimens, etch themsomehow, and put them under your microscope. If you do it right you are going to see things. Even if you don't havethe faintest idea what it really is that you see, you can always describe it in words and measure parameters likesize or distribution.
If you are among the first ones doing this, you are going to see things that nobody has seen before. If you missproper words for describing what you see, you just invent some new ones like "pearlite", "cementite", "martensite"or "bainite" (not to mention "ledeburite"). You still don't know what it is but now can talk and write about it - it's notunlike politics at this stage.
In what follows we look at optical "micrographs" like our early steel scientists and, while we are not going to see
atoms, small precipitates, dislocations and the like, I promise that what we are going to see will be quite enough tomake your head spin. In other words: we are looking at parts of the microstructure of iron / steel. For the rest we would
need to employ electron microscopy or other sophisticated techniques.
And in contrast to the pioneers of old we now know what we see! Well - make that: I know what we see, and I willtell you.

Iron, Steel and Swords script - Page 172

7.1.2 A Lustrous Surprise
Now let's look at the γ + cementite phase that we expect to be the stable (or "nirvana") phase at room temperature forour eutectoid composition.
If we cool the mix down very s l o w l y, giving the steel plenty of time to get close to nirvana, we see something
as shown below in our microscope (after polishing and defect etching, of course).

Structure of steel with the eutectoid composition
This is actually a picture from a scanning electron
microscope (SEM). In an optical microscope this structure
would not be clearly visible.
Here is another one
Source: Eyuep Duman, Diploma Thesis: "Druckabhaengigkeit der Invartypischen Instabilitaeten von Fe3C- (Zementit) Partikeln"; Physics
department; University Duisburg-Essen / Germany 2006. By
permisison; thanks for letting me use it.

Very pretty but I bet this is not what you expected, if you expected anything. Here is another picture from an ancientsword showing exactly the same kind of "zebra" pattern.
What you see is a kind of zebra pattern of dark and bright stripes inside different grains. It should produce a "déjàvue" feeling, however. We have looked at similar pictures before.
What I see is the classical ordered structure relating to eutectic or eutectoid points in a phase diagram. In the caseof steel we get a highly ordered layered structure of ferrite (dark) and cementite (white).
Next, let's look at a different sample at higher magnification in a scanning electron microscope or at the highest
magnification (about 1000×) in a light microscope:

Structure of hypoeutectoid steel

Iron, Steel and Swords script - Page 173

These pictures are from a commercial piece of medium carbon steel taken by a student of mine. There are some"normal" grains and some grains with the "zebra" structure.
In the SEM picture, the cementite is white and sticks out of the ferrite matrix. In the light microscope picture thecementite is black. In neither case has this color anything to do with the true color of the stuff.
Whatever else one could "see" in these pictures, one things is clear: What we do not have are large grains of ferriteinterspersed with some grains of cementite, as you were entitled to expect from the phase diagram. What we dohave is a structure that is not determined all that much by where the steel wanted to go ("nirvana", the ultimate goal)
but by kinetics, the available path to the goal.
Sometimes the path to paradise is meandering and stony. If you get stuck on the way, you may find yourself in very
different conditions compared to what you were aiming for.
How do I know what these pictures show? How do you know that I'm not pulling your leg? Well, without some additional
knowledge neither of us can tell. My additional knowledge comes from several sources. First, the theory behind phase
diagrams, nirvana and so on simply predicts what one should get, and second, we have far more advanced analytical
tools nowadays that allow me to check if I'm right.
Scanning electron microscopes , for example, only show the surface (in contrast to transmission electron
microscopes) but they may also reveal the chemical composition of what is there. Our colleagues 100 years ago did
not have this, they had to find the proper interpretation of their pictures by other means and lots of work.
The next pictures demonstrate that once more. You also see in the left-hand picture that "banging" the whole thingmechanically fractured the brittle cementite while the ferrite in between just deformed plastically by dislocations
running through it. That is an interpretation once more because you cannot see the dislocations in a SEM picture.
Cementite, as we ascertained before, is a crystal but does not support dislocation movement at room temperature.
It thus must be brittle like most ceramics, the material class it belongs to.
You can also see deep etch pits around cracks in the cementite. The cracks allows the etchant to penetrate deeper
into the material and to etch the ferrite "from the side".

Cementite platelets embedded in ferrite as seen witha SEM
Cold rolling (akin to banging
it with a hammer at room
temperature). The ferrite has
deformed plastically, thecementite actually fractured.

After slow cooling, just likein the optical microscope
picture above.

Source: M. Umemoto et al., Toyashi Uni. of Technology, "Mecanical
Properties of Cementite and Fabrications of Artificial Pearlite", Materials
Science Forum, Vol 426 - 432 (2003) pp 859 - 864

Here is the paper with more pictures
Now comes an important point: The rather typical "zebra" structure for ferrite + cementite (or α + Fe3 C in more prosaic
terms) found at the eutectoid composition and below the 727 oC (1341 oF) transition temperature has its own name; it iscalled pearlite because it shows a pearl-like luster.
Plenty of "why questions" come up:
Why do we find the pearlite structure and not some other structure?
Why does it have a pearl-like luster?
Come to think of it, why do pearls and nacre (=mother-of-pearl) show a "luster", while diamonds and toenails
don't?
Let's start with the last question first:
Nacre, the stuff pearls, mother-of-pearl, sea shells and some snail shells are made of, is alayered composite material - just as eutectoid steel. The distance between the layers of asoft protein and hard calcium phosphate is in the lower µm range, just like the distance
between the soft ferrite and hard cementite platelets in steel.
The wavelengths of visible light is also in this range, and that means we get interference
effects . In simpler words: the reflection of light from such surfaces changes with viewing
direction and the effect of that when we look at it we call luster. Nowadays we call structures
like this "photonic crystals", and the most amazing natural photonic crystals are perhaps
the wings of some butterflies and beetles, and in particular opal.

Iron, Steel and Swords script - Page 174

Advanced
Link
Photonic
crystals

Opals are crystals, yes, but not of atoms but of comparatively gigantic balls of amorphous glass in the form ofsilicon dioxide (known as quartz in its crystalline form, look at an old figure for the difference). The interference oflight caused by a periodic structure that is "coarse" enough to be on the same scale as the wavelengths of light(say around 100 nm - 1 µm) causes the luster or other remarkable optical effects of opals, pearls and nacre,butterfly wings, and pearlite.
Nacre, by the way, has another superficial relation to steel: it is composed of hard calcium phosphate platelets
embedded in a soft protein matrix, reminiscent of what you might associate with a damascene blade.

Mother-of-pearl (nacre) and opal as seen with a SEM.
Neatly packaged platelets ofrelatively hard calcium
phosphate are "glued"
together by (invisible) thinlayers of soft protein.

"Huge" spheres ofamorphous quartz (SiO2)
balls form an fcc crystal.
"Huge" refers to the fact thatthese spheres are about 600
times larger than the atoms
usually forming a crystal,
containing about
300.000.000 atoms.

Source: With permission from thegroup of my late friends U. Gösele
and J. Woltersdorf, MPI Halle,
Germany

Source: Internet at large

But I'm digressing. Let's consider the first question now. Why does an eutectoid iron-carbon mixture produce theintricate pearlite structure when it must change from simple austenite to ferrite + cementite? It's certainly not the nirvana
structure; that would be one large cementite precipitate in a ferrite matrix.
Well, the crystal invokes another well-known principle:

Principle of supreme laziness:
Don't spend a lot of energy for attaining the impossible.
Go for a compromise that needs the least effort.

Consider: The phase transformation in question involves a lot of work. The lattice type must change from fcc to bcc
wherever ferrite is to be made, and the surplus carbon must be expelled from the ferrite and moved to wherever a
cementite crystal is to be.
All of this involves moving atoms around:
All iron atoms must move somewhat to adopt to the new lattice type. Some must move a lot to make room
for the cementite.
The carbon atoms must move a lot to get away from the ferrite and into the cementite.
Making large grains of ferrite with some large cementite precipitates or grains in between, while good for nirvana,
simply involves too much work or moving around of atoms.
The crystal goes for a compromise.The typical eutectic structure that constitutes pearlite is the structure that
results when one optimizes the scale of the structure to be made to the distance the carbon atoms can move. We
called that quantity diffusion length. We thus expect structures on a scale that is comparable to the diffusion lengthof carbon interstitials, making sure that most if not all carbon atoms can make it to some evolving cementite.
The following figure shows how that leads to the layered structure:

Iron, Steel and Swords script - Page 175

Formation of the eutectic / eutectoid "zebra
pattern"by minimizing carbon diffusion
What is going on is rather clear. If the spacing of the cementite lamellae is no larger than the total diffusion lengths ofthe carbon atoms, all of them can get there.
This is something we can calculate; I actually did this in a science module.
Within reasonable cooling rates from about 1.000 0C (1832 0F), the master curve in the science module predicts
lamellae spacings between roughly 0.1 µm if you cool rather rapidly (50 K/s) and about 10 µm if you cool slowly (1K/s). That is just what you tend to find, look at the pictures above and elsewhere.
The principle of supreme laziness is related to "Occam's razor" (look it up yourself). While it is not a basic law ofnature, expressible in precise equations, it is a pretty good guideline with some philosophical implications.
Suppose, for example, you are almighty and about to make a universe, complete with galaxies, planets, living
beings, pizza, beer and red wine. You could, of course, simply put all the required atoms (around 1080 ) andphotons (far more) in the proper place. That's certainly a thing an almighty being can do - but it is a lot of work.
So if you are an almighty being but somewhat lazy, you just make a few basic laws (like the first and second law)and some universal constants like the speed of light or the Boltzmann constant (plus, perhaps, some pizza and redwine).
All you have to do after that is to relax, enjoy your food, and wait. After 15 billion years or so, your universe will havemade itself, complete with galaxies, planets, iron (quite a lot, in fact), living beings, tele evangelists, bankers andslugs.
Now, if you are an almighty being and extremely lazy, you make nothing at all. You just wait a bit longer. A lot of
universes of all kinds will form all the time and eventually there will be one with pizza, wine, the natural laws as weknow them, lawyers and hemorrhoids.
Finally, if you are an almighty being and almighty lazy, you don't even bother to make yourself. The odds are that
there will still be a universe with me in it eventually.
No - don't throw lightning bolts at me, or whatever else you have, for these blasphemous thoughts. The culprit is actuallyPeter Atkins who goes on about that (and the first and second law) in his wonderful books at length.
While I was taking you into the rather lofty realm of universe making, you probably wondered why I did not pose anotherquestion up there:
What are the mechanical properties of pearlite?
I do not need to ask this question because we know the answer from theory! We have areas were dislocations canmove freely, and areas where they can't move at all. The material will be rather hard. There is some ductility but far
less than in soft ferrite.
That's a bit brusque for now but I will get back to it in due time.

Iron, Steel and Swords script - Page 176

7.2 How Do You Like Your Mix?

7.2.1 Hypo and Hyper
Deducing Steel Structures
After we dealt with the eutectoid composition , we must give a quick look to hypoeutectoid and hypereutectoid steel
during a slow cooling down.
Let's start from a state point well inside the pure γ phase in both cases.
For the hypo ("below") case (blue state point), some primary ferrite (light blue in the picture below) must
form as soon as the γ → α + γtransition temperature is reached.
For the hyper ("excessive") case (red state point), primary cementite (pink in the picture below) must form
as soon as the γ → γ + Fe3C transition temperature is reached.
You know by now that in both cases the nucleation of the new phase occurs most easily at the grainboundaries and especially at the nodes of grain boundaries of the austenite. Later we will see that certain
impurity atoms also help to form cemenite.
As soon as both steels hit the all-important 1000 K (727 oC, 1341 oF) transformation temperature, the still present
austenite in both cases must change to a ferrite-cementite mixture (striped in the picture below ). This is shown in
the figure below.

Formation of the structure of hypoeutectic andhypereutectic steel
during slow cooling down.
I'm going to discuss that figure in some detail by looking at the various state points in the phase diagram and the(schematic!) structure going with them as shown to the left and right of the phase diagram
In both case we start with pure austenite or fcc iron with some dissolved carbon at a temperature somewhat above
1200 0C (2192 0C) We can't image the structure at such a high temperature but we can be sure that it consists oflarge grains without many defects. This is indicated by the two topmost structure figures.
Some time after we started cooling, the state points hit the line separating the pure austenite region from the two
mixed phases regions α + γfor the hypo, and γ + Fe3C for the hyper composition. We now need to form some αferrite or some Fe 3C cementite, respectively. How much of these new phases are needed will be given by the "leverrule" that we will get to know quite soon.
Whatever, in the beginning we don't need all that much and the precipitation of the new phases will start at good
nucleation sites, in particular grain boundary nodes. This is shown in the second structure figure in going
downwards.
As the state points move to lower temperatures within the mixed phase regions, more ferrite or cementite needs tobe formed, and the new phases grow. This may happen along the grain boundaries (indicated in the third structure
figure on the right), more uniformly (right figure), or in some other way.
Eventually we hit the temperature where the transition to α ferrite and cementite occurs in both cases (slightly below
1000 K in the figure). We know the composition of the γ phase at this point: it must have exactly the eutectoid
composition in both cases.
In the hypo case the carbon concentration in the austenite needed to increase to get to this composition. Sincecarbon-poor ferrite was formed, this could happen. In the hyper case it is the same thing, just with signs reversed.
The carbon concentration in the austenite needed to go down, and it could do so because carbon-rich cementite
was formed.
We thus find just the proper amount of ferrite or cementite, distributed as shown, before the transition occurs.
Iron, Steel and Swords script - Page 177

Now we go below the 1000 K transition temperature. In both cases the final structure must consist of α ferrite and
Fe3C cementite - just the amounts must be different.
The principle of supreme laziness dictates to leave the primary ferrite or primary cementite as it is. In both cases
then only the remaining austenite with the eutectoid composition must change into ferrite and cementite.
It will do that exactly as it did when we had the eutectoid composition from the very beginning. In other words, it willchange into pearlite. This is schematically shown in the last structure figures above.
The pearlite then consists of secondary ferrite plus cementite, for the hypo case, and secondary cementite
plus ferrite in the hyper case. The primary ferrite and the primary cementite, respectively, remain unchanged
What we will get then is:
For the hypo case (blue state point): pearlite embedded in primary ferrite
For the hyper case (red state point): pearlite with some primary cementite in between.
Once more we assume that the new phases nucleate at grain boundaries and then grow (we will have a closer look atthat soon). What the structure really looks like is shown below.
First the hypo case:

Structure of hypoeutectoid steel
The top picture was taken with a scanning electron microscope at a (medium) magnification sufficient to resolve
pearlite with a lamella spacing of about 0.5 µm. The bottom picture comes from a light microscope at low
magnification (200x).
The structureless grains are primary ferrite; the "zebra" or black grains are pearlite, with an unresolved "zebra
pattern" in the lower picture. Note that not all grain boundaries are easily visible.
Now to the structure of hypereutectoid steel. Here is a light microscope picture at medium magnification

Structure of hypereutectoid steel (lightmicroscope, medium magnification)
The white areas a pure cementite
Source: Dr R F Cochrane, Department of Materials, University ofLeeds; by permission

Iron, Steel and Swords script - Page 178

The white stuff completely encasing the grain boundaries is primary cementite. The rest (dark) is pearlite (notresolved) with a few pure cementite inclusions.
Pseudo Phases
My use of the word "pearlite" in all of the above cunningly prepared you for an important new idea:

For practical reasons, weconsider pearlite to be aphase in its own right.
Pearlite is not a real phase, of course, since it consists of two "real" phases - but what the heck. For all practical
purposes pearlite behaves just like a real phase. One might call it a pseudo phase but one usually doesn't.
In the phase diagram, pearlite as a phase would be a vertical line, just like cementite. If we draw pearlite as a phase
into the the phase diagram below, the decomposition of the high temperature mixed phases into ferrite andcementite (Fe3C) as shown several times before, can now be simplified into a decomposition into ferrite and pearlite
for hypoeutectic steels, or into pearlite and cementite (Fe3C) for hypereutectic steels, respectively.
Just to be on the safe side, here is the figure illustrating thisPhase diagram for hypo- and hypereutectoid steel
with pearlite as additional "phase".
If you could follow me that far, you are no ready for parts of a basic Materials Science exam. Try it. It's fun.

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7.2.2 Mixed Blessings
What Could happen
Carbon steel is composed of something soft and ductile: ferrite, and something brittle and hard: cementite. Even readers
given to the bulk intake of beer during reading non-fiction (or fiction, not that I blame them) got that by now. Steel is akind of composite material; a material made by somehow joining two different materials.
On a microscopic scale steel is thus exactly what the various "damascene" techniques of joining hard and relatively
brittle with soft and ductile steel are supposed to do on a macroscopic scale. It is always assumed that this bringsout the best of both materials, and that the product would now be hard and ductile and not soft and brittle

Why?

Why shouldn't it be soft and brittle?
Whenever we make a composite material it contains a least two phases, in contrast to a chemical compound, which isa one-phase material. An ideal composite material is made from at least two uniform materials that have different
properties. The composite material will have properties different from that of its "parents" but there is no reason why itshould always inherit the "good" properties of its parent.
Why should it combine just the best of the parents? Just look at your kids. Someof mine are actually female, do not like beer and red wine, and never showed any
interest in the science of steel!
To be sure, composite properties of materials will be determined to a large extent
by the properties of the parents. But how they come out in the end is also
determined by the (micro) structure of the composite, very much so.
This is easy to see for a composite with parents that are hard & brittle and soft &ductile.

Advanced
Link
Composite
Materials

If you don't see this right away, do a little (brain) experiment. Build two walls orhouses
1. The first wall you make with hard and brittle rocks or cinder blocks that are held together by some kind of
rubbery mortar or glue. You also might fill the interstices of a (yielding) wooden framework structure with(unyielding) bricks.
2. The second wall you make with soft rubber bricks that are held together by hard and brittle mortar. You also
might encase (yielding) iron rods into (unyielding) concrete.
Which wall will be rather hard but will yield elastically or plastically to some pressure without breaking, and which
one will be brittle and break immediately into pieces if forces exceed some limit?
Right. Structure (in the case of kids called upbringing or nurture) matters just as much as the properties passed onfrom the parents (in the case of kids called genes or nature). This is illustrated below.
By the way, did you note that I have just settled the old "nature or nurture" debate?

Wood - brick composite

Iron, Steel and Swords script - Page 180

Brick - mortar composite
Warped old houses in Lüneburg, Germany.

A picture of all steel reinforced concrete constructions still standing after experiencing what the twohouses above went through.

A lot of houses like the ones above survived heavy bombing during WW II - warped, bent and damaged, but standing- while concrete buildings either stayed unwarped as before or collapsed completely.
We want hard but ductile steel. Our ingredients so far are soft and very ductile ferrite, comparatively hard and somewhat
brittle pearlite, and really hard and fully brittle cementite. We want to combine these ingredients in such a way that weemulate wall structure No 1 and never get No. 2. So let's see what that implies:
Hyopeutectoid steel: We need to embed the comparatively hard and somewhat brittle pearlite into a matrix of softand ductile ferrite, just as shown in this picture. Good ductility at medium hardness can be expected
Eutectoid steel: You have little choice here. From what we considered so far you get pearlite all over, as seen inthese pictures. Good hardness and reduced ductility should result.
Hypereutectoid steel: You definitely want the really hard and fully brittle cementite distributed in the pearlite likein this picture od wootz steel. What you don't want are closed shells of cementite around the pearlite as shown
here since this must lead to rather hard but completely brittle steel. But that is what you will get if you don't pay
close attentention.
These microstructures then might bring out the best of the three phases we have at our disposal: hard - but not brittle.
The question now is how to make them. As you know by now, the crystal itself is not going to be overly helpful in thisbusiness.
Mother nature knows how to deal with question like this.
Nacre, a compound material of soft proteins and hard calcium carbonate (CaCO3), not only gives mother-of-pearl
its luster but also its strength. It consists of hard and brittle calcium phosphate platelets embedded in a soft matrixof proteins and thus comes pretty close to the first type of wall constructed above.
Nature uses that principle quite a bit. We also find in bones, for example, except that instead of calcium carbonate
you have variants of calcium phosphate (knon as apatite) in bone. The proteins are mostly collagen.
Calcium phosphate, by the way, is a chemical compound you are very familiar with. You imbibe (dissolved) calcium
phosphate in one form or other when your drink milk or eat milk products. It comes in several variants, e.g. as
CaHPO4 or "hydroxyapatite" (Ca10(PO4)6(OH) 2). Your tooth enamel is made from the stuff, just with less protein.
All variants are hard and brittle.
Fresh bones are rather tough and flexible. I avoid the word ductile here because the crystalline part is not ductile atall, i.e. its dislocations can't move, and the organic part is not crystalline, so there is no plastic deformation or
ductility by dislocations. That doesn't mean that organic or amorphous material cannot deform plastically at all, only
Iron, Steel and Swords script - Page 181

that the mechanism is completely different from that of crystals.
You know that. Breaking that turkey wishbone after Thanksgiving is far easier if you let it dry for a few days. The softand flexible protein (mostly collagen) stuff in between the hard bone stuff ("hydroxyapatite") then has decayed andthe formerly tough and somewhat flexible bone becomes quite brittle and easy to snap.
Isn't that great? Now we start to understand the principle behind the damascene technique or composite steel as I willcall it from now on, the mixing of different steel variants.
Well—not really. In the case of nacre and many technical composite materials, the focus is primarily on optimizing
Young's modulus or the stiffness of the material, together with the fracture toughness.
Composite materials like nacre or carbon-fiber-reinforced plastic (CFP) have a far larger effective Young's modulus
compared to the "parent" protein or plastic, respectively. It is primarily the stiffness of the composite material that
has improved. It also doesn't fracture as as easily as the very stiff but brittle "parents" phosphates or carbon,
respectively.
In composite steel we cannot change Young's modulus or the stiffness very much because we still have mostly iron.
Use this link if you forgot this. So making better swords by using composite steel techniques must have some otherrationale behind it.
If we now look at the hardness of composites and not at Young's modulus, we first need to recall that hardness formetals is
1. just another word for "yield stress", and2. the yield stress is the stress that enables dislocations to move.
Cementite is brittle and that translates to: dislocation movement in cementite is impossible. It follows that pearlite
must be harder than ferrite because the cementite in there cannot but act as an insurmountable barrier for
dislocations, and that will make their movement more difficult.
While dislocations cannot move across the cementite lamellae in pearlite, they can go around—it's just harder to do(pun intended). So even eutectoid pearlite is still ductile to some extent.
Now let's look at hypo- and hpyereutectic steel or, as we just learned, at pearlite embedded in ferrite or pearlite withprimary cementite, respectively.
Hypoeutectic steel is simple. The primary ferrite grains are soft, dislocations can move easily. The hardness of
hypoeutectic steel will be some average of the hardness of ferrite and that of pearlite. What you get will also depend
somewhat on structure parameters like grain size, of course
The hypereutectic case is trickier. If we embed something reasonably hard but still ductile like pearlite in something
very hard and brittle like cementite, the resulting composite would be very hard—but it would also be completely
brittle. This is so because the dislocations in the pearlite grains still could move but never could get out of the grain.
It's just like your rubber brick wall made with brittle mortar.
We will get exactly this undesirable situation if the primary cementite in hypereutectic steel does indeed nucleate at thegrain boundaries and then grows to envelop the grain into a brittle cementite shell. Unfortunately that's exactly what
hypereutetic steel does if left to its own, nirvana-seeking devices. Here is a remarkable picture showing just that:Three-dimensional rendering of cementite
completely enclosing a pearlite grain.
Source: The Naval Research Laboratory: 75 Years of Materials
Innovation; Bhatka B. Rath and Don J. DeYoung; JOM, 50 (7)(1998), pp. 14-19; by permission
Iron, Steel and Swords script - Page 182

This is a three-dimensional computer reconstruction of one-half of a hypereutectic steel grain, showing only the
cementite. It reveals the three-dimensional morphology and connectivity of the cementite plates masking the grainboundaries and shows a few lath-shaped cementite particles with the the "zebra" pattern typical for pearlite.
The grain is completely encased in cementite. In addition some pearlite structures are visible inside the grain. It is
not all pearlite because some of the secondary cementite re-enforced the primary cementite at the grain boundary.
How do you get a picture like this? Take a picture of the (defect etched) surface, polish off 0.2 µm material, takeanother picture. Repeat 150 times. Then process the individual pictures and feed them into a computer that
assembles the final compound picture (after it was fed with proper software for doing this). Obviously a task for
graduate students who will love it.
Four letter words come to mind now. Why? Because what this means is that you, the ancient smith attempting to makea wootz blade, have a big problem now. Considering that wootz steel with roughly 1,5 % - 2 % carbon is hypereutectic,
actually very much so, you are in big trouble. The stuff you are supposed to work with tends to be very hard but is totallybrittle. You just as well could make a blade from glass.
Turning wootz steel it into a hard but very flexible and tough material, as it is reported to be, obviously needs morethan just to let it cool down slowly. The trick is, quite obviously, to distribute the considerable amount of cementitethat the phase diagram requests for hypereutectic carbon steel in such a way that good properties emerge.
Just to make sure that you know what I'm talking about, the next figure schematically shows some possible ways of
distributing a certain amount of cementite in a matrix of austenite (or the final pearlite).

Four principally different ways of distributing brittle
cementite
The matrix could be austenite at high temperature or
pearlite at lower temperature. What is shown is:a) Austenite / pearlite grains and cementite grains. This
pretty much never happensb) Austenite / pearlite grains in a cementite shell. That's
what tends to happen. It is clear that this structure isbrittle and breaks easily.
c) Lots of little roundish (roundoid?) precipitates("spheroids") of cementite. That's what you find in wootz
steel.
d) Lots of little platelets / needles of cementite.

The matrix could be austenite at high temperature or pearlite at lower temperature.
It better be austenite at high temperature, however! Because if you cool below the transformation temperature, theremaining austenite just transforms into pearlite but leaves the primary cementite intact. It is thus essential tocontrol the structure of the primary cementite already at high temperatures; to do so at low temperatures is far moredifficult or impossible.
In other words: if you start the transformation to pearlite with a "bad" structure (like b), it is far more difficult or
impossible to turn it into one of the more desirable structures at the lower temperature.
Let's look at that in more detail. What we might find at room temperature in full accordance with the phase diagram are
structures like:

Iron, Steel and Swords script - Page 183

1. Just a random mixture of ferrite (yellow) and cementite grains without any pearlite. This is a conceivablestructure but never found. The principle of supreme laziness is very much against such a structure.
2. Pearlite grains (yellow) separated by cementite walls. That's what the crystal would produce if left to its own
devices; the picture above illustrates that rather nicely. But why? Why does the crystal want to make thisbad (for us) structure? We shall see.
3. Lots of small cementite particles embedded in large ferrite grains. Not something likely to occur either.
4. Lots of cementite particles - small, large, mixed, whatever - embedded in large pearlite grains. That's what wewould like have to some extent. The hard and brittle stuff completely embedded in the softer but still hard andstill ductile stuff. Wootz steel will fall in that category.
5. Long and interconnected cementite needles in pearlite (like a glass fiber network contained in epoxy). Not
likely to occur, even so there are recent reports about "cementite nanowires" in wootz blades.
6. Stacks of thin cementite platelets embedded in pearlite. Variant d) in the figure above could be seen as aschematic drawing of this case or number 5 just above since in a two-dimensional drawing you can't tell if
longish objects are needles or platelets seen "edge on".
7. Your proposal. I'm sure you can come up with something.
If you have a good memory, you notice that we are getting close once more to discussing optimization of your product.
What structure would we like to have? Why? And what do we have to do in order to obtain it?
The Lever Rule
Before we look ever deeper into those questions, we need to clear up one last point about phase diagrams.
Here, as in the various drawings shown all along, we mixed all kinds of phases—ferrite , austenite, cementite, pearlite—
in some ratio. What ratio exactly?
The time has come to produce the last rule for reading phase diagrams. You will now learn how much of each phase
we have in a two-phase region. This is not directly given by the composition. Knowing that you have, for example,
1,6 wt% carbon in iron, doesn't tell you how much of that carbon will be in the austenite or the liquid, respectively, at
1600 K. In other words. Just knowing the concentration of a component doesn't tell you how much of it you will findin the coexisting phases.
The phase diagram will tell you that. Here comes the simple lever rule:

Lever rule illustrated for a composition with 1,6
wt% carbon

Let's look at an example of a 1,6 % hypereutectoid carbon steel. That means that we have 1,6 g of carbon in a little lessthan 100 grams of iron.
In the mixed phase of ferrite + cementite that we expect at room temperature, how many grams of iron or cementite,
respectively, do we have?
Well. Let's do a little math: We have 100 grams altogether. Pretty much all of the 1,6 g of carbon is tied up in the
cementite or Fe3C. So every carbon atom in there ties up three iron atoms for cementite formation. In grams thatwould be…?
OK, enough math—you know where that would end. There is a much easier way: Look at the phase diagram anduse the lever rule. What that means is easy to understand, just look at the picture above.
Imagine that at the composition you're considering is the pivot of a seesaw, with the beam extending to the state
points of the two phases the system must decompose into (pearlite and cementite in this example). Balance theseesaw by putting the weights with the proper ratio (= ratio of the two beam lengths) on the beams, and you havethe weight ratio of the two phases in the composition.

Iron, Steel and Swords script - Page 184

Just looking shows that for 1,6 % carbon steel we need about seven times more pearlite than cementite. That's why
the primary cementite is not so prominent in the picture we had before; we simply do not need very much.
The time has come to tackle the big questions, alluded to above and before:

What structure is optimal for
sword making?
If I know what I want,
how can I make it?

Of course, that are not just the basic question for hypereutectic steel but for just about any steel in the context of sword
making.
Let's generalize a little bit and consider that your customers did not only want swords from you and yourcolleagues, but also knives, dinner plates, and tankards for beer. As time progressed and people got more civilized,
they wanted also wine glasses, bicycles, Mercedeses, solar cells, yachts, cell phones, power plants, machine
guns, wrist watches, airplanes and artificial knee joints; not to mention pace makers, viagra, and Wagner operas.
The two questions above then apply to just about everything that is made by scientists and engineers.
Replace "sword" by "product" and you have the Materials Science and Engineering mission statement.

Iron, Steel and Swords script - Page 185

8. Tuning Carbon Steel
8.1 Keeping Dislocations at Bay
8.1.1 Being a Drag
8.1.2 A Closer Look at the Second Law

8.2 Outwitting the Second Law
8.2.1 Strategies for Winning
8.2.2 Tempering and Ostwald Ripening
8.2.3 It's a Long way to Nirvana

8.3 Hardening Steel - the First8.3.1 Forming your Battle Line: Solid Solution and Precipitation Hardening.
8.3.2 Size Matters8.3.3 Bang it!

8.4 Be Cool!
8.4.1 Martensite
8.4.2 Multiculti in Steel
8.4.3 Feeling Stressed?

Iron, Steel and Swords script - Page 186

8. Tuning Carbon Steel
8.1 Keeping Dislocations at Bay

8.1.1 Being a Drag
There is an army standing along your eastern frontier. It's a mighty foe along a long line, with thousands of tanks, heavy
artillery, and plenty of soldiers.
You have a far smaller number of lightly equipped soldiers and not sufficient heavy stuff. You know that you cannot stopthe enemy when he advances; all you can do is to slow him down. You don't even want to stop him because in that casenuclear weapons would come into the play, completely breaking and destroying the country. How are you going todeploy your forces?
This was the rather real situation that the Germans faced during the cold war. They weren't supposed to do theimpossible and stop the Russians, all they had to do was slow them down (and die in the attempt) so NATO had
enough time to built up invincible forces along the Rhine, keeping those evil Russians out of France.
Stopping them was deemed not to be a good option because that would only have been possible with nuclear
weapons, completely destroying all of Germany for sure.
There is a long dislocation on the left side of a crystal, ready to move to the right, deforming the crystal in the process.
You only have some foreign atoms that you can deploy in order to slow it down. Stopping the dislocation is not a good
option because the result would be fracture, destroying the crystal.
What are you going to do in either case?
You could deploy your soldiers one by one, spreadingthem randomly and uniformly across the terrain.
They can move around freely (including running away)
and they might just slow down the advancing line ofenemy forces somewhat.
If your soldiers are well trained and motivated theeffect might be quite noticeable.

You could deploy your your foreign atoms one by one,spreading them randomly and uniformly across the
crystal.
They can move around freely (including running away)
and they might just slow down the advancing
dislocation line somewhat.
If your foreign atoms distort the lattice quite a bit, theeffect might be quite noticeable.

It's a strategy hat would give some results. Nevertheless, it is probably not your best strategy. So let's look foralternatives.
You can also get all your soldiers into one place,where they build an invincible fortress.
The advancing line of the enemy then will go aroundyour fort, leaving a ring of soldiers behind to keep you
under cover.

You can precipitate all your impurity atoms into one
big precipitate that the dislocation can never cross.
The advancing dislocation line then will go around yourbig precipitate, leaving a dislocation loop behind tokeep you under cover.

That is obviously not the best strategy either. It is now quite clear what you have to do.
Form many small groups of soldiers and dig them in.
That will really slow down the enemy as he has totake them one by one—and that's not going to beeasy.

Form many immobile small precipitates . That will
really slow down the dislocation since it has toovercome each precipitate one by one—and that's notgoing to be easy.

Of course, if you don't live in flatland as shown in the figure below but in a mountainous region, a major insurmountable
mountain also hinders the enemy's progress. In crystal terms that means a second phase (or a really huge precipitate)that didn't form by getting single atoms together but was always there.
Steel, being a complex material, knows all these strategies and more, as we shall see:Iron, Steel and Swords script - Page 187

How to obstruct dislocation movement withlimited forces

If you are a steel crystal, supposed not to yield too easily to outside forces, the enemy are the dislocations. They start
to move as soon as the mechanical stress pressing on your crystal reaches the yield stress, which is also a measure of
hardness. We will call that "yielding" from now on. Yielding means that plastic deformation commences.

Remember:Hardness measures essentially how
difficult it is to move dislocations

Let's consider some steel, some aluminum, or just any metal with some kind of foreign atoms or impurities inside.
Carbon in the case of steel, copper in the case of aluminum, and so on. We now want to harden the metal, making it
more difficult—but not impossible!— for the enemy dislocations to move through.
We will use those foreigners for that, either as mercenaries fighting single and on their own, or by forming strongholds
involving also some of the good citizens. In other words: by forming metal-impurity precipitates.
We have names for those hardening mechanisms:
Solid solution hardening works with single foreign atoms, i.e. extrinsic point defects.
Precipitation hardening works with precipitates that form during cooling.
Achieving maximum hardness without blocking the movement of dislocations completely (that would make the steel
brittle) means to precipitate the carbon, or whatever impurities there are, in an optimized way. Size, shape and the
distribution in the grains of the crystal should also be "just right". We have two primary tasks now.
1. Finding out what the optimal size of precipitates would be, and2. Forcing the crystal to make the right kind of precipitates.
After we did that, we need to coordinate solid solution and precipitation hardening with all the other hardening
mechanisms yet to be discussed. This is not going to be easy because you can be sure about one thing: whatever
the right size of precipitates will be for you, the crystal isn't going to like it.
It is now easy to see why. Get the relevant phase diagram for the impurity you are considering, look at the phase or
the phase mixture you will eventually have at room temperature for the composition chosen, and you will realize that
there are only three options:
1. The crystal wants its impurities dissolved.
2. The crystal wants its impurities precipitated.
3. A mix of 1 and 2.
That is true for any binary phase diagram, not just for carbon in iron.
If the "host" materials wants precipitates like Fe3C in the case of iron and carbon, or CuAl2 in the case of Aluminumand copper, it wants them to be as big as possible. I have stated that before a few times.
We know that by locking unwanted atoms into a precipitate, the crystal gains energy and gets closer to nirvana. But
why are a few big ones better than a lot of small ones?

Why should precipitates be as big
as possible for nirvana?
Iron, Steel and Swords script - Page 188

We need to look at this question now in more detail. Especially because the answer will also tell us why it is sodifficult to nucleate a new phase or precipitate.
There is no such thing as a free lunch for crystals either. Locking your unwanted impurity atoms into a precipitate does
make life better as soon as your state point hits a two-phase region, indeed. But there is a price to pay.
A precipitate is a three-dimensional defect—remember? The interface between the
precipitate and the crystal is then by necessity a phase boundary, a twodimensional defect. You may perceive the phase boundary as a kind of fence thatis necessary to keep the foreign atoms inside.
But phase boundaries are defects too, and thus not something you want. Nirvana is
without defects or at least with as few as possible.
Considering that you must have phase boundaries around your precipitates, youwant to keep their total area as small as possible because their total eneryg scales
right with their area.

ScienceModuleNucleation

In other words, you want the relation between the number of impurity atoms imprisoned in the precipitate and thethe phase boundary "fence" surrounding your "prisons" to be as large as possible. You want a small fence to lock ina lot of prisoners—and that means you want your jail precipitate as large as possible.
That's easy to see. It takes far less fence length (one dimensional thing) to keep hundred prisoners in one large-area
jail (two dimensional thing) compared to keeping 25 prisoners each in 4 smaller jails, see below. In three
dimensions there is even more to gain by making your prison big.

Ratio of size and boundary; prison example

Four small prisons need twice as much fence than one large prison with the same capacity. In three dimensions it
would be even worse.
The consequence is simple: If you, the ancient or modern smith, want lots of small precipitates, you have to fight the
crystal and the second law! It's time to review our arsenal for doing this.

Iron, Steel and Swords script - Page 189

8.1.2 A Closer Look at the Second Law
The second law tells us how things should be for the coveted state of nirvana. What the actual structure will be is adifferent kettle of fish.
Your mother, your teacher, your priest and so on told you many times what you should be; now consider what you
are. You probably are not the president, a Nobel Prize winner, or the pope (me neither). But perhaps you are ateacher, a (rich) plumber, a real estate agent, or a professor. Not so bad either. And I can still win the Nobel priceeven so it's highly unlikely.
The second law does tell a crystal what it should be—in precise equations. Your mother told you what you should
be in countless words, and your priest, imam, rabbi etc. threatened you with eternal fire and brimstone etc., if you
didn't heed their ideas about what you should be. I prefer equations by far.
The second law also relates to crystals what the second-best structure would be, the third-best, and so on. If thevery best structure is unattainable, the crystal is smart enough to go for the second best, third best and so on. Can
you match that?
Unfortunately, while the crystal always seems to know precisely what is best under given circumstances, we do notalways know it for sure, neither for the crystal nor for ourselves. The second law doesn't tell us all these alternatives
straight away but hides the answers in so-called differential equations or other tough math. We can't always find thesolutions—in contrast to the crystal.
If you have not yet achieved nirvana or a good approximation thereof, you must do something. Doing anything means tomove some atoms around.That is true for you and for a dumb crystal. The crystal usually does it by some of the
diffusion mechanisms we already discussed. If the crystal wants to form a big precipitate with, say, a million impurity
atoms inside, it must gather this number of impurity atoms from a largish volume that contains enough of the stuff, andsend them all to the place where the precipitate is to be located.
How, I ask you, can a rather dumb crystal, consisting of not-so-smart atoms, know about this and then actually do it?
There can only be one answer: the crystal "knows" nothing whatsoever. It happens all by itself, without purpose andintent!
Out of the pure chaos of impurity atoms and vacancies running about at random, order, in the form of neat
precipitates embedded in the crystal, will arise all by itself if the conditions are right.
How does that happen? Roughly like this: Two impurity atoms jumping around at random in their host crystals,
meet accidentally somewhere, and since they like each other to some extent, stick together for some time. Thenthey break up again, resume their random walk, and meet some others, or maybe meet some threesome that hasformed accidentally somewhere else.
As the temperature goes down, their movement becomes more sluggish and they tend to stick together for a longer
time. Precipitates start to form and grow as soon as more atoms stick to it per second than atoms leaving it again.
Look at your bank account. The amount of money in your account starts to grow as soon as more money comes inper month then flows out. If your account balances, you are at equilibrium: nothing changes anymore (on average).
Change the average stream of money flowing in or out ever so slightly, and your precipitate of money localized inyour account gets larger or smaller.
The second law (and some other quite exciting stuff) comes right out of "statistical thermodynamics"; that part ofphysics that describes what temperature actually is. We always deal with huge numbers of atoms and that's why we
can only deal with statistical entities like averages. Temperature, in case you forgot, is just another word for "averageenergy contained in the random movement of elementary things like atoms or molecules".
You see there are good reasons to call it statistical thermodynamics.
By the way, the first scientist who explained phenomena like diffusion in terms of atoms jumping around at random
was no less than Albert Einstein. With that he also established the reality and existence of atoms.
Later he got a Nobel Prize for explaining the so-called "photo electric effect", essentially establishing the photon .
He should have obtained at least five more Nobel prices, definitely another one for explaining (in terms of equations)the phenomena of diffusion of atoms in solids.

Iron, Steel and Swords script - Page 190

Albert Einstein
Born in Ulm / Suebia / Germany. One of the many
achievements of Suebians

Since you asked: Nobel prices should have been awarded to Albert for:
1.
2.
3.
4.
5.

Explaining the phenomena of diffusion in terms of atoms.
Explaining the photoelectric effect. (This one he got).
Special theory of relativity (worth about 5 regular Nobel prizes).
General theory of relativity (worth about 10 regular Nobel prizes).
Describing (in equations of course) the so-called "stimulated emission of photons", the very foundation of
Lasers, about 50 years before the first Laser went operative.
6. Predicting the so-called "Bose-Einstein condensation" a strange thing that matter does at very low
temperatures. The "Bose-Einstein condensation" was found experimentally not so long ago, and that did
provide for Nobel prizes.
But despite Einstein's involvement with what we now call statistical thermodynamics, the supreme price for that, in myopinion, goes to Ludwig Boltzmann (1844 - 1906) and Josiah Willard Gibbs (1839 - 1903), who put the second law
as we use it here on firm footing just about before the turn of the 19th century.
The (very short) equation on Boltzmann's tombstone (S = klog w) ranks up there with the very well-known shortequation from Newton (F = ma), Einstein (E = mc2) or Max Planck (E = hν). I promised that I would abstain fromequations here, what you see above are just quotes.
Boltzmann not only did not receive the Nobel prize; he finally was driven to suicide by some of his dear colleagues
who ridiculed him for proposing that things like atoms did actually exist. "Can you see them" he was asked, "if not,shut up". He couldn't see atoms then—but we can see atoms now. Grave injustice has been done to a hero ofphysics and materials science once more!
The long and short is that neither crystals nor atoms are smart. They just do at random what circumstances permit
them to do, just like some American presidents.
Boltzmann and others were smart. They could predict what the nirvana states (best, second best, …) would be andhow it can be achieved by atoms running around. Let's be smart, too and see what we can do.

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8.2 Outwitting the Second Law

8.2.1 Strategies for Winning
States and Microstructure
Now let's outwit the second law. We need to do this because we definitely don't want to have the microstructure thatthe crystal wants to make. In its unwavering adherence to the second law it is going for the best nirvana state , and we
don't like that. Before we go on, let's define two terms a bit more precisely:

1. What, exactly, is a nirvana state for binary compositions like iron and carbon?
The first answer is simple: It is the state you find in the phase diagram for a given composition and temperature. So
far I have used the expressions "nirvana " and "nirvana state" more or less indiscriminately; they meant essentiallythe same thing. But meanwhile you have learned a thing or two and it is time to be a bit more discerning. We now
use the term "nirvana state" to indicate that the crystal has assumed the proper basic structure necessary fornirvana, indeed, but not necessarily nirvana itself.
It is easy to illustrate the difference between nirvana and a nirvana state . For example, if you want to achieve(temporarily) nirvana, your nirvana state means that all the things required for nirvana are at hand, e.g. leisure, beer,
red wine, good book, attractive and willing person of the right sex, and so on. Having all that, i.e. being in a nirvana
state , is a necessary prerequisite for achieving nirvana but does not yet constitute nirvana. How far you getnirvanawise depends on how all those ingredients interact with each other and with you. In other words: the details(called microstructure) of the nirvana state also matters quite a bit.
So a crystal must first be in a nirvana state if nirvana is to be achieved later. It then can be close or not so close tonirvana proper, depending on what the microstructure of the nirvana state looks like.
Let's look at some basic possibilities for crystals:
The nirvana state of a binary composition like iron and carbon consists of either one phase or a mixture oftwo phases, never more. The phase diagram shows you which one of the two it will be for any given state
point. The nirvana state of iron with 1,3 wt% carbon at 1100 K, for example, is γ + Fe3C or in words:
austenite plus cementite. Look it up yourself.
If the nirvana state consists of just one phase, nirvana proper calls for a single crystal without any defects
except the required point defects; essentially vacancies and the dissolved atoms of .the second constituent(e.g. the carbon in iron). For example, a ferrite polycrystal full of dislocations is in a nirvana state but has not
yet achieved nirvana.
If the nirvana state consists of two phases, nirvana proper calls for two single crystals with the phaseboundary area as small as possible.
We know already that achieving nirvana proper is an elusive goal for most materials. Achieving the nirvana state,
however, is possible, and that must always be the first step on the way to nirvana.

2. What, exactly, is a microstructure or simply structure ?
Easy. It's nothing but the exact arrangement of the atoms described in terms of defects. Describing a
microstructure thus may entail entries like:
Average grain size and grain shape (round or elongated?)Nature, size and distribution of precipitates.
Density and distribution of dislocations.
Kind, concentration and distribution of dissolved point defects (uniformly distributed or enriched around grainboundaries?)
Presence of metastable phases (e.g. martensite).
Presence of nanocracks, inclusions of something else (slag in steel).
...
The list is long and in practice not so easy to compile. Generally speaking, the longer and more detailed it is, thelarger is the deviation from the (always simple) nirvana structure.
Now comes an important point: We can express the difference or "distance" of the actual microstructure from thenirvana microstructure in numbers (with unit energy). The larger the distance, the larger the need or drive for the crystal
to do something about it. That's why we call this distance: driving force! We need to write that down in big letters:

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The driving force for change is thedifference in energy
between two alternatives
You are right. It should actually be called driving energy but for historical reasons it's called driving force. Knowing
the driving force of a crystal will give us a good idea about what the crystal is going to do if we don't interfere. It's likeknowing how your opponent is going to employ his troops in the upcoming battle. That will certainly help you to win
the fight.
Strategies and Tools
For our sword blades we want certain microstructures. There is no such thing as "one microstructure fits all". What kindof microstructure is best for you blade depends very much on what kind of steel you start with, and what kind of (carbon
steel) blade you want to make. Let's look at three examples:
Modern blade from uniform steel. You want small grains and very small precipitates in medium carbon steel; nottoo many dislocations. That ensures that your steel is quite hard but still ductile enough not to fracturecompletely or to suffer heavy damage at the edge on impact.
Wootz steel blade with "water" pattern. You need to start with high-carbon "hypereutectoid" steel that must havebeen molten once (no slag residues, no microcracks, etc.). You need to control nucleation of the cementite andyou need to form very large precipitates arranged in some pattern. Possible but not easy.
Japanese katana. You need at least two different kinds of steel, both as uniform as possible. The softer one
could contain coarse grains and precipitates, and the harder one must be able to develop martensite (I'll get tothat).
Pattern welded blade. You need at least two kinds of steel, three are even better. Two must "look" differently afteretching so a pattern can develop, their microstructure actually doesn't matter all that much. Two different kinds ofcarbon concentrations will not be good enough; different phosphorous concentrations (I'll get to that) might do thetrick. The microstructure of the third kind (used for the edge) should be like that of the modern blade from aboveor the hard steel of the katana
Lots of different microstructures; none of them close to the nirvana structure. We now need to discuss strategies formaking the desired microstructures. Before we look at this, however, I'm going to make an important statement :There is no such thing as plain
carbon steel!
Only with very modern technology can we make something that comes close to an ideal binary composition made fromonly two kinds of atoms like iron with a defined amount of carbon and nothing else. The problem is that making such a"perfect" carbon steel (or any other binary composition) is always very expensive and mostly pointless. So it's ratherrare.
In order to make an ideal carbon steel you would have to start with extremely pure iron. Next you alloy it withsome defined amount of ultrapure carbon—but what for? You would get "ideal" carbon steel with some specificproperties indeed—but are those the properties you want? If you can make ideal binary carbon steel, you can dothat with most of the other 90 elements of the periodic table, too. Chances are that some other combination will giveyou better steel than what you can get with carbon. There is no reason whatsoever that from 70 or so possible alloy
elements, carbon should happen to be the best.
We can only justify taking this ultra-expensive route for special applications where we need specific properties that
we cannot get in cheaper ways. Even then we compromise. We don't start from ultrapure iron, just from relatively
pure iron. We may not want carbon in there but tolerate a little bit. Then we add small amounts of other elements toachieve the properties we want. That is not only done, it is a growing part of modern steel making. The catchwords
are High Purity Steel and High-Strength Low-Alloy Steel or HSLA steel.
Making large quantities of cheap steel thus forces us to work with non-ideal carbon steel that also contains relevant
quantities of other elements. In fact, many of today's steel do not rely on carbon as the main alloying element at all.
You the ancient smith, however, had no choice. You had to work with what you could make or get.
This is a very important point. We are now moving, ever so slowly, from being Materials Scientists to being Material
Engineers . We must work with what he have or can afford.

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The difference between Materials Scientists and Material Engineers
is: Money
Money matters to Material Engineers. Not only does a Material Engineer project leader make far more money thana Materials Scientist professor, the former must be aware of the costs of what he is doing, on return on investment,
impact on the environment, and so on. He cannot focus on making ideal steel, he typically must make cheap
steel—in bulk!
So real steel always contains other impurities besides carbon, some added intentionally, some unintentionally. Aslong as there is not a lot of this stuff around, the iron - carbon phase diagram still is (approximately) valid withrespect to the nirvana states one should expect.
It is the microstructure that is sensitive to small amounts of impurities. This is good because it is mostly the
microstructure we want to optimize for our purpose since there is not much we can do about the nirvana state (I'll
get to the important exception shortly). Impurities thus are an important part of our arsenal for fighting the crystals
tendency to be a softie.
By the way, did you note that I'm not saying that Materials Engineers never make expensive and almost ideal materials,
They do—whenever money can be made and there is no alternative.
If we look at silicon (Si) instead of iron, we need to make ideal (and expensive) silicon since some products wemake from silicon only work if we use extremely perfect silicon. That means we need single-crystalline silicon with(almost) no defects in the crystal, except for some painstakingly selected foreign atoms that we need in well-defined
small concentrations. Silicon crystals are far more perfect than the best we could ever do with iron, and about as
close to nirvana as a crystal can ever get.
Yes—it's expensive. Very expensive. Luckily, the products we make from this expensive perfect silicon are verysmall: microelectronic components like micro processors or the memory in an USB stick. So we get a lot of
products and thus cash out of very little silicon.
Making a microprocessor out of a slice of perfect single-crystalline silicon requires
to make changes to the silicon, This, as always, requires to move atoms around.
How is it done?
Well, employ the strategies listed below (plus a few special tricks). I'm talking
basic Materials Engineering here when I now talk about strategies for optimizing
microstructure, not just sword blade making.
Times are a'changing. Right now we need "perfect" but inexpensive silicon inbulk—for making huge amounts of solar cells. A real challenge for Materials
Science and Engineering. As you will see (on roof tops), we are up to the job!

Science
Link
Semicond.
Technology

But back to the topic: strategies for making the desired microstructures. Here are the basic strategies and tools wehave at our disposal. In simple cases one strategy may suffice but in most cases you must use combinations.
Strategies :1. Stop at the right moment whatever the crystal is doing at high temperatures. For doing that you cool itquickly; a process called "quenching". There might be two effects:- The crystal retains more or less the microstructure it had at the high temperature.
- The crystal switches to a "desperation" microstructure that does not need much atom movement to comeinto being, just large driving forces.
2. Use violence. Change the structure by massive deformation induced from the outside.
3. Force the crystal to take a special way towards nirvana by temperature profiling. Change the temperature
in some specific way, allowing only those things to happen that should happen.
4. Optimize the composition. Make sure you have the right proportions of the main ingredients and the properseasoning with impurities.
Tools :
1. Cold liquid. Throw your hot steel in it and you have quenching.
2. A hammer or any kind of press, rollers, ..., for inducing plastic deformation.
3. A controlled heat source for tempering. Your hearth, an oven or crucible, a powerful Laser, a torch, friction whatever works.
4. ???? You need to add or remove this and that and there is no particular tool describable in just a few catchwords.
I will go through all of that in more detail in what follows. Here we just note that strategy number 4 is actually very
powerful but the tools that go with it are a bit vague. In particular for you, the ancient smith. While nowadays we canquantify and understand the "this and that" bit, you, the ancient smith, could not. The only tool you had at your disposal
was the ability to pick the "right" kind of iron or steel from a rather limited supply. The material you started with had thensome composition that you could not change all that much any more. The only exception is what is known as"carburizing" or "de-carburizing" at high temperatures, increasing / decrasing, or more generally, changing theIron, Steel and Swords script - Page 194

carbon concentration somewhat in surface-near regions.
In essence: it is not so much the smith but the people who made his steel who employed strategy No. 4 - knowingly or
unknowingly. It is a major strategy and I will come back to it later to some extent when I go into the making of steel.
Now let's look at strategies No. 1 and 2 in a more superficial way before I go into more details. Strategy No. 3 will
exercise us a lot in what follows, so I will not say anything to that right here.
First Strategy: Quenching
After the crystal assumed the proper nirvana state at high temperatures, it will start to work on the microstructure.
Precipitates will grow (in a two phase state) until there is only one (or a few) large one, or shrink (in a one phase state)
until there is none; grains will grow, getting larger and fewer; dislocation will gradually disappear, and so on.
The quenching strategy exploits the fact that some intermediate structure that the crystal assumes on its way to thenirvana structure may suit our needs better than an ealier or later structure. It's like preferring teenagers to children or
adults for some purpose that I have yet to find out.
For stopping whatever the crystal is doing at some particular temperature and point in time, we simply make use of
the fact that not much can happen anymore if atoms can't move. All it takes to keep atoms from moving are lowtemperatures. Just look at the numbers again to appreciate this.
For steel and most other common metals, room temperature is often (but not always) cold enough for preventing
atoms to do something.
At room temperature a carbon interstitial (or other interstitials like nitrogen (N) atoms) makes roughly one jump per
second. Within a whole year they can move about one micrometer at best. That's not a lot but enough to causesome trouble on occasion, as we will see.
The movement of all other atoms - either by vacancy or by interstitial diffusion - is so sluggish at room temperaturethat they're not doing much anymore during your lifetime. The iron atoms thus do not move noticeably during one
year at room temperature. However, if many years have passed; for example thousand or two thousand years,
things may not be so clear anymore.
Very old glass, an amorphous solid (the opposite of crystalline order on the atomic level, and not the nirvana state)
may have crystallized (nirvana state) just a bit after 2000 years or so because its atoms are moving ever so slowly.
We notice that because the glass turns "milky".
The structure of very old steels may have changed a bit, too. It's not so easy to tell because we don't know what the
microstructure was 2000 years ago, and we have hardly any specimens to investigate, anyway.
So what you can do as a first option is to "freeze in" some desirable microstructure that might exist at hightemperatures by cooling down real fast - for example by dropping your hot steel in cold water. That process is called"quenching". You can control the cooling rate somewhat by quenching into water (fast), oil (not so fast) or brine(slow), and of course by the temperature of your quenching liquid.
What strategy No 1 obviously needs is a certain control of the cooling rate. How many degrees does your sword
blade cool down per second? Cooling rates are thus measured in degrees per second, for example in oC/s; thesame as K/sQuenching your work piece is not as easy as it appears. First of all, you just can't cool down a solid piece of steel (oranything else) arbitrarily fast. The best you could do (if money is no concern) is dropping your hot steel blade into liquid
helium at 4 K (- 269 oC, -452 oF). Even better would be to let somebody else drop it because what you get is a very coldsword blade and a major explosion when all that liquid helium turns instantaneously into gas.

Quenching a steel bar at one end
The bottom sits in (originally) cold water. While is coldenough to appear black, most of the rest is still red
hot.
Source: Alexander Kilpert; Internet; with friendly permission.

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No matter how you quench, the part in touch with the coolant will always cool down far more rapidly than the rest;
see above. Same thing for the inside in comparison to the outside.
The earth has been put into a really cold place some billion years ago but is still rather hot inside. You can try alittle experiment with a hot potato if you have doubts about that. Take it out of the boiling water, hold it under running
cold water for a few second until the outside feels right for eating, and then bite into it. You will suddenly andpainfully understand what I mean.
In other words: it is impossible to cool down a big piece of steel with the same cooling rate everywhere. During
quenching the outside will always be colder than the inside, until all parts eventually have reached ambient
temperature. What you will get during quenching without fail is therefore a temperature gradient inside your steel,a change of temperature with position.
That's not so good for what we have in mind. We want to freeze-in a certain microstructure and that will only work as
desired for the outer parts of a work piece that can cool down real fast. In the inner parts it is hot much longer, andwe must expect the microstructure deep in the steel to be different from that on the outside.
Too bad - and not much you can do. But the unavoidable different cooling rates (in scientese we call it differential
cooling rates) in different parts of your blade can also be useful, as you might know if you know anything about theJapanese art of making sword blades. I'll get to that.
To make things worse, quenching also has a few side effects that may turn it into a dangerous medicine. You might
get the desired microstructure allright—but in a blade that has shattered into several pieces or bend into a distorted
shape. The reason for that is that quenching always induces massive mechanical stress, directly tied to thetemperature gradient. I will get to that, too, in due time.
Moreover, If you really rush the crystal by cooling it very quickly, it might not be able to produce the nirvana state,
never mind the microstructure. It then changes its strategy for achieving nirvana, which was: i) assume the nirvana
state, ii) optimize the microstructure. Instead it might do crazy and unexpected things like forming martensite. I'll
get to that later.
Despite all the problems listed above (three times "I will get to that later"!), quenching is a major way to process steel.
But the unavoidable differential cooling rates do put limits to this strategy, and as you just learned, it isn't quite as easy
as it appears on first sight.
In other words: you can cool quickly but the iron crystal will fight back. How it does that we will see in what follows.

Second Strategy: Hit It Hard!
The second strategy is the simple and time-honored strategy most men use whenever they are supposed to dosomething but are out of their depth: Resort to violence!

Sword, plowshare, whatever: beat it hard!
"Let Us Beat Swords into Plowshares"; Sculpture by
Evgeniy Vuchetich in front of the UN building in NYC;
The other way around is here.
Source: Internet at large

Iron, Steel and Swords script - Page 196

Destroy the structure that your crystal assumed at some temperature and some point in time by banging it hardwith a hammer.
Or run it through a rolling mill, a press - anything that induces massive plastic deformation and perhaps some microcracking.
If you hit your sword blade-to-be hard with a hammer, something must happen inside the crystal. At the very minimum
you induce plastic deformation, generating a lot of dislocations and running them through the crystal.
Look at how its done again: a dislocation moving through a crystal produces a shape change and thus plastic
deformation. Already a little bit of violence produces a lot of dislocations!
Besides plastically deforming your work piece, you also may fracture the brittle cementite inside by banging on yoursteel - here is the picture showing that.
The havoc wrought by banging your steel with a hammer at temperatures not too high should influence the final
structure at room temperature. It does - and we will have to look at that a bit more shortly.
But don't forget: If you bang your steel above the transformation temperature for forming austenite or one of themixed phases with austenite (around 1000 K (727 oC; 1341 oF), or if you heat it after banging beyond thattemperature, the structure produced by banging will get lost during cooling, provided there is enough time. Above atransition temperature, the steel looses it's "memory" of what was done to it before, to put it in simple words, andmoves determinedly and quickly to the new nirvana state, forgetting all that has happened before.

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8.2.2 Tempering and Ostwald Ripening
Third Strategy: Tempering
The third strategy was: Force the crystal to take a special way towards nirvana by temperature profiling. That's what
we will do a lot; often in conjunction with the other strategies.
Let's look at an example:
1. Quench your steel with some suitable parameters (starting temperature, type of quenching fluid, volume ofquenching fluid, temperature of quenching fluid, how long you keep it in the quenching fluid, ...). That's using
the first strategy.
2. Heat it up again to a typically low to medium temperature and hold it there for a while. Parameters are:Temperature, time, cooling down procedure (slow or fast)).
Both points together mean you provided a temperature profile and that means you used the third strategy.
Heating up again after some initial cooling is known as "tempering" your steel. We will look at some examples oftempering shortly, so I won't dwell on it here.
In other words, we subject our steel to a defined temperature vs. time treatment. The example above produces what was
known as "tempered steel" in the 19th century and beyond, the best possible steel for demanding implements likeswords or umbrelly spines.
The temperature - time profile in this case might look like this:Temperature - time profile for "tempered" steel
Very schemantically; numbers are not too
meaningful.

Temperature-time profiles can get quite involved. Sword blades from wootz steel, for example, may have been subjected
to many intentionally performed hot-cold cycles.
Now why should one want to do this? Because it allows to engineer the density and size of cementite precipitates,
among other things. And that is relevant for you, the ancient smith.
Let's consider a simple but important example. You, the ancient smith, want to make a wootz blade with a "water"
pattern. By definition this is done with hypereutectoid or high-carbon steel. The final steel crystal, as you know now,
thus needs to precipitate a lot of carbon as cementite. If you don't use tricks, the primary cementite will encase theferrite grains as shown before, resulting in useless brittle steel.
You definitely need to prevent this. Moreover, you also need to induce the crystal into making large precipitates incertain places, so your blade will show the elusive "water" pattern when its finished (I'll get to this in due time).
The crystal, as you know (the reader, not the ancient smith), also wants to make large precipitates in the pearlite cementite two-phase region that we have at room temperature. It just does not succeed most of the time because
the primary cementite nucleates and grows along the grain boundaries, while the secondary cementite produced
pearlite or, worse, makes those brittle walls even thicker.
So the first thing you need to do is to prevent cementite nucleation at grain boundaries at all costs. You do that by
employing strategy No. 1. You select not just any high carbon hypereutectic steel but suitable wootz steel that
does not only contain some other impurities at the right concentrations but also in a special spatial distribution. You
either picked a very special steel or you got a brittle and useless blade. We can be rather sure that a lot of bad
blades have been made, indeed—we just never read about those nor did they survive.
I'll come back to that. For now let's just consider how one would go about making just a few and large cementite
precipitates. There are two basic or "theoretical" options for doing this:
1. Nucleate just a few precipitates, far removed from each other. Then let them grow until all the carbon is used
Iron, Steel and Swords script - Page 198

1.
up. This way you will only have have a few big ones in the end.
The question, of course, is: "how?"
2. Nucleate lots of small precipitates and subject them to a kind of "grow big, winners take all" race. The
losers, falling behind in growing, will be forced to stop growing altogether and must shrink instead, releasing
their carbon atoms and feeding the more successful ones with it.
The question, of course, is: "how?"
The first extreme is simply not feasible in crystal with defects, and thus certainly does not apply to all normal iron andsteel crystals. Defects act as nucleation centers and if you have a lot of defects you will nucleate a lot of precipitates.
That is especially true if you start with proper wootz steel that contains additional impurity atoms to induce nucleation of
cementite everywhere and not at the grain boundaries. Sorry. You will alway nucleate lots of small precipitates at hightemperatures.
It's just like the early American settlers. The were roaming the crystal the prairie as individuals or as twosomes, andnucleation of a settlement was easy. Plenty of good sites. Right at the edge of the forest, next to the little brook, inthat protected shallow, or at the lake shore. Eventually, more people precipitated around some logwood cabin
nuclei, forming small towns. No power in the world could have induced individual settlers in the USA to start withjust a few sky scrapers in just two or three major places.
Sorry. Just forget option No. 1; it won't work. Except if you start with ultrapure iron where no nucleation places areavailable (put your settlers in a featureless and waterless desert). Then induce some defects for nucleation (dig awell and create an oasis). That will make sure that all your perambulating carbon atoms (settlers) will be found there
and nowhere else after a while.
That's obviously just as impractical for making cheap steel in bulk as the making of ideal carbon steel discussed
before.
Nevertheless we employ that strategy on occasion—for silicon products, of course.
But you, the ancient smith, couldn't even dream of doing it that way. You had no idea anyway what was going on inyour steel. The same is true for your superiors up to and including your Gods. In the many revelations comingstraight from some deity and recorded in some holy book, no practical advice for hard-working smiths or artisans
was ever given.
You, the ancient smith, thus had to go with the second option.
Tempering and Ostwald Ripening
The second option might look at bit crazy at first. Why should some disadvantaged precipitate that couldn't grow fastenough for whatever reason, give up and start shrinking at some point, releasing its carbon atoms so that the big andimportant ones can get even bigger? It goes against our my and hopefully your basic feeling of taking from the rich andgiving to the poor.
Well, the principle behind the second option was first written down by what we must assume was a closet materials
scientist: Matthew the apostle He teaches: "For to all those who have, more will be given, and they will have anabundance; but from those who have nothing, even what they have will be taken away" (Matthew 25:29).
Mathew's principle is not just for the religious, it governs much of everyday life:
Have you ever considered what there was before high-rise buildings covered large parts of Manhattan? Just
look at Chinese cities today and you see how many small houses disappear and feed huge sky scrapers.
Not exactly with the bricks they were made from but with their former share of the land, the electricity, thewater, emissions, and so on.
Have you ever been inside a major European cathedral? Odds are that it was built on the side of a big churchthat was erected on some old basilica, which has been build over an ancient chapel; cannibalizing each timethe material from the older construction and other abandoned smaller buildings in the surroundings.
Maybe more to the point: have you looked at the distribution of wealth in the USA lately? A few bankaccounts have grown to humongeous size while most others shrank. Many are close to or below zero now.
Ripe Swiss cheese contains only a few big holes. Young Swiss cheese contains many small ones. Guesswhat happens during ripening or ageing?
Matthew's principle is important in Material Science and Engineering. We scientists know it under a different name,however:

In science, Matthew's principle is called
Ostwald ripening

Iron, Steel and Swords script - Page 199

Ostwald ripening is a very common process inside materials, and we will soon see
how it works for making wootz sword blades. If we exclude cathedral building, bankaccounts, cities or other stuff that is outside of Material Science proper (Swisscheese is inside), Ostwald ripening is a process that we understand very well; we
can actually calculate what is going to happen.
I will not go into the mechanisms behind Ostwald ripening here. You can get a firsttaste form the science module, where the first part is not too difficult to grasp.
The long and short is that Ostwald ripening always happens in crystals. Exactly
how depends on the circumstances, in particular the temperature - time
profile—and that we can control to some extent. We will need to keep Ostwald
ripening in mind when we now look at real steel.

Science
Link
Ostwald
Ripening

Tempering and Nucleation
So far I gave you the impression that there is not much we can do about nucleation. Is that really true? Well, mostly but
not quite. Crystals want to make a few big precipitates if the phase diagram calls for it, and for doing that they have twobasic options outlined above.
Now crystals don't know a thing about the two options they have in principle, they're just doin' what comes naturally.
Their IQ rarely exceeds that of the people addressed in Annie's well-known song, which one could amend by the lines:

You don't have to know how to precipitate
When you're plagued with too much carbon.
You just let'em loose and they'll start to mate
Doin' what comes naturally

Crystals are dumb in any
shape
They ain't had any learning.
Still they're happy like an ape
Doin' what comes naturally.

The crystal starts making the first tiny precipitates at places where their nucleation
is particularly easy (principle of supreme laziness) if you give it time. That is almost
never somewhere inside the perfect crystal lattice but almost always at major big
defects. When you are out in the street and in need of precipitating something outof your body, you look for a suitable place like the bathroom of Hotel to dumb the
stuff - provided you have time. You also take your time and do whatever you do atleisure.
Grain boundaries, especially the juncture of two grain boundaries, are thecorresponding great nucleation sites for the crystal, where it can dumb the surplus
atom it doesn't want to have in its body bulk anymore, in style - if there is time. The
precipitates grow leisurely.

Link Hub
Nucleation

When needs get more pressing, meaning the driving force get larger, you settle for any bathroom, including thosearomatic small cubicles distributed everywhere. Dislocations, or some small precipitates of some other kindcorrespond to that as far as the crystal needs are concerned. You do not loiter and precipitates grow quickly.
If the driving forces become overwhelming and the alternative to immediate precipitation is utter disaster, you settle
for a dark corner or just about any place (just one foreign atom or even the perfect lattice). And you do it as quickly
as possible.
So there is nothing much you can do about nucleation. You are stuck with the infrastructure or defect structure that's
there. The key word is rather "driving force". Provide large driving forces and nucleation will happen in far more places
then in the case of small driving forces. The result are many small precipitates that came into being rather quickly.
Like always, there is a catch. You get a large driving force if you cool down quickly to some temperature well below
some transformation temperature, e.g. our by now well-known 700 oC (1292 oF) for carbon steel. There is an urgent
need now to have cementite precipitates but since you cooled down quickly, there was not enough time to makethem. Nucleation will start all over but growth is sluggish since nothing moves very fast anymore at thattemperature.
Yes? You think, maybe, let's raise the temperature again, after we now have all these nuclei, so the precipitates
can grow faster? Very good. That's a straight A for paying attention. The headline, after all, is temperature profiling.
What it all amounts to is the "golden rule"

Control nucleation!
Control kinetics!
Iron, Steel and Swords script - Page 200

We are now at the core of Materials Technology, in particular iron and steel technology. Controlling nucleation means tocontrol the starting configuration for the march to nirvana and the beginning of cooling. Controlling kinetics means
temperature profiling.
With the starting configuration you can control nucleation in many ways; I'll get to that. You could, for example,
work with defects. As mentioned before, it is often quite efficient to introduce intentionally a few suitable foreign
atoms besides our omnipresent carbon.
Of course, you move now from a binary system—just iron and carbon—to a far more complex system and only God
knows Materials Scientists know, what else besides helping the nucleation of e.g. cementite, those foreign atoms
will do with iron and steel. God probably knows too, but hasn't revealed it directly so far. Interestingly enough, asmentioned before, all those revelations in all those holy books never contained any hard scientific facts.
The foreign atoms that you did not introduce intentionally but happen to be there without you knowing, might be justas efficient for nucleating cementite. And you may not need a lot to change the behavior of your steel.
Concentrations far below 1 % might be sufficient.
Wootz steel, for example, needs either a little vanadium (V), niobium (Nb), titanium (Ti), or possibly a few other"carbide formers" for being what it is, if Verhoeven is right (I do believe he is, up to a point).
Alternatively or additionally you can influence nucleation by controlling the "driving force" that pushes the crystal
towards nirvana, as outlined above.
We will now turn towards real steel more and more, and all the points made here and before will come into their own.
Before we do that, however, we will see how nucleation and Ostwald ripening works at something far simpler than steel
but of prime importance for sword bearers: the making of optimized aluminum beer cans.

Iron, Steel and Swords script - Page 201

8.2.3 It's a Long way to Nirvana
The Aluminum - Copper Experiment
Let's look at a classical example that uses our strategies in a particularly transparent way. Thanks go to Michael
Ashby, David Jones and their grad students who most likely did the actual work.
The idea was to harden Aluminum (Al) by adding a small amount of copper (Cu). This is important for making
superior beer cans (and the cans for less interesting beverages). You don't want to entrust your beer to any can,you want a can with properties that are "just right". Here is a short list:
1. High mechanical strength when filled with beer. You must be able to stack a lot of cans on top of each other;rough handling must not lead to leakage.
2. Low mechanical strength when empty. Empty cans should be easy to crush with one hand or with little effort,
to reduce the volume for transport and easy re-melting.
3. Extremely low costs. That means the can is made from a minimum of aluminum alloy that is easy to shape.
4. 100 % recyclability. No weird things must happen upon remelting and solidification, even if the material is a
bit dirty.
5. No bad influence on the beer inside. A totally passive or chemically inert surface is necessary
That calls for an aluminum alloy with precisely tailored properties, in particular hardness. Actually, it calls for two
aluminum alloys with different hardness: one for the bulk of the can, and a somewhat harder (and thicker) one forthe top with the pick-open device.
One of many possible ways to go is to use copper (Cu) as an alloying element. It must do the job already in small
quantities since copper is expensive. In the "Ashby and Jones" an extensive systematic study is reported about what
you can do with copper in aluminum. It serves as a paradigm, a model case for hardening metals by the mechanisms ofsolid solution hardening,and precipitation hardening.
I will guide you through this study because what is happening in the Al-Cu system is typical for most alloys—but far
easier to understand than what happens in the Fe-C-some dirt system. Note that what follows is not the way thematerials for real beer cans are made, it just provides basic and systematic knowledge for that venture.
First we alloy very pure aluminum (Al) with about 4 % of copper (Cu) and hold it at around 550 oC (932 oF) for a while. In
other words: we make a rather ideal and expensive binary system.
Nothing helps, you now need to look a the aluminum (Al) - copper (Cu) phase diagram. Use the link.
Yes, it is horribly complex; a real nightmare. But if we just look at the aluminum-rich part, it is actually simple. Heregoes:

Aluminum - Copper phase diagram on the Al
rich side

In the Al-rich part, with just 4 % copper (Cu), at 550 oC (932 oF) we just have Cu dissolved in aluminum or the usual
α-phase. That means that single Cu atoms are occupying the sites of Al atoms in its fcc lattice. The copper atoms
thus are extrinsic impurity atoms of the substitutional kind. You just as well could call then doping atoms because
they are intentionally introduced, but nobody does that. This term is more or less reserved for changing electricalproperties by introducing impurities. We do call them "alloying element", though.
Our starting material at 550 oC thus is poly-crystalline aluminum with 4 % of copper (Cu) atoms fully dissolved,
some dislocations and vacancies, and not much else.
At lower temperatures the crystal obviously needs to produce a few large CuAl2 precipitates for achieving nirvana.
The chemical compound CuAl2 is also called the theta (Θ) phase

Iron, Steel and Swords script - Page 202

Next you quench to room temperature. You do that so fast that no precipitation occurs during the cooling. In thelaboratory we can do that, effectively "freezing in" the high temperature structure.
Then you temper by going up to a constant 150 oC (302 oF), i.e. you employ strategy No. 1.
When you start at the 150 oC, you now have exactly what you had at 550 oC: 4% copper atomically dissolved in analuminium polycrystal. The only difference is that at 150 oC the crystal is unhappy about that. Very unhappy. It will
now do whatever it can to remedy the situation and to establish the proper nirvana state, which is almost copper-freealuminum plus CuAl 2 precipitates. You also can call it a mixture of the α and Θ phase; same thing.
So all you do next is to let your specimen sit at the chosen temperature for a while (employing strategy No. 3). You
picked 150 oC because at room temperature your aluminum cannot do much during your life time; everything is prettymuch immobilized. If you temper at 150 oC, there is enough thermal energy to allow precipitation to happen, just rather
s-l-o-w-l-y because the Cu atoms move rather sluggishly at that temperature.
That is good because it gives us enough time to observe at our leisure what is going on.
The important point is that the driving force for precipitation is large at this low temperature because the crystal can gain
a lot of energy by getting rid of surplus copper atoms.
A temperature of 150 oC combines an overwhelming need for making precipitates with some sluggishness in doing
things. We're thus heeding the "golden rule" from before and control nucleation and kinetics. The crystal has no
choice but to start a lot of very small precipitates all over the place.
If there is a sufficient number of defects around, nucleation will now start at those defects, i.e. we haveheterogeneous nucleation. Otherwise nucleation will be homogeneous but the details don't matter for our purpose
here. We just will produce a large number of nuclei soon after we reached the final 150 oC, and we do not need tocare exactly how that happens and exactly how large that number will be.
Before I go on let's reconsider the concept of the driving force; it is really important (you might want to go to thebathroom now if you remember the preceding chapter).
The driving force for things to happen is just a measure of how much the crystal has to gain (in terms of energy)
by doing something that gets it closer to nirvana.
Consider steel just a few centigrade below the austenite-pearlite transition temperature. Yes, turning into pearlite
would be better than remaining austenite, but just a little bit. You, the crystal, will go for it but not with real zest andvigor. The driving force for the transition is small. It may happen rather quickly anyway because everything is very
mobile.
Now consider that you quenched the steel very quickly to several 100 centigrades below the transition temperature.
The crystal wants the same structure as in the case above but turning to pearlite at this temperature would be far
better than being austenite, and transformation becomes supremely important. The driving force for the transition islarge.
The ominous "driving force" invoked a few times already thus simply measures the reduction of the distance tonirvana (the gain in energy in science speak) that the crystal can realize under the circumstances. Needless to say,we can calculate that and express it in a cold hard number.
The message is clear:

Large driving forces induce
desperate measures

Crystals are like humans in this respect, with the exception that they are always reasonable. Humans, just likecrystals, are less inclined to do the right thing under circumstances where the benefit is small. For example,
stopping overspending and being thrifty becomes a far more urgent business when your debtors are closing in withswords drawn.
As I'm writing this (July 31st 2011) bankruptcy for the USA is just two days away and politicians become frantic.
Greece, very close to bankruptcy for about a year by now, is extremely agitated and induces desperate measures:
frequent meetings of European heads of states, transfer of more than hundred billons of Euros (> 10 10 €) that do notreally exist, and severe violations of about every European treaty.
Two years ago, the situation was not all that different but the political driving forces were much smaller because therating agencies had not yet drawn their swords. However, in contrast to the forces driving crystals, we cannot
calculate political driving forces precisely, because large amounts of irrationality and stupidity are involved that do
not surrender to (mathematical) reason.
Like always, there is a catch to producing a high density of small precipitates via large driving forces, meaning large
degrees of sudden undercooling by quenching. While this will produce the nuclei for many very small precipitates, at
low temperatures things move slowly. Those nuclei will take forever to grow to the size you want. Growth means that Cu
atoms move by diffusion from the depth of the Al crystal to the nuclei.. If they diffuse slowly, growth will be sluggish.

Iron, Steel and Swords script - Page 203

What can you do about this? Well, here we don't want to do anything about it because we like whatever happens tohappen slowly. If we would want many nuclei but not-so-sluggish growth, we employ some smarter temperature
profiling: Quench to a low temperature that produces a large driving force and thus produces a lot of nuclei. Afterenough time has elapsed to form many tiny nuclei, you go up to a specified higher temperature. Growth now is brisk
but some of the smaller precipitates will dissolve and some others may get too large because Ostwald ripening
cannot be avoided.
If needs be, repeat the process, perhaps with some in-between steps.
That's exactly what we do with silicon if we want to grow many silicon dioxide precipitates, which we may like tohave in certain parts of the crystal.
Does this sound a bit like working with wootz steel? Yes, indeed - all reports agree that the smith was employing many
temperature cycles.
Except, he did it in order to obtain just a few large precipitates, the exact opposite of what I described just above.
He needs to do this so he can produce the famous "water" structure in this high-carbon or hypereutectoid steel.
We'll come to that later in more detail.
Here you just can take it as hint that the golden rule is rather powerful, indeed, provided you know what you aredoing. If you don't know what you are doing, you need to have a recipe, based on centuries of experience and untold
failures, that works at least occasionally. "Untold failures" means exactly that: we have never heard, read or found
the results of forging attempts that failed to produce a superior wootz blade!
Back to our Aluminum-copper alloy. After tempering for some specified time at 150 oC (302 oF), you stop whatever isgoing on by now quenching to room temperature (strategy 1), where not much happens anymore. Then you test yourtempered Al(4%Cu) alloy for tensile strength or hardness. That gives you just one data point for the curve in the figure
below. Next you analyze your specimen by everything you have (metallography, electron microscopy, ...) to ascertain
exactly what kind of structure was produced.
Then you repeat the experiment with a new sample, waiting a little longer at 150 oC (302 oF) before you do thetensile test and the structure analysis.
Then you repeat the experiment....
Then you …
When you're done, you get the curve shown below.

Hardening a Aluminum - Copper alloy

Then you repeat the whole set of experiments but with specimen where only 3 % Cu was used for alloying.
This gives another curve for this particular composition.
Then you repeat the whole set of experiments with 5 % Cu, and so on.
When you're done, you repeat everything once more but now you hold the samples at 170 oC, or 140 oC.
And so on at (almost) infinitum.
A high and mighty director of a large research establishment once put it like that: "After doing this kind of work for awhile, you start to realize that this not a suitable occupation for a self-respecting human being. That's when you realizethat you need graduate students".
You appreciate now why we need to have all those students. They enjoy (we believe) doing this kind of work for their
Master or PhD theses.
The figure above shows just one of the many curves produced by scores of graduate students. It shows what you
get for 4 % Al in Cu "tempered" at 150 oC (302 oF) for quite a while. Note that 1000 hours equal 6 weeks. What wasmeasured is the yield strength or hardness as we know by now.

Iron, Steel and Swords script - Page 204

The Aluminum - Copper Experiment Explained
What we did was hardening our Al - Cu alloy by ageing. What happened is very clear (and supported by much moredata). It illustrates quite nicely what hardening any metal is all about. You know, of course by now that it is all about the
obstruction of dislocation movement by obstacles.
Now let's look at the data.
For the first few hours of tempering the tensile strength (or hardness) goes down because extremely tiny
precipitates or nuclei form. That reduces the number of obstacles a lot. For example, if If you form agglomerates
that of just three Cu atoms, you reduc the number fo obstacles threefold,. In a volume that originally contained 90
Cu atoms for example, you now have 30 three-atom agglomerates. Each tiny precipitate or nuclei might obstructdislocation movement a bit more than a single Cu atoms but since you don't have that many obstructions any more,
the total effect is less obstruction to the onslaught of the dislocations. Look at the analogy again.
Eventually - after about 7 hours of annealing - the precipitates grew large enough to seriously obstruct dislocation
movement and the "hardness" goes up. "Seriously" means that for example a 100 Cu atom precipitate obstructs
dislocation movement more than 100 single Cu atoms.
The hardness reaches a maximum after about 100 hours; obviously at this point in time we have the optimal
number-size relationship for the precipitates. Around this time we may also have used up all the available copper
atoms.
If we keep at it, the hardness will go down again. That happens because now Ostwald ripening takes over. All
copper atoms originally dissolved in the aluminum are used up and imprisoned in precipitates. Further growth of
precipitates can only happen by the bigger ones cannibalizing the smaller ones, and that is exactly what happens.
We get fewer and fewer but larger and large precipitates. Few and very large precipitates do not bother dislocations
all that much, hardness goes down.
Of course, we can learn far more from an analysis like that. But that involves
cumbersome details and an equation or two. The link provides for that.
Here we just note that the battle line scenario given before is rather realistic and
now we even know how to deploy the troops we have in the best possible way - in a
simple little war and without regard to money.
Iron is a far trickier opponent then aluminum when it comes to hardening, and it
fights dirty. We also need to get to terms with it on a limited money and timebudget, so we aren't done yet.

Advanced
ModuleThe Al-Cu
systemBut let's continue with looking at the results of the beautiful Al - Cu experiment and ponder some of the topics it
touches upon.
All in all, the maximum hardness we could produce is almost three times larger than the minimum one, and that's quite
an achievement. Moreover, we know exactly what is going on, and we can control it to a large degree.
If Ostwald ripening seems still strange, here is a comforting thought. You canwatch it happen while drinking beer. Right after pouring the beer consists of aliquid and foam (the head).
The head consists of many tiny bubbles formed by a thin membrane of the liquid
and the gas enclosed. The beer is very unhappy with this. Its nirvana state would
be what we call "flat" - no bubbles! Why? Because foam means liquid with a lot of
surface area and thus unnecessary energy.
So Ostwald ripening commences. Some bubbles collapse, giving the gas they
contain to others that are now bigger. And so on. Big bubbles come into being by
eating up small ones (provided you let it happen before you guzzle them up). The
reason for that is the same as for precipitates: the driving force is the possible gainin surface energy by reducing the surface area as much as possible.

Fun
ModuleBeer bubble
science

Isn't that great? Finally you have a good reason to drink a lot of beer because you are actually doing science,
studying Ostwald ripening.
Since it's a complicated process when you look at the details, I recommend lots of studying. You might augment
your studies with some Swiss cheese, realizing that the holes in there are precipitates of some gas that actuallymust have started with lots of little ones but, thanks to the second law and Ostwald ripening, developed into the few
big ones you are familiar with.
Back to beer cans. (Hey, another scientific reason to drink beer!). With all the work that produced the figure above, we
now know one temperature profile that forces Aluminum plus 4 % of copper to do what we want - within the basic limitsof the system.
It is a simple profile: Cool rapidly to room tenpertures and then go up to the desired temperature. Keep thattemperature constant for as long as you fancy, then drop quickly to room temperature.
Simple - but there is a catch: it takes too long for the best result - about 100 hours! Far too expensive. So, maybe,
we should:
Raise the temperature a bit, from 150 oC (302 oF) to 170 oC (338 oF)?
Start annealing at 150 oC but then go slowly up to 200 oC (392 oF)?
Do it, perhaps, the other way around.
Use 5 % or 3 % or ?% copper.
Iron, Steel and Swords script - Page 205

Use some other atom instead of copper.
Your suggestion.
You can spend any amount of time tinkering around with optimizing beer cans, boring your female graduate
students to tears. Nevertheless, you can never be sure that you found the best way to make your beer cans. So
let's have another big epiphany:First law of Practical Science:
There is nothing more practicalthan a good theory

If you have a (mathematical, of course) theory about hardening aluminum (and anything else) you could just calculate allof the above. It not only saves a lot of time and money, you also can be sure that you arrive at the best possible process- not to mention that your graduate students now can try their ken at something more challenging, like making superior
steel for swords. And you have more time to study Ostwald ripening with beer, so everybody profits.
You have a why question? Why, for demonstrating how to outwit the second law, did I pick an example from theboring world of aluminum and not from the exciting world of steel ?
Well, I invoked the principle of supreme laziness.
The iron -carbon system that we call (carbon) steel is far more complicated than the Al - Cu system. Looking at acomparable experiment for steel would have needed far more writing, which is hard work that keeps me from studying
Ostwald ripening.
OK. Just to keep you in good humor, here is an actual and interesting steel example:

Yield strength (or hardness) increase of "mild"
and rather soft sheet-metal steel at room
temperature.

We have soft, low-carbon sheet-metal steel that shows the effect of ageing at room temperature. Its hardness
changes ever so slowly at room temperature but after a year has passed it is substantially increased.
You might think that this is good. No. it isn't. Hard is not always better than soft; hard steel sheets can be quite
irritating if you want to shape the stuff easily. The Aluminum foil you use to wrap your food with shouldn't be too
hard, for example.
What has happened? First of all, you still have some excess carbon in this iron at room temperature. Not all of the
stuff has precipitated into cementite, probably because it was cooled too quickly. That's easy to do with thin sheets:
just letting it "sit" after hot-rolling might be sufficient.
At room temperature carbon interstitials and some other interstitial like nitrogen (N) are still a little bit mobile; lookat the numbers I provided a long time ago. The carbon atoms move ever so slowly (roughly a few µm per year) until
they get caught at some precipitate or in the core region of a dislocation, where they come to rest.
The net effect is that they make it more difficult for the dislocations to move when the need arrives, and that means
the material is now harder.
Now let's get back to the topic we're actually looking at. You probably forgot it by now, so let's dedicate a wholeparagraph to it.

Iron, Steel and Swords script - Page 206

8.3 Hardening Steel - the First8.3.1 Forming your Battle Line: Solid Solution and Precipitation Hardening.
The Cost Issue
We are there. Finally! From now on we will only deal with steel because you now have amost of the major tools in yourpossession that we shall need for hardening steel.
Thank God, I don't have to tell you anymore that hardening means to increase the hardness, and that this is the sameas raising the yield stress. You also know how the yield stress is defined, how it is measured in a tensile test, and that
it is just a measure for how easy or difficult it is to move dislocations. You know what a dislocation is, and how its
movement induces plastic deformation.
That's why from now on I won't make links anymore whenever terms like those are coming up.
We start with solid solution and precipitation hardening of iron and steel. We have more or less covered that topic
already; look up some old figures. This link beautifully illustrates what we are discussing in the context of battling
dislocation movement.
What we have seen in the aluminum - copper case is that single atoms of copper in aluminum are more effective at
obstructing dislocation movement than very small precipitates of copper atoms.
Large precipitates are inefficient too, because you can only have a few of those. So there is some optimal
combination of size and number; the Al-Cu system nicely illustrated that.
The aluminium - copper system also demonstrated that the strategy derived from "theory" works well. Should we now
use the same strategy with steel? Find the best element to alloy iron with and then get going?
No, we shouldn't. There are several problems. One is particular virulent for modern smiths (or engineers, as we callthem now). It's called: money. About the others we shall see shortly.
The money problem is simple and obvious. In our fast-living, sometimes enlightened, but always cheap age, you, themodern engineer, just do not have all the time and the money in the world to make your steel and work with it. Costs
matter. Very much so.
Cars would not be affordable for the likes of me and possibly you, if car bodies still would have to be made like aold-fashioned sword or a suit of armor. Those were expensive items in their ages that only people could afford who
were quite rich. Richness then mostly came from robbing your serfs and underlings - at sword point, if necessary.
Let's be happy that in our enlightened times the politicians bankers robbers usually don't have swords.
If costs matter we must compromise. Quite a lot actually, if we want to produce large amounts of cheap steel. We
now run into the eternal conflict between the great things one could do in principle, and the things that eventually will
make money. Let's call that the great cost issue .
By the way, we are going through that stage right now with solar cells. We know
exactly how to make superior solar cells if money and time doesn't matter. If it
does, and for solar energy it most certainly does, we must and will compromise.
There are a lot of parallels between the development of mass -produced cheap but
still good steel after about 1850, and what's going on right now about massproducing cheap but good silicon for solar cell production.
I wrote that around 2012. I'm happy to report that solar cells are now (beginning of2015) cheap enough to make it on their own, without subsidies, on a highly
competitive energy market. And they will et cheaper and better in years to come just like steel about 150 years ago.

Advanced
ModuleSolar Cells

But back to steel. We could make superior steel by starting with very pure iron and alloy it with the whatever is best formaking extremely hard but still very tough steel. We actually do to some extent!
We alloy our top steels with several elemtnts in just the righ amounts and use optimized temperature profiles to produce
the best possible combination of precipitate type, size and concentration. The principles are the same as the Al - Cu
example but the reality is far more complex.
What you might get is, for example, "maraging" steel. As suspected before, it actually does not use carbon as
the key element for hardening, but you don't have to worry about that - most of us couldn't afford maraging steel forcar bodies or other bulk uses. I will come back to maraging steel later and then also explain the meaning of theterm "maraging".
Taking the great cost issue into account we must try to live with rather dirty iron, and with carbon as the major alloying
element.
That's more or less what you, the ancient smith, had to content with anyway, even so you didn't know about that. The"more or less" refers to a facet of steel lore that I have not yet mentioned but saved for now:

Iron, Steel and Swords script - Page 207

A lot of ancient steel contained phosphorous (P) and not carbon (C)as the major alloying element.
I'll get to this in due time. For now let's concentrate on the dirty iron - carbon system. Whenever possible we evenignore the dirt. If it is not possible, I will tell you.
Solid Solution Hardening in IronFirst let's look at solid solution hardening, or hardening with atomically dissolved impurity atoms. In order to get cleandata, we need to do this in a lab-type experiment, paying no attention to the cost issue.
What exactly are the effects we can get with carbon or other elements that are being kept in solid solution inside
an iron crystal with respect to hardness and so on? Here are some data for iron and for comparison for really soft
copper (Cu):

Solid solution hardening in ferrite.
High concentrations of dissolved C, N and P are notpossible.
All curves would converge around 25 MPa for zeroconcentration, showing that pure iron is very soft.

Solid solution hardening in copper.
Note the difference in scales!
RP, you remember, is the critical yield strength andmore or less the same as hardness

Iron, Steel and Swords script - Page 208

The curves always refer to the best we can do with pure iron or pure ferrite, as we now always call the room temperaturebcc crystal. Now you see the other problems besides the cost issue alluded to above.
1. There is a definite hardening effect for all the impurity elements shown. But what we get in all cases is still rather
soft ferrite. Look at the Al-Cu system again for comparison. There we got a maxuimum yield stress (RP) of about
350 MPa (Mega Pascal; last time I remind you about that!) for Cu-precipitate hardened Al. Even the softest
version of our Al-Cu system with about 150 MPa is about as hard as most iron-impurity systems in the picture
above. When we talk about hard steel, we talk about at least 500 MPa.
2. The "best " elements for solid solution hardening are the interstitials: carbon (C) and nitrogen (N) plus
substitutional phosphorous (P). So why don't we increase their concentrations, extending the curves to larger
yield stress RP or hardness values?
Because the phase diagrams tells you that you cannot keep larger concentrations in solid solution at room
temperature. We already know that for carbon (this link gets you there); more than about 0,1 % at hightemperature can't be done. For the date in the figure above thus a few tricks had to be used to keep the atoms insolid solution. That's also true for nitrogen and phosphorous; look it up yourself.
3. The substitutional atoms like Silicon, (Si), nickel (Ni) and so on don't help much either. For a yield stress of 500
MPa you would need rather high concentrations and it is not so likely that you can keep high concentrations insolid solution. Just check the phase diagrams.
4. If we use dirty iron as we must, e.g. iron with some carbon and some of the other elements, all kinds of otherthings can happen. We cannot simply add the effects of different atoms. In other words: putting in, for example, 1% silicon (Si) and 1 % molybdenum (Mo) will not necessarily give you a yield strength of about 300 MPa. It might
be even worse than it is for just one of these elements.
By the way, the curves above are based on 11 different phase diagrams, as you must have noticed. It makes nosense to ask our graduate students to make a sample of iron with x % of some impurity in solid solution, if thephase diagram tells you that it can't be done.
I do hope that you appreciate that those simple looking curves above are based on a hell of a lot of work.
What you learn is that carbon is indeed the most efficient single mercenary that you can field in the fight against
moving dislocations, but that it will not do you much good. The first law of applied science asserts itself once more.
The figure on the bottom, just for the hell of it, shows exactly the same thing for copper (Cu). I spare you the rest of
the metals but rest assured that there is a lot of data.
What you learn is that pure copper is rather soft, indeed, in comparison to pure iron (look at the numbers on thescale!) and that you can harden it quite a bit with half a percent or so of antimony (Sb), tin (Sn) or indium (In).
Nevertheless, it is still rather soft. Tinkering in your garage with the goal of making a copper (alloy) sword with ayield stress of 500 MPa or so, thus will be foolish. There is nothing more practical than a good theory!
Note that Silicon (Si), doing not too badly in iron, has almost no effect in copper.
Precipitation Hardening in Iron
How about a lot of carbon in iron. Far more than the solubility limit in ferrite or α-phase at room temperature? Than thesystem will produce cementite precipitates and we can go for precipitation hardening.
Yes—but! We know that as long as we cool down slowly enough, what we will find is:
ferrite + pearlite for hypoeutectoid compositions;pearlite + cementite for hypereutectoid compositions.
No more links to what should be elementary stuff by now as I have promised or threatened, whatever it is to you. Incase of doubt look it up via the index.
So, yes, the carbon beyond the solubility limit does precipitate and form cementite. However, it will not form abunch of small and more or less spherical cementite particles as we would like it, but far more complex structures,
especially for carbon concentrations > 0,7 %, i.e. hypereutectoid carbon steel.
In order to keep things simple, let's first look at hypoeutectoid steel with rather low carbon concentrations. That will span
the range from wrought iron to mild steel.
Mild steel produced by cooling down no too fast must have a structure consisting of pure ferrite grains plus some
pearlite grains, just as shown here. The ferrite grains will have dissolved as much carbon as possible (about 0,02 %)and thus have a yield stress around 200 MPa, as we can deduce from the picture above.
The pearlite grains are much harder since they contain cementite. Cementite is brittle at room temperature and thus
impenetrable to dislocations. Dislocations may still move in the ferrite between the cementite lamellae but pearlite
grains are a formidable obstacle to dislocation movement. They thus introduce a less ductile and more brittle
component.
We can make an educated guess that an increasing carbon concentration (but still well below the eutectoid
composition) will produce the following effects with increasing carbon concentration:
The yield strength will increase from a starting value of about 150 MPa to values far larger.
Ductility or the maximum elongation will go down.
The fracture energy will go down as well.
Closer to the eutectoid composition new things start to happen and these trends may change.
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Now let's look at hypereutectoid steel.
That's simple. For carbon concentrations well above the eutectoid compositions and "normal" coolin we must
expect that we have pearlite grains completely encased in primary cementite, just look at that fantastic picture
again. In this case we expect a hard and completely brittle material.
If we are just a little bit above the eutectoid composition, some ductility might still be there.
What we get experimentally for plain carbon steel is shown below:

Effect of carbon on steel properties. The verticalline at thecross marks the eutectoid composition"Normalized" and "Annealed" refer to the starting
structure. Yield stress RP (and ultimate tensile
strength RM), fracture energy and ductility (maximum
strain or elongation) behave pretty much as expected.
It is more or less what we expected. With increasing carbon concentration the yield strength goes up, the fractureenergy down. No surprise here.
This trend, however, already weakens around 0,5 %, long before the eutectoid composition is reached. That is,perhaps, a bit surprising?
Well - no! Plastic deformation needs dislocations to run through the whole sample. This means that there must be acontiguous region of material from one end to the other through which dislocations can run. It is like electricalcurrent. If you don't have a conducting path between two electrical terminals, no current will flow - no matter how
much conducting materials, mixed up with isolating material is in between.
Let's visualize what is going to happen if we have two kinds of grains in some variable kind of proportion inside somematerial. One kind of grain is a "conductor" for electrical current or dislocations, the other one is an "isolator" electrical charge or dislocations cannot move inside these grains. Highly stylized and for only 2 dimensions we getsomething like this:

Percolation of electrical current or dislocations
through a mixof 39 grains. White ones are conducting andgreen ones are not

Iron, Steel and Swords script - Page 210

The hexagons symbolize grains. White ones can conduct electrical current or can be deformed plastically, i.e.
dislocations in these grains are mobile. Ferrite, for example, can do both. Green grains are insulators and do notsupport dislocation movement. This would be the case for pure cementite. Pearlite, however, is still a good electricalconductor (because of the ferrite in there) but almost an insulator with respect to dislocation movement.
An electrical connection between left and right is shown symbolically, and the dotted purple arrows illustrate someof the possible pathways for electrons or dislocations that lead from left to right. The percentage of statistically
distributed green grains increases from about 20 % to 50 % and it is immediately apparent, that at some criticalpercentage, no more flow or percolation of electrons or dislocations from left to right is possible.
The word percolation refers to the twisted step-by-step flow of whatever; you know that from the percolator that makes
your coffee. Percolation science is more demanding than coffee making, however.
For example, if you extend the problem posed above to three dimension and ask at what percentage of statistically
distributed insulating grains the mix switches from a conductor (at least one current path can still be found) to an
insulator (no current paths' anymore), the answer is not easily calculated. It' happens when about 3/4 of yourspheres are insulators.
If we take that as a rough guess for dislocation movement too, we expect that around 75 % of the eutectoid
composition it is also all over for dislocation movement. In other words, around 0.75 · 0.8 % C=0.6 % C we expectthat yield strength and fracture energy "bottom out", i.e. don't change much any more. That is rather what the
curves above show you.
What we will get depends of course not only on the carbon concentration but also on the structure of the specimen
before the tensile test was done. We have already learned that one and the same steel can have completely different
properties depending on its history.
They only way to get comparable results is thus to first "anneal" or "normalize" the specimen. For today's steels
you get precise instructions of how to do this. In essence you have to keep the steel at high temperatures for a timethat is sufficient to achieve a state close to nirvana (done by annealing; takes a long times) or at least not too far off(normalizing; shorter time).
Now you know about solid solution and precipitation hardening of plain carbon steel. A bit disappointing, isn't it? We canget a yield stress of 500 MPa but for a high price: the material is also rather brittle.
For good swords we should be able to do better. So next we need to look at the remaining straight options for
hardening steel.

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8.3.2 Size Matters
Grain size matters for hardness. If you want to increase hardness, small is beautiful.
Grain boundaries are very serious obstacles for moving dislocations. In our military analogy, they act like fortified
borders between states. The smaller the grains, the more grain boundaries you have, the harder the material will be.
Unimaginative, as engineers sometimes tend to be, we named this hardening mechanism "grain size hardening".
But scientists are often quite imaginative when if comes to naming new things, not to mention using good scientificnames for unscientific purposes. I'll give you examples in this link.
Back to the boring stuff. If you make your grains four times smaller, hardness will go up two-fold. No equations. I
promised. But you realize there is a square root in there somewhere. Below, you can "see" it

Yield strength (or hardness) vs. grain size forstainless steel
Source: Kawasaki Steel

It's a 12.5 % Cr, 9.5 % Ni, 2 % Mo, 0.1 % N steel. The blue lines give error margins or scatter of results. Note thatyou get a linear relationship if you plot the data vs. one over the square root of the grain size (see how cunningly I
avoid equations?). In carbon steel the numbers are different but the general relation is the same.
So grain size hardening can quadruple the hardness!
Great - but how do we make small grains? The crystal hates small grains, nirvana calls for huge ones. Once more weneed to fight the second law. The problem is that no matter what you do during forging, grains will tend to get larger,
never smaller.
Banging with your hammer a low temperatures might help, but not all that much. If you run your steel through aroller mill, it will get much flatter and the grains will become elongated (see this picture) but their size as measured
by their volume does not change much.
Kawasaki steel, presumably knowing what to do about steel, obviously had a hard time to get grain sizes below
about 1 µm for making the measurements shown in the figure above as evidenced by the far larger error bars for thesmall grain sizes.
So let's forget about grain size hardening for forging swords. There may or may not be some improvement on grain size
(meaning they get smaller) that is caused by what you do, but you have no good control and therefore you cannot use it
systematically. Worse, chances are rather good that by what you do you will make the grains bigger.
Now for a new thought: "OK, agreed, I can't make the grains smaller - but, maybe, I can keep them from becoming
bigger?"Yes, you can!
If grains grow, their grain boundaries and thus also atoms have to move. So make grain boundary movement difficult.
Since you must heat up your steel during forging, unavoidably supplying vacancies and whatever else is needed foratoms to move, the prerequisite for grain boundaries to move are there and your options are limited:
1. Minimize your "thermal budget", i.e. the weighted product of temperature times time. It must be a"weighted" budget because a few minutes at high temperature does more harm than hours at a somewhat
lower temperature.
Another way of putting that is: minimize the total diffusion length of the iron atoms.
2. Add some impurities that make it difficult for grain boundaries to move. The trick, of course, is to identify
suitable impurities, get them into the grain boundaries, and avoid negative effects on other properties.
Not all that easy but possible.

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If you happen to be a modern smith (nowadays called Material Scientist or Engineer), you do not work with plain carbon
steel but with an iron alloy that contains more alloying elements than just carbon. Some of those elements might be inthere to do the job mentioned above.
Of course, if you are a modern material Scientist, you might also know the tricks of nano technology and you might beable to come up with "nano grained" steel that is quite hard just from grain boundary hardening as shown above.
Chances are pretty good, however, that you will fall into the "cost issue" trap. Your "nano" steel is too expensive
and nobody will buy it. Except, of course, the Pentagon or some Arabian King.

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8.3.3 Bang it!
When you "bang" your steel or induce plastic deformation or strain by some other means, you produce and move
dislocations. A lot of the dislocations produced will get stuck in your crystal and then act as obstacles to the ones thatare still moving. Your crystal gets harder and we have called that effect strain hardening; it is also known as work
hardening
Strain hardening thus means that your obstacles for dislocation movement are other dislocations.
In the invading soldier metaphor, it is clear from recent experiments along that line in Iraq, Afghanistan and so on,that you actually can impede the advance of your own soldiers by "stuck" soldiers from some other parts of yourmilitary. If, for example, your military bureaucracy grows faster than your fighting troops, you can be sure that it will
be a major obstacle for the guys out there.
We also have what is known as "friendly fire", not to mention basic stupidity—but that analogy becomes too painful
to pursue.
Strain hardening is an every-day phenomena. Bend a metal paper clip back and forth a few times and it strain
hardens, becoming more difficult to bend. Eventually it fractures.
You can see that effect rather nicely in the stress-strain diagrams I made for you. The steel gets much harder after
it was somewhat deformed and "strain hardening" was named as the reason. At that point, however, that was justdescriptive and not explanatory.
The measure for what can be achieved with strain hardening is not so much RP, the yield stress, but rather Rm, theultimate tensile strength. This is clear. You simply cannot get effects of strain hardening before you did some serious
straining.
So should I now make some steel, deform it until it reaches R m, and then use it for a sword blade? After all, it is
now as hard as it ever can get from strain hardening?
Don't. There is no such thing as a free lunch and the prize you have to pay for excessive strain hardening is clear:
your steel will now break at the slightest provocation.
Think about your paper clip or look at the stress-strain curves again.

Stress - strain curves showing the effect of strain
hardening

We have a piece of C15 steel (whatever that means). If we do a tensile test until the bitter end we would get the blue
curve. The specimen yields at RP 1 and that defines its hardness. For fracturing it, you need to go up to its ultimate
tensile strength and for that you must almost double the stress needed to induce first plastic deformation.
Now you deform your C 15 steel only up to the green point; almost at the ultimate tensile strength (the maximum of
the curve). You give the deformed steel to your smith and tell him to make a sword out of it. Your smith will find that
he was given rather hard steel and makes a sword with a hard blade that will fracture at the slightest impact. Why?
Easy to see, If you don't give the pre-deformed steel to your smith, but to your tensile-test engineer, she will find thered stress strain curve. The specimen now yields at RP 2, exactly the stress where you finished the first tensile
test. it is no much harder. After yielding occurred, the curve continues exactly as it would have in the first tests if
you hadn't stopped the machine. It takes only a tiny bit of more stress after RP 2 has been reached and yourspecimen fails (after first deforming rapidly a bit more than 1%)
So beware. Banging your steel a lot at low temperature is sure to induce strain hardening. At the same time, ductility
decreases.
Banging a lot at high temperatures well above the austenite transition temperature will do not much good for strain
hardening, though, because now you work with a different material (austenite) that changes completely upon(slowly) cooling down. It will not "remember" your banging.
Iron, Steel and Swords script - Page 214

Banging a lot at high temperature just a little bit above the austenite transition temperature and cooling down not too
slowly might do all kinds of things including some strain hardening because you make it difficult for your steel toachieve nirvana and to rid itself of the defects around at high temperature.
At that point we can start to appreciate a basic problem that you, the ancient smith, faces when you forge a sword
blade.

How do you know how far away from thetransition temperature you are?

You didn't have a thermometer, for God's sake! You didn't even know the meaning of temperature; you only hadsome vague notion of pleasant, hot, very hot and cold.
The standard thermometers from today, by the way, couldn't take the heat either. Look up how you would measurehigh temperatures today.
And no! Don't deceive yourself:. Being able to distinguish between hot, very hot, and unbelievably hot was not goodenough. Precise temperature control matters a lot in blade forging! I will come back to that later again.

Iron, Steel and Swords script - Page 215

8.4 Be Cool!

8.4.1 Martensite
Surprise!
It's clear by now that most of the time the crystal wants to do the opposite of what you want it to do. The crystal wants
big grains, large precipitates, and few dislocations - in other words, it wants to be a softy.
For sword blades we want the crystal to be hard and tough. Nothing helps but to interfere massively with its preferred life
style. The way to do that is to be cool 1). And to get your steel to be that too - and presto!
We know that the first strategy for keeping the crystal from doing its thing is not allowing it enough time for moving
its atoms around.
In other words: we must quench the crystal, we cool it down from some high temperature real fast. If we do thatfrom a temperature above the austenite transition, the crystal has very little time for rearranging its own atoms fromfcc austenite to bcc ferrite and in particular for getting most carbon atoms out of the newly formed ferrite in order tomake cementite.
If the time is simply too short to produce pearlite and whatever else is called for by the phase diagram, new things
must happen.
Let's look at the extreme: If you could cool down arbitrarily fast, atoms can't moveat all and you would find the same structure at room temperature that you had at
high temperatures.
In the laboratory or in special factories we can do this under special circumstances
for special geometries. We can cool a thin piece of any metal down from above
1000 K to room temperature in a fraction of a second. What we get are thin ribbonsof amorphous metal that are quite useful for example when it comes to magnetic
properties.
Many metals then "freeze-in" the liquid structure they had at the high temperature
and are amorphous solids with peculiar properties. The process is called " melt
spinning" and you can look it up if you want.

Advanced
Link
Meltspinning´´When we cool down extremely quickly we do not get the nirvana state as called for by the phase diagram but ametastable phase that tries as hard as it can to change to the stable one. Since this takes some energy,
metastable phases—like diamond—can live very long at room temperature. However, as soon as you heat it up to a
sufficiently high temperature it will transform to the stable phase.
Melt spinning of iron or steel does not produce anything even remotely thick enough to be useful as sword blade.
The best you could expect for a real sword blade is to quench it so fast that parts of the austenite structure are"quenched-in", at least in the outer parts of the blade that cool down the fastest. That is the best you can expectwith what you have learned so far. If that expected structure would be good for sword blades is not yet clear,
however.
Surprise!

Something unexpected will happen!
The "best" you and everybody else could reasonably expect does not happen! Plain carbon steel does not freeze
into the austenite structure, no matter how fast we cool it down. Plain carbon steel still has a big trick up its sleeve.
If we cool it real fast, it produces something completely new, a kind of metastable phase, that we call martensite,
after Adolf Martens (1850 - 1914).
Martensite formation is rather strange. It does not happen gradually while we quench. It happens all of a sudden at
temperatures as low as just a few 100 centigrade when single atoms can't really move much anymore. But
dislocations still can, and martensite formation is a process that involves lots of dislocations.
Let's look again at the driving force business before we proceed with martensite formation. Let's look at you (and me) forthat. You and I are supposed to be good and law-abiding citizens. I'm sure that you strive all the time to achieve thesupreme state of being a good, responsible, law abiding, and so on citizen, who reads educational stuff like this article,
instead of guzzling beer and munching extremely unhealthy food.while watching scantily clad females on TV doing
things that your local moral authority would not approve of.
I also do some of that on occasion. Especially whenever the need to be particular good is not so pressing because,
for example, I still fit into my clothes or my wife is not around.
However, if the deviation from what I should be weight-wise (for crystals it would be nirvana-wise) becomes larger,
my attempts to achieve the proper state of being become more severe. Shortly before I would explode, I will takerecourse to desperate measures and drink water instead of beer.
Iron, Steel and Swords script - Page 216

We are talking driving forces here once more. What's weight difference for me, is energy difference for crystals.
If you are still in the austenite state and it is just a little bit below the transformation temperature, things are notserious yet. The difference in energy between ferrite and austenite is small.
But being still in the austenite state a lot below the transformation temperature is really, really bad. Ferrite now
would have a much lower energy than austenite. This state of being cannot be tolerated anymore.
The need to turn from an fcc austenite crystal into a bcc ferrite crystal gets absolutely peremptory. All your atoms
are involved in this because they all need to change their surroundings from 12 next neighbors in the fcc austenite
lattice to 8 in the bcc ferrite lattice.
In addition, you also would like to get rid of the carbon in the ferrite or α phase. Ferrite atoms just do not like to havea carbon neighbor. Getting rid of the carbon is a bit less pressing, however, since it concerns only those of your ironatoms that are next to an interstitial carbon atom whereas the need to be ferrite concerns all.
Getting rid of surplus carbon would mean to move individual carbon atoms from wherever they are to somewhere
else. But individual atoms can't be moved in a civilian way by diffusion anymore, so you simply cannot make carbon
free ferrite grains, period.
The only two options left are to remain (metastable) austenite or to go for martensite as a compromise. It's a lousy
thing to do but better than to remain austenite.
So, what exactly is martensite? A rather special microstructure or arrangement of iron atoms! Even with our present
knowledge of what crystals are and do, fortified with a phalanx of heavy computers, I doubt that we would have predictedmartensite formation. It seems that crystals are still smarter than we are when driven to extremes.
Martensite formation also occurs in other metals and it is a pretty queer thing there too.
When people like Adolf Martens saw martensite in their optical microscopes, they could not know what they saw
and how exactly that stuff had formed. But they could describe it and give it a name. They also figured out that themartensite in steel was extremely hard and thus useful.
So once more, what is martensite?

Martensite is a distorted bcc ferrite
lattice in parts of a steel crystal
that still contains dissolved carbon
and is full of defects" Distorted" means that instead of a perfect cube you have a (slightly) elongated cube (or a "tetragonal "structure).
"In parts" means that particles of the metastable martensite phase are embedded in something else. Thereis no such thing as 100 % martensite. The something else could be regular ferrite / pearlite / bainite (wait) oreven some retained austenite.
"Still containing dissolved carbon" means that there is far more atomically dissolved carbon in the martensite
then would be proper for stable ferrite. That's why the lattice is distorted.
"Full of defects" means that there are lots of dislocations inside the martensite, for reasons we will see
shortly.
The hardness of martensite comes from the defects it contains, in particular from the dislocations. Hypothetical
defect-free martensite would be simply ferrite and that is not very hard.
The "Mysterious" Formation of Martensite
How does martensite form? That's a good question and if we Materials Scientists are perfectly honest, we have toadmit that some details still elude us.
Martensite formation in detail is so tricky that even modern textbooks are more confusing than elucidating. Let's firstlook at the standard model that Edgar C. Bain proposed in 1934. It illustrates how martensite formation could have
happened. Here it is:Iron, Steel and Swords script - Page 217

How a (distorted) red bcc lattice is "hidden"
inside a pink fcc lattice.
Shown are two unit cells of a close packed fcc crystal. The fcc lattice points are marked with pink or red spheres;
two spheres at the backside are not shown for clarity. The same spheres could also be taken as symbols for the
regular Fe atoms in an austenite fcc crystal. The green dots mark the possible positions for carbon interstitials in
the austenite crystal.
The (distorted) bcc lattice co-existing with the fcc austenite lattice is marked with red spheres and red lines
Bain realized that the face-centered close-packed austenite crystal (with the occasional carbon atom sitting in one of
the green positions indicated) actually contains a distorted body-centered lattice as marked by the red spheres in the
figure above.
It's a perfectly rectangular lattice but not a cube since one side is longer than the other two (that makes it
tetragonal). Your halfway decent general education should enable you to find out the precise dimensions of the red
cuboid.
All that the fcc austenite needs to do for turning into a bcc ferrite crystal is to expand a little bit laterally (x and y
direction) and shrink a bit vertically (z direction). Doing that would be a great way to satisfy that urgent desire to
become bcc. But how could one do such a transformation all over the crystal in not just one elementary cell of thecrystal but in many connected ones? For doing this not only do the atoms need to move, they all need to moveprecise amounts at the same time.
Even if we ignore the carbon for a moment, which shouldn't be there after turning fcc austenite to bcc ferrite, the only
way of doing this Bain transformation is to move a lot of atoms in lockstep, sort of in military fashion.
The regular way, given time, would have been to move the atoms one by one, each one running around pretty muchat random, or in a civilian fashion.
I didn't just make up those words by the way; they are well known in metal engineering and I have introduced themalready some time ago.
If you, the crystal, now start to entertain thoughts of " transformation by military movement", you run into major
problems (as always when asking the military in tough times to solve a problem):
1. Even if you move your atoms in military fashion, you must start somewhere. Some nucleation is required and thatis mostly difficult, as we know now. It is not very difficult for the iron in this case, because you just use whatever
defects happen to be around. In real life you just invent some atrocity perpetrated by the enemy (look up"Lusitana" or "Gulf of Tonkin incident") or let the enemy do its worst (Pearl harbor). If all else fails you fake anattack ("Gleiwitz incident").
2. If you take the red cuboid in the figure above as a nuclei for the Bain transformation, and make it into a real cube
(easy to do in your brain), it is obvious that it just doesn't fit into the remaining lattice anymore. If you then movethe boundaries between the new and small bcc part and the fcc austenite (you have seen one!) outward into the
fcc part (making the martensite grow), the newly created martensite will simply not fit properly into the volume
inside the austenite that its atoms occupied before the transformation. You have to press and squeeze like hell tomake it fit. The second problem therefore is that a lot of stress will be created by a Bain transformation. Since
you attempt the transformation in order to gain energy, and since stress means to put up energy, this is notgood.
3. The third problem comes from the fact that so far the only way to move atoms in a military fashion is by moving a
dislocation through the crystal. If you try to do this, you sooner or later realize that dislocation movements always
produce a shear deformation. The Bain transformation, in contrast requires "push / pull" or, as we call it, anormal deformation . The differences are made clear in the figure below; you might also want to use this link.

Iron, Steel and Swords script - Page 218

Normal and shear deformations
There is a little theorem going with this: Normal deformations preserve the anglesbut change the volume. A cube
turns into a cuboid. Shear deformations preserves the volume but not the angles. A right-angled cuboid turns into
something crooked, for example.
The long and short of this is: The Bain transformation as envisioned is a bit too simple minded. Nevertheless, it shows
the general direction of what is going on. All we need to do is to figure out how to produce something akin to the Baintransformation by shear and not by "pulling and pushing".
Luckily, a nice little theorem in more advanced math tells (some of) us that every deformation you can produce in
one way, e.g. by pure push / pull, can also be produced in the alternative way (pure shear) and vice verse. All you
need to do is a proper "coordinate transformation". That involves mathematical things far worse than vectors so wesure don't want to go into this. Let's only note:
Understanding what happens when martensite formation occurs is best visualized by the Bain model above,
employing normal deformations.
Understanding how it happens is best visualized with some (very schematic) drawings showing shear
deformations.
The synthesis of both views is easy - in "tensor math".
You sure don't want to go into some of the more sensible questions either; I just list them to give you an idea of thecomplexity of the issue:
Are there other almost bcc type lattices hidden inside the fcc lattice that can be made into proper bcc"cubes" by some (shear) deformation?
If there are, will there be a "bad fit" problem leading to stress?
If there is a stress problem, can I do something to mitigate it?
It's not possible for us to work that out for iron (and plenty of other cases) without a bit of advanced math, so I won't eventry.
Iron, however, found out how to form martensite without math. In what follows I will try to give you an idea of how its
done. There is, however, no way to make proper three-dimensional drawings of what is really going on; schematic
illustrations in two dimension must suffice:Schematic drawing of
Schematic drawing of how
how the martensite ismartensite ( pink bcc lattice)made to fit into theforms from fcc austenite
crystal by plastic(white)deformation.
by a shear process.
Three dislocations haveAlso shown is a dislocation
moved all the way throughmoving through the martensite.
the martensite.
Iron, Steel and Swords script - Page 219

The (slightly distorted) cubes of the bcc lattice are notobvious because we look at it from some special direction.
Look at this picture to see that you don't always see the
cubes.
The black lines are meaningless. They just "guide the eye"to recognize the dislocation (red line) and the shear
deformation
The black arrows in the left drawing show what kind of atom movement by a shear deformation will yield martensite.
In addition, a dislocation in the sheared part (=pink martensite) has already moved parts of the martensite one stepto the left.
The drawing on the right shows how the bcc crystal formed by shear (=pink martensite) is made to (almost) fit into
the host crystal again by moving three dislocations through it on the dotted red planes.
The lower part of the schematic crystal is just "sheared" to the right by moving all atoms on a horizontal plane by thesame amount as indicate by the black arrows. The amount of shear increases with the distance from the phaseboundary that must form by definition.
A shear like this is related to what we called "twinning" but we do not need to worry about this here. All we should
know is that shear as shown can be produced by moving a hell of a lot of special dislocations (not shown) in a peculiar
way. How that works is shown in the twinning link.
Why is the sheared off part now a bcc lattice? In the picture this cannot be seen.
Well, for real crystals the shear is not just in the paper plane but has also some amount out of the plane. The wholething is just impossible to show edge-on. I won't even attempt to draw it three-dimensionally in the proper
perspective view; that would be far above my skills. It's probably above anybody's skills since nobody so far has
made such a drawing.
It's far easier to write down a few equations that show it all and more. Provided, of course, that you can "see" what
linear matrix algebra can "show".
Just believe me that with just shearing as shown schematically, you can make a (very slightly distorted) bcc latticeout of a fcc lattice. That's what the right-hand part of the figure attempts to illustrate.
After a suitable shear, involving movement of a lot of atoms in military fashion, the crystal still faces a severe stressproblem. As the figure clearly shows, the sheared-off part that is now bcc martensite would not fit at all into the stillpresent fcc part surrounding it.
The right-hand side of the drawing shows how to deal with that problem. Run suitable regular edge dislocations
through it on the dotted red planes, and you produce a structure as shown. Since those are regular dislocations, incontrast to the special dislocations producing the original shear, you can run as many as you like through themartensite and it still remains bcc martensite.
After enough dislocations did their work (and note that many of them will get stuck on the way!) the bcc martensite
part now fits into the "parent" fcc phase, if only with some effort. and some remaining stress.
Notice that I called the product of all this shearing and deforming "bcc martensite " and not "bcc ferrite"!
Why? Because after this whole process of shearing, involving moving a lot of atoms at once in lockstep, i.e. military
fashion, by running special dislocations through it, then running a hell of a lot of regular dislocations through the
newly formed bcc martensite, then squeezing everything elastically (just changing the distance between atoms
slightly) until the martensite fits into the space that its atoms formerly occupied, we still do not have a nice bcc
ferrite phase because we also need to consider the carbon!
All the carbon that was present in the fcc austenite is still in the bcc martensite because the shearing did do
nothing to the carbon atoms. They stayed right where they were with respect to their iron atom neighbors. After themartensite formation happened, they can't go away anymore either because it's too cold. The net effect of that isthat the bcc martensite is not really bcc, i.e. body-centered cubic but a bit elongated in one direction. In otherwords, the carbon in the martensite is incorporated in such a way that it induces a small normal deformation andinstead of a cube we get a cuboid as shown in the figure above
For being bcc, it is necessary to be strictly cubic (the "last "c" in bcc stands for cubic). We do not have thatanymore, we have a cuboid that the likes of me call a body centered "tetragonal" lattice.
What that means should be clear: In pure iron, or iron with very little carbon, there can be no martensite. The
martensite transformation discussed above would just be a messy and complicated way for turning austenite into
ferrite when there is no better way.
Martensite is only something special if there is carbon involved. What that means is:

You cannot harden iron with too
little carbon since martensite
cannot be formed.
Iron, Steel and Swords script - Page 220

Not all of the austenite can transform to martensite, by the way. After nucleation, the rapidly growing martensite
particles, often in the shape of plates, lathes or needles, get into each others way and stop growing. So some austenite
might be retained in between, even so it is very unfavorable at room temperature. Also, if the quenching is not all that
rapid, e.g. deeper in the bulk, there might be enough time to form a little bit of ferrite / cementite in the usual way oreven orderly pearlite. What you get in the end is an awful mess of everything. And this mess is quite hard for reasonsthat should now be clear.
In an TEM electron microscope you can see it all. But even experts have problems unraveling exactly what theysee. Below are two pictures that serve only to show one possible general structure and the inside of somemartensite,

What martensite looks like in the transmission
electron microscope (TEM)
The black "feathers" aremartensite as seen at low
magnification in an electron
microscope.

At high magnifications it
becomes apparent that there
is an extremely high densityof dislocations (the dark,somewhat wavy looking
lines) inside the martensite
platelets or lathes.

Source: "Werkstoffkunde Stahl"; p 155/157

Describing martensitic transformations properly in mathematical terms, while not too difficult for the initiated, does
boggle the mind so much that we never attempt it in undergraduate courses. Thus nobody notices that a lot of
professors aren't too sure about it either. I will thus not go into this any more, except to summarize by enumeratingsome important points:
1. In a general martensitic transformation some kind of crystal lattice (bcc in our case) forms from someother kind (fcc in our case) by a military kind of transformation. Martensitic transformations can be found in a
lot of crystals besides iron. What exactly happens is rather difficult to conceive by mere humans but acrystal has no problem in doing it. If a lattice type transformation is required at some temperature by thephase diagram, but not possible by a diffusive transformation, the only way left to approach nirvana is a"military" shear transformation, and that we call martensite formation. If the driving forces are large enough,martensite formation will "just" happen. If that is not the case, the high-temperature structure will become"frozen-in"
2. While it is difficult to do the math, it is not impossible. Martensitic transformations are well understood by
now and there are many metals and alloys that produce their own kind of "martensite". For example, "shapememory alloys" work by martensitic transformations. You may never have heard about those things but
they have saved the life of many people because "stents", the little wire mesh things that keep your arteries
open, are made from them.
3. Martensite in steel is only extremely hard because it is full of carbon and stuck dislocations. Martensite invery low carbon iron is the ferrite phase formed by a martensitic transformation. Its properties are no different
from ferrite formed in the usual way by a diffusive transformation; it is rather soft. That is the reason why byquenching you can only case-harden steel with a carbon concentration not too low, inducing "true"martensite formation.
So if you quench your whole steel sword blade, only the outside and the thin parts—the edge—will cool down so fastthat hard martensite is formed. The parts that cool down fast but not fast enough for martensite, will also be somewhat
harder because cementite or pearlite formation in the normal way is still rather difficult. What one gets in this case iscalled bainite; I'll get to that. Martensite only forms form the surface down to a certain depth known as quenching or
better hardness depth. This is easily measured with a so-called Jominy test, use the ink for details.
Now you have a hard (and rather brittle) edge and you encased your whole blade in the hard stuff. That's why we call thiskind of hardening: "case hardening".

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If you want to avoid having the whole surface of your blade turning very hard (and brittle), you make sure that parts of
it cool down more slowly - by coating it with some clay or whatever. Therewith you provide thermal insulation of thecoated parts and reduce the cooling rate to a value where no or only very little martensite will form.
Here you have, in a nutshell, the Japanese way of making nihontos / katanas.
If your sword blade or whatever else you (case) hardened by quenching is now too hard and brittle, you temper it a bit.
We covered tempering in some detail with the Al-Cu example. When you allow a bit of atomic movement by tempering
after quenching, the crystal moves its atoms around in such a way that it gets closer to nirvana. For case-hardened
quenched steel the first priority will be to get rid of the martensite by turning it into ferrite, and that is done by castingout the carbon, forcing it to form cementite. Hardness then decreases but ductility increases. Stop tempering at theright moment and you have the compromise between hardness and ductility that is best for you.
Here is a diagram that shows schematically what you can do by quenching and martensite formation in comparison
to slower cooling as a function of the carbon content. Of course, it is only valid for the thin parts that could form
martensite.

The two extremes for carbon steel.
Extreme hardness can be obtained by martensite
formation (plus some retained austenite) uponquenching. Cooling the mix slowly produces largegrained soft ferrite plus pearlite. Tempering after
quenching produces something in between.
With martensite hardening we go way beyond of what could be done with all the other hardening mechanism. The
stuff is harder than cementite, glass or granite! It is also perfectly brittle like glass or granite; the first law of economics
is still enforced.
That explains why in the figure above the Vickers hardness was measured and not the yield stress. You can'tmeasure a yield stress if the material never yields but just fractures.
The yield stress numbers were just estimated from the table I gave you long ago so you can compare (approximate)
numbers.
That leaves us with a little puzzle. Put a glass edge on a otherwise simple sword and it is just as good as a truekatana? Maybe—but how are you going to do that?
The great thing about hard but brittle martensite is that it is still nothing but iron and a little bit of carbon. We canmake it directly from the steel we use, produce it exactly where we want it, as hard as we want, and attached to therest as well as could be. Try that with some steel and some glass!
Doing It
Understanding the theory of martensite formation is not an easy undertaking, even so you can enjoy the comfort of youreasy chair and your favorite beverage while trying to do so. Hardening a real piece of steel by quenching it in yoursmithy is not an easy undertaking either, even if you quench your thirst with all the beer necessary for that. Fortunately
you, the ancient smith (and the modern one) can do that without the need to go through the easy chair ordeal first.
You do not need to know anything about martensite and what happens inside your steel during quenching. You justneed to follow some working recipe. Smiths have quenched steel for the last 2000+ years without knowing a thing about
the theory behind it. They made babies the same way.
All smiths knew, however, that quench-hardening is a tricky process that did not always work, for reasons unknown.
Baby-making is not all that tricky in comparison but doesn't always work either for unknown reasons until recently. This
does not imply that there weren't all kinds of theories around that sought to explain those deficiencies (not enoughpraying, praying to the wrong / Goddess, moon too full, evil eye, witches, ...), it only implies that all those theories wereutterly wrong.
What could go wrong with quenching? Let's make a list:
1. Your sword might come out straight and in one piece from the quenching bath but has not hardened.
2. Your sword comes out nicely hardened in parts but not everywhere. Chances are that it is also bend.
3.
Iron, Steel and Swords script - Page 222

1.
2.
3. Your sword fractures and comes out in pieces that are possibly nicely hardened.
There is more that can go wrong. Maybe 95 % of your blade are perfect but there is an ugly hard blotch somewhere on
the blade where it shouldn't be.
This is rather upsetting because quench-hardening is done after a lot of masterly
work has already been invested in the blade. That all comes to naught if quench
hardening fails since you usually cannot repair what went wrong. It is therefore
small wonder that a lot of mystery and magic developed around quench hardening.
Since quenching did chance the properties of the steel a lot, and since it is hard toconceive that the "nature" of the steel has changed a lot, it was reasonable if wrong
to assume that the quenching fluid imparted something crucial to the steel. It isthus small wonder that humankind came up with all kinds of (mostly disgusting)recipes for quenching fluids. The link gives a taste treat.

SpecialLink
Quenching
Magic

The Module in the link also shows that nobody ever quenched asword blade by running it through a living body!
In hindsight and armed with materials science insights is is easy to understand why things could go wrong during
quenching. Here is a list that elucidates what could cause "bad quenches" and which factors play a major role:
1. There is no hardening if there wasn't enough carbon in the outer parts that cool fast enough for martensite
formation. You will produce "martensite", yes, but it is not hard because it is simple ferrite.
2. There is no hardening if your starting temperature was too low. Only austenite will transform to martensite andthat means that your blade must be above the transformation temperature of 727 oC (1341 oF) when it hits thequenching fluid. And it must be at high temperature long enough to allow all carbon to dissolve.
3. There is some hardening but not enough. You might have taken out the blade too early, performing a "slack
quench " (see below)
4. There is no hardening if your steel contained a lot of carbon, like crucible steel. Quench harden a wootz blade
and what happens is that it will not get harder but is now perfectly brittle and useless because the (primary)cementite is now lining the grain boundaries.
5. Local bending or warping happens if martensite forms inhomogeneously, i.e. only in parts of the blade or indifferent amounts. That might be due to an inhomogeneous temperature distribution (e.g. parts of the blade were
too cold) or inhomogeneous carbon distribution. If you have other inhomogeneities, e.g. phosphorous-rich parts or
non-uniform slag inclusions. local stress inhomogeneities during cooling could result that induce warpage.
6. Any cooling produces stress in the sample; rapid cooling produces more stress than slow cooling. Fracture
happens if this thermal stress" exceeds a certain limit somewhere. Fracture can be avoided if stresses are kept
low or if plastic deformation occurs before fracture. Your blade will then be bent but not broken. This may be thereason why a soft core is good for single-edged blades like katanas
7. Straight double-edged blades with a symmetrical cross-section are easier to quench than single-edged bladessince the unavoidable stresses on the front and backside or on the two edges tend to cancel each other. That is
not the case for a katana, for example, where the thin edge cools far more rapidly than the thick back that is also
thermally isolated by the layer of clay applied to all but the edge region.
There you have, in a nutshell, what you need for successful quenching. Note that
two independent factors come together:
Martensite formation. Required is the right (medium) amount of carbon
and the right fast cooling rate. Other "dirt" like phosphorous or slag
inclusions, while typically not good, can be tolerated up to a point.
Thermal and structural stress. Any phase transformation (like austenite ⇒martensite) causes structural stress, and any temperature difference (likebetween the outside and inside during quenching) causes thermal stress.
The two stresses add up. Stress causes first elastic deformation and thenplastic deformation and fracture. Note that thermal stress disappears
completely as soon as the temperature is the same everywhere.

Iron, Steel and Swords script - Page 223

ScieneLink
ThermalstressMartensite formation and thermal stress are interlinked in a complex way. Martensite formation is a phase changethat causes stress, and it only happens when there is a large cooling rate that unavoidably also produces large
thermal stress. How the to stresses add up is not easy to guess, nor what will happen. In essence, however, you
might get one of the following four general cases:
1. The combined stress causes essentially only elastic deformation. Then your symmetric blade emerges fromthe quenching bath in the same shape it went in. There might still be stress in the martensite containingedge regions but they tend to cancel each other. An asymmetric blade with martensite on one edge only
might be somewhat curved.
2. The combined stress causes some plastic deformation in some areas besides the always present elastic
deformation. Your blade then bends and stays bend even after the stress has gone or, as one says, hasrelaxed. But this bending is going the right way and you now have an elegantly curved sword blade, e.g. akatana.
3. As above, except that the plastic deformation is not going the "right" way, You now have a warped ugly
blade.
4. The combined stress exceeds the fractures stress somewhere and you end up with two or more parts. Not
good.
Yes, quenching is complicated. If you want to dig a bit deeper, you need to consult the thermal stress module . I
tried to make it very clear and easy to follow.
I have said quite a lot about the art of quenching but never even mentioned the quenching fluid, the magic andmysterious substance our ancestors considered to be of overreaching importance.
Well, they were wrong. Very much so. The quenching fluid has only one function: to establish the cooling speed. It cando that in three ways:
1. Its temperature. Guess under what circumstances a hot potato will cool down faster: If you throw it into hot orcold water? No more needs to be said.
2. Of course, if you pitch a big hot potato into a little bit of cold water you are cheating. So you need to supply
enough coolant. Pissing on your blade will not be enough.
3. The same amount of liquid at the same temperature has one more distinguishing factor: its thermal conductivity ;how fast the liquid can transport heat from the hot to the cold site. That depends on what it is and if it isvigorously agitated, streaming or just sitting there. The development of gas bubbles also has some influence on
quenching speed.
That's it. There is no transference of some "magical" stuff from your liquid to the steel, except perhaps a marginalamount of carbon or nitrogen for a few nanometers below the surface. And you don't need that because you already haveplenty of carbon in your steel - otherwise quenching makes no sense in the first place.
However, various dirt in your liquid might react with the surface of the blade to produce ugly spots (or to prevent this). So
it really doesn't matter from which river you took your water as long as it isn't too dirty.
It was the famous French scientist Réaumur who figured that out and did away with 1000 years of disgustingsuperstition. Here is an illustration to that.
Water is a pretty good quenching fluid and circulated water is more effective than still water, of course. Circulated oil
is more effective than still oil but less effective than still water. All the disgusting stuff is in between.
More than that one does not need to know about quenching fluids.
Tempering and Slack Quenching
Let's say you did properly quench a medium carbon steel. The outside of your pieces of steel, down to a depth of amillimeter cooled down fast enough to enforce martensite formation and is now very hard. And very brittle. Maybe toobrittle for the use you have in mind. What can you do about that?
In essence, you have two options:
1. Temper your steel. Anneal it a the right temperature for the right time, e.g. 30 minute at 400 oC (752 oF). Somemartensite will shrink. producing bainite. The hardness decreases somewhat but the ductility increases. I havecovered that already up there.
2. Change your quenching conditions next time you go about it. Either cool more slowly by using a different
quenching fluid, or stop immersion before the piece has completely cooled down

Iron, Steel and Swords script - Page 224

2.
In the first case you form less martensite and more bainite instead. Depending on the details of what you want toquench-harden, some particular quenching fluid then is "just right". That might be one of the reasons why theobsession of the smiths of old with various strange quenching fluids was not just superstition. One of those brews
might have had just the right thermal conductivity for your work.
In the second case, known as slack quenching, the outside cools down rapidly to ambient temperature and forms
martensite. But you take the piece out while the inside is still hot. That will heat up the outside again, tempering
the structure there to some exent. In effect you sacrifice some hardness for improved ductility. What you will get
depends, of course, on many parameters like starting temperature, nature an amount of quenching fluid, agitation of
fluid or blade, time in the fluid, geometry of blade, thermal isolation like a clay coat on parts of the blade, .... Youmight make it even more complicated by taking the blade out after some quenching time but re-inserting it aftersome other time.
Smiths without benefit of a material scientist are likely to consider slack quenching as something powerful but
erratic that only works on good days and if all the required magic and prayers are properly done. Consult the TTT
science module if you want to know (far) more.

1)

According to James Joyce in Finnegans Wake, p. 465:"... Be bloddysibby. Be irish. Be inish. Be offala. Be hamlet. Be the property plot. Be Yorick and Lankystare. Be cool. Be
mackinamucks of yourselves. ..."

Iron, Steel and Swords script - Page 225

8.4.2 Multiculti in SteelThe Melting Pot - What Goes in and What Comes Out"Multikulti" was and is a big word in Germany, it stands for "multi-cultural society"". Multiculti is achieved by mixing
Germans, Turks, Africans and so on with their respective cultural traditions and habits, and it was supposed to bring out
the best of all involved. Ha!
Multiculti, if you take it with a grain of salt, was and still is a good thing. It has substantially increased the quality offood in Germany, the singers in the opera are much better (and far easier on the eyes) - and just look at the nationalsoccer team in 2010; not to mention 2014! However, there are also undeniable problems.
Nowadays the political viewpoint is a bit more differentiated. It became clear that if you just throw some minority
culture into the German mainstream without any control of what is going one, the result might not be the perfectalloy you had in mind. What you will get depends on how you treat the various cultures that you try to alloy withGerman mainstream, and how they interact with each other.
Let's look at multiculti more scientifically and less sociologically. The result of what comes out of a "melting pot"
as multiculti was called earlier, does not depend so much on what some anonymous "one" does with the mix but on
how it self-organizes under the prevalent conditions. The Americans coined the term "melting pot" for people as an
obvious analogy to the making of metal alloys. A sociological melting pot is supposed to make good Americans, a
metal melting pot should produce good steel. Neither process is easy but all things considered, steel making is far
more more complicated than the making of an American; the latter enterprise might be more fun, though.
We are alloying mainstream iron with minority carbon and several more minority elements in real steel. What you finally
get will depend on the conditions for self-organizing. I have already shown you many different outcomes of a "meltingpot" steel experiment. let's recall some:
What you could get for some simply low-alloy carbon steel is a wild mix of primary and secondary ferrite, retained
austenite, primary and secondary cementite, more or less well-defined pearlite and to top it off, some martensite.
This are the phases and pseudo-phases you might find.
In the phases we have interstitially dissolved carbon atoms, other dissolved elements, dislocations, grainboundaries, phase boundaries, and precipitates other then cementite of all kinds, sizes and shapes.
In addition there is stuff like "bainite" that I kept from you so far.
The self-organized mess you will eventually end up with at room temperature might be good or problematic for yourapplications. What it will be depends on the mix you started with and the conditions you provided.
So far we only scratched the surface of steel science and technology - and we didn't even make a deep impression! If
you found this fascinating enough and really want to go a lot further, you should become a material scientist in generaland a steel expert in particular. That means studying full time for 3 - 5 years plus spending some time in a smithy or
steel mill. If you only want to go a bit further, read on.
Coming Out of the Closet
I will only look at a few more basic things in this backbone of the hyperscript:

What happens for carbon steel in between the two extremes weglanced at:
Cooling v e r y s l o w l y - Cooling very fast
Cooling very slowly yields well-developed pearlite + ferrite or pearlite + cementite by civilian processes(everything diffuses around at random).
Cooling very quickly yields a lot of martensite by military processes (all atoms move simultaneously in lockstep) plus some other stuff.
What happens in between? Well, everything you can imagine—and more.
Increasing your cooling rate first forces the crystal to do the necessary transformation at a finer and finer scale,making the distances that atoms have to cover by civilian processes smaller and smaller.
In other words: Cooling very slowly will eventually cause some pearlite to nucleate at some grain boundary corner.
From this corner a pearlite-austenite front will develop that moves leisurely across the whole grain.
If things now need to happen faster because you are cooling somewhat faster, the crystal starts pearlite in moreplaces inside a grain and moves the pearlite-austenite phase boundary more quickly. The structure then becomes
finer.
This is shown schematically below. If time is even more pressing, cementite starts to precipitate all over the place,and not in a nice orderly pearlite or zebra-pattern fashion (not shown here; you can imagine this. If not, look up the"divorced eutectoid transformation").
Iron, Steel and Swords script - Page 226

Cool real fast (or quench, in other words) and you have mostly martensite.

Slow cooling rate
Relatively long diffusion
paths' are possible,

Pearlite grows from few
nuclei and spreads acrossthe grain

Medium high coolingrate
Diffusion happens as
before but on a smallerscale,

Pearlite grows from several
nuclei; a grain may containseveral independent pearlite
regions

Pearlite formation in eutectoid steel for slow andmedium cooling rate
If you look at the old picture of pearlite in eutectoid steel, you see that it is closer to the slow cooling case. You
also see that even under ideal conditions, reality is far messier than can be shown in two-dimensional schematic
drawings.
In between cooling slow and cooling real fast is a region where things can get really messy. I need to trot out a few morechimeras (monstrous creatures composed of the parts of other animals) that so far I kept hidden in the closet:

In between halfway decent pearlite andfully developed martensite
you find "bainite".
The name "bainite" honors E. C. Bain , a well-known steel scientist.
There are lots of people out there who will take offense at my grave oversimplification of Bain's work but trust me: you
don't want to know much more than what I state here.
Bainite is not a nice clean phase like ferrite, austenite, or cementite. It is neither a well-defined but metastable phaselike martensite. It isn't even a pseudo phase like pearlite that at least can be represented in a phase diagram. It is a
mix of all of the above and might at best be called a chimeraphase (Chimera=mythical creature composed of the parts ofthree animals: a lion, a serpent and a goat). However, a lot of people and books talk about "bainite" the same way theytalk about martensite, pearlite or ferrite. That's not really correct but so what. Let's look at an analogy:
Take a perfect male (like me) to symbolize a perfect single phase like hard cementite
close to nirvana (and therefore single-crystalline). Take a bunch of male students toembody a less perfect polycrystalline phase of cementite, and a bunch of female
students as (yielding and soft) ferrite. What you find in an old-fashioned class room(boys on the left, girls on the right) then would be pearlite. Not a real clean phase but awell-defined mix of two real phases. Martensite would correspond to teenagers, neither
here nor there, just a transitory phase on the way to adulthood. Austenite corresponds
to kids; capable to change into adults of either sex.
Bainite then could be represented by people in a zoo. You get a mix of everything fromabove including, maybe, some apes (hard to tell from humans without a good
Iron, Steel and Swords script - Page 227

ScienceModuleBainitemicroscope).
At best you could call this mess a a chimeraphase - but nobody uses that word. You just call it bainite or, being a
bit more discerning, "upper" or "lower" bainite, hoping that the other person knows what you mean even so you
might not be too sure about that yourself. Use the science link if you want to know more.
It's simply that a lot of terms and names around iron and steel are from times when it was not quite clear what one
was naming. A proper scientific name for bainite was "dark etching acicular aggregates" (=longish things appearing
dark in a microscope)" since essentially you couldn't see all that much even at the highest available magnification.
Naming this more or less invisible stuff "bainite" was not very scientific perhaps but made you feel much better
psychologically. You might not have had the true name of the thing but at least you had some name.
Often those names are still around and are used today, even so they are not completely correct anymore. Let's justresign ourselves to the fact that that all these names are used a bit indiscriminately. Some refer to phases , someto structures, and nobody cares.
So what does bainite look like? I'll give you two pictures here. If you want to know more, you better consult thescience link. It is simply not sensible to discuss bainite in simple terms only.

From (small distance) pearlite to bainite schematicallyTime progresses from left to right.
Yellow: austenite grain, blue: ferrite, red: cementite
and "carbon cloud".

Bainite as seen in a transmission electron
microscope
Source: Wikipedia; from J. Horton; Oak Ridge National
Laboratory, Materials Joining and NDE Group

Now to the last last new structure I need to mention: Widmannstätten ferrite . The name tells it all: It's a phase(ferrite) with a special structure.
You get Widmannstätten structures, for example, if hypoeutectoid plain carbon steel iscooled down rapidly from a very high temperature well above the A3 temperature. That is thetemperatures where the pure γ-phase (austenite) starts to transform into primary ferrite andaustenite. This is called "overheating" and makes sure that you have large austenite grains.
If there is little time for the transformation because cooling is fast, ferrite crystals will
nucleate all over the grain boundaries and, since the grains are so big, also in the grain.
They quickly grow into some preferred crystal direction inside the grain and thus become
Iron, Steel and Swords script - Page 228

ScienceModuleWidmannstätten Ferrite

"longish". That simply means that you get ferrite needles ("acicular growth", lathes) or plates
that tend to be aligned along the same direction within one grain.
Do it with hypereutectoid steel and you get cementite needles; look up the science module for details. Here is a
picture of Widmannstätten ferrite in hypoeutectoid steel as is comes out of a bloomery:Widmannstätten ferrite in bloomery steel
Source: Reports of the Rockbridge Bloomery: Smelting
Enriched Bog Ore in a Low Shaft Bloomery; Jonathan
Thornton, Skip Williams and Aaron Shugar; no date.

You should now slowly and reluctantly realize, I hope, that the iron-carbon phase diagram, our reliable guide or map
through the labyrinth of iron-carbon alloys close to nirvana (now called "equilibrium"), is no longer of much use. The moreinteresting iron-carbon alloys known as "hard" steel, have microstructures that are far away from equilibrium. Of prime
importance for what we will get in the end is not only the carbon concentration but also the "thermal history", the way
the material was treated with "temperature". The "mechanical" history, the way the material was exposed todeformations by banging, rolling and so on, is also of some importance - but let's take one step at a time.
What we would need now is a new kind of map that tells us where we will end up if we the go down the fast, the slow, or
the meandering road while cooling our steel.
Such a map exists. It is called a "Time - Temperature - Transformation diagram" or
TTT diagram for short. You draw in how you are going to move from high to lowtemperatures, and the TTT diagram tells you what you will end up with.
Of course, exactly what you get does not only depend on the temperature profile as wecall that road from now on, but also on the carbon concentration, not to mention thepresence of other impurities. What I'm trying to tell you is that TTT diagrams just need to
be a bit more complex than mere phase diagrams. Here is the probably most simple
example of a TTT diagram for a medium carbon steel:

TTT diagram for simple carbon steel and"natural" cooling.

Iron, Steel and Swords script - Page 229

Science Link´

TTT Diagram

The yellow curves show steady cooling at wildly different rates. It takes about 5 seconds, 5 minutes, or more than aweek to get down to room temperature. In other words: the first curve embodies hard quenching by immersion in acold liquid, the second one air cooling with maybe some blowing, the last one letting your steel cool down inside alarge furnace that takes a week to get cold. The microstructure going with these curves are defined by the areas thecurves run through.
I only show a TTT diagram here to make clear that you now must make a decision: Either you decide you want toknow more, then you need to spend some time with the advanced module. Or you decide that this is all or possibly
more than you ever wanted to know about the topic, then you can just read on. There is no middle road in this case.
If you do a complicated thing like cooling your steel in a defined way to 800 oC, keeping it there for 30 min,quenching it to room temperature followed by tempering for 20 min at 300 oC, the TTT diagram will have to becomplicated. I can't change that, sorry.
I'm sure you can imagine a lot of cooling strategies or temperature profiles. And you can be sure that some smith
somewhere and sometime has tried it already, provided it can be done without too much fancy equipment. Alas - it isvery likely that mostly he produced junk or mediocre blades. But on occasion a magical sword might have come outby happenstance.
Now you know why. There are just so many parameters that influence the final result. Deviating from someestablished standard process that you learned from your master will most likely not be good. The probability thatyou produce one of the many kinds of inferior steel is simply much larger than that you end up with something new
and marvellous.

Iron, Steel and Swords script - Page 230

8.4.3 Feeling Stressed?
We are now almost done with the easy stuff. We only need to look at one last thing that happens when we cool downsome steel:

Cooling down produces a lot ofstress in the steel.

What does that mean? Imagine some small volume somewhere inside your blade. If there is stress acting on thatlittle piece of your steel, it means that mechanical forces are acting on it; pushing, pulling or shearing, trying tochange its shape.
Why should there be stress during cooling? There are two main reasons:
1. The different phases of steel have different specific volumes. That's a general and well-known thing. The
liquid phase of any metal always occupies a larger volume than the solid phase, so why should austenite andferrite occupy the same volume for the same number of iron atoms involved?
When the phase changes from ferrite to austenite or vice verse, the concomitant volume changes will simply
generate phase change stress.
2. The inside always cools down more slowly than the outside. In other words: different parts of your blade havedifferent temperatures during cooling. We say there is a temperature gradient. When things get hotter,
their volume expands; we named that thermal expansion. When things get colder, their volume must shrink
accordingly. During cooling the outside is always colder then the inside and thus has shrunken more thanthe hot inside part. The cold outside then presses on the inside like a vice trying to compress it, the hot
inside tries to pull the dole outside apart. In other words: During cooling your blade (or microchip) will
experience compressive stress in the inside and tensile stress on the outside. The faster you cool, the bigger
the temperature gradients, the bigger the temperature gradient stress.
So there is unavoidable stress during cooling down. What does it mean? You should be able to answer that question
yourself. The answer is:
Look at the stress -strain diagram for the kind of steel you have!
If the yield strength is surpassed locally, the steel will deform plastically, generating a lot of dislocations in theprocess. Too much stress and it will simply fracture. You get more local stress if you cool down quickly, of course.
The effects for you, the ancient smith, are clear. Upon (fast) cooling your steel or blade may:
Bend, i.e. deform plastically. Only if the unavoidable plastic deformation is exactly symmetrical (the left partwants to bend to the left, the right part to the right; the effects then cancel if they are of equal but opposite
strength), you won't notice that.
Katanas do bend during quenching, If you did everything right, they bend the way you like.
Shatter, i.e. fracture into two or more pieces. Not good for blade making but good for testing the steel you
have.
Fracture only internally . In other words, you have cracks crisscrossing the steel, but the whole thing still
sticks together. If those cracks are only in the inside where you can't see them, you are now about toproduce an inferior blade that probably will kill its owner in a fight because it breaks on heavy impact.
You realize, of course, that the occurrence of stress during cooling is not limited toiron and steel. The reasons given for thermal stress are extremely general; thesecond one applies to any material. Cool a brittle material like glass too fast and it
will not only fracture, it will explode. Cool silicon too fast and it either fractures or,
as long as the average temperature is still high, it deforms plastically. In bothcases the silicon is now worthless for the product you had in mind.

Science Link
ThermalstressThe End is Near!
At this point we are completely done with the easy stuff. I will now move on to the tricky stuff, hoping that you see thatas a promise and not as a threat.
The first step in doing this is to admit that:

Iron, Steel and Swords script - Page 231

There is no such thing as
plain carbon steel!

If you believe that some piece of steel is plain carbon steel, you are wrong.
You always have some "dirt" or impurities in your "plain" carbon steel besides the alloying element carbon. Sinceeven minute amounts (like 0,001 %) of something might make a big difference to what you get when forging a sword
blade, you just have to live with some uncertainty. Mostly, however, small amounts of impurities are not a big
problem.
Then it might be far worse. Unbeknownst to you, the ancient smith, you may not have (dirty) carbon steel but
something quite different: phosphorous steel. A lot of old sword blades in (northern) Europe were actually made from
phosphorous steel and not from carbon steel. Or from phosphorous, arsenic and carbon steel. This opens a whole
new can of worms and I will have to get back to this later.
You, the ancient smith, didn't know anything about that. You just left us with blades of breathtaking complexity andbeauty. Nobody knows your name anymore.
The ancient famous philosophers knew just as little as you, the smith, about iron, steel or most everything else fromthe world of materials. But in contrast to you, they didn't make anything but just thought about it and then wrote
down their guesses and opinions (mostly wrong) in excessive length. Their names are still known and revered bysome.
So I want you, the reader, to do the following:

Next time you look at an ancient blade
from some unknown smith or a copyof an old book from, say, Aristotle,
consider who did more for thedevelopment of mankind.

It's time for a getting-philosophical-break during which we consider this thesis (or theorem?): E Pluribus Unum.
In particular, I want you to give some thought also to the antithesis. Even if Latin is Greek to you, the sentence should
be vaguely familiar to you if you happen to live in the USA1).
(Hint: It's easier to have deep thoughts while taking deep drafts from a suitable beverage. With luck, you won't evenremember your deep thoughts on the next day).

Iron, Steel and Swords script - Page 232

A beak, wings, two feet - and look how many birds you get, including some that are not even flying around out there.
Iron atoms and carbon atoms - and look how many steels you get!
Actually, if you did your contemplating right, you realized that there are far more birds in the picture, not to mention
out there, than the species of carbon steel I have mentioned so far.
To answer your implicit question: Yes - I did keep a few more things concerning carbon steel from you. Besides the"bainite" and Widmanstätten ferrite " alluded to not that long ago, we have a lot of stuff that goes under headings
like "cast-iron", with a subculture of its own, distinguishing, for example, between "white" and "gray" cast iron. We
have phases called ledeburite (after Adolf Ledebur; 1837-1916) or graphite, and so on.
There are also strange new animals like stacking faults, split dislocations, partial dislocations . grainboundary dislocations that live inside the phases—you get the drift. There are more birds and interesting parts ofbirds, indeed, and I could go on for a while, elaborating carbon steel.

Surprise!

Even if you are eager to go on, I give up - as far as the Backbone isconcerned
If you don't want to give up,
switch to the Science partI will now simply go on to the next chapter entitled "Real Steel" and move from mere birds to all animals, including
beloved ones like cats and dogs but also slimeworms and university administrators.
In the case of animals, this needs more ingredients than just beaks, wings and clawed feet (e.g. tails, slime and being
narrow minded). In the case of steel, we will now add more than one alloying element.
If the resulting structure at room temperature is good or problematic for the applications you had in mind will depend on
the mix you started with and the conditions you provided.
So far, we only scratched the surface of steel science and technology. If you really want to go a lot farther, you
should become a material scientist in general and a steel expert in particular. That means studying full time for only
5 - 7 years plus spending some time in a smithy or steel mill.
If you only want to go a bit farther, check the "Science" and "Miscellaneous" modules.
Why do I forsake you at this point? Because it just doesn't make much sense to introduce and discuss things like TTTdiagrams without equations. Not that I couldn't do that, I just don't feel like it.
I promise, however, to keep those science modules relatively simple. So if you want to give it a shot, here are all thelinks.

1)

ScienceModuleScienceModuleScienceModules

ScienceModuleBainiteWidmannstätten

TTT
Diagrams

Thermalstress

E pluribus unum is Latin and translates as "Out of many, one" or "One from many". The antithesis would be: Manyfrom one, e.g. many kinds of steel out of one (or few) ingredients or an universe with all its many manifestations outof one equation.
E pluribus unum is the phrase found on the Seal of the United States, along with "Annuit cœptis" (He [God] hasfavored our undertakings) and "Novus ordo seclorum" (New Order of the Ages) on the backside, together with thetruncated pyramid with the Eye on top.
E pluribus unum was considered a de facto motto of the United States until 1956 when the United States Congress
passed an act adopting "In God We Trust" as the official motto but leaving open which God.

Iron, Steel and Swords script - Page 233

9. Real Steel
9.1 Some General Remarks
9.1.1 Things Get Complicated9.1.2 Problems with Alloying

9.2 Low Alloy Steels
9.2.1 A Closer Look at Low Alloy Steels
9.2.2 Designing Low Alloy Steels

9.3 High Alloy steels
9.3.1 Stainless Steel
9.3.2 Maraging Steel

9.4 Phosphorous Steel
9.4.1 Phosphorous Steel - an Orderly Introduction
9.4.2 Phosphorous Steel - a Chaotic Succession

9.5 Cast-Iron
9.5.1 General Remarks
9.5.2 Kinds of Cast Iron

Iron, Steel and Swords script - Page 234

9. Real Steel
9.1 Some General Remarks

9.1.1 Things Get ComplicatedProperties and Microstructure Reconsidered
So far I have mostly looked at an ideal iron - carbon alloy, called plain carbon steel, with just an occasional glance ofwhat else might be in there. This is not realistic. In ancient steel, there is always something else in there - essentiallythe more prominent elements of the periodic table in some form or other and inclusions of slag particles, charcoal,"pebbles", and whatever else was around. Whatever is in there got inside by circumstances and certainly not byintention. Aristotle, after all, had proclaimed that steel is especially pure iron, so why should you add something?
Even if you, the ancient smith who had fortunately never heard of Aristotle, dunked your red-hot iron in all kinds ofrevolting stuff including goose shit, you didn't do it in order to get some element inside the steel crystal lattice. You
believed in the working of some magic that somehow relates to goose shit or whatever, or you simply did it because
somebody (your master) had told you that this is what one does. Just think of all the revolting stuff people eat justbecause somebody (typically parents) told them that this is what one does, and you see how powerful tradition can be.
My wife (from NYC), for example, eats slime that's is still alive! inside some closed (for good reasons!) nacre shell!
Times have changed. When we make modern steel, we add all kinds of alloying elements intentionally. But mostly wealso have some stuff in there that we do not care about. The only question is if we know that some unintentional stuff isin there, and how we make sure that we can tolerate it. We need to distinguish a bit more closely between the various
things our iron / steel might contain and define a few terms:
Alloying elements are there because we added them intentionally.
Dirt atoms in concentrations around 0.x % are there because they happened to be around in one of theprocesses involved in making the steel. We don't want them but we know they are there. We tolerate a certain
amount of dirt - especially sulfur (S) - because it costs money to make really clean iron and steel. You do it,
however, if you must.
Trace elements are always unintentionally in there. Their concentrations is low - some ppm to below thedetection limit - and we typically neither know nor care about that.
Inclusions, in contrast to atoms, are pieces of something (slag, charcoal, tiny stones, ...) that somehow made it
inside your steel. Inclusions are much larger than atoms and in most of steel history were simply part of yoursolid raw iron / steel. They are always there if your steel was never liquid. This was a huge problem for ancient
steel makers and it is still a (small) problem today. The Celtic iron from the 5th - 1st century BC shown below,
while possibly rather pure, is sure to be full of slag and charcoal inclusions.

Celtic "trade" iron from Pleidelsheim, Germany
Source: Special exhibition dedicated to the Celts of the firstmillennium BC "Baden-Württemberg State Museum ofArchaeology" and the "Württemberg State Museum", 2012/13,
Stuttgart, Germany

Iron, Steel and Swords script - Page 235

The periodic table contains about 90 elements that you can find out there, if mostly in disguise, i.e. tied up in somecompound. You can also just buy most of them, something that is much easier to do. Some elements are very rare andthus not likely to be unintentionally incorporated in your steel. That is one reason why many of those 90 elements are
only found in very low concentrations in your steel, ppm or much lower. You need sophisticated equipment to detectthem.
It is very likely that a very low concentration of something does not influence the properties of your steel very much - but
you never know for sure. Boron (B), for example, will be felt at concentrations as low as 0.0003 % (3 ppm).
But many elements are ubiquitous enough and thus might make it into your steel. Assuming that we always havesome carbon around, we have, expanding on the above a bit, the following basic possibilities:
1. The element in question is present in a extremely low concentration, say below 10 ppm or 0.001 at%. You
need sophisticated equipment to detect it. It is very likely that it causes no problems and no benefits since itdoes not noticeably influence the properties of your steel. However, you never can be quite sure as long as
you didn't look into it. 1)
2. The element is present in what we call a low concentration - above 100 ppm or 0.01 at% and up to theusually 1 wt % or 2 wt%. It mostly causes you all kinds of problems but might be good in special
circumstance. Sulfur (S), phosphorus (P) or oxygen (O) comes to mind.
3. The element is present in low concentrations and is (almost) always good for you. Manganese (Mn) is theexample for this. We might have been lucky because some manganese is contained naturally or we added it
intentionally - for example in the case of "micro-alloyed steel".
4. The element is present in a low concentration and noticeable but mostly not doing all that much. Smallquantities of elements like nickel (Ni) or chromium (Cr) are in this category.
5. The element is present in a high concentration, from 1 % to above 10 %. Then it is (almost) always
intentionally in there and thus must be doing something beneficial.
Point 1 - 4 covers what is called low alloy steels, point 5 leads over to high alloy steels.
As you see, steel science is difficult. Very difficult. What we learn from all of the above is that just knowing theconcentration of some element doesn't tell you how it might change properties. And I'm meaning all relevant properties,
not just the basic "strength" stuff that I mostly discussed so far. And whatever it does in principle will very much dependon processing. And on what else is in there. And on the temperature and the environment.
Nowadays we may know the exact composition of a steel down to trace elements in the ppm or even ppb range - butthat does not tell us all that much about its properties. The properties, as you know by now, depend on the
microstructure, which depends on the compositions and the processing, or everything you or somebody else ever did toyour steel.
To make things even more complicated we must now also consider steels withoutcarbon or more properly, steels with very low carbon concentrations. The link willtell you far more about that than you ever wanted to know. These " designer steels"
are always modern steels and their number and market share is rapidly growing.
Don't mix that up with old-fashioned wrought iron . It is low in carbon, yes, - but it is
not steel!
You can already appreciate that with only a little carbon you cannot produce muchcementite. Hardness thus must come from something else. I will come to that.

Link Hub
Major Steels

Of course, over the last 150 years or so, when something akin to steel science was born and thrived, a lot of data
have been collected and refined into knowledge and rules. But that only helps to some extent, because there isalmost no rule without exception. Sulfur in steel is always bad? Yes, but there are some steels where sulfur (S) is
added intentionally because it makes machining easier. Even evil phosphorous is used in modern so-called"weathering steel" and some others. Another example is oxygen. It is decisive for making your steel. You blow it
through your molten raw stuff in order to take out you whatever you don't want, but you typically don't want it in thesolidified product 1).
So, once more, steel science and engineering is difficult. Very difficult. Thank God! It gives us scientists and engineers
something to do for making a living. If systems are very complex, then there is also a lot you can do.
Look at modern alloy steel; iron with alloy elements that we put in there intentionally . I, a modern steelmaking scientist
have an incredibly large selection of alloying elements and processes up my sleeve, from which I can choose. That's
why there are thousands of different iron alloys out there today, all of them we call "steel". And that's why there will bemany more to come, just wait. The parameter space involved is still largely unexplored. In contrast, you , the ancientsmith and steelmaker (almost the same thing) had only very limited options. Worse, you had not much leeway inexercising these options either.
Your first option was to choose among the few kinds of steel available two thousand or three thousand years ago.
1. You had essentially wrought iron or a mild carbon steel, always with some additional dirt in there. Your steel
was never liquid, so it always contained slag inclusions.
2. You had essentially a phosphorus (or arsenic) steel with some other dirt in there. Your steel was never liquid,
so it always contained slag inclusions.
3. You had essentially a carbon - phosphorus steel with some other dirt in there. Your steel was never liquid so
it always contained slag inclusions.
4.
Iron, Steel and Swords script - Page 236

3.
4. You had "wootz" steel that had been liquid once. It had a high ("hypereutectoid" ) concentration of carbon
and contained some dirt, but hardly any slag inclusions. Some wootz kinds also contained traces of strong
carbide formers like vanadium (V) that were not distributed homogeneously.
5. You had some weird stuff.
Your second option was how you processed your steel. Not much choice here either. Temperatures were restricted
and not precisely known, and thermal treatment consisted of natural cooling or some kind of quenching.
Your third option was which God you prayed and made sacrifices to. It might have helped your spiritual well being
but did very little towards improving your steel.
At this point you must become aware once more that what I have summarily called slag inclusions are objects of prime
importance for all ancient smiths making iron and steel objects including sword blades, from all steel other than wootz
steel. Inclusions are the major reason for all this folding and hammer-welding; I'll get to that.
But let's assume that we know that it is the microstructure, including slag inclusions, that determines the properties inthe end. Let's think about this for a minute. Do we (I include myself) really know how the properties of steel depend on
the microstructure?
Let's say we know the exact composition of a steel and its microstructure. Thatallows you and me (in principle) to make some educated comments or guesses
about its hardness and ductility, allright. But how about the following properties:
Weldability; the possibility to join two peaces by simple liquid or torch
welding without compromising mechanical strength at the weld seams?
Weldability is a very important property. If a steel cannot be welded, forget it
for the car industry.
Corrosion resistance, or how fast does it rust? Under normal conditions? In
salt water? I don't have to explain the importance of that property.

Illust. Link
Steel
Properties

Creep resistance. That doesn't mean that the steel resists to be being used by (insert creep of yourchoice). It means that it deforms plastically and v e r y s l o w l y under a stress that is far lower than theyield stress and thus shouldn't do anything. We are talking long term behavior here, a tricky business.
Fatigue resistance. Can steel (or any material) get tired and collapse? You bet! Fatigue happens if small
oscillating strains (vibrations in other words) occur long enough in your steel. I'm talking small stresses andstrains here once more, that should be well contained in the elastic region of the stress-strain diagram.
Accordingly, the microstructure should not change - but it does, leading eventually to fracture.
I have mentioned fatigue (and creep) before but now you know that these properties, like all properties, must
somehow be tied to the microstructure. In both cases the properties and thus the microstructure changed
under conditions where we wouldn't have expected that.
.....
The list would go on for at least 20 more points if we look seriously at all important properties. The link gives somemore examples.
Then you repeat most of the list but for some temperature other than room temperature. Is fatigue more pronounced
at high temperatures?
The answers to the many questions hinted at above must be hiding in the
microstructure. There simply is nothing else. My colleagues and I (mostly mycolleagues, to be honest) indeed do know a lot about how all these properties
depend on the composition and the microstructure. Not yet all there is to know, but
a lot. I give you a taste treat in two advanced modules about creep and fatigue .
I will not say much about corrosion - yet. It's too painful, see below. Not only for theowner of fine steel products but also for Materials Scientists. While we do know a
lot about corrosion, it's not nearly as much as we would like to know.

Different corrosion in parts of a pattern-weldedsword.
Source: Bundesanstalt für Materialforschung und -prüfung,
Berlin, Germany. Used with permission.

Iron, Steel and Swords script - Page 237

Advanced
Links
Creep
Fatigue

Some smith around - roughly - 500 AD made a complex pattern-welded sword from two kinds of steel. One of thesesteels was phosphoric steel (I'll get to that shortly), the other one carbon steel. Look at what you get after only amillennium and a half! The carbon steel is almost gone whereas the phosphoric steel was rather corrosion resistantunder the conditions encountered.
And that is even a well-preserved artifact. Most of those swords, originally looking like that, are now only a vague
orange colored spot in the earth.
Of course there are a lot of basic rules about properties and microstructure. Most of them were found empirically andexplained later, if at all. I will give you one important rule as example:

Pearlite is bad for weldability andcorrosion resistance. Martensite is worse.

Tough luck! Our main ingredients for increasing hardness cause severe problems regarding other properties. So weneed to do something about that by alloying the right elements besides carbon. That's essentially why we doextensive alloying. As far as only hardness is concerned, just working with (clean) iron and carbon would already doa good job.
The good news thus is: With proper alloying you can cure some problems of your steel.
However, there is still no such thing as a free lunch.
The bad news is: There is no super steel that gets only good grades with respect to all the 20 plus properties ofinterest to you when you consider a product. One size doesn't fit all.
To some extent this is clear. Super steels cannot exist because quite often some requirements on your list arecontradictions in terms. You just cannot have a steel that is easy to press into some shape (so it must have a low
yield stress) and very hard (requiring high yield stress) at the same time. It's just like demanding a round square,esoteric science or theo logy.
Good grades in all non-contradicting properties are not possible either; in particular if one of those properties iscalled "costs count", i.e. if the great cost issue raises its ugly head.
The message is clear: you must compromise! You might be looking all your life for that gorgeous person with a Noble
prize in physics, a lot of money, a friendly and honest disposition, and so on, but you are most likely better off tocompromise when looking for a partner (especially if you are a physicist).
You might be looking all your life for that supersteel either. Going for the best compromise is smarter.
That's why there are far more than 1000 types of steel out there that you can buy. In a few years from now there will
be even new types - steel science and engineering is still far away from having made everything that has some value
for somebody. Development of new steel types is more and more based on solid science including a lot ofcomputing. That does not preclude that on occasion some "tinker" comes up with a big surprise.
You realize of course that we are now deeply in non-crystalline organic waste, to say it politely. How do we make acatalogue listing that many types of steel in a systematic fashion? How do we categorize steels?
It's like categorizing the many different types of wine or living beings. "Red, white, rosé", or "animals, plants, fungus"
comes to mind and gives an easy start - and some trouble. Under which wine heading would you list champagne or"Schillerwein" a German specialty where you mix red and white grapes? Are viruses living beings and if so, whichheading covers them?
The real trouble, of course, starts after the first level of the system. The next level of listing wines, for example, may
contain identifiers like grape type (e.g. Lemberger, Pinot Noir, Zinfandel, Primitivo, ..) or region: Württemberg, Napa
valley, California, Bordeaux, Rioja, ...). It's not overly helpful. I bet you don't know what a Lemberger grape is (mypreferred variety) or that Zinfandel and Primitivo are just two different names (USA and Italy, resp.) for the same
grape. Giving the sugar content (or words for it like "dry" or semi-dry") and so on comes next, plus lots ofentertaining descriptions ("steely with a hint of flint"). And you know what: It doesn't tell you much about how somewine will agree with you if you don't have extensive prior experience with wines and the classification system.
Historically, wine was only categorized by its origin. The same is true for steel. Where it was made (or who made it)
told you how it was made and what kinds of properties and quality to expect. "Sheffield steel" or "Krupp Stahl" said
it all. Some areas or producers just produced better wine or steel than others, and nobody knew exactly why thiswas the case.
Categorizing steels is almost as bad as listing wines. I won't even attempt it here.
This Hyperscript, however, claims to encompass everything remotely interesting toswords, and that must include some way to classify steels. I therefore give you thebasics about categorizing steels in a basic module.
It is basic and not advanced because is contains absolutely nothing that is difficult.
It just is awful, illogical, wretched and complicated - even so no politicians andlawyers were involved.
Iron, Steel and Swords script - Page 238

Basic Link
Categorizing
steelGetting Closer to Real SteelIn a general and somewhat trivial way we distinguish between the unwanted evil impurities called dirt, and the wanted
good ones that we then call alloy elements. There are thus two reasons why you have foreign atoms in your iron or
steel:
1. They originate almost exclusively from making your steel and processing it without conscientiously adding
alloying elements.
What you find in your finished product then goes mostly back to what you filled into your smelter. The
concentration of some element in your steel may change during processing, quite a bit in fact, so what you havein the end depends on both variables.
2. They originate only to a small extent from making your steel and mostly by being deliberately introduced by you.
It is clear that this demands powerful real-time analytics. You must know at all times what is in your steel so you
can take out what needs to be taken out and insert the right quantities of what needs to be inserted. You alsoneed to know how to do this.
The first point, of course, relates to iron and steel making for the first 3.500 years or so, the second point to the way
we do it for the last 100 years or so.
I will get back to modern steel making, but for now let's look at the old-fashioned way. Both kinds of elements, thebadies and the goodies, then come almost exclusively from the ingredients used in the making of the steel, including
the ingredients used for optimizing slag. I'll get to slag in the fullness of time.
In ancient times you stuffed unclean ore and unclean charcoal into your smelting furnace. You had no choice, you
simply didn't know better. You might have had an idea that cleaner is better, though. Remember? All that was
known about the "theory" of steel is that Aristotle had proclaimed around 350 BC that steel was especially pureiron.
So you may even have treated your ore before you used it, removing some of the unwanted stuff, but nonethelessyour ingredients were never very clean. In our modern times we still stuff unclean ore and "coke" into our huge blast
furnaces. Not because we couldn't make clean ore and carbon but because it's impossible to get clean carbon andpure iron ores in huge quantities for very little money. Coke in this case means rather clean carbon and is not
something you drink or stuff up your nose. I'll get to coke in the fullness of time, too.
Whatever happens inside your blast furnace (and that's a rather complex story we are going to tackle in the next
chapter), you cannot reasonably expect that pure iron will come out. Nevertheless, our forebears did produce
admiringly clean wrought iron in their primitive "bloomery" furnaces. They could do that because they made very
clever use of the iron-carbon phase diagram - without having the slightest notion of what that might be. Their stuff
always contained slag inclusions, however.
By the way, the silicon (Si) production of today follows the same basic ideas we use for making iron. You throw dirty
silicon "ore" (actually silicon oxide or silica (SiO2), otherwise known as quartz sand) and dirty coal / coke into afurnace. You even add some more dirt in the form of (special) wood chips because that makes the product better - justlike the special plants put in the crucible when making wootz steel. The only difference to iron making is that you don't
set the mix on fire. You run some heavy electric current through it. It's necessary for some particular reason but theeffect is the same. Things get rather hot.
What you get is - surprise - dirty silicon. There is a lot of dirty silicon (also called "metallurgical grade silicon") madeevery year; well above one million metric tons. Most of this metallurgical grade silicon goes - you guessed it - into
steel or aluminum as alloying element. An amazingly large part is also used to make silicone , a polymer that has
many uses, some of them associated with outstanding properties of people like Pamela Anderson.
By the way (once more), you noted (I hope) that silicon, silicone, and silica are about as different as romanic,romantic, and Rome, or "Smelting", "melting" and "gelding". Unfortunately this is not always known to journalists,
translators or museum people.
A small part of the metallurgical grade silicon, about 25.000 tons per year or 2 % of the total, is converted to theultra-clean and quite expensive single-crystal silicon that ends up in computer chips, solar cells, or micromechanical devices like the "heart" of your beamer or the movement sensors in your i-phone.
Only a small part of the total iron / steel production of old ended up in a superior sword. The product then is expensive
and so on, but also demonstrates the top technology of the time. That's what motivated my (amateur) interest in swords,
remember?

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It also motivates my (professional)
interest in solar cells. While we canmake an enormous number ofcomputer chips from one ton of ultraclean silicon, one ton won't get us very
far if we want to make square miles ofsolar cells with silicon. That's why
there are large efforts under way tolearn how one could make good solar
cells with dirty

Attention! I'm
getting
fundamental;
veering
off the topic!

and cheap "metallurgical grade"silicon. It will be rather exciting for the
initiated to watch if the silicon guys
can do what the steel guys managed
to do 2000 years earlier by cunning,
and about 150 years ago by evolving
into Materials Scientists andEngineers. They either learned how tolive with dirt or how to remove it
cheaply.

I'm absolutely sure we will succeed with silicon, too. We are already at the "break even" point now (2012), i.e.
producing your electricity with solar cells cost just as much as in the old-fashioned way. That can be roughly
compared to the point in time when mass-produced steel had its "break-even" with the dominating cast iron. Just
wait an other 20 years and solar energy will be far cheaper than running power plants with coal, oil, or gas.
Yes, you are right - the sun doesn't shine at night; in my country quite frequently we do not even see her during
the day. I know that. All I have to say is: trust your scientists and engineers to find a solution. Don't trust yourbankers, oil companies, power plant owners and related politicians to find a solution. And keep the latter fromhassling the former.
In particular, do kick your economist in the rear when he tells you that the solution will be to write some numbers
on paper (called CO2 emission certificates). I guarantee that they will work just as well as the papers pronouncing
fledgling dot.com companies to be more valuable than, let's say, Mercedes; the papers that promised to yield far
more then 20 % a year by bundling mortgages yielding around 3 %; or the papers stating that Greece is a healthy
economy ready to join the euro. Not to forget, of course, all the papers stating that a crisis that resulted fromoverspending, can only be overcome by more overspending.
So trust my colleagues and me in particular. If it makes you feel better, you could send me large amounts ofmoney and I will send you a paper stating in many fancy words that the energy crisis and the financial crisis is
now over for you. Don't miss this opportunity! I will serve only the first 1000 applicants, the rest will have to livewith both crisis' forever after.

1)

Dianzhong Li, Xing-Qiu Chen, Paixian Fu, Xiaoping Ma, Hongwei Liu, Yun Chen, Yanfei Cao, Yikun Luan & Yiyi Li, in thearticle "Inclusion flotation-driven channel segregation in solidifying steels", published in: Nature Communications 5, Article
number: 5572 in Novemebr 2015, report the observation that "Channel segregation, which is featured by the strip-likeshape with compositional variation in cast materials due to density contrast-induced flow during solidification, frequently
causes the severe destruction of homogeneity and some fatal damage " is caused by oxygen precipitation and occurs foroxyen concentrations above 0.001 wt%. "This study uncovers the mystery of oxygen in steels, extends the classicalmacro-segregation theory and highlights a significant technological breakthrough to control macrosegregation" is claimedby the authors.

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9.1.2 Problems with Alloying
Setting the StageIn everyday life we use almost exclusively metal alloys and not pure metals because alloys are better. All alloys withiron are called steel a long as iron is the base metal with more than 50 wt% of the total. With copper (Cu) as basemetal, we use more names and call its alloys bronze or brass, for example. There are no generic names for aluminium
alloys, even so they are very important.
So alloying is good. Well, yes - but there are also problems. I shall start reminiscing a bit about the history of alloying
and go from there to point out some problems with alloying. Finally I will delve deeply into the joys of alloying
In writing this article I found it surprisingly hard to find data or good metallographic pictures for the ideal plain carbon
steels, i.e. steel with only carbon as alloying element. That's the kind of steel I have discussed in the preceding
chapters. There is a simple reason for that:

There was and is no such thing as
ideal plain carbon steel

There was and is no such thing as ideal plain carbon steel since nowadays we always add some other elements(typically manganese and silicon) , and in the old times you always had some stuff (often phosphorus) in the ironunintentionally.
Steel is iron with some alloying elements. That is a relatively recent insight. Looking back three millennia, we might
distinguish several steps on the way to understanding the steel alloy system we are dealing with here: iron plus a bit of
the rest of the periodic table. The times given below are approximate. They may vary between here and there, and there
is always considerable overlap.
1. 1.700 BC (?) - 1.500 AD: Iron was "invented". Smelting proceeded by a solid state process. The big trick forgetting steel was to have it as part of the bloom in the first place. This necessitate the ability to recognize and to
separate it from the wrought ion probably also there. You never made steel, as stated in much of the literature, by
employing a second process called "carburization" that inserted some carbon into the bulk of your wrought iron(or something else suitable like phosphorous (P)). In any case, your iron or steel was full of inclusions (except for
crucible steel). Where and when steel making differentiated itself from (wrought) iron making by optimizing
bloomery processes for either extreme is not all that clear, but around 500 BC there was some intentionallymade steel around. Of course, the steelmakers most likely did not have the faintest (correct) idea why whatever
they were doing actually "worked". If they had any ideas at all, we don't know about them because these guys
couldn't write, and nobody who could write would even dream of recording anything that he heard from mere
artisans / slaves.
But even without any clear understanding of what one was doing, iron and steel technology became incredibly
sophisticated during the 3000+ years we talk about here. Complex and beautiful pattern-welded swords andequally enticing wootz swords were produced.
2. 1.000 BC - 1.500 AD: Some people called philosophers thought about the "nature" of materials and wrote it
down. Most results of that thinking were utterly wrong. Small wonder. As long as you don't really know whatatoms and chemical elements are, you cannot possibly understand what is going on while making steel (orpeople). Some early guys had a few thoughts into the right directions but the prevailing view of guys like Aristotle
was utter nonsense.
3. 1400 - 1700: With the advent of the blast furnace steel making changed completely. Surplus carbon and otherstuff now needed to be taken out of the dirty cast-iron (called pig iron) that was produced from now on until today.
4. 1700 - 1830: It became clear that carbon is responsible for the hardness of steel in comparison to pure iron, andthat "chemistry" mattered in the sense that it was important what your steel contained or came into contact with.
It also became clear in the late 17th century what carbon is. Alloying with elements beside carbon happened too,
but more or less accidentally.
5. 1830 - 1900: The major breakthroughs in steel making occurred, tied to names like Austen, Bessemer, Thomas,
Siemens, and Martin. Steel production increased dramatically and so did the understanding of what is going on.
In 1897 Robert Austen describes the first iron - carbon phase diagram. Looking at the microstructure withmicroscopes and intentional alloying started.
6. 1900 - 1950: "Discovery" of atoms, statistical thermodynamics, and quantum theory. Based on this, the"discovery" of crystals, and crystal defects could follow. The ingredients for a thorough understanding were now
all there. Alloying was done consciously on a rapidly growing empirical and scientific base.
7. 1950 - Present: Modern analytical tools allow to find out the concentration of the elements in your steel, how
they interact and generate all kinds of microstructures, and how that relates to the properties observed. Alloying
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7.
is based on a deep understanding of what is going on and a huge data base. There are, however, still some open
question and occasional surprises.
8. 1990 to Present: Computer power started to allow "first principle" calculations about properties of real crystals.
The age of scientific steel (and other solids) has started. Its impact on steel technology, while still minor, isnevertheless felt and is sure to increase. Semiconductor science and technology is utterly impossible without
computers.
9. Present - 2050: Wait and see. There will be new and superior steels for sure.
Whatever is in your steel might have been put in intentionally or unintentionally. In a strict sense, putting specificelements intentionally into your steel did not start before, roughly 1850. Steel makers through the millennia, however,might have used certain ingredients (like leaves of some special plants in crucible steel making) for the same purpose.
What you had in your steel depended on what you used for making it, and trial and error lead to recipes that "worked" sometimes by alloying the right stuff by good luck.
Your forebears put (mostly) the right things into their personal systems, too. They did not eat certain mushrooms,
fruits and plants even so they had no idea about the biochemistry of toxins and had never heard of cholesterol orcalories. But they did not consume the really good stuff either (chocolate ice-cream, coffee, cognac, my wife's
gooseberry cake, .. ) because they lacked the ingredients and the know-how for making it. Try to make ice-creamwithout a freezer. It can be done but I bet you don't know how.
Most of the time your ancestors ate mediocre food that was easy to get. But they had very good food on occasion,using special and expensive ingredients and followed time-tried complex recipes.
In analogy, very good steel was produced sometimes and then used for swords or other high-value items. Most of
the time, however, the stuff was mediocre or bad.
Major Problem: Embrittlement
If we now look at whatever was in there intentionally or unintentionally, it either could be good or bad (and anything in
between). Sulfur (S) is practically always bad, manganese (Mn) is practically always good, and phosphorous (P) is
ambivalent. Of course, as with all medicine or spices, the dosage is important. The headline of this sub-chapter was"Low Alloy Steels", meaning that we look at low concentrations below at most a few percent.
If a given steel gets worse upon alloying it with something depends on how you define "worse". That depends on
your intended uses. Does a whisky get worse when you alloy it with soda?
A decreasing hardness, for example, might be bad for sword users but not for others. When you need to make achastity belt in a hurry, it's easier with not-so-hard steel. Since your wife doesn't appreciate a hard one any morethat a soft one, why bother and use hard steel?
Everybody agrees on one issue, however:Embrittlement of your steel is always bad!

If your steel undergoes a ductile-to-brittle transition (or transformation), you have a problem! It is such a well known
and big problem that it has its own abbreviation: DBT! If alloying induces a DBT transition, your steel is now perfectly
brittle and behaves essentially like glass. Not good. Neither for swords nor for chastity belts.
Phosphorous and sulfur are notorious for causing DBT behavior. They are also particular hard to keep out of (ancient)steel, so we now have one of the major problems with (typically unintentional) alloying in ancient and recent times:

Phosphorous is responsible for"cold shortness", and sulfur induces"red shortness" or "hot shortness".

The terms mean shortness, nowadays called brittleness , that occurs at low or high temperatures, respectively. I've
already introduced this in chapter 3.2, now we will go to the core of these really big problems in steel technologythat haunted steel makers and users up to about 1950.
To be perfectly clear: phosphorous (P) causes a DBT when the temperature drops below some critical temperature
TDBT, and sulfur causes a DBT if it gets above TDBT. Other alloy elements might also cause these effects.
Cold and hot shortness were two of the banes of steel throughout the millennia. Even today DBT causes major worries
for users and makers.
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Cold shortness is a major problem for you, the user. Just imagine that your steel turns brittle in the winter, when thetemperature is around freezing. Your sword will shatter into thousand parts on impact, your steel steamer will justbreak apart (that happened!; see below), and your chastity-belted wife only needs to sit in the snow for some time
and then look for that nice smith apprentice with his hammer. One little bang will do it (for starters).
In other words, cold shortness is bad for you if it occurs in the range of temperatures where regular humans live,
love, work, and do business. If cold shortness occurs at temperatures too low for regular humans, you can live with
it. However, if you, like me, belong to the irregular humans who, for example, keep liquid nitrogen (N) or helium (He)in steel containers at temperatures around -200 oC (-328 oF) or -270 oC (-454 oF), resp., you better watch out forwhat kind of steel is used!

Liberty Ships fractured because of cold
shortness around 1940

Hot shortness doesn't affect you, the user, all that much - except if you plan to go to hell - because sword fights
rarely take place around 500 oC (932 oF) or so. The smith has the problem now since his steel turns brittle when its
hot. If red shortness occurs, there will be no forged steel objects because the material shatters when the smith istrying to forge it at high temperatures. So all embrittlements are simply bad.
I hear you. You now want me to answer your why questions. Why are phosphorus and sulfur causing DBT transitions atsome special and inconvenient temperatures? And how? For starters I give you a first clear answer:

I don't really know!

Well, let's take that with a grain of salt. I don't really know the deep-down details - and that's also true for mycolleagues. In the words of Jianming Huang, who wrote a PhD thesis entitled: "Ductile-to-Brittle Transition in Body
Centered Cubic Metals..." in 2004: "The (..) mechanism of this (ductile to brittle) transition still remains unclear
despite of large efforts made in experimental and theoretical investigation".
By the way, there are many more things in Materials Science that present-day Material Scientists don't know about
for sure. What a relief! This means that there is still enough work for Materials Scientists and Engineers in the
future. My kids can go for decent careers and do not need to become lawyers or bankers. (The brats actually went
for medical doctor (2) and literature science (1)).
OK - so I don't really know what exactly is going on at DBT transitions. But I do now quite a bit of general stuff about
DBT's, however, and I will share that with you.
I do know, for instance, that hot shortness, in very general terms, occurs if some impurity forms precipitates with alow melting point that like to sit in grain boundaries. When it gets too hot they melt. The ferrite / pearlite grains ofyour steel then are held together in parts only by a liquid. They will still cling together - even if the grain boundaries
are completely liquid - just like wet hair. But hit it with your hammer and the steel falls apart. Sulfur (S) does justthat, so hot shortness is now explained (haha).
What happens at cold shortness is far more trickier. Quote: "Large quantities ofphosphorus (in excess of 0.12% ) reduce the ductility thereby increasing thetendency of the steel to crack when cold worked. This .... is called coldshortness". You will find a statement like this in most steel books.
Notice that the quote above doesn't say that phosphorus causes cold shortness,
only that it increases the tendency for it. But why is phosphorous increasing thetendency for cold-shortness, or as we call it now, a ductile-to-brittle transitions(DTB) at low temperatures? And how does it do that? I have promised (orthreatened?) to tackle these hard questions in this Hyperscript, so I will give it ashot.

Science Link
Cold
Shortness

In what follows here I give you a few simple hard facts about cold shortness. Any attempts to delve deeper into that
subject will open a humongous can of major and very wriggly worms. That's why I will deal with the deeper aspectsof cold shortness mostly in the science module.
Iron, Steel and Swords script - Page 243

When I started to look into the topic in more detail, I had no idea about the size of the can of worms I was about toopen. I spare you the gruesome details, you will probably find more than you are looking for if you use the link above.
The explanation for cold shortness, in very simplistic terms, follows a line of arguments like this:Any crystal under large stress will either deform plastically or fractures. In other words, it is either ductile orbrittle.
Plastic deformation means that sufficiently many dislocations are generated and moved across the crystal.
This needs some minimal energy , some of which is supplied by the stress and some by the temperature . If
you lower the temperature the dislocation process gets more sluggish.
If dislocations hit an obstacle like hard cementite, they might be stopped or slowed down. Grain boundaries
also slow them down, irrespective of some dirt in there. The minimal stress needed to promote dislocation
movement thus depends on the microstructure and the temperature in a rather tricky way. .
Fracturing means that some tiny pre-existing nano cracks grow. This implies that the crack tip runs throughthe specimen and induces fracture. In order for this to happen, a certain minimal stress is needed.. If thecrack tip hits an obstacle like hard cementite, it might be stopped or slowed down. If the crack tip hits agrain boundary with weak spots because some impurity atoms or small precipitates are sitting there, it might
speed up. The minimal stress needed to promote cracking thus depends on the microstructure in a rather
tricky way but not much on temperature.
If you apply serious stress to your specimen, there will always be a competition between the two
mechanisms. If cracking wins, your specimen is brittle, if plastic deformation by dislocation wins, yourspecimen is ductile. In most fcc crystals like aluminum (Al), gold (Au) or nickel (Ni), the dislocations always
win at pretty much all temperatures. But this is not necessarily true for other crystals and you will find a DBT
transition at some temperature.
Since both mechanisms depend in different ways on the microstructure and temperature, phosphorus andany other element in your steel cannot but influence the DBT transition behavior.
In fact, even pure iron or ideal plain carbon steel, or just about all bcc crystals, show DBT transitions - mostly
at critical temperatures TDBT substantially below freezing, fortunately. Before the advent of refrigeratorsthat simply wasn't much noticed. Vikings may have lived in areas where the temperature falls substantiallybelow freezing. But they didn't do major sword fights then, or knew and accepted that their swords broke as anatural thing. They might even have had two swords, one for cold, and one for not-so-cold weather. So they
only were pissed at the smith (and shortly after probably dead), when their swords broke while fighting indecent weather.
So the long and short of cold shortness in (ferritic) steel is not if it occurs (it will), but at what critical temperature
TDBT you will encounter it. With respect to alloying we therefore want to know how the alloy element affects thecritical temperature TDBT and possibly the magnitude of the effect. The figure below makes clear what I mean:

Brittle to ductile transition with various phosphorus(P) concentrations
A few of the original measurement points are shown to givean idea about the experimental scatter encountered
Adopted from: W.A. Spitzig, "The Effects of Phosphorus on the
Mechanical Properties of Low-Carbon Iron", METALLURGICAL
TRANSACTIONS, Vol. 3, MAY 1972, p 1183

A Charpy impact test provided the fracture energy data on the left scale.
The specimen for the red line, shows essentially pure iron. Its detailed composition was: 0.005 % C; 0.001 %N;
0.0045 %O; <0.005 %P; 0.004 %Si; 0.01 %Mn; 0.004 %Si; 0.002 %Ni; 0.002 % Cr.
"Upper shelf" and "lower shelf" is steel engineering slang for the high and low fracture energy associated withductile or brittle behavior, respectively. Their difference is a measure for the magnitude of the effect.
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Those are rather dramatic curves that tell us a lot about the DBT transition phenomena. Let me enumerate the major
points for you:
1. The critical temperature TDBT increases from about –50 oC (–58 oF) for pure iron to about 10 oC (50 oF) for ironcontaining 0.6 % phosphorus (P). This kind of phosphorus steel thus is only good at temperatures around andabove room temperature.
2. The effect of cold shortness is nothing less than dramatic . The energy needed to fracture the steel in a Charpy
impact test comes down from an "upper shelf " value around 100 J to almost zero at the "lower shelf".
3. The results you get in an experiment as illustrated in the figure will, of course, not only depend on the nominal
phosphorus concentration but also on details of the microstructure and on exactly how you tested. You could, forexample, have different average grain sizes for the same phosphorus concentration, and then you would getsomewhat different data.
4. The DBT transition region can be extremely sharp. Take the phosphorus steel with 0,2 % phosphorus, forexample. At –30 o (–22 oF), it is not brittle but ductile. Hit it hard with a hammer (or another sword), and it will
just bend or dimple somewhat. Go to –40 o (–40 oF), and just hitting it lightly will cause it to shatter into pieces.
For higher phosphorus concentrations, the transition is not quite as sharp but still occurs within a narrowtemperature interval.
Now you see why "the (..) mechanism of this (ductile to brittle) transition still remains unclear... ". We can accountmore or less for the points 1 and 2 right above, but point 4 is a tough nut to crack with theory. There are other open
questions concerning DBT transitions; look up the science module if you need to know.
Alloying iron with anything, or alloying iron already containing a mix of alloying elements (then called steel) with one
more element , will always change the DBT transition behavior. The changes might be small but you must be aware ofit.
Generalizing a bit, alloying will always change all the properties of your steel. Playing around with one specificelement might leave some property almost unchanged, make it better, or make worse. The "playing around" part,
meaning the concentration and detailed processing you use, is important.
If you only look at the information about phosphorus (P) as alloying element that is contained in the figure above,
your conclusion would be to avoid phosphorus at all costs. To some extent that is what we do. But before you throwout phosphorous (P) forever (assuming you can do that), you should first look at what it can do for you.
If you cannot throw out phosphorous because you, the ancient smith, do not know how to do that, you better figureout how to live with it.
We have few modern steels that contain phosphorous (P) intentionally because whatever good it can do for you ismostly far easier done with other elements. But we do have plenty of ancient steels that contained phosphorous (P)unintentionally. Despite all the problems it causes, it still could be used to makes steels that were better thanwrought iron or bronze. In fact, phosphorous (P) steel was so important in old times that it has its own sub-chapter,coming up soon.
The basic problem with alloying should be quite clear now:

Making a good alloy is an extremelycomplex undertaking.

If you intend to "invent" a better metal alloy today, you are well advised to assemble a highly knowledgable group of
5 - 10 people, supply a infrastructure with the necessary hardware like furnaces and electron microscopes, and givethem at least 10 years and a sizeable budget.
The odds are actually rather low that they will come up with a new alloy that will be successful in the market place.
Nevertheless - it's the only way to go.

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9.2 Low Alloy Steels

9.2.1 A Closer Look at Low Alloy Steels
How to Make Low Alloy Steel"Low Alloy" Steels are all iron alloys where the concentration of each alloying element is low, say below 1 % or on
occasion 2 %. Some formal definitions demand less that 3.5 % of alloying elements in total but that is an arbitrary
number.
This means that all ancient steels where low alloy steels - as long as you don't count the elements contained in theslag inclusions.
Don't let yourself get confused by names like "micro-alloyed steel". This kind of steel and just about everything else
are just a subgroups of low or high alloy steel. At this point it is sufficient to distinguish between
Low alloy steel - see above
High alloy steel. Obviously steel with alloy element concentrations far larger than 1 % (above 3.5 % in total if
you are a formalist).
Wrought iron. The special "low-alloy steel" case of having rather pure iron with just a little bit of carbon andpossibly phosphorous right from the smelting process.
Cast-iron. The special "high alloy" case of iron with about 4 % carbon (and all kinds of other stuff).
The next distinction I like to make for low alloy steels is:
The major alloying element is carbon. It "works" well if the goal is to increasing hardness cheaply, because it
enables the formation of cementite, pearlite, martensite and bainite.
The major alloying element is phosphorous (P). That is only valid for ancient steels but then it is important. I
will deal with "phosphorous steel" in more detail shortly.
The major alloying element is neither carbon nor phosphorous but other stuff. Whatever carbon is still in
there might not be used for producing cementite and so on but for making carbides with the alloying
elements. That essentially covers modern "high-performance" steels.
Since this chapter is about real steel and not "paper" or laboratory steel, we need to look into how steel making
techniques relate to alloying. It is clear by now that our forebears could neither produce extremely pure iron as starting
material (wrought iron is not extremely pure) nor could they do conscious alloying. But how about modern steelmakers?
Real steel is mostly modern steel, and the first question to address is how modern steel making interfaces with alloying.
I'm going into steel making in the next chapter but a few things in the context of alloying are important now .
As stated before, the advent of the blast furnace, very roughly around 1500, completely changed the process ofsteel making. Before that your iron / steel was never liquid (except high-carbon crucible steel) and you either lived
with whatever elements happened to be in your steel naturally, or you put the alloying element (pretty much always
carbon) into your (wrought) iron after you made it. After - roughly - 1500, steel making consisted of making pigiron", the dirty high-carbon stuff we would classify as cast-iron, and now you needed to take unwanted elements(including too much carbon) out of the stuff.
Nowadays, as for the last 150 years, pig iron is cleaned by blasting air (or oxygen) through it while it is still liquid.
That works quite well but has the drawback that your clean liquid iron now contains substantial amounts ofdissolved oxygen. That is not so good for further processing because the oxygen wants out, and the whole thing
fizzles. Imagine casting a sword blade with champagne (or beer if costs matter) after you shook it vigorously, thenpouring it into a very cold mold. If you rather drink the stuff, just look at water ice that formed out there in the winter:
it's full of pores or bubbles containing the air dissolved in the liquid that can't stay dissolved in the solid. Now
imagine casting at 1500 oC (2732 oF) from a huge barrel full of the fizzy stuff. You don't want to do that. You wantsomeone else to do that while you are far away.
It just won't work. You need to "kill" your iron or steel first. That unfriendly action simply means to take out theoxygen by reacting it with strong oxide formers or oxidizers like silicon (Si), aluminum (Al) or even calcium (Ca). The
silicon oxide (SiO2, also known as quartz) or aluminum oxide (Al2O3 , also known as sapphire or ruby if it contains
the right dirt) that is formed in this process floats on top of the liquid iron and can be ladled off.
By the way, in Germany we do not kill our steel, we do a "Beruhigung" (calming down, pacification). I resist thetemptation to veer off into a little essay about language and culture at this point.
The problem, of course, is that after you produce your "silicon-killed steel" or "aluminum-killed steel", you now havesome left-over silicon or aluminum in your killed steel. You have also some left-over dirt in small but possibly
noticeable concentrations and, of course, plenty of (hopefully) harmless trace elements.
You do not, however, have a lot of solid stuff swimming in the liquid that later would form major inclusions. Whateveris still solid will typically swim as "dross" on the surface or rests on the bottom if it is really "heavy", and can betaken out. That is a huge advantage!

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After you have killed your steel, serious alloying can commence. Knowing the weight of your heat of steel, as we call a(huge!) bucket full of the liquid stuff, you now throw in the proper amount of your alloying elements. For example, if you
go for 0.001 % of boron (B) in your 5 tons of steel, you need to pitch in 50 g of elemental boron, some metal-grey
substance that is easy to get. If you want 0.5 % of carbon, you add 25 kg of coke, and so on.
That seems to be an easy process. It isn't. All kinds of things can happen if you just pitch in your alloying elements
indiscriminately. For the case of boron, you probably buy some stuff from some supplier that contains boron, ofcourse, but also all kinds of secret ("proprietary") ingredients. This link gives an impression about this.
For all the other stuff that goes into the brew, you better make sure how it is best done, too.
If you enjoyed (or suffered) a decent education, something from Shakespeare might now come to mind.
When you're finally done with concocting the brew, solidification and thus processing starts. Temperature profiling is thething to do in order to get the microstructure you want. Easy in principle, not so easy if you make steel by the ton on anhourly base. Nevertheless:In essence, we understand how
modern steel alloying is done.

Basic Carbon Steels
It's time to ask a simple question (again): Considering that I can make rather clean (killed) iron, why should I now add
carbon? I can get all kinds of hardening mechanisms from other elements. Maybe it is better to use something else andto make what I will call a "designer steel"?
Good thinking. That is actually the trend for modern steels. Nevertheless I'll stick with carbon steels for a little
longer. For less demanding applications relatively simple carbon steels might just be more economical than fancy
alloy steels without carbon. Not better, mind you, but cheaper.
So even today a lot of carbon steel is made. In fact, most of the steel made today, around 90 % or so (or roughly morethan a billion tons a year), is carbon steel despite all the fancy "High-Tech" kinds of steel you find in the link. Their
strength and hardenability, though less than that of many alloy steels, is still adequate for many applications. Process
refinements made it possible to improve properties of carbon steels other than hardness, too. Fine tuning by adding alittle of this and that allows to make many different kinds of carbon steels, matched to some particular needs. It goes
without saying that all of this is still rather cheap. I also goes without saying that all these steels are either silicon (Si) or
aluminum (Al) killed. So they always contain a little of the killing element. Of course some intentional manganese (Mn;around 1 %) as standard alloying element is always in there too, to keep the remaining sulfur (S) in check (and for otherfriendly objectives).
We might distinguish four major groups:
1.
2.
3.
4.

Mild and low carbon steel with 0.05 % - 0.25% carbon content
Medium carbon steel with 0.25 % - 0.6% carbon content.
High carbon steel with 0.6 % –1 % carbon content.
Ultra-high carbon steel (UHCS) with 1 % - 2 % carbon content.

The first group, low carbon steels, are the simple and easy-to-work with everyday steels. They are not very hard andthus easily "drawn", e.g. into wires from which nails are made. A bit of hardening is possible but martensite formation
usually does not take place.
What is often called "mild steel" is found at the upper end of the concentration range, i.e. around 0,15 % - 0.25 %carbon. It is the most common form of steel, rather cheap, and provides for material properties that are acceptable
for many applications. If needed, the surface region can be hardened somewhat by carburizing.
The second group, medium carbon steel, includes the typical "tempered steels" of the 19th century. From it the best
sword blades were made for some time, superior to everything from the past, including wootz swords, Japanesekatanas, or pattern-welded composite blades.
Medium carbon steel is still used for products like crankshafts, couplings, tie rods or generally machinery parts thatneed to be mass produced and "strong".
The third group, high carbon steels, provides for rather hard and brittle steels, difficult to work with. They are also morecostly to fabricate, because of decreased machinability, poor formability and poor weldability. Machinability is ameasure for how easy it is to drill a hole into it or, more to the point, to work the material on a lathe.
These steels are good for springs where fatigue resistance is important (if you have a spring in your machine
something is meant to vibrate) or parts where abrasion is of concern, e.g. plough shares and scythes or the modern
equivalent thereof, not to mention wrenches, hammers, mauls, pliers, screw drivers and cutting tools, such as
hatchets, and axes. They also make high-strength wires for you piano or wire saw.
A modern spring steel might give you a sword blade far superior to anything made in the old times and in the 19th
century.
Iron, Steel and Swords script - Page 247

The fourth group, ultra-high carbon steel is of interest to us because ancient wootz steel belongs into that category.
These steels are difficult to work with but can be tempered to great hardness. They are used for special purposes
like axles or punches. Most steels with more than 1.2% carbon content are made by using powder metallurgy.
Above 2.0 %C the world of cast-iron begin.
Here are some major modules concerning steels and alloying:

Illustr.
ModuleProperties

ScienceModuleIllustr.
ModuleAdvanced
ModuleAlloying
scienceAlloy elem.
Overview

Alloying
elements

Iron, Steel and Swords script - Page 248

Module Hub
Major Steels

9.2.2 Designing Low Alloy Steels
Let's Design a High-Strength SteelNow let's replace carbon as the major "hardening" agent and design a high-strength low-alloy steel without muchcarbon in earnest. I'm going just through a few principles that illustrate the salient points I'm trying to make. For more
information use this link.
We want to make relatively cheap steel that can be conventionally welded (liquid welding) but is quite "strong", i.e. hardand ductile. That means it must be low in carbon since we do not want martensite formation, which is bad for welding.
For the same reason we do not want a lot of pearlite. If we think in terms of carbon steel the only choice left is relatively
soft low-carbon steel.
We want, however, rather large hardness (plus a large number of other good properties) that we simply cannot getfrom a low-carbon steel. We do not want high-alloy steels either because they are simply too expensive, not tomention hard-to-weld. What we want to make is a "high-strength low-alloy" (HSLA) steel, one of the major"designer" steels in circulation today. This kind of steel has a market share of about 12 %, which is quite a lot roughly 170 million tons per year. Its development was driven by oil and gas extraction (meaning, for example, steel
for pipelines where welding is a must), construction, and transportation (meaning cars).
HSLA steels are also known as "micro-alloyed steels". This needs some explaining. When a steel person talks
about "alloying", she is referring to elements different from carbon and the commonly accepted amounts ofmanganese, silicon, etc. Bearing this in mind, we now can distinguish three alloy groups:
Micro Alloy Steel: Steel containing small amounts of vanadium, niobium and/or titanium and other stuff withusually less than 0.10 % individual concentration and and a total alloy element concentration of less than
0.15% on top of, e.g., manganese and carbon.
The name is a bit unfortunate because "micro" obviously does not refer, as it should, to alloy concentration in
the 10-6 or ppm or 0.0001 % range, but simply to a a concentration range considered to be "microscopic" incomparison to normal steel.
Then we have the old two assignations:
Low Alloy Steel: Steel containing less than 3.5% of alloying elements.
High Alloy Steel: Steel containing more than 3.5% of alloying elements.
Our HSLA steel to be designed thus still contains the ubiquitous Manganese (up to 2%) and carbon - but not much.
Around 0.07 % - 0.12 % carbon will suffice. The trick is that we do not use the carbon for producing cementite ormartensite but for making metal carbides. Following the principles of hardening, as discussed in chapter 8, but
without using martensite, you know now what you must do:
1. Use solid solution hardening. Use dissolved foreign atoms other than carbon that make it more difficult fordislocations to move.
2. Use precipitation hardening. Take care to keep the precipitates small (including some cementite that might
still be formed). That means to worry about nucleation and temperature profiles.
3. Use grain size hardening. Keep the grain size small. That's not easy. Adding small amounts of alloy atoms
that like to sit in grain boundaries (possibly in the form of small precipitates) and keep them from moving
might do the job.
4. Use work hardening. Or maybe, don't. Work hardening means to deform your steel before you use it. It will
get harder but also loose ductility.
For the first mechanisms we need to look at the relevant figure again. We also need to consider all the affordable
elements not shown in this figure but here.
What we find is that atomically dissolved carbon and nitrogen have by far thebiggest direct effect on the yield strength (owing to their being interstitials), and that
phosphorous kept in solution is very good, too, (but, remember, very bad in cold
weather.
Then we have silicon (Si), manganese (Mn) titanium (Ti) and copper (Cu, not shownin the figure) and some other elements as pretty good solution hardeners. Copper,
however, has drawbacks (including its prize), and silicon causes problems here
too. This leaves, in a first cursory evaluation, manganese (Mn), titanium (Ti), and tosome extent nickel (N) and vanadium (V) as eligible alloying elements for solid
solution hardening.

Alloying
Elements
Overview
Details
Science

Manganese is the clear winner since it also neutralizes spurious sulfur (S) and isquite cheap.
The second mechanism calls for alloy elements that form precipitates either with the iron (of which there is plenty), withthe little bit of carbon left, with iron and carbon, or with the few other elements around. But not with the manganese(Mn), please, because we need that dissolved as single atoms for hardness, and to round up and precipitate residual
sulfur (S).
You also want your precipitates to have a melting point higher than iron to avoid hort shortness, and you want them tobe hard so neither dislocations nor advancing microcracks can cut right through them.
Iron, Steel and Swords script - Page 249

Now look up manganese (Mn) in the periodic table. It sits right next to iron (Fe) and thus can be expected to bechemically similar. That makes you suspect that elements that like to form compounds with iron might also like toform compounds with manganese, which is not good. That rules out elements for micro alloying that like to form
precipitates with iron.
So what kind of precipitates should form? Carbides, of course. That also solves the other problems, because
carbides typically have a very high melting point and are extremely hard. We now need alloy elements that are
known to be strong "carbide formers ". That are all elements that form carbides (surprise!) and win against the ironin the competition for the carbon in there.
All you have to do is to go through the periodic table, looking (experimentally) for good carbide formers. It's a feast
for grad students once more. Many Ph.D. theses' and scientific papers will result.
Elements like niobium (Nb), vanadium (V), titanium (Ti), chromium (Cr), zirconium, (Zr) or molybdenum (Mo), butalso silicon (Si) or boron (B), emerge as possible contenders. All of them like to form very hard carbides with very
high melting points. So we now go and try them out. Each one causes a hell of a lot more work than that little
example I gave you with Copper (Cu) in aluminum (Al). What they do if several different ones are there at the sametime will provide work for generations to come.
We still have the third mechanism, keeping the grain size small.
That involves two major points:
Making small grains in the beginning (whatever and whenever).
Keep those grains from growing.
If you look at the formation of a final ferrite structure from the liquid to the solid, the decisive grain sizes are theaustenite grains at high temperature. To keep them from growing, you shouldn't give them much time to do so, i.e.
you need to work on your cooling rate. In addition, with some luck, some of your alloying elements might like toproduce their carbide precipitates in the grain boundary (easy nucleation) and this might help to keep the grainboundaries from moving. If it can't move, the grain can't grow.
Of course, the iron-carbon phase diagram is not decisive for that any more. More work for grad students.
I'm already discussing the processing or in other words the temperature profiling. This is crucial. Whatever you put into
your HSLA steel to form carbides, it will only work if you cool down quickly. Otherwise all those carbides have time togrow into large sizes and you want them to remain very small, remember? Just one example: Niobium (Nb) or vanadium(V) works already at low concentrations around 0,1 % - provided you know what you are doing. Tiny niobium carbide
particles of about 1 nm size (containing less than 100 alloy atoms) will increase the yield stress from about 20 MPa to
200 MPa, at a concentration of about 0.1 wt % Nb. "Huge" particles with diameters of 10 nm or larger have practicallyno effect anymore! Look at the simple Cu in Al example. It's all there except that the effects are more pronounced in theiron - niobium system.
The problem, of course, is that the outside always cools down faster than the inside. The "inside" thus stays "soft".
All we can do is case hardening - only the "case", the outer layer is really hard. The word to introduce andrecognize now is "hardening depth ". The question simply is: To what depth is the cooling rate fast enough toallow hardening? And how can we measure it? For the second question the answer is easy and given in this link.
Whatever happens during quenching, major things only happen when the temperature goes below the transition
temperature where austenite intends to change to ferrite. The formation of metal carbides, we might assume, also
starts below that temperature. In plain carbon steel this "A1" temperature is around 720 oC (1328 oF). If we could
lower it, there wouldn't be so much time for carbide formation and the carbides stay smaller.
Can we? Of course—by alloying the right element(s).
Even if you overdid your "good stuff break", you should now have gotten the central message:

If you want to change the property ofsome material, alloy theright element(s) the right way.

In normal human life, finding out what is right or wrong gives jobs to a lot of humans. And to lawyers. A hell of a lot of
people working inside some religious organization are concerned about this topic, and they can tell you unambiguously
if what you do is right or wrong with regard to what you eat, how you deal with your girl friend / spouse, how to raise yourchildren, and so on. Then there is that parent-in-law who knows exactly what's right or wrong for her son or daughter,and so on. Just don't ask them about alloying elements.
In contrast, as far as technical human life is concerned, the number of the scientists and engineers who know the rightalloy elements from the wrong ones, and the right way to deal with them, is rather small.
Which group has achieved more I leave open at that point.

Iron, Steel and Swords script - Page 250

If you are into alloying, you should be aware of where you could succeed, and where not. The first law of appliedscience comes into its own. Using it, you will know that making big changes in Young's modulus by alloying just alittle bit of something will not work - period! Or, to give another example, that alloying will always increase theelectrical resistivity.
Nevertheless, alloying plus proper processing does the trick in many cases. The fact that we have more than 1000
different steel alloys, with properties tailored to some particular needs, bears witness to that.

Iron, Steel and Swords script - Page 2519.3 High Alloy steels

9.3.1 Stainless SteelThe Steel Corrosion Problem
Now let's improve a particularly undesirable property that all the steels we have "made" so far possess to a smaller orlarger extent: they rust (apparent exceptions, like the pillar in New Delhi, prove the rule).
Rusting means that the iron reacts with the oxygen from the air (helped by water)
to form all kinds of iron oxides and hydroxides, subsumed under the generic namerust.
There is no good reason why it shouldn't do that. The iron-oxygen bond is far
preferable to the iron-iron bond as far as the second law is concerned, and iron, justlike aluminum (Al), titanium (Ti) , chromium (Cr) , nickel (Ni), silicon (Si) and so on,
has very good reasons to oxidize as much and as fast as it can.
Let's be clear about that: In an oxide containing atmosphere all metals - except thenoble ones - need to be fully oxidized if they want to achieve nirvana.

Advanced
ModuleCorrosion

However, from the materials named above only iron visibly rusts or corrodes, to use the polite name, while aluminum,titanium, chromium, nickel, silicon and so on tend to be rather stable at room temperature. They don't seem to corrodemuch. How come?
Well, all these (pure) elements are actually very happy to react with oxygen, indeed. In doing so they form an oxide
layer on the surface. We now have to basic possibilities:
1. The oxide layer is "dense" and after it reached a certain thickness protects the material beneath it from directcontact with whatever is on the surface of the oxide - including the oxygen! Even better, if the layer getsdamaged, e.g. by scratching, it heals itself quickly and forms a closed layer once more.
2. The oxide layer is not "dense" - you may call it "porous" then. It does allow all kinds of stuff to reach the surfaceof the metal and commit atrocities there. If damaged, it may not heal but allow other reactions to take place.
The first case by necessity contains the miraculous property that the growing oxide film stops its own growth assoon as it has a reached a thickness that does not allow more oxygen to make it to the metal. That doesn't' takemuch. Silicon (Si), for example, grows a very thin layer of (amorphous) SiO 2, otherwise know as quartz, rather fastin air. Quartz ware, as you might know, is used in pretty much all of chemistry because the material reacts withalmost nothing and is impenetrable to most everything. That's why a silicon dioxide (SiO2 ) layer with a thickness of
only 2 nm (or about 8 atomic layers) is already perfectly capable to stop further oxidation of silicon around room
temperature "forever".
Aluminum oxide (Al2O3) does about the same for aluminum (Al), and so on. Below is a schematic picture thatshows what happens.

Oxide layer Formation on Silicon.

The picture would be much the same for most metals. It is important to realize that the oxidation happens at theinterface metal - oxide and that means that oxygen atoms must diffuse through the oxide that has already formed tothe interface oxide - metal,. where the oxidation takes place. Since oxidation is the first step in corrosion, we learn
an important fact right here:

Iron, Steel and Swords script - Page 252

Corrosion is a surface or interface property!

The chemical reactions leading to corrosion must take place at the surface, or more precisely the metal / oxideinterface as defined above. The properties of the interface / surface layers determine what happens. Of course, thesurface structure of some crystal is determined to some degree by the bulk structure but just knowing the bulk
structure will not be sufficient to predict the corrosion behavior
Since diffusion at room temperature is typically slow, it will be effectively zero for oxide layers just a few nm thick. In
the case of silicon, the "native" oxide it carries around at room temperature is typically 2 nm thick. If you increase
the temperature to, say 1000 oC (1832 oF), you get thicknesses up to a 1 µm if you keep going for a few days.
Layers just a few nm thin are invisible to the eye, and that's why all these oxide protected metals (including silicon)
look just as silvery-gray as the "naked" metal (that few people outside science have ever seen). There are also
metals where the oxide layer eventually grows so thick that you see it - take "green" copper, for example.
In contrast to iron and particularly carbon steel, the oxide layers immediately formed upon contact to oxygen forwell- passivated metals, as we call the effect, are uniform and dense. After they have formed to a sufficient
thickness, they simply prevent oxygen from reaching the metal and thus stop further oxidation. If they are damaged,
new oxide forms faster than anything else, effectively repairing the protective layer.
Iron, and in particular steel, doesn't passivate by just sitting in air. This is a bit peculiar - most metals, if you think
about, appear to passivate. Well - no! We just never think much about all those metals and alloys that don't. All
Alkali and many earth alkali metals (e.g. Li, Na, K, Rb, Cs, Ca, Sr, Ba) won't last long in air (or, worse, water). We
just never think about those elements because they we never use them as "metals".
Why does the "oxide passivation" not work in this case? There is no simple general answer. There are steels, after
all, where it does work - so-called "weathering steels" for example.
There is, however, a simple specific answer for carbon steels! In these steels you have largish cementite phases.
We don't know (yet) if that oxidizes and, if it does so, what kind of oxide it will form. Carbon (di)oxide? That's a gas!
In any case, the oxide layer forming on the ferrite simply cannot cover the cementite too. There is simply no closedoxide layer on carbon steel and at the "edges" all kinds of bad things can now happen. An outline of that is shown
below.

Oxide layer Formation on Carbon Steel

Above larger cementite parts no oxide can form. The oxide to the left and right, since it expands when formed,"squeezes" the cementite, meaning that there is a lot of stress and strain in the surface near layers now. Smaller
cementite particles will disturb the oxidation locally; they also may become embedded in the oxide formed, possibly
causing cracks. Add to this that there are several kinds of iron oxides and hydroxides (in contrast to aluminum, andsilicon, for example), and that not all oxides are insulators (like silicon and aluminum oxide) but semiconductorsthat may participate in "electrochemical" corrosion, you get a first idea why carbon steel readily rusts while wroughtiron does not.
Moreover, do you also get a first idea of what to do about preventing rusting? I hope so.
In summary: Many metals (and other elements), while reacting strongly with oxygen (O), tend to form thin passivatingoxide layers that protects the metal surface from further oxidation. Their oxides, we say, are efficient diffusion barriers atroom temperature, disallowing diffusion of the oxide (and anything else) to the metal. We are back to our old adage:

If the atoms can't move, noting can happen.

Iron, Steel and Swords script - Page 253

Not so with iron or plain carbon steel. There are many possible iron oxides (more to corrosion of steel in this link) but adense layer with diffusion barrier properties does not easily form and your blade will corrode if you don't give it extensive
care.
Let's face an uncomfortable truth: there is no such thing as a corrosion resistant plain carbon steel. It just can't be.
If you want corrosion resistant or stain-proof steel, you must do one or all of the following:
Avoid large non-oxidizing phases of all kinds, in particular lamellar cementite.
Establish conditions where a closed oxide layer can be formed.
Supply chemical "incentives" to make that oxide "good" oxide that is closed, dense and able to do "selfrepair".
That is quite a list. What comes to mind now is certainly "stainless steel". However, there is no such thing as "a"stainless steel; it's rather a large family of high alloy steels. Let's give that type of steel a first cursory look; more in thislink
Stainless SteelThe major trick to make "stainless" steel, meaning steel that does not rust, is to make sure that its surface is always
covered with a dense layer of essentially chromium oxide (Cr2O3), a good diffusion barrier for oxygen, that will protect
the steel from further attack by the oxygen.
Plating a layer of pure chromium on your steel will do that, too. However, you cannot do anything to your productafter the plating because any damage to the thin Cr layer will induce localized corrosion of the steel underneath.
Alternatively, you can include that much chromium (Cr) into your steel that there is always a sufficient number ofchromium atoms at the surface to induce a closed layer of mainly chromium oxide. (Cr2O3). It's not as much as you
might guess, all you need is more than 11 % (a number that can actually be calculated); up to 25 % or so are usedin practice. Interestingly, this mix - just iron and chromium, no carbon - stays bcc at almost all temperatures .
Hardly any austenite is formed when heating up. That also means that there is no strong hardening upon quenching
because there is no phase transformation, martensite formation, and so on.
A bit of carbon, 0.6 % or so, changes that. There will be some austenite and thus the possibility of (case) hardening
by quenching and martensite formation. What we get then is a simple but good ferritic "stainless" steel for ballbearings, kitchen knifes or surgical instruments.
The kind of composite phase diagram below illustrates that.

Iron carbon phase diagram with reduced
austenite "field" due to chromium additions.
Unspecified Internet source

What the figure shows is how the region of stable austenite (yellowish colors) decreases with increasing chromium
concentration. Chromium, in other words, is a ferrite stabilizer.
Above 12 % chromium austenite does not exist any more for low carbon concentrations. If you go to 0.5 % carbon,
you will still have austenite; only the transition temperatures are somewhat changed. More to that in the science
link.
This opens a whole new bag of tricks that can we explore by adding substantial amounts of other element to achievecertain parameters.

Iron, Steel and Swords script - Page 254

The possibilities are humongous but I will only mention one more member of thehigh-alloy family: austenitic (stainless) steel. Add some 10 % of nickel and 1 %or so of manganese, and the transformation temperature from austenite to ferrite
comes way down from its customary 770 oC (1418 oF). It gets low enough so it
doesn't take place at all anymore. You now have steel with an fcc lattice with theremarkable property that it is not magnetic.
Austenitic steels are not only rustproof and non-magnetic, they can also be madeto be relatively hard. Since they are fcc crystals, they do not suffer much from thedreaded ductile-to-brittle (DTB) transition and thus are great for low-temperatureapplications. They are typically more ductile than comparable plain carbon steel
and thus are easy to work with because they can be pressed or drawn. They also
have better aging properties but are more difficult to machine.

Science Link
Alloy science

You will find a lot of austenitic steel around you. Your kitchen sink will almost certainly consist of austenitic steel
but also the inside of your electron microscope, and many of the pipes in your nuclear power plant.
By the way, I know that a lot of you guys out there hate stainless steel knives on the ground that they cannot be kept
sharp. I will address this topic later.

Iron, Steel and Swords script - Page 255

9.3.2 Maraging SteelUsing steel science, let's "design" high-tech steel once more to get a feeling for what can be done; we will stay withhigh-alloy steel. What we want to make now is a steel that is:easy to shape (meaning it is soft),
extremely tough (meaning it is hard but still ductile),
doesn't suffer from limited hardening depths.
and can be welded.
That does sound like a big, fat contradiction in terms, doesn't it?
Well, yes, but there are ways. What we need is "obviously" a steel that we harden after we have worked it into thedesired shape. Since we usually work steel around room temperature, the only option for a hardening process is
now to heat the steel to some temperature, and keep it there for some time. Temperature profiling once more, justthe "wrong" way around. So far we always softened a material by heating or tempering.
Or did we? Maybe you remember the example where an alloy got harder upon heating?
This yet-to-be-determined process also takes care of the uniformity of hardening. While you can never cool down
quickly and uniformly, you can heat uniformly. Just heat up slowly. Since not much will happen before you reach theprocess temperature, all is well.
What we are about to do is to make "maraging" steel. The name is short for "martensitic ageing" and, while fully
correct, leads you straight into wrong associations. So far, "martensite " was code for "distorted ferrite containing
carbon and being extremely hard". While not wrong, it is a bit too special. I have pointed out before that martensite
is only very hard if some carbon is stuck in there and distorted the crystal lattice. Undistorted martensite in ironwould just be ferrite and that is rather soft. You might think that the term "undistorted martensite" is an oxymoron (acontradiction in terms) because it just means bcc ferrite. Well - you're wrong.
Nice clean bcc ferrite that resulted from the nice clean fcc austenite preceding it on the temperature scale by asudden martensitic transformation is quite different from the bcc ferrite that is produced in the normal diffusion-driven
way. It is small-grained and full of twin boundaries and dislocations! Why? Because carbon or no carbon - all the
problems with fitting sheared parts of the crystal into the space available haven't changed.
What that means is that carbon-free martensite (= ferrite) is substantially harder then regular large-grained ferrite
with not too many dislocations.
We want our maraging steel to be relatively soft when its in the martensite structure. That requires two things:
1. No carbon. But there is no martensite (= ferrite) formation by shear in pure iron, so we need
2. At least 19 % nickel (Ni).
Nickel, like manganese (Mn), cobalt (Co) and most of the nobler metals are known as γ stabilizers, they produce
phase diagrams known as open γ-field systems (the link leads to the "alloy science module"). What all that meansis that with increasing alloy element concentration the transition temperature austenite ⇒ ferrite (γ ⇒ α) comes
down. That makes diffusive transitions more and more difficult and at some concentration they just can't happen at
all any more. That's when martensitic transformation takes over. Even that can be suppressed for proper highalloying and then leaves you with austenitic steel.
The γ ⇒ α transformation for Fe - 18% Ni steels starts at 600 oC (1112 oF), and that is just "too cold". These steels
simply will not decompose peacefully into equilibrium austenite and ferrite, even if held for very long periods at lower
temperatures. Instead, during cooling the Fe-Ni austenite transforms to hard but not extremely hard "martensite"with a bcc crystal structure.
That's already rather tricky but not doing you all that much good. The trick now is to alloy optimized amounts ofelements like molybdenum (Mo), cobalt (Co) or titanium (Ti) that are capable of forming hard intermetallic compoundswith nickel (Ni), things like Ni3Mo or Ni3Ti. Those alloy elements are not doing much during the cooling down necessary
to form the iron-nickel martensite but will provide for a lot of added hardness when you now start the "ageing" bit, theannealing at the right temperature for the right time. It goes without saying that before you start hardening by ageing,
you first shape you relatively soft material into the form you want it to be.
Of course, if you heat up to temperatures too high (roughly above 600 oC (1112 oF), you just form austenite again.
But if you pick temperatures around 450 oC (842 oF), you might form a lot of tiny intermetallic precipitates fasterthan your martensite decomposes into austenite.
If everything is done just right, the precipitation hardening mechanism, on top of the hardening already there by themartensite, will easily double or even treble the hardness—without compromising ductility too much. This is what
you see in the figure below:

Iron, Steel and Swords script - Page 256

Yield strength (or hardness) development during
the ageing of maraging steel.
Source: From a data sheet of "Böhler". A Ni 18.5 %, Co 9%, Mo
5%, Ti 0.7% steel

A typical example of a good maraging steel is an iron alloy with 17 % - 19 % Ni, 7 % - 9 % Co, 4.5 % - 5 % Mo and
0.6 % - 0.9 % Ti. Tempering or "ageing" takes place around 490 oC, producing intermetallic precipitates. The term
"ageing" was chosen in analogy to what we know from our old friend, the aluminum (Al) - copper (Cu) model
system.
The initial development of maraging steels is attributed largely to work by C. G. Bieber, in the late 1950s. This work
resulted in the first two grades of maraging steel being introduced to the market. These steels contained 20 % and 25 %nickel, respectively, with small additions of aluminum (Al) from "killing" the steel, and titanium (Ti) and niobium (Nb) forforming precipitates. Since then many variants have been introduced.
Maraging steel, while used for all kinds of especially demanding applications, is still under development and not all
details are fully understood. In particular, adding substantial amounts of cobalt (Co) is rather helpful - see below but what exactly cobalt does is not all that clear. Co may decrease the solubility of Ni3 Mo in the iron-nickel
martensite but I'm not sure if that is the last word.

Combined action of cobalt and molybdenum onthehardness achievable hy ageing..
Source: Key to metals

This is a rather curious diagram. It seems to indicate the hardening effect of proper "ageing", i.e. of forming optimal
densities and sizes of certain precipitates seems to increase linearly with the product of the molybdenum andcobalt concentration. This means that it is proportional to each concentration by itself. This is now one of thosemany little puzzles posed by experiments that theory needs to solve.
This link leads to a 1999 research paper, more or less selected at random, that nicely illustrates some of the
problems, including "banding", something that will exercise us quite a lot as soon as I get to wootz swords; "deadheats" not amenable to "corrective healing actions"; and "elimination of the research staff" in order to save money
and make the problems go away because nobody talks about them anymore.
Maraging steel with yield strengths of 1500 MPa or more are possible (corresponding to a Vickers hardness up to 800
everywhere , not just in the "case"!) at a ductility of 6 % - 8 %!

Iron, Steel and Swords script - Page 257

There is your material for your ultimate sword blade! Indeed, in modern fencing, three kinds of blades are used: thefoil, the épée and the sabre / saber. The all look quite similar to the layman and often are made from maraging steel;this might even be required by international rules.
However, production, import, and export of maraging steel is also monitored by international authorities because it isparticularly suited for use in gas centrifuges for uranium enrichment. Lack of maraging steel significantly hampers
this process; ask your friendly Iranian politician.
What Modern Steel Making Tells Us About
Sword Making in the Old Times
To summarize once more: Modern steels like the HSLA and maraging steels introduced here resulted from scientificinsights into structures and hardening mechanisms. They are many more steels like that; the link will provide a lot ofreading. Steel research and development is not yet finished but an ongoing and important enterprise. The decisive
factors for progress were the scientific revolution in the early 20th century and the insights into what crystals are andhow they deform around the middle of the 20th century.
In the 3000 plus years of iron and steel technology before that, our forebears did not have the slightest chance to comeup with something like micro-alloyed, stainless, or maraging steels.
You just can't get far in designing and testing steels if you don't know what
happens, can't see your precipitates, and can't measure key properties in order to
get quantitative data. In other words, with no knowledge about deformation
mechanisms, impeding dislocation movement by obstacles, and at best optical
microscopes instead of the whole bag of sophisticated micro-analytical tools wehave today, you are simple "blind".
If you want to make a better sword blade relative to the state-of-the-art, you can
only go by trial and error. This will only get your that far. So if your technique,based on centuries of experience gained by your forebears, allows to make good
blades most if not all the time, you eventually stop experimenting at all and cling
slavishly to the recipes that work.

Link Hub
Major Steels

Japanese sword blades, for example, are just plainly amazing giving the "blindness" of their forgers to what they
were doing. The same thing, of course, is true for Celtic / Roman / Alemannic pattern welded swords and oriental
wootz blades.
The down side of this is that no more progress will be made after your blade-making process was declared perfect andcanonized; e.g. in 16th century Japan. Is that bad?
Well, let's look at an example from a different but related sphere of human enterprise: art. Painting in the West waspretty good in the 16th century, just like sword making in Japan. Botticelli, Cranach, Dürer, Leonardo ,Raphael, Tizian, and many others come easily to mind (I did grant you a halfway decent education)!
Some may claim that the masterpieces from these painters have never been surpassed but I beg to differ. Painting
in the West has evolved since then in a multitude of ways, and while I could do without certain works of art createdsince then, I would not like to miss the French impressionists, parts of art noveau, and many other art styles quite
different from 16th century painting.
In contrast, after apparent perfection was achieved, the art of steel as embodied in blade forging did not evolve further inJapan - and that's a pity. In other parts of the world it did; you only have to look the way the shape of swords changed
and diversified.
Constant experimenting lead to progress in iron and steel technology, which in turn eventually lead to guns,
submarines, fighter planes, nuclear bombs, and so on.
You might consider that this does not constitute much progress with respect to armed conflicts. If the good or thebad guys win is still a matter of chance or taste; there are just a lot more dead innocent bystanders. I tend to agree.
But better steel also gave us cars, railways, airplanes, boats, tractors, machinery of all kinds, radio and TV,
computer tomography, painless drilling at the dentist, minimal invasive surgery (I got a taste treat of that and liked itvery much!), and so on. All of that would be impossible without advanced steel.
And don't tell me that there is hardly any steel in a computer or cell-phone! The factory where the microelectronic
chips are made is full to the brim with machinery made from all kinds of steel!

Iron, Steel and Swords script - Page 258

9.4 Phosphorous Steel

9.4.1 Phosphorous Steel - an Orderly Introduction
Why We Need to Look at Phosphorous SteelNow lets have part of the truth about Phosphorous (P) in steel - the rest will follow later. Phosphorous was and still isan undesired element in almost all old and modern steels. Only recently it is used - carefully - as an useful alloying
element in some advanced steels. Cold shortness is one of the major problems it causes. Phosphorous increases the
DTB transition temperature; brittle steel at cold weather results.
But so far I have consistently maintained that phosphorous is supposed to be not always harmful like sulfur; it mighteven be beneficial. So what are its good points?
Phosphorous can be used to harden steel. So long as it is atomically dissolved it is one of the three outstanding
solution hardeners; look a the diagram in the link. What's more, it might protect the steel from corrosion. The
uncorroded part of the patern-welded sword shown here was phosphorous steel for sure. Phosphorous also changes
the look of your steel. It makes steel brighter or "whiter" and that was of large importance for pattern welding
techniques, where the pattern should be clearly visible.
Nevertheless, in the 19th century a lot of time, money and effort went into getting phosphorous out of iron; I'll get tothat. Nowadays we rarely employ phosphorous (P) for modern steel - in contrast to sulfur (S)! I've stated that sulfur
is always bad before, but there are exceptions. It is exactly the "bad" properties of sulfur that are made useful forsome special applications; this link will tell.
So why do I devote a whole sub-chapter to phosphorous steel? Simple:

Phosphorous steel played a major rolein ancient steelmaking.

Moreover, since many European ores tend to contain plenty of phosphorous, dealing with its many effects exercised
steelmakers mightily until not so long ago. I will cover that later in some more detail.
Before I get started, one more word to the wise: In the light of more recent insights, it is quite possible that not
everything labelled "phosphorous steel" in the past is actually phosphorous (P) steel. It might be steel containing
arsenic (As) or an As - P mixture.
It's not so simple to tell the difference without rather modern analytical tools. I will get to that later, too.
The Ancient Iron Pillar in India that Does Not RustIn Delhi you find a famous 1600-year-old huge iron pillar (7 m tall, 6 tons in weight), forged
together from many pieces of wrought iron with low carbon content that simply does not rust.
Its "secret" has recently been unveiled by Indian scientists. The relatively large amounts ofphosphorous in the iron and in slag particles within the iron, catalyzed the formation of a
special kind of rust, so-called δ-FeOOH ("Misawite") plus a layer of crystalline phosphates thattogether form a stable protective layer on its surface.
This basic paper from R. Balasubramaniam relates the story of the pillar in great detail andgoes into great length to describe its microstructure and the history of its investigation. His
second article is shorter and asks if we can learn anything from the old phosphorous-iron? Not
surprisingly, his answer is: yes, indeed!
I doubt very much, however, that the international steel community is listening.

Iron, Steel and Swords script - Page 259

phosphorous in the iron and in slag particles within the iron, catalyzed the formation of a
special kind of rust, so-called δ-FeOOH ("Misawite") plus a layer of crystalline phosphates thattogether form a stable protective layer on its surface.
This basic paper from R. Balasubramaniam relates the story of the pillar in great detail andgoes into great length to describe its microstructure and the history of its investigation. His
second article is shorter and asks if we can learn anything from the old phosphorous-iron? Not
surprisingly, his answer is: yes, indeed!
I doubt very much, however, that the international steel community is listening.
The New Dehli iron pillar, while certainly a work of art and technological cunning, is actually
made from a poor kind of steel. Its composition varies and the carbon concentration is
generally low. Typically it contains somewhat more phosphorous than carbon. In
consequence, it shows the typical phosphorous "ghost structure" (see below) when astructural etch is done.
Moreover, it contains a lot of slag inclusions. Really - look a the the picture below! The large
black stuff is slag. I don't want to be a spoil sport, but if a composite material like this canstill be called "steel" is questionable. In any case, a sword made from that material may nothave corroded easily but I don't believe you would have been happy with it in a fight.

Microstructure of Dehli pillar. The large
black islands are slag inclusions!
Source: Adopted from Balasubramaniam

Rust
proof
1600
years
old ironpillar inNew
Dehli
Source:Wikipedia

The Dehli pillar illustrates quite nicely that whenever you attempted to make steel in ancient times, you may have run
into phosphorous (P) as one of the major alloying elements in your steel. That was true then, and it still is true now. Partof the reason for this is that the "bog iron", used for millennia to make iron and steel in large parts of the world,
contained relatively large amounts of phosphorous. Regular ore in large parts of the word is often phosphorous-rich, too.
Part of the steel technology of old thus followed the old anglo-saxon proverb "if you can't beat 'em, join 'em", and madeand used primarily phosphorous steel or phosphorous-carbon and not "plain" carbon steel.
You, the smith of old, did not have they the faintest idea about phosphorous in your iron, of course. When you made(or more likely bought) a piece of iron / steel, you didn't call it carbon or phosphorous steel. You differentiated thevarious kinds of iron / steel available in different ways - and we do not know much about that. Perhaps you knewthat the "more shiny" steel needed to be treated in a different way.
If you belonged to the smiths who could, for example, make a Roman pattern welded sword of the 3rd century, youmust have had had a whole bag of tricks up your sleeve, and it is doubtful that we know them all. I have tried tocollect some of that in a science module but we can never be sure of what we missed.
So you actually made phosphorous steel swords. How good they were - I don't know. Many are still around anddisplayed in museums (not necessarily meaning that the museum knows that). They may be a bit worse for wear
but not as badly corroded as carbon steel swords.
If those phosphorous steel swords would have been an inferior product that got you killed easily, they wouldn't havebeen on the market for centuries in the good old times.
You will see that phosphorous is just as efficient as carbon and nitrogen (N) for solid solution hardening of ferrite,
just look at this figure again. Ferrite is the bcc or α phase of iron / steel and that, according to the phase diagram,is what we will have in the iron - phosphorous system for very low phosphorous concentrations at room temperature.
So you actually can harden ferritic iron with a small amount of phosphorous.
In what follows I will first give the "science" of phosphorous steel a quick look, and than consider old phosphorous steel
a bit. The issue will come up again in the chapters to follow, where I deal with iron / steel making and swords in moredetailIron, Steel and Swords script - Page 260

The Science of Phosphorous SteelLet's do a laboratory kind of (thought) experiment and make an ideal phosphorous or P-steel. R. Balasubramaniam (orrather, I suppose, a grad student) has done exactly that; look it up in the second article mentioned above.
Or maybe don't. If you got so far with this Hyperscript and understood the vital parts of it, you will now go straight to thejugular and tell me: "Give me the iron (Fe) - phosphorous (P) phase diagram. Knowing now a bit about hardening
mechanism in general, plus having the phase diagram", you are telling me, "will allow me to make some prediction
about P-steel. How difficult can it be".
OK - here goes. Here is the iron - phosphorous phase diagram. If you compare it to the iron- carbon phase diagram you probably will get a bit confused. There are some similarities, allright, but especially for the low phosphorouspart the phase diagram is quite different.

Phase diagram iron - phosphorous
Phosphorous stabilizes ferrite and tends to close theaustenite field.

There is hardly any austenite (the yellow γ phase). That's because
phosphorous does what is known as "closing the γ-field"; just like arsenic(As), silicon (Si), aluminium (Al), beryllium (Be), titanium (Ti), vanadium (V),molybdenum (Mo) and chromium (Cr).
More to that in the science link.
Below is an enlargement of the important part of the Fe-P phase diagram. It
is actually easy to understand. Just assume that phosphorous hates the γphase or austenite so much that it will do everything to avoid it. Ideally
there should be no γ-phase.
On the other hand, pure iron must have the fcc γ-phase between 911 oC(1672 oF) and 1392 oC (2538 oF); this is symbolized by the fat dark blueline.

Science Link
Alloy
science

So at compositions close to pure iron the phase diagram as shown below is just the best compromise between
totally conflicting demands. By the way; I used different colors for the same phases or phase mixtures in the twophase diagrams shown here. I did that not only because I'm lazy and didn't check what color I used before but also
to demonstrate that those colors are completely meaningless. Their only job is to make the pictures prettier and to
guide the eye.

Iron, Steel and Swords script - Page 261

Low concentration part of the iron - phosphorous
phase diagram
and the development of ghost structures

Now go ahead and derive the microstructure you are going to see at room temperature, starting with the red state point
I'll give you an hint: Looking at the microstructure at room temperature with some etchant that is sensitive tophosphorous, you will find a "ghost structure". The picture below shows some "ghosts" from the New Dehli pillar.
Can you do it? I doubt it. That's why I included a few helpful sketches in the picture above.

Ghost structures in phosphorous steel
Here is another picture
Source: Adopted from Balasubramaniam

What do we see? We know that we must have ferrite, and the dark lines,
as always, are the grain boundaries between the ferrite or α grains. The
darker areas are the "ghosts". They become especially well visible if you
play with the focus of your microscope a bit. Depending on your focus
setting they could also be brighter than the rest.
The ghosts in the picture above are actually depressions in the ferrite
grains. You thus can focus either on the lower surface within the
depressions or the higher surface; both are seen best at some defocus
conditions at low magnification.
But why should the etchant remove more material in some areas? Because
Iron, Steel and Swords script - Page 262

What do we see? We know that we must have ferrite, and the dark lines,
as always, are the grain boundaries between the ferrite or α grains. The
darker areas are the "ghosts". They become especially well visible if you
play with the focus of your microscope a bit. Depending on your focus
setting they could also be brighter than the rest.
The ghosts in the picture above are actually depressions in the ferrite
grains. You thus can focus either on the lower surface within the
depressions or the higher surface; both are seen best at some defocus
conditions at low magnification.
But why should the etchant remove more material in some areas? Because
the ghost are phosphorous-poor regions, etching a bit faster than thephosphorous-rich areas. They are the "memories" of the phosphorous-poor
austenite grains that formed within the ferrite grains and then disappeared
again.
Let's see how that works:
At the temperature where we start in the example above we have coexisting ferrite and austenite grains. If you allow
enough time at the starting temperature, the grains will be rather large, with the ferrite grains being phosphorous-rich(about 1.2 %) and the austenite grains being phosphorous-poor (about 0.5 %) as indicated by the necessary splittingof the state point. As soon as we start to cool down, the ferrite grains must grow and the austenite grains shrink.
This is easily done, the existing ferrite or α grains will just penetrate into the austenite, as shown in the middle
figure. However, the new α parts will be phosphorous-lean since there is normally not enough time for thephosphorous atoms in the "old" α grains to diffuse into the new areas. As soon as we leave the two-phase areaaround 910 oC (1670 oF), all austenite has turned into ferrite, but it will be phosphorous-poor ferrite!
We have only ferrite now but the former austenite regions will now be phosphorous-poor ferrite embedded into
phosphorous-rich ferrite. Since most etchants dissolve phosphorous-poor ferrite a little faster than phosphorous-rich
ferrite, the phosphorous-rich regions stand up like mesas on the plane of the phosphorous-poor background. Hereare your ghosts!
The link not only gives more details but also points out why phosphorous ghosts are not quite as simple as I makethem look here.
But beware! Any alloying element that is an α-stabilizer must have a phase diagram similar to that of iron-phosphorous
for low concentrations and thus produce "ghost" austenite.
In either case, if you shall see "ghost" after some defect etching depends on how well the alloying element could
equilibrate its concentration during cooling (not all that well, probably) and in particular if your etchant picks up small
concentration differences of some element being in there in small average concentrations. That is rather unlikely except the element in question does similar things as phosphorous and that is probably true for arsenic (As) and maybe
antimony (Sb).
It is quite possible (if not very likely) that ancient steels that have been classified as "phosphorous steel" because aghost structure was seen after etching, actually contain either phosphorous, arsenic, antimony, or a mix of thoseelements. Research into this is just starting.
What else besides ghost structures might we find in phosphorous steel? Iron-phosphide precipitates (Fe 3 P), ofcourse. Look at the phase diagram!
Considering that we usually do not have "plain" phosphorous steel but steel with a mix of carbon and phosphorous(plus whatever else might be there), things tend to be even more complicated.
There is no need to delve deeper into this, however.
Knowing the microstructure is nevertheless very important. It gives clues as to the heat treatment and the hardness andductility of phosphorous steel, and that is no mean feat! Unfortunately the microstructure doesn't tell us much aboutother interesting properties of phosphorous steel:
Phosphorous steel is "white", i.e. reflects visible light in a different way than "normal" steel. That is an important
property for pattern welded swords since it allows to see the pattern! How that property relates to the structure issomething I do not know. I do know, however, that this is a tough nut to crack.
Phosphorous steel corrodes considerably less than regular (carbon) steel of comparable (medium - low)
hardness. Once more a property that is not easy to predict from knowing the microstructure. One might guessthat the absence of large cementite particles is helpful but that doesn't lead very far. Just like optical properties,
corrosion relates to surface properties and knowing the bulk structure doesn't help all that much.
Phosphorous steel has a strong tendency to be "cold-short"! That is very, very bad! I don't think that anyone
could predict the rather extreme influence of phosphorous on the ductile-to-brittle transition from only knowing the
microstructure!
The long and short of all this is: Phosphorous in iron has exercised iron and steel people very much throughout themillennia - and it will keep doing this! It is a kind of thorn in the soft underbelly of iron and steel science that causes
permanent pain, reminding us that we are not yet finished with Material Science in general and steel science inparticular.
On the other hand it was used a lot. Maybe just out of necessity because you couldn't avoid it but evidence ismounting that our forefathers used the stuff deliberately and possibly even made it on purpose!
Iron, Steel and Swords script - Page 263

9.4.2 Phosphorous Steel - a Chaotic Succession
Originally I planned to call this module "Phosphorous in Ancient Times". After quite some time of looking into the issue,
I concluded that the new headline is better. So I won't go smoothly from one point to the next, pointing out how they are
all related, that we understand it all, and that my brethren and I are really superior guys who you should send large
amounts of money to or at least worship a bit.
I'll just give you a taste treat of what is out there. Since the topic "phosphorous in iron" will come up several times again
in various contexts, I will on occasion also give links to one of the modules ahead.
Let's start with a quote from Samantha Rubinson's 2010 thesis, p.280:"Phosphoric iron was a commonly used alloy in the Early Medieval Britain. 66% of the artifacts examined in thisstudy contained significant amounts of phosphorus in their iron alloys.
This research found that phosphoric iron was one of the three major iron alloys used in Early Medieval Britain. This
result indicates that phosphoric iron was present in much larger quantities than previous studies (McDonnell 1987b,
McDonnell 1992, Tylecote and Gilmour 1986) were able to identify. This discrepancy was due to the limitations in
identification of the alloy. .... These results indicate that many of the preconceptions of phosphoric iron are invalid."
1)

Consider this, and in addition that phosphoric steel was nearly always used in the heydays of the pattern-weldedsword (300 AD - 800 AD) on the continent. A first major question emerges:

Did our forebears make phosphoric iron intentionally?

Did our forebears like to work with the stuff? So far everybody (including me) more or less assumed without muchdiscussion that phosphorous in (old) iron got in there unintentionally because phosphorous-bearing iron ore was used in
smelting. Samantha Rubinson and others are not so sure anymore. Maybe the old ironmongers added phosphorousbearing stuff like bones (containing apatite or calcium phosphate) intentionally to what they put into their smelters?
This questions leads us straight to smelting technologies, the growing awareness that smelting iron is far more
tricky than imagined, and that our ancestors could smelt iron and steel in far better ways than imagined not so longago.
We simply do not know enough about the old "bloomery" techniques used before the advent of the blast furnace roughly - around 1400. More to that (far more!) in chapter 10.2
There is second (minor) question hiding in that quote: Who discovered when and where that ancient steel was often
phosphoric steel?
Samantha quotes work of McDonnell, Tylecote and Gilmour from about 1985. I feel certain that there are older
sources but don't feel like looking into that right now.
That feeling is partially due to the expectation that early researchers stumbling on to phosphoric iron could not
possibly have gotten everything right. Getting a grasp on phosphoric iron needs more than seeing some ghosts,
interpreted as phosphorous-rich areas, after defect etching. And that "more" was not available until 20 years ago.
This leads straight to the next point, raised more recently by Samatha Rubinson but also by others:
Could it be that "ghost structures" or other etching results that were interpreted as caused by phosphorous wereactually due to other elements, e.g. arsenic? Or maybe a mixture of elements?
The general answer is: Yes, it could be. After that it becomes muddy. While there are indications that there is sucha thing as ancient arsenic iron or phosphoric-arsenic iron, it is to early for me to go deeper into this.
Of course, one needs also to consider the negation of the question above: Could it be that there is phosphorous /arsenic / etc. in the steel and no ghost structures are produced?
Yes, that could be; says Samantha ("In many cases no indicators were present to identify the presence ofphosphorus in the ferritic microstructure"). Ghosts are tricky (the British should know) and not always around when
they should be. Again, a topic that needs far more research before much more can be said.
While a steel containing some phosphorous and some arsenic can be expected to behave roughly like a steel with only
phosphorous at some higher concentration (the sum of both), the same can not be true for a steel that contains
phosphorous and some carbon. While we do know a few things about P,C- steel, I won't go into that topic except tonote that this kind of ternary alloy was rather common, at least as far as studied by Samantha Rubinson. Here is what
she found:

Iron, Steel and Swords script - Page 264

Phosphorous and carbon concentrations in early
medieval
samples from England
SourceThere is no particular trend visible; almost everything goes. Note on the side that almost pure carbon steels comewith concentrations between 0.1 % and - hypereutectoid (!) 0.9 %.
Now let's look at a few more interesting points:
There seems to be some consensus that phosphoric iron is easier to forge and to work with than carbon steel. It
seems to be particular beneficial to wire drawing. That is not only claimed in the link given above but seems to be akind of diffuse common knowledge. Of course, we will only get to know particulars if experienced smiths do specificand well-designed experiments.
Phosphoric iron can be harder then wrought iron. That is no surprise, we know already that it is one of the threeoutstanding solution hardeners. However, this necessitates that the phosphorous is atomically dissolved and notprecipitated as the phase diagram demands for nirvana (equilibrium). In addition, it should not be concentrated ingrain boundaries either. Here is what Samantha found (turned 90o and augmented by me) in comparison to what
well-known Hungarian / Czech Republic researchers 1) found:

Hardness versus phosphorous concentration
SourceSamantha Rubinson's data are a bit strange. While quite a few points inside the range outlined in blue would fall on
the expected linear increase line (that means doubling the P-concentration would double the hardness; the red line
shows the slope), many samples are much harder than one would expect from only their phosphorous content, andfew are softer. That could only mean that
there was no appreciable precipitation of Fe3 P, andthere must be additional hardening, probably because some carbon was also present and cementite hasformed.
The data from Thiele and Hosek (matched in scale to the data of Rubinson) agree in general terms but not in detail,Iron, Steel and Swords script - Page 265

showing once more that things are complex.
Whatever, while a hardness around 200 is not breathtaking if you think about the cutting edge of swords, it isrespectable and quite sufficient for many other steel uses. The ancient smiths must have been puzzled no end thatsome initially hard steels could be further hardened by quenching but not always. Well, if an initial 200 hardness
was due to phosphorous and not to carbon, quenching cannot produce martensite and thus extreme hardness.
So no Fe3P precipitates in all the samples above?. That could well be the case. The precipitation of phosphorousis difficult because it has to happen at relatively low temperatures. We might establish a "no Fe3P precipitates" ruleat this point. In fact, Samantha Rubinson, while spelling out "phosphoric iron" a few 100 times in her thesis, never
ever mentions Fe3P precipitates.
But we should be careful about generalizations. Buchwald has encountered old steel that did contain iron-phosphideprecipitates (and thus was rather soft for its phosphorous concentration). Here is the relevant picture:Iron-phosphide precipitates in old steel
SourceThe little black dashes are iron-phosphide precipitates according to Buchwald. Why that exception to the "no Fe3P
precipitates" rule? Well, maybe that sample has gone through some annealing that just happened to be perfect for
inducing precipitation. Maybe most of the precipitate growth happened in the 1000+ years the sample was hanging
around at room temperature? Maybe those "little black dashes" aren't Fe3P precipitates but some stuff containing
arsenic? (Buchwald couldn't yet know about that possibility).
Your guess is as good as mine: We need to wait until more research clears up the topic.
What about arsenic steel? Is there such a thing as iron with (almost) only arsenic (As) as alloy element? Well - notquite. Samantha Rubinson did find a few pieces with high arsenic concentrations of up to 1 %, but always mingledwith the other stuff. She figures that it was in there unintentionally - in contrast to phosphorous.
So arsenic is not interesting? Note quite so. We will encounter it again in the context of the so-called "white weldlines". This is another still mysterious topic that needs elucidation.
All things considered, we do not need to be overly worried about arsenic in iron. One must keep an open mind,
though.
Why is phosphoric steel more corrosion resistant? Because it is more homogeneous than carbon steel. There areno cementite particles sticking out into the surface that can't be covered by a passivating oxide. In addition, somecorrosion inhibiting phosphates might form as outlined before. Note that phosphoric iron is not "stainless", it justrusts slower than comparable carbon steel. The practical consequences may have been considerable, however.
No big mystery here - although the details are far from clear.
As the last point, we need to consider the "whiteness" of phosphoric iron or "silvery iron" as it was sometimes
called according to Samantha Rubinson. All I can tell you is that I know a lot about why materials appear more orless colored if viewed with normal light, that it can't be explained in simple terms, and that I do not have a clear idea
about how a little bit of phosphorous changes the appearance of a piece of iron.
Of course, you never look at a piece of iron but always at a piece of iron covered by some thin layer of oxides.
These oxide influence the "color", the appearance to the naked eye. So maybe the oxides on phosphoric iron are
different from those on regular steel an "make" the silvery-white appearance? I have a clear answer to that: I don't
know.

Iron, Steel and Swords script - Page 266

All things considered, phosphoric iron has quite a lot going for it. It has two big disadvantages, however:
1. It promotes brittleness, in particular cold-shortness.
2. It does not allow high hardness levels since no martensite can be formed.
The second point is not a problem for many applications but cold-shortness is. Or is it?
To be sure: phosphorous does cause cold-shortness and the "silvery iron" or whatever else it was called in ancient
times was known to become brittle when cold. At least most of the time. We are allowed to wonder, however, if there
might have been ways to make phosphoric iron from some bloomeries, containing slag particles and a little bit of thisand that, less brittle than the "common" variants if treated "right"?
If we look into cold shortness scientifically, and into the influence of small amounts of impurities and alloy atoms, wefind that we look into an extremely complex issue. Phosphorous causes extreme cold-shortness and parts of themechanism behind that is its tendency to precipitate into grain boundaries. Avoid that and you get non-brittle or ductile
phosphoric iron?
To quote S. Rubinson once more: "In most archaeological artifacts there is no evidence of brittleness in thephosphoric iron microstructure ... . Vallbona (1997) suggested that this was the result of the presence of slag".
Maybe the ubiquitous slag particles in bloomery steel are good in this case? Hard to know because modern steel
that is typically used for experiments does not have slag inclusions. Well, modern phosphoric iron has a champion
on its own, E. Balasubramaniam , who we have met not that long ago. He looked into the issue in some detail: "Inorder to understand the possible method by which the ancient blacksmiths overcame the problem of embrittlementin phosphoric irons, a very careful study of the microstructures of several ancient Indian irons (dating from the 5th
Century AD up to the 19th Century AD) was undertaken."I give you the whole 2003 paper in this link.

Enough! Throughout the history of iron up to modern times, phosphorous in steel has provided for much trouble but wasnevertheless extensively and deliberately used.
The last word to that topic needs yet to be spoken!

1)Ádám Thiele and Jirí Hošek: "Estimation of phosphorus content in archaeological iron objects by means of optical
metallography and hardness measurements", Acta Polytechnica Hungarica, after 2012 (no more data given)

Iron, Steel and Swords script - Page 267

9.5 Cast-Iron

9.5.1 General Remarks
Cast-iron seems to hold no interest for connoisseurs of sword blades. Well, yes - but wootz steel, with a carbon content
around 2 %, is just at the edge of what one usually associates with cast-iron: steel with a carbon content of 2 % toabout 4,5 %.
That's why I will give cast iron a quick look. Let's see what we can learn with respect to sword blades.
Having made it so far, you are now chomping at the bit and ready for a quick look at the relevant part of the phase
diagram. Here it is:Iron - carbon phase diagram with the cast-ironpart.

Let's make two things absolutely clear before we start:
1. Cast-iron is not (pure) iron that has been cast as a liquid into some mould but an iron alloy!
2. There is no such thing as plain carbon cast-iron! Carbon is always the major alloying element in cast-iron but
there are always others, too.
Having made that clear I will from now on write cast iron without a hyphen, like everybody else. There are two basic
kinds of cast iron and it is important to make this distinction:
1. The liquid stuff that comes out from a blast furnace (or any other furnace if it gets hot enough). This kind of castiron is also know as "pig iron" and contains all kinds of "dirt" besides a high carbon concentration.
2. Some intentionally engineered iron alloy with a low melting point and thus always with > 2 % carbon as one ofseveral alloying elements.
The first kind is the raw material we use for steel making since the - roughly - 15/16th century. The second kind is now a"High-Tech" material used for many demanding applications. In between these extremes is everything you can think of.
In order to get an idea of what the "cast iron" alloy family contains, let's start with the simple and purely theoreticalsituation of having iron and more than 2 % carbon in a state close to nirvana. That is what the phase diagram above
describes. This fictitious material can serve as a starting point just as well as it did for the fictitious material we call"plain carbon steel" if the carbon concentration is lower than 2 %.
First I need to make a confession: the phase diagram shown above is actually not showing the real nirvana states! All
this time I was deceiving you! Sorry - but no real damage was done so far.
So what is the truth and nothing but the truth about the iron-carbon phase diagram? Here it comes: True nirvana
states do not call for mixtures of ferrite or austenite and the iron carbide (Fe3C) that was named cementite but foriron and pure carbon in the form of graphite.
An old science module actually contained all of that. It also shows the true iron-carbon phase diagram, and if you
activate the link you see that it hardly differs from the "untrue" iron-cementite phase diagram.
The point of all this is:Iron, Steel and Swords script - Page 268

There is never graphite in steel.
There might be graphite in cast iron.

As long as we have low carbon concentrations, or (plain carbon) steel in other words, it is always cementite that forms
first. It is only metastable, yes, and should eventually decay into graphite and iron. But it will not do so in your or mylifetime and that of our descendants; just like our diamonds.
For high carbon concentrations, i.e. cast iron, this is different. We might find graphite instead of cementite in there, inparticular if some other elements like silicon (Si) are also present.
Allright - now let's look at the phase diagram in the 2 % carbon - 6.67 % regime and go with cementite and not graphite
for a first shot. The major features are.
For a composition of 4.3 % carbon we have an eutectic point at 1.130 oC (2.066 oF). Use the link to refresh yourmemory about that. A melt with this composition will directly solidify into an "eutectic" mix of austenite andcementite. It is similar to what happens at the eutectoid point for steel, where we get ferrite and cementite. The
resulting mix in this case we called pearlite and treated it as a (pseudo) phase in its own right.
Same thing here. Solidification at the eutectic point produces a mix of austenite and cementite, and we treat that asa (pseudo) phase. We call that pseudo-phase ledeburite , after Adolf Ledebur, an eminent German iron and steel
engineer and scientist in the second half of the 19th century. Ledeburite might be expected to form the typicaleutectic zebra pattern but that is not what it does. The zebra pattern forms because repartioning the carbon (or any
other element) is difficult at lower temperatures. It is not all that difficult when a liquid solidifies. We might rather
expect dendritic structures in this case. Whatever - nobody has ever seen ledeburite directly because it only exists
at high temperatures.
So far so easy. But now we decrease the temperature to below the transformation temperature at 723 oC (1333 oF).
What will happen? Well - the phase diagram does tell: The austenite (γ) and cementite mix that we call ledeburite
transforms into a pearlite - cementite mix.
Only the austenite needs to transform into pearlite or ferrite plus cementite. The primary cementite already present
at high temperatures in the ledeburite need not do anything. We still call the pearlite - cementite pseudo-phase that
we get a low temperatures at 4.3 % carbon concentrations ledeburite or, if you are a stickler for details,
transformed ledeburite or ledeburite II (the high-temperature variant is then ledeburite I). We might expect
pearlite grains embedded in cementite since the mixture is cementite-rich.
What happens if we are not at the precise eutectic concentration of 4.3 % carbon? What always happens: for lower
carbon concentrations ("hypoeutectic") we have a decomposition into pearlite and ledeburite II, and for higher
concentrations ("hypereutectic") the decomposition produces ledeburite II and cementite. That is a bit academic,
however. We know already that what you get depends very much on how fast you cool.
If we cool not all that slow, the transformation of the austenite into pearlite becomes difficult and we encounter all
the phenomena we found for steel (and possibly some more). With increasing cooling rate the pearlite gets narrower
and less well developed, and eventually we find bainite. For very large cooling rates we might even get martensite.
Contrariwise, for very slow cooling and high carbon concentrations we might now encounter the real nirvana
structure, which is not cementite but graphite - see above.
So what does ledeburite II look like at room temperature? If we cool slowly, we would expect pearlite grains, developed
from the primary austenite and embedded in the primary cementite. Why should they be embedded? Look at the carbon
concentration. A pure Fe - 4.3 wt% C alloy corresponds to about 18 at % carbon. Since every carbon atom binds threeiron atoms to form cementite, 54 % of the remaining 82 % iron atoms are used up and we have only about 30 at %"free" iron left in a ledeburite eutectic. Most everything is cementite and that's why we expect the ferrite to becompletely embedded in cementite.
Ledeburite types of cast iron, or essentially pearlite embedded in cementite, will fracture right through the cementite,
giving the fracture surfaces a whitish appearance. That's why this kind of cast iron is called white cast iron.
It is not easy to find good microstructure pictures of eutectic pearlite- cementite ledeburite II. The reason is simple
and mentioned above: there is practically no such thing as a pure Fe - 4.3 wt% C alloy, slowly cooled.
Here is the best picture I could find:Iron, Steel and Swords script - Page 269

Microstructure of white cast ironSource: Internet article of Miguel Angel Yescas-Gonzalez and
H. K. D. H. Bhadeshia; from the PhD thesis work of Miguel Angel
Yescas-Gonzalez. With friendly permission.

We see a cut through an original austenite dendrite that has turned to pearlite. It is embedded in whitish cementite.
In addition we have small flecks of pearlite because the sample actually had a carbon content of 3.6 % carbon (and0,1 % silicon) and thus was hypoeutectic and needed to form some more pearlite
Two properties of (about eutectic) "white cast iron" are quite clear:
1. It is perfectly brittle! With a contiguous matrix of brittle cementite it just can't help that.
2. It has the lowest possible melting point of all iron-carbon, or better iron-cementite alloys. The stuff melts at amere 1130 oC (2066 oF)!
It actually has the lowest melting point of pretty much all iron alloys for low alloy element concentrations in the %range. I haven't checked all 80+ possibilities but I am rather sure that you will not find an "easy" iron alloy with alower melting point. And that's why cast iron has been and still is of large technical importance:

Cast iron can be easily cast!

Big surprise! Cast iron allows for easy casting!. That's why this alloy is called "cast iron", meaning "castable" iron, after
all. But seriously: the melting points of gold or bronze / brass are 1064 oC (1948 oF) and (1000 - 900) oC ((1832 - 1652)
oF), respectively. If you can handle that, you can, with a little bit more effort, also handle cast-iron. Provided of coursethat you can make the stuff.
The ancient Chinese, it seems, were the only ones who could produce cast iron some 2 500 years ago and foundways to use it. They used it to make plowshares, pots and art plus a few weapons on the side. In the West, castiron could be made rather early too, but it wasn't used much before the 15th century. Cast iron was used (of course)
for making cannons, cannon balls, and lots of other stuff. In 1390 the first recorded casting of a cast-iron cannon
took place in Frankfurt/Main, Germany. More to that later.
The low melting point is certainly a huge advantage. But the stuff is brittle and that is a disadvantage. Brittlenesscertainly limits applications - no sword blades, for example - but it doesn't prevent them completely. Natural stones,
glass or concrete are brittle too, but quite useful for making pyramids, windows, microscopes or huge bridges with the
stuff. Your toilette seat is perfectly brittle but can take a lot of punishment! Why? Because while those materials cannot
take tensile (pulling) stresses very well, they have no problems with compressive (squeezing) stress. Same for castiron.
Besides engineering your cast iron product for mostly compressive stresses, there are two more ways to deal with thatunwanted brittleness:
1. Make your cast iron parts massive. Cannon barrels, bath tubs, stove parts, whatever. If they are massive enough,Iron, Steel and Swords script - Page 270

1.
they can take some tensile stress, in particular if is is not concentrated on a "point". Take a thick glass window.
When you hit it with a hammer (point stress), it might break. But try to break it by pushing with your hand! You
can't.
2. Do what Material Scientists always do to improve properties: mix in this and that, and optimize processing. In
other words: don't use a pure Fe - C alloy but add some more beneficial elements. Then cool slowly, quickly or
run a temperature profile - whatever works best.
The first point is rather trivial and you can see how it's done whenever you look a some cast iron object. Hint: lookdown when you walk the street or watch your wife when she uses that special heavy pan.

Cast iron man hole cover in Copenhagen.

In Copenhagen the elephants symbolize beer, of course (look up "elephant beer"
yourself). We know that iron technology and beer always goes together (casting makes
you really thirsty), inspiring the Copenhagians to produce gully art. The artist evenappreciated that the bulk intake of beer produces certain needs; just look at thedetails.
Generalizing a bit, we note that all cast irons have low melting points, allowing for easy
casting. And almost all are brittle. There are other good points, too, that all cast irons shareto some extent:
Cast iron is dirt cheap! There is no metal or anything else with comparable properties
that is as cheap as (unsophisticated) cast iron. It could replace expensive brass inmany applications, especially in early steam engines. Whole bridges were made fromthe stuff in England as early as 1770.
Cast iron is rather hard and thus resists deformation. That makes it a good material for
structural applications where large (compressive) forces / stresses are encountered.
For the same reason it has an excellent wear resistance.
It hardly rusts - in contrast to most steels. That is quite remarkable and extremely useful.
Some cast irons (not white cast iron) have an excellent machinability - even so you need to be a bit careful about
that.
What will alloying and processing do for us with respect to these (and other) properties? A lot, to be sure. There arealmost limitless possibilities and I will not go very deep into this. All I'm going to do in the next sub-chapter is to lookbriefly at grey cast iron and some modifications of that extremely potent material.

Iron, Steel and Swords script - Page 271

9.5.2 Kinds of Cast Iron
Grey Cast Iron
The main alloying element besides carbon in cast iron is silicon (Si). It stabilizes graphite and also improves some otherproperties (see below).
All the dirt that is contained in the primary "pig iron" may still be there too, in particular our old acquaintances sulfur (S)and phosphorous (P). Some manganese might have been added to take care of the sulfur in the usual way. Carbon is
the important element and, as in steel engineering, one sometimes defines a carbon equivalent concentration [Ceqi] by[Si] + [P][Ceqi] = [C] +3
A high cooling rate and a low carbon equivalent favors the formation of the white cast iron I have introduced in thepreceding sub-chapter. It is the cheapest and simplest variety of cast irons. Since it is very wear resistant, it finds
applications in, e.g., slurry pumps, ball mills and grinding mills or for the teeth in a backhoe's digging bucket.
More interesting, however, is grey cast iron. It tends to be formed for slow cooling rates and high carbon equivalents
because this allows to get closer to equilibrium and thus graphite is formed instead of cementite. Graphite has no
mechanical strength to speak of, and grey cast iron behaves mechanically like iron with voids or microcracks instead ofgraphite. That causes cracks to go through the graphite inclusions. They are also deflected, and fracture surface isrough and looks grey because a lot of graphite is exposed - hence the name.
The graphite forms already in the high temperature region, together with the austenite. Upon cooling the austenite
either decomposes into pearlite in the usual way, producing a ferrite - cementite mix, or, for very slow cooling rates,
into ferrite and graphite. In the latter case this secondary graphite just enlarges the primary graphite inclusions
already there.
Here is what pearlitic grey cast iron looks like:

Microstructure of grey cast ironSource: Internet article of Miguel Angel Yescas-Gonzalez and H.
K. D. H. Bhadeshia; from the PhD thesis work of Miguel Angel
Yescas-Gonzalez. With friendly permission.

The dark longish objects are the graphite flakes. They typically precipitate in this kind of rather stretched-out shape.
In between one can just see the pearlitic structure of the matrix. If one considers the graphite flakes to have no
mechanical strength, they essentially are nothing but microcracks that initiate fracture at the slightest "provocation".
Grey cast iron thus is rather brittle, even so the stuff between the flakes is good pearlitic steel. It is, however, lessbrittle (and hard) than white cast iron.
Grey cast iron is the most commonly used cast iron and the most widely used cast material based on weight. Most
variants have a chemical composition of 2.5 % to 4.0% carbon, 1 to 3% silicon, a little bit of this and that, with theremainder being iron. More that 35 million tons are produced every year. It is clear why - consider the list of properties:
Low cost.
Good castability in general and in particular because the silicon increases "fluidity" when casting.
Iron, Steel and Swords script - Page 272

Good hardness.
Good wear resistance, to some extent because the graphite flakes act as lubricant. "Galling", the sticking
together of two metal parts "rubbed" very hard, does hardly occur.
Good corrosion resistance in general and in particular if it contains silicon.
Very good machinability since the bore chips or flakes come off easily due to the graphite.
Excellent damping capacity because the graphite absorbs energy, e.g. from vibrations.
Less solidification shrinkage than other cast irons / steels because the graphite does not shrink much.
Easy to weld.
But: Low tensile strength and ductility and therefore not much impact and shock resistance.
Obviously, we now must ask ourselves if we can do something about the last bad point? Having progressed that far
in this Hyperscript, you should be able to have some ideas in this respect. No??? Read on and learn. Yes!!! Readon and see if your ideas would work.
Grey Cast Iron with Spheroidal Graphite.
The brittleness of regular grey cast iron results mostly from the sharp-cornered microcracks supplied by the the (often
interconnected) graphite flakes. If one could find a way to render the graphite spheroidal with no sharp corners, the castiron should be far less brittle and even somewhat ductile. How could one do that? There are two more or less obvious
ways:
1. Add something to the mix that hinders the graphite to form flakes.
2. Anneal at sufficiently high temperatures to allow the graphite to assume the thermodynamically much better
spherical shape.
If you go for the first point, it helps to figure out why graphite tends to precipitates as flakes (or, if considered threedimensionally, as "rosettes"). It might come as a surprise that this is a hotly debated topic in polite scientificcircles. Details thus are "complex" (meaning: not so clear even to experts) but don't matter here. The question is:
how can we prevent flaky graphite? The answer is: add minute quantities of magnesium (Mg) or cerium (Ce) or .... (?
) and the graphite inclusions grow more or less isotropically into spheres. Why? I don't know.
That's what it looks like:

Microstructure of spheroidal grey cast ironSource: Internet article of Miguel Angel Yescas-Gonzalez and H.
K. D. H. Bhadeshia; from the PhD thesis work of Miguel Angel
Yescas-Gonzalez. With friendly permission.

What we see are featureless round graphite particles, dark pearlite grains, and whitish ferrite. The sample is an ascast 3.5 % C, 2.5 % Si, 0,5 % Mn, 0.15 % Mo, 0.31 % Cu and 0.042 % Mg cast iron mix. The small amount of Mg
is decisive for the spheroidal shapes of the graphite.
Note that the graphite particles are always surrounded by a ferrite fringe. That simply happens because duringcooling they "suck out" the carbon that is contained in the pearlite / cementite that happens to be in theirneighborhood, leaving back the ferrite and a somewhat larger graphite particle.
Spheroidal graphite cast iron has much better mechanical properties than the normal stuff. Its ductility increases atleast five-fold if not twenty-fold compared to flaky-graphite cast iron, with all the other good properties not much affected.
In essence we now have a ferritic / pearlitic steel with spherical pores, and the properties of the steel become important
for the properties of the composite.
That should give you plenty of ideas - we know what we can do with steel, after all.

Iron, Steel and Swords script - Page 273

For example, we might expect that annealing the stuff shown in the picture above would allow the spheroidal
graphite particles to suck more carbon out of the cementite that is still present in the remaining pearlite. Ultimately
only ferrite and graphite should be left. That works; what you get looks like this:Microstructure of annealed spheroidal grey castiron
Source: Internet article of Miguel Angel Yescas-Gonzalez and H.
K. D. H. Bhadeshia; from the PhD thesis work of Miguel Angel
Yescas-Gonzalez. With friendly permission.

It's the same sample as shown above; it just was annealed some time (precise conditions unclear). No pearlite isleft; we now have graphite particles embedded in (relatively soft and very ductile) ferrite. You can clearly see that theoriginally rather spherical graphite particles have surrounded themselves with somewhat irregularly shaped annexes- the carbon sucked out from the cementite.
This kind of ferritic spheroidal grey cast iron is no longer brittle but rather
ductile, as shown on the right. You can even twist it and forge a pattern-weldedsword from it.
But would you want to do that? Maybe not, because the material now is ductile
but not hard. So use all the tricks you know for hardening steel, For example,
produce a hard bainitic matrix structure by employing the "austempering"
concept used so successfully for regular (carbon) steel. Or try whatever else
has worked for hardening steel.
You realize, of course, that I have just opened a huge treasure chest or a very large
can of worms, depending on how you look at the matter. There is no end to
optimizing cast iron now. It is safe to predict that we are going to see more andmore advanced kinds with specific properties.

Ductility of ferritic
cast iron

The catch, equally of course, is also obvious. It's no longer a simple and dirt-cheap material. That's because themore sophisticated our alloying becomes, the more you must avoid useless or detrimental dirt. And annealing
always costs money anyway.
At the end, let's go back to the beginning. How about making swords from cast iron?
Well, the need for good but affordable sword blades has sharply declined before "high-tech" cast iron came into being
and nobody has tried what one could do. I wouldn't be surprised., however, if good blades could be made nowadays byusing some optimized cast iron. Blades possibly better than what our ancestors could make - but not as good as
blades from modern steel.

Iron, Steel and Swords script - Page 274

10. A Short History Of Metals
10.1 Copper - First Metal in Ancient Times
10.1.1 Discovering Metals
10.1.2 Native Copper
10.1.3 Smelting Copper - The First
10.1.4 Smelting Copper - The Second
10.1.5 Copper Final

10.2 Making Iron
10.2.1 Early Iron
10.2.2 Smelting Iron
10.2.3 Smelting Wrought Iron, Steel and Cast Iron
10.2.4 Bloomeries

10.3 Iron and Steel in Early Europe
10.3.1 Technology Transfer
10.3.2 The Iron Trade

10.4. Crucible Steel
10.4.1 The Making of Crucible Steel in Antiquity
10.4.2 Making Old-Fashioned Crucible Steel in Modern Times

10. 5. Iron and Steel in "Modern" Europe
10.5.1 From Bloomeries to the Blast Furnace
10.5.2 Making Steel up to 1870
10.5.3 Making Steel after 1870
10.5.4 Making Steel Things

Iron, Steel and Swords script - Page 275

I turned to PBS and watched some thing called"History of Metallurgy".
It was actually quite interesting but
I fell asleep before it ended. 4)

10. A Short History Of Metals
10.1 Copper - First Metal in Ancient Times

10.1.1 Discovering Metals
The Problem of Finding the "Truth"
First a word of warning! I will not give you an authoritative account of when and how
humankind discovered the various metals and alloys that it has been using ever since. I
simply don't know the truth and nothing but the truth about that. I have read a tiny little
bit of what others have to say - a few hundred articles and books - and I know a bit
about the archaeological evidence by roaming around in museums. Reading all that has
been written about the topic would not only need several lifetimes, it would also be amajor waste of time since a lot of what has been written is obsolete.
A kind of short and naive version of what is to follow can be found in the early module
shown on the right.

Advanced
Link
The Ages

The history of metals is muddled to some extent because it is messily entwined with the history of archaeology and thehistory of science. Only archaeology can unearth the truth about the history of metals by digging up relevant artifacts,
and only the modern science of solids can make sense of those artifacts. The trick is to get the two together.
You may wonder that archaeology has a history. Didn't people everywhere and at all times have some interest in thepast and in whatever artifacts that were around and could not be overlooked? Yes, but what I'm alluding to here is"scientific" archaeology, or digging for knowledge and not for finding treasures, art, literature or justifications for yourreligious believes. "Scientific" means that those archaeologists dig for finding out how all the people lived (not just therich / nobility), what they did in the period in question, how they developed, and what kind of parameters influenced theirdevelopment. And so on.
The first scientific diggings or excavations in that sense took place in 1748 in what used to be the old Roman townsof Pompeii and Herculaneum. That was done just fine but not really scientifically - because science was still in its
infancy. The archaeologists then could not have identified a steel object because they simply did not know whatsteel is.
A little later, some specialists or early scientists marched along with Napoleon's army from 1798-1801. The emperor
then invaded Egypt for not immediately obvious reasons, and his civilian followers did some digging and exploring
there. This culminated in Jean-François Champollion deciphering the Rosetta stone, enabling the reading of
hieroglyphics, and thus establishing the thriving field of Egyptology. The rosetta stone, by the way, is now in the
British Museum in London because British troops, invading Egypt for not immediately obvious reasons either,
defeated the French in Egypt in 1801 and took whatever they could grab (nobody asked the Egyptians, of course).
The British also destroyed Copenhagen in 1801 for some reasons of their own, and they are still proud of all that.
Also in the beginning of the 19th century, in a kind of team effort, cuneiform was deciphered, opening the way forlooking deeply into the ancient mesopotanian civilizations and for learning about the importance of beer.
The first major excavation conducted along what one could call scientific principles (the catch word is "stratigraphy")
was that of of Hissarlik, the site of ancient Troy. It was started by Heinrich Schliemann in 1871, a German "amateur",
who was fought and ostracized by the professionals That hasn't changed, by the way. The majority of professionalarchaeologists still consider any "amateur" (like me) to be an unmitigated nuisance.

Iron, Steel and Swords script - Page 276

Part of the Rosetta Stone
Source: All over the Internet

To be sure, deciphering hieroglyphics, cuneiform, and so on is a highly scientific enterprise. Without some experts
being able to read and understand the old texts, large parts of archaeology would not get very far. It is thus clear thatscientific archaeologists in the 19th century were highly trained in the "humanities". It takes some dedicated long-timeeffort to become familiar with ancient dead languages and their weird scripts. You can't blame those old guys for not
spending much time for learning a bit about physics and chemistry after they had learned hieroglyphics or cuneiform(besides, of course, Latin, Ancient Greek, some Hebrew, French, German or English). It wouldn't have helped muchanyway, because before the end of the 19th century the knowledge concerning metals wasn't at a level where it would
have been very useful.
A "classical" 19th / 20th century archaeologist thus had a strong tendency to answer technical questions in theway that came naturally to him:
1. Find out what the ancient Greeks had to say about the topic. If they had recorded something - that's it. Steel,for example, is then particularly pure iron.
2. If the old Greeks are mute: is there anybody else, preferably Roman, halfway prominent and long since dead,
who had an opinion on the topic? If yes - that's probably it.
3. If there isn't anything or only obvious crap: Sit down, think hard, and publish the results of your thinking as
the answer.
What you will never ever do is to conduct experiments. You have seen on wall pictures in old graves that a granite
block is hollowed out by something that could only be a hollow copper drill plus stone "hammers". So that's how it
is done. There is no need to try experimentally if that is actually possible or how long it would take to make adecent sarcophagus. You also don't analyze King Tut's iron dagger to see if it was really made from meteorite ironbecause the old Egyptians referred to the stuff as "metal from heaven" so it must be of meteoric origin.
This has changed in the last 30 years or so. "Archaeometallurgy" established itself as a new interdisiplinary field andthere is a rapidly increasing number of papers dealing with thoroughly analyzed metal-related artifacts, resulting in abetter and better understanding of the development of metallurgy in different parts of the world.
Interested laymen like you and me profit from that - but we also have a problem.
We do not like to read learned papers, published in arcane and hard-to-get
archeological journals, describing just some tiny detail concerning the history ofiron, steel and swords. We neither have the time, the required prior knowledge, nor
the incentive to construct the big picture ourselves from all those small mosaic
stones.
We rather like to look at objects in museums , learn the interesting points from thedescription there, and then possibly buy the general book going with the exhibitionin the museum shop, hoping that it would provide the perspective we are after.
The problem with that approach is that we invariably get:

Link Hub
CriticalMuseumGuide

1. Far too little information, and2. Quite often misleading if not completely wrong information.
3. No museum book in many museums.
While this is deplorable, it can't always be avoided. Museums cannot change exhibitions frequently, and much of
the doubtful explanations you get were put there many years ago. It is quite possible that people then just didn't
know better.
However, when a completely new exhibit is designed in our present times, with great labor and cost (example:
Iron, Steel and Swords script - Page 277

"Türkische Cammer" in Dresden; see the picture below), or when some special exhibit is made "to order" (example:"The Celts" in Stuttgart), the partially hair-raising nonsense encountered there with respect to metals is inexcusable.
That's why I have started the critical museum guide accesible in the link above. The picture below illustrates what I
mean.

Tip of the Dresden Zulfiqar
The picture shows the Dresden copy of the "Zulfiqar", Prophet Mohammed's bifurcated sword, quite famous in the
Muslim world, as envisioned by "professionals". This is utter bullshit, of course. But zulfiqar renditions like the one
above have a history of their own, and it would have been quite interesting to learn about that in the in the museum.
Museums and their exhibition catalogues are not the only problems encountered whensearching for "the truth". Go and google for some general topic like "first use of copper"or, if you want to be more specific "Cayönü Tepesi and copper" or "Luristan ironswords". You find lots of articles from all strata of interested sources. Crackpots, tourist
agencies, and interested laymen let you have their materials, professor's teachingmaterials can be found, blogs from all kinds of people (including archaeologists orexperts in related fields), master and PhD theses, and the occasional freely accessible
paper from a real scientist.

Illustr. Link
Confusingthe issue

What you rarely find are the original sources: papers or books with pictures and explanations from the excavators or firstinvestigators. What you find will tend to confuse you (see the link for a few examples).
If you look for pictures, you are in for a disappointment. Try to find a picture of the famous and celebrated first
copper objects found in Cayönü Tepesi. You won't. And if you happen to find something, do not automaticallybelieve that it is really what it claims to be. There are many mistakes!
Now I can get back to the beginning of this chapter. I can't give you an authoritative account of when and how
humankind discovered the various metals etc., because nobody can. First of all, in different areas of the globe, thehistory of metals is typically quite different. Second, much of what was supposed to be solid knowledge is now being
challenged, and the final word hasn't always been spoken yet. Read A. Haupmann's rather recent book - it is presently
one of the "last" words on the subject. It dedicates a lot of space to refuting views of others, and to point out the many
white spots on the metal history "map".
I'm not the only one with that kind of problem. The eminent scientists Sherby and Wadsworth, whom we willencounter as soon as I get finally around to swords, got so fed up with the prevalent beliefs about the history ofmetals in the archeological community at large that they wrote a full paper2) , proposing that the iron age not only
precedes the bronze age but may even go back to Neanderthal times, i.e. to 300.000 BC - 40.000 BC. Sherby andWadsworth are serious scientists and not crackpots, and while they may have a point; I don't subscribe to it.
Talking about crackpots, and just to be on the safe side, I want to make one thing very clear: I certainly do notcount the various claims of all those people that believe in more unorthodox things - for example that early
metallurgy goes back to some aliens that long ago visited the earth - as real challenges to the mainstream historyof metallurgy. But I do not call all of them crackpots, however. Some of them did raise valid points on occasion. I
have researched the "alien hypothesis", together with other science students for quite a while after von Däniken
brought it up (once more) in the seventies. My conclusion was simple: It's not impossible that aliens visited theearth long ago, just very unlikely. The evidence provided, while stunning on occasion, does not really support theclaims made. Nothing in the last 30 years has happened to induce me to change my opinion. Sorry about that. I
would have liked the alien stuff much better.
What I am going to do is to look at the discovery of metals and metal technology by humans not along the time-honored
but questionable system of "The Ages" (like stone - bronze - iron age) but along the more natural lines of:Forging of native metals.
Carbon smelting of "Easy" Metals, producing liquids.
Casting and producing alloys
Carbon smelting of iron, producing a solid "bloom".
Electro-smelting of "difficult" metals.
It's a slight variation of the system proposed long ago in an advanded module in chapter 2. But now you haveadvanced your knowledge about metals and material science quite a bit, and I can now look at all this stuff righthere in the backbone.
I will look at the first point in the remainder of this sub-chapter: the discovery of elemental or native metals, and thefirst simple techniques to turn them into pretty or useful objects. I will plagiarize myself heavily here, using what I havewritten earlier in the links you are by now familiar with.
Iron, Steel and Swords script - Page 278

Working with Native Metals - or Possibly Not?
Stone age woman did not just make flintstone tools. She also painted art on the wallsof her cave some 15.000 years ago, and long before that - 30.000 to 40.000 years ago she made complex ivory sculptures including a figurine known as Venus of the "Hohle
Fels" (hollow rock). And he or she made music. With flutes from bird bones. At least if
she lived in what is now Suebia in South Germany, the area where I was born.
I can't resist the temptation to claim several "firsts" for my early countrymen; use thelink for details.

Illustration
Link
SuebianthingsWhat I'm driving at is: given all this sophistication more than 30.000 years ago, it appears to be likely that those people
would also pick up those pretty yellow or brown-green-reddish "stones" - gold (Au) or copper (Cu) nuggets - that theyencountered here and there, and then make something from it. Just as well we can assume that they picked up any
pretty stone or object, and made something like jewelry from it. Just for fun. Or for averting demons and evil eyes. There
are no other uses for gold, copper and pretty stones, sea shells and so on. These things are not directly useful foreveryday life, like making survival easier.
Indeed, serious archeometallurgist from institutions like the British museum and major universities are convinced thatmetallury did not come into being from a need to use metals: "We will show that metallurgy derived from the desire (...)
to adorn the human body by using colorful (copper) ores and naturally occurring metals. It is only in the subsequent
millennia that that the application of heat in a controlled reducing atmosphere led to the smelting of metallic ores to
produce lead, copper, copper alloys and eventually silver", they write. Sorry - forgot which one exactly.
The desire to adore the human body is certainly very old, The "Sungir" people, living not far from what today is Moscow,certainly were into strings of (bone) beads to adorn their dead, and very likely also their living bodies, a long time ago:

Sungir burial, 28 000 to 30 000 years old,with lots of strings of bone beads
Source: Public domain; all over the Net.

From that reasoning it follows that the earliest metals used by humans should benative gold and copper for making adornments and jewelry. Well, that follows
indeed - it just ain't true! The oldest gold artifacts (adornments, indeed) known atpresent are from Varna in present-day Bulgaria and go back to only
4.560 BC - 4.450 BC. Copper artifacts, for comparison, go back to about
8.000 BC!
The Varna Necropolis, accidentally discovered in October 1972, is a burial sitethat is internationally considered to be of prime importance for understanding
world prehistory. It belongs (surprise!) to the "Varna culture" (sometimes also
referred to as Thracian, even so Thracians proper came much later). The present
day viewpoint is to see the "Varna culture" as the culmination or the end of themuch older "Alteuropäische Kultur" that I will call "Danube culture" since the"official" English version is "Neolithic Europe" which is not a good name since the
Danube culture most likely invented metallurgy and thus was not (neo)lithic, i.e.
stone tool based.

Iron, Steel and Swords script - Page 279

Advanced
Link
DanubeCultureSome Varna graves contained a lot of the oldest gold artifacts unearthed so far. They also contained copper
objects and much more. Grave No. 36 contained by far the richest find of highly sophisticated objects of great value
from that long ago. To put it in perspective: The pyramids in Egypt were built 2.000 years later (with copper tools);
King Tut was laid in his grave 3.000 years later, the Jews bewailed their fate as prisoners in Babylon 4.000 years
later, and Jesus was nailed to the cross with iron nails 4.500 years later.
Gold in Varna was used for jewelry and adorments (including giving some lustre to a very male part of the anatomy),
while the copper in Varna was used for tools and weapons. Interestingly enough, there are no swords or daggers
among the Varna objects.
Large pictures of some of the treasure can be found in this link. Below are a few details

Details of Varna: gold, copper axe (upper left)
andgreen-stone axe (lower right)
Source: All over the Internet

We see gold and copper objects plus highly polished and perfected stone tools. The gold stuff is only ornamental
but the copper pieces (axe heads) are tools or weapons. More regular-sized pictures of the Varna gold can be foundin this link. While the gold is for sure native gold (pretty much all gold is), the copper must come from smelting. It
probably signals the point in time and space when serious smelting of copper started.
The Varna metals are a good starting point for asking some of the big questions that come up for any "old" metal.
Before I start, let me give you a piece of warning: It's easy to ask big questions. It is not so easy to answer them. In
fact, one point of the exercise I am about to lead you through, is to make perfectly clear why there are no easy answers
to supposedly simple questions.
First and foremost we want to know:

1. Were the old Varna people thefirst ones that used gold
about 6 500 years ago?
The first answer is: It looks like it - so far! But nobody really knows. Maybe sometime in the future an even older
place with gold artifacts will be found. Or maybe no such place will be found because there isn't any. That might be
so because older cultures and people did not use gold, or because it was recycled and re-used. Gold was more
plentyful in ancient times but still rather rare and therefore always precious. It can also be re-shaped very easily - incontrast to all those far older ivory or stone sculptures or anything ceramic. Graves were robbed for almost sure if
there was a chance that they contained gold objects but rarely if all they contained was a bit of pottery and some
flintstone tools.
Personally, I was inclined to believe that gold was used in areas where you could find sizeable nuggets of the stuff
long before the Varna culture people put it in graves (which, amazingly enough, were not robbed). That excludes a
lot of places (for example the romping grounds of those advanced old Suebians 30 000 years ago) but leaves quite afew. I can neither prove this claim nor can you or anybody else disprove it. At the moment it's a matter ofIron, Steel and Swords script - Page 280

probabilities.
I might argue that the odds are in my favor since ancient people did use the native copper they could pick up long
before the Varna culture people put plenty of smelted copper in their graves together with picked-up gold. Why
copper and not gold? It's a good question. We don't know the answer for sure but some ideas for the copper
preference will come up in what follows.
The probability argument goes against early uses of gold. More and more ancient sites are found where copper wasused long before 4 500 BC - but never gold! We might speculate wildy and assume that gold was not seen as
something special and therefore was only collected and used long after copper was "discovered". Maybe the fashionchanged, or who knows. While there are indications that our ancient forebears did like colorful things (especially ifthey were green), it is just possible that they hated yellow. Yellow usually signals infertility, sickness or danger look at a desert, pus oozing out from a wound, or that yellow jacket about to sting you, and you get the point!

Good and bad colors 3)
The second big question is:

2. Were the Varna metal artifacts cast or hammered into shape?
The answer is: In the literature to Varna 1) there is a general agreement that most gold objects have been formed byhammering the metal into shape. If you look at all the pictures I have provided, this is all but certain for pretty muchall of the gold artifacts. It is very difficult to cast a thin foils but rather easy to hammer a gold nugget or piece into athin foil, and that's what obviously was done in making many of the pieces shown.
If we accept the hammering hypothesis for a moment (and I do not suggest that we should), the question now is:
how come many of those gold objects have the same size, considering that nuggets are typically smaller and ofvarying size? Actually, most gold is recovered as gold dust or "placer gold" by panning, so you only have very small
particles. The copper objects are also far larger than the biggest elemental copper pieces they could find. So how
do you get large pieces, and many pieces of identical size?
The answer could be: You must hammer-weld your little gold and copper pieces together to form a large piece, andthen cut off standard sizes.
Hammer-welding of gold is not addressed a lot in the literature. There are some indications that it is easy - but only
for pure gold, which native gold never is. About hammer-welding of copper I can't find anything except a few hints
that it can' be done. Rehder, for example, states that copper does not naturally weld together. It cannot be easy
without some special tricks because copper is always covered with a rather stable oxide.
I'm inclined to say: forget about hammer welding for copper and gold! For copper, hammer welding doesn't seem towork at all, and for gold, even if it should work, there is a practical problem! How would you heat fine dust and thenhit it with a hammer? Considering that your hammer and anvil was just some piece of stone?
To make a long and convoluted story short: Personally, I'm rather sure that thecopper parts were fully cast, and that the gold parts were made by hammerforging from cast ingots.
Now you might ask: "If those people knew how to cast, why not cast the gold into
the desired shape right away?" Because you want light-weighed objects withlarge surfaces, to better "show off" your gold with maximum effect. That simply
demands objects made from thin gold sheets. Doing that by hammering was
possible - but not by casting. For that you would have needed molds made with a
precision that was simply not attainable 6000 years ago.
We have a first hint that metal technology, even very early one, is far trickier than
you can possibly imagine. The link gives an idea of what it really entails.

Science
Link
Early Metal
Technology

If we surmise that this is indeed what the Varna people did with their gold and copper, one thing is clear: they musthave had some prior metal working experience, including smelting copper, melting and casting. That is all but sure.
These techniques had been invented in the general area just a few (hundred) years before the time in question, andthe Varna people either knew how to do it or knew from whom one could buy the stuff. I will come to this in somedetail in what follows.
Iron, Steel and Swords script - Page 281

That leads us to the third question:

3. Was "metallurgy" discovered in one
place at some specific time and thenthroughout Eurasia? Or was it
discovered independently in many
places at different times?
This question can be broken down into many detailed questions concerning different aspects of metallurgy. Maybe
the copper technology spread or "diffused" from one source, at least in Europe / Middle East, but iron smelting was
discovered indenpendently in many places, and so on. The "diffusion - multiple discovery controversy"
exercises archaeometallurgists mightily at present. Scientists do love a good fight, in particular if it is about someundecidable arcana.
I have no opinion myself to that topic. There is some evidence that copper / bronze metallurgy spread from places in
the middle-east outward, supporting the "single invention / diffusion" hypothesis (the link leads to an article
promoting that view), but there are also good reasons to subscribe to the alternative view. For example, the North
American "Indians" used native copper quite a bit as early as (maybe) 5 000 BC, and they did certainly not rely on atechnology transfer from the Middle East. Nor did the South-American cultures - Maya, Aztec, Inka and so on - who
did know how to make copper and bronze (not to mention silver and gold).
Needless to say: almost all Chinese are sure that everything remotely important was first discovered or invented in
China. It so happens that they are wrong as far as metallurgy is concerned. That "diffused" into China from theWest!
The fourth question is:

4. Is the Varna copper native copper or did it result from smelting
copper ores?
I have tentatively answered this question already; here I'm going to dig a little deeper.

Some Varna copper artifacts. Smelted or native
copper?
Cast or hammered-welded / forged?
SourceNote that I did not pose this question for the gold. Gold is never smelted, i.e converted from a gold compound into
the element, simply because it is almost exclusively found in the elemental state, mostly alloyed with a bit of silver
and traces of this and that. Gold was and is rather rare, and either you find elemental gold or you don't find anything.
You do not have the option of finding plenty of some gold compound that you then can smelt into elemental gold.
To confuse the topic a bit, gold-bearing rock is still called gold ore even so thisterm otherwise always denotes a chemical compound of the desirable stuff.
Of course, when dealing with gold, just picking up the large nuggets you foundwhen walking around in your backyard wasn't all there was to getting gold in
ancient times (not to mention modern times). Quite early - as far as we know something like a gold technology developed, including digging for the stuff, getting
the silver out, shaping and welding it, making gold leaf and gold (nano) powder(e.g. for making red glass), and so on.
More to that in the link.

Iron, Steel and Swords script - Page 282

Science Link
Gold
Technology

But back to copper. Copper (and practically everything else) is quite different from gold. Copper ore, meaning copper
compounds like green malachite (CuCO3(OH)2) can be found in many places and in large quantities, while native
copper is rather rare (except in parts of North America) and only found in some special locations, often together withmalachite and other copper ores. For elemental silver it is even worse.
If you consider that your ancient counter-part was not so much interested in gold (since, after it became fashionable,
his boss took it from him anyway) but very much so in labor-saving devices (like a good copper chisel, axe, fishhookor needle), it made a lot of sense to these people to develop smelting techniques, allowing them to produce copperin bulk from the local rocks. If you could do that, your boss would like you and order fancy objects like copper axes.
But he couldn't use all your copper for himself (he didn't do any work and thus didn't need real tools anyway) andyou could keep or trade some of the stuff. And even better: if you could smelt copper, lead, tin or silver, you got
melting, casting and alloying for almost free! There was a way to become rich without being the Boss! This worked
for some, at least in China.
So it only remains to sit down with the guys, have a beer or two, and invent smelting.
Ha ha. Do a time travel and go some 6 500 years back (easy if you believe in standard TV movies). Then tell those
Varna people that their precious copper stuff, reserved for their big chief, could be made from those bluish rocks out
there by sort of cooking them in a fire made from "special" wood, and that you could show them how to do this for a littleof their gold. The Varna guys would tell the time traveller: "Yes, we do know that - but do you know that you can also
make copper from green rocks?
It would be like some time traveler coming from the future, telling you that you could talk to about anybody on the globe
if you would buy his little box for a very reasonable price. You would not only believe him but show him your little boxthat could even send pictures to his girl friend, but comes much cheaper.
Sorry. Wrong century in both cases. These time travelers need to go back a few more centuries. Then nobody reallyknew how to smelt copper, and the idea that one could talk to people hundreds of miles away via a little box would havebeen totally absurd before about 1980.
Now test yourself. Do you know, what exactly kept the nerds around 1850, 1870, 1890, 1910 .... 1970 from making
a cell phone? Or a computer tomograph? Or beer cans? They just didn't think of that or what? What kept the people
around 6000 BC from doing some smelting?
Smelting was most certainly not invented by some ancient Einstein, who thought very hard for a while and thenproclaimed how it should be done. Smart phones weren't made that way either. Smelting was not invented but
discovered - probably more or less accidentially, and in bits and pices, like many big discoveries. It is also quite
likely that it was almost discovered many times by ancient "pyro-technologists " (use the link if you want to find out
what that is) but that most of these guys did not notice that something special had happened.
Times need to be right for big discoveries. Maybe you needed a somewat stratified society before smelting could be
discovered, with chiefs bent to accumulate special and rare things, however useless, to demonstrate that they aresomehow above the lower strata of society. The role of status symbols - that's what a copper mace head, a fancy
pattern-welded sword or a wootz samshir with a Mohammed's ladder pattern were - for the development of scienceand technoloy should not be underestimated!
Do you notice how cunningly I diffused the actual issue? It was: were the copper implements found in the Varna madefrom elemental copper or from smelted copper? Were they cast or hammered into shape? I gave you just my personal
opinion but without any proof. I could just as well have given you the personal opinion of some archaeologist - but he or
she doesn't have proof either since it appears that the Varna objects have never been properly investigated. There areways to tell smelted copper from native copper as we shall see.
In order not to lead you astray too much, it now behooves me to state that there is a growing consensus that the
Danube culture did smelt copper as early as 5000 BC. It might even be the culture that discovered he smelting of
metals!
As it turns out, the simple and rather innocent questions I asked about some early metal artifacts here tend to open big
cans of especially squiggly worms. We will see another example of this in the next sub-chapter.

1)e.g. Colin Renfrew in his article "Varna and the emergence of wealth in prehistoric Europe" (in the book: "The Social Lifeof Things" Cambridge Uni. Press), or Ch. J. Raub: "The Metallurgy of Gold and Silver in Prehistoric Times", NATO ASI
Series, 1995.

2)

Oleg D. Sherby and Jeffrey Wadsworth: "Ancient blacksmiths, the Iron Age, Damascus steels, and modern metallurgy
J. Mat. Processing Technology, Vol. 117 (2001) p. 347-353

3)

Of course, if one subscribes to the good color / bad color hypothesis, one needs to explain why the bad golden /yellow color became good at the latest around 4 500 BC (Varna burials).
Easy! People discovered beer around this time. No more needs to be said. I want this to be known as the PROSIT(Pursuing Radical OStentatious Interdisciplinary Transactions) hypothesis.

4)

Donna Tartt: "The Secret History", a "mesmerizing and perverse" novel from 1992, Penguin Books.

Iron, Steel and Swords script - Page 283

10.1.2 Native Copper
Is There a Native Copper "Age"?
The first metal used by humans appears not to have been gold but copper. Or maybe lead? I have dealt with the gold
puzzle in the preceding sub-chapter, now let's look into the copper issue. Or is it the lead issue? Am I confusing? Well I'm just staying with the gist of the ongoing discussion in "insider" scientist circles and between all kinds of interested"outsiders" (like me).
Let's start by asking another deceptively simple question:

Who used the first metal (Copperor Lead), when and where?
If you think that this is a simple question, think again. There is a simple first answer, however: Nobody knows for
sure!
First of all, it is not impossible that some ancient culture we have not yet discovered had used metals long before
any of those we know at present. Maybe this culture has perished without leaving a trace, or maybe we just haven't
found it yet. There is plenty of speculation about the lost continent of Atlantis, for example, and while that is mostly(or better: completely) baloney, you can never be sure that there isn't something spectacular out there waiting to bediscovered. In fact, during the last 50 years or so, totally unexpected finds have been made; suffice it to mention"Varna" and "Göbekli Tepe".
However, it is rather unlikely that we find totally unknown cultures that were more advanced then the ones we know
about. The reason is simple: It is just not likely that much advanced stuff has happened before the end of the last
ice age about 10 000 years ago that triggered what is called the "neolithic revolution", and we do have a general ideaof what happened then.
So let's rephrase that question: "Who, as far as we know from digging around, used the first metal; when and where?"This question can be answered and it has been answered. Many times, actually. There is not just one answer but many
- the particular answer you get depends on whose book or paper you consult and on how old it is. If you want the oneand-only definite answer, you will have to wait, probably until hell freezes over. It's better to get acquainted with the ideathat there may not be a definite answer. Just look at Çrockü , an ancient guy, who carved some nice green rock hefound (happened to be malachite) into a bead or pendant for his sweetheart, one Ms. Nölüdyæ (they did have funnyspelling then). This was a rather routine thing to do for Çrockü, he had done it many times before. But this time he didn't
notice (or care) that his workpiece had some elemental copper inside its green shell. 12 000 years later we find it anddeclare: "There is worked native copper! The very first one!" Is Çrockü now really Mr. "The First"? This may have
happened, by the way.
But how about that lead (Pb)? Well, a lead bead was supposed to have been found inÇatal Höyük, one of the earliest cities ever unearthed. That lead bead dates to theseventh millennium BC and provides a major, major puzzle! Since lead can only beobtained by smelting, it provides a starting point for smelting technologies at about
9000 years ago in Çatal Höyük - and that date simply doesn't match with everythingelse we know about that. It is several millennia too early!
If you have never heard of Çatal Höyük: use the link hub! You will find a great many
details about Çatal Höyük and a number of other very early places of interest.

Link Hub
Early places

Well - as it turned out in 1990 1) , that bead was not made from lead (Pb) but from galena or lead sulfide (PbS).
Galena is abundant in nature. It's lead ore, the stuff you make lead from, and it does look a bit like (shiny) lead.
Lead has been confused before (and even nowadays) with graphite or galena, so history repeats itself.
Now it only remains to solve the puzzle of the lead bracelet from the sixth millennium BC, found at Yarim Tepe I,
in what is now Iraq. It is about 1 000 years younger but still too old. So how about that?
It appears that it has never been properly investigated; an onerous distinction it shares with many famous metal
artifacts. So it may be lead - or possibly not.
Pursuing the question from above does lead into a fascinating if somewhat confusing journey into Anatolia and parts of
the Middle East. Out of the kindness of my heart I give you a lot of details about a number of those early places wheremetal could have been found but wasn't, where it was erroneously believed to have been found, and where it really was
found.
If you take the tour (via the link hub above), you will not only get closer to the answer of our basic question but also findout that ancient man (and woman) was seriously whacky, a bit like Californians. The men were into sex. That's normal,
you might say. Yes - but with turtles? The woman were into jewelry and home decoration. That's normal, too - as longas you don't put the (spiffed up) skulls of your former loved ones on the mantelpiece!
Iron, Steel and Swords script - Page 284

But now let's get going. No more confusing the issue: Who used the first metal ? Was it copper or what? When andwhere?
The answers today in short are:
The first metal used by humans was native copper (Cu), indeed. It was probably not used intentionally but "onthe side" when some native copper happened to come along with a new delivery of "greenstones" like malachite.
The oldest (always small) copper objects are from around 8 000 BC, making them about 10 000 years old; see
the time-line here
The first towns where copper was definitely found are: Asikli Höyük , Cayönü Tepesi and maybe (but probablynot) Nevali Çori - all of them in Anatolia, Turkey, see the map
Should that induce us to declare a Native Copper Age from 8 000 BC - ????? BC? I say: No! As far as I can tell, native
copper usage was slight, and the material was of no importance for the life of those ancient people. I can think of threereasons for this:
1. There just wasn't all that much of the stuff around (with the exception of the "Old Copper Complex" around
the Western Great Lakes in the USA).
2. Hammer shaping (including, maybe, hammer welding but probably not), even with a bit of "pyrotechnology"(see below) just won't get you very far. And melting + casting hadn't been invented yet.
3. Native copper just wasn't very useful. One could make beads and pendants for jewelry from it, or other smallthings like awls and hooks. Those copper things would turn green, and that might have made them moredesirable for jewelry. But native copper is rather soft and not very useful for tools; it is far inferior to the highly
developed flint and obsidian tools around by then.
Now let's look at that in some more detail. For plenty of details use the linkFirst Copper and Neolithic Society
The people in Asikli Höyük and Cayönü Tepesi, who left us some copper beads and stuff, started to settle down around
10 000 BC. They first built some simple "hole-in-the-earth plus wattle and daub" 5) houses, forming small towns, andstopped roaming around the countryside as major style of live. The were still hunters and gatherers, however, living inwhat we like to call "neolithicum" or New Stone Age. Domesticating animals like sheep, goats and pigs, as well as
tending (and breeding) crops like wheat, emmer, barley and einkorn, came later.
Nevertheless, people now became "sedentary", meaning settled down, after roaming around or huddling up in caves
for many thousands of years. That was a complete change of their basic behavior and thus known as the "Neolithic
revolution". Our old friend Çrockü from above wouldn't have seen himself as a revolutionary, though. The neolithic
revolution took place during a time period of a thousand years or so, and it only looks like a "sudden" change inbehavior on large time scales.
Çrockü might have been a neolithian but he wasn't a dummy. He knew that it is beneficial to men if the wife
(Nölüdyæ; by now he had married her) is happy and thus quiet 4), and that this involves giving her jewelry and theoccasional little sculpture that reminded her of his outstanding virtues.
The catchword is "jewelry" or amulets, same thing. Necklaces or other things made by stringing up beads were
found in pretty much all neolithic places, often as grave goods with female remains. All kinds of materials were used
for beads, here is an example with intricately carved bones.
The most prominent material for making jewelry was "greenstone ". Here are a few examples from the general timeand area:

Greenstone beads and pendants, about (0.5 - 2)
cm in size
Source : Daniella E. Bar-Yosef Mayer and Naomi Porat: "Greenstone beads at the dawn of agriculture", PNAS June 24, 2008
vol. 105 no. 25 p. 8549
With friendly permission

There are many "green stones" you can find out there: Apatite (some calciumphosphate; most of the beads above),
Fluorapatite, Chrysocolla, Malachite Turquoise, Amazonite, Serpentinite, and so on. Whatever all that is, the three
red-lettered ones are copper compounds or ores. Best known is malachite, below are examples. Those colorful
copper ores (including blue azurite and many others) are typically found on the upper reaches of copper ore bearing
strata, above groundwater levels and with exposure to air. It's what you see when you roam around the mountains:
rocks with green and blue veins. When you start digging there, chances are that you encounter native copper a little
lower down. It is not necessarily present in the form of nice big nuggets but might be embedded unobtrusively in themalachite / azurite "rocks".

Iron, Steel and Swords script - Page 285

Malachite. Nice solid examples, greenish rock,and with embedded native copperÇrockü and Nölüdyæ, like everybody else in the so-called "fertile crescent" - what is now Turkey / Anatolia, Iraq, Iran,
Israel, Lebanon and so on - "made great efforts at obtaining green minerals for the production of beads and pendants"
around 12 000 BC. A little later - say (10 000 - 8 000) BC "this trend expands" write Daniella E. Bar-Yosef Mayer andNaomi Porat. Both of them subscribe to the good / bad color hypothesis 2). People then even mined for goodgreenstones and traded the stuff far and wide.
A little later than 12 000 BC, Çrockü's descendants had fully settled down. They lived no longer in wattle-and-daubhuts but in large and complex stone houses. They had domesticated some animals, cultivated plants (probably
made beer ) and performed strange rituals in large complex stone temples or ritual buildings. The men were still into
sex but now preferred women to turtles, it appears. They left lots of figurines around with clear meanings. Take thetrip to learn more.
Now to the punch line:

Those guys could not avoid
to get some native copper on occasion
with their "greenstones"
The question is what they did with it. Who knows. They might not have noticed that their greenstone containedsome copper inside (see the "Shanidar cave pendant"), chucked out the faulty lot, tried to do something with the
stuff and failed, or figured out some way to deal with it. Maybe only a few of those guys cared for working native
copper or actually could do it. The copper beads and so on in those neolithic towns typically were found in only one
or two houses.
What some of them did sometimes was to bang some copper into a thin sheet and then roll it up. The pictures tell it all

Copper beads and an awl from Cayönü Tepesi
and Asikli Höyük
Source: Courtesy of Ünsal Yalçin

On the upper left is a cut-open bead, and the rolled structure is clearly visible. On the bottom is an awl.
Now go to your basement shop, get some copper, and bang it into a sheet. It will be easy if you take a piece of copper
wire from some electric cable, while you might fail with a piece of copper tubing. It depends a lot on how pure the copper
is. Electric wires usually use rather pure and therefore soft copper; copper tubes are alloyed to some extend for
hardening (you know the drill by now). Your copper, upon cold hammer forging, might develop cracks before you achieve
the thin sheet you are after. So what are you going to do?

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Right. You anneal the structure in between hammering. Shape it some but no more than the material will takebefore cracking. Then put it into the fire and anneal it. Driven by the diffusion of atoms via vacancies, the dislocation
density will go down, grains will grow, and so on. You know where to look for the explanation of the fancy terms by
now; I will not set links anymore.
When you now continue hammering, you can deform your copper some more without encountering problems.
The great-great-...-great grandson of Çrockü and Nölüdyæ, one Frodü, who madesome of those copper beads and other stuff, knew that too. At least some of those
copper artifacts were done by using "pyrotechnology", to use the fancy word forsome annealing in between hammering. Annealing typically commences attemperatures around 2/3 of the melting temperature. For copper (melting
temperature 1084 oC; 1982 oF) this means temperatures around 600 oC (1112 oF),
easily reached in a regular fire.
How do we know this? By looking at the microstructure - an example is given
below; details can be found in the link

Link HubPyrotechnology

There is much that you can make from thin metal sheets - if you are a good smith. If you can even hammer-weld twopieces together, you can do even better. So how about hammer-welding copper? Try it in your basement. It didn't work
for me. Definitely not with cold copper, and neither with hot (but not very hot) copper. I'm not saying it can't be done; I'mjust saying that it is not easy, in contrast to hot iron or (pure) gold. Gold isn't easy either but for a different reason. Do
some experiments with some 24 ct gold stuff of your spouse (best done when said spouse is far away) and you see
what I mean. Seriously now: "native" gold typically comes as "dust" - try to hit that with a hammer!
Frodü couldn't hammer-weld copper either - at least I didn't see any evidence for that. The best he and his cronies
could come up with (as far as we can tell from what we found) is the famous mace head from Can Hasan:

Mace head from Can Hasan
Diameter about 5 cm
Source: Courtesy of Ünsal Yalçin

D. French, the guy who dug out Can Hasan in the 1960ties, pronounced this mace head to have been cast, and thiscaused no end of confusion. This particular artifact dates back to 6 000 BC, and there was just no way that people thencould have cast copper (or anything else) for a very simple reason: they hadn't invented pottery yet!
Çrockü, Nölüdyæ, Frodü, and everybody else living from roughly 10 000 BC - 6 000
BC are called "PPNA" or "PPNB" people in polite scientific circles, with "PPN"
being short for "Pre-Pottery neolithics". They burnt lime (rather amazing!), shaped
clay and hardened it some in a fire, made mudbricks and dried them in the sun,hollowed out stones to get bowls, and so on - but they did not make "hard-fired"pottery! And if you don't have that, you simply do not have a vessel or crucible inwhich you can melt copper at 1084 oC (1982 oF), always provided you have a moldand can get the temperature up this high in the first place (they could not). It's as
Iron, Steel and Swords script - Page 287

BC are called "PPNA" or "PPNB" people in polite scientific circles, with "PPN"
being short for "Pre-Pottery neolithics". They burnt lime (rather amazing!), shaped
clay and hardened it some in a fire, made mudbricks and dried them in the sun,hollowed out stones to get bowls, and so on - but they did not make "hard-fired"pottery! And if you don't have that, you simply do not have a vessel or crucible inwhich you can melt copper at 1084 oC (1982 oF), always provided you have a moldand can get the temperature up this high in the first place (they could not). It's as
simple as that. For casting you need some special hardware (see the link), and if
you don't have it, you don't cast.

Basic Link
HardwareSo Ünsal Yalçin, an eminent archeometallurgist from Bochum, Germany, when he was allowed to investigate themace head, duly found out 3) that the this artifact was hammered and not cast. The pictures above clearly show not
only the seam but also that the two pieces did not weld properly at the seam.

Microstructure of mace head from Can Hasan
Source: Courtesy of Ünsal Yalçin; from 3)

Looking at the microstructure as shown above makes clear (to anybody familiar with typical microstructures ofcopper) that the object did not solidify (no dendrites), i.e. was not cast. It has been deformed ("pressure twins") andannealed (large grains, straight grain boundaries, few defects in the grains).
What happened after bead making started about 10 000 years ago in Cayönü Tepesi and Asikli Höyük? Almost nothing
for about 2000 years. Then some more beads and the mace head appear about 8 000 years ago in Çatal Höyük and
Can Hasan. The nothing again for another thousand or 1500 years.
To be sure, there is the occasional copper artifact that was found between 8 000 BC and 5000 BC somewhere inEurope, the Middle East or in other places, and most certainly only a tiny part of what had been produced has beenfound. Nevertheless, there simply was never a native copper industry that was of any importance to the people in the
Middle East and Europe. There wasn't all that much native copper around, and whatever there was ended up coldworked / annealed into some not-so-useful items, and that was that. Copper tools just could not compete with stone
tools, and copper jewelry, that sooner or later turned green, was not that much better than the easy-to-make greenstone
stuff. The big step in early metallurgy involved smelting, melting and casting of copper around 5000 BC. It was a huge
step to take, and the old (and possible long forgotten) "native copper" experience was of no importance whatsoever.
Interestingly, things in America went differently. The native North-Americans (sometimes called "Indians") around
the Western Great Lake area had discovered huge deposits of copper ore, including large amounts of native copper,
often in rather large pieces. They used it for several millenia since at least 4000 BC, and made a very large numberof copper artifacts, including large pieces like axes and spear points. This is known as the Old Copper Complex,
this link provides for details.
Racial bias prevented proper investigation of the Old Copper Complex until the (later) second half of the last century
because nobody (with a white background) believed that primitive Indians could have developed a metal technology.
Well - they did. However, it remained a rather primitive technology forever. Smelting, melting and casting was notdiscovered in North America.
The "High Cultures" of Meso- and South America did have some copper and bronze technology, including smelting,melting and casting. It came into being a few thousand years after the copper and bronze age in the Old World andremained rather primitive, possibly because these cultures never invented bellows, absolutely necessary for largescale smelting.

Iron, Steel and Swords script - Page 288

Where Does That Leave Us?
Now that I have answered the basic question in some detail, let me ask you a question: "Are you satisfied?" Neither am
I. While it is clear enough that during the neolithic revolution the occasional copper bauble was made by some "artist",copper was clearly not important to the PPN people. The first discovery of metals did not cause a revolution in humanculture and civilization, as has been often assumed.
Looking at early metal artifacts properly, i.e. scientifically, rather caused a revolution in the way technical artifacts
are treated by archeologists now. Until not so long age the eminent and God-like top-dog digger just looked at theobject, pronounced what it was, how it was made, and when. Then he or she put it into a box - never to be opened
again in most cases. If we are lucky, he or she eventually described the details of the dig where the artifact was
found in some detail. Quite often. however, Mr. or Mrs. VERY IMPORTANT never got around to that.
Archeometallurgy, closing ranks with materials scientists who command a large arsenal of advanced analytical
tools, has changed all that by showing that a wealth of quantitative information can be obtained even from tiny
fragments. Many old mistakes and misunderstandings have been corrected in recent years, and more insights areto follow for sure. New mistakes will be made for sure too, and fresh misunderstandings will evolve. Such is(scientific) life. Nevertheless, progress will be made.
It would be naive, however, to expect that eventually we will get simple answers to our simple questions. The big
picture that starts to emerge is even more colorful and far more complex that the old "three-age paradigm" sotreasured by a bygone era.
If you scanned through the many additional modules I have provided, you couldn't fail to realize that a lot of work stillneeds to be done. Just a tiny part of the metal artifacts hoarded in (the basements) of museums has been properly
investigated at present; more in some countries than in others. We might know quite a bit about early metallurgy insome part of the globe but in other parts major work still needs to be done. Iran, for example, has been all but cut-off
from modern developments and international exchange of results and ideas in the last 30 years or so - but will havemuch to offer for sure.

1)

G. Sperl: "Zur Urgeschichte des Bleies", Zeitschrift für Metallkunde, 81 (1990) p. 799 - 801

2)"We propose that the green color mimics the green of young leaf blades, which signify germination and embody the wish
for successful crops and for success in fertility"3)Ünsal Yalçin: "Der Keulenkopf von Can Hasan", Metallurgica Antiqua, Der Anschnitt, Beiheft 6, 1996, p. 279 - 289.

4)

In todays (June 2013) sunday newspaper, a Turkish emigrant (possibly a descendent of Frodü), who has lived in Germany
for many years and in between married a women his parents picked for him in Turkey, summed it up in ungrammaticalbut nevertheless very precise German: "Guck ich immer türkische Fernsehen. Frau immer türkisch schauen, so ich
müssen auch. Langweilig, aber Ruhe! Wenn Frau Ruhe - besser." (Always watch Turkish TV. Wife always watch Turkish,so must I. Boring but peace and quiet. Wife quiet - better).

5)

I had to look it up, too. "Wattle and daub" means that "a woven lattice of wooden strips called wattle is daubed with asticky material usually made of some combination of wet soil, clay, sand, animal dung and straw." In other words: Thesame construction as the walls of the barn behind the house of my parents.

Iron, Steel and Swords script - Page 289

10.1.3 Smelting Copper - The First
What is Smelting?
What exactly is smelting? I will let you know in some detail in the next sub-chapter.. Here, as a kind of foreplay, I lookon smelting, melting and casting of copper in a more general way that can be extended to most metals.
I will start by looking into what smelting is not. I have done that long ago in an advanced module but now we need it righthere in the mainstream part, so I'm going to repeat and enlarge a bit on what I have stated before.
First of all, let's do away with some common misunderstandings concerning smelting.

1. Smelting has nothing to do with melting!
Smelting is not the same thing, or almost the same thing, as melting. Smelting relates to melting like hitting to s...ting,to put it drastically, or shot to hot, shop to hop, spot to pot: not a all! Take romanic to romantic, or silicon to silicone forexamples where misunderstandings are also quite common. Only one letter is different in all these pairs, but themeaning is very different in all cases. And for you Germans out there: yes indeed - smelting looks and sounds evenmore like "schmelzen", the German word for melting than melting itself, and that is the case because the English"smelting" does go back to the Old High German "smelzan"=schmelzen=melting. Fine. Those Old High (and Low)
Germans just didn't know better. You, however, have no excuse. You could and should know better 2). Especially if you
work for the science section of one of Germany's leading newspaper.
Smelting means to rip apart some molecule that contains a metal. It will be broken up into the elemental metal andsomething else. In chemical lingo you reduce the molecule in a reduction process. Most of the time you do that byreacting it with some reducing agent like carbon monoxide (CO).
If I apply the term for a moment to all molecules (something one normally doesn't), things get clear:
1. Melting ice produces water (H2O); smelting ice produces hydrogen (H) and oxygen (O).
2. Melting wax (the hydrocarbons or alkanes of a candle, for example (CnH2n +2, e.g. C31H64) produces liquid
wax; smelting would produce carbon (C) and hydrogen (H).
3. Melting copper ore (compounds of copper and other stuff like oxygen, carbonates, sulfides, ..) produces amolten copper compound. Chalcocite, a copper sulfide (Cu 2S) or cuprite, a copper oxide (Cu2O), forexample, melts at 1130 °C ( 2066 °F) or 1232 °C (2250 °F), respectively. Smelting copper ore produces
copper (Cu) and residues of whatever else was in there.
4. Melting galena (lead sulfide, PbS) at 1114 °C (2037 °F) produces molten galena, smelting it produces lead(Pb) and some sulfur (S) compound.
5. Melting lead (Pb) at New Years Eve at 327 °C (621 °F) produces molten lead, smelting lead can't be done
because lead is already the elemental metal.
Confusing smelting and melting comes from the naive perception that an ore is some rock that contains theelemental metal inside; in some fine pores or whatever. If you heat the ore beyond the melting point of the metal, itliquefies and oozes out - like water from a soaked frozen sponge upon thawing / melting.
That is a naive perception - except for noble metals like gold or platinum. These noble metals are indeed contained
inside "rocks" as tiny particles in most cases. On occasion there might also be large "nuggets". Compound ofthese noble metals (proper ore) do exist but are very rare.
Relatively noble metals like silver or copper might also occasionally be found as "native" metals, sometimes even inlarge lumps and large quantities (e.g. in the Old Copper Complex in the USA). But the bulk of these metals is
contained in compounds called ores.
This leads directly to the second basic misunderstanding concerning smelting:

2. The temperature needed for the
reduction has very little to do withthe melting point of the metal!
The temperature needed for reducing some ore has nothing or only very little to do with the melting point of the metal. It
is of some importance on how you run the smelting process but does not determine at all the temperature you need for
reducing the ore. True, making the metal liquid in a smelter is advantageous for the whole process because the liquid
metal can easily trickle down - but you can only liquefy a metal after you made it!
To make a long story short, pretty much all smelting requires high temperatures for several reasons:
The original source of heat comes from energy liberated by burning fuel, typically charcoal in old times. You
Iron, Steel and Swords script - Page 290

need a lot of energy and the temperature in the burning charcoal bed should be around 1 200 oC for efficient
smelting; 1 300 oC is better. What we call "burning" is the reaction of the carbon (C) in charcoal or wood withthe oxygen (O2) of the air, producing carbon dioxide, CO2, and a lot of energy in the oxidation zone of asmelter. The energy liberated increases the average energy of the atoms and molecules involved, and thus
the temperature. Moreover, air streaming through a bed of burning charcoal gets completely depleted inoxygen since that is used up after a few layers of burning charcoal lumps.
Whatever sits above the burning charcoals - in smelting this would be your mixture of charcoals, ore andpossibly a "flux". This mixture, called the charge or burden of your smelter, gets hot but can't burn becauseof the lack of oxygen. Instead other chemical reactions take place.
At high temperatures (at least 1 000 oC for efficient smelting) hot charcoals react with the carbon dioxide(CO2) produced lower down to carbon monoxide (CO). This reaction consumes energy, i.e. cools thesmelter. Two molecules of CO are produced for one molecule of CO 2 and that is quite important for rather
tricky thermodynamic reasons given here. The CO produced, streaming up through the burden, reduces theore particles it meets as long as it is hot enough for that process to happen. It gets consumed in a processthat typically produces fresh CO2 and the elemental metal.
All the hot stuff in your furnace (including the flux) may produce more gases, for example the stuff produced
in a typical pyrolysis process, that also come out of the flue. If you use sulfitic ores, chances are that sulfur
fumes, typically sulfur dioxide, (SO2) are produced. And so on.
It is a good idea to stay upwind of a running early smelter!
All the hot stuff in your furnace (especially the flux), including the ore and the furnace wall, may react toproduce liquid slag. While that seems wasteful, it is absolutely essential for iron smelting for reasons weshall see.
The drawing below shows all that schematically. It is not to scale; the reduction zone is typically far longer than theoxidation zone. The charcoals also rest on a kind of grate just to make the drawing easier. Moreover, for simplicity
only the charcoals in the burden are symbolically shown.
Most of the gas flowing through is nitrogen (N2) from the air, doing nothing but funneling of energy from the oxidation
zone, helping in heating the burden above. Air, by the way, consists of 78 % nitrogen, 21 % oxygen, 1% argon, 0.04%
carbon dioxide; forget the rest. In the reduction zone, CO is produced and consumed for reducing the ore, producing
CO 2 once more

Schematic flow of gases through a smelter.
There is far more nitrogen then shown.
We aren't done yet in the listing of major points about smelting:
Any halfway efficient smelting reaction needs to produce liquid slag, and slag is only liquid if it's hot - at least
1100 oC; 1200 oC is better.
If you want to obtain your metal in the liquid state, you obviously have to exceed its melting temperature, atleast in the lower part of your smelter, where it collects. However, it is usually advantageous to melt themetal already in the reduction zone; we shall see why presently. That is the only part where the melting
temperature comes in!
The temperature where the actual reduction of the ore takes place can be rather low, however. Reducing iron orcopper or with carbon monoxide can start at temperatures as low as 400 oC (752 oF). That has some serious
consequences:
Reduction of ore, provided there is carbon monoxide around, starts already way "up" in your smelter, inregions where it is not all that hot. The reduction process therefore is practically always a solid stateprocess, producing small and porous solid metal particles already high up in your smelter.
The problem is to get those particles down without oxidizing them again!. They need to by safely transported
Iron, Steel and Swords script - Page 291

through the very hot oxidation zone down into the "dump", where you collect them either as a liquid, or as asolid lump of welded together particles - a "bloom" - if no melting takes place as in the case of iron.

This is not easy. You need liquid slagfor doing this efficiently.
The confusion often encountered about the "temperature" of smelting comes from neglecting that there are several"critical " temperatures. The condition that the metal produced by the smelting should be liquid , is just one of many. It
is true, however, that producing a liquid metal by smelting often makes things easier and thus is preferred in manycases. If you want to do that, you must go beyond the melting point of the metal, of course.
It is not that easy, however. Even if you could get the temperature in your ironsmelter up to the melting point of iron, you wouldn't be happy. You would not get
liquid iron! You would get a liquid mix or alloy of iron and carbon that we(unfortunatey) call call "cast iron". The reason for this deplorable fact is that very
hot solid or liquid pure iron simply laps up so much carbon from its surroundingsthat it quickly and unavoidably turns into the "useless" stuff mentioned above.
When I stated that the old smiths' couldn't get it up (the temperature) I told you
only half the truth. The other half is: They didn't want to, either. They could havedone it but they didn't want to produce cast iron.

Link Hub
Science
Smelting

Smelting is a rather complex thing to do. If I now have whetted your appetite and you can't wait for a deeper look into
smelting, go right ahead and click your way through the science module right now.
Otherwise, let's go on:

3. Slag found on a dig does indicate
smelting. The absence of slag does notindicate the absence of smelting.
It is generally assumed that smelting always produces liquid slag, and you can tell that smelting took place when you
dig up a lot of slag. You know slag when you see it. I'll get to slag in more detail later. If you can't wait, here is the link.

Slag from iron smelting

Slag from copper
smelting

Source: Internet at large

The second part of the first sentence above is almost correct. If you do find substantial amounts of slag, there must havebeen some smelting going on. The first part is not. The basic copper smelting reaction Cu2O + CO → 2Cu + CO2
produces copper and volatile carbon dioxide and nothing else. The same is true for many possible reactions where anore is reduced to the metal and gases like CO 2.
In other words: it is perfectly possible to smelt an ore without producing slag or anything else that is discarded and left
behind.
It is just not very common. First of all, ancient (or modern) smelting does never have just the right amount of pure
ingredients in the smelting furnace. There is always some "gangue", as we call the "rocks" that the ore isembedded in. Some gangue is pretty much always mixed up with the pure ore. The charcoal contains some "dirt"
and the inside of your furnace might get dissolved to some extent, helping in producing slag. Even some of your ore,possibly all of it, might participate in producing slag.
And this is good! Slag production, if done right, is good for you. That's why in serious smelting slag-producing stuff(called "flux") is always intentionally added to the mix that goes into a smelting furnace.
To make matters a bit more complicated: Slag can also be produced after smelting, when a "bloom" of iron or
Iron, Steel and Swords script - Page 292

whatever product was taken out of the smelting furnace was refined or cleaned in a hearth . Slag then still indicatesthat some smelting must have taken place - just not necessarily where you found the slag.
So, yes, smelting does produce slag - whenever it is done on a large scale, i.e. most of the time. "Large scale"smelting starts essentially as soon as bellows are used to supply the air. A shaft furnace with an inner diameter of
30 cm or so, is already "large-scale"!
The very first smelters, however, did not work on a large scale. It is quite possible or even likely that only little slag
was produced in very early copper smelting. Indications are that this was done on a small scale "at home", possibly
by a few specialists, who had the ore brought in from wherever it was found.
So the absence of slag does not necessarily signal the absence of small-scale smelting.
A first Go at Smelting Copper
Now that we understand each other, let's smelt some copper. Let's do it in such a way that it will be liquid, meaning that
we must exceed the melting point of copper at 1130 °C ( 2066 °F) in our smelting apparatus.
You do it - with only the implements you had some 6 000 years ago. After all, you know by now a lot more about
smelting than whoever did it first. Should be easy.
I'm waiting with bated breath!

Waiting
Aha! It didn't work! That's what I expected. So you took a ceramic tube, filled it with charcoal and copper ore, set it on
fire and waited. And waited. And no copper was produced! Well - I couldn't produce any either. Lots of people recently
tried - just for fun or with science in mind. Typically, it doesn't work the first time. Or the second time.
So let' see how the ancients did it and ask the old (and slightly stupid, as we know now) question:

Who smelted (and cast) copper
for the first time?
When and Where?
And how , exactly?
Note that I deliberately put smelting and casting together. While it is possible that somebody melted native copper andthen cast it into a mold, there is no evidence for that. This might look a bit strange on first sight - why shouldn't Frodue's
grandson Frodoe, who was a nice chap showing great promise despite his furry feet, not get the idea of putting some
native copper in a pot, melt it, and pour it into some mold?
Because melting and casting copper is actually more difficult in a way than just smelting it from ores. All you needfor "inefficient and messy" smelting is a regular-size ceramic bowl or crucible, some malachite or azurite, somecharcoal and a blow pipe. Any hollow reed with a clay re-enforced end will do. The rest is just "know-how" .
For melting and casting you need in addition to all of the above:
A crucible for the molten copper that can take the heat and the liquid
copper. That need not to be much different from the smelting crucible but
you must be able to handle it.
A mold with the right shape that won't fracture on impact with hot liquid
copper.
A way to manipulate very hot things. Your kitchen gloves will not be goodenough for handling a pot hotter than 1130 °C ( 2066 °F)!

Iron, Steel and Swords script - Page 293

Basic Link
Hardware

The link gives an overview about the hardware needed to smelt, melt and cast. It also defines terms (e.g. thedifference between heart, oven, stove, kiln and furnace). Seen in this way (and there is no other way) it is small
wonder that melting and castings came quite likely together with smelting. As far as the archeological evidence
goes, both techniques appear around the same time.
There are innumerable books and articles (including my own ones) that assume that smelting was discovered more orless accidentally by a potter doing high-fired pottery. I'm not considering low-fired pottery, spanning the range from sundried mud bricks to some simple stuff made from local goo and put into a regular camp fire (typically not exceeding
600 oC ; 1 112 oF). That is fine for making the Venus of Dolni Vestonice but not good enough for making a crucible
Read the very good essays on Geology, History, and People of Richard Cowen and you get an idea of how this might
have happened. Or read on.
Anyway, high-fired pottery needs pyrotechnology , the processing of things at hightemperatures, and pyrotechnology in a non-trivial sense is actually older than pottery.
Çrockü, Nölüdyæ, Frodü and their contemporaries already knew how to burn lime inquantity (not an easy thing to do) and even to make concrete (rather tricky) long before
they hit on pottery and smelting! Check the link for details.
When people finally started to go into serious pottery, it stands to reason that some ofthem tried to adore their pots with those well-known green or blue stones - malachite or
azurite - but after firing they found dull pots and a bit of copper. That's how the usual
story goes. It is not wrong. Something like that could happen in principle. It's just notvery likely.

Link HubPyrotechnolgy

It is not enough to have some copper ore and high temperatures for smelting copper. You need to produce carbon
monoxide (CO) to reduce the ore, and that does not only need high temperatures but also lack of oxygen. You won't
easily get the necessary high temperatures in a fire as shown below, nor a lot of carbon monoxide.
Producing the required temperature and a reducing atmosphere in a good pottery kiln can be done - the red / black
Greek vases from around around 500 BC bear witness to that. But that kind of technology did not exist when thefirst smeltings occurred.

Direct firing of pots
Source. Wiki Common; Tatoli Ba Kultura

What I'm saying is that the pyrotechnology people used around 7000 BC - 6000 BC wasn't likely to produce copper or
any other metal accidentally because some smelting occurred. You aren't likely to win the check pot in the lottery next
week either - but somebody will. Very unlikely things do happen if you try often enough. If you bring copper ores
collected for their beauty and some pyrotechnology together often enough, somebody somewhere will have accidentally
produced some copper at some time. And that somebody will very likely not have noticed that. How often do you
rummage around in the ashes of your stove or chimney, looking for unexpected treasures?
So let's face it: somebody somewhere and sometime got everything right and recognized that something special
had happened. Maybe the lucky discoverer had some knowledge about working native copper. Maybe he noticed
that something special was contained in the pile of garbage left over from making pottery because his wife forced
him to get the garbage out, and in picking it up those reddish prills became visible. And wasn't the big chief, the guy
who had forcefully united all the warring clans into his "kingdom", crazy about those useless things that one foundevery now and then?
It could also have been quite different. Maybe some early potter was really bend on getting away from the standard
pot decoration techniques of using ochre powder that was rubbed on the "green" pot to be fired. Ochre is a mix ofearthy stuff but always contains haematite (Fe2O3) - an iron ore. What you got was a reddish-brown color in the
typical oxidizing atmosphere encountered in primitive firing. This guy was bent on getting the bright blue or green of
azurite or malachite and started to experiment. He didn't succeed in getting colorful pots, and he didn't get any
copper either. But this guy was tenacious an kept going. Maybe he put some malachite inside a pot with somecharcoal, just to see what would happen. Maybe some copper ore fell inside a pot by accident, together with somecharcoal. With luck, some smelting in a crucible could then have happened in a really hot fire.
Then again, maybe what happened was ...(Insert you scenario of choice)Iron, Steel and Swords script - Page 294

The only thing we know for sure is that smelting copper was discovered about seven thousand years ago!
Who Dunnit?
Noticing that something special has happened was probably the decisive step. It must have lead to some experiments
along the "let's forget pottery and make copper" line. A break-through had occurred, and it:
either spread from the unique place of discovery by "diffusion", orwas discovered independently in other places at some other time.
There you have the "diffusion" or "independent discovery" hypothesis once more.
Of course, both hypotheses might be right if you look a the very big picture. The Meso and South Americans
certainly discovered copper smelting and follow-up technologies like making bronze completely on their own - andmillennia later than the Old World guys. They never discovered iron smelting, though. On the other hand, there islittle doubt that copper and iron metallurgy diffused into China from the West. But how about the "hot" very early
regions stretching from the Middle East via Turkey to the Balkan? Let's see what the experts have to say:

"Extractive Metallurgy", by the way, is the polite term for "smelting technology".
Well-know experts authored that recent paper. They go for "Belovode, a Vinca culture site in Eastern Serbia " anddate it to around 5000 BC. The Vinca culture is part of what I called the "Danube culture"; the link tells the full story.
Now we know. Or do we? Here is a paper from another very well-know expert:

The Yumuktepe mound, now in the thriving town of Mersin, was first excavated 1937 - 48; digging resumed in 1993.
Ünsal Yalcin, an author who already rectified the puzzle of the Can Hasan mace head, re-investigated some of thecopper that had been found there and concluded that the copper was melted and came from "extractive metallurgy",i.e. smelting - around 5000 BC once more.
I could show you more articles to "first smelting"; all of them sincere and convincing. Collecting "first smelting" articles
could easily develop into a hobby, in fact. With more and more new finds or new analytical results of old finds coming inon a regular base, one could spend quite some time by acquiring, sighting and classifying new finds.
So let's give up. At least I do. Let's just recognize that smelting copper had been discovered around 5000 BC
somewhere in southern Europe / Asia Minor.
Fine. Discovering something is a start. Where it gets you, however, often depends on many things. It was and israther common that a lot of time might pass between a basic discovery and its being used for large scale
applications. Some countries out there have not yet adopted democracy, something discovered 2 500 yeas ago andproven to be a good thing. Volta came up with the first battery and thus a source of electricity in 1800, and it was of
no use to anybody but a handful of crank scientists. It took 100 more years before it started to change the life ofpeople at large. Steel, our topic here, is a pretty old discovery but it took something like 3 000 year before it was
really used on a large scale.

Iron, Steel and Swords script - Page 295

It's the same with the discovery of copper smelting. There is still a long way to go before smelting as an "industry"
actually changed the life of people. The first copper tools must have been far inferior to good flintstone or obsidian
tools, so why bother. In order to give you an idea of the complexity of early metallurgy development, I have redrawn
a rather illuminating collection of data originally compile by Chernykh , 1992 1). It is best seen in the large version.

When and where copper and copper alloys(different colors) were used
Large Version
What you see is when and where copper and copper alloys (different colors) were used. I'm sure that many new
data since 1992 should be included, and that some old data need to be corrected. I'm also sure that the over-all
picture would not change drastically. What one recognizes without looking at details is:
Regional differences are large.
There is a "native copper pocket" in the "Middle East and Turkey and somewhat later in the Danube region.
Here is a necklace with native copper beads from there.
There is an "arsenic copper" pocket in the "South-east" before the coming of bronze
Nothing much was going on before about 4 500 BC even in the "advanced" regions, where native copper was
known for thousands of years by then.
Copper smelting done by early cultures ("Varna") disappeared around 3 500 BC, leaving a gap of several 100
years before the technique reappeared again in the general area
Allright. Enough soft talk. Let's smelt some copper now

1)

E.N. Chernykh, (Inst. Archeology, Academy of Science, Moscow): "Ancient Metallurgy in the USSR; The early metalage" Cambridge University Press,1992

2)

For example you, the guilty writers in the 1999 book "Kupfer für Europa" (Copper for Europe), ed. Ralf Busch- That's thebook to the special exhibition of Cu and Cyprus in the former Helms museum in Hamburg, Germany (now it's thearcaeological museum).

Iron, Steel and Swords script - Page 296

10.1.4 Smelting Copper - The Second
Let's Smelt!
I am now going to demonstrate the working of a "large-scale" copper smelter to you. That is the kind of apparatus thatallowed to start the "bronze-age" around 3 500 BC, about 1500 years after the first small-scale smelting of copper. From
today's point of view, those smelters are pitifully small affairs. However, compared to what was around before, they werecomplex and large "machines" that also needed a certain infrastructure for successful operation.
It also doesn't matter at this level of generalization what you smelt. Here we look at copper, but doing iron would also be
possible, not to mention lead and tin.
The first thing we need is a "container" that, well, contains the fuel, ore and flux in the top part of the smelter, and the
product in the bottom part. It also - most important - must contain the heat produced by the energy source in thebottom-near region.
That you must somehow mechanically contain the ore, charcoal, and copper produced is a bit trivial at first sight. I
promise that it will stop to be trivial when you look at it a bit more closely.
That you must contain the heat is also trivial. If you don't, it just won't get hot enough where it's needed. Yourheating apparatus in your room will not be able to sustain the temperature in the room if you open all windows andmake sure that there is a draft.
So let's make a shaft furnace, a tube with an inner diameter of roughly 30 cm, and up to a meter tall. We make itfrom a material that can take the heat and that has a low heat conductivity, so heat doesn't leak through the walls.
Mud or clay, perhaps re-enforced with some straw, might do the trick.
Our furnace tube must not contain the gases blown through it or produced during smelting. They must be allowed toleave through the top or "flue". Since our construction is open on the top, gases can not only leave there, we can also
use that opening to replenish fuel, ore and flux from time to time.
The bottom part is set somewhat into the earth, after we lined the very bottom with some suitable stones as shown
here:

Bottom part of a shaft furnace
Source: Photographed in the Goslar museum

Now we need a few more openings. Definitely one for running the air in that is needed to keep a fire going. Through that
opening we stick a pipe, called a "tuyere", through which we will blow in the air, somehow.
Maybe we add another hole lower down for tapping liquid slag every once in a while. The whole contraption (without aslag tapping hole) now looks schematically like this:Schematics of a real smelter

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A first construction problem becomes obvious. Everything would be far easier and more elegant if the solids(charcoals, ore, flux, ...) would sit on a grate , with the air flowing uniformly through the load which we will now callby its proper name: "burden".
Sorry. Can't be done. There was (and more or less is) no material that can take the heat and the weight of theburden for very long. We have no choice. We need to blow in the air with a tuyere from the side as shown. In doing
this we must make sure that:
1. It is the right amount of air (always a lot), and
2. It flows out of the business end of the tuyere with the right speed that makes
it go nicely through the whole diameter of the furnace as shown. If it comesin too slowly, it will not reach the other side. Too fast and it will leave a"dead" pocket above and below the tuyere.
The diameter of the tuyere is essential here. It is easier to move a lot of air into thefurnace if the diameter is large - but then the air will flow slowly. The two demands
are contradictory, and in order to meet them the (inner) diameter of the tuyere mustbe just right for the kind of pressure you can apply to your blowing apparatus.

Link Hub
Science
Smelting

Even with the right tuyere diameter it is not so easy to meet the two easy-to-state requirements above. It is actually very
difficult as we shall see. Read up the science module if you want to know why this is so right now. Otherwise we justassume that we somehow can do it right.
Now we fill our smelter with charcoals only, and start the initial fire.
No, No NO!! You don't use your barbecue charcoals! That's one of the many reasons why your smelting didn't
work. You need to use a carefully adjusted mix of high-energy charcoals produced from special hardwood trees,and highly reactive charcoals made from soft wood. For best results the charcoal should have been made frombranches and not from the trunk of the tree, and at rather high temperatures. In other words: you use special andexpensive charcoal.
Not to forget: You pay a lot of attention on making sure that your charcoal lumps have all about the same size, andthat must be the right size. You need to meet two contradicting requirements once more:
1. The surface-to-volume ratio of your charcoal bed should be large since the energy production (the "burning")
takes place at the surface. That calls for a small lump size. Not too small though, otherwise too many
surface regions touch and cancel each other.
2. The air resistance of your charcoal bed should be just right and not too large. Air resistance measures how
hard it is to blow air through your burden. For very fine lump sizes (essentially a powder), air resistance isvery large and blowing air through a bed of powder would take a very high pressure. You might just blow yourburden right out of your furnace in this case. Making the lump size large, or using just a pile of wood, makes
it easy to move air trough the pile but now your energy production goes down, and a lot of the oxygen in the
air isn't even used for burning but passes just through, preventing carbon monoxide production.
Your lumps size needs to be just right. As a rule of thumb, start with a size of about about 10 % of your inner
furnace diameter and then optimize.
Now set the charcoals on fire from below, establish proper air supply, and keep it going until your furnace is "attemperature". It will take a while because during this period you heat up and "fire" the clay walls of your furnace, too.
You will observe that only the first five or so layers of charcoal are really burning, with a temperature of (1200 - 1300) oC((2192 - 2372) oF). Actually, you will not observe that because there is no way to look inside a working smelter. You
infer that from indirect observations.
Why is that? Why shouldn't the whole stack be on fire? Because the oxygen needed for burning comes from below, andat optimal conditions there is no more oxygen left after the air traveled through the first few layers of your charcoal bed.
Instead of the normal oxygen - nitrogen mix that constitutes air, you have now a carbon-dioxide - nitrogen mix a few
layers above the burning charcoals. That is good - it enables smelting!
The charcoals above the ones burning and thus taking out the oxygen from the air are quite hot, of course, since they
are close to a very hot fire and exposed to very hot gases streaming through. Those gases are the carbon-dioxide (CO2)
formed by the burning reaction that also produced all the energy, and the nitrogen of the air that does not do anything
except getting hot. If you provide enough of that energy (by reacting the right charcoals having the right size with theright amount of air) the charcoals above the burning layer should acquire a temperature of at least around 800 oC (1472)
oF); more is better. That will allow the reaction of the carbon in the charcoals with carbon dioxide from below, producing
deadly carbon monoxide (CO) according to:
CO 2 + C ⇔2 CO.
This reaction actually consumes energy and thus cools things to some extent. So if you want the reduction zone to bearound 1000 oC, the oxidation zone, where the burning takes place, must be considerably hotter.
The carbon monoxide produced will move up the stack with the nitrogen and the carbon dioxide that might have been leftover.
After a while of burning just charcoals, your smelter is ready for use. You can check that by hanging over it. If you
are dead quite quickly, the carbon monoxide production is taking place satisfactorily. A better way is to watch how
fast your charcoal moves down. Charcoal disappears almost completely by either turning into CO2 or CO, and thewhole burden therefore moves down the shaft at a certain rate or speed. As soon as this consumption rate looks
right, you start to add ore and flux to the charcoal you feed to your smelter.
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Now we can finally start to do a bit of smelting! And it goes without saying that you better take care to:have the right ore or mix of ores.
The right average size of your ore pieces.
The right kind of flux or mixes of fluxes,
with right sizes.
And in particular the right amounts of charcoal, ore and flux!
This link gives an idea of how that was done not so long ago in the case of iron smelting.
As your burden moves down, a given layer in the burden will get hotter and hotter while it is exposed to the carbon
monoxide and nitrogen streaming up. The nitrogen still doesn't do a thing except heating the burden and funneling out
energy. There is nothing you can do about that.
The carbon monoxide, however, will start to react with your ore, reducing it, and it does so typically already at low to
medium temperatures already present high up in your furnace. The product of the reaction is the metal, and typicallycarbon dioxide once more. Possibly some more stuff is produced, depending on what kind of ore you use, either
escaping as gas or adding to slag production. That will turn out to be a serious problem; I'll ge to that.
In either case, you now need to fully understand an often overlooked but serious fact of smelting:

Metal production by reduction isalways a solid state process!
In a way that is clear. You can't melt a metal before you have it.
Very schematically what is going on looks like this:CO production and ore reduction in an atomistic
modelThis is what happens on an atomistic level. Hot carbon (upper left) reacts with one molecule of carbon dioxide (CO2;blue ellipse) to form two molecules of carbon monoxide (CO; pink ellipse) The CO takes out the oxygen atoms fromthe surface of the metal oxide (center right). This leaves surface vacancies behind. The left-behind metal atoms
roam along the surface until the find a metal crystal into which they become incorporated. Alternatively they start toform a new one. The arrows just indicate that all the gas molecules run around with a very high speed that defines
the temperature.
Your gangue plus the added fluxes also start to react, forming glassy stuff that is, however, neither fully formed nor
liquid at the medium temperatures where reduction is already happening. This is not shown above since my artistic
talents are limited.
Once more: Reduction starts early and turns the ore into the metal plus, depending on what kind of ore you use,
something else that either escapes as gas or participates in slag making. Nothing is liquid while that happens.
Eventually, the process is finished. The newly smelted tiny metal particles move down with everyhing else, getting
hotter, but for a while they are still in the carbon-monoxide rich area we call reduction zone, together with charcoals
not yet consumed and the slag that meanwhile also has formed from the gangue and the flux added to the burden.
But after a while you run into a big a problem. You must get your metal now through the very hot and oxygen containingzone (the oxidizing zone) where the charcoal burns, all the way to the bottom. You must do that without oxidizing yourmetal again !
If you ever watched a smith putting a piece of iron in the really hot part of the fire on his hearth, you saw that his
solid piece of iron oxidizes very quickly. Your solid small copper or iron particles don't stand a chance! They will
never make it through the oxidation zone if the go down there in a leisurely pace. They will get completely
reoxidized! You must move them through rapidly , and that is best done if they are liquid! Liquids can move much
faster down the bed of charcoals than solids that must move with the charcoals. Liquids just trickle through.
The problem of course is that we do not necessarily have our metals liquid. The melting point for copper may not yet
have been reached at the edge of the oxidation zone, and for iron it will never be reached. Iron stays solid all thetime. So nothing helps but enclosing the metal particles in liquid slag
Iron, Steel and Swords script - Page 299

Liquid slag can easily take small solid particles along when it trickles down. And it not only transports them fastthrough the dangerous oxidation zone, it also protects them from oxidation since it coats the particles.
If a liquid metal trickles down by itself, it will become partially oxidized but some metal might make it. The metaloxides formed will end up in the slag.
I'm talking efficiency here. How much of the copper contained in the ore ends up as the elemental copper you areafter, how much ends up in the slag as copper ore? It is not difficult to have a very high percentage for the latter.
You fill in a lot of ore and charcoal but you get just a little bit of metal; see the picture below.
Now you have one very good reason why slag is good for you - if its the right kind, and so on. There are more very goodreasons why you want to produce slag - read about them here or just believe me!
All I wanted to do here is to demonstrate one thing. Smelting adheres strictly to the Goldilocks principle:

Smelting is a complex process!
A lot of things need to be JUST RIGHT!
A lot can go wrong. If you don't start with everything being just about right, there is very little you can do after you
set your smelter on fire.
Nowadays we understand most everything and can model what is going on inside a smelter on a large computer.
But a few details are still not all that clear. The reason is that it is impossible to "look" inside a running smelter,
watching what is going on.
Next let's look quickly at the key problem of smelting: the air supply!

The Overbearing Importance of Air Supply
Very simple calculations or quickly gained experience will teach you that you need a lot of air to run your smelter fromabove. How are you going to supply that air. Let's quickly go through the options:

1. Blowpipe
The picture shows the use of blowpipes around 2 400 BC in Egypt. The other half of that picture is here. You supply air
to your smelter by exhaling into a blowpipe that leads right into the furnace or crucible.

Use of blowpipes around 2.400 BC
Blowpipes are laughably inefficient. It takes six guys in that picture to keep a tiny little crucible at temperature!
There is no way to run the smelter above with blowpipes. There would not be enough space for assembling thenecessary throng of guys around your smelter. And no, you can't just make the blowpipes longer; they loose
efficiency with length.
While smelting probably did start with with blowpipes, you didn't get very far this way and it went out of custom. It took
only a few thousand years for the guys to figure out something more effective.
That's right! Smelting in the very beginning, before it became more common place around 3 500 BC, was done with
blowpipes or with one of the methods coming next. It was still used after 3 500 BC as the picture proves. However,blowpipes still would have been your instruments if you just wanted to melt small amounts of a precious metal like goldin the privacy of your home. Maybe that's what those old Egyptians were doing. I'll get back to that further down but first
I like to introduce a somewhat better if still not-so-good method for supplying air.

Iron, Steel and Swords script - Page 300

2. Natural Draft and Wind
Potters could (and still can) heat a large kiln to very high temperatures by burning wood in an mostly enclosed fire box
connected to the "hot box". The whole contraption was constructed in such a way that it produced sufficient natural draft(via the chimney effect) to keep a lively fire going.
That kind of construction culminated in the "reverberatory furnace" that even allowed to melt iron in the 19th century.
Fine - but we are talking 6 000 BC or so here. Those guys might have mastered kinky sex by then, but they couldn't
even get close to a reverberatory furnace or an advanced kiln.
Nevertheless, more simple "natural draft" furnaces might have been used. Unfortunately, not much remains after
8000 years or so, and what one finds often does not allow an unambiguous identification. Here is an example.
Some natural draft furnaces for smelting iron have been used in Africa in more modern times, so it can work provided you do everything exactly right, of course.
That is also true for the next kind: Wind-blown furnaces. Besides doing everything just right, you now must also
have the right wind from the right direction. Wind-blown furnaces have been used at least in Sri Lanka around 500
BC for smelting iron, so you can do it.
What we can reasonably assume for neolithic times is that natural draft and wind-blown furnaces were used andthat they were an improvement compared to blowing into a salad-bowl sized crucible with your blowpipe. Natural
draft and wind furnaces might have been instrumental for starting larger-scale copper smelting arond 3500 BC. They
are still rather inefficient and messy, though.
Both types - natural draft and wind - have one huge advantage: if it works, it is very simple and cheap. You save thecosts for food and whips, needed to keep your slaves going, and so on.
However, they also produce a major problem:

Natural draft and wind furnaces
can't be controlled!
The only major control you have while running a smelter is the air supply! You can blow into your blowpipe
vigorously or sluggishly. You can move its business end from here to there. You can get a second guy to help
blowing. You have some control!
With simple natural draft / wind furnaces you must take it as it comes.
Not so good. If we want to do some serious large-scale smelting now, we need to invent...

3. Bellows
Bellows were the major invention for getting serious smelting going. We call everything "bellows" that turns mechanicalenergy into a stream of air, not just the accordion type you're visualizing right now. Your bicycle pump qualifies as
bellows, for example. Here is a picture:

Business end of the big bellows shown here plus apiece of modern junk for blowing up air mattresses
Why bellows are of the utmost importance for smelting is simple to see. One well-trained guy working a welldesigned bellows replaces at least 40 if not 80 guys with blowpipes! Your muscle power is just that much larger
than your breathing power.
Attach one decent bellows to the tuyere of our smelter from above and you are in business. Of course, the diameterand length of your tuyere must be just right, not to mention the "angle of attack" (the 15 o shown are about right),
and you should have no leaks in your set-up.
It is really simple: no bellows - no large-scale smelting. American cultures never invented bellows and they had nolarge-scale smelting of copper either. Moreover, they never got around to smelting iron. More about the topic can befound here.

Iron, Steel and Swords script - Page 301

Bellows offered one more big advantage: you can also work them with powerful machines like water wheels or windmills,
increasing power relative to an human another 50 or 100 fold. Besides the Chinese, however, nobody did that before theMiddle Ages, even so the infrastructure was in place. The Romans, for example, did use waterwheels extensively forother jobs.
The reason for not using large water-powered bellows and matching large smelters was simple. It made no sense to
smelt iron in very large "bloomeries" since you couldn't handle massive blooms, the solid iron produced in there. How
would you get it out, for example, without destroying your smelter? That would be an insurmountable problem eventoday. But bloomeries went out of style around AD 1500, in exchange for blast furnaces that made liquid cast iron.
Doing that you can go for large-size smelters since your product is easily removed by tapping it. A blast furnace, by theway, is exactly the same thing as your old bloomery, except that it is bigger and you blast a lot of air insidecontinuously by mechanical means.
Who was the genius who invented bellows, one the most important pieces of hardware needed for the progress ofcivilization? When and where?
I don't know, neither does anybody else. The Hittites certainly knew bellows around 1700 BC since they broughtthat technology to Egypt when they invaded it. It is likely, however, that bellows are considerably older than that. It
is tempting to identify their invention with the start of "industrial-size" copper smelting around 2 500 BC, somewhere
in Mesopotamia, Asia Minor or the Balkan.
Primitive Smelting
It remains to do a bit of primitive, inefficient and messy smelting, like much of humankind before around 3 500 BC. The
most primitive smelting you can do in your living room, using a salad-bowl size crucible. In fact, your ceramic salad bowl
might be good enough for the job.
The picture tells it all:.

Schematics of a working salad bowl smelter
Heap up some charcoal, more on the side opposite to your blowpipe. Ignite it, put your blowpipe into it, blow. Add
some ore, stir maybe, blow here, blow there, and with luck you will produce a mix of a little slag and a few prills ofcopper, wherever you happened to keep an area hot enough for a little while and produce some carbon monoxide.
It appears that something like that was done for millennia in some towns, here and there. Interestingly, those towns
were not close to the places where copper ore was found or even mined. The ore obviously was "imported" to theplaces where smelting was done, maybe just as much for its "greenstone" quality in the beginning as for smelting a
bit of copper on occasion.
Here are two real crucibles. Note the hole in the base, where you could insert a stick for handling.

Unused (left) and used (right) crucibles from the early
fourth millennium BC; Ghabristan; Iran 1)
Source. Courtesy T. Stöllner and G, Steffens, Deutsches BergbauMuseum, Bochum, Germany

Tin smelting, on the other hand, appears to have taken place close to the mines, for example in Göltepe (not to be
confused with Kültepe), a large bronze-age town thriving from about 3300 BC to 1800 BC in what is now Turkey.
Remains of crucible smelting have been found, but also enormous deposits of slag, indicating that the smelting
method must have been more advanced than what is shown in the picture above.

Iron, Steel and Swords script - Page 302

Now I can dispense with (simple) melting in just a few sentences. Do more or less the same thing as in simple
crucible smelting. Use a smaller bowl / crucible because you must be able to pick it up when it is very hot so you
can pour the metal out. Only put charcoal and copper in there. Blow directly on the surface because you do notneed to make carbon monoxide. Look up a few more details here.
Just for being complete, there is yet another way of smelting. Take a crucible formed more like a beer glass than asalad bowl. Fill it with powdered charcoal and ore plus some magic ingredients (powdered flux in other words). Immerse
it in a bed of burning charcoals or into a very hot kiln. In other words: heat it from the outside. If everything is done right,
you might get the so-called direct carbothermic reaction inside the crucible, reducing the ore first with solid carbon
and not with carbon monoxide. This is rather inefficient because the reaction can only take place at the points where thecarbon touches the ore and not all over the surface as with carbon monoxide.
However, if your were lucky and had the right ore for (iron) smelting, the carbothermic reaction produces its own
carbon monoxide according to, if you must know:
2 Fe2O3 + 5 C ⇒ 4 Fe + CO2 + 4 CO.
The process thus was self-amplifying. It allowed to reduce ore in a furnace or kiln with an oxidizing atmosphere; youdidn't need to produce reducing conditions. This kind of crucible smelting might also have worked for copper - I don't
know.
More about that in this link.
Of course, in a space as large as Europe plus parts of Asia, and during a time span of a few thousand years, all kinds ofsmelting variants must have occurred. The technology slowly improved from extremely simple and inefficient "saladbowl" smelting, via highly organized blow-pipe smelting (like the guys above) and natural draft / wind furnaces to bellows
driven "large-scale" operations. Zillions of variants must have been used, and the archeological records tend to show
this. Here is a rather illuminating statistic from two places of what is now Jordan:

Percentage of copper found in slag as a function oftime.
Different color=different general areas
Source: Redrawn from Haupmann's book

Note the concentration scale - it's logarithmic! Duringn the very early times of smelting, up to 100 % of the copper
ended up in the slag. The "pink" area (actually the Timna area in Jordan, close to the gulf of Elat) was doing better
than the "light blue" area (Faynan, also in Jordan, further North) with only around 5 % Cu lost. As time progresses,
efficiencies get better. Around Roman times Faynan was doing better than Timna, and losses were below 1 %It took several 1000 years to get there!
Still, nothing helps, without bellows plus getting everything about the furnace and its burden "just right", copper smelting
could not take off and become the large-scale operation that used copper alloys and started what we call the "earlybronze age".
Maybe you noticed that I'm inching away from copper smelting towards iron smelting? And that right now it looks
that there is hardly any difference between copper and iron smelting.
Be patient, please. We are almost there. We only need to look at alloying copper first, so we can make proper (tin)bronze and what is referred to as "arsenic" copper.

1)

C. P. Thornton: "The Emergence of Complex Metallurgy on the Iranian Plateau: Escaping the Levantine Paradigm", J
World Prehist 22 (2009) p-301–327

Iron, Steel and Swords script - Page 303

10.1.5 Copper Final
Arsenic Copper
You are currently reading the 10th chapter of Iron, Steel and Swords. The nine chapters ahead dealt essentially with thequestion why alloying iron with some carbon makes a big difference to properties. If you grasped just the general ideas,
it should not come as a surprise that alloying copper with this and that will also change its properties. You also learned
that some alloying might happen during smelting, and that you may not be pleased with that. In other words: Alloying isa great thing to do - as long as you do it "just right".
Hardness was surely the first property the ancient metal workers would have liked to improve. Or was it? We knowthat pure iron or copper is just too soft for chopping off heads, for example. Those old guys (and Judith ) thus musthave gone for improved hardness one should think. Well - not necessarily. Before you can chop off something withyour copper sword or axe, you must first make it. In the case of copper and copper alloys you make it by casting.
Something easy to do, one should think.
No! In contrast to popular misconceptions, casting is not easy. Even if you can get the stuff completely liquid, justpouring it into a mold will not automatically make a good cast object. You might get porous stuff, for example, sincegases trapped in the liquid metal couldn't get out and cause bubbles like in swiss cheese or yeast dough. Or yourmold simply explodes, not so good either. Here is an example of some modern copper axe casting attempts, doneby Julia Wiecken who isn't a clueless amateur but knows exactly what she is doing:

Three tries at casting a copper axe following old"recipes"
Source: Julia Wiecken "Report on actualistic casting preexperiments –The copper hammer and adze-axes from the Carpathian Basin"
Historical Metallurgy Society, Coghlan Bequest. HMSN. NEWS Historical
Metallurgy Society 69, Summer 2008.

Julia tried to cast a copper axe, following the old technique as closely as possible. Here is the link to the actual
paper. It just is not quite as easy as you might think.
Proper alloying can indeed make casting much easier. And, as an added bonus, your copper alloy might even get
considerably harder! The only question is: how much of what should I alloy for getting the best results? And why does
the winning recipe work so well?
If I would try to answer these questions in any detail and with scientific reasoning, I would have to write a few morechapters. I won't. Just believe me without me proving everything..
The ancient metal workers in what is now Iran did not spend much time either worrying about how to answer thequestions above. What they worried about, I surmise, is why the guys down the valley got "better" copper on
occasion than what they produced, considering that those guys made copper the same ways they did as far as
they could tell.
In other words: there is no doubt at all that in smelting copper a lot of unintentional alloying took place. You mightalso call it "getting dirt into the copper". Some "dirt" might be good for some properties, others might be all bad.
Look at the table below to get an idea of the wide range of unintentional copper alloys produced as late as 1400 BC.
Chances of encountering all kinds of alloying / dirt effects while smelting copper increased with increasing business.
In very early small-scale smelting, alloying and other effects might not have been very strong because simple andrather pure ores of the oxide or carbonate types were used, for example azurite and malachite, that were picked up
from surface-near deposits. Smelter temperatures were not very high either, and no fluxes were added intentionally.
That simply restricts what can happen besides making some copper. Prying off the copper prills from whatever slag
and residual charcoal was left, and melting these copper pieces in air, purified the copper quite a bit since a lot of
impurities evaporated or oxidized (and then could be skimmed off). Very early copper therefore is often quite pure.
As production increased, you had to dig deeper for copper ores. Serious mining
started, and down there in the bowels of the earth you encountered more complex
ores, typically sulfides, in all kinds of mixtures. As production increased, all kindsof ores or ore mixtures made it into the smelters. Deeper down into ore deposits
Iron, Steel and Swords script - Page 304

As production increased, you had to dig deeper for copper ores. Serious mining
started, and down there in the bowels of the earth you encountered more complex
ores, typically sulfides, in all kinds of mixtures. As production increased, all kindsof ores or ore mixtures made it into the smelters. Deeper down into ore deposits
you also tended to encounter minerals of other metals and mixed minerals that
contained copper and some other metal like iron, nickel or arsenic.
Temperatures in your more advanced smelters were higher, too, and weird
reactions could now take place.

Misc. Link
Copper Ores

Elements that are often found in connection with copper ores had a higher probability if ending up in your copper than
the rest. Tin (Sn), the key element for making bronze proper, is not among the likely ones so making tin bronze by
accident is unlikely. The more likely elements were arsenic (As), antimony (Sb), nickel (Ni), iron (Fe) and I don't knowwhat else.
Almost everything was possible now, including making some copper-rich (and thus useless) iron. Oversimplifying a lot,
your smelting could go along four different ways:
1. You produced "better" copper, i.e. a copper alloy with improved properties. This happens, for example, if somearsenic gets incorporated, often together with antimony and nickel.
2. You produced "bad" copper, for example if iron becomes alloyed.
3. You produced usable copper plus other stuff like so-called "matte" (copper sulfides) and iron.
4. You produced no copper but something else like so-called "speiss", an arsenic - iron alloy.
Those must have been exciting times in metallurgy. Of course, what we find many thousand years later are almost
exclusively artifacts left from successful copper and copper alloy smelting. Nobody kept the useless stuff, andnobody recorded the curses uttered when a smelting batch went wrong.
As Ünsal Yalçin showed in the paper mentioned before, the "dirt" concentrations contained in the earliest copper
artifacts produced by smelting varied considerably but on a relatively low level. Large variations in compositions
seem to occur for pretty much all of early copper production, with the over-all purity of the copper produced declining
with increasing production in large furnaces.
Eventually some people somewhere realized that certain kinds of copper - like arsenical copper - were just better thanothers, and that one could optimize the production of the "good" stuff by putting the right ingredients into the smelter.
Contrariwise, avoiding certain other stuff and practices made it less likely that "bad" copper was produced.
That is straight evolution once more. The archeological evidence clearly shows that arsenic alloying was encouraged,
while iron alloying was avoided. To us that is clear because arsenic copper is "better" copper, indeed, while ferric copper
is not good for you.
About everybody in ancient times sooner or later produced arsenic copper intentionally. Iran is exceptional in its
long-lasting preference for arsenical copper at a time when most surrounding regions had already switched to tin
bronze. Why is arsenic copper preferable to pure copper? There are several reasons:
It does make casting easier. Not only does the melting point decrease with As concentration, it also helps to
avoid all the negative effects of gases contained in the liquid metal.
It does produce substantial hardening. Just 2 wt% As may increase hardness and tensile strength by 30 %.
You also get a larger work-hardening effect.
It changes the color. In particular, arsenic copper may show a silvery sheen. It may actually appear to besilver if the concentration of arsenic was high enough.
However! The first law of economics still applies. You must pay a prize. .

Arsenic (and its compounds) have thisunfortunate tendency to kill you!
Even worse, arsenic tends to kill you sneakily. Arsenic and its poisonous compounds easily vaporize, streaming outof your crucibles and smelters and poison the air you breath. Don't try to make arsenic copper yourself!
Ötzi the Iceman, the well-preserved natural mummy of a man who lived about 3.300 BC and was found in the Alpes
in 1991, had a considerable concentration of arsenic in his body and hair. This, along with Ötzi's copper axe madefrom 99.7% pure copper, has led scientists to speculate that Ötzi was involved in copper smelting.
Anyway, arsenic copper was first produced more or less accidentally by "co-smelting" copper and arsenic bearing ores
like arsenopyrite (FeAsS), enargite (Cu3AsS4), domeykite (Cu3As) and many others found here and there in copper ore
mines. When you realize that there is some connection between the "input" and the "output" of your smelter, you pay
some close attention to what ores you use and how you process them before smelting. You might even differentiate
what you do. Some make regular, relatively pure copper for everyday uses, some others (and somewhere else) makehighly alloyed "silvery" prestige objects that are traded over long distances.

Iron, Steel and Swords script - Page 305

Witness the Nahal Mishmar hoard found in 1961 in a cave on the northern side of Nahal Mishmar, Israel. It dates
to 3500 BC or older and includes 432 artful copper, bronze, bone and stone objects; 240 mace heads, about 100
scepters, 5 "crowns"", and more. The copper objects alone weigh 140 kg, constituting an immense value for thetime. It is probably the collected treasure of a major temple that was hidden for some reasons. Here is a picture ofsome of the objects; more can be found via this link.

Parts of the Nahal Mishmar hoard
Large picture
Source: Courtesy of the Israel Museum

What exactly some of these objects signify is not all that clear. There are also researchers who argue strongly thatat least som of the objects are form a much later date 3) . The round balls with a hole are mace heads. It isinteresting in this context that a mace head was the first metal weapon found so far, and that maces, good forbashing your opponents skull in, were employed for a long time. The picture below shows a Hittite warrior fromaround 600 BC with a sword and a mace. Note also that there are no swords either in the Nahal Mishmar hoard.
An amazing skill in casting technology 5500 years ago is demonstrated quite nicely by all these objects.
Particularly interesting for us is the large range of alloy compositions used for the objects as is directly visible fromthe quite different colors. Indeed, we have objects made from rather pure copper, objects made from copper alloyedwith up to 20 % of an arsenic (As) - antimony (Sb) mix, and probably anything in between. Some more pictures are
here. One picture shows the "silver sheen" quite nicely.
There are indications that the alloyed copper objects in the hoard were imported from somewhere. It is no yet known
from where exactly but definitely not from close by.

Late (600 BC) Hittite God / warrior with sword andmace.
Source: Photographed at the Karatepe / Turkey open-air museum.

Iron, Steel and Swords script - Page 306

So how do we alloy copper with arsenic? Paying close attention to what you put into your smelter will only get you that
far. For achieving copper with a defined concentration of arsenic - say 3 % ± 1% - too many things need to be "justright". You simply can't monitor your smelter and its input closely enough, and there is no guarantee that you get the 3% stuff all the time. While co-smelting most likely was the technology used most of the time, the archeological evidence
strongly suggests that some more sophisticated alloying process must have been used after an initial (long) phase ofco-smelting and hoping for the best. So how was it done?
"Where is the problem?" you might ask. "So these guys eventually smelted pure metallic arsenic and mixed it withpure copper, melting it together, just as they did with tin somewhat later".
Good thinking. Just not correct, sorry. You cannot smelt arsenic in the usual way because arsenic doesn't melt but
turns into a gas right away when it reaches a relatively low temperaure of 613 oC (1135 oF). Skipping the liquid
phase and turning from a solid to a gas is know as sublimation. You know it from frozen carbon dioxide (or dry ice)that produces all these dramatic "fog" effects in theaters and night clubs when it sublimates in a water-richenvironment (the freezing / sublimation temperature is -56.4 °C (-69.5 °F)).
Arsenic is even worse than zinc that also vaporizes inside the smelter. Arsenic gas, of course, will quickly move up
the burden, oxidizing as soon as it meets oxygen. It will solidify again on cold surfaces - and it kills about everything
in its way!
So nobody made solid arsenic in ancient times. Co-melting solid arsenic with solid copper wouldn't have worked
well anyway, since most of the arsenic would have evaporated off long before the copper would get liquid.
Making a defined copper - arsenic alloy thus is quite difficult. But some of the ancient guys obviously had figured out
some way of doing that - but to archeometallurgists it is far from obvious how, exactly, they did it. There is a lively
discussion going on just now, fueled by new results coming in regularly. I will only give you a taste treat of what is goingon.
In a very recent paper Pernicka and others 1) present rather convincing evidence that at least the old Arismanians
in North-West Iran around 3000 BC deliberately produced speiss, an iron-arsenic alloy, which then was used to
produce arsenical copper. Most likely the ore "arsenopyrite" (FeAsS) was first smelted to produce speiss, whichthen was added to metallic copper or as ingredient for a smelter dealing with "proper" copper ore. The copper
produced contained arsenic (good!) and iron (bad!), but the iron more or less removed itself by oxidation if the copper
was melted in air.
Let's leave it at that and only give a passing look at a magnificent cast arsenic copper head that may be linked to the artof the Elamites , early masters of metallurgy. It is almost solid and thus rather heavy. The Metropolitan Museum in NYC
does not state if the arsenic content was high enough to produce the "silver sheen" possibly sought after for objects likethis.
Of course, the Metropolitan doesn't know exactly where this object comes from because, like most objects shownin the Metropolitan and many other museums, it goes back to illegal digging and trading if you believe Oscar
Muscarella, something I tend to do.

Head of a Ruler; arsenical copper, Iran; ca. 3200 BC 2000 BC
This might be Ur-Nammu (or Ur-Namma, Ur-Engur, Ur-Gur)ca. 2047-2030 BC who founded the Sumerian 3rd dynasty
of Ur 2)
Source: Photographed in the Metropolitan; NYC

Iron, Steel and Swords script - Page 307

A lot more could be said about arsenical copper but, to the best of my knowledge, archeometallurgists are far fromhaving come up with the "final" words to the topic. So let's desert the issue here and move on to:
BronzeCopper bronzes still are a diversified and thriving part of modern metallurgy. We use aluminum, lead, phosphorous,
silicon, and (insert name of chemical element) bronzes nowadays; plus tin bronzes, the "classical" bronze. Just to beclear: if I look at bronze in antiquity, I only mean tin bronze. Of course, antique bronzes also contain all kinds of traceor "dirt" elements besides tin - but let's not be picky and forget about that.
Bronze was THE first "metal" that changed humanity for good. Actually, you just as well could say it changed humanity
for worse because "industrially" produced bronze weapons allowed large-scale warfare. Slaughter on a magnitudeunprecedented in earlier times commenced around 2000 BC.
The word "bronze" appears first around 1730; it goes back to 13th century Italian "bronzo" meaning bell metal or
brass. The deeper roots are unclear; the Persian word for copper, "birinj", might be the source.
Bronze contains typically around 10 % tin; up to 20 % might also be encountered. The microstructure can be rather
complex. If you don't scare easily, you might consider taking a look at the phase diagram.
As we can see from the time / geography diagram of copper uses given before, all civilizations sooner or later changed
from making copper and arsenical copper to making bronze. It is just so much better:
Alloying is easy and controllable (provided you have tin) and doesn't kill you because the ingredients are nottoxic, in contrast to arsenic.
Casting is much easier (lower melting point and less problems with gases, etc.)
It has a very good corrosion resistance, making it suitable for ship fittings (very important around theMediterranean). Even ship propellers today are still made from some bronze.
Bronze is considerably harder then wrought iron or other Copper alloys then in use. Its Vickers hardness
ranges form 60–258 vs. 30–80 for the others.
How good is bronze with respect to hardness? Here is the decisive figure from the extensive work of Heather
Lechtman:

Hardness of Tin (Sn) and arsenic (As) bronzes incomparison to carbon steel.
Source: Heather Lechtman: "Arsenic Bronze: Dirty Copper or Chosen
Alloy? A View from the Americas"; Journal of Field Archaeology, Vol.
23 (1996) p 477 - 514

Surprise! Not only is arsenic copper just as good with respect to hardness than tin bronze, both are just as good asnormal steel not containing martensite from quenching. However, looking a bit more closely, and also atconcentrations of arsenic or tin far above 1 %, tin bronze wins against arsenic bronze with respect to mechanicalproperties and all the other points made above. Wrought iron or mild steel, however, has no clear advantage.
Making and casting bronze became a large-scale industry that came into its own around 1500 BC in the countries
around the Mediterranean. Many beautiful works of arts, in particular from the "late bronze age" (after about 1500 BC),
with intricate details are displayed in museums, including large sculptures and useful, if expensive objects like the one
shown below:

Iron, Steel and Swords script - Page 308

Life size bronze statue of some Roman senator.
2nd century AD, found submerged
Source: Photographed in the Archeological museum, Adana, Turkey.

Cauldron stand, around 1 000 BC, Cyprus
Large size picture
Source: Photographed in the "Neues Museum", Berlin; Germany.

The cauldron stand is displayed in the "Neues Museum", Berlin; Germany (that's where you find Nefertiti, too). It is
probably from Kition / Cyprus. Note that it was broken and mended rather clumsily.
A large-size picture of a ritual Hittite bronze axe can be found here
Tin bronze (Cu-Sn) alloy became known in the late 4th millennium BC and the beginning of the 3rd millennium BC in
Mesopotamia and western Iran (Khuzestan and Luristan regions). Early bronzes in some places might have been
produced by accidental co-smelting of copper ores and cassiterite (SnO2), the only tin ore around. Cassiterite is rather
rare, however, and it was and is a matter of much contention in archeology where the many bronze makers in antiquity
got their cassiterite or metallic tin from.
To cut a very long and confusing story short, copper and tin eventually became
high-volume trading items in the second millennium BC. Cyprus was a major
producer of copper, and the "ox-hide" copper ingots typically recovered fromtrading ships lost in the Mediterranean can be found in about any archeologicalmuseum in Europe - except the one on Cyprus, it seems.
A lot of what we learned about the metal making and metal trade in the heydays ofthe bronze Age comes from the "Uluburun ship" that sank around 1320 BC.
Below is the Berlin ox-hide copper "ingot"
An ingot, by the way, is a piece of relatively pure material, usually metal, that iscast into a shape suitable for further processing. Pieces of iron used for trading
thus are not ingots, even so some famous museums address their iron this way.
Iron, Steel and Swords script - Page 309

Illustr.
ModuleUluburun
Shipwreck

26 kg copper "Oxhide" ingot; 2 000 BC - 1 000 BC,
Cyprus
Source: Photographed in the "Neues Museum", Berlin; Germany.

"Oxhide" tin ingots are less ubiquitous but also exist. Cornwall in England (veryclose to the edge of the world in those times) was a known source, and a few more
had been known around 1980, but these known tin sources were simply not enoughfor the bronze industry. Meanwhile, more than 40 ancient sites of tin mining havebeen discovered in southern Turkey, and our knowledge of ancient metallurgy haschanged and improved ever since. I doubt that the last word is already out on the
topic and thus will not dig deeper into the subject.
More to tin and other early metals can be found from the link hub.

Link Hub
Early metal
technology

Making tin bronze thus could be done by simply co-melting the metals and I won't go into this anymore. Much trial anderror must have occurred, but eventually copper, tin, and bronze technologies were mastered quite well. Around 285 BC,
for example, some Chares of Lindos had the Colossus of Rhodes erected, a 30 m tall bronze statue, made from 500"talents" bronze (15 tons) and 300 talents of iron (9 tons). The Assyrian king Sennacherib (704 BC -681 BC) claims tohave cast a 30 ton bronze statue, and he might not have been the only one.
For comparison: The bronze Bavaria in Munich, cast around 1848, is 18.5 meters high and weighs about 87 tons.
The Statue of liberty in New York was erected in 1886, is 46 m tall with a 27 ton copper skin. 350 million $ wereraised to allow restoration of the statue in 1984, to give a rough idea of the kind of money one needs for showing off
in style.
The following figure gives an idea about technology development in the second half of the second millennium BC in IranComposition variation of copper / bronze from 1400
BC to 1000 BC
Source: Redrawn from: Omid Oudbashi, S. Mohammadamin Emami andParviz Davami (2012). Bronze in Archaeology: A Review of theArchaeometallurgy of Bronze in Ancient Iran, Copper Alloys - Early
Applications and Current Performance - Enhancing Processes, Dr.
Luca Collini (Ed.), ISBN: 978-953-51-0160-4, InTech
Iron, Steel and Swords script - Page 310

While the earlier samples - all from the same place and time - showed wild variations in the impurity concentrations,
500 years later the alloying element tin (Sn) was obviously intentionally added with a well-controlled concentration
around 10 %. Similar observations hold for other places.
All of this adds up to a simple conclusion: around 1500 BC a well-developed smelting technology was in place in many
areas of the Old World that could produce copper, tin, bronze (Cu + Sn) reproducibly and in quantity. Not to forget,
plenty of lead, silver, mercury and even brass (Cu + Zn) were also produced in more or less tricky ways. Some rather
involved techniques for parting and purifying some metals also existed, look up the "Early Metals" module.
The big question now is: Why the hell shouldn't those guys not have made iron and steel? I'll come to that but want topoint out already here that the emergence of iron and steel technology was not an isolated breakthrough but part of an
existing and already highly developed engineering system. If not much iron and steel was produced before 1200 BC, it
was not so much because it couldn't be done but because those guys didn't want to do it.
Before I now finally move to iron and steel, let's give a first quick look at how copper and iron smelting hang
together.
Speiss, Matte and Iron in Copper Smelting
As mentioned before, things get more complicated when you run out of clean, simple oxide or carbonate ores. Typically,
these minerals formed when the original ores came in contact with air (and water), and that happens when they areclose to the surface. All the way down in the bowels of the earth you have the original ores, typically sulfides. In
between things are complex. Surface-near ore might have dissolved in rain or ground water and then got washed down
deeper, where it precipitated again. Over million of years a complex mix of copper oxides, carbonate, sulfides andwhatnot built up, together with "mixed metals": ores containing arsenic, iron, antimony, nickel and whatever else wasaround.
Put sulfides or more complex stuff in your smelter and all hell will break loose, at least in an olfactory sense. Some ofthe sulfides and sulfates will become oxidized, and your contraption will exude hellish fumes like sulfur dioxide, SO2.
The oxidized ores can become smelted, i.e. turned into metal and carbon dioxide. The surviving sulfides will not get
reduced, however, but will generate trouble. It is therefore a good idea to "roast" your ores before you put them into thesmelter. Roasting turns sulfides into oxides. It doesn't need very high temperatures and can be done on a kind of
griddle with a regular fire below.
That's what ancient metal workers did when smelting copper was becoming a realindustry in the second millennium. Roasting ores wasn't particularly healthy,
especially if they also contained some arsenic, and it was a good idea to say
upwind of roasting griddles and smelters if you could. Ancient metal workers,
however, rarely succeeded in oxidizing the ores a full 100 %, and some sulfides
still went into the smelting furnace.
By then also some iron oxides went into the smelting furnace. Either because they
happened to be around or, more likely, because they were added intentionally as
flux. Iron oxides, together with the ubiquitous always present silicates (things
containing silicon dioxide, SiO2 ), produce fayalite, (Fe2SiO4), a great slag
material.

Advanced
Link
CyprusMuseumWe know that this was done because the slags from advanced copper and iron smelters are virtually identical intheir compositions! Smelters were also relatively large and could easily reach high temperatures around 1300 0C or
above. What happened under these circumstances is quite complicated and will lead us straight to iron smelting.
I have made clear by now that in the second millennium BC copper and tin smelting was done on a large scale, and witha rather sophisticated underlying technology and infrastructure . Around a smelter things still looked rather primitive butthat was and is deceiving.
It is important to realize that bronze wasn't the only metal (alloy) produced in antiquity. Including iron, there were the"seven metals of antiquity ": Gold (Au), Silver (Ag), Copper (Cu), Iron (Fe), Tin (Sn), Lead (Pb) and Mercury (Hg). In an
indirect way there was also Zinc (Zn) since brass, a copper zinc alloy, was made but without ever making elemental
zinc. This special module tells it all. Besides the smelting required for making all these metals except gold andmercury, other rather tricky technologies had been invented for purifying and "working" these metals. And quite a few ofthese technologies existed before iron was produced on a sizeable scale.
The question I'm leading up to once more is: why did iron come in so late? Is it especially difficult to make or what?
Before I go into this, let's ask a more general questions: what about the many other metals the periodic system provides
for? Why wasn't there nickel (Ni), cobalt (Co), chromium, (Cr), manganese (Mn), titanium (Ti), or platinum (Pt), to namejust a few? After all, we can be sure that after the discovery of smelting, some early enterprising engineers andscientists must have tried to pry out metals from about every rock and mineral they could find.

Iron, Steel and Swords script - Page 311

I have already answered this questions in parts - look up this module and here you find probably more than you arelooking for! Some metals simply cannot be smelted with carbon or carbon monoxide as reducing agent. Some
metals, including iron, could be reduced to the elemental stage but not melted and thus would not collect as liquid
pool in the bottom of your smelter. You only could "make" them if you managed to condense them in a safe place
below the tuyere in the solid state as a "bloom". While this works with iron, it may not work with other metals. I
actually don't know because nobody, it seems, has tried to do this, for example, with manganese (Mn, melting point
1244oC; 2271 oF), nickel 1535 (Ni, melting point 1453oC; 2647 oF) or cobalt (Co, melting point 1495oC; 2723 oF). It
may well be that for one reason or another, all these metals were just not "in reach" in antiquity but I suspect thatsome metals actually could have been made but had no conceivable uses. Future archeologists digging through theremains of the 20th century will not easily find indium (In) or gallium (Ga) since they were more or less useless,even so these metals were produced (as by-products of other metals). Only in the last few decades they havebecome key metals for some High Tech applications. Manganese (Mn) by itself, for example, wouldn't have been ofmuch use in the ancient world and alloying it to iron was impossible since iron could not be melted.
To make a long and complex story simple, I will just give you some results of what people in the second and particularlyin the first millennium BC experienced in their metal smelting practice.

1. The made Speiss
Speiss is a collective name for all kind of arsenides and antimonides produced in a smelter. Typically we have ironand copper arsenide. Since arsenic and antimony are metals (sort of), speiss is thus a metal (alloy), too. It came up
above in the context of making arsenic copper but it actually comes up all the time. If it wasn't smelted intentionally,
like in the case above, it was often a by-product of copper and lead smelting. Arsenic copper could be seen as anextreme case of speiss on the low arsenic side.
Much more could be said about the role of speiss through the millennia, not to mention the etymology of that word.
It's rather strange in English - and rather common in German: Speiss relates to "Speise"=food, "Speis" is southgerman dialect for mortar, and bell-makers still use "Speise" for casting bells. The verb "einspeisen" means to
inject, feed, supply with. You get the drift.

2. They made Matte
Matte, once more, is a collective name for metal sulfides produced in a smelter, typically Cu, Fe, Ni and Pb
sulphides. Sulfur (S) is not a metal, so sulfides aren't metals either. Matte may form as an intermediate productwhen smelting sulfide ores, especially for copper and lead. The reason for matte formation is simple: while you canturn a sulfide into an oxide with heat and oxygen, i.e. by roasting in air, you cannot reduce a sulphide by carbon
monoxide in the smelter. The sulfides getting down into the reduction zone thus end up as molten layer on top of
the molten copper layer and below the slag layer, since these liquids don't mix and arrange themselves according todensity.
Matte is a heavy brittle black stuff when solidified; it was considered a nuisance in early smelting days. It is actuallya very rich copper ore that can be smelted to the pure metals in a second go - if you know how to do it. I give you ahint: Roast it well in air and add silica as flux - that will do the trick. Much of the ancient matte has been used forcopper making somewhat later.
Matte is once more a strange word in English and not-so-strange in German.

3. They made iron
So you want to make copper. You feed your smelter with roasted copper (+ arsenic) ore; a mix of oxides andsulfides and God knows what else. You add some iron oxide and sand /silicon oxide as flux plus plenty ofcharcoals. Now consider:

Why shouldn't you get some iron too?

Iron, Steel and Swords script - Page 312

You expect to get some arsenic copper, some matte and maybe some speiss. Fine. You called the iron oxide thatyou put in your smelter "flux" - but you just as well could have called it "iron ore".
The truth is that you did get iron if you weren't careful. Making iron accidentally was a real hazard in copper
smelting, and could best be avoided by keeping the temperatures as low as possible. The reason is simple: you getiron by either reducing the ore at moderate temperatures high up in the burden or by reducing the iron-rich fayalite
slag swimming on top of everything else all the way down. As long as the iron produced remained solid, it couldn't
do all that much. At worst some particles, or a thin layer of iron particles, floated on top of your molten copper,
perhaps. However, if the iron could incorporate enough carbon to turn into cast iron, it liquefied and caused trouble.
At higher temperatures this is more likely to happen.
Copper containing as much as 35 % iron has been found. It is entirely possible that ancient copper guys producediron-rich copper quite often. It was, however, not too difficult to purify iron-infested copper: just melt it. Anything
above the solubility limit around 4 % will precipitate and float to the surface, where you can pick it up as iron ! The
rest you can get out by blowing air onto you liquid copper, oxidizing the iron but not the copper. Add a little silica
and you get slag, sitting on top and thus easily removable. There are two points of interest here:
The first point is: The ancient copper guys definitely knew about iron. However, what they got was iron contaminatedwith copper, and that was and is "bad" iron, with properties nobody likes. The second point is: The ancient copper
guys definitely knew about refining a metal by exposing it to oxygen in its liquid state. That, to refresh your memory,is the way steel is made from cast iron.

4. They made mixes of all of the above
The picture shows a kind of (highly idealized) worst case where you get everything during copper smelting.
Typically, either matte or speiss dominates in copper (sulfide) smelting. However, in lead smelting you might havegotten everything except, perhaps, the iron because you could keep temperatures relatively low.

What you found in your crucible
Even present-day copper smelters worry about matte and speiss. If you produce either one, your efficiency is not as
good as it could be. Indeed, modern conventional metallurgical wisdom has it that the production of speiss has to be
avoided at almost all cost, since it is more harmful than useful for any practical purpose
Last Words to Pre-Iron Metal Technology
What became clear, I hope, is that the beginning of large-scale iron smelting around 1200 BC did not signal theinvention of new and exciting technologies. Metal engineers by then had a long-standing tradition of making, refining,
and working with several kinds of metals in rather sophisticated ways. It is not that the couldn't make iron. They rather
avoided making iron because they had no use for what they got.
If I now have confused you in a major way - sorry. To
ameliorate the damage, I supply the very readable article"History of Mining and Metallurgy in Anatolia" that narrates
the big outlines of what was going on long ago in what now is
Turkey.
The authors are well-known archeometallurgists; you have run
across their names before in various parts of the hyperscript:Ünsal Yalçýn and Hadi Özbal . I can't give you a properquotation because the article as found in the Net does notgive its source - I hope the authors forgive me for including it
here.

Good
Reading
History Met.
Anatolia

In the next sub-chapter I will finally look at iron!

1)

Thilo Rehren, Loïc Boscher, Ernst Pernicka: " Large scale smelting of speiss and arsenical copper at Early Bronze Age
Arisman, Iran", Journal of Archaeological Science 39 (2012) 1717 -1727

2)

The Pages (of Blog) of Jerald Jack Starr, Nashville, Tennessee, USA, will tell yu far more about the Sumerians then you
ever wanted to know. They are great fun! Try it:
http://sumerianshakespeare.com

3)

Shlomo Guil: "!ALTERNATIVE DATING OF THE PRESTIGE ITEMS OF NAHAL MISHMAR , ISRAEL"; Published 2018;
unclear Internet source.
Iron, Steel and Swords script - Page 313

10.2 Making Iron

10.2.1 Early Iron

Note: I wrote another module about "Early Iron", containing some stuff I learned since I wrote thismodule, and focussing on complex early iron artifacts (=swords) from smelted iron
There is also a very readable recent scientific review of this topic
The Collapse of the Bronze Age and the Occurrence of Iron
Smelted iron in significant quantities appeared around 1200 BC. If you just scanned through the preceding chaptersabout making copper, lead, tin and bronze, you know that this was pretty late: about 3500 years after the first smeltingof metals and at a time when metal smelting, refining, melting, alloying and casting was already highly developed andabout to become a major industry. Moreover, smelting copper must have produced some iron on occasion. So why didiron appear so late? Is there a reason for 1200 BC as the decisive point in time?
What we know is that 1200 BC is a rather ominous date since it signals major upheavals around the Mediterranean,something known as "the Bronze Age collapse" followed by the first "dark ages".
In other words; the transition to the iron age in the larger Mediterranean was during a time period that was violent,bloody, and culturally disruptive. Severe changes in individual life-style frequently occurred, for example by your sudden
violent death. Killing and being killed was a style of live for marauders, pirates, their victims and the people / soldiers /mercenaries fighting them.
What about the rest of the world? No iron was used there in 1200 BC as far as we know (with the possible exception ofIndia). It is thus sufficient to concentrate on the Mediterranean at large.
What happened during the Bronze Age collapse? Extremely bad things. For example, between 1150 BC and 1206
BC we had the collapse of:the Mycenaean kingdoms,
the Hittite Empire in Anatolia and Syria,
the New Kingdom of Egypt in Syria and Canaan.
Of course we don't know exactly what was going on. People about to be killed and their killers leave no written
records, and in burnt-down and looted cities a lot was destroyed by definition. We might decry the scarcity of
written documents from this era but the people living then were probably more concerned about the violent
destruction of about every major city between Pylos (Greece) and Gaza (Sinai). This included major capitals like
Hattusa (capital of the Hittite Empire in central Turkey), Mycenae (Greece, near Athens, the major centre of Greek
civilization), Troy, and Ugarit (Northern Syria; important trade city and cultural center). The map in this link gives anidea of what was going on. What that also meant was that trade routes were interrupted, causing major economic
disasters and severe cultural cuts like a decline of literacy.
The collapse also occurred around the time when Moses and the Pharaos Ramses II/III were about - if the former
was about at all - and Troy fell to Achilles, Odysseus and so on, or at least to somebody. The still mysterious anduniversally feared "Sea People" also had a major hand in this. It wasn't just fun and games to fight them. Here is atiny part of a well-known sea battle that Ramses III actually won.

Iron, Steel and Swords script - Page 314

Fleet of Ramses II fighting sea people
Parts of a drawing of the 15 m × 2.5 m limestone relief from1170 BCin Medinet Habu, Egypt.
Large picture
Source: All over the Net

A first "Dark Age" hit the Mediterranean civilizations. In the view of some scholars it was even more disastrous then thedark ages following the collapse of the western Roman Empire. It remains to be seen if it shall have been worse than thedark ages that will follow the collapse of all of civilization in the not-so-distant future due to the present climate crisis.
There are even speculations that Hesiod's Ages of Gold, Silver, Bronze and Heroes, preceding the disastrous Age ofIron, recalls the cultural memory of the good old times before 1200 BC.
So what caused the Bronze Age collapse? And why am I harping on that topic considering the headline of this chapter?
Well, there is one possible answer to both questions. The bronze age collapsed because of
Climate change,
Volcanoes,
Earthquakes,
Migrations and raids,
Changes in warfare,
Ironworking,General systems collapse just so - or because some or all of the above occurred together.
I'm not sure that I have covered all bases, but those are the mainstream hypotheses. Pick your favorite one. Plentyof supporters and lots of written material can be found for either one. I'm of course interested in the "Ironworking
hypothesis", which states that iron-weapon wielding "migrators and raiders" overcame the conservative bronzeweapon equipped chariot-running armies of the great kingdoms. So there you are!
Now we must ask: Is that true? Did the "invention" of iron cause the bronze age collapse? Or was it rather the otherway around: the collapse caused a lot of creativity and inventions like ever so often in times of chaos?
If you go with the "iron caused collapse" hypothesis, you must now provide some idea about the identity of these"migrators and raiders". Once more you can take your pick. They were:the "Sea People" from above, who appear to have been a disparate mix of Luwians, Greeks and Canaanites,
plus possibly run-off slaves.
Indo-European tribes, such as the Phrygians, Proto-Armenians, Medes, Persians, Cimmerians, Lydians andScythians.
Pontic speaking Colchians, Hurro-Urartuans and Iranian Sarmatians.
Thracians, Macedonians and Dorian Greeks, who seem to have arrived at this time - possibly from the North crowding out the "Greek" or Mycenians.
Semitic peoples, such as Aramaeans, Chaldeans and Suteans – moving in possibly from the South-East.
People you know but would never have associated with these guys.
Latest news (e.g. in "Der Spiegel", 28, July 2016) cover the hypothesis that the Luwians from above actually had a
big empire of their own in West Anatolia that hasn't been properly "discovered" yet. Most of the time they wereindependent of the mighty Hititte empire to the East and around 1200 they took to sea faring and raided about
everything in reach. The "Greeks" (actually the Mycean culture) saw the opportunity to raid the Luwian town Troja
while the Luwians were busy elsewhere. They succeeded but their whole empire went down the drain anyway assoon as the got home.
Maybe that's how it was. The champion of that hypothesis is Eberhard Zangger, a kind of hobby archaeologist(like me, just more so). He became known by claiming that Troja was actually Atlantis. Again, maybe he is right. I
don't know. Mainstream archaeology, of course, is rather sceptical.
Well - as it turned out about 20 months later, mainstream archaeology was right. Eberhard Zangger fell for faked
evidence; read this article of "Der Spiegel".
Whoever and whatever. Here we are interested how all that relates to the rise of iron. Latest research or opinion has itthat the shift to iron occurred after the collapse, not before. Then it would be the disruption of the complex infrastructureneeded for bronze making in bulk, in particular the failing tin supply, that forced the metal-men to go for something that
could be made with just local stuff, and that means making iron.
And so on. Plenty of hypotheses, plenty of dispute, no certainty so far.
Personally I'm certain that there is some connection between the "Bronze Age collapse" and the dawn of the Ironage but I'm also certain that it is not a simple linear cause-effect relationship.
I do not know how all the events around 1200 BC hang together and why iron became popular then. I do know,
however, that some iron objects appear long before this time, and I'm relatively certain that ancient engineers could
have made iron before 1200 BC if they would have applied themselves. As we have seen, they quite likely madesome iron by accident as a by-product at copper smelting. So let's look at the archeological record - and the written
record.

Iron, Steel and Swords script - Page 315

Yes indeed! In 1200 BC some people could write very well in several kinds of languages and scripts. Cuneiform was
popular and used for international correspondence. But Egyptian or Luwian hieroglyphics, Phoenician, demotic, and so
on was also highly developed, not to mention whatever was going on in the Far East and China. Some of the stuff washammered into stones, carved into clay, written on papyrus, or scratched into wax tablets, and a little bit of what was
written survived.
Some people whom I truly admire can actually read and understand it today. Look at some of those old texts and you
see why I really think highly of the experts who can make sense out of that:

Luwian hieroglyphics, Phoenician and cuneiform
Source: Photographed at Karatepe / Internet at large

So what do we learn about early (iron) metal science and technology from what the ancients wrote about it?
Unfortunately not much! Those guys wrote mostly about other topics, typically about commerce, law suits, religion andadvertising (the deeds of the Noble). True, occasionally they were also concerned about serious issues like making beerand left recipes, but metal making? Sorry. No interest there.
Quite good engineers must have existed as early as 2500 BC. Just try to build a major pyramid with only bankers,
lawyers and priests and you see my point. Prolific scribes existed too, who covered every available flat surface in
Egypt with pretty hieroglyphics.
In what must be square miles covered with hieroglyphics, demotic or hieratic script, the total
amount of words or symbols dedicated to pyramids and pyramid building, something hard tooverlook even in present day Egypt, is exactly zero. Same thing for the extensive copper-tool
making business that went with pyramid making. Nada!
Same thing for the old Greeks, Assyrians, Hittites, whoever. At best there are a few indirect
remarks about commerce in metals that are open to interpretation and do not really help allthat much.
I have collected whatever there is - as far as I could find it - and you are welcome to checkthe module.

Misc. Link
Iron inwriting

It remains to ask our standard question now:

Who smelted Iron
for the first time?
When and Where?
And how, exactly?
You know by now that this it a rather naive question with no real answer at present (or probably ever). In the copper
case, one problem was to differentiate between native and smelted copper, in the iron case we don't have to consider
that. While native iron actually exists, it is exceedingly rare and has never been found in Eurasia. Instead we have a new
problem! We must differentiate between smelted iron and meteoritic iron!
By the way: So far and in what is coming I use the term "iron" for everything that is iron-based - wrought iron, steel,meteoritic iron - nickel alloys, whatever. For a lot of ancient "iron" the composition is not known anyway, and it just get's
to cumbersome to differentiate between all the iron manifestations.

Iron, Steel and Swords script - Page 316

Now I have opened a rather large can of worms. While you most likely will not findan iron-nickel meteorite on your next hike, quite a few have been found by
somebody else throughout the centuries / millennia. It is perfectly possible thatsome ancient people not only found a meteorite but used it for making iron things.
In fact, there is no doubt that some old iron things have been made from meteoritic
iron. However, the attitude of some scientists and curators to pronounce any pieceof iron from before about 1200 BC without a detailed analysis to be meteoritic ironis not scientific but lazy. Here is an example.
I give you a special module on meteoritic iron.

Advanced
Link
Meteoritic
Iron

Here I will only consider iron that is definitely from before 1200 BC - either smelted or meteoritic. It is not an easy thing
to do. Most recent articles about early iron typically spend many pages on discussing why some artifact that was
supposed to be early iron actually wasn't, why this or that analysis isn't quite right, why some piece thought to bemeteoritic iron actually isn't or the other way around. And so on. I could easily compile a much longer "confusing theissue" list than I did in the case of early copper but I won't .
Let's just look at some major objects and discuss a few general conclusions. For more details I will provide links.
What I'm going to look at is:
The Alaca Höyük dagger from 2800 BC - 2500 BC.
Pharao Tutankhamun's iron dagger from 1323 BC.
The "Great Pyramid Iron Plate" from around 500 BC (???).
Some unimposing artifacts from here and then.
The Alaca Höyük Dagger
Alaca Höyük is the present name of the tell or settlement hill that contains the remainsof the capital of ancient Anatolian kingdoms; see the link. Alaca Höyük predates theHittite empire, in which it became absorbed after about 1800 BC. It was discovered
and partially excavated rather early in 1910. Its fame comes from several royal tombs
that contained rich "treasures", in particular bronze "standards". It is the earliest "ironsite" I know; the link gives two more early iorn places.
Grave K contained the iron dagger. Here it is:Iron dagger from Alaca Höyük (ca. 2400 BC – 2300 BC
but maybe 2500 BC )and some bronze standards
Source: Museum of Anatolian Civilizations in Ankara.

Iron, Steel and Swords script - Page 317

Advanced
Link
Early Iron
Sites

Dagger from the Royal Tombs of Ur, ca. 2300 BC 2600 BC
Source: Internat at large

The dagger does show some wear and tear after having been buried for 4500 years in a tomb. But all things
considered it looks far better than its owner. It is similar to a (copper blade) dagger found in the Royal Tombs of Ur
as shown. The age of the Ur dagger seems be a bit unclear but it is comparable to that of Alaca Höyük.
Taking 1200 BC as the beginning of the iron age proper, the dagger precedes that date by 1200 years. It's like finding amobile phone in an 800 AD settlement, sort of early Vikings. In other words: discounting small and completely corroded
stuff, the Alaca Höyük dagger is the oldest undisputed sizeable iron artifact known at present.
Does that prove that some smart guys in Anatolia could smelt and process iron that early? Or, considering that Turks
are master traders, that the Alaca Höyük guys just knew from where you could import it? Did the smith who forged the
dagger use meteoritic iron or smelted iron?
The last question could be answered, at least in principle - see the link. However, anunambiguous answer needs a detailed metallographic analysis, partially destroying theartifact. This is unthinkable and thus the final word is not yet in. A Japanese team in 2008
published in a preliminary report that substantial amounts of nickel are contained in the "rust"of the dagger. If there is a final report I have failed to find it. A high nickel concentration does
indicate meteoritic origin, indeed, but does not unambiguously prove it. Moreover, older
investigations yielded much lower nickel concentrations according to Ünsal Yalçin 1).
More about early artifacts in this link

Advanced
Link
Early Iron
ThingsWhat can we learn from the Alaca Höyük Dagger? In my opinion, the following:
Somebody somewhere around the Mediterranean definitely knew how to forge iron around 2500 BC. This leaves
open if it was smelted iron or meteoritic iron. Forging the dagger blade from a lump of iron was not easy, and thenecessary technique was not known from the copper or bronze casting technology. While it is likely that"somewhere" is not too far away from Alaca Höyük, long distance trade cannot be excluded. It was definitely
established (via the Assyrians) somewhat later
Somebody somewhere possibly knew how to smelt iron or that iron could be produced unintentionally whilesmelting copper. This conclusion cannot be deduced from the dagger alone. There are other iron finds from Alaca
Höyük and elsewhere from the time period in question, however, and while these pieces are small and often fully
corroded, they were definitely not meteoritic iron.
Iron was an extremely precious metal and very rare in 2500 BC. There is only one iron dagger in the royal tombs
but plenty of precious bronze standards.

The Iron Dagger of Pharao Tutankhamun
Pharao Tutankhamun, or King Tut in short, was one of the least important Pharaos then but is the most famous Pharao
now. His present fame stems from the fact that his tomb is the only one that has been found with all his grave goods
still there.
Tutankhamun "ruled" nine years from 1332 BC – 1323 BC and died when he was about 20. From a recent DNA
analysis it is all but certain that the "enigmatic" Pharao Akhenaten was his father. Akhenaten abandoned
traditional Egyptian polytheism in favor of monotheism (first time that happened!) and moved the capital out to thesticks in Armarna. His "official" name was Amenhotep IV or Amenophis IV. This means "Amun is satisfied" while
Akhenaten means "living spirit of Aten"; with Aten a kind of sun God and the only one. His father was Amenhotep IIIof the Armarna letters fame.
King Tut's grave contained a lot of amazing stuff but here we are only interested in his two daggers. They were foundclose to his body in the gold sarcophagus making clear that they were among his most precious belongings. One of thedaggers had a gold blade, the other one a blade of iron.
Here they are:Iron, Steel and Swords script - Page 318

King Tut's gold and iron dagger
Large picture
Source: All over the Net

King Tut's dagger ties right in with the "Amarna letters", the archive of Amenhotep III, written in cuneiform and foundin Amarna. One of the letters from the Mittanni King Tushratta (a kingdom at the southern edge of the Hittite empire
in Anatolia and eventually absorbed therein) from about 1370 BC mentions the shipment of gifts to Egypt, including
daggers with steel and iron blades. It is quite possible that King Tut's dagger is actually the one his grandfather
obtained, or a new one from the same source.
King Tut's dagger is certainly the best conserved iron artifact from early antiquity. It is also enshrouded in mystery:it was never properly investigated as far as I could tell - when I wrote this in 2014. Now, in May 2016 things havechanged. The dagger has been investigated (up to a point); here is the original paper of Daniela Comelli and 12
coauthors. The study is of very high quality and leaves no doubt:

King Tut's dagger was made from meteoritic steel!
The same result was found once more by A. Jambon and published with great fanfare in Jan 2018. Here is thearticle by the Süddeutsche Zeitung, Germany's leading newspaper. The article can also serve as a prime example
for making all the usual mistakes concenring the smelting of iron - and it contains a few idiocies of its own!
Considering that the dagger was found in 1922, there would have been ample time to investigate before 2016. Why did ittake so long? There are two reasons I can come up with:
1. As soon as one visits the world-famous Egyptian Museum, the pyramids, etc. one perceives right away that mostpresent-day Egyptians, including the heads of the Antiquity ministry etc., are not scientifically interested in what
they have. They are only interested in how to make a buck out of it.
2. Methods for non-destructive analysis of artifacts did not exist many years ago. The powerful modern techniques(essentially X-ray based) that give unambiguous results are relative recent achievements.

Iron, Steel and Swords script - Page 319

So what do we know about King Tut's dagger?
It was often supposed to be of meteoritic origin. There weren't any data
substantiating this claim, until now. Contrariwise, many scientists up to now
supposed that it was made from smelted iron. That was a reasoable assumption
given the Armarna letters.
Iron was still an extremely precious metal and still very rare in 1323 BC, about 1200
year after the Alaca Höyük dagger. King Tut's iron dagger was his most valuable
possession and degrades the other stuff in his tomb, including all the gold, to justhigh-class junk. Just look at where if was found. One is tempted to invoke certain
symbolic meanings of swords (or daggers in the case of boys).
Somebody somewhere definitely knew how to forge iron around 1400 BC. And soon. See above.
It is obvious that the Egyptians made the hilt. They made it to match the hilt of thegold dagger, and they made it small (for the small hands of the Boy-Pharao Tut?). A
part of the tang of the blade is clearly visible. This may indicate that the Egyptiancraftsmen did not know how to shorten the tang.
The third point in the list above is of considerable interest. Did the person who made the dagger learn the forging
technique by working with meteoric iron only? That seems not very likely. We might rather assume that some iron
was actually made by smelting, either intentionally or as an (unwanted) by-product of copper smelting. Forging
techniques may have emerged by fooling around with this (inferior) stuff. The Armarna letters also indicate that iron
could be made somewhere in the Hittite sphere of influence. However, an object as large and as uniform as King Tut's
dagger could "obviously" not be made with the smelted iron from around 1300 BC.
The Ceremonial Axe of Ugarit
Ugarit was an ancient port city in northern Syria; its ruins are called Ras Shamra. Ugarit had close connections to theHittite Empire, sent tribute to Egypt at times, and maintained trade and diplomatic connections with Cyprus. The city
state was at its height from about 1450 BC until its destruction around 1200 BC by the Sea Peoples during the Bronze
Age collapse as related above.
Archaeological, Ugarit is considered quintessentially Canaanite. A brief investigation of a looted tomb was conducted by
Léon Albanèse in 1928 and serious digging was done since 1929 by archaeologist Claude Schaeffer from the Muséearchéologique in Strasbourg. Work continued under Schaeffer until 1970, with a break from 1940 to 1947 because ofWorld War II.
The axehead shown below is dated to the 14th - 13th century BC. It was found there quite early and alreadydescribed as having a meteoritic iron blade with a bronze socket inlayed with silver and gold.
On the back of the axe we see a boar, while the axe bade is sort of coughed up (or "roared out") by two lion heads.
The animals are rendered quit well, the gold and silver inlays, however, are a bit haphazard and leave something to
be desired.

Iron, Steel and Swords script - Page 320

Iron axe from Ugarit; 1400 BC - 1300 BC
Aleppo National Museum (we hope)
Source: Beyond Babylon: Art, Trade, and Diplomacy in the Second
Millennium B.C. , Aruz, Joan, Kim Benzel, and Jean Evans, eds.,
Metpublications, 2008 (free access)Very recently (end of 2017), Albert Jabon, mentioned right above, confirmed that the iron is of meteoritic origin.
Once more we have to accept that the axe is bo prove for the existence of an iron smelting technology before about1200 BC. It does, however, prove once more that some people knew how to forge iron rather early on, possibly
before they knew how to smelt it.
The Great Pyramid Iron Plate
The Great Pyramid of Giza or the Pyramid of Khufu (also called Cheops) has exercised scientists, normal people andcrackpots mightily for thousands of years. In the millions of Internet sites to the Great Pyramid, the contributions of realscientists (as opposed to self-proclaimed ones) are about as frequent as engineers in a fashion show. Interestingly, theother pyramids in Egypt are of only little interest to "Great Pyramid" fanatics, notwithstanding the fact that some of them
are almost as big and complex as the "Great" pyramid.
Some issues around the Great Pyramid even have the potential of turning real scientists into particular craggy
crackpots; witness, for example, Charles Piazzi Smyth and his "pyamid inch".
The issue of interest to us here is the "Great Pyramid Iron plate".
The history of this piece of iron is quite fetching. In 1837, Colonel Howard Vyse blasted away parts of the structurearound the supposed endings of the "air shafts" leading up through the bulk of the pyramid to outlets high up on theoutside. Here is the present-day ending of the southern air-shaft from the King's chamber. At least two layers ofstones are missing.

Iron, Steel and Swords script - Page 321

The coming-out of the air shaft of Khufu's pyramid
Source: Rudolf Gantenbrink 1999 Internet page (http://
www.cheops.org)

On Friday, 26 May 1837, after dynamiting away for two days, a man in Vyse's team, one J.R. Hill, discovered a flat
iron plate about 26 cm × 8.6 cm in size with a thickness ranging from 4 mm to nearly zero.
Vyse proclaimed it to be "the oldest piece of wrought iron known" and set off an ever-lasting dispute. The iron piece
was brought to the British Museum where it still resides.
Here it is:

The Great Pyramid Iron Plate - front and backThe missing corner was sacrificed for analysis.
Source: British Museum

I will not enumerate all the opinions put forth by half-way knowledgable or at least prominent guys in the 150 years or soafter the discovery of that unassuming iron artifact. I will only mention two:
The mining engineer Herbert Hoover (1874 – 1964), together with his wife, translated in his spare time the famousbook "De Re Metallica" by Agricola, from Latin to English. in 1912. In some footnotes he offered his thoughts on
the history of iron, in particular that the iron age began much earlier than is usually assumed. The iron plate ofGizeh was interpreted as a clear hint that very early Egyptians could produce iron. And yes, H. Hoover was also the
31st President of the United States from 1929 to 1933.
Those were the good old times when American Presidents could afford to be intellectuals. But then as now, they
were not necessarily always right with their opinions.
Oleg D. Sherby; Emeritus Professor of Materials Science and Engineering, Stanford University, and Jeffrey
Wadsworth, President and CEO of Battelle Memorial Institute since January 2009, are not exactly crackpots but
eminent and well-known Materials Scientists. They go right along with President Hoover's view of the earlyprominence of iron in a number of papers and also refer to the Great Pyramid Iron Plate as an important artifact
supporting their views. They actually go as far as to suggest that Neanderthal man might have known how to makeiron more then 40.000 years ago 4) .

Iron, Steel and Swords script - Page 322

If these eminent men view the Great pyramid Iron Plate as the pivotal point for a new and revolutionary view on humanhistory, it behooves us here to consider what we know about that piece of iron. Quite a lot, as it turns out. There havebeen two in-depth metallurgical investigations. The specimen were cut from the plate, witness the "missing corner" inthe picture above.
The first analysis was done in 1989 by El Sayed, El Gayar and M.P. Jones 2). They reported that
"The plate consists of numerous laminates of wrought iron and that these laminates have been inexpertly
welded together by hammering. The various layers differ from each other in their grain sizes, carbon
contents, the nature of their non-metallic inclusions, and in their thicknesses..."In addition, they also found"small, but significant, proportions of gold ... in one of the oxidized layers and it is thought possible that theplate may, originally, have been goldplated".
Their final conclusion was:
"It is concluded, on the basis of the present investigation, that the iron plate is very ancient. Furthermore,
the metallurgical evidence supports the archaeological evidence which suggests that the plate wasincorporated within the Pyramid at the time that structure was being built".
So there!
The second analysis was published in 1993 by Paul Craddock and Janet Lang of the British Museum 3). The
authors went through all the proper moves of an in-depth analysis of both a fresh piece and the old piece
investigated 4 years earlier. Their major findings were:"The structure of the iron in both sections is very similar and we are in broad agreement with El Gayar andJones on its identifications if not interpretation".
"We must report that despite extensive searches no trace of gold could be detected, and it is our firm
opinion that the original report of gold is incorrect".
The iron comes probably from a post-medieval and still crude cast-iron technology plus a "fining process" formaking steel.
"This (the findings) strongly suggest that the plate of iron from the great Pyramid is of no great antiquity".
So there???
While I'm inclined to go with the second analysis, the issue remains open. Is that piece of iron very old or not?
Determining the age by a radiocarbon analysis might provide certainty in the future, maybe. Until then we need to wait.
We might ask ourselves another question: does it matter if that piece of iron is about 4500 years old or rather recent?
Obviously it matters very much to Sherby and Wadsworth and everybody else who believes that the "official" history ofmetals in general, and that of iron in particular, as put forward by archeologists and their ilk, is majorly flawed.
We already faced the "really no gold use before about 4500 BC ?" enigma, and now we have the "smelted iron use
well before about 1500 BC - yes or no?" controversy. Would the Great Pyramid Iron Plate, if really about 4500 years
old, tip the scales in one way or other?
I doubt it.
First of all, both investigations agree that the plate is made from smelted but very "bad" iron. It does thus not attest
to a well developed technology.
Second, there are a few more but less well-known iron artifacts from well before 1500 BC (mostly disputed, ofcourse) that indicate that early mankind occasionally did make iron. This could have happened accidentally during
copper smelting or because somebody experimented a bit without a clear goal in mind. We don't know.
We do know, however, that iron objects were considered to be extremely precious at least up to 1300 BC, witness
King Tut's dagger and the royal correspondence concerning iron. As far as I'm concerned, this proves beyond
reasonable doubt that no significant iron smelting and working occurred in the "larger" Mediterranean before about1200 BC. The pyramids, in other words, have not been made with iron / steel tools.
On the other hand we cannot rule out with certainty that the Neanderthals, or other very early cultures might havemade iron that either has vanished without a trace by now or hasn't been discovered yet. It is just is not very likely;
just as in the gold case.
The real enigma thus is:

Why was no iron made before
about 1200 BC?
The technology for smelting iron was available!
To put it in other words: Why did the iron age "proper" start around 1200 BC and not much earlier? That brings us
right back to the beginning of this chapter.
The answer, whatever it will be in the end, must include an often overlooked part:

Iron, Steel and Swords script - Page 323

It is a long way from smelting some iron to making
an iron artifact like a knife blade
Iron smelting going well always produced solid iron. If it resulted in something liquid it was cast iron and that wasquite useless in antiquity (with the exception of China). While liquid metals as in copper smelting etc. just "run out"of your furnace if you open a tap hole, or will be found neatly solidified at the bottom, you now must learn how to get
this solid iron called a "bloom" out of your smelter. Then you must learn how to refine this (very dirty) bloom inseveral stages, all involving "smithing" and requiring a suitable hearth. Finally you must learn how to make objects
exclusively by "banging" your iron with a hammer, and how to make big pieces by joining smaller ones by fire
welding. On top of that comes the art of thermal treatments, including hardening by quenching.
All of that is competely new. Nothing remotely similar is needed for copper and bronze technologies. Many
amateurs and professionals are out there doing iron smelting and iron working experiments right now, and they all
learn the hard way that the whole "technology chain" is far more difficult to master than you could possibly
imagine! It is not something that you learn during a weekend with the boys.
This simply means that it takes a while before the technology is established by trial and error. But after that has
happened in a few places, it can be passed on from master to apprentice and start to spread.
Before I go deeper into all this, I will quickly run through a few more old iron objects.

Old Iron - Odds and EndsÜnsal Yalcin in his 1999 paper1) lists more than 10 iron objects from 10 Anatolian sites from before 1200 BC. The Alaca
Höyük dagger is there, of course but typically the description is "needle", "jewelry", "fragments of unclear uses","weapons" or "knifes". Some of the needle heads were gilded, and the meteoritic origin of some objects could be ruledout because they contain no appreciable nickel. Some objects are likely not really iron, and others are completely
corroded with hardly any iron left inside (easy to find out because they don't react to a magnet).
Jane Waldbaum in her masterly review from 1999 lists around 150 early items from all over, again with denominations
like anklet, bracelet, ring, pin (or jewelry in other words), piece, lump, fragment, wire, rod, etc. Nothing very substantial.
She discusses these artifacts at length and I can't resist to give a few quotes:"With the exception of ...(some 10 objects) ... all the recent additions (about 50) to the repertoire (about 100
objects) are either jewelry pieces or fragments that cannot be identified".
"(...) several pieces, earlier said to be iron, have been shown not to be on recent examinations".
"The point .... (if Ni always signals meteoritic origin) .. has also been raised by Piaskowski (1982) who performed
metallographic analysis on a series of nickel-rich iron objects .... and showed that they had, in fact, beensmelted" .
"Analysis of several 100 Late Bronze Age artifacts from .... Timna .... of southern Palestine, in fact, showed'substantial quantities of metallic iron in the copper' (Rothenberg 1988:12), while analyzed iron artifacts from thesite contained significant amounts of copper".
I could not find any pictures of the early stuff, but the picture below probably comes close. It shows rings andneedles from the Karagündüz necropolis in the Van area (eastern Anatolia) from the 10 / 11th millennium BC, a time
horizon when iron in this area became rather common. The older stuff mentioned above is rather less wellconserved.

Small iron things (jewelry) from 1100 - 1200 BC(Karagündüz, Turkey)
Large picture
Source: Hadi Özbal, Istanbul University:"Ancient Anatolian Metallurgy",a Powerpoint presentation in the Net.

Iron, Steel and Swords script - Page 324

What do we learn? In the first place, we see how science works. It will eventually arrive at "The Truth" or at least get very
close, but rarely in a straight-forward way. Typically we get there with a lot of back-and-forth movements, long pauses,
plus a few excursions into mined areas. The path is lined with fallen warriors and memorials for the heroes; not all ofthem deserved.
Otherwise we learn once more what we already know or at least suspected:
There was definitely non-meteoritic iron in use early on.
Early iron was rare and therefore often used for jewelry. Then as now, only the elite could afford expensive
jewelry.
Copper smelting quite likely did produce some iron every now and then. It's not "good" iron but still usable forsmall things.
All in all, I'm inclined to make a strong case for:

There was no sizeable iron production
anywhere on this planet
before - roughly - 1200 BC !
That's a strong statement. It might be wrong but for the time being I'll stick with it. The question, once more, is:why? Why was the iron age kicking in so late? Let's look at some of the explanations offered.
What Started the Iron Age?
The first hypothesis assumes that people had no choice.
They still would have preferred to make bronze but the mayhem of the bronze age collapse, with constant warfare andbreakdown of trade, in particular the tin trade, put an end to that. If you can't get tin, supposedly always coming from far
away sources like Cornwall / England or Afghanistan, you can't make bronze.
This hypothesis rests on two assumptions:
1. People preferred bronze to iron. That implies that they actually knew iron and how to make it but wouldn't do thatas long as they had bronze.
2. Tin supplies broke down. This implies that there were no relatively near-by tin sources that could be exploitedeven under adverse circumstances.
Let's look at these two points in some detail.

1. People didn't like iron? Could that be true? After all, the few early iron pieces found were obviously considered to
be of tremendous value, and the rich and powerful used early iron for jewelry or other showing-off items!
That is certainly true - but does not exclude the possibility that normal people didn't like iron for everyday things.
There are a number of possible reasons for this:Any iron / steel produced in whatever way and for whatever reason, could not be melted and cast. If castingis your main metal-working technology, you do not like that. Making metal objects by forging instead of
casting needs all kinds of skills and tools that people simply didn't have.
If some cast iron was accidentally produced (unlikely but possible), it could be cast but was brittle and very
hard and thus not all that useful. It could certainly not replace most bronze objects.
The iron produced as a by-product of copper smelting always contains substantial concentrations of copper.
Unfortunately, copper in iron makes for rather bad steel, difficult to forge. Many an early smith or metal
worker who tried to make something from the stuff probably gave up in frustration. The rest made small things
like rings and pins that could be sold to the lazy part of the population that didn't need real tools.
Attempts of direct iron smelting might have produced wrought iron in a solid "bloom". The chain of processes
needed for making anything from that (starting at removing the bloom, compacting it while still hot,...) was
neither well-known nor obvious. It involved a lot of work, and final products were no better than bronze
counterparts. Wrought iron is not harder than bronze, remember? So why bother? The fact that the bloom
was most likely a very inhomogeneous mixture of all kinds of steel didn't make things easier either.
All that iron stuff corrodes or rusts. Some kinds more than others, but all kinds far more than almost
completely corrosion-resistant bronze.
Iron smelting in all early versions is far less efficient than copper smelting. You put a lot of valuable charcoal,ore and flux into you smelter and get only a little bit of iron, if any at all.
Quite a list! Looks rather convincing to me. At least it is easy to see that iron might have had a bad image with early
metal engineers. Now let's consider the positive points:
From iron one can make silvery or silvery-white objects. Considering that this appearance was much indemand, it might have had a small but important market. Not only could it replace silver to some extent for
Iron, Steel and Swords script - Page 325

making jewelry, it was somewhat different, more expensive and exotic, always a good point when selling to
the rich. Even today the really rich go for platinum jewelry instead of just bourgeois silver.
With luck, some good carbon steel could be produced on occasion. With even more luck, objects forgedfrom it would case-harden if quenched. The final product then might have been far superior to the best bronze
stuff., especially if used for knifes and swords.
Smelting and working wrought iron is easy - if you know the tricks. Very simple furnaces, fed with local stuff,
would do. Almost everybody could do it, and you didn't need to import anything (like tin for bronze). While
wrought iron swords and knifes were no better than bronze stuff, they were no worse either and you, or yourlocal smith, could make them. And wrought iron was just fine for all the everyday stuff like pots, pitchforks,
hooks, nails or chastity belts.
I think we have sufficient reasons to accept that people might have switched to iron when tin supplies broke down.
But did that really happen?

2. Until about 20 years ago, archeological research had identified only a few places where tin mining took place inantiquity, all of them rather far away from the centers of bronze technology. Meanwhile major tin sources, goingback to the third millennium BC, have been found in Anatolia, e.g. the Kestel mines in Göltepe. There might bemore tin sources not all that far away from the bronze makers not yet identified, and this means that tin trading
could still have occurred.
Moreover, with modern techniques it is possible to determine where the tin in some old bronze objects came from.
Results of analyzed bronze objects from around 1200 BC or even younger seem to indicate that the tin trade was
not suffocated in a major way around 1200 BC. And we do know that bronze never disappeared; a lot of bronze wasmade parallel to iron all the time.
The last word isn't in yet but we might conclude:

The iron age did not start because alack of tin after 1200 BC.
The second hypothesis suggests that people on Cyprus or Palestine mastered the production of steel around 1200 BC,
including quench-hardening, and that the new and superior technology spread from there.
This pronouncement is based on many steel objects found in Cyprus, dating to the early 11th century. Some knifes
even must have been quench-hardened and tempered! Similar findings are reported from Palestine, and I take thisinformation (like much of the rest) from Jane Waldbaums's article. The link provides for the aticle; here is the quote
However, the carbon concentration varied quite a bit between all the artifacts investigated. It is thus not clear if the
production of good steel was accidental or the result of determined efforts that were just not always applied or failedon occasion. It is conceivable, of course, that some metal engineers became aware of the stupendous possibilities
of iron /steel, and dedicated time and effort into finding out how one could produce the good stuff in a more
systematic way.
There are parallels to this in modern science. The potential of semiconducting materials for "electronics" wasrecognized around 1930 but the science of semiconductors was not well understood. Nevertheless, some products
based on semiconductors were made and sold, e.g. the early "crystal detector" radios or the selenium (Se) based"diode" rectifiers still used in electron tube devices in the 60ties of the last century. Nobody quite knew how thesethings worked but that didn't prevent their large-scale use.
Even more to the point, the first "real" commercial transistors, based on a well-understood theory, were made from
germanium (Ge) in 1950 / 60. Silicon was just not up to the job, even so it "occasionally" did produce much better
products. We (I include myself here) first had to learn how to make it "just right", and how to process it. After thatsilicon completely crowded out germanium, just like iron / steel crowded out bronze.
My conclusion isIron crowded out bronze for "cheap" objects after the complete
technology chain became known.
The third hypothesis invokes ecological reasons. In particular Theodore Wertime, one of the great old men ofarcheometallurgy, argued that the bronze industry around 1200 BC had exhausted the supply of wood / charcoal andwas forced to switch to the more fuel efficient iron smelting. Two questions come up in this context
1. Is there archeological evidence for heavy deforestation in the areas of concern?
2. If yes, would iron smelting indeed provide a way out of the problem?

Iron, Steel and Swords script - Page 326

1.
2.
The answer to both question is: No! There is evidence for some deforestation but it is not conclusive. And ironsmelting is not more fuel efficient than copper smelting, in particular if not yet optimized. The demands on charcoal
are just as large than for copper smelting, at best there is a marginal advantage. This is the present view ofmainstream archeology.
I have a personal view on this. If charcoal supply to a metal making and working center becomes difficult because
the stuff has to be transported over larger and larger distances, iron smelting does offer an advantage: Moving yoursmelter and the "smithy" to where the charcoal is will be far easier than moving your bronze production place, andthe chances of finding iron ore nearby are much larger.
The smelter may be less efficient but is smaller and easier to make, and you don't need the mould makers, thepeople needed for alloying, melting and casting the bronze, not to mention the traders for charcoal, ore and tin. All
that is either not needed or available close by. The infrastructure for making iron things is simply far less involved
than that for making bronze things.
The issue thus may not only concern the charcoal supply. The advantage of iron is that decentralizing the whole metalbusiness, advantageous for several reasons in times of turmoil and chaos, was easier done for iron in comparison tobronze.
Of course, the people involved did not get together and decided that it was time to decentralize, and to do that byswitching to iron technology. It just happened by straight evolution. Some yokels entrenched in remote woods could still
produce (bad) iron when the big metal center close to the city was overrun and destroyed by some foes together withthe city. Survivors took what they could get - a not-so-good iron knife / sword, after all, is still better than no knife /sword, and the increased demand triggered improved technology.
We might conclude:

Making iron is easier than making bronze
with regard to the necessary infrastructure.
That is advantageous in times ofchaos, crumbling empires and general warfare.
I'm sure that there are more possible scenarios that have been put forward by experts - but I will stop here. You are free
to subscribe to any of the three hypotheses discussed. You will be in good company and you will have someadversaries.
As far as I'm concerned, I believe that everything mentioned above played a role somewhere and sometime, but not
everywhere and all the time. It is a simple game of evolution once more. Smelting processes always contain a certain
mutation rate, i.e. variations in the process for all kinds of reasons. On occasion a mutated Cu smelting process
produced some iron, for example. Maybe the quality of the charcoal was a bit different, maybe some worker made anerror in the amount of flux (often iron oxide) put in the smelter, whatever. Some of those mutations produce a little iron,some produce something else, and some do not noticeably change the product. As long as the environment is stable,
mutations in the output are thrown away and thus do not survive. There are long and learned papers to a Darwinianevolution / mutation process concenrng the makin of iron 4)
If the environment changes - your empire breaks down, no more tin coming in this month, your charcoaler has been
killed by enemies, your local elite-customers ran out of money - mutations are seen differently. "Natural selection" will
now see to it that those mutations thrive that allow the people involved to cope better with the challenges of the changed
environment. In time the mutations take over. This can happen rather quickly because in troubled times the "mutation
rate" in bronze technology must have gone up, since people were forced to experiment. You can't get your usual
ingredient for flux anymore? Before you stop operations you try some alternative. You have mutated the process! The oldprocess is kept for whatever it could still do better. Bronze never went quite out of style, and Roman officers still had
bronze swords in use, for example.
Nobody knows what really happened 3200 years ago. And nobody will ever know in detail. We don't know exactly
what caused the first and second world war either, otherwise there wouldn't be so many books and conflicting
opinions. Why did the age of electronic computers start in the second half of the 20th century? Was the technology
invented at one place and then spread? Views differ widely, something quite amazing because electronic computerswere clearly a German invention, of course.
Seriously now: major inventions leading to completely new products and life-styles - cars, electricity. computers,
refrigerator, washing machines, television, oral contraceptives, .... - are always coming up more or lessindependently at several places around the same time. All that is needed is a bit of communication across theborders. I see no reason why it should have been different 3200 years ago.
Now that we have finally started the Iron Age, let's smelt some iron and steel.

Iron, Steel and Swords script - Page 327

1)Ünsal Yalçin: "Frühe Eisenverwendung in Anatolien", Istanbuler Mitteilungen, Band 48 (10998) p. 79 -95

2)

El Sayed, El Gayar and M.P. Jones: "Metallurgical investigation of an iron plate found in 1837 in the Great Pyramid at
Gizeh, Egypt" ,Journal of the Historical Metallurgy Society, Vol. 23 No. 2, 1989, pp. 75-83.

3)Paul Craddock and Janet Lang: "Gizeh Iron Revisited", JHMS 27/2 (1993), pp. 57 - 59.

4)

Oleg D. Sherby and Jeffrey Wadsworth: "Ancient blacksmiths, the Iron Age, Damascus steels, and modern metallurgy",
J. Mat. Processing Technology, Vol. 117 (2001) pp. 347-353.

5)

Michael F. Charlton, Peter Crew, Thilo Rehren and Stephen J. Shennan: "Explaining the evolution of ironmaking recipes– An example from northwest Wales", Journal of Anthropological Archaeology 29 (2010) pp. 352–367

6)

Jane C. Waldbaum: The Coming of Iron in the Eastern Mediterranean". In "The Archaeometallurgy of the Asian Old
World", edited by Vincent C. Pigott, University of Pennsylvania Monograph (1999), p. 27 - 57

Iron, Steel and Swords script - Page 328

10.2.2 Smelting Iron
Remember?
Maybe you read the module about smelting science, may be you didn't. If you read it, you probably forgot most of what
you read. I'm constantly amazed myself on what I find in all those modules because I forgot it - and I actually wrote
them.
Then there are the copper smelting modules. Remember this picture? I thought so.
For those of you with slight guilt feelings by now, here are the links plus a short description of the contents.

Smelting
Science 1
Furnace andFire

Smelting
Science 3
Smelter
Technology

Smelting
Science 5
Slag;
TricksSmelting
Light
Smelting
copper

How hot?
Economy of size.
Air flow stuff.
Different fuels.
Furnace examples
The ideal smelter.
The real smelter.
Tuyeres and air flow.
There are many important
temperatures!

Size limits.
How hot should it be?
No good slag, no good
smelting.
Crucible smelting withoutCO.

Smelting
Science 2

Charcoal properties.
Size counts!
Tree type too.
The dual role of charcoals.

CharcoalTechnology

Smelting
Science 4
Air
SupplySmelting
Science 6
SeriousIron Smelting

How it works for copper.
The gases in a smelter.
Primitive copper smelting
in salad bowls.
Progress with time

Air supply is everything!
Blowpipe limits.
Natural draft and wind.
Only bellows allow good
smelting!

Boudouard equilibrium
Baur-Gaessler diagram
Why smelters produce
only wrought ironWhy they don't

Don't despair!
There is light a theend of the tunnel(and my wife).
Innards of Ephesus
amphitheatre

For those of you who couldn't pay attention because they had to get some beer or do some gender mainstreaming, I will
now repeat the essentials by a direct comparison of copper and iron smelting. Below is a very schematic picture of asmelter. On the right we go for copper, on the left for iron.

Comparison of copper and iron smelting

Iron, Steel and Swords script - Page 329

Let's see what both smelting experiments have in common:
We need to produce a lot of heat = energy, and for that we burn = oxidize charcoal at the bottom part in the heatgenerating zone or oxidizing zone. We need to supply a lot of air through a "tuyere" for this, and it must be justthe right amount. Not too much because all the oxygen (O2) in the air supply needs to be used up after a few
layers of charcoal, and not too little because we need to get the temperature up quite a bit. The combustion
products of the "burning" charcoal layer is hot carbon dioxide (CO2; according to C + O2 ⇒ CO2 + energy) plus
hot nitrogen (N2) from the air.
The charcoal layer above the burning layer can't burn because there is no more oxygen. If it gets sufficiently
heated by the hot gases flowing through, it will produce (hot) carbon monoxide (CO; according to C + CO2 +energy ⇒ 2CO). This reaction does not produce energy but consumes quite a bit, meaning it cools the gases.
Ideally, the burning layer should be at least at 1200 oC (2192 oF) and the carbon monoxide producing layer at
least at 800 oC (1472 oF) if the smelter is supposed to work efficiently for both copper and iron. That is not allthat difficult to achieve - provided you have a decent air supply, always necessitating bellows.
We now add a certain amount of ore (and maybe "flux") to the charcoal and feed that mix (called "burden") into
the smelter from above. The flux is supposed to generate slag, together with all the other stuff in the smelter
including "gangue" (the "rock" fragments coming with the ore) and often the clay from the smelter wall material.
The hot carbon monoxide "reduces" the ore, i.e. turns it into pure metal (abbreviated "M"); most simply according
to MO + CO + energy ⇒ M + CO2. All that chemistry simply states that both metal and carbon monoxide fightfor oxygen. The carbon monoxide likes to have more oxygen (turning it into carbon dioxide) and the metal ores
like to keep the oxygen it has attached to the metal atoms. The carbon monoxide wins the battle for oxygenagainst some (not all) metal ores if the temperature is high enough. For copper and iron it always wins. This
reduction reaction (= stealing of the oxygen) starts already at rather low temperatures around 400 oC (752 oF)
for copper and for some iron ores. The reduction uses up energy and thus cools the smelter. Reducing iron takes
substantially more energy than reducing copper and altogether needs somewhat higher temperatures.
In both cases the ore is turned into the metal with everything being solid all the time. The reduction process
fragments the ore pieces into many small and "spongy" metal particles. We now have small metal particles
relatively high up in the smelter, mixed with not yet fully reduced ore. The flux materials have also started to react
to what we find later in the slag but everything is still solid. At best some glassy very viscous goo is formed.
As the charcoals at the bottom part get turned into gases, the whole burden moves slowly down - charcoal, ore,
metal particles, flux material, slag goo - getting hotter all the time. If that would be all, the metal particles would
start to re-oxidize as soon as they move into the oxidation zone and no metal would be produced!
The slag, after turning liquid, collects in the bottom (as in the picture above). It also might be tapped every oncein a while through a tap hole in the "right " position. Accordingly, you produce "production slag", a sort ofcylindrical cake found in the bottom pits of furnaces, or tap slag outside the furnace, irregular pieces often with aflow pattern; see below.

Left: Production slag (about 200 kg, Denmark, 200 AD- 500 AD)
Right: Tap slag (unspecified)
Source: Left: Photographed in Copenhagen museum. Left: English
Heritage, May 2011; open access Internet

A first conclusion emerges. The metal must go through the oxidation zone quickly. That is easiest if something is liquid:

Iron, Steel and Swords script - Page 330

If we want to produce metal we need toliquefy something above
the oxidation zone so it canmove down quickly.
Either the metal, the slag
or - best of all - both!

Now to the differences in copper and iron smelting. This will also make clear why something liquid is needed:
Reducing iron ore generally takes more energy than reducing copper ore. You must therefore increase the ratio of
charcoal to ore since you need to burn more charcoal to supply more energy.
In the almost unavoidable presence of silicates (typical gangue material or the stuff coming with the ore), ironoxide or iron ore is a good flux material. That's why copper smelting was routinely done with iron oxide as flux
material. It is then no wonder that iron was produced accidentally every now and then during copper smelting. In
fact, as copper smelting techniques progressed, this became a problem.
Iron smelting thus can be a "self-fluxing" process, meaning you do not have to add flux material as long as theubiquitous silicates from the gangue were around. Early iron smelters indeed did not use flux materials. Selffluxing also means that your smelting efficiency goes down, since quite a bit of your ore ends up in the slag as"fayalite", an iron silicate and a major part of slag. With bad luck, slag might have been the only thing you
produced in your supposed iron smelting.
The metallic copper particles are produced in the solid state, just as the iron particles (or any other metal
particle in normal smelting). They will melt, however, while still above the hottest part of the smelter, the oxidizingzone where the charcoals burn because there is oxygen. Being liquid, the copper now can trickle down much
faster than the whole burden moves down, and thus pass through the very hot oxidizing zone without becoming
re-oxidized again. It collects as a liquid at the very bottom, protected by a liquid layer of slag that collects on topof it.
The metallic iron particles will not melt. They would move down slowly with the burden and re-oxidize in the hot
oxidation zone - if they don't become part of the liquid slag. Sorry. No liquid slag - no solid iron!
Solid iron is only produced as a bloom if liquid slag envelops the iron particles above the oxidizing zone andsweeps them down quickly to a half-way protected place. There a bloom will grow because iron-particle
containing slag is raining down on it, and the iron particles stick together.
However, in a "badly" run smelter, some iron particles produced close to the edge of a smelter may make it downon their own because they might happen to move through "cool" oxygen-deprived places in the oxidation zone.
Such a "protected place", with some CO around that's made right there, might be behind the tuyere , in particular
if it sticks too far into the smelter and the air flows out too rapidly. Alternatively, it might be on the opposite sideof the tuyere, in particular if the air flows out of the tuyere too slowly and doesn't quite make it to the other side.
This is schematically illustrated below. Of course, a bit of liquid slag also helps. Mulling this over it becomes
clear that the exact geometry of the tuyere (height, angle, diameter, penetration depth into smelter) will be
important.

"Protected zones" where blooms can grow
Top: air velocity too slow
Bottom: air velocity too large
Iron, Steel and Swords script - Page 331

This is an extremely simplified description of what is going on inside a smelter. I bet that you had no idea that it would
be that complicated, even in the most simplified version. I'm now going to answer a few of your questions.
Question: "It seems that reduction to metal always takes place in the solid state, and that melting the metal above
the oxidizing zone is good. So why don't we just increase the temperature in iron smelting to well above the melting
point of iron? That should be no problem with present-day technology."
Answer : True enough. It just won't work. The problem is that liquid iron trickling though hot coals and exposed tocarbon monoxide at least on parts of its way down will incorporate so much carbon (and whatever else might bearound) that you don't get pure liquid iron all the way down but dirty cast-iron! You simply cannot make clean liquid
iron in a carbon smelter.
Question: "Excuse me, but why do I get clean liquid copper then?"Answer: You don't, actually. It just so happens that copper does not incorporate a lot of carbon (look at its phase
diagram!). It can and will dissolve a lot of other stuff that happens to be around, however - iron, for example! That is aproblem! But when you melt the dirty copper again, getting it ready for alloying and casting, you automatically purify
it to some extent.
Question: "Why do we get mostly wrought iron, i.e. rather carbon-free iron in solid iron smelting as I read almost
everywhere? After all, the solid particles of rather hot iron could also incorporate some carbon on their way down,even if they hang on to liquid slag! "Answer: First, in contrast to public opinion and quite involved theory, typical iron smelting throughout the ages did
not produce just wrought iron. A bloom with a wild mix of low-carbon wrought iron and all kinds of carbon steel isproduced most of the time if you do not run your smelter in an optimized way. However, the iron produced by
reduction below about 700 oC (970 oF), has no choice but to be rather pure. If you manage to keep it that way on its
way down the smelter, you do end up with wrought iron. But that does not happen "automatically"; you need toknow how to achieve that. More details can be found here.
Question: "Why do archeometallurgists, including the ones whose papers I particularly enjoy reading, often mention
iron that has been "carburized" if they discuss steel artifacts? Don't they know that you cannot increase the volume
carbon concentration of a solid piece of iron by any reasonable treatment? In other words there is no such thing as"carburization"! Then they talk a lot about "primitive small smelters" in the iron age. Don't they know that smelter
technology at the beginning of the iron age around 1200 BC was already highly developed?"
Answer: You are right and I don't know the answers. There is indeed a lot of confusion in the general literature about
how to make wrought iron, steel and cast iron. As far as the intricacies of smelter technology and the iron-carbon
system are concerned - those were and are mysteries to almost all. That's why I'm writing this Hyperscript, after all.
Since all and sundry were inclined to believe that bloomeries could only produce wrought iron, you had to assume
that some "carburization" was done later if you actually dug up steel.
"Primitive smelters" may simply refer to dug-up facts. Smelters might well have been more primitive for iron thanthey had been for copper. After the fall of the (Western) Roman empire, bath-room facilities were rather moreprimitive for about 1500 years than Roman standards, for example, and the same might have happened to metal
technology in some places for a while. However, the technology for making the Colossus of Rhodes around 300 BCfrom bronze and iron / steel was certainly not primitive, to give a counter example.
More to that in the next sub-chapter. First I will look a little more closely into what is going on inside an iron smelter

Inside an Iron Smelter
Let's assume that carbon monoxide (CO) is around and that it is hot enough for things to happen. Now let's give that acloser look. One of the things that could happen is that you killed yourself because carbon monoxide is rather
poisonous, and some of it always comes out at the upper end of your smelter.
Carbon monoxide reduces iron ores in stages. Before that happens, some changes in the ore may take place byroasting. It goes like that:

Roasting
Goethite /Limonite
Siderite

2 FeO(OH)⇒

Fe2O3 +
H2O

FeCO3

⇒

FeO + CO 2

Smelting
Magnetite

Fe3O4 + CO⇒

3 FeO + CO2

Hematite

Fe2O3 + CO⇒

2 FeO + CO2

WüstiteFeO + CO⇒Fe + CO2Iron, Steel and Swords script - Page 332

No, I didn't break my promise of "no equations". Those are just chemical reaction "equations". We don't count thoseamong serious mathematical equations. They are just abbreviations for long names.
What we see is that the various iron oxides are turned into iron in several steps, always producing FeO or wüstite
first. The first two reactions (roasting) you can do separately from smelting, you sort of condition your ore.
Reduction of the wüstite is the final reaction in the smelter, it produces the elemental iron.
Far more reactions occur then the ones listed above, including, for example, direct reduction with carbon and notcarbon monoxide.
We must also consider that some of the carbon dioxide (CO2) produced by reducing the ore is turned into carbon
monoxide (C + CO2 + energy ⇒ 2CO) as long as it is hot enough, helping the reduction process. That is good. On
the other hand, some of the carbon monoxide produced will turn to carbon dioxide and carbon in the form of soot;not so good.
Where the main processes happen inside the smelter can be seen in this link
How fast one of these reaction proceeds depends on many things. Essential is always the available surface area ofthe ore because whatever happens takes place at the surface. A bunch of small ore particles react much faster thanjust one lump of the same weight. So crush your ore - but don't make the pieces too small, this would restrict theflow of gases too much. A porous ore particle full of microcracks has a larger surface than a compact one of thesame size. Crumbly limonite thus might be better than solid magnetite.
Now let's look at some not-so-good things that will also happen.
First, cementite (Fe3C) is formed; either from an oxide or from the freshly generated iron. Cementite formation
reduces efficiency because it takes out some of the iron supplied by the ore.

3 FeO + 2C⇒

Fe3C + CO

3 Fe + 2 CO⇒

Fe3C + CO2

We are not yet done. Besides carbon and iron ore, we have all kinds of "dirt" inside the smelter, not to mention theflux we added, and the walls of the smelter that will also participate in all kinds of reactions. We might, for example"smelt" a few more elements by accident, for example phosphorous (P), nickel (Ni) and copper (Cu) if somecompounds happen to be around:

P 2O5 + 5 CO⇒

2 P + 5 CO2

NiO + CO⇒Ni + CO2

Cu2 O + CO⇒

2 Cu + CO2......

.....

.....

All of the above is possible and will happen in an
antique bloomery if the stuff is around. The elements
produced can end up in the iron
SiO2 + 2 CO⇒

Si + 2 CO2

MnO2 + 2 CO⇒

Mn + 2 CO2

…..

.....

.....

Possible in principle but not happening in an antique
bloomery. Manganese oxide in your ore thus will not
put beneficial manganese (Mn) into your iron

Iron, Steel and Swords script - Page 333

So some of the constituents of the unavoidable "dirt" in your smelter may or may not end up in the iron you
produce. If they do end up in the iron, they do influence its properties. In a major way like phosphorous, where small
quantities below 1 % make a big difference, or just a little bit like nickel (Ni), where 1 % or so is hardly felt. But
sorry - all those manganese-oxide rich iron ores do not help directly to make better iron because some beneficial
manganese makes it into your product as is often assumed.
However, stuff that does not imbue the iron with manganese, silicon, or other "good" elements may nevertheless bequite important for other reasons:
1. It may influence or even dominate slag formation like silicon dioxide (SiO 2) or change the properties of theslag. The slag, for example, might become fluid at a somewhat lower temperature because of some "dirt" andthat is rather good.
2. It influences the ability of the iron to pick up carbon on its way down to the bloom. Manganese oxide (MnO)
is reported to do this, for example; although I'm not sure I understand how that is supposed to happen.
The message is loud and clear:

The kind and "quality" of your ore,gangue and flux matters very much!

Making good iron is easier if you can command clean oxides or carbonates. If you are stuck with "bog iron" ,you still can make good iron but you must adjust and optimize your process chain - from the pre-treatment of youringredients, via the smelting process, to special processing tricks for the product. Your way of making a steel sword"from scratch" could then be quite different from that of the more lucky people with clean ore.
I'm not done yet. We still need to produce slag. No slag - no efficient iron smelting! If we use the ore as flux in a kind ofself-fluxing process, we are looking at (simplified) reactions like:SiO2 (quartz) + 2
FeO
solids⇒

CaCO3 (limestone)
SiO2 + CaO(quicklime)
solids⇒……….

⇒Fe2SiO4
Fayalite, main
component of slag,
viscous liquid
CaO + CO2
CaSiO3slag component……….

The first reaction takes place between silicates always containing SiO2 and iron oxide (= iron ore). It produces aniron-silicate , Fe2SiO4, called fayalite, a major component of pretty much all antique slags. SiO2 is pure quartz or"silica", rather common by itself, but most silicates and thus most "rocks" will also do.
The second reaction uses calcium oxide (CaO) or quicklime, something you don't find but must make by burning
limestone right in your smelter. While quicklime making was already known to stone-age people, its use for ironsmelting had to await the advent of the blast furnace around 1400 / 1500 AD where limestone is used for flux.
In any case, these reactions (plus plenty of others) occurred between crystalline solids because your primary flux
materials, like your ores, would never liquefy in antique (or modern) smelters. Only some reaction products areglassy or amorphous materials that do not melt but turn from solid to viscous to liquid as the temperature goes up,
sort of like honey. Around 1200 oC (2192 oF) your slag is liquid enough to "run".
I'm going to stop here. I'm sure you got the point

What happens inside a smelter isvery complex indeed!

Iron, Steel and Swords script - Page 334

Today we might be able to model the whole thing by using appropriate and very involved theory. With very big
computers one might get useful results. That is pretty much the only way to "look" inside a smelter. Any direct wayof "looking", or approaching the task experimentally, is well-nigh impossible. You simply cannot watch a piece ofore making its way down the smelter and record in great detail what is going on.
What we can do, however, is to make special experiments in the laboratory. Expose a small piece of pure ironoxide to carbon monoxide in a retort at precisely known and controlled temperatures and you can "see" andmeasure what is going on. That will give you data like the ones displayed here.
All that the early iron engineers could do was to go by trial and error. What they actually did do, we don't know.
First, only a very small part of all the iron things made have survived and were found. Second, the results fromunsuccessful smelting runs are almost never found because you can't find iron if none was produced. In a similarvein, it is not likely that we find many objects that were made from "bad" iron, e.g. copper-rich iron, because at besta few small objects like rings were ever made.
In 2000 years from now archeologists are going to find zillions of silicon devices but at best a few that were madefrom germanium. The very first electronic devices, however, have been made from germanium only. The experiments
concerning silicon and the many "bad" silicon devices actually made during the germanium time (and then thrownout), will not show up in the future archeological records at all.

Iron, Steel and Swords script - Page 335

10.2.3 Smelting Wrought Iron, Steel and Cast Iron
Steel by Carburization ?
Let's start by a quick look at a controversial issue: Can one make steel from wrought iron by "carburization"? The
answer is certainly "yes" - as long as the term isn't specified. It is certainly possible to get carbon from the outside into
originally clean iron ("wrought iron") if you have high temperatures at your disposition - and all the time in the world.
Steel has indeed been made in this way in the 18th century (by a process called "cementation"); I will get to that.
However, the issue here is not the 18th century but the first millennium BC and the many publications stating thatsome old artifacts consist of "carburized iron", vulgo steel. The directly or indirectly implied message is that someancient smith started with wrought iron and managed somehow to get substantial amounts of carbon into an object
like a knife blade by carburization while he is forging it.
Here are a few examples:"Ideally the smelter produces steel. If not, the iron will be carburized in the forge".
"The practice of steeling (i.e. carburizing) such items as bracelets is curious since there is no functional
advantage to be gained....""One of the knifes was not carburized, one was mildly carburized, the other two were extensively carburized".
The list could go on for quite a while. I do not give references because what we have is a general pattern, andbecause authors I regard very highly have fallen into the fallacy of implying that ancient smiths somehow"carburized" wrought iron in order to get steel. The truth, however is:

You cannot "carburize" a volume of ironin your forging hearth.

Rehder , in his invaluable book, makes that quite clear. He has two independent arguments for his claim:
1. The first argument is based on the necessity that the source of carbon can only be the carbon monoxide
produced by burning charcoals in the forging hearth. Based on simple calculations he argues that one cannot nothave enough of that gas in all the places were it would be needed. One rather has carbon dioxide and oxygen,and the usual effect of heating a piece of iron in a forge-fire is actually de-carburization and iron oxide ("hammer
scale") formation.
2. The second argument considers the time needed for getting carbon deep into iron. Rehder maintains that evenwith enough carbon monoxide, "carburization" would take far too long to be of practical value.
.
The eminent archeometallurgist Donald B. Wagner, undisputed expert for the Chinese metal history, begs todisagree1). He bases his criticism on Rehder's CO concentration calculations, reasoning that enough of the stuff
could be around in a forging hearth. He also refers to writings from the 18th century and to some more recent
experiments were "carburization" during forging was claimed or demonstrated, respectively. What Wagner proves
beyond doubt is that one can carburize wrought iron, indeed - as long as only thin layers or tips of needles are
considered.
The issue is rather easy to resolve. How much carbon is available for moving into the iron from the outside does dependon the source of carbon, of course. Carbon monoxide, splitting into carbon and oxygen on the surface of hot iron, is far
more efficient in providing carbon atoms at the iron surface than solid charcoals. A gas can envelop the iron at any
moment, whereas a solid piece of charcoal only touches the iron at few spots at best (see all the way below), and thecarbon - iron contacts are even destroyed as soon as a carbon atom breaks off and disappears into the iron.
This is clear from the picture below. It is our old copper picture, of course, just slightly changed for smelting iron now. It
has one added feature: carburization by CO. It still does not show slag formation and other "details".
So the source of carbon for "carburization" is important, indeed - but not crucial for the topic.

Iron, Steel and Swords script - Page 336

Inside an iron smelter. Extremely simplified

The real problem comes from diffusion, from the way carbon atoms move into the inside of iron. Once a carbon atom
has made it below the surface layer of the iron crystal, it moves around randomly, as illustrated here. Looking at
numbers one learns, for example, that you need to keep your piece of iron at 1000 oC (1832 oF) for about 3 hours if
the carbon should penetrate to a depth of about 3 mm. That would just about "carburize" a knife blade. Not uniformly
though, mind you. The carbon concentration near to the iron surface would be much higher than in the middle of theblade.
So you can get carbon inside iron. In principle as deep as you like, but at "normal" temperatures, this takes far too
long to be practical. If you want to go for 6 mm in the example above, it will take 9 hours; 9 mm take 27 hours andso on. If you increase the temperature a lot (not all that easy to do in an ancient forge), the time required does comedown but grains will grow larger and so on, counteracting your efforts to "harden" the iron with carbon.
What you can do and what has been done, is to "case-harden " your workpiece. You supply a thin layer of carbonrich iron or steel around your wrought iron inside by keeping it in your forge fire at the right place (where the carbon
monoxide is produced) for a while. If you quench and possibly even temper your piece after that, the outside or"case" could well be very hard steel.
However! While this is not too difficult to achieve in a modern hearth with a constant air supply, ancient hearths
were "blown" with an intermittent stream of air, and this caused the reducing part of the fire to "breath" - moving
back and forth. The gradual disappearance of the coals also moves the proper place around, and it is not all thateasy to move your workpiece accordingly. If your workpiece is large like a sword blade, you can only keep a smallpart of it in the right place anyway.
And don't forget: whenever your iron is not in the reducing part of your fire, de-carburization takes place! First, youoxidize the iron, consuming the surface-near and "carburized" parts, and second, the carbon diffuses out of the ironjust as readily as into the iron. If your pieces carburizes or de-carburizes simply depends on the balance of
depositing carbon atoms on the surface and sweeping them off. Only in a reducing CO-rich atmosphere deposition
wins.
All in all, carburization of a thin layer of iron in an ancient forge fire is possible - but not easy. Carburizing a solid
large piece of iron this way is impossible, though.
The long and short of this is simple:

Ancient fully "carburized" iron (= steel)
was never made in a forge fire
but right in the smelter!

Smelting Wrought Iron
Iron smelting throughout the millennia supposedly produced wrought iron with a very small carbon concentration. Maybe
that's true. At this stage I'm not saying it is, and I'm not saying it is not. What I am saying first is: Why bother? Wrought
iron's properties as a metal are supposed to be inferior or at best equal to those of bronze. We know that this is true forthe hardness of the material from comparing it with bronze.
However, wrought iron (and mild steel) offers large advantages on other counts:
If you have the know-how, it is far easier to make than bronze. It doesn't need an extensive infrastructure for
procuring rare ores or ingredients like tin from far away. In contrast, if you have some wood at your disposal andaccess to some iron ore deposits in mountains or to a working or ancient bog in the low lands where you find bog
iron, you can make it all yourself.
Iron is therefore much cheaper than bronze.
Iron, Steel and Swords script - Page 337

Iron is easy to work with by forging. You must have the know-how , of course, but banging a lump of wrought iron
into a knife-blade shape is altogether far easier then making a mould, making a crucible, melting some bronze,
casting the bronze, finishing the cast.
You can hammer or fire weld small pieces to get a large piece; the link gives an example. That is not possible
with bronze and most other metals
Your wrought iron tools can be repaired. If your knife breaks, fire-weld it together again. You can't do that with abronze blade.
If you can "do" wrought iron, you have the door wide open for moving up to making and working steel , includingthe "in-between" like case hardening your wrought iron knife blade.
Now we know better. While wrought iron is not harder than bronze, it does offer lots of advantages. As soon as
people learned the many tricks needed to make and work iron, there was no good reason anymore to stick tobronze except for some special cases or because you are conservative. Getting into the new technology was
torturous and painful, with many disappointments and unexplained mishaps. One only embarks on such anenterprise if there is no choice.
People only switch to unaccustomed food shortly before starving. When was the last time that you ate insects,
worms, grubs, or just cats and dogs (or pigs, cheese, ...)? Potatoes weren't originally welcome in Europe, many
Asian people wouldn't know what to do with wheat, and I still don't know why my wife thinks that corn is food forpeople before it has been processed by a pig.
It is thus no accident that iron came into its own at the collapse of the Bronze Age. As we have seen in thepreceding sub-chapters, the occasional very early iron came in all kinds of variants - copper-rich, "carburized" - withno recognizable relation between the composition and the intended use, see above. Some bracelets were "steeled"while some knifes were not. It all points to those ancient smiths simply not having a clear idea about the various
qualities of iron / steel. They just did their best with the haphazard pieces they had and in all likelihood were quite
happy if they could make anything worthwhile for keeps. We can be rather sure that most products of early irontechnology didn't "work" and were simply thrown out.
Eventually, however, iron could be made reproducibly and reliably, and the secondary technologies like dealing withthe red-hot bloom, making half-way clean iron bars on a hearth by forging, plus making various shapes from thesebars by forging and fire-welding, became known and were mastered.
Above I have exorcised the "carburization demon". Now I need to remove the "wrought iron was first" demon. Did you
realize that all the carburization talk only makes sense if one assumes that early iron workers could only make wrought
iron? Only then do you need to "carburize" the carbon-free stuff if you want steel.
That's indeed what is mostly assumed. And that assumption was backed by theory as far as it goes. Nevertheless - it iswrong!
Copper smelting technology at 1200 BC was developed to a point where it would have been no problem at all to
produce anything ironwise: wrought iron, steels with little or a lot of carbon, and cast iron. All you needed to do was
to use the existing technology with iron ore instead of copper ore and a somewhat increased charcoal to ore ratio. A
few minor adjustments here and there and off you go, making cast iron, for example.
True, we have not found cast iron artifacts in the Mediterranean between 1200 BC and 1000 AD. Does that meanthat nobody could make cast iron? No! It just as well could mean that nobody bothered to make it since it wasconsidered useless. But what about accidentially made cast iron in antiquity? Have we found any? Not really. But
then nobody looked for it and if found, it wasn't recognized.
Not everything one can make is actually made. Nobody in the the South American empires (Maya, Aztec, Incasand so on) bothered to make wheels for carts and so on, even so they knew how to do this (they made children toys
with wheels). Wheels, considered to be one of the greater inventions of mankind, are rather useless in ancientSouth-American cultures since there were no horses, oxen or any other animals that could pull your cart around,
not to mention the rather steep roads in the mountainous regions or narrow and muddy paths in the jungle.
It is similar for cast iron and high-carbon steel. As all modern smelting experiments prove, you had no problem
producing highly "carburized" iron in your smelter. You just didn't want to do that most of the time. Steel is so much
more difficult to work with and rusts like crazy in comparison to wrought iron. Its larger hardness isn't so importantfor most of your everyday iron objects either. It might even be a nuisance. For example, carpenters still use nails
that are not made from steel but from rather soft iron for obvious reasons. And cast iron is extremely brittle and thus
useless on first sight. On second sight one might do something with it, as the Chinese proved.
We need to realize that the main product of the town smith for the last 3000 years weren't swords, mail and armor.
That was made by a few specialized guys. The vast majority of smiths made every-day wrought iron or mild steel
things for the always overbearing reason: It is good enough for the job and much cheaper. Your car body isn't madefrom stainless steel for exactly the same reason.
In other words: After the iron age proper had started and enough experience with the new metal was acquired, thesmelters produced the quality of iron that the customers wanted. And that was mostly wrought iron or mild steel,occasionally steel, and never cast iron. It is thus small wonder that smelting technologies were optimized - by trial anderror - towards making wrought iron and mild steel.
The question now is:Iron, Steel and Swords script - Page 338

How do I smelt wrought iron only?

The answer is: I don't know. It is easily possible in theory but seems to happen rarely in all those experiments
people make! The best one can do is:
Take advantage of the iron-carbon phase diagram. And the peculiarities of the diffusion of carbon in iron. Also don't
forget to optimize the movement of the burden down you smelter in relation to the movement of liquids like slag. This
involves optimizing the smelter geometry and the kind and quantity of flux you add. Not to forget either: having theright ore lump size distribution is essential. And it goes without saying that how much air you blow in at what kind of
velocity is crucial.
In other words: those old smelting masters needed an advanced degree in Materials Science and Engineering. Or
did they?
When my wife makes her famous "Hefekranz" (braided yeast dough thing, sort of like halla, just better), she optimizes
the relation of yeast to flour, the time at the right temperature for allowing the yeast to eat the flour and multiply, themixing of the ingredients, the nucleation and growth of CO 2 -filled bubbles (this takes optimizing the reaction
temperature and time to allow proper diffusion and Oswald ripening) and the addition of secret ingredients like sugar andGod knows what. I gather that the right kind of flour (particle size?) is very important, and that various temperatures playa significant role. It is an incredibly complicated process and I have never managed to calculate what's going on.
As far as my wife is concerned, she bakes a cake, following the working recipe of my mother to a dot. Nothing to it.
Works all the time.

It worked (Hefekranz)

Long ago I suggested to try a few changes to the recipe. Use different flour for a chance - maybe the product getsbetter? My wife just gave me that look. Of course she was right. The probability that an already very good product gets
worse if you make changes in the recipe are far larger than that it gets better.
Good cooking recipes were obtained by a long series of trial and error, and it doesn't matter if you cook food or ironore. Eventually there are working recipes. They are somewhat different from region to region but they work for the
local customers. Maybe the Italian food is better than the German food; in Germany we use German recipes
anyway. But even in Germany, recipes for "hefekranz" vary quite a bit from here to there. So all the good wives,
about to make a hefekranz for their deserving husbands, use different recipes - but only up to a point. All hefekranz
recipes must have a lot in common after all, if the final product is to be contained in the bandwidth of what
constitutes a hefekranz. Leave that common ground and you do not get a hefekranz but a Gugelhupf, for example.
Also very good to eat but just not a hefekranz.
Maybe the Roman "Ferrum Noricum" (made from siderite) is better than the North German iron (made from bog iron)but smelting recipes in North Germany were not changed. Using the Roman technique would not have worked in
North Germany because the guys there just didn't have the exact same ingredients.
We can be rather sure that every region had their wrought iron smelting recipe that had evolved by trial and error togive satisfactory results for whatever local conditions prevailed. Satisfactory results, not the very best result, mind
you. Evolution only goes that far and always leaves a bit of room for future improvements. Just look in the mirror torecognize that. Evolution, after all, has made you.

Iron, Steel and Swords script - Page 339

What is the common ground in making wrought iron that all smelting recipes must recognize? Looking at that from theproduct, your recipe must assure that
1. Pure iron is produced during the primary reduction processes.
2. This pure iron should not get carburized (or messed up in other ways) on its way down from the reduction zone tothe bloom.
The first condition is easily turned into a recipe: Keep the temperature low (around 800oC (1472 oF). The you
produce your iron only as ferrite that cannot dissolve carbon. If there is some carbon for some reason, it will
precipitate as cementite (Fe3C).
Since reduction of iron ore with carbon monoxide (CO) starts well below this temperature, there is no big problem
there (except, of course, setting and keeping the temperature). In the freshly reduced ferrite there is no carbon. If it
does not get hotter and turns to austenite there never will be.
The problem starts with getting your carbon-free ferrite into some protected position below the tuyere. Typically you
need liquid slag for this. But there is no liquid slag at 800 oC. Nothing helps, you must have temperatures well above
1100 oC (1472 oF) in the hot part of your smelter to liquefy slag. You must get your carbon-free iron somehow
through that hot zone without carburizing and oxidizing it too much.
If you want to make steel or cast iron, the opposite is true.
This is where the art of smelting wrought iron starts. It turns into a high art as soon as you don't just want to produce
wrought iron but any kind of iron / steel, e.g. steel with 0.5 % carbon with some predictability and reproducibility. If you
can do that also with high efficiency, meaning with as little fuel and ore as possible, you are worth your weight in gold, I
guess.
Let's review what we have in our bag of tricks for moving our carbon-free iron particle down through the hot CO producing
and oxidizing zones and to keep them carbon-free if we want wrought iron. I include tricks that might come to mind but
don't work:
1. Envelope your pure iron in liquid slag at temperatures below 720 oC (1330 oF).
Nice try but can't be done. There is no liquid slag at temperatures that low. Never ever.
2. Allow some carburization in the reduction zone and remove the carbon later again.
Carburization, as we learned above, proceeds by diffusion and thus may only affect the outside of our ferrite
particles as long as they are not too small. "Burn" off that carburized layer in the oxidation zone by oxidizing andwhat is left is carbon-poor. That requires that your particles are not to small so only an outer layer becomescarburized, but not so large that they are not fully reduced.
3. Just run the process messily (and inefficiently).
Keep temperatures as low as possible and inhomogeneous. Make only the parts above the tuyere as hot as needsbe, keeping the opposite parts cooler. The CO produced in the hotter part will spread out as it moves up, reducing
ore also in regions closer to the other side. Same thing for the slag. It is liquefied in the hotter parts above thetuyere but in percolating down will spread to the outer parts, sweeping down whatever it finds. Iron particles moving
down on the opposite side thus will not spend all that much time in the austenite phase, where the can absorb
carbon, and thus stay pure.
4. Don't mix ore and charcoal, produce layers.
When a charcoal rich layer burns, producing lots of hot CO, you reduce the ore above it. When the ore layer with
the iron comes lower, temperature will go down because the charcoal content is low, and you get your iron down
without carburizing it too much.
5. Oxidize your (more or less carburized) iron somewhat or even a lot in the oxidation zone. As long as enough ironis there to make it stick to the bloom developing in the "cold" region below the tuyere, you need not worry as longas you are producing carbon monoxide around the bloom, too.
In other words: you now reduce very finely dispersed iron oxide right on the bloom. You might even reduce the ironoxides in slag that lingers there long enough. Since this happens in close contact with some "seed" bloom, you are
now growing a wrought iron bloom.
6. Keep your iron particles large and compact (in contrast to spongy), or more generally, have a small surface tovolume ratio. Carbon must diffuse in from the surface and you get lower over-all carbon concentrations in large
particles compared to smaller ones at the same conditions. How you can achieve that I don't know. Use the rightores, in not too small lumps? Have the iron particles attached to yet unreacted ore / gangue (protecting theirsurface)?
7. Keep the carbon monoxide busy to reduce FeO wüstite so it does not diffuse into the iron already produced out ofsheer boredom because there is nothing else to do. In other words: move your burden down fast enough so when it
hits the hot zone some ore is still around. Expressed in scientific words and with equations, that is the official
reason for the (wrong but time-honored) theorem that bloomeries can only produce wrought iron. It will work, though.
Just not all the time and in all circumstances.
8. Your idea.

Iron, Steel and Swords script - Page 340

10. Measures that seem to work and that W. H. Lee Sauder and Henry G.
Williams III stumbled across by doing lots of bloomery experiments under the
influence of beer. My interpretation of what they are doing - and I might be wrong is: Run your smelter hot and with as much ore as possible. Reduce all iron oxide
before it hits the oxidation zone. The iron will re-oxidize but the oxide shell forming
around an iron particle will form slag with the other now very hot stuff around,envelop the remaining iron in a liquid slag shell, and trickle down fast to join the
bloom below.

Advanced
Link
Sauder /Williamsmelting

I'm not really certain about all the stuff above. Points 2 - 6 might contribute to making wrought iron (or any iron / steel) tosome extent but I don't know. Sauder and Williams go far in finding solutions; time will tell how far exactly theirapproach (and my interpretation) will get us.
Personally, I still wonder if one can produce wrought iron, meaning iron with hardly any carbon inside, in a smelter at all.
A bit further down I will make it clear that making solid iron with a lot of carbon inside is also quite hard.
From "theory" one should expect that a bloomery produces iron with some carbon - not a lot but more than almost
nothing!
I'm certain, however, about one thing

Diffusion

Temperature is decisive

Diffusionin IronAt temperatures above A1 the iron assumes the austenite phase. Carbon is soluble in austenite and can get "in" bydiffusion. The distance carbon atoms can cover at a given temperature during a given time I called "diffusion length",
invoking Einstein. This diffusion length increases exponentially (really fast) with the temperature but only with thesquare root of the time (slowly). If you increase the (absolute) temperature just 10 %, for example from 1300 K(1027 oC;1880 oF) to 1430 K (1157 oC; 2114 oF), the diffusion length increases by 65 %, while even doubling thetime (100 % increase) produces only about a 40 % increase.
Let's simplify that in a strong statement:

Wrought iron production depends on
diffusion limitation

In other words: you can't keep your iron clean by limiting the supply of carbon. There is always enough around tomess up your wrought iron. You must limit the diffusion. You must either make diffusion in the iron slow or you must
make it hard for the carbon to get into the iron by coating it with a diffusion barrier. Low temperatures in the
reduction zone, by necessity above A1 but as low as possible, were thought to provide the key to that. But if you
keep the temperatures too low, not much will happen.
A completely different approach - the Sauder / Williams way - is to use high temperatures. It looks like this enables
efficient slag formation and then efficient protection of the iron particles.
That is quite similar to what we do in microelectronics. We must keep bad atoms like copper or iron out of thesilicon at all costs. Low temperatures would be fine but then you can't process your silicon either. So use a diffusion
barrier, a thin coating of something inside which the bad atoms diffuse so slowly that they will not make it to thesilicon or are "eaten up" because they react with the stuff
All things considered, I'm not too sure about what exactly you need to do to produce only wrought iron. I'm not sureeither if that was ever done. The complexity of the problem will become a bit clearer when we now look at making steel
and cast iron.
Smelting Cast Iron
Now let's go to the other extreme. Let's put lots of carbon into the iron, making it cast iron.
In principle things are clear. Just do the opposite of what is described above. Allow the iron particles to get really hot in
the CO rich part of the smelter. Then carbon can penetrate deeply and in quantity. To get a feeling of what the task
implies, let's look a bit more closely at how much carbon you actually need, and where it must come from.

Iron, Steel and Swords script - Page 341

The answer to the last question is simplicity itself. The only source of carbon in your smelter is the charcoal. It turns
into the carbon monoxide (CO) that acts as carbon source, indeed, but you first need the charcoal. Charcoal has adensity of 180 kg/m 3 - 280 kg/m3; it is very "light". Iron, on the other hand, weighs in around 7.800 kg/m3 - it iscalled a heavy metal for good reasons. Considering that you don't feed only solid charcoal to your smelter but acharcoal - air mixture, which charcoal accounting for about 50 % of the volume, the available carbon comes with aneffective density of roughly 100 kg/m3.
You can imagine the production of carburized iron by taking a quantity of pure iron and then pile as much charcoal
on top as is needed for getting the right carburization level. Dissolve that pile in the iron, and there you are. Here is
the picture:

How much charcoal you need to dissolve in theiron shown to get the percentage indicated

It sure looks like you need quite a bit. In smelter reality, however, you need far more - multiply by two or three,would be my guess. Why is that? Because you can't put all the carbon from the charcoal into you iron! You need toburn quite a lot to produce the energy needed. And burning turns the carbon of the charcoals into carbon dioxide(CO2). In the reducing layer this CO2 is reacted to the carbon monoxide (CO) that reduces the ore. That producescarbon dioxide once more. Slag production might also eat up some carbon. Whatever happens, a lot of carbon
dioxide (and possibly some monoxide) will come out on top of your smelter, and the carbon in these gases cannot
carburize your iron.
If we now want to make cast iron with 4 wt% carbon in the iron, we encounter a new problem:

Cast iron production iscarbon supply limited!

It is not diffusion limited as the production of wrought iron just discussed above. Why isn't it diffusion limited, too?
Because you now run your smelter at very high temperatures. The copper people knew how to do this; it is pretty
obvious anyway: Increase the ratio of charcoal to ore and blow more air trough the tuyere. In case of doubt use twotuyeres. What you need to achieve is that the iron formed way up in the stack incorporates enough carbon in theCO-rich reduction zone to lower its melting point to a value were it becomes liquid before it hits the oxidation zone.
Then it can trickle down as cast iron and collect as a liquid in the bottom of the smelter, protected by the slag layerthat swims on top of it.
As already discussed above, your only chance to get enough carbon into the iron is to use carbon monoxide as sourceof carbon. From the picture above it becomes clear that you need to turn a lot of charcoal carbon into carbon monoxide
to have enough. And don't forget, you need carbon monoxide also to reduce the iron ore. For doing that you need far
more carbon dioxide and energy than in the case of making wrought iron. That's why you need to burn far morecharcoal.
Hence the simple recipe for making cast iron once more:
Use more charcoal relative to the ore content, i.e. increase the charcoal to ore ratio.
Make it as hot as you can inside your smelter. You need the high temperatures for more efficient CO production
and for fast diffusion.

Iron, Steel and Swords script - Page 342

Isn't that interesting? Putting a lot of carbon into iron is just about as difficult as keeping it out! Maybe making
wrought iron isn't that tricky, after all? If you don't know a thing about iron and carbon and just run your smelter on
the "lean" side, you will get some carbon into the iron but maybe not all that much? Maybe, but Lee Sauder,based on experiments, disagrees. He rather goes for running your smelter hot and being smart about slag
production. Who knows.
What we do know is that the early iron smelters around 1200 BC and some time after that produced all kinds of iron andsteel. Wrought iron, mild steel, hard steel, cast iron, phosphorous iron, and so on. The bloom from just one run might
have contained a whole mix, and the results from one run to the next must have varied. That is what modern smelters
tend to findForging the stuff must have been frustrating. Sometimes it was easy, sometimes it was difficult and sometimes it
couldn't be done at all. That explains up to a point why sometimes jewelry was made from hard steel and a knife blade
from wrought iron, and why there seems to be no system in the amount of "carburization" if we look at early ironproducts. It is one thing to discover the basic technique of smelting iron, and quite another thing to make it areproducible process that produced high-grade blooms with consistent qualities and carbon content. It also takes sometime to establish (and pass on) the art of forging with all its many tricks.
It is usually assumed that the "West", including the Romans, was not able to produce cas iron in antiquity - incontrast to the "East," i.e. the Chinese. That is not the case. It looks rather that people didn't want to make castiron. Old cast iron has meanwhile been found in Europe, and there is probably more. One problem is that you only
find cast iron or residues of cast iron smelting you look for it (and know how to interpret what you find. I give you two
references for that 2), 3) but for the time being leave it at that and now turn to the art of smelting steel.
Smelting Steel
Making iron with carbon contents between 0.2 % and 0.8 %, say, is now simplicity in itself (haha): Don't do anything
special. Not too cool, not too hot and so on, and you will end up with a bloom that contains some average carbon
content around, say, 0.4 %. If you look closely you find that the carbon concentration varies from one spot to the next. It
is easy to see why. Every iron particle, deposited on the existing bloom by some slag droplet, has its own history andacquired more or less carbon. If the lumps of ore fed into the smelter had a large distribution of sizes, differences will belarge, if they all had about the same size, their carbon contents will be more similar.
For some hands-on experiecne on this read Adrian Wrona's "hands-on" account. Here it is.
There might also be differences in the average carbon contents from the bottom part of the bloom to the top part
because conditions changed. When you first feed ore into the smelter, you cool it to some extent and it may takesome time before a stationary state is reached. When you stop operations, your smelter is still hot and things still
happen for a while.
With increasing experience you learn how to make a bloom with some halfway predictable carbon content. Surprises
are likely to to happen whenever one of your parameters changes a bit without you noticing. The quality of the charcoal
from that new supplier is a bit different, your new tuyere has a slightly smaller inner diameter, your bellows developed atiny leak, the gangue coming with the ore changed a bit in its compositions, you had too much beer while controlling
things, ....
Enough "theory". Now let's go out and smelt.

I have (of course) never heeded my own advice. But others have, in particular Darrell Markewitz , who works in the Lee
Sauder tradition. His account in what it takes to do proper smelting is quite "hands-on" and fascinating. Here is his
report.

1)

Donald B. Wagner: Ancient Carburisation of Iron to Steel: a Comment", Archeomet., 4.1 (1990) p. 111 - 117

2)

P. Crew, M. Charlton, P. Dillmann, P. Fluzin, C. Salter and E. Truffaut: "Cast iron from a bloomery furnace", In The
Archaeometallurgy of Iron, Eds J Hosek, H Cleere & L Mihok, 2011, 239-262

3)

Hubet Presslinger: "Metallographische Beurteilung... (he found cast iron in the Noricum)", Schild von Steier, 20 (2007) pp.
313-315

Iron, Steel and Swords script - Page 343

10.2.4 Bloomeries
Real Smelting
So you smelted some iron. Some time between 1000 BC and 1000 AD or even later. It doesn't matter much as far as
the basics are concerned. You used a "bloomery " type of furnace, essentially a stone lined hole in the ground plus acylindrical tube made from e.g. clay on top; see all the pictures below and elsewhere. A bellows is attached via atuyere. Your bloomery is not much different from the shaft furnaces used for making copper.
You did the best you could, trying to follow the working recipe as closely as possible. You and your crew worked formany hours. Some roasted the ore and smashed it into small pieces of suitable size; others built the smelter and thehearth of the forge. During smelting time it's working the bellows, feeding the smelter, fetching the beer, and watchingclosely if everything goes well. You may tap the slag once in a while through a tap hole or you just let it collect in thebottom pit.
Now it is time to stop the smelting. How do you do this? You tell the guy at thebellows to stop pumping? Then your smelter stack will be full of burden that got
stuck when the fire goes out and everything cools down. That will be no problem if
you tear down the whole thing to get at the bloom while it is still hot. It's justwasteful.
So you stop feeding the smelter but keep blowing air until everything is burned off.
Then you use up all material. It's just that the smelting process sort of fizzles out
uncontrolled during this turning-down process and you don't know what happens toyour bloom. But you might be able to get your bloom out through the top or an
opening at the bottom without being forced to tear down your smelter completely.

Illustr.
ModuleDoing it

Here are some pictures of a smelting experiment. It was re-enacted to investigate the old techniques and also to
see what one would dig up years later:

Small Bloomery starting up, dismantled, and bloom
Source: Thomas Birch, Robert Scholger, Georg Walach, Frank Stremke,
Brigitte Cech: "Finding the invisible smelt: using experimentalarchaeology to critically evaluate fieldwork methods applied to bloomery
iron production remains", Archaeol Anthropol Sci; Published online 16.
Mai 2013.
With friendly permission

This was a smelting experiment done by archaeometallurgists. That's why we havedata and numbers:
The ore was limonite, roasted and then crushed and sorted.
15 kg charcoal for preheating.
Constant airflow until the end stages of the smelt, when it was increased.
18 kg ore, 45 kg charcaol; ore to fuel ratio 1 : 2.5.
Charge added every 20 min.
The slag-rich bloom weighed 9.5 kg

Iron, Steel and Swords script - Page 344

Illustr.
ModuleBlooms &BloomeriesThis was high-efficiency smelting. Limonite contains about 50 % iron so at most 9.5 kg iron could be produced. Even if
only halve of the bloom consists of iron this is a good result; compare to numbers given here.
More pictures of blooms and bloomeries can be found in the link.
Note that no flux was added. This implies that there was sufficient SiO2 in the gangue. Slag from smelting ironinvariably contains fayalite or iron silicate (Fe2SiO4), a member of the olivine group that constitute the Earth's mostcommon minerals by volume. SiO2 or quartz reacts with iron oxides in many ways; the end products being fayalite,
wüstite, the iron mono-oxide FeO rarely found in nature, some elemental iron (Fe) plus carbon mono and di-oxides.
What, exactly, you get depends on conditions; here are a few possibilities for the end result of all interesting
reactions:

1.

3 Fe2O + 2 SiO2 + 3 CO⇒

2 FeO + 2 Fe2SiO4 + 3 CO22.

2 Fe2O + SiO2+ 3 CO⇒

Fe + FeO + Fe2SiO4 + 3 CO2

3.

4 Fe2O + SiO 2 + 9 CO⇒

5 Fe + FeO + Fe2SiO4 + 9 CO24.

2 FeO + SiO2⇒

Fe2SiO4 + 909 kJ

About equal amounts of wüstite and fayalite, i.e. 2 FeO + 2 Fe2SiO4 plus a bit of this and that is what we call slagfrom bloomery iron smelting. It is liquid around 1200 oC (2192 oF).
The reactions above have been made "stoichiometric" for certain relations of iron and SiO2 gangue in ore. Since thefayalite forming process releases a lot of energy, far more than the other processes in the smelter (see the lastentry above), it will definitely take place and elemental iron can only be produced if some iron oxide is left over after
all the the SiO2 in the gangue has reacted. The reactions given above (and taken from Vagn Buchwald's book)correspond to the following iron : SiO2 relations in the ore:
1. Fe : SiO2 = 56 % : 20 %. An inadequate ore that will only produce slag.
2. Fe : SiO2 = 59 % : 16 %. The iron yield is 25 % relative to the iron fed into the smelter3. Fe : SiO2 = 64 % : 8.6 %. The iron yield is now a very high 62.5 %.
This is quite amazing! Change your ore "quality" by a few percent and your smelting results may change dramatically.
That's why you paid a lot of attention to your ore. You cleaned it as well as possible, you crushed it and then roasted it.
That process can be seen here. Roasting takes place around 500 oC (932 oF) for several hours and does a number ofthings:1. It removes water. Both the "regular" water and the crystal water in the ore by reactions like 2 FeOOH ⇒ Fe2O3 +H2O. In other words; it turns Goethite, limonite and bog iron into haematite.
2. It removes sulfur (S). Many ores contain some pyrite (FeS2 ). Roasting releases the sulfur according to 4 FeS2 +11 O2 ⇒ Fe2O3 + 8 SO2. The sulfur dioxide produced is a poisonous gas that escapes and will be noted by its
acrid smell. Since sulfur in iron is always bad news, this is quite important.
3. It makes the ore more crumbly because the iron oxide crystals will fall apart to some extent undergoing all thesereactions. This increases the surface to volume ratios substantially and thus makes the solid-state reduction
process easier that can only proceed via the surface.
4. It changes the color of the iron-bearing parts (bright orange if it is pure haematite). That makes picking of goodore pieces now easier. Some unwanted additions like copper may cause discolorations that allow to discard thecontaminated pieces.
So you did a lot of work before you started to actually smelt.
Anyway, the smelter is is now turned off one way or other and now it is time to get the bloom. That is not a problem aslong as the smelter was nothing but a hole in the ground about 30 cm across, lined with a few stones, and a clay tube
leading up about 1 m at most. You just tear down the whole thing. You can build a new one in a short time with little
cost and effort. The tuyere, the bellows and the connection between both are more critical.
You could also make make a bigger smelter but then tearing it down and rebuilding gets more expensive. More
important: the bloom might be too large to be wrought (= old-fashioned word for worked) "by hand". A bloom weighing
more then - very roughly - 10 kg needed more bang for compacting than what you and I could deliver with a hammer.
The smelter shown above did have an opening for retrieving the bloom (plugged up during operation) but since it was too
small, the smelter had to be dismantled. You can try to retrieve the bloom through the top of the stack but it ain't easy
either. All in all, iron bloomeries for more than 2000 years tended to be small and were only used once or - after repairs a few times for good reasons.
Metal engineers eventually, like after 1000 AD, found ways to have larger permanent smelters and to get the bloom
out without destroying the smelter every time. They also found ways to work those big blooms - with water-wheel
driven hammers! But we are still back around 1000 BC and we need to wait for about 2000 year before that is goingto happen.
The best one could do for more than 2000 years was to produce a bloom about 2 to 4 times bigger than what one
man could work. The big bloom then was cut into two or maybe four parts while still red hot. Then up to four smiths
could work it. Here is a picture showing a cut bloom.
Iron, Steel and Swords script - Page 345

Working your Bloom
So what, exactly, is a bloom, and how do I work it? As the pictures in the links show, a bloom is a red-hot mass of iron,charcoals, slag, and maybe pieces of smelter lining, weighing a few kilograms. If it is larger than roughly 10 kg, youmust divide it. That is easier said then done, especially without modern power tools.
You must now compact and refine your bloom. For that you hit it with a hammer. For starters, you need ahammer with a big head otherwise you just make dents in the red-hot porous mass that is oozing viscous slag.
That's why you use a wooden mallet and a stone or the slightly concave surface of a tree trunk as anvil. It's not thatwood makes a great hammer head or anvil. But if you ever tried to lift an iron hammer the size of the wooden malletshown below, you appreciate the wooden mallet. Same thing for the tree trunk. It will get burned but keeps the
bloom nicely in place.

Ready to compact a bloom

Bad bloom from
Roman times

Source left
Source right: From the "Hüttenberg" project under the direction of
Brigitte Cech; photo from Ruth Fillery-Travis; both University College
London (UCL). With friendly permission.

What you want to do is to hammer your bloom into an solid piece of "wrought" iron. Wrought because you wrought =worked it, not necessarily because it had a very low carbon content. This means that you must remove bits and pieces
of foreign matter, squeeze out the still liquid (if viscous) slag, and close the holes and pores in the iron.
This is hard work, necessitating a decent supply of beer. While I have never yet hit a bloom with a mallet as shown
above, I do have some hands-on experience of hitting things with big wooden (or iron) hammers for prolonged periods oftime, and I can testify that it is hard work, producing a magnificent thirst that cannot be quenched with water.
Hitting a bloom with a wooden mallet will only get you that far, though. At some point the bloom is just too cold to notice
your feeble hammer blows. You now transfer it to the hearth of a smithy, heating it up again, and banging it some more.
This you do on an anvil (stone in ancient times), using an iron hammer. In between banging you reheat the piece in yourhearth. You go for very high temperatures, necessitating a good air supply to you hearth. Very high temperatures inexcess of 1000 oC (1832 oF) make it not only easier to shape your piece, but re-liquefy still present slag and enable firewelding of the many seams.
Just banging on your bloom randomly will compact it some but you will not achieve optimal results. It takes someexperience and cunning to produce a nice bar of iron (or shapes like Celtic double-pyramid bar; see below) from agiven bloom. You will, for example, sprinkle some special sand on the mass from time to time, because that helps
to hammer or fire weld iron to iron. If you want to close holes, you must join iron surfaces, and this is not possible
as long as they are oxidized. Adding a bit of silicate (from quartz sand) will produce liquid fayalite when it reacts
with the oxide, the main material in slag, that you now can squeeze out. I'll get to that in more detail in a moment.
You also will tend to fold your flattened piece over and weld it together, and you repeating that several times. In
other words, you produce what some like to call a piece of "damascene" iron / steel. Well - you don't. All you try to
do is to make your piece of iron as uniform as you can, and folding and rewelding a lot does just that. Done
professionally we call it "faggoting". Try it with random lumps of brown (chocolate) and white dough. Flatten, fold and"weld" a few times and you have more uniform light-brown stuff.
Of course, the quality of a bloom matters very much in this. Some blooms are simply too bad for "processing"; andexperts can "see" that, it appears, and won't bother to work it. The "bad" bloom above was found in Hüttenberg; Austria,
one of the places where the the famous "Ferrum Noricum" of the Romans was produced between 100 BC - 400 AD. It
was found when the smelting place was dug up by Brigitte Cech and others like Thomas Birch. We must assume that it
was judged to be unworthy of use by the ancient smiths.
Here is a bloom from a modern experiment, it looks rather similar to the "bad" Roman bloom from above.

Iron, Steel and Swords script - Page 346

Bloom from a recent experiment
Source: Besucherbergwerk „Grube Wohlfahrt“When the smith is done, he has produced a shapely piece of iron. A straight bar, perhaps, or the famous Celtic "double
pyramid" bars (Spitzbarren) as shown below:"Double pyramid" iron bars found in my home town in2009
Source: Photographed at the "Special Exhibition Dedicated to the Celtsof the First Millennium BC"; Stuttgart, 2012/13

But no matter how good your bloom and your compacting skills: the iron / steel pieces produced contained slag
particles and maybe other inclusions, and their carbon content varied within a piece and between pieces (as we will
see in the next chapter). They may or may not contain relevant (varying) concentrations of phosphorous and otherstuff, too. Moreover, closing holes in the bloom and folding the workpiece many times produced plenty of weld
seams that can be perfect or bad, depending on the skills of the smith and local conditions. The specimen above,for example, show "cracks", probably from bad weld seams.
This kind of stuff can never be a match for inclusion-free homogeneous steel!
The Carbon Content of Your Bloom
Now I can no longer avoid dealing with the crucial question: What did those bloomeries really produce? Always wroughtiron (= soft iron with very low carbon content) as explicitly and implicitly assumed in most of the older "archeological"
papers? And never cast iron?
In the preceding sub-chapter I have already argued at length and rather convincingly (to me) that it is possible to produce
low carbon iron in a bloomery but that you just as well could get cast iron or anything in between, i.e. all grades ofcarbon steel. It now behooves me (love that word) to prove that claim. There are two possible ways to do that:
1. Analyze a lot of old iron and determine the carbon content, in particular for
everyday "wrought iron" stuff.
2. Run bloomery experiments just as it was done thousands of years ago andsee what you can get.
It is quite nice for me that the number of bloomery experiments done by all kinds ofpeople and thus also by people who don't know a thing about Material Science is
sky rocketing! Before the year 2000 or so, only a few smelting experiments weredone inside the scientific community, e.g. by Tylecote. Nowadays lots of people
with or without a scientific background go out, build a bloomery, drink some beerand smelt some iron. Even high school classes do it for their science projects. I'm
not sure if they drink a lot of beer and I don't even want to know how they keep
themselves amused otherwise out there in the underbrush.

Iron, Steel and Swords script - Page 347

Illustr.
ModuleResults ofBloomeriesThis is good! The kids and many enthusiasts out there do not know a thing about smelting except what they haveheard (or read) from others - just like the old Romans and so on. Many a hobby black smith or metal smelter started
with very little background knowledge but became a smelting expert by trial and error, who could raise a bloomery
and produce some good iron /steel without problems.
It's a rare moment! We also get to witness the errors in the present wild days of empirically re-inventing bloomery
techniques by trial and error! My guess will be that in a few years it is all over. The Internet will provide so many
(almost) fail-proof recipes for smelting a bit of iron that will work all the time. Just like in antiquity; it just took a bit
longer then for the knowledge to spread.
The link above gives some results from randomly selected smelting activities. A clear picture emerges:
It is perfectly possible to smelt cast iron, wrought iron, and anything in between in a simple bloomery.
It is also possible to smelt no iron, producing only iron-rich ("magnetic") slag.
Efficiencies (weight of bloom relative to weight of ore) can vary substantially; high efficiencies are possible.
Changing the carbon content of the bloom by changing parameters "by feeling" doesn't seem to work most of thetime.
Bloom quality can vary a lot, and the carbon content of a bloom can change considerably from top to bottom.
It does take a fairly large number of smelting experiments done in the time honored trial and error method before
you can call yourself an experienced smelter.
It is possible, however, to develop a smelting technique that produces what you want (i.e. low-carbon iron) mostof the time within the possibilties and constraints of your local environment.
It's not so easy to transfer a technology that works in one place to another one where the ore, charcoal and so on
will be somewhat different
Now let's look at the archeological record. Below I give carbon concentrations for some objects as given and discussed
in Buchwald's authoritative book.

Iron clamps Parthenon
447 BCRoman nails
40 AD

No

[C %]

No

[C
%]

1

0.395

1

0.019

2

0.419

2

0.21

3

0.117

3

0.04

4

0.104

4

0.07

5

0.350

Left: Iron stub for connecting column drums in-situ in
Ephesos
Right: Roman "standard" nail

The Greek routinely used iron clamps (always encased in lead) to keep layers of shaped stones together, and stubs
as shown between two column drums. This added resistance to shear forces as they might be encountered in an
earthquake. The clamps that kept the marble "bricks" of the temples together sure varied a lot with respect to theircarbon concentration. None was "wrought iron" in a strict sense (i.e. less than 0,1 % of carbon). That makes sense.
You want strong steel to make your temples earthquake-prove. I have my doubts, however, that the Greeks knew
much about the properties of their iron / steel.
Nails you typically like to be made from soft and thus very bendable iron. It thus makes sense that the Roman nails
are low in carbon. Three of them would even qualify as wrought iron.
Now let's look at some Celtic swords from around 350 BC. They all have been investigated in detail by R. Pleiner.
Vagn Buchwald was able to re-examine 23 of these swords, including the structure and compositions of the slag
inclusions. His results concerning the carbon and phosphorous concentration are shown below in a graphic
representation drawn with the data in Buchwald's book. The carbon concentration typically varies between different
parts in an unsystematic way and the measured range is shown as red bar. The phosphorous values represents the
maximum concentrations found.

Iron, Steel and Swords script - Page 348

Carbon (C) and phosphorous (P) concentrations in
Celtic swords from about 500 BC - 250 BC.
Source: Data are from Buchwald's book; p. 116

There are four wrought iron swords, rather useless one should think. But two of them are high in phosphorous andthus also quite hard. The rest represents a mixture of all kinds of carbon concentrations - between swords and in agiven sword.
Rehder in his wonderful book raises the same point. Bloomeries produce iron with a wide spectrum of carbon
concentrations. He analyzed data for 507 iron artifacts, spanning the time range from 1000 BC to 500 AD, and, after
eliminating cast iron ("which was so easily made") arrived at an average carbon concentration of 0.48 % with a range
from 0.001 % to 0.9 %. Rehder also reports on an independent work of Schaaber et al. where an average carbon
concentration of 0.53 % was found for 484 samples, mostly from late antiquity in central and southern Europe.
Rehder also makes a point that finished iron objects had experienced a lot of forging that must have lead to somede-carburization. I have discussed at length that carburization during forging is not impossible but unlikely and thatnot much will happen in any case. De-carburization is far more likely, since most parts of the forged objects will
experience oxidizing conditions most of the time - and that's when de-carburization takes place. It also will only
affect surface-near parts, but with a lot of folding and fire-welding, the effect might be noticeable throughout thevolume.
What's Left
Untold millions of bloomeries must have been used in Europe and the Middle East in the more than 2500 years between
1200 BC and 1500 AD. It shouldn't be too difficult to dig some up. What can we expect to find?
Not much exiting stuff, actually. Besides a (completely grown over) slag heap you can only expect some burnt
looking stones and discolored soil wherever there has been a hole-in-the-ground bloomery. With luck, maybe somepieces of the wall and the tuyere are still in-situ. With extreme luck, you might find an abandoned bloom.
Archeometallurgists actually have run bloomeries with all the trimmings (roasting the ore, forging the bloom, ...) for awhile. Then they tore down the smelter, cleaned up a bit, and went away.

The smelting place from above after finishing
SourceIron, Steel and Swords script - Page 349

After just a few years grass will have grown over the whole affair and nobody will recognize that the place was used
for smelting some iron some time ago. After a few thousand years, some topsoil has aggregated and nothing isvisible at all - by human eyes. With some special "eyes" provided by your friendly physicist or Materials scientist
around the corner that can also "see" (very small) magnetic fields, you will recognize something special there,
however.
When you dig it up, it might look like this:Remains of a Roman furnace in Hüttenberg, Austria
SourceNot much is left from old bloomeries and forges. Essentially you find some holes in the ground or just depressions withsome blackened soil. Maybe a few stones and some slag pieces if you just take in an overview. If that site is from 1000
BC or 1000 AD is not immediately obvious; the remains of smelting places look very much the same, regardless of age.
If you dig and look closely, however, you find much more:
1. Slag deposits from the "run-off" slag (Run slag, tap slag, ...) if the furnace was tapped for slag.
2. Furnace bottom slag (furnace bottom cakes) if there was no tapping and the slag collected a the bottom.
3. Hearth slag. That is slag released when the bloom is re-heated in the hearth. It trickles down and leaves a "cake"looking very much like furnace bottom slag.
4. Hammerscale or oxide particles that flew off when the smith banged on the always oxidizd hot iron.
5. Pieces of iron banged off from blooms and the hot iron parts.
6. Discarded "bad" blooms.
7. Hammer and anvil stones.
8. Furnace lining stones.
9. Remainders of flux and ore.
10. "Lost" items like an iron bar or beer bottles from more recent smelting.
No. 5 - 10 are obvious, and I won't discuss them. The first four items, however, warrant a few words (and pictures).
For finding the "run-off" or production slag, you may want to look around yourself. Then consider that those hillocks
and the large hills you see out there might be huge mounds of slag! We have seen that before in the context of copper
smelting. Now we may encounter really big deposits of slag. We definitely do!
In 1915 - 1943 the modern steel mills on the Island of Elba (Portoferraio) or just across in Italy (Populonia,
Follonica, Piombino) were fed with iron-rich ancient slag from the general area. Up to 2 million tons of ancient slag,
found in layers 2 m - 8 m thick, were "harvested" with heavy equipment. The slag was produced by bloomeries
running there for a long time, the maximum activity was after 450 BC. Ancient slag from bloomeries always contains
a lot of iron because iron oxide (= ore) was used as flux. Modern blast furnaces use limestone as flux (producing
CaSiO4 instead of FeSiO4) and thus can work with old slag.
True, the general area (including the Island of Elba) was a metallurgical center in antiquity (sort of an ancient
Pittsburg, Sheffield or "Ruhrgebiet") for many hundreds of years - but 2 million tons? Assuming that one bloomery
produces at most 50 kg of slag in one run, this means that 40 million bloomery runs must have taken place.
Assume somewhat smaller numbers, and it still boggles the mind.
So we could expect that the archeologists dug up a lot of bloomery remains and lots of artifacts related to ironmaking? Not so! First, the large strip-mining machinery left little behind, and second, the archeologists then did notcare all that much about blackened holes in the ground. They cared about the discovery of unrobbed Etruscan
graves around Populonia from about 900 BC - 420 BC that were hidden (and thus protected) below thick layers ofslag.
The Etruscians were about in Italy before and during the rise of the Roman empire and masters of copper / bronze
technology. They were also easy going, given to throwing good parties (look at the pictures in those tombs), and notabove making fun of their victims:

Iron, Steel and Swords script - Page 350

Etruscan tomb ("tumuli") at Popolunia; formerly hidden
under slag.
Inset: Embellishment on a chariot. Last thing you might
have seen while still alive.
Source: Internet commercials

In the graves some iron objects were found but few have been analyzed. As far as one can tell, the old Etruscianiron was, as expected, a mix of all kinds of grades.
Furnace bottom slag and hearth slag look rather similar. In the first case it is the stuff that collected at the verybottom of the bloomery and couldn't flow out because the tap hole was too high (or because there was no tap hole). In
the second case it is the slag that drips down from the bloom when it is re-heated to be forged to its final shape. Forging
sqeezes out the slag still in the bloom and possibly adds a bit more because the smith sprinkles silica on the bloom.
Some of the stuff clings to the bloom and only flows off during reheating.
Furnace bottom slag and hearth slag thus will be roundish and bowl-shaped on one side.
Here is a 100 ton furnace slag found in Rochester, USA, in 2013, when the City dug up a parking lot in order tomove some electrical lines in preparation for the construction of Rochester’s new marina. It so happens that in 1926
or so, the Quinnesee Iron Mining Co. operated a blast furnace right there, but when they folded and tore down the
furnace, they forgot to take the rather weighty furnace bottom slag along.

100 ton (about 220 000 pounds) furnace bottom slag inRochester, USA.
Source: "Rochester Subway".

The furnace bottom slag of an ancient bloomery looks about the same, except it is just much smaller.
Here is a typical hearth slag, cut into two pieces. It has the same basic geometry as a furnace bottom slag
because both once filled a round bowl-shaped depression.

Hearth slag .
Source: English Heritage Internet site. With permission.

There is no lack of ancient slag and analyzing it has become a major activity. Slag, however is always a complex
mixture of many ingredients; here is an example. It is therefore not easy to learn a lot about the smelting and forging
process from slag analysis alone. However, much progress is being made right now and the analysis of slag willcertainly provide major insights into ancient metallurgy in years to come.

Iron, Steel and Swords script - Page 351

Now to hammerscale, the last point of the list above that I will discuss. What is hammerscale? It is the oxide formed onyour iron when you put it into the forge fire. You then simply "burn" it. When you bang it with the hammer, the brittle
oxide breaks off in small fish-scale like parts. Small iron particles might break off too, becoming oxidized as the fly off,
and if your iron still contains some slag, droplets of liquid slag, solidifying as the sail off, will join the rest.
Here is a picture of hammerscale on the anvil:

Hammerscale on an anvil.
Source: Sorry, forgot.

Hammerscale is essentially Magnetite (Fe3O4). Quite a bit is produced during forging and that limits the time you
can heat and bang a piece of iron. It gets smaller all the time.
Hammerscale is a great ore. If you produce enough you can put it right back into your smelter.
Enough! It should have become quite clear that iron and steel was mostly made in small bloomeries for more than 2000
years. The product always contained slag inclusions, and carbon (and other stuff) in all kinds of concentrations. With
experience and cunning, the process could be optimized to some extent but the final product could never compete withuniform iron / steel that did not contain slag inclusions, meaning steel that was liquid once.
It remains to see how Europe and some of the East cultivated bloomers iron / steel technology and how in the far
East wootz steel came into being, a steel that was liquid once and thus free of slag inclusions.

Iron, Steel and Swords script - Page 352

10.3 Iron and Steel in Early Europe

10.3.1 Technology Transfer
Spreading the Technology
Way back I asked: Who smelted iron for the first time? When and where? And how, exactly?
I didn't really answer these questions because neither I nor anybody else knows for sure. If we discount the more or lessaccidental production of some of iron during copper smelting and the few if spectacular objects from early times, thebest we can say is that the systematic production of iron in bloomeries started around 1200 BC somewhere in Anatolia.
To credit the Hittites with the "invention" of iron, as archeologists were inclined to do in the past, is most likely
overstating the case. True, the Hittites left a lot of written documents where iron is mentioned but practically no iron
artifacts to speak of.
If we believe some ancient Greeks like Strabo (65 BC - 25 AD), we should look for the Chalybians, who possessed thesecret of steel making. Hence Chalyb=steel in Greek (and Latin), in contrast to "sideros"=iron. Besides the Greek
references we do not know much about these guys but there are strong hints that they lived in the general Colchis areaat the Black Sea coast as shown in the map below. The term "Chalyb" might come from the Hittite "Khaly-wa", meaningland of "land of Halys", which is also shown in the map below. The Halys river (now know as Kizilirmak) starts aroundthere.
Note that the Greeks wrote their stuff about 1000 years after iron became generally known and used. Their differentiation
between iron and steel might indicate that it took that long before metal workers could select and manipulate the stuff
from the bloomeries in ways where this distinction became meaningful, including proper forging and quenching for
getting hardened steel. Whatever. We must treat all these not-so-old writings like rumors and not as literal truth.
In this module I will give a very cursory look at the spreading of the technology and the trade with iron and steel"halfware" in mostly Europe. The "Eastern" technology of crucible steel will have its own module.
This chapter will be very patchy because the knowledge about these topics is patchy and because I want to keep thisshort. It goes without saying that most of what follows contains a lot of educated guessing.
What we do know is that iron technology spread rather quickly in the Mediterrean after 1200 BC. The source seems
to be present-day Turkey. One might assume that the collapse of the Hittite empire around 1200 BC displaced a lotof people, including skilled iron engineers, who were now free (or forced by circumstances) to move about and offer
their skills to all and sundry.
The map below, drawn after the map in Buchwalds's book, is rather trivial. What one sees is that the knowledge
about iron spread by "water" - along major rivers or by seafaring. Small wonder - that's how people did get around forlong distances. After you walked from Kiel in North Germany to East Anatolia once (and survived), you tended totake a boat for getting back.
The map also shows a few major places for iron production that I will discuss here.

The spreading of iron technology after 1200 BC
Large picture
Source: Inspired by the map in Buchwald's book.

Iron, Steel and Swords script - Page 353

Spreading iron technology means that people in some area learned how to smelt iron and how to forge it into
something useful. Essentially all you need is charcoal, iron ore and some clay for building the bloomery, plus a hearth,an anvil and tools for forging. If you can procure those things, that odd traveler who came by boat from far away (on his
own or as slave) will show you how to smelt and forge iron in exchange for some money or the opportunity to stay alive.
Chances are he won't succeed on his first try. As we have seen in all those modules before, you must do yoursmelting just right. Your gangue is "wrong", your bellows are leaky or especially efficient, your charcoal is too
reactive, and so on, and and all you produce is slag, useless cast iron, or small useless blooms.
Eventually, after optimizing local processes, you will be able to produce some iron. But some areas / people willproduce better stuff than others, not to mention that some produce their iron more cheaply than others. If for a given
product there are differences in quality and / or price you have all that is needed to start some trading.
In other words: the spreading of the technology did not preclude trading. You might make your own iron but you will
still import some from "specialists" who make a particular good (or cheap) variety. If conditions were right, you may
even have given up your own production in favor of imported stuff.
The exporters of iron / steel owed their success not just to secret procedures or some magic. More likely they had
better ingredients, a better organization, and a more motivated and skilled workforce. It is simply easier to makegood iron with nice "clean" siderite than with dirty bog iron, for example. It is thus no great surprise that certain
areas specialized in iron working quite early, and that their iron was traded wide and far.
What follows are a few remarks about some places of iron production. Taken together, one can get a feeling for what
has happened.
CyprusWhat we know with some certainty is that around 1100 BC iron appeared in "quantities" in Cyprus, Syria (Hama), andthe Levante (many places). Occurrences in the Aegean (mostly islands like Crete, Euboia, Naxos, Thassos but also themainland) and Anatolia are less pronounced. Here is a statistic compiled by Susan Sherratt 1).
Place Cyprus Syria
S.Aegean Anatolia/
LevanteObjectHama
1200 BC - 1100 BC
Knives

30

1

3

8

1

Dagger

3

0

2

0

0

Sword

2

3

0

0

0

Arrowhead

1

0

1

0

0

Other

7

0

2

0

0

Total

42

4

8

8

1

1100 BC - 1000 BC
Knives

22

6

30

8

3

Dagger

2

0

6

9

0

Sword

3

6

1

3

0

Arrowhead

0

4

5

0

0

Other

4

1

8

10

3

Total

31

17

50

30

6

The number of objects found is certainly only a small and unknown fraction of what was around. It thus may or may
not be halfway representative for the local level of iron technology. But that is all we have to work with. We candiscern certain trends however, with some reasonable probability for being true:
1. Iron in all places is no longer used for making jewelry and expensive representation items but for importantutilitarian stuff (A knife was one of your more important "tools" then) and weapons.
2. Cyprus was possibly a bit further along than the rest and specialized rather early on knifes. In fact, there aresome who believe that iron technology spread from Cyprus and not Anatolia.
3. Arrowheads signify that you can afford to loose your iron; it is no longer extremely valuable.
4. The relative lack of swords or other objects that would have needed a sizeable piece of "good" iron for forging
might indicate that the technology was not yet up to that task. Making lots of little objects (arrowheads) fromlots of small iron blooms was easy, making a knife from some medium sized one was possible if special,
and making a sword from a large piece or by fire-welding smaller pieces was nearly impossible.
5.
Iron, Steel and Swords script - Page 354

5. We have far too few pieces of really old iron!
.
Wherever the starting point for spreading iron technology might have been around 1200 / 1100 BC, at 500 BC, to give aclear date, about everybody in Europe and around the Mediterranean knew how to run a bloomery and how to produce
iron implements from the iron bloom produced.
Let's look at a few places to get an idea of what was going on.
The Etruscans - Populonia and Elba
I have mentioned Populonia and Elba before in the context of slag production during metal smelting. The whole area Elba and the Italian coast region just across - was an ancient metal center, sort of an early Pittsburg, run by theEtruscans and later, as the Etruscans became absorbed in the Roman Empire, by the Romans.
Ancient writers remarked on it, for example the Greek Diodorus (60 BC - 30 BC):"Off the city of Tyrrhenia known as Populonium there is an island which men call Aethaleia (=Elba). It is about one
hundred stades distant from the coast and received the name it bears from the smoke (aithalos) which lies so thickabout it. For the island possesses a great amount of iron - rock, which they quarry in order to melt and cast(philosophers never get it right) and thus to secure the iron, and they possess a great abundance of this ore. For
those who are engaged in the working of this ore crush the rock and burn the lumps which have thus been broken incertain ingenious furnaces; and these they smelt the lumps by means of a great fire and form them into pieces ofmoderate size which are iron their appearance like large sponges. These are purchased by merchants in exchange
either for money of for goods and are then taken to Dicaerchia (=Puteoli, Campania) or other trading-stations, where
there are men who purchase such cargoes and who, with the aid of a multitude of artisans in metal whom they havecollected, work it further and manufacture iron objects of every description."
The area, in particular Elba, had copper ore and huge amounts of iron ore. The Etruscans already had a large copper
smelting operation going there and smoothly adopted to iron at the latest around 600 BC, it appears. I have alreadystated that 2 Mio tons of slag have been produced in about 500 years, some of which could have been from copper
smelting since this also produced iron-rich slag. This number is actually debated and might be considerably smaller butthat doesn't matter for the three points I like to make:1. I could not find a single picture of an iron object or of the remains of a smelter from that area. This was simply notsomething one particularly looked for when the area was "cleaned" of its slag in 1915 - 1943.
2. This kind of negligence used to be the case for about all metal-producing regions. In 1980 or so, almost no oldsmelters / furnaces have been found and dug up, even so millions must have be around in Europe alone.
3. This has changed dramatically in the last 20 years or so. An increasing number of archeologists,archeometallurgists, lay-people, and guys like me are looking into the issue.
The Etruscan graves found under the slag deposits attracted far more attention than the slag for obvious reasons.
Fortunately, a few iron objects were found in these graves and thus preserved and described (but rarely analyzed).
Of particular interest here are the "spieti " (Italian) or "obelsikoi" or "oboli" (Greek), looking like thin (barbecue)
spits of iron or bronze. They can be seen as a kind of currency, and that will not be the last time we encounter ironpieces as a kind of money.

Oboli form Crete (Heraklion museum)A fascicle (=bunch, cluster, bundle) of iron oboli(You find out yourself what fascism has to do with this)Large picture of real spits
Source: Radomir Pleiner

We can be reasonably sure that the oboli and any other iron products from this region consisted of inhomogeneousforged iron, with varying concentrations of carbon and other elements (like phosphorous) and always a lot of slag
inclusions, typically elongated from smithing. Oboli, according to general theory, were a kind of currency, sort ofvery elongated coins, that you could use as money or directly as raw material of a certain value. You could forge aknife from am oboli, or you could use them as spits for roasting your chicken on the fire. Some modern
archeometallurgists even subscribe to a heretical point of view: Oboli were nothing but spits for cooking on an open
fire, as was the custom in those days. What else but iron would you use for a spit?
Below is what real spits looked like - they could easily have been made from oboli.
Iron, Steel and Swords script - Page 355

Iron spits for roasting meat
Source: Photographed in the Heraklion Museum, Crete

Ferrum Noricum
The Roman empire was rather large compared to the average distance people, goods and news could travel per day. It's
influence on present day Germans (Italians, French, ....) can still be seen and felt if you have sensitive and trained
receptors. The Romans were not only highly organized but used the specialities of the conquered territories to their best
advantage. They also left a lot of written stuff and that's how we know about the "famous" Ferrum Noricum; the superior
iron (actually steel) from the province Noricum.
Noricum used to be an independent kingdom (we believe) that became (peacefully) incorporated into the Roman
empire in 16 BC. It coincided with much of what now is Austria. Ancient Noricum included Hallstatt , a place thatgave the name to a whole culture (Hallstatt culture, 800 BC - 600 BC or Early European Iron Age). It also contained
a place (still) called Erzberg I ("ore mountain") close to the present town of Hüttenberg (cottage mountain or
possibly smelter (smelter=Hütte) mountain). That's where Ferrum Noricum was produced during the Roman times
and somewhat earlier during the (late) La Tène period (following the Hallstatt culture; 450 BC - the Roman conquest
in the 1st century BC). There is another place called Erzberg (II) in Noricum that is also known as an iron producing
place - but not before early medieval times. Iron production around Erzberg II went on until recently; it should not be
confused with Erzberg I.
The Romans run a kind of large-scale well-organized iron industry out of (present -day) Magdalenenberg or
Magdalensberg, the "city" close to Erzberg / Hüttenberg. It is all in the map below:

The Noricum
Large picture
If you are now a bit confused about all these folks and cultures (Romans,
Austrians, Celts, Hallstatt, La Tène,...) that's as it should be. Let's simplify and justlook at two cultures: The Celts, having their heydays from about 600 BC - 0 AD,
and the Romans who absorbed and replaced the Celts around 50 BC and later. The
Hallstatt and the La Tène culture (and others) are just expressions of Celtic "super"
structures.
The Celts are supposed to have been the first "iron masters" in Northern Europe;
the link goes a bit deeper into the Celtic Culture.
You might be inclined to associate Celtic culture with Ireland, Wales and Scotland
in more recent times because people there speak Gaelic, a kind of left-over Celtic
tongue. Historians are not so sure. Celts and Celtic culture did survive to someextent in these places after it was all but extinguished on the continent, but it did
not come from there.

Iron, Steel and Swords script - Page 356

Advanced
Link
The Celts

The Celts may have discovered and explored the Hüttenberg ore deposit in the first century BC. They might have had acultural center on Magdalenenberg, working and trading the iron from there and thus making it known to the Romans.
The Romans eventually - more or less peacefully, it appears - took over and lots of artisans settled there, making
Magdalenenberg at major hub for iron making and trading for centuries to come. It is possible that the fame of Ferrum
Noricum owes just as much (or more) to the organizational skills of the Roman and to the cunning of their smiths than
to the quality of ore and iron.
We have known for quite some time that Ferrum Noricum was famous in antiquity because the Romans wroteabout it.
Quite a lot, actually. However, besides the descriptions in the literature not much was known about this iron from direct
evidence. That has changed only recently and I will get to that. First, however, I like to give a few quotes from ancientreferences to Ferrum Noricum. That is easier said then done because all sources on Ferrum Noricum mention that there
are numerous references to its outstanding quality in ancient literature but very few actually supply quotes. Here is what
I found (sometimes translated by me):
Ovid (43 BC – 17/18 AD), was a Roman poet who is still well-known in educated circles.
He wrote: "...durior [...] ferro quod noricus excoquit ignis..." (...harder than iron tempered by Noric fire...).
One might conclude that he distinguished steel from iron and knows about "tempering". That word, however, haschanged its meaning in the course of time from "quenching" to heating up again. So what Ovid meant depends on
what tempering means.
Titus Petronius(14 AD - 66 AD), the author of the famous "Satyricon", has one of his figures, Trimalchio, praise his
cook in strong terms, finishing with: "... and since he is so gifted, I presented him knifes made from Ferrum Noricum
that I brought back from Rome..." . The knifes are fetched and admired for their sharpness.
There is more to this quote then meets the innocent eye. Trimalchio, a somewhat vulgar "noveau rich", shows hismoney by presenting his cook with a gift of not just one but several very expensive knifes, normally far too good forregular kitchen work. It's like you giving your cleaning Lady a Porsche instead of a subway token so she can get towork.
Galen of Pergamon (129 AD – 200/216 AD) we have met before. He was a prominent Greek-speaking Roman
physician, surgeon and philosopher; arguably the most accomplished of all medical researchers of antiquity. He
developed fine surgical instruments that needed to be made from the best iron "like Ferrum Noricum" if they should
be serviceable.
Marcus Valerius Martialis (known in English as Martial; 40 AD – 102 /104 AD), was a Spanish poet who publishedshort, witty and satirical poems in Rome. He was born in Bilbilis and praises this town as the place were first-ratesteel blades originated from, "better than the iron of Chalyb and Noricum". In his times the iron from Chalyb was
already a myth and not real.
Martial also refers to the use of hunting spears with tips of Ferrum Noricum that were used by the emperor Domitianjust for for playing around with! Once more a show of using the best and most expensive for inferior purposes, just toshow off!
Pliny the Elder (23 AD– 79 AD) or Gaius Plinius Secundus, famous Roman author, naturalist, philosopher, naval
and army commander (those guys were good at multi-tasking) writes:"...the high quality of iron goods is ensured by the ore as in the Noricum, by the working as in Sulmo, or by thewater as in the places given..."One of the "water" places is the Martial's home town Bilbilis from above.
Tremendous confusion ensued from that statement. Can you make great iron / steel from inferior stuff by working itin special ways? (Yes, but only up to a point). Is it enough to have good ore for making good iron / steel? (Notreally). Is the result of quenching, polishing, etc., dependent on the quality of the water you use (definitely not! - atleast as long it is half-way clean water).
The water myth comes up even today on occasion, e.g. if a Spanish merchant tries to convince a tourist that they
have "special water" there, making for swperior swords when used for quenching.
The 20th century literature about Ferrum Noricum is rather murky, mostly because it was based on discussing oldliterature. If we want to shed some light on the topic, it is illuminating to ask a few pointed questions:
1. The Ferrum Noricum of the Romans made its literature debut around 0 BC / AD. But the people in the Noricum
were smelting iron long before they became Romans. We must ask: Who? How? How early? How much? How
well?
2. Could it be that there were two kinds of Ferrum Noricum? Regular and superior? After all, it appears that there
was a major iron industry in the Noricum, making a hell of a lot of weapons for a large part of the huge Romanarmy plus plenty of everyday objects. All that iron could not have been extremely precious and costly. But thenwe also have the expensive prestige stuff mentioned by the literati. A case like Fiats and Ferrarris from Northern
Italy? 2)
3. Why was it somehow easier to make good iron in the Noricum then elsewhere?
4. What do we know about Ferrum Noricum from archeological digs plus metallurgical analysis of artifacts?
There is the stuff for an involved and lengthy PhD thesis. Applications from suitable candidates who are able to pay all
expenses (including those of the Prof. in charge) are welcome. Until we get that research done, I will give you just shortanswers.

Iron, Steel and Swords script - Page 357

1. The people in Norica were Celts before they became Romans. They did produce iron in Norica but notnecessarily only in Hüttenberg. There are indications that the Celts discovered the Hüttenberg "iron hat" (gossan) in
the second century BC and then exploited that source of minerals. If the Celtic iron / steel from the Noricum wasbetter than Celtic iron /steel from elsewhere is an open question, it seems.
The iron industry in Hüttenberg went strong ever since the Celts started it until about the fall of the (Western) Roman
empire in 454 AD. After a 500 year break (the "dark ages"), operations resumed in the 11th century and were kept
going until 1978.

2. I owe this question to Gerhard Dobesch3), and it makes some sense to me. The metallurgical information to datedoes not unambiguously support these claims but one might speculate that:
1. Particular good ore (see below) plus special skills in smelting and working the bloom produced better than
average but "cheap" regular Noric iron in bulk.
2. Highly specialized smiths could produce superior and very costly stuff from the regular Noric iron. They knew
how to pick different grades of iron or steel from the supply, and how to use theses materials for forging
special layered composite structures (as opposed to fire-welding random pieces). They even knew how to
carburize and case harden the outer layers.
Some more recent metallurgical investigations of Noric iron (see below) point in this direction but so far the "twokinds of Ferrum Noricum" hypothesis is just speculation.

3. The ore found in Hüttenberg is essentially siderite or iron carbide (FeCO3). Not the richest of ores but particularly
easy to smelt as people find out right now once more. Why? I shall leave that questions open for the time being(meaning I don't know the answer yet). An analysis of what one finds in roasted ore from the area as given in
Buchwald's book yields:
50 % - 54 % Fe
6 % CaO (quicklime)
5 % MnO
less than 0.0 8 % P and S.
This is not a bad mix for making "good" iron. It is often assumed that the relatively high manganese (Mn)concentration makes that ore so special because some manganese in the iron is always beneficial. Quicklime
might be good for making slag. It's not that easy, however. Manganese oxide is not so easy to reduce and does not
ensure sizeable manganese concentrations in the smelted iron as we shell see somewhat below. Nevertheless,siderite ore is easier to smelt in a bloomery and produced better iron than, for example, bog iron.

4. So far there aren't many analyzed Noric iron pieces but their number is going up as I'm writing this. This is due tothe ever increasing interest in ancient metallurgy and the many digs that have been started in recent years. New
archaeological excavations at Hüttenberg started in 2003 under the direction of Brigitte Cech. Earlier results are well
published in Harald Straube's book
Let's have a quick look at the pertinent results of analyzed Ferrum Noricum. I will only use two sources. There areundoubtedly more but as far as I'm aware of them nothing really new is added to what follows.

First we look at three swords likely made from Ferrum Noricum. All we need to do is to look at an old picture,augmented with some new data:

Iron, Steel and Swords script - Page 358

Carbon (C) and phosphorous (P) concentrations in
Celtic swords from about 500 BC - 250 BC. Threeswords are (probably) made from Ferrum Noricum
Source: Data are from Buchwald's book; p. 116

Vagn Buchwald has reasons to assume that the three Celtic swords marked were made from Ferrum Noricum. His
conclusion is based on a thorough analysis of the composition of the slag inclusions. If he is right, the three swords
do have a relatively high carbon concentration and a low phosphorous concentration, a possible mark of high quality.
But that is also true for some other swords. From the data given Ferrum Noricum is not outstanding.
Buchwald's final words are of some interest:
The general impression of Celtic swords, here covering a period from roughly 650 to 100 BC, is that the blade wasnormally manufactured from a single iron bar of no particularly good quality . .... No deliberate attempt at carburizing- or decarburizing - can be observed. It happens that a pearlitic hard steel is located along the edge or at the point,
but just as often the soft ferritic zones are located here. The laminated textures are due to the original
heterogeneous nature of the bloom and bars, and not to some deliberate piling of material with known carbon or
phosphorous content ....
Common to all the Celtic swords is the extensive cold working that has taken place."

Second we look at results from two kinds of early "Austrian" steel, published by H. Preßlinger and colleagues 4).
What they investigated in some detail were:About 30 specimen from around 100 BC and found North of the Danube In Gründberg, part of the present Linz
(indicated on this map). The objects found in 4 depots were mostly "utility" things like hooks or hammers and notmade from Ferrum Noricum.
About 10 objects from 100 BC - 100 AD found in Magdalenenberg, right in the heart of the Ferrum Noricum
region.
Major results for the Gründberg specimen were:
Hardness values (Vickers) ranging from 80 (quite soft) to 680 (extremely hard) and were not always
correlated to the observed structure.
Structures are typically ferritic (soft) or ferritic-pearlitic (medium hard). Occasionally grain-boundary ferrites(Widmannstätten structure) were observed, and martensite in one case .
Manganese (Mn), sulfur (S) and copper (Cu) concentrations were typically below 0,01 % and thus of noconsequence to properties.
Phosphorous (P) concentrations between < 0.01 % and 0.7 % were found, with very strong variations inside
one specimen.
Preßlinger concludes that the objects were made by fire welding of many thin layers with conscientiously picked
grades of steel, in particular phosphorous-rich steels for the intended hard parts.
It is not for me too put some doubts on the conclusion - but compare to what Buchwald has to say about "piling"right above. One particular interesting result, as far as I'm concerned, are measurements that offer a solution to the
puzzle contained in these data: ferritic or ferritic-pearlitic steel - but very large hardness? How is that possible? The
picture below gives the answer.

Phosphorous concentration and hardness achievableby cold working,Source: Redrawn (and augmented) after H. Preßlinger et al.

It's the phosphorous, of course. The red and blue dots are measured values, the red line gives (roughly) the
expected relation due to a basic solution hardening mechanism for undeformed iron. Cold working phosphorous
steel increases the hardness values rather dramatically. That is conceived as being good.
However, the steel might now be rather brittle and given to "cold shortening". Nothing seems to be known about
that.

Iron, Steel and Swords script - Page 359

Major results for the Magdalenenberg specimen (knifes, axes, hammer) were:
Structures span the range from ferritic to martensitic. No hardness values are given.
Phosphorous (P), Manganese (Mn), copper (Cu) (and presumably sulfur (S)) concentrations are very smalland supposed not to influence properties.
Carbon concentrations vary substantially from specimen to specimen (between 0.03 % and 1.5 %) and within
one specimen (e.g. 0.04 % - 0.16 % on the low side, or 0.52 % - 1.5 % on the high side) with about half ofthe specimen found on the large side.
Some specimen have large amounts of slag inclusions; not a sign of high quality.
All specimen were supposedly made by fire welding several pieces.
"Case hardening" was probably used.
What do we learn? First of all, to be careful with interpretations. There is some disparity between Buchwald's andPreßlinger's results. Of course, both could be right - the number of specimens investigated is far too small to allow fullgeneralizations.
What we might be able to conclude is that Ferrum Noricum was generally low in phosphorous but also in manganese.
The manganese oxide contained in its ore thus does not make for better iron because appreciable amounts of beneficial
manganese end up in the iron. It quite likely makes for better smelting, however, maybe by somehow helping to produce"better" slag? It is an open question at present.
"Classical" wrought iron with a low carbon and phosphorous concentration might be inferior to iron with an appreciable
phosphorous concentration, i.e. phosphorous steel. Wrought iron or more or less pure ferrite, in other words, is simply
not as hard as phosphorous steel. The latter cannot be hardened in the "usual" way but can become quite hard by cold
working. Phosphorous steel is reported to be difficult to forge or easy to forge, take your pick. A pure carbon steel withproper care to carbon concentration and hardening would be superior, though - provided it does not contain too many"bad" slag inclusions.
In other words: It is possible that very good smiths on occasion could make superior steel objects from very good
Ferrum Noricum , while only normally good steel resulted from normal Ferrum Noricum (a very good smith nevermakes anything bad). It is, however, hard to judge the fighting quality of an old sword by a metallurgical analysis ofjust a small portion that usually does not include the edge. "The harder the better" is certainly not generally correct.
I haven't found other comparisons between Ferrum Noricum and "Ferrum normalium", the iron / steel produced
elsewhere. At present we must admit that we do not really know what exactly made Ferrum Noricum so special. Maybe
the bulk of it wasn't all that great after all, and only some very expensive objects, made by special smelters and smiths,
made it into the literary fame that started the whole craze.
I have no problem to subscribe to the "two kinds of Ferrum Noricum" hypothesis but will not commit myself before more
results are in.
Snowdonia
The Snowdonia National Park in Northern Wales does contain a few early smelting places (plus some from far latertimes) - just like a few thousand other areas in Europe. The only thing remarkable about Snowdonia is Peter Crew andhis crew (couldn't resist). Peter is employed by the Snowdonia National Park Centre; here is the address (couldn't resist
once more): Snowdonia National Park Centre, Plas Tan y Bwlch, Maentwrog, Blaenau Ffestiniog, Gwynedd, LL41 3YU,
UK.
Peter decided to do some smelting experiments: "From 1983 to 2007 a series of nearly one hundred ironworking
experiments were carried out, primarily to provide data for the characterization and quantification of the slag from the
excavations". He also decided to eschew learning about the science of smelting first and thus to go about it like thelocal yokels 2500 years or so ago: "It is very easy, but potentially misleading, to use technological tricks from later
processes or other cultures". Use the materials you find locally, built smelters with it, following the "blue-prints" of what
you dug up instead of learning it from the master, do not use modern equipment of any kind, and learn by trial and error.
The result is: "Our early smelts were a disaster".
Several highly readable articles appeared, and in 2010 Peter Crew published"Twenty-five years of bloomery experiments: perspectives and prospects" 5); thequotes above are from this paper. Peter also became quite scientific in themeantime, witness one of his newer papers.
Of interest for us here is to learn that 25 years of experimenting did produce a lot ofinteresting results - some of which are shown below - and definitely helped ourunderstanding of early iron technology. However, Peter Crew did not yet reproduce
exactly what he has dug up. In essence, Peter and his co-workers learned a lot
from all their experiments, in particular that the Golidlock Principle strictly applies.
Everything needs to be just right if you want to do a high quality smelt.

Ilustr. Link
Odds &
Ends

Peter Crew investigated the influence of a lot of parameters on smelting. Besides playing around with the smelter
geometry and air blowing parameters, they looked in particular on different kinds and grades of ore, flux andcharcoal. Some quotes concerning results can be found in the "Odds and End" link.

Iron, Steel and Swords script - Page 360

Moreover, Peter Crew also looked into processing the bloom, from refining to making billets, bars, and finally artifacts
like knife blades. He needed the help of blacksmiths for doing that and learned that present-day blacksmiths display
various degrees of skills when faced with iron blooms. My feeling is that none of them would be up to the standards ofan ancient smith. But then, how could they? They have to re-invent all the trade secrets that were passed on frommaster to apprentice for millennia before they became lost in more modern times.
Peter Crew and colleagues produced a wealth of insights and data from their many experiments and from checking
with written accounts. I will give you just two pictures out of many. First, let's look at the average size of blooms asa function of time. Bloom size was limited for two reasons. First, in the beginning of iron technology you were happy
to get a bloom at all. In small furnaces, run without much experience, you tend to get a small bloom. Second,
blooms too large cannot be refined by hitting them with muscle-powered hammers.
Now let's look how bloom size developed (in England) between about 500 BC and 1600 AD:

Bloom size (logarithmic scale!) vs. time as deduced
from products
Source Peter Crew

Around 500 BC people in England and Northern Europe started smelting iron in relevant quantities, Bloom sizes
tended to be rather small, probably limited by technology. With growing experience, bloom size settled around 2 kg
for quite some time. That is an easy-to-work small size but large enough for making a few small object or a knife
blade or two. Iron itself was mostly traded in the form of billets, bars, currency bars, the latter with weights around
500 g.
Around 250 AD a "quantum leap" occurred. Bloom size increased about 5 fold to around 10 kg. New ways of forging
must have been used. What we see is probably the Roman experience with running a well-organized iron industry.
This allows, for example, to split a 12 kg bloom into 2 or 3 pieces while still hot. With enough smiths and hearth
places around and in working conditions, the pieces of a large bloom can now be tackled.
A huge leap forward occurred around 1500 AD. Huge blooms of 100 kg and more appear routinely. The innovation inthis case is the water-powered hammer that could deal with blooms this large. Look at the following picture to get
an idea of what that means:

Refining a big bloom with a "water hammer".
Source Peter Crew
Iron, Steel and Swords script - Page 361

This is a bloom weighing in at at around 40 kg. You could not impress it very much (in both meanings of the word)with an arm-wielded 2 kg hammer. It will, however, yield to that monster hammer that is powered by a substantial
water-wheel.
Now let's look at some data describing the efficiency of smelting. The curves below show how much iron you get invarious smelting experiments (A - E), and how much of that is left over after various forging steps, relative to the amountof charcoal used

The relation of charcoal to iron after the various steps
needed to make an iron object.
Reference lines for selected charcoal to iron ratios are also
given.
A: High P bog-ores, 8kg smelts in 25cm diameter
furnace, without slag tapping.
B: Bog-ores, with low P and moderate Mn, 10kg
smelts in 25cm diameter furnace, without slag
tapping.
C: Sideritic ores, 16kg smelts in 30cm diameter
furnace, with slag tapping.
D: Sideritic ores, 16kg smelts in 30cm diameter
furnace, with slag tapping, hot-bloom removal and
immediate refining, with re-heating in the furnace.
E: Bog-ores, with low P and high Mn, 32kg smelts in
40cm diameter furnace, blown with an air rate ofabout 1000 litres per minute, with slag tapping, hotbloom removal and immediate refining to a smithedbloom; cut to three pieces for refining to bars.
Source Peter Crew

If we look at curve C, for example, we see that this experiment yielded a bloom of about 3.4 kg for about 45 kg
charcoal burned; a relation of 13 :1.
After refining the bloom, about 1.8 kg of iron are left, decreasing to 1 kg after forging a billet, 500 g for the bar, andjust about 300 g left in the "artifact", a knife blade in this case.
Each heating and forging step looses iron because you cannot avoid losses by oxidation and flaking off. Moreexperienced smiths might be able to keep losses low but your are definitely loosing more than 50 % of your original
bloom weight to the necessary follow-up processes.
Even for curve E representing the most efficient smelting, about 120 kg of chacoal were needed to produce a final
product weighing 6 kg!

Iron, Steel and Swords script - Page 362

Wetzlar
The last specific entry here I selected more or less at random. "For the development of iron production in Germany as awhole, the sites at Wetzlar-Dalheim offer a unique insight into changing production patterns and techniques over thebest part of 1.5 millennia of bloomery iron production", to quote A. Schäfer from the University Bamberg (Germany). So
where is Wetzlar? And why does it strike a chord in the heart of any individual remotely interested in photography andmicroscopy?
To answer the last question first: from Wetzlar came the Leica , the most famous camera ever made. It's homewere the "Ernst Leitz Optische Werke", Wetzlar. Leitz is still a big name in microscopy.
Wetzlar is smack in the middle of Germany, a bit to the West, in the river Lahn valley. Around 15 years ago it
became clear that iron has been made and worked in the general area for quite some time, and it was decided tostart major investigations.
The investigations are still going on but it is quite clear by now that "the Central Lahn Valley between the eastern
fringes of the Westerwald and Taunus mountain ranges features rich iron ore deposits. Neolithic settlers, who
cultivated the fertile loess terraces about 5.600 BC, already made use of the haematite deposits as a colouring
agent. From the Latène Period onwards, local iron production can be traced at a number of findspots in the region.
Especially at Wetzlar-Dalheim an agglomeration of sites has been detected by a combination of field walking,geomagnetic surveying, drilling programmes and C14-dating". 6)
With a lot of work and detailed analysis of many thousand artifacts (and many known smelting / smithing places not
yet dug up), the following picture emerged:

Iron smelting / smithing activities around Wetzlar,
Germany"Cxy" refers to the various places investigated;
dates are mostly from calibrated C14 data.
Source: Redrawn with data from A. Schäfer 16)

Iron was smelted and forged in this area just about from the very beginning of iron technology in Northern Europe up to
the Middle Ages (and actually beyond) without any interruption.
Remains of smelters and smithies found indicate that the technology hardly changed within the 2000 year time spancovered. The older furnaces were of the "slag-bottom" type, i.e. they were not necessarily tapped for slag.
Technological advances seem to have run towards multiple uses of one furnace, i.e. providing some method to get
the bottom-slag cake out without completely destroying the furnace. The second furnace type was of the "Lovosice(Tuklaty) type", whatever that means. My money is on a strongly-blown slag-tapping type.
Looking more closely at the many artifacts unveils the influence of the Roman occupation and possibly also effectsof the Battle of the Teutoburg Forest in 9 AD, when an alliance of Germanic tribes led by Arminius ambushed three
Roman legions and their auxiliaries, killing about everybody, and halting Roman expansion for quite a while.
What Did We Learn?

Iron, Steel and Swords script - Page 363

From all the above some insights emerge:
1. It's a lot of work to make an iron object. Producing a 10 kg bloom keeps about 10 - 15 people busy (including thecharcoal maker, the ore suppliers, smiths, and so on) for days, and you can't produce more than a handful of
blooms a week. It follows:
2. Iron objects were still special and not cheap before the "industrialization" of the process around 250 AD.
3. Whatever you made, it wasn't wrought iron. You had a mix of carbon-rich and carbon-lean iron, often with
substantial amounts of phosphorous (and possibly some other stuff) in just one bloom. You might also find large
variations in "steel quality" from boom to bloom.
4. But you also had experienced smiths who could judge the quality of a piece of iron / steel by a number of ways
(some probably lost) and work "good" pieces into rather satisfying products.
5. Most iron products were made by haphazardly banging together whatever grade of iron / steel you had in yourshop. That's why we find knifes with hard cores and soft edges and many objects where the carbon and / orphosphorous concentration changes unsystematically from here to there.
6. However, some guys somewhere and sometime knew exactly what they did. In fact, smithing skills around 400
AD allowed to produce wonderful pattern-welded blades and were never surpassed. Some smiths even had aworking knowledge of case hardening and used that conscientiously. There must have been some frustration,
however, for sometimes it worked,and sometimes it did not.
Great. But the headline was: Technology Transfer - Spreading the Technology". I bet you forgot. What did we learn
about technology transfer from looking a the five places enumerated above? Not all that much, I do admit that.
Nevertheless, I will dare to draw a few conclusions!

1. It did take quite some time for iron technology to get out of Anatolia / Cyprus / Palestine (and possibly Iran). In
most of Italy, Spain, and Egypt, plus pretty much all of Northern Europe, iron did not come into frequent use before
about 800 BC if not a few centuries later. In Greek there are signs that iron was used around 1100 / 1000 BC but
then "disappeare" for a few centuries, re-emerging again around 700 BC.
Anything you could call "technology transfer" can't take that long. So what happened? Well, for technology transfer
you need three ingredients: 1. A society that has the technology, 2. A society ready to receive the technology, and3. Ways / people for transferring the technology. Sounds simple but the emphasize is on "A society ready to receive
the technology". A "society" simply demands a state of organization far more complex than that needed for runninga tribe or clan, and "ready" means just that. Look a than example from today. Germany does contain a highlyorganized society that can make microelectronic products or solar cells. I, personally, would be willing and capable
to transfer the technology (for a small consideration, of course). Well-defined societies in (pick about any country /society in Africa / Arabia) do exist and might be eager to receive the technology. They are not ready, however.
I don't think it is an accident that "local" iron ages are associated with the rise of large-scale societies like theEtruscans, Celts or Romans.

2. Emulating a smelting process that worked in Anatolia, or in some other place like Elba or the Noricum, most
likely wouldn't work all that well. As we have seen in all cases, everything must be just right - for your local
conditions. While you can learn about the basic process of smelting iron from listening to what some traveller has tosay, you must optimize the process for your local conditions by trial and error. That is a tedious and costly process
without any guarantee that you will make it.

3. Learning the art of forging from hearsay - veything from working your bloom to actually making a knife blade - islike learning to knit a sweater with a complex pattern or to build a Stradivari from hearsay. It takes years of learningand practicing under the supervision of a master before you can call yourself a blacksmith. And an experienced
blacksmith who had made it from Cyprus to England in 1000 BC, say, would not have found it easy to practice hiscraft: no iron, no infrastructure for all the things he needs.
Transferring just knowledge, even in the form of experienced people, is not good enough. You need to transfer awhole infrastructure including a certain mind set of the people involved.
I was lying above. I could not transfer the technology of making solar cells to the Congo, say. Why, the people there
don't even need me. They just need to buy a few books that contain all there is to know about making solar cells.
You could buy those books and start to make solar cell. I bet you wouldn't be sucessful. OK, out of the goodness of
my heart, I send you some PhD students who have deep hands-on experience in the business. You know what?
You, together with these knowledgable foreigners, still won't be making solar cells. I'm quite sure of that.
Technology transfer is just not all that simple in other words.
Assuming that some technology exists somewhere, technology transfer only happens as soon as some area / society
is ready and connected to the rest of the world. Then it will spread in a self-organized way and possibly even progress
rapidly beyond the level of the society where it first evolved. Witness the advent of metallurgy in China and the Roman
empire after these cultures were ready. Due to their then unmatched organizational skills, they quickly turned smelting
and metal working from isolated artisan procedures to industrial activities.
So far so good. The problem we face now isIron, Steel and Swords script - Page 364

Who discovered steel technology
for the first time?
When and Where?
With steel technology I mean:
Realizing that there are different "grades of iron" called steel.
Finding a way to sort these different steels from one or more blooms into at least three groups (too soft, too
hard, just right).
Producing halfway uniform pieces from the members of one group by fire-welding.
Producing knife or sword blades by fire-welding pieces of different steels with the soft / hard parts in the rightplaces.
Going through the proper processes for case hardening, including quenching from high temperatures and andpossibly subsequent tempering at medium temperatures.
This is a tall order. It includes paraphernalia like recognizing phosphorous steel and knowing that it can't be hardened by
quenching, being able to do all the forging without too much loss of material and carburizing / de-carburizing the outerlayers, and being able to produce a longish object like a sword blade in a way that makes its structure rather uniform
throughout the length even so you can only work a small part of it at a time. Nobody usually has a hearth more than ameter long, after all.
Note that finding some martensite in some old steel does prove that the smith has thrown the red-hot object into
cold water, indeed. It does not prove, however, that this smith knew a thing about steel technology. He might havethrown all his finished products into cold water, just to safe time, not caring if he had wrought iron, phosphorous
steel (both not given to hardening upon quenching) or proper carbon steel that would produce some martensite.
Having halfway well-defined and different grades of carbon steel is the key to steel technology. You might get that bymastering smelting to a degree where you could produced rather homogeneous blooms with a certain carbon
concentration or by picking various grades from a bloom with mixed compositions.
Let's see if looking into the iron / steel trade will help us there.

1)

Susan Sherratt: "Commerce, iron and ideology: Metallurgical innovation in 12th-11th century Cyprus"; in: Karageorghis,
Vassos, Cyprus in the 11th century B.C.: proceedings of the international symposium organized by the ArchaeologicalResearch Unit of the University of Cyprus and The Anastasios G. Leventis Foundation, Nicosia 30-31 October, 1993, 59106, Athens: A.G. Leventis Foundation

2)

Radomir Pleiner: "Iron in archeology. The European bloomery smelter". Archeologicke Ustav AVCR. Praha, p. 400

3)Gerhard Dobesch: "Zweierlei ferrum Noricum?", Mitteilungen des Montangeschichtlichen Vereins Hüttenberg Knappenberg, Folge 18, Nov. 2011, p. 1

4)

H. Preßlinger, E. M. Ruprechtsberger and O. H. Urban: "Stahlwerkstoffe in der Kelten- und Römerzeit – Teil 1 und 2";
BHM, 152. Jg. (2007), Heft 5, p. 146- 150, and BHM, 152. Jg. (2007), Heft 5, p. 232 - 234.

5)Peter Crew: "Twenty-five years of bloomery experiments: perspectives and prospects", in D Dungworth and R Doonan(eds) 2013, Accidental and Experimental Archaeometallurgy [25] (London: Historical Metallurgy Society), p. 25-50

6)

Andreas Schäfer: "Zwischen“ Dünsberg und Waldgirmes. Wirtschaftsarchäologische Untersuchungen an der mittleren
Lahn" in: Berichte der Kommission für Archäologische Landesforschung in Hessen, Vol. 10 (2010) p. 69 – 90 and in
Abstracts of Second International Conference Plas Tan y Bwlch 17th – 21st September 2007: Early Ironworking in Europe
II, archaeology, technology and experiment.

Iron, Steel and Swords script - Page 365

10.3.2 The Iron Trade
The town I grew up in after 1950 had around 1000 inhabitants. It was essentially a "sleeping town" for the workers andemployes of the factories and businesses in the near-by cities but also still a community of farmers and artisans. Of
course there was black smith (and a cartwright, glazier, carpenter, ...), and he was working right across the street frommy parent's house. Same thing in all the other towns with a farming background. My grandfather actually was the blacksmith in another small town with less than 1000 inhabitants. So was his father and grandfather.
I'm absolutely sure that any community with more than 500 inhabitants or so supported and needed a black smith("Schmied" in German) for about 2000 years until - roughly - 1960. The surname Schmid / Schmidt / Schmitt /Schmit is No. 2 on the list of the most frequent surnames in Germany, only bested by "Müller" (you guessed it).
It is clear that all those smiths' could not make their own iron / steel but bought it. The major source was the next
local smelter "facility" of course, but some long-distance trade with special merchandise also existed.
As soon as people started to make iron in quantities, they also started to trade the stuff. The roots of the iron trade thus
go back to distant antiquity; we just don't know all that much about it.
As we have learned in the preceding parts, a smelter makes a bloom, and this bloom should be processed immediately
into one or several pieces of iron that can then be used for making products. These iron pieces tend to be more or lessstandardized for good reasons:
1. The black smith working the bloom (or parts of one) needs to have some idea of what he is going to make. Using
the same basic geometry every time makes the work easier.
2. A black smith who has worked a lot of blooms will have developed a good feeling for the quality of the stuff he isbanging at. He might be inclined (I'm guessing this!) to use different shapes for different grades.
3. A black smith who has worked a lot of blooms knows that he has to do a lot of fire welding and that the quality ofthe stuff he is making depends on the quality of the bloom and the quality of his work. The iron is of high quality if
it can be forged into thin pieces without cracks. Standard shapes thus might have thin parts as quality
demonstrators.
4. A black smith who works in a fully organized "industrialized" facility, for example in a Roman iron factory, simply
produces the prescribed shape, following the Roman Army standards concerning the shape of iron goods to adot.
5. Iron slated for export is given shapes that allow easy handling and stacking.
Of course, standards differed between areas / countries and changed many times during the 2000 years or so iron wasmade in bloomeries. Below I look at some of the better known early European trade standards. More information in
Pleiners book: Iron in Archaeology - Early European Blacksmiths.
The double pyramid or bipyamidal bars (German: Spitzbarren; English: double - pointed ingots of continental type)are mostly found in what used to be the Western part of the Celtic heartland - Switzerland, Eastern France, South
Germany. They go back to the La Tene period or to about 450 BC - 0 BC / AD. Whole hoards have been found in thisarea plus the occasional single specimen in Scandinavia, England or somewhere else in Europe.
Here is a map. Red symbols denote single finds / small amounts, big green symbols indicate findings of hoards or large
amounts; some major cities are shown for orientation.

Map of Celtic double pramid irons (Spitzbarren) finds
Source: After a map in a brochure of the Württembergisches
Landesmuseum, Stuttgart, Germany

Interestingly, Sargon II, who ruled the Assyrians from 722 BC – 705 BC, was in possession of a tremendous
treasure of iron that was stored in the palace of his capital Dur Sharrukin, present-day Khorsabad. One Victor
Place, resuming excavations started by Paul Botta in 1843, found 160 tons of iron just in storeroom 84. Most of thatiron was in the form of bipyramidal bars weighing 4 kg - 20 kg. Metallographic investigations by well-known
Iron, Steel and Swords script - Page 366

Radomir Pleiner2) showed that this iron was rather non-uniform stuff, a mixture of wrought iron, mild steel and hardsteel steel, with plenty of slag inclusions. Interestingly, some tools like hoes and spades, where one would haveexpected steel edges, tended to be of low-carbon wrought iron.
Ewart Oakeshott takes this as an indication that the Celts originated from Assyria but this view is not popular withhistorians.
That's what one can find about Sargon's iron. What one cannot find are the present whereabouts of these tons ofiron, or more than a handful of pictures. Here is a picture of a Celtic bipyramidal bar, some from present-day Poland,
and a specimen from Khorsabad

Double pyramid iron bars,
Top: Celtic, South Germany; 5th - 1st century BC
Large picture of other bars
Middle: From the "Lausitz Culture" (1200 BC - 500 BC).
Bottom: Khorsabad; 717- 705 BC
What was made from bars
Source: Top:Photographed at the Special Exhibition Dedicated to the"Celts of the First Millennium BC"; 2012/13 Stuttgart, Germany. Bottom:
Internet; Chicago Museum.

I don't know if the early Celtic smiths produced bipyramidal bars because they somehow carried on the tradition of
the Assyrians. If not, they must have hit on that shape for reasons that evade us. One might speculate that abipyramidal bar is he best compromise between a rectangular bar or block (most easy to pack and store) and adrawn-out geometry with thin parts (best to judge quality) but who knows.
One might also speculate that a bipyramidal shape allows the smith easy working. Since he mostly makes small
objects like nails of knife blades and not swords, he only needs to heat the thin parts for drawing out a sufficientamount of iron for the task at hand. This is the explanation you find in the "Landesmuseum Halle", together with animpressive illustration .
Celtic double pyramid bars have been extensively investigated too, and were found to be rather heterogeneous. They
cover the whole range of carbon and phosphorous iron so typical for these times and must have been the raw
material Celtic swords and other objects were made from.
Currency bars look a bit like a half-made swords. Their German name is "Schwertbarren" ("sword bars") and while thisname is self-explaining, "currency bars" is not. They were found mainly in England. When Caesar invaded England in 54
BC, he noticed that the early British smelted a bit of tin and iron but imported copper. He also was of the opinion thatthe British used standardized (more or less) bronze bits and iron staves as a kind of currency instead of coins. Caesar
wrote that down in his "De Bello Gallico" and untold numbers of High School students had to suffer through it. In the
19th century Caesar's influence finally lead early archeologists to coin the designation "currency bars" for these peculiar
objects.

Iron, Steel and Swords script - Page 367

Celtic currency bars; around 200 BC
Source: Photographed at the "Special Exhibition Dedicated to the Celtsof the First Millennium BC"; Stuttgart, 2012/13

Currency bars may have been used as a kind of money but this is open to some doubt, as in the case of theEtruscan / Greek oboli. They certainly were also just the raw material that a smith bought from some merchant obviously paying with some other kind of money. There are around 20 different kinds of currency bars, possiblyreflecting different grades of iron, different areas of origin, different smiths, or whatever.
Currency bars are rather heterogeneous. They cover the whole range of carbon and phosphorous iron so typical forthese times, etc., etc. No difference to bipyramidal bars, in other words. They were, as Buchwald points out, "farfrom being a high quality material fit for swords, sickles or knifes".
So why, oh why? Why this particular shape? I certainly don't know. I can only guess. A drawn-out thin piece of irondoes allow a better assessment of quality. The fact that it could be forged into this shape already is a sign of someminimal quality. More important, perhaps (I'm guessing) is that the surface / volume ratio is large, so there is a lot of
surface to look at and significant inhomogeneities might have made themselves conspicuous to a trained observer.
While you can always bang a thick piece of iron (like a bipyramidal bar) into something thin, the reverse is far moredifficult. Currency bars therefore are of limited use.
Just the opposite is true for billets or whole small blooms just "wrought" a little bit, and any number of shapes (including
weird ones like the "four-fingered blæsterjern" or clod).

Blooms, billets, and a clod for trading / paying (?)
Source: Peter Crew and Buchwald

This (British) stuff is still relatively early (long before the Roman occupation) and more or less local. I won't go
deeper into what it might mean, partially because I do not have the faintest idea. From a quality point, the hooked
billet shown above is relatively solid, not showing obvious welding flaws, but that is not necessarily true for others.
The clod is from Scandinavia (essentially Denmark) and was used by farmers to pay their taxes with at least as
early as 1500. The cuts obviously allow to assess the quality.
Iron, Steel and Swords script - Page 368

More serious trading started when the Romans were running things in large parts of Europe. This was to be expected;
just look at the dramatic increase in average bloom size around 200 AD. We know something about the Roman iron
trade from pictures and (presumably) writings and a bit from archaeological finds. This link leads to a paper of Janet
Lang that describes the Roman iron and steel technology quit nicely
The Romans had rectangular standardized no-nonsense bars in several sizes, sometimes stamped. Some of these bars
have been dug up but the most miraculous finds are from ships that went down and stayed there for almost 2000 years.
There are plenty of Roman iron bars from 16 shipwrecks in the Mediterranean, and some if not most of that iron was
most likely made in the Populonia area, between 150 BC - 400 AD.
Here are some bars seen in-situ on the bottom of the Mediterranean.

Roman iron bars in-situ on the bottom of theMediterranean
Source: M. Feugères and V. Serneels: "Recherces sur l'economie dufer en Meditérranée nord-occidentale", Monographies Instrumentum 4(1998) p. 263.

Roman iron bars recovered from the Rhone
shipwrecks
Source G. Pagès et al.

A recent in-depth work1) analyzed a number of the Rhone shipwreck bars in great detail; this link leads to the paper.
The results are what one should expect by now: it's rather bad iron - by today's standards. The carbon concentration
inside a bar varies quite a bit, and there is (inhomogeneous) phosphorous, not to mention pores and slag inclusions
and bad welds. Here is a picture:

Iron, Steel and Swords script - Page 369

Etched bar (composite) and data obtained
Large picture with more details
Source G. Pagès et al.

These iron bars are from 27 BC - 96 AD. They were made to exacting standards and obviously important enough toship them a few hundred miles. But they simply did no consist of very good iron / steel.
We are forced to conclude that these bars represent the best the Romans had, at least for general use. Maybe their"Ferrum Noricum" was better. It appears to have been phosphorous-free but we do not yet know enough.
Iron trade has never stopped. It might have been confined to short range and low volume in troublesome times or remoteregions, but local smiths always must have had some sources. In the Middle Ages it was more diversified, trading welldefined grades of iron or steel.
However, looking at the iron trade has not helped us to answer the big question from before:

Who discovered steel technology
for the first time?
When and Where?
And with steel technology I still mean the whole range: Realizing that there are different "grades of iron" called steel,finding a way to sort these different steels from one of more blooms into at least three groups, and so on and soforth.
As I'm writing this I do not yet know the answer. I do know, however, that the advent of the pattern-welded sword at
the beginning of the end of the Western Roman empire (around 375 AD, when the migration period started by thearrival of the Visigoths) demands mastery of steel technology.

1)

G. Pagès, P. Dillmann, P. Fluzin, L. Long: "A study of the Roman iron bars of Saintes-Maries-de-la-Mer (Bouches-duRhône, France). A proposal for a comprehensive metallographic approach", Journal of Archaeological Science 38 (2011)p. 1234 - 1252

2)

Radomír Pleiner: "The Technology of Three Assyrian Iron Artifacts from Khorsabad"; Journal of Near Eastern Studies, Vol.
38, No. 2 (1979), pp. 83 - 91

3)

Zbigniew Bukowski; Warszawa: "Die ältesten Eisenfunde und Eisengewinnung im Bereich der Lausitzer Kultur im
Flussgebiet von Oder und Weichsel", in: Frühes Eisen in Europa. Festschrift Walter Ulrich Guyan zu seinem 70.
Geburtstag (Deutsch) Hardcover – 1981 by Harold Haefner (Herausgeber); p. 69

Iron, Steel and Swords script - Page 370

10.4. Crucible Steel

10.4.1 The Making of Crucible Steel in Antiquity
Debunking the Myth of "Wootz"
Before I start on "wootz" I want to be very clear on how I see this rather confused topic:
There never has been a secret about the making of crucible (or "wootz") steel, and there isn't one now. Recipes
for making crucible steel were well-known throughout the ages, and they were just as sensible or strange asrecipes for making bloomery iron or other things.
There are many ways for making crucible steel. If the crucible process worked properly, the steel produced was
fully liquid, and it didn't matter much exactly how you made it. If the process did not work well and the steel was
only partially molten, i.e. a mixture of liquid cast iron and solid austenite, the product was not good steel.
Besides differences in the (always large) carbon concentration, the concentration of impurities might also be
different - just like for bloomery steel. This might lead to differences in properties for comparable carbon
concentrations, for example the susceptibility to cold shortness or the ability to form a good "watered silk" or"water" pattern.
Crucible steel that has been liquid once is relatively homogeneous and slag-free - in contrast to bloomery steel.
That is where crucible steel is "better" than bloomery steel.
Crucible steel is always high carbon if not ultra-high carbon steel (UHCS). This is generally not so good. However,
mixtures that would, for example, have produced 0.8 % carbon steel, a steel optimal for many applications, would
not melt at the temperatures available. Crucible steel thus is a compromise. It is very hard but also very brittle
and almost useless in its "as made" state.
Some products like surgical knifes, files or punches (but typically not swords) are best made from high-carbon
steel. In this case crucible steel was fine. It closed the gap between low and medium carbon bloomery steel andtoo-much-carbon cast iron. There was no other easy way to cover the 1 % - 2 % carbon range.
Special processing, including very special forging techniques, allowed to make products like swords from crucible
steel that were very hard throughout but not completely brittle. Like any homogeneous hard steel, they could bebend a lot before plastic deformation or fracture occurred, in contrast to not-so hard and slag inclusion containing
bloomery steel swords. Slag inclusions simply trigger early fracture.
Some crucible steels could be induced to precipitate their carbon inhomogeneously. The cementite formed was
not distributed evenly but arranged in such a way that a visible pattern could be produced at the surface. Thesesteel blades with a "watered silk" pattern or "water" pattern for short, were highly priced in the Arabic cultures
but not necessarily better than featureless blades. There were in fact not as good as blades made fromhomogeneous steel.
The term "wootz" is rather meaningless in all of this. It is supposed to be some special kind of crucible steel but
nobody knows what, exactly, makes it special relative to "non-wootz" crucible steels. One might reserve the term
for those crucible steels that can produce a "water" pattern. The problem with this is that nobody can sort given
crucible steel ingots into "wootz" and "not wootz" before all the forging takes place. There are just no clear
criteria.
Crucible steel was made in India and in large parts of Asia since at least 500 AD, possibly much earlier, up to
the end of the 19th century - but not in the "West" (and China). That is not so much because "the West" didn't
know the secrets of making crucible steel; it didn't want to make it.
If you are dreaming of wielding that wootz super-sword one day, enabling you to beat thecompetition, kill the dragons and win the heart and more of all those damsels out there sorry for letting you down. My advice is to go see a shrink about the possible meanings ofthose dreams.
Now let's see what one can find out about crucible steel. The swords made from crucible steel will be dealt with in somedetail in the next chapter.
What is Crucible Steel?
Can you produce iron in a crucible? Well - why not? Take a crucible, fill it with a mixture of (powdered) iron ore andcharcoal, and heat it up. There is something like a direct reduction process between iron oxide and carbon that
produces iron and carbon monoxide. I have described that process in some more detail in a science module. If
something is possible, chances are that somebody did it. So did our remote ancestors make iron and steel in a
crucible?
No - they didn't! It's not as simple as it sounds. There are a few catches:
Even if some iron is produced: as long as it doesn't melt, you cannot expect to find a bloom or a solid pieceof iron in your crucible after cooling down. How are those iron particles all over the place supposed to get
together and form a bloom? You might produce slag that could help forming a bloom but trickling down in a
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powder is difficult. If you use big lumps of ore and charcoal not much reaction is possible because of thestrongly reduced contact area.
Melting the iron might help - but that requires very high temperatures in excess of 1500 oC (2732 oF), noteasily attained in antiquity.
If you could produce temperatures that high, you needed a crucible that could survive this temperature while
not reacting with its contents. Another tough assignment to meet in antiquity!
If you could do all this, chances were that you started a run-away reaction, exploding your crucible.
Maybe in the 19th century iron was produced in a crucible; there are some vague reports about that 4). Whatever
there might have been - direct reduction in a crucible was and is of no importance. When we talk about crucible
steel we do not talk about making it by direct reduction. We make it by dissolving carbon in old-fashioned bloomery
iron / mild steel by turning everything liquid.
I'm starting a touchy business here and want to be very clear. Whenever I use the assignation " crucible steel" in what
follows, I mean:

Crucible steel = high-carbon steel made by enriching low-carbon
iron / steel with carbon in a crucible in the liquid state

Why is crucible steel a touchy business? There are multiple reasons. Here is the list:
Crucible steel is almost a synonym for "iron / steel of the East". Many regions / cultures / nationalities
compete for the honor of having been the inventor of this "superior" steel.
The early history of crucible steel is not all that clear, nor are the details of the particular technology that wasused in certain places and times. That does not prevent a lot of people from having strong opinions andemotions about that.
Extremely good swords have been made from crucible steel. They were far better than their Westerncounterparts! Or they weren't. Strong emotions about this topic are ignited as soon as the magic word "wootz" is mentioned.
Some crucible steel lends itself for making blades with a pattern often described as "watered silk" pattern,"water" pattern or "true damascus" pattern. These patterned blades are (wrongly) believed to be the best
blades ever made. I like to call it a "water" pattern not only because this is a standard expression for this but
also because the girl friend of my son, when she saw a wootz blade for the first time in her life,
spontaneously called it a "pattern like flowing water".
It is hotly debated what kind of factors need to come together to produce coarse cementite particles that are
non-randomly distributed in a way that forms the "water" pattern. Lots of emotions again - but the final word
isn't yet in.
Many (wrongly) believe that the technology for making crucible steel and the rather special forging techniques
for making patterned blades was lost centuries ago, and that the "secret" for making "super" steel will remain
lost forever.
Indian crucible steel has been known in the "West" for quite some time without anybody paying muchattention. It became "famous" late in the late 18th and then 19th century, when Western intellectuals"discovered" the wonders of the Orient, and not, as many believe, during or after the crusades.
Western guys (including scientists) created considerable confusion around the "secret" of wootz steel. To
some extent this was deliberate for all kinds of non-scientific reasons (like money). Mostly, however, theconfusion was not so much about the secrets of wootz steel but about the secrets of steel in general.
In what follows I will look into crucible steel in a scientific, detached, objective and unemotional way. You mustbelieve me or I will rave and scream, haunt you in your dreams, curse you and your descendants, send you
unpleasant deceases like kneasles or smallcocks, and inform the IRS that you have hidden accounts.
Let's start by assuming that you, personally, have a furnace that can go up to 1350 oC (2462 oF), and a crucible that
can take the heat. You have build and run a bloomery just for the fun of it - just like Claes Vahlberg and his buddies and now you have some normal bloomery steel or wrought iron at your disposal. In other words, you have an
inhomogeneous mass of iron with an average carbon concentration of around 0.3 %, slag inclusions, and possibly some
phosphorous. This is now your starting material for making crucible steel.
Two thousand years ago some of our ancestors could muster about the same equipment and materials. But you, incontrast to your ancestors, also know all about the science and engineering of steel! You decide to use this knowledge
for turning your bloomery iron into good steel.
It is absolutely clear to you that you must melt the stuff. This is the only way to release all the entrapped slag andhomogenize the carbon concentration plus whatever else is in the iron. You might also purify the molten iron a bit, along
the lines used for copper purification or for making steel out of cast iron.

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Unfortunately your furnace is
not hot enough to melt your stuff.
What will you do?

You look a the iron-carbon phase diagram, of course. It will tell you what kinds of liquid you might be able to get atthe highest temperature your furnace can produce. Just look:

Making and Melting High-Carbon SteelObviously, you have to have at least about 2.1 % carbon in your steel if it is to melt at 1350 oC (2462 oF). If you
could only produce 1200 oC (2192 oF), the steel needs something between about 3.5 % - 5.2 % carbon - and it
wouldn't be steel anymore but cast iron. If you want only about 1 % carbon (not shown), you must go well above
1400 oC (1673 oF).
Now you know what you have to do. You need to supply just the right amount of carbon to raise the level from theaverage carbon concentration in your bloom (about 0.3 %) to at least the required minimum of 2.1 %. It's easy
enough to figure out how much carbon that will be per kg of bloom iron. So you take your (pieces of the) bloom, putthem into your crucible, add the proper amount of carbon, cover it with a lid (with a hole so gases can escape), andput the filled crucible in your furnace. Run it up to the maximum temperature, keep it there for the time it takes tohave a few beers with the boys, then let it cool down.
What you will find is a steel ingot snug in the bottom part, covered with a bit of slag. The slag comes from the slag
still contained in the bloom, and because you might dissolve some of your crucible material. At high temperatures
the slag will liquefy and sit on top of the far denser liquid steel, protecting it to some extent.
Now to your questions. The first, quite obviously, is:
1. Why should the bloomery iron liquefy? After all, its melting temperature is never reached.
Well - liquefaction occurs for the same reason that the ice in your driveway liquefies to water if you sprinkle salt
on it at temperatures below the freezing point of pure water but above the freezing point of salt-saturated water. A
little salt then diffuses into the solid ice, lowering its melting point, and small parts will eventually turn liquid. Thiscan happen already on a nanometer scale so not much diffusion or time is needed for the process. The liquid
dissolves the salt rapidly and at the solid-liquid boundary the salt keeps diffusing into the solid, turning it liquid.
The boundary area increases and the process accelerates. If you supply enough salt, all ice will eventually turninto liquid salt-enriched water.
Same thing with iron and carbon. It might take a while, but a few hours to a day should be enough for a crucible
charge of at best a few kilograms.
2. What should one use as a source of carbon?
Pure carbon = powdered charcoal, would be the obvious answer. Obvious, yes - but not what (most of) yourancestors did. The evidence points rather to the use of organic stuff like tree leaves or pomegranate peelings.
Whatever it is, during heating up all organic stuff will pyrolyze to carbon and gases that escape - provided you
make sure that no oxygen is around! That's one of reasons why you put a lid on your crucible (with a small hole
to allow the escape of gases produced inside), and why it makes sense to put the crucible in the reducing part ofyour furnace fire. All organic waste then is a source of carbon (and possibly a few other key elements).
The use of organic waste instead of charcoal now certainly triggers the third question:
3.
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3. Why? Why plant matter and not charcoals?
The answer is simple. I don't know. I can guess, however. Read on and you will find out what my guesses are.
4. The second-to-last question is also clear: Is there anything else besides bloomery iron and plant matter that you
like to put into your crucible?
The answer, as expected, is: it depends. If you have a little manganese-bearing stuff handy, it might be helpful. A
bit of glass or something to that effect might help in slag formation, especially if your bloomery iron is rather on
the slag-lean side.
5. A last question comes to mind: Are there any other ways to make crucible steel?
Yes there are - but not that many! You might, for example, mix wrought iron and cast iron in a relation that
produces the proper carbon concentration. You might use cast iron and take out some of the surplus carbon in
there by adding something oxidizing stuff like quicklime or even iron ore. Or you might use cast iron .... However,there was no cast iron in most places before, roughly, 1500 AD (with the exception of China).
Modern scientists and smiths have made crucible steel as described above; I will
get to that in due time. Here I only want to impress on you that making crucible
steel involves neither a secret nor is some magic required. It is rather straightforward. Precise recipes for the process have been published by several authors
from 400 AD onward.
There are a few documents that were written before 400 AD and allude to iron /steel in ways that could mean crucible steel from India. Maybe, but probably not.
More important than a few very vague early writings that may or may not allude to
crucible steel are the large amounts of early writings, in particular in India, thatnever mention crucible steel. We are justified in concluding that if crucible steel
existed before 300 AD or so, it was of no importance.

SpecialModuleEarly
Writings

So let's assume that (Indian) crucible steel appeared "on the market" around 300 AD. The first surviving good recipe
for making it dates to about 380 AD. It was written by one Zosimos (ca. 350 AD - ca. 420 AD), a kind of early
alchemist in Alexandria. Refer to the special module for details
The problem we have with ancient crucible steel from around 300 AD to 1700 AD is not to figure out how it wasmade but:
Figuring out from dug-up remains what, exactly, was going on when and where. This is not so easy because
not too many ancient places have been found, and not much is left there anyway.
Figuring out if some ancient (rusty) object was made from crucible steel or bloomery steel. Not too difficult if
you can destroy the piece - the rare exception. Quite difficult if you mustn't touch it - the normal case.
Figuring out how Eastern ancient smiths were able to work with the brittle high-carbon stuff in such a waythat high-quality products resulted.
Figuring out how some Eastern ancient smiths could produce blades with a "damascene" or "water" patternfrom some crucible steel, and what, exactly, made that steel different from crucible steel that did not allow
pattern formation.
Getting some solid data about the quality of crucible steel blades in comparison to other blades of the sametime period - and in comparison to blades made from modern steel.
Just for human interest, we might also want to know why the "West" never adopted the technology
considering that the information was available.
How good is (good) crucible steel? It is certainly better in one respect than run-of-the-mill bloomery steel. Since good
crucible steel was once molten, it is homogeneous on a macroscopic scale and free of slag or other inclusion. Thatmakes automatically for far better fracture toughness properties. That is the bright side of crucible steel.
As always there is also a dark side: Ancient crucible steel is always high-carbon steel and thus rather hard but perfectly
brittle, just like cast iron. In contrast to cast iron, however, it could be forged - with special skills, love, and tender care.
That allowed to make useful objects like razor blades, surgical instruments, or files. For those products extreme
hardness is good (e.g. for making very sharp edges that stayed sharp) and the still large degree of brittleness istolerable because these objects were not exposed to high-energy impacts like swords.
One also could make crucible-steel swords with very hard and sharp blades that could be bend without fracturing tosome large degree. Thise swords, however, were still rather brittle since the grains were encased in cementite as shown
here, and possibly cold-short since crucible steel like any early steel often contained phosphorous with all theconcomitant problems. But then there are also what I will call "wootz" swords, showing a water pattern on theire
surfaces. This pattern is due to "spheroidized" cementite, made in rather tricky ways (just wait), that gives someductility to the steel.
Looking into these points in some detail will be a substantial amount of work. Let's start with the when and where .

Extremely Short History of Early Crucible SteelIron, Steel and Swords script - Page 374

What do we know about the early history of crucible steel? We have essentially three sources we can exploit:
1. The remains from ancient places where crucible steel was made. This needs finding these places, digging up
some artifacts, and figuring out what those artifacts can tell us about the making of crucible steel.
2. Very old objects, in particular swords and armor, that have been made from crucible steel. We need to analyze
these objects and conclude from the results to the making of the crucible steel and the way the steel was forged
into the object.
3. Whatever ancient authors wrote about crucible steel.
Nothing here is straight forward. Ancient crucible steel workshops or "factories" do not leave much behind that can beeasily recognized after thousand-plus years, just like bloomeries. What you find needs to be analyzed and interpreted,
and interpretations might be ambiguous or simply wrong. Very old swords of any kind are usually not available for close(and thus destructive) analysis. In the rare cases where this was possible, the results of an analysis do not tell you
exactly how that sword was made. As far as written accounts go, we know already that we shouldn't expect too muchfrom this module.
Let's start with the evidence from dug-up crucible steel work shops.
There is one thing we know for sure about crucible steel work shops: we haven't yet discovered most of them. Until
about 20 years ago, the only known early places for crucible steel were in Sri Lanka and South India. Anna Feuerbach(plus many others), put the Merv area in present Turkmenistan on the "crucible steel" map, in particular in her(unpublished but available) PhD thesis work (2002 Univ London) and in later publications 1). Meanwhile we also have
Akhsiket in Uzbekistan 2) and a few places in (South) India 3).
However, the crucible steel workshops in Central Asia that were dug up and investigated by an international team dateto the early Islamic period, i.e. the late 9th - early 10th century AD. That is, maybe, still "early" but not very early. Anna
Feuerbach, however, has reasons to believe that crucible steel technology in Central Asia goes back at least 500 more
years.
The map below shows the known early places (plus Damascus) and makes clear that there is definitely a lot of room for
more finds.

Known Places where Crucible Steel was made inearly times

I emphasize "early places " here because crucible steel has been made for a long time - from at least 300 AD up to
the 19th century in India and Central Asia. Of course we know a lot more about later places than about the moreinteresting early places.
Contrariwise, there is presently no evidence at all that crucible steel has been made in Damascus / Syria or, moregenerally, in what one might call the "Arabic" countries, not to mention the "West" at large. There are a few written
hints that some crucible steel was made in Syria and Egypt but nothing has been found yet. On the other hand weknow for sure that "India" exported crucible steel on a large scale to the Arabic / Muslim countries for 1000 years or
more.
Once more, this doesn't mean that the "Arabs" didn't know how to make crucible steel (or bloomery iron / steel). It
just was easier and cheaper to import the stuff - considering that the Arabian peninsula, Egypt, and so on had
neither much iron ore nor much wood for charcoal on their territories. India, in contrast, had plenty of both. In North
Germany we do import our wine even so we know how to make (and drink) it.

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If one digs up an old crucible steel work shop one tends to find parts of used crucibles, remains of furnaces, and a bit ofslag. The very few iron / steel objects left over only exist as rust or small "prills" embedded in the slag or sticking to
crucible shards. To the best of my knowledge, no good ancient "wootz cake" or "pulad egg" (I'll get to that) has everbeen found so far. Dating the finds is difficult, and interpreting what they mean not always easy. For example many
crucibles dating to 300 BC - 300 AD have been found in Kodumanal in India. These crucibles may or may not have beenused for making crucible steel. You also need crucibles for the much older techniques of melting and casting copper,
bronze and gold. Crucible remains from other (Indian) places definitely have been used for making steel (they might, forexample, be encrusted with steel prills) but no dating was possible.
In other words, we are a far cry from knowing who, where and when made the first crucible steel. We do know, however,that whoever did it, had to be able to run a bloomery and to make some pretty good ceramics, far more heat resistant
than the normal pottery of those days. In addition they needed a furnace or kiln that could produce very hightemperatures for many hours in a reducing environment. Moreover, without a good knowledge of forging technologies,
crucible steel would have been of little value.
All things considered, crucible steel could have been made as early as 500
BC or so - it's just not likely. If so - and personally I'm not convinced of that - iteither was a small-scale operation or we have not yet found major centers.
What we need to bear in mind is that almost anything that is known orassumed to be known about crucible steel and the swords made from it
comes from around 300 AD or later, much later in fact. We simply do no knowmuch about very early (= before 300 AD) crucible steel making at present.
There are good reasons to believe that there might not have no been any. To
quote Bennet Bronson , whose 1986 paper 4) in my opinion still sets thestandards:

SpecialModuleLate Writings"We have no indications that crucibles were used in steel making
before the late first millennium AD, and we have no real reason tothink that they were used in India as early as that"

The famous iron pillar from around 400 AD, by the way, was made from bloomery iron. That was the only way since
the high-carbon crucible steel cannot be hammer welded, it is said.
What we do know about crucible steel and most of the mythology surrounding it and those "true damascene
swords" comes from its "late" history (after 1700 AD, say). The special module gives a short account of the late(and very confused) history of crucible steel.
No let's look at old artifacts. For old steel artifacts, in particular swords, a detailed metallographic analysis can give
clear indications if the object was made from bloomery or crucible steel. Crucible steel is free of slag, inclusions ofwhich are always found in bloomery steel. Early crucible steel should always be hypereutectoid high-carbon steel, andthus contains a lot of cementite in one form or other. The concentration of carbon and other elements is rather uniform
throughout the material, in contrast to bloomery steel.
Anna Feuerbach has analyzed a number of old blades and reported the results in her 2002 PhD thesis and in apaper from 2005 1). She found a few blades that have been made from crucible steel: "One of these blades (from3rd–4th century A.D. burials in the Russian Northern Caucasus) has aligned spheroidal cementite, themetallographic feature that produces the visible pattern. This is the earliest known crucible Damascus blade". If weassume that Anna is right, crucible steel and the forging technology going with it must have existed at least as earlyas 300 AD; a date we are familiar with by now.
More recently, Sharada Srinivasan, an Indian authority on crucible steel,reported on metallographic investigation of a (heavily corroded) ring (seepicture) form the South Indian site of Kadebakele, securely dated to to 800 BC– 440 BC. It is: "one of the earliest known examples of pearlitic or higher
carbon steel found anywhere in the world. The structure is not inconsistent
with that found in the crucible fragment from Mel-siruvalur, which is confirmed
to be from high carbon crucible steel production" 3).
That is certainly true but the structure is not inconsistent with high-carbon
bloomery steel either, something that ancient smiths could turn into smallthings like rings on occasion. Other iron artifacts from the same place andtime were definitely bloomery iron, says Sharada.

Iron, Steel and Swords script - Page 376

As far as early authors go, I already mentioned that above. There are no definite statements from the time before theAlexandrian historian Zosimos wrote a detailed description of crucible steel production during the 3rd century AD. He
stated that it was being used in India and Persia. This would date crucible steel making to at least 300 AD once more.
Just to give a taste of what else is around: Alexander the Great reportedly received some special "white" steel from
Indian rulers in 326 BC. This could have been crucible steel, putting the date of its first making before 350 BC or so - but
this is just guessing. More to that in this module.
What emerges once more is that the making of crucible steel might go back to about 500 BC but that there is noincontrovertible evidence for that. We know that bloomeries could produce cast iron and thus also high carbon steel.
Mrs. Srinivasan's ring thus might have been made from a high-carbon steel piece that was produced in a bloomery.
Whatever. If people actually made crucible steel before about 300 AD is doubtful, and even it they did we can simply
ignore it at present for lack of data.
While the basic technique for making crucible steel never changed, we can be sure that the technology developed andthat late processes were far more advanced and better controlled than the early ones. We do know this, actually. Many
Westerners have seen crucible steel being made in India between 1795 and 1900. Some wrote about that and we still
have about 20 written eyewitness accounts, some from people with a scientific training or a deep knowledge about ironand steel. Look at the "Late History" module for some more details
The "West", however, never caught on, and never made crucible steel of its own (with the exception of the Russiansin the first half of the 19th century). Benjamin Huntsman; if you wonder about that statement, just melted steel incrucibles in the 18th century; he didn't add carbon.
This is a puzzle of sorts. Overfunded spy organizations like the CIA or NSA are rather recent inventions but it isnevertheless not likely that nobody was able to steal the secret recipes, in particular because they weren't all that
secret to start with. Plenty of written recipes were open to all that could read since 300 AD and certain ways forgetting a working recipe would have worked just as well then, as getting big sports events to Qatar now, forexample.
As always, it might have been plain old stupidity or religious / social bias (same thing anyway) that kept crucible
steel making out of Western Europe. That attitude keeps equal rights for females out of many countries at present,
for example. But, maybe, the real reason was that Western steel and Western swords were just as good as their
Eastern crucible-steel counterparts. The Crusaders, after all, fought their way deep into the lands of crucible steel
swords late in the 11th century and most of the 12th century with their bloomery steel swords, while the other side
never quite made it into Northern Europe - and they sure tried for many centuries!
Some Points about Making Crucible SteelFirst of all you need a crucible that can take the heat, at least 1350 oC (2462 oF) and higher is better! You can't makeit from "regular" clay because your crucible then would start to melt around 1200 oC (2192 oF). So use "special" clay
and strengthen it with roughly equal amounts of (silicon dioxide rich) rice chaff. Or find some other way, e.g. by using"China clay" or stuff containing a lot of aluminum oxide.
Different cultures at different times found different solutions. The Sri Lanka / Indian crucibles, for example are quite black
whereas the Central Asia stuff is rather on the white side - like modern porcelain.
I don't want to belittle crucible technology. It is absolutely crucial to the development of metallurgy, and much could besaid about it. It's just just not crucial to the topics here. If you can make one that can take the heat, you can makecrucible steel. If you can't, forget it. The schematic drawing shows what old crucibles looked like in almost natural size.

Iron, Steel and Swords script - Page 377

Crucibles. Left, the larger but thin-walled Central
Asia kind; right the smaller and older Indian variety
Source: Redrawn from Rehrer's paper 2)

Second, you need a furnace that can produce at least 1350 oC (2462 oF). You can easily get that kind of temperature
close to the tuyere of a well-constructed and vigorously blown bloomery but here you need to heat a crucible inside akind of kiln. That is not so easy to do.
In Merv some remains of kilns from around 900 AD have been found. They were rather advanced constructions, certainly
outperforming their counterparts from 500 BC or 100 AD. Several crucibles were put in a bed of charcoal inside a domed
kiln and a lot of air was blown in from below.
But nothing helps. If you want to make crucible steel with at most 2 % carbon, possibly a bit less, you must keep
up a temperature of at least 1350 oC for hours and within a not too small area. One might speculate what you might
get at lower temperatures, where you find yourself inside the "γ + liquid" phase field. There you have a mixture ofcarbon-lean solid austenite and a carbon-rich liquid. This probably has happened a lot, and than you get "bad"crucible steel that is rather inhomogeneous.

Third, you need some bloomery iron and a source of carbon. For the latter you might use those magic plants theshaman recommended or just about any organic waste. Some plants might work better than others because they might
supply a bit more of "good" trace elements but we do not know much about that. The decisive point is to add just theright amount of organic matter. Since even you, the modern crucible steel maker, do not know the precise amount ofcarbon contained in your bloomery iron and also not exactly how much carbon will remain from the plants after
pyrolyzing (some of the carbon will escape as CO2 or CO), this is simply a matter of trial and error, culminating
eventually in a working recipe.
Your iron needs to be crushed into suitable lumps. Note that for an "ideal" crucible steel process, you may want to haveyour iron more or less as dust or powder - but that is not something easily done with ancient technology.
For added value, you might also want to add a bit of "flux". It should be the right kind and the right amount, of course.
Some manganese containing stuff would be good since a bit of manganese in your steel is always beneficial.
Then you might consider how to stack the stuff inside your crucible. Iron - flux - leaves? The other way around? Several
layers in succession? There is no obvious good reason why this should matter but it is an issue with modern crucible
steel makers.
Now put a lid on and maybe secure it by smearing some clay around the rim. Or seal your crucible in some other way.
You need to do this for the reason mentioned above and for simply keeping stuff from falling in. You might want to put a
Iron, Steel and Swords script - Page 378

small hole in the lid, though, because gases will develop with your particular mixture for almost sure. You should allow
them to escape lest they blow up your crucible.
So why organic matter and not charcoal? My guess is that the decomposition of the organic stuff at hightemperatures releases hydrogen (H2) and carbon monoxide (CO) among other stuff, gases that will not only preventthe oxidation of the iron but remove the oxides already there. The carbon produced by pyrolysis of leaves etc. will
also be a fine dust that can more easily coat the iron and penetrate it than lumps of charcoal. The ash produced
might help in slag formation.
But that's only a guess. There are reports that in more modern times charcoal was actually used as a source ofcarbon. If done just right there shouldn't be a problem.
All you need to do next is to stew your charge for a while - several hours, maybe a day or two, and then let it cool down.
You have two options for that:
1. Cool down quickly, including taking the crucible out of the kiln and using some violent cooling procedure.
2. Cool it down slowly.
It appears that the early Indian crucible steel makers preferred the first possibility, and the later Central Asia people thesecond. I'm not aware of solid evidence for that, however.

Backbone
Link
Easy
Segregation

This is a rather important issue since the cooling speed
determines the general microstructure obtained at room
temperature, including in particular the amount of macroand microsegregation of whatever impurities arecontained in the iron. If a "water" pattern can be formedin swords forged from the steel, and what it will look like,is possibly determined by this structure.
I will come back to this in detail, meanwhile it would be agood idea for you to read up on those topics a bit.
Go ahead, Give it a try. Don't drink beer. Have your girlfriend support you if necessary.

Science Link
Segregation
Science

Sorry about that but it's good to have you back.
Now you can remove your crucible steel from the crucible (which you have to destroy in the process). You will haveproduced either
a wootz cake if you feel attached to the modern English tradition, ora bulad egg if you use the more ancient names for naming the ingot"Cake" or "egg" refer to the shapes of your ingot, determined mostly by the shape of the crucible bottom. Since we haveneither old wootz cakes nor bulad eggs, these names do not tell us a thing about the (average) properties of "raw"ancient crucible steel.
The somewhat unusual identifier "wootz " was and still is the commonly accepted name for crucible steel in theWest. Lengthy papers have been written about its origin. "Wootz", writes Sharada Srinivasan in 2009 3), "is thought
to be a European corruption of the south Indian Telegu/Kannada word for steel, ukku". Ukku may derive from therelated Tamil word uruku, meaning to make molten. It could also be related to ekku, the old Tamil word for
sharpness/ sharp spear. And so on.
As far as I'm concerned one needs to imbibe a lot of beer before one is able to pronounce "ukku" like "wootz".
Maybe the British just didn't want to be outdone by the French in the art of mispronouncing foreign words.
Pulad, Fuladh, Bulat, Bolat and so on simply is the (much older) term for "wootz" in most "non-Western" countries.
It is also the word used by the old writers like Al-Kindi and Al-Biruni Maybe it relates to the Persian word "pulad" =steel. Or to some other words in some other languages.
While I'm at it: Damascene or damask, one of the many names for blades with a "water" pattern, could mean
coming from the city Damascus, the capital of present Syria, that a smith named "Damasqui" has made the sword,or from the Arabic word damas = water.
Iron, Steel and Swords script - Page 379

The point is that both words are a bit ambiguous. They do not always mean just "crucible steel". The term "wootz
sword", for example, denotes only a sword with a visible "water" or "damask" pattern. While all "water -patterned"
swords were made from a wootz cake or bulad egg, there are crucible-steel swords without that pattern.
And now we finally can ask the most difficult question in the context of crucible steel:What, exactly, is the difference between wootz cakes / pulad eggs
that can or cannot produce a "water" pattern on a blade?

That is the question. It is a tricky question because an ancient blade with a water pattern unambiguously proves that its
maker could manipulate his wootz / pulad in a way that produced the pattern. One might speculate if somebody
somewhere and sometime was able to produce a "water"-patterned blade from a steel that was not a crucible steel? The
answer seems to be no - as long as we do not look at modern 20th century steels. I will get back to this topic in asomewhat different context later.
Blades without a water pattern, however, do not prove anything directly. There could be several reasons for the lack of awell developed "water" pattern:
1. The blade did show a pattern but somebody polished it, erasing all traces of the original pattern. Museum people
like to do this.
2. The wootz / pulad would have allowed to produce a pattern but the smith chose to forge the blade in such a waythat no pattern could develop. While the "water pattern" was highly priced in some cultures, others (including, forexample, on occasion the Indians who made the steel) liked their blades shiny even after etching.
3. The wootz / pulad would have allowed to produce a pattern but the smith didn't know how to forge it in such a waythat the pattern could develop.
4. The blade is from wootz / pulad steel and actually does show a pattern - it is just too fine to be seen by the"naked" eye.
5. The wootz / pulad does not allow to produce a pattern, no matter how it is forged. This happens "automatically" if
we have a "low-carbon" crucible steel - but I'm not sure if such a thing ever existed. We look at high carbon wootz/ pulad here.
Let's make clear what I mean with "water" pattern. It means a special kind of a layered distribution of cementite
particles in the steel because, after some etching, a nice pattern visible to the naked eye is produced. If, bycontrast, the unavoidable cementite particles are distributed uniformly, there is no nice pattern; at best the blade
looks slightly mottled. I will go into this in far more detail in the next chapter.
Just to make sure we understand each other, here is a picture illustrating a few quick points about patterns on a
blade:

Three blades with a pattern. The contrast is strongly
enhanced.

Iron, Steel and Swords script - Page 380

The left part shows the "water" pattern of parts of a "wootz" blade. People gave it many names and I don't care how
you like to call it - true damascene, perhaps. Important is only that the pattern results from an inhomogeneous
distribution of cementite particles. You do not see the individual cementite particles but their arrangement in the
fuzzy white bands.
On the right is the center of a (modern) pattern-welded blade. Two kinds of steel are involved here. One that appears
bright after etching, and one that appears dark.
The center shows a Japanese blade with a distinct "hamum". The blade actually consists of at least two kinds ofsteel but you see only one. The pattern is due to a different microstructure of one kind of steel. The bright parts aremostly martensite whereas the darker parts are bainite / pearlite.
I do not show a fourth variety; bands of pearlite grains separated by ferrite grains. This is observed in modern steels(with a microscope) and Anna Feuerbach mentions it in her thesis as a possible "wootz" pattern. I have yet to see
this in an old steel, so there is no picture.
Finally we are at the heart of all the excitement and emotions about "wootz" steel and blades. The tough questions toaddress now are:
Does it need something special so that some wootz cakes / bulad eggs allow to produce a nuce water pattern?
If yes, what exactly is it?
Alternatively: is the pattern produced by a special way of forging? Could a cunning smith persuade any highcarbon steel to produce a pattern?
Is a blade with a nice water pattern always better than one without it? If yes - why?
I'm talking more and more about sword blades now. Since this is the topic of the next and final chapter, I will stop
right here and go on with a quick look at modern ways to reproduce crucible steel and use it for blades.

1)

Anna Maria Feuerbach: PhD thesis work (2002 Univ London; Inst. Archaeology)
Ann Feuerbach: "PRODUCTION AND TRADE OF CRUCIBLE STEEL IN CENTRAL ASIA", Indian Journal of History of
Science, 42.3 (2007) 319-336;
A. Feuerbach, D.R. Griffiths, and J.F. Merkel, “Crucible Steel Manufacturing at Merv,” Mining and Metal Production
through the Ages", ed. P. Craddock and J. Lang (London: British Museum, 2003), pp. 258– 266.
Ann Feuerbach: "An investigation of the varied technology found in swords, sabres and blades from the Russian Northern
Caucasus"; iams 25 for 2005, p. 27-43 (Institute for Archaeo-Metallurgical Studies Newsletter).

2)

Thilo Rehren: "As similar as black and white: steelmaking crucibles from South and Central Asia"; Archaeology
International, open access, 23 October 2002, p. 37.

3)

Sharada Srinivasan, Carla M. Sinopoli, Kathleen D. Morrison, Rangaiah Gopal and Srinivasa Ranganathan: "South Indian
Iron Age iron and high carbon steel: with reference to Kadebakele and comparative insights from Mel-siruvalur", in:"Metallurgy and Civilisation: Eurasia and Beyond" Archetype, London 2009, ed. J. Mei and Th. Rehren.

4)

Bennet Bronson: The making and selling of wootz, a crucible streel of India", Archeomaterials, Vol1, No. 1 (1986) p. 13 51.

Iron, Steel and Swords script - Page 381

10.4.2 Making Old-Fashioned Crucible Steel in Modern Times
Old and New
After the advent of the blast furnace around - roughly - 1500, the cast iron produced was the raw material for making
steel. Since it was liquid once, the steel produced from it was rather homogeneous and without slag inclusions, just likecrucible steel. Producing steel from cast iron happens by taking some of the surplus carbon out. In theory you can stoptaking carbon out as soon as you have reached the concentration you want. It is not an easy thing to do in practice but
it has been done. Stopping the carbon reducing process early produces ultra-high carbon steel (UHCS) but nobody, it
appears, made that kind of stuff during the middle ages. The fact that it wasn't done most likely means that nobody
wanted it done.
Objects like swords made from cast-iron derived normal steel were still made by forging. Casting steel started wth
Huntsman around 1750 on a small scale but only came into its own - roughly - around 1850. Cast steel is by definition
crucible steel in the sense that it was liquid once, and that its carbon content was established while the steel was
liquid. Once more it would have been no problem to make ultra-high carbon steel (UHCS) and thus a facsimile of ancientcrucible steel, and once more, nobody made some. UHCS was not in large demand then, nor is it now.
Why? Why did the "West" not appreciate UHCS, considering that is is a very hard steel? To answer in the words of
J. Oleg D. Sherby, one of the researchers who worked most of his life on the topic: "Ultrahigh carbon steels (1.0 to
2.1%C), now designated as UHCS, have been viewed for most of this (20th) century as belonging in the “no man's
land of carbon steels” being sandwiched between the extensively-utilized high carbon steels (0.6 to 1.0%C) and themass-produced cast irons (2.1 to 4.3%C).
Ultrahigh carbon steels’ position in the “no man’s land of carbon steels” is because UHCS have been considered to
be brittle at room temperature and thus have been generally ignored commercially. The origin of this belief can betraced to the classic work of Howe, published in 1891, in which the tensile ductility of steel was studied as afunction of carbon content."
Here is the classical curve of Howe, augmented by the new data of Sherby and colleagues:

Elongation vs. carbon content for carbon steel;(data collected by Henri Howe, 1891)
and modern data for 1.8 %C UHCS
SourceGood old Howe, whoever he was, thus pronounced UHCS to be useless - but not lightly. He had a hell of a lot ofdata points as you can see. However, all his data points were from UHCS where the grains were completely
enclosed in a brittle cementite shell and that cannot but render the composite brittle, too. I have dealt with that
extensively before.
What you can do to alter that deplorable state of being is to break up the cementite. Disperse it in the form of small
lumps in a continuous or contiguous matrix of ferrite, and you should have some ductility. You know by now, I takeit, that for UHCS the phase diagram predicts a mixture of ferrite and cementite. It only remains to produce thismixture by having cementite particles in a ferrite matrix instead of having pearlite grains encased in additional
cementite lining the grain boundaries.
How could one produce a "nice" ferrite / cementite mixture that is stable at room temperature? Sort of little spheres of
cementite embedded in a continous matrix. A "spheroidization of the cementite", in other words, is what you want.
There are three major ways to get this:
1. Anneal at very high temperature for a long time. Since cementite, like all precipitates, likes to minimize theinterphase area, it tends to do this by balling up, forming spheres. Give the atoms enough opportunity to movearound, meaning enough time and temperature, and this will always happen. Of course, above the A1
temperature of 727 oC (1341 oF) you only work with the primary cementite but that is the "bad" one at the grainboundaries.
2. Break up the cementite with a hammer or by any other means of deformation You best do this below the A1
temperature to get all the cementite. At higher temperatures (where smithing typically occurs) cementite also
Iron, Steel and Swords script - Page 382

2.
ceases to be brittle and then won't break. What broken cementite looks like you can see here.
3. Forming spherical carbides by employing the "divorced eutectoid transformation" or DET.
The first possibility is not very attractive - high temperatures and time equals money. Moreover, while making
spherical particles or spheroids of cementite is advantageous for the crystal in terms of energy, making plain carbon(graphite) is even better. If you overdo it, you might end up with a structure akin to white cast iron; totally useless formaking swords.
In fact, one of the first modern publications dealing analytically with wootz steel and swords, the remarkable 1962
paper "Damascus Steel in Legend and Reality" by Carlo Panseri 1), does report that 0.3 % of the 1.42 % total
carbon in a magnificent wootz blade was present in graphite form.
The second treatment will always happen if a sword is forged - provided the smith keeps the temperature low. It thenis more or less mixed up with thethird way: inducing a divorced eutectoid transformation.
Combining all three treatments in a smart way will produce "Damascus steel, defined as a hypereutectoid
ferrocarbon alloy, with partially and heterogeneously spheroidized cementites, having a carbon content normallyrunning between 1.2 and 1.8 percent." 1). Panseri knew his stuff. I just needed to strike out the "heterogeneously"
because that is not yet there.
"How do you divorce an eutectoid transformation?" you might now ask. "I wonder if I even want to know about it. My own
divorce was messy enough, after all", would also be a perfectly normal reaction. Well - don't worry, or at least not too
much. There was no divorce; the term only means that there wasn't any cooperation either between the cementite andthe ferrite when both were formed from austenite.
A picture says more then thousand words:

Cooperative and divorced transformation fromaustenite to ferrite and cementite
In the normal cooperativemode, ferrite and cementite form together as shown and discussed before. The result isthe famous pearlite "zebra" structure as seen upon etching in pretty much all metals that underwent an eutectic /eutectoid transformation during cooling. With increasing cooling rates the distance between the lamellae getssmaller because the diffusion lengths decreases. If you cool too fast at "normal" carbon levels, you first start toproduce bainite , no longer with a clearly defined zebra structure, and finally martensite. You would be justified incalling the formation of bainite a "DET", too; some people actually do this.
However, if we look at UHCS, a divorced transformation ideally produces spheroidized cementite particles in a ferrite
matrix, just as shown above.
What does it take to produce a nice DET structure? Either a lot of luck and cunning or a very good understanding ofwhat is going on. In essence it boils down to:
Annealing at high temperatures for a sufficiently long time span. But not just any high temperature. You have tobe pretty close to A1 or it won't work. Complications may come from the fact that other elements in your steel
may change A1 somewhat.
Cycling for long times (like 2 days) from just above to just below A 1 may work even better.
And so on.
But you need nuclei to act as starters for the large cementite spheres you want to have in the room temperature
ferrite. These nuclei need to be present already in the austenite.
The only problem remaining is to supply those nuclei. They must be very small cementite particles because in ourhypereutectoid steel we can only dissolve about 0.7 % carbon close to A1, and the rest must exist as cementite.
We can produce these nuclei by doing whatever is needed, essentially annealing at high temperatures. If these
nuclei are randomly distributed, we will have a random distribution of the large cementite particles found later in theferrite; if not, not.
We are inching towards pattern formation here!
That all this works is shown here:

Iron, Steel and Swords script - Page 383

SEM picture of fully and partially spheroidized UHCS
Source O. D. Sherby, J. Wadsworth, 1997

On the left we have fully spheroidized cementite in a UHCS-1.8 %C sample. The treatment included tempering
around A1 and deformation by hot rolling. On the right hand side the sample has been annealed for a while at 840
oC, i.e. well in the austenite region, and the "zebra" pearlite now starts to form again during cooling. It goes without
saying that spheroidized UHCS is no longer brittle but has some ductility; the red data points in the picture on top
are from samples like the ones shown here.
Would there be a difference between a modern UHCS and an antique wootz cake or bulad egg? Both are very hard butwith some ductility left.
Well, yes, of course. The modern "crucible" UHCS would contain some defined amounts of manganese, silicon, andsome unspecified and possibly unknown traces of this and that - but no appreciable amount of phosphorous. It would
also be rather uniform throughout.
The bulad egg would contain more or less random amounts of this and that, including possibly some (beneficial)manganese but quite possibly also some phosphorous. Moreover, it could be a "bad egg" if it was not completely
molten but only partially. Then it was only a mix of a carbon rich liquid and some solid and relatively carbon-leanaustenite, look at the phase diagram. It wasn't very uniform either in this case.
So what is better? It is not impossible that some UHSC containing some undefined impurities would be better withrespect to basic mechanical properties in comparison to a well-defined modern UHSC that contains only what was put
into it. It is not impossible - just very unlikely.
So is there anything that wootz can do that a modern UHSC cannot?
Well - maybe the ability to arrange the spheroidized cementite particles in such a way that they form a nice pattern,
the famous "water" or "damascus" pattern, is special? Good question, just a bit stupid. We know of course thatsome wootz cakes or bulad eggs do offer that possibility - there are swords with the "water" pattern, after all. The
real question is

Can you make a water patternfrom any modern UHSC?

That is "the" question. The answer isn't in yet. Some people looking into the issue say "yes", some say "no".
Searching for the answer proceeds like in the old days: the champions of the two factions fight it out in a jousting
tournament:

Iron, Steel and Swords script - Page 384

The Great Verhoeven - Wadsworth Jousting Tournament
There is no shortage of people who have addressed the issue. Two guys, however, have not only addressed the issues
but started a veritable jousting tournament, taking stabs at each other (with pens) in turn. I'm referring, of course, inalphabetical order to John. D. Verhoeven and Jeffrey Wadsworth and the men-at-arms who go along with them.
John D. Verhoeven is a distinguished Emeritus Professor of Materials Scienceand Engineering, College of Engineering of Iowa State University. He worked inareas like electrotransport, thermotransport and convection in liquid metals,
directional solidification, superconductivity, cast irons, steels and Damascus Steelin his capacity as Professor at Iowa State; publishing a lot of papers.
Jeffrey Wadsworth we have met before. He is President and CEO of Battelle
Memorial Institute since January 2009. Before that he was the deputy director for
science and technology at Lawrence Livermore National Laboratory, the manager ofthe Metallurgy Department at the Lockheed Research and Development Division of
Lockheed Missiles & Space Company Inc. and affiliated with Stanford University.
He has authored or co-authored more than 260 papers on a wide range of materials
science and metallurgical topics, too

SpecialModuleThe
Tournament

These guys are heavyweights and their jousting is fun to watch from the sideline. They both are limping a bit after 26
years of stabbing at each other (with pens), but none has yielded yet and both seem to be still capable to mount ahorse and charge. Here is (simplified) what the fight is all about
Wadsworth champions the: Yes - you can make a nice water pattern from any old or modern ultra-high carbon
steel (UHSC). The cementite forming the pattern is essentially the cementite you had in your steel before forging.
Verhoeven goes for the No you can't" option. You need special UHCS with traces of special impurities likevanadium (V) to nucleate cementite in new structures that are quite different from the ones in the steel before
forging.
Mind you, the tousle is not about if you can or cannot make a pattern with any modern UHSC steel. It is about:

Can you make a nice water patternfrom modern UHSC?
The emphasize is on "nice" because you can definitely get some pattern with any modern high-carbon steel. Verhoeven
claims that you only get a "nice" pattern (he calls it, for example, "museum-quality" as opposed to "granular") if theoriginal steel contained some carbide-forming trace impurities like vanadium (V) or molybdenum (Mo) that become
distributed inhomogenously due to dendrite formation during solidification. More about pattern appreciation in thismodule.
So who is right? I'll tell you if you send me some money in unmarked large bills. Or maybe in the next chapter. Until
then use the link above and enjoy the tournament.
Making Crucible Steel the Old-Fashioned Way
There seem to be very few old wootz cakes / bulat eggs around, and whatever there is cannot be used forexperimenting. So let's make some, following the old recipes as far as we can. Maybe with a few shortcuts in the
beginning. You don't need to build a kiln and burn charcoal anymore to get the temperature up - we have electricity forthat. But that doesn't matter. Whatever is in the crucible doesn't care how it is made hot. It might care if the atmosphereis oxidizing or reducing, though.
Verhoeven began a unique collaboration with master blade-smith Alfred H. Pendray in 1988. The idea was to prove
his point by recreating blades just as nice as the ones we admire in museum from crucible steel made for thispurpose. Pendray was infected by the scientific spirit and charged his crucible with high purity stuff and deep
thoughts about the rest.
Richard (Ric) Furrer, however, did his crucible experiments under the influence of beer. Both guys produced
crucible steel from which blades could be forged. Here are their recipes:

Iron, Steel and Swords script - Page 385

SmithAlfed H. Pendray

Richard Furrer

Iron source 1. High-purity iron
2. Sorel iron(high-purity iron with acarbon concentration
around 4 %; i.e. highpurity cast iron).

1. Iron powder(presumably highpurity)2. Cast iron

Carbonsource

1. Sorel iron
2. Charcoal
3. Special green leaves

1. Cast iron
2. Dandelions fromthe backyard

Slagformer

1. Glass shards
2. Additional
unspecified ingredients

Freshly crushed
green glass(from beer bottles)

Process / Melt iron,
Philosophy liquid glass (=slag) ison top and protects
steel. Leaves producehydrogen (H) that helps
carburization
Without leaves andglass the finished ingot
tends to be brittle

Seal crucible airtight
Heat for about 3
hours.
Don't worry, havesome beer with theguys,
cool slowly

ResultIn both cases the relative amounts of carbon
source and pure iron determine the carbon
concentration in the final product.

Alfed H. Pendray is a blacksmith and the former President of the American Knifemaker's Guild. Not only is he anexpert on "wootz" steel but as a farrier has shoed some of the most famous (and valuable) thoroughbred race
horses in the world. He has worked together for more than 20 years with John D. Verhoeven.
Richard Furrer started as a black smith and is now running the "Door County Forgeworks". He is an internationallyrenowned expert for ancient metallurgy who works with scientists from several universities and teaches classes
there.
Both produce wootz cakes of quality, and both can make blades with a definite water pattern:

Water pattern on modern wootz blades
Left: Furrer school; Right: Pendray's work
Source: Left: From the Internet pages of the Furrer disciple Owen
Bush; who made a wootz blade in Furrer's smithy. Right: Pendray's
work as published here

Pendray's piece show a "Mohammed's ladder with roses" pattern, the most complex pattern made in the old days.

Iron, Steel and Swords script - Page 386

Incidentally, Pendray confirms what I suspected some time ago: Organic matter as a source of carbon might beadvantageous because it also supplies gases like hydrogen, helping the process.
Meanwhile several smiths produce modern wootz blades with a pattern. You find an example in Calabrés paper, bylooking for the work of a Russian smith named Mr. Ivan Kirpichev, or by looking at the work of Eric M. Taleff 3, a
researcher who coauthored several papers with Wadsworth and Sherby. Or just search the Net, you will find more.

A genuine wootz pattern (not pattern welded)
according to Taleff 3)
SourceBut are those modern patterns "nice " patterns? The one above might qualify, I believe, even so it is not traditional.
But that is a touchy topic since it is a matter of taste and it is hard to define where "nice" ends and "inferior" starts.
From what I have seen, Pendray's blades take the price. So far he seems to be the only one who recreated the"ladder and rose" pattern as shown above. Verhoeven attributes this to traces of vanadium that are contained in the
Sorel iron used (without knowing this) for the making of the wootz. This might well be true and the question now is:

Why are traces of vanadium(or molybdenum, or .... )necessary for making nice pattern?
I'll look into this in the next chapter where I finally will get to swords

1)

Carlo Panseri: "Damascus Steel in Legend and Reality" reprinted in Gladius, IV (1965), pp. 5-66; originally published in
ARMI ANTICHE, Bulletin of the Accademia di Marclano, Turin, sole number for 1962, and translated to English by H.
Bartlett Wells. Washington DC, in 1965

2)

Rafael Calabrés et al.: "Traditional Forging of Swords and Knives with Legitimate Damascus Steel", Prakt. Metallogr. 38/6
2001 . p. 325 - 337(Note the "Legitimate")3)

Eric M. Taleff: "Microstructural Characterization of a Knife with Damask Patterning", Technical Report, Internet
Taleff investigated a "blade created from a commercial tool steel using a combination of thermal and mechanicalprocessing steps." His conclusion concerning the pattern shown above is: "The knife blade examined clearly falls into thecategory of a genuine damascus steel. The damask pattern it exhibits results from microstructural bands in the
distribution of very fine carbide particles."Iron, Steel and Swords script - Page 387

10. 5. Iron and Steel in "Modern" Europe

10.5.1 From Bloomeries to the Blast Furnace
Changes Over Time - a General View
In the preceding subchapters I covered the early history of iron and steel in some detail: from the beginning to about
Roman times in Europe, or up to - roughly - 400 AD. Other parts of the world were mostly neglected with the exceptionof a short entry for China, and a not-so-short subchapter about crucible steel in India and parts of Asia.
There was no iron and steel in the Americas and Australia before the "white man" brought it along, so there isnothing to tell. Africa, however, does have a "modern" iron and steel history; I deal with it - shortly - here. Whatfollows is heavily biased towards (Northern) Europe.
So what has happened with respect to iron an steel development between - roughly - 400 AD and 1870 AD in Europe?
Looking at one of the time lines I have given you before for smelting, one is inclined to conclude: not much! Bloomeries
were still run in the 17th century or even later, and the basic process was not much different from the one used 1500
years earlier. A sword was still forged by a smith. A 200 BC Celt coming out of some deep freeze in 1500 would hardly
note a difference in the forging process.
So the basic techniques for making swords and other iron / steel items didn't change much. That is also quite
typical for other cultural / technical developments. Does that mean that the products didn't change much either?
Just for fun, let's look at how the changes of products relate to the changes or non-changes in basic technologies.
Here is a first example:
Same basic technique, quite different product / result

Uta vonNaumburg, middle
Celtic sculpture, around 400 BCof
One of the earliest North-European full- the 14th century
size sculptures
One of the mostimpressive
Gothic sculptures.
Large Picture

The difference (I guess) between using bronze or steel
chisels

Iron, Steel and Swords script - Page 388

The basic technique is exactly the same in both cases: take a rock and chisel off what you don't want. The products
display quite different levels of sophistication, however. Progress comes from attention to details: pick your rock withgreat deliberation and care, use chisels and hammers of different size and shapes, learn from a great master,
peregrinate around a while and learn from other masters and "schools", take great care of the final finishing and - mostimportant - practice a lot.
The basic technique of making iron and steel remained exactly the same for for at least 2000 years: bloomeries
processed iron ore with charcoal and produced a bloom. Bloomeries were still run in the 17th century, if not later.
The details of how it was done and the quality of the product changed quite a bit, however.
Before I get to the development of bloomeries, let's look a the other extreme: Rather different technologies produce
essentially the same product.
Different technologies, same idea / product

Baroque plaster cast; Dresden
Around 1700

Roman mosaic,
CopenhagenmuseumAround 100 AD, I
guess

Large Picture
Since I know that you enjoy artwork, here is more of the above.
It's good to have you back. For our purpose here the example is making steel. You can do that in many different ways,
e.g. by putting carbon into wrought iron, or taking it out of cast iron. The product is the same, the technologies are wildly
different. You need to invent the blast furnace, making cast iron and fining it before you can make steel in the secondway.
Some things don't change much at all, however. Here is an example from everyday life:
No change in production technologies and products(babies) for
untold millennia

Iron, Steel and Swords script - Page 389

Nefertiti and two daughters (ca. 1350 BC)
Source: Photographed in the "Neues Museeum", Berlin

For our purpose here the example is black smithing or forging. A 1900 black smith would have had not much trouble to
do his work in a Roman smithy and vice verse.
Then we have revolutions where something utterly new appears. Quantum theory, for example, changed humanities
way of life rather radically:
New insights, technologies and products fromquantum theory

Iron, Steel and Swords script - Page 390

Hydrogen bomb / nuclear energy; Anti Baby pill;
microchipInternet / computers
All are children of quantum theory.
As far as iron and steel are concerned there were many small revolutions and two big ones. Small revolutions concernedfor example the introduction of the blast furnace, the use of coke instead of charcoal, making wrought iron and steel
from cast iron, and so on. Big revolutions occurred around 1870 (Bessemer et al. allowed steel mass production) andaround 1950 (quantum theory allowed understanding). We might also see the direct use of cast iron as a revolution
leading to new technologies that enabled novel products.

Vagn Buchwald has written a 600 page book including a million or so pictures on "Iron Steel and Cast Iron before
Bessemer"; sort of a sequel to his 370 page opus "Iron and Steel in Ancient Times". The topic: "Iron and Steel inModern' Europe" of this chapter is covered extensively in Buchwald's books Read them and then come back. I'll wait.
You also may just read on if you promise not to grumble at what follows. It is comparatively short and thus biased. I
will omit a lot, I will be subjective, and sometimes I might generalize too much. What I will cover is:Power by water wheel for blowing, hammering and other jobs around making iron and steel.
The Stückofen and the Catalan forge as examples for advanced bloomeries.
The blast furnace, cast iron, and making wrought iron and steel from it.
What happened around 1870 and beyond.
Water Wheels as Sources of Power
On my exercise bike I can deliver around 100 Watts (W) of power for many hours, and 150 W for some 30 minutes or
so. That's not bad for a guy of my size and age. Athletes can do better, but not very much better. Your male slave (oryour wife) pushing the bellows thus is good for about 0.1 - 0.2 horse powers (1 HP=746 W) for 8 - 10 hours a day. Aslong as humans were the essential source of power around iron making, the size of the operation was limited. And no,you do not usually use horses. They are not only far too valuable, they are also to stupid to dig in mines, to work
bellows or to swing a hammer.
One could of course use many humans to get more power, as the ever inventive British and Americans
demonstrated:

Steel engraving of people being punished in a prison
in Jamaica in 1837
Source: Internet at large

Not only did your prisoners and slaves get their daily constitutional by running a treadmill, they also produced
power on the side. The team above will produce about as much as a valuable horse!
But let's be honest: treadmills, horse mills and other contraptions for producing some power were used everywhere
throughout antiquity. The were turned by humans, horses, donkeys and so on - and even by dogs on occasion.
A water wheel as power source is much better. It provides easily for 3 - 4 horse powers or more, works without
interruption (as long as the water flows), doesn't need to be fed and to go to the bathroom, and never wails andcomplains. However, for making a good one, you need iron and steel.
The Romans (and others around their time) did use water wheels for all kinds of things but apparently not in the ironand steel industry. It was used for moving water up (including in mines), for grinding cereals, for operating marble
saws, and I don't know what else. Constructions like this one (and simpler ones) may have been in used in the later
first millennium BC:

Iron, Steel and Swords script - Page 391

Water wheels in Hama, Syria, from the 12th - 13th
century
Source: Hama Internet site

After the official end of the Roman Empire in 476 things declined for a while but the water wheel technology neverdisappeared totally. Eventually it spread over all of Northern Europe, reaching England in the 9th and 10th century andthe more remote corners of Scandinavia and the East in the 11th and 12th century. In the Domesday book from around1085, more than 5000 water mills were listed for England alone. The Domesday book, by the way, records the resultsof a great survey of much of England and parts of Wales for William I of England, better known as William theConqueror. He wanted to find out what and how much each landholder had in land and livestock, and what it wasworth, so he could tax it accordingly. The fun of conquering is always with the conqueror and not so much with theconquerees.
Water wheels were important for mining by then. And mind you, mining did not focus on getting iron ore - that wasmore or less all over the place - but on silver, tin or other more precious ores. You needed to move things, to crush
the ore and, most important, to get the water out of the shafts. That takes a lot of power.
As far as iron and steel making is concerned, all of the above helps. Water wheels were essential for getting andpreparing the ore. They also allowed to pump big bellows needed for blowing big bloomeries. Without them you could
not move the big hammers needed to forge the big blooms that will come out of big bloomeries.
The catch is: all the machines needed must be in operation at the same time. Big blooms are useless without big
hammers at the ready. "Man muss das Eisen schmiede solange es heiß ist" (You need to forge the iron while it is hot)is a well-know old proverb in the true language of iron and steel. You are now running a demanding business and nolonger a I-do-it-when-I-feel-like-it outfit
It appears that it took a few centuries before all the infrastructure that was required besides just having a water
wheel came into existence. What is needed for "power" bloomeries and "power" forges (as shown below in a 1550
illustration) are the following ingredients:
A place at a running water that could drive big wheels. It is unlikely that this place also has iron ore near-by.
That forced the bloomeries to move down into the valley from their more lofty uphill places close to the ore,and to establish the logistics for ore transportation. Charcoal still could be produced in the next forest
typically not far away.
Big bellows like these. Those are far more complex machines than the ones a human could pump.
A device that transforms the rotational movement of a water wheel into the up-and-down movement needed
for pumping bellows or moving hammers. Not so easy in ancient times.
A control of pumping and hammer movements that are a bit more subtle than just "on" and "off". That
necessitates, for example, a control of the water flow across the wheel.
A second independent wheel that moves a big hammer like this one controllably up-and down.
The necessary infrastructure for running a big bloomery and the power forge in perfect synchronization.

Iron, Steel and Swords script - Page 392

Water mills power hammers and bellows
Source: From Olaus Magnus: History of the Nordic Peoples (1555);
open access Internet

In other words: Besides being in possession of a lot of know-how you also need to make quite an investment and to
employ a sizeable crew of experienced guys good at tricky and dangerous team work. And you had to be at it all thetime if you wanted a return on investment. You needed to make a profit not only for your own sake but also for paying off
the Mafia (then called nobility).
Contrast that to the small uphill bloomery. You could run that yourself with the help of your family during the vacation
time or on long weekends. You could not loose much cash because most of your investment was the work you and youryokels put into the effort. At the worst you lost some time, at the best you made cash or saved some because you did
not need to buy your iron from others.
Somewhere here is the reason why it took quite a while before big power-blown bloomeries (more or less the same as a
blast furnace) in conjunction with power-hammer forges became the standard. In Agricola's famed book from around
1550, many water wheels are shown in connection with mining and water control (like pumping) but only a few times,
rather indirectly, connected to blowing or hammering.

Big reversible water wheel forup and down movements of a load.

"Power"bellows and a"power"hammer (D);water wheel notshown.

Water power in Agricola's bookMore and large-scale pictures
Uses of water power for smelting are recorded for the early 13th century, and it happened indeed in the 12th and13th century that bloomeries moved downhill to rivers that could drive water wheels.
Power hammers were definitely in use around 1335 in Spain. In the 15th century the Basque "valley of iron" saw as
many as 20 hammer-works in Lagazpi; wherever that might be. Large bloomeries as part of a sophisticated"industrial" infrastructure could now develop - the next paragraph gives two examples.

Iron, Steel and Swords script - Page 393

Stückofen and Catalan ForgeIn Roman times bloomeries were run in a well-organized way; the increase in bloom size encountered in England gives aclear idea about that. While the development of the bloomery must have gone through ups and downs, they did notseem to have changed very much until the use of water power allowed making and processing larger blooms.
The good old "Ferrum Noricum" changed its name after the demise of the Roman empire but the iron and steel making
tradition around Erzberg / Hüttenberg lived on (until almost today). Power bellows and hammers took over in the 12thand 13th century and the bloomery furnace became bigger and was made from sturdy stone masonry, typically with arectangular cross section.
The only halfway contemporary picture, once more, is from Agricola's book:Stückofen
However, Agricola omitted the bellows. They often were right in front but could be on the backside behind the wall inthis case. The lower part (plus possibly the bellows) had to be removed to get at the bloom, which in German iscalled "luppe". That's why a Stückofen is also called a Wolf's Ofen in German. And it's "Stück", not "stuck",meaning piece, chunk, lump.
The Stückofen shown above would have produced something like a 20 kg - 30 kg bloom, far too large to be forgedwith 2 kg hammers powered by humans.
As time went by, the Stückofen grew in size. In 1430 blooms weighing 370 kg were reported - just what you needed tofeed to your 500 kg power hammer. Larger and larger Stücköfen automatically became hotter because of theirincreasing volume to surface ratio and if they produced cast iron, you called them blast furnace. In fact, cast ironappeared as an unwished-for by-product besides the bloom in late Stücköfen. Eventually the iron masters learned towork with that stuff and the era of cast iron production began; see below.
Meanwhile the Stückofen (actually rather called "Blauhaus" or "Plahütte" (=Blashaus or blow house) by the local
yokels) reached gargantuan sizes. When the last one in Austria was was finally extinguished forever in 1770, theblooms had reached masses of 900 kg!
In many areas in Europe similar developments took place. Similar but not identical. Each place had its specifictechnologies, based on tradition and local know-how. Local procedures were optimized by evolution to local conditions,like the kind and quality of the available ore. However, small revolutions also occurred. One was the invention of the"trompe", an air blowing device radically different from bellows. Today we call it water aspirator and it is an ubiquitous(small) device in many laboratories.
The principle is simple: A water jet rushing down a pipe with an opening in the upper part will suck air down with the jet
too, and thus can be used as a pump for evacuating vessels (today's use), or as a blower creating an air stream.
Iron, Steel and Swords script - Page 394

The trompe appeared around 1620 in Spain and moved up to Southern France and other places. It was employed inwhat is called a Catalan furnace or forge. What we know about this type of bloomery goes mostly back to
Southern France, not Catalania. The trompe supplied an especially steady airflow that could be well regulated. The
water vapor coming with the air might have been beneficial, too, since it decomposed into hydrogen and carbon
monoxide at high temperatures.
Here is what a Catalan furnace with a trompe looked like:

Catalan forge with trompe
Source: Libre de la Farga, 1983; via Buchwald.

The trompe is interesting but it never replaced the bellows completely. The Catalan forge is interesting to us for anotherreason: the way it was constructed and loaded. It looked more like a squat asymmetric bathtub than a pipe, and parts of
its walls were made form thick cast iron. The ore was divided in two grades: walnut sized lumps and coarse powder.
First the bottom was filled with charcoals up to tuyere level, then (with the help of a temporary divider) charcoal was
piled up close to the tuyere and layers of charcoal, ore lumps and ore powder to the right as schematically indicatedabove.
The furnace was run on a light blast for the first three hours or so. The slag tapped during this time was fed back to thesmelter. Then the blast was increased and more ore and charcoal added as needed. The charcoal side close to thetuyere was moistened and compacted with shovels on occasion to avoid gases from escaping there. A big advantage of
the Catalan furnace was that it could be stoked and "worked" from above while it run.
The Catalan furnace was still a bloomery - but with plenty of attention to details!
A bloom of up to 150 kg was recovered through the side by lifting it out with levers (and with effort!). The process
produced three qualities of iron /steel. The inside of the bloom consisted of soft, almost carbon-free wrought iron, theoutside was good hard carbon steel, and the intermediate regions intermediate. The iron master had many ways tocontrol the product:
Change the ratio of charcoals : lump ore : powder ore.
Change the tuyere inclination.
Change the airflow / processing time.
Change the amount of the manganese oxide that was supplied with some gangue. More of that kind of"gangue" gives more steel.
I gave you these data to illustrate the point I made above: The basic techniques hardly changed but substantial progress
comes from attention to details!

Iron, Steel and Swords script - Page 395

The Blast Furnace
Stückofens, Catalan forges, and just about any bloomery are blast furnaces in the literal sense oft the word. What theterm really means, however, is a furnace where enough air is blasted in to allow the production of cast iron and nothing
but cast iron (besides slag, of course). The term also implies continuous smelting with high efficiency of even "poor"ores. In fact, as pointed out before, the slag from ancient Etruscan and Roman bloomeries was used as a good iron ore
and fed into blast furnaces around 1925.
Just looking at the making of liquid and carbon-rich cast iron misses the point, however. Making that in a bloomery typeof furnace was never a real problem, except perhaps for the very early times of iron bloomeries. It appears that European
iron makers simply avoided to do this because the product was not useful to them. It also needed more charcoal andmore efforts at blowing, so why bother?
We know of course that cast iron is quite useful in two rather different ways:
1. Cast iron, though brittle, can be directly used for making all kinds of universally useful things like bathtubs or
man-hole covers plus questionable things like cannons and cannon balls by simply casting the liquid into amould.
2. Cast iron can serve as a cheap raw material for making pure iron and all kinds of steel
We also know that the Chinese made cast iron in blast furnaces right away and used it for both applications
enumerated above.
In the West, however, cast iron came into its own rather gradually. Power-blasted bloomeries like the Stückofen or theCatalan forge could easily make cast iron if so desired, and it appears that its production parallel to a bloom could often
not be avoided.
The Austrians in the "Ferrum Noricum" region knew the stuff. Cast iron was produced on the side in their larger
Stückofen; it could be tapped and collected. The Austrians called it "Graglach"; lach containing the German"Lache"=puddle, pool, (small) lake. "Grag" is unclear, it appears, but I believe it simply comes from"krakelig"=scrawny, spidery; and Graglach is simply a pool of liquid iron that looks like this:A "krakelige Lache" (?)=(?) Graglach. Here it happens
to be (now solidified) copper
Source: Photographed in the Copenhagen museum

You can't get much more krakelig than the copper above. Anyway, the old iron guys learned to do things with the
graglach and eventually it became a commodity traded far and wide. In 1469, for example, one Peter Pögl delivered
14 000 canon balls to Emperor Friedrich III, called the Peaceful, who wanted to play ball with the Hungarians,
Bohemians or the Turks if the first two weren't available.

Iron, Steel and Swords script - Page 396

Meanwhile some other Austrians run a "Flossofen" (German for flowoven) with know-how imported from Brescia, Italy. A
Flossofen was not all that much different from a Stückofen but used only for making cast iron - up to 2000 kg a day! Thatstarted in 1570 and that enterprise ran parallel to making huge blooms around the corner of the river in the Stückofen. I
would guess that the Flossofen guys used calcium carbonate (CaCO3) or limestone as flux, given the large yield of ironthey obviously enjoyed, but I don't really know. Supposedly it was the Durch Jan Andries Moerbeck who found out
around 1619 that the limestone was good for fluxing because he noticed that the English in the "Weald" wereparticularly successful in smelting cast iron because their ore was "self-fluxing" and contained limestone as gangue.
With limestone as flux you first form quicklime (CaO) at high temperatures, which in turn produces some calcium
silicate as liquid slag component instead of the good old iron silicate fayalite that still contained much of the iron fromthe ore. The "limestone slag" contains only little iron (around 10 %) instead of about half of what the smelter was
originally fed with in the case of fayalite.
How cast iron and thus the blast furnace came into its own is a tangled story, intermixed with the development of
the gun. You need a lot of metal to make a 1000 kg "bombard" or cannon, and it needs to be "good" metal lestyour weapon explodes upon firing. Good bronze is fine but rather expensive, and wrought iron or steel from abloomery is not so easily turned into a huge object just by forging and fire welding; see below. Cast iron would be
ideal but you better know how to work with this brittle material before you cast a gun and fire it. Cast iron, as weknow, comes in many grades and can have a wide range of properties.
Don't forget that the technology of metals other than iron was quite developed in the Middle Age. Large bells were
cast from "Speiss", by then more or less weird copper-centered alloys. Of course people started mixing the newliquid iron with everything else they could liquefy and a lot of weird and useless stuff must have been produced.
Suffice it to look at a few dates and events (mostly taken from Wertimes book) just to illustrate what was going on:
In 1353 Berthold Schwarz invented "black powder"; necessary for guns and cannons. No, he did not! It's amyth. Knwledge about black powder diffused to Europe from the East (China), andAlready around 1320 the first guns appeared in Europe.
1390 the first recorded casting of a cast-iron cannon took place in Frankfurt/Main, Germany.
Wesel, a town in North Germany, possessed a cast iron gun in 1400.
In Burgundy iron cannons were cast (and the fact recorded) between 1414 - 1417.
Cast iron cannons appeared in Italy in 1429 (plus cast iron pans)
Siegen in Germany started mass-production of cast iron cannons in 1445.
On 29 May 1453, after an eight-week siege (during which the last Roman emperor, Constantine XI, waskilled), Sultan Mehmed II "the Conqueror" took Constantinople (afterwards calld Istanbul). A cannon was
decisive in destroying the famous walls of the city.
But: Neither Agricola (1556) nor Biringuccio (1540) in their lengthy books pay much attention to cast iron,even so the latter devotes plenty of space to casting cannons with other metals.

I's not so easy to forge a cannon on a normal smithy
hearthSource: Donal Duck Sonderheft Nr. 28; with friendly permission of
Ehapa Verlag.

Iron, Steel and Swords script - Page 397

People obviously did use cast-iron to cast cannons, cannon balls, frying pans and much other stuff around 1400 or evensomewhat earlier. It the objects were well made, it didn't matter much that the material was hard but brittle. It still could
be strong enough for the purpose. Your porcelain toilet is perfectly brittle, for example, but can take a lot of punishment.
Using cast-iron as a raw material for making wrought iron and steel of all grades is a different matter, however. You had
to take the carbon (and other stuff) out almost completely in order to get soft wrought iron. If you wanted steel, you had
to stop a the right moment in the process of reducing the carbon concentration (almost impossible) or, if you went all
the way resulting in wrought iron, put some carbon back in. Sounds not only complicated; is complicated - but still
worth it, because making cast iron as starting material had tremendous advantages in comparison to running a
bloomery:
1. The smelter could be run in a continuous process for days or weeks on end. Keep feeding your blast furnace withore, charcoal and flux, keep blowing it steadily, and you can tap your cast iron and the slag periodically without
ever stopping (as long as the walls hold out).
2. Size is no longer limited by keeping a bloom from getting too large. You can now make your blast furnace rather
large, automatically increasing efficiency and the output.
3. You can use limestone as flux, avoiding fayalite formation. Your slag thus does not have to contain a lot of iron
anymore and efficiency goes up.
4. You can use difficult ores - either low grade ore or high-grade but hard, e.g. stuff like magnetite.
5. You produce a liquid that you can cast directly or after remelting!
With coke replacing charcoal after 1730 (look it up here) blast furnaces could get even larger. Coke is mechanicallystronger than charcoal and doesn't crumble if the weight of the burden exceeds a certain limit. It is not as reactive
as charcoal but you don't need to cut down your last trees in order to make it. You could dig up plenty of the coalneeded to make coke in the coal mining places. That is the reason why iron smelting now moved to the places
where coal was abundant.
A soon as cast iron was understood, one could make all kinds of machinery and parts besides cannons. Watt's steam
engine from 1765 could not be imagined without cast iron. In time it provided more power than the water wheel, and blast
furnaces could be made bigger once more. The steam engine also provided sufficient power for blowing air through liquid
cast iron, allowing the Bessemer process and anything else that caused the industrial revolution that is still going on. In
case I haven't mentioned it yet: There can be no silicon technology without steel. There is plenty of steel inside any
semiconductor manufacturing plant.
It's time to stop or I will need to start another Hyperscript, far larger than the present one.

Iron, Steel and Swords script - Page 398

10.5.2 Making Steel up to 1870
A few General Points
In the preceding subchapters I have given you a hell of a lot of details about making solid blooms in a bloomery andliquid cast iron in a blast furnace. Making steel was somehow mixed in with all of that. As far as iron and steel making
in bloomeries is concerned, I have essentially covered that. However, I have not yet given you much about how to makewrought iron and steel from cast iron.
So let's look a bit more focussed on how to make steel, in particular if you start with cast iron. But before I come to that
I will deal once more with making steel in a bloomery. And before I do that I need to point out something:Throughout the ages the averagecustomer wanted wrought iron,not steel!

Wrought iron or mild steel, stuff easy to forge and easy to work with (e.g. by filing, drilling, bending, ...), was what
one needed for most everyday products - the last subchapter will give examples. Hard steel was good for (some)
weapons and some civilian things, for example coulters (I'll get to that) or piano wires. It is estimated that about 90% of the iron production was for wrought iron and not steel for most of history up to modern times.
If you were running a bloomery you tried to get a bloom of carbon-lean iron most of the time. Since archeologist mostly
reported that they found wrought (or better carbon-lean) iron, and since theoreticians predicted that bloomeries should
produce nothing but wrought iron, there shouldn't have been a problem in making the stuff. The problem for people
investigating old objects was rather to explain why there was also quite a bit of steel around, especially if you went backto the very early iron era. The explanation offered for this was simple: a smith carburized the wrought iron in his hearth even in cases when this made not much sense because he would have been better off with wrought iron.
As we know now: all of the above is wrong. Why? Here are the reasons in short:

1. Archeologists actually did not find mostly carbon-lean iron. Almost 1000 analyzed iron artifacts from late anquity
to 500 AD contained an average carbon concentration around 0.5 %, as already pointed out before.

2. If later products were indeed carbon-lean it only means that people by then had learned to run their bloomeries insuch a way that they did produce at least some wrought iron that could be separated from the steel also produced.
That bloomeries actually do not produce wrought iron only but anything between wrought iron and hypereutectoid
steel has been proved by plenty of experiments done recently.

3. A basic and quite valid theory does indeed predict thatonly wrought iron should be produced inside a bloomery as
long as there is still some wüstite (FeO) around (meaning always). The theory is not wrong but just too simple.
Bloomeries are far more complex than considered some time ago when the theory was conceived. Here are details.

4. Carburization of a sizeable piece of wrought iron in a hearth cannot work for quite elementary reasons as
explained here.
So what do you have to do to get a piece of nice steel with a defined carbon concentration of, for example, 0.5 %, 1 %or 1,5 %? From just a bloomery? From cast iron? Or from combining whatever you have? Plenty of good questions.
But let's not forget: there is also phosphorous steel. And mixed carbon - phosphorous steel. Plenty of that, actually.
And we have ancient crucible steel or wootz / bulad in many variants. Not to forget either: if your steel product should
contain x % carbon, you generally must start with a higher concentration because forging actually always de-carburizes
your steel. A little more carbon or quite a bit, depending on what exactly you do with your steel.
What already becomes apparent is that many different kinds or grades of steel
emerged after, let's say, 1500. And all these iron / steel kinds had names! Since
we have more writings about iron and steel from 1500 and beyond than actual
samples, we often don't know what, exactly, a certain name implied. Names ofsteel might point to the origin, to intended uses or to the method for making. What,for example, is pig iron? Or sarschach steel? Who put the blisters in blister steel?
The link leads to a module with a list of expressions and names for iron and steel.
In what follows I cannot go into all the intricacies hinted at above. I will therefore
only give a taste treat.

Iron, Steel and Swords script - Page 399

Advanced
Link
Iron / Steelnames

Making Steel With Bloomeries
Let's start simple and only consider pure carbon steels from a bloomery for starters. If you want steel of some type, you
first need to make a bloom. Then you need to separate the steel grade you want from all the other iron / steel that is
also contained in the bloom you made. Finally you have to forge your steel pieces into a bar or billet with as few slag
inclusions as possible. If you were very good at that, your product might have been relatively uniform steel.
Your options for optimizing this process chain are limited:
Run your bloomery in such a way that plenty of the wished-for steel is produced. Easier said then done but
possible within limits.
Try to make the bloom compact and homogeneous with respect to the desired carbon concentration. That seems
to be quite impossible, so:
Try to make the bloom as compact as possible with a clear distribution of the carbon. You might for example
make a bloom with wrought iron inside and steel outside. That can be done but it is not easy.
Optimize your ore and (in later times) the flux you added. That is your best option. In particular see to it that yourore contains some manganese oxide (MnO). For reasons not entirely clear that helps to make steel. Also
carefully pre-treat your ore by cleaning, roasting or even weathering it for a few years (maybe dissolving someunwanted impurities in the rain).
Find ways to recognize and separate the proper steely parts from your bloom.
These recipes do not look very convincing, in particular because they aren't really recipes. It's like proposing tosomebody who has the ingredients for making bread to take them but to make cake now. Small wonder thatdifferent cooks at different places and times produced different cakes - if they produced cakes at all! And some of
the cakes might have looked good but had a weird aftertaste and gave you heartburn - like steel containing some
phosphorous.
But once more: what I listed above is about all you can do. The key word then is: experience! On the part of thebloomery masters and the smiths. Ways were needed to judge the quality of some iron / steel, and there must havebeen a lot of "tricks", some probably lost by now. I'll get to some of that later.
Making Steel From Cast Iron - Basics
That's how we make steel right now and how we made some steel for the last 500 years or so. The Chinese were at it
longer: for the last 2500 years or so.
So let's remember: Cast iron contains about 2 % - 4 % carbon and usually a bit of this and that. If silicon is among thethis and that, you might get grey cast iron instead of white cast iron and so on. Read up about this here .
Whatever - if you want to make steel you have to take out some of the carbon. In principle this is easy. Just remember
how your very remote ancestors got their copper clean. Just melt the stuff again and expose it to oxygen. Everythingthat likes to oxidize will oxidize at the high temperatures needed for melting and either disappears as gas (like carbon),forms slag (like silicon) or what's called dross: oxides that swim on top of the liquid metal.
There is no problem for cleaning "dirty" copper this way. Cleaning iron, however, is not so easy. We encounter
major problems:
1. As the carbon disappears, the melting point goes up. From a meagre 1140 oC ( 2084 oF) for eutectic castiron (4.3 % carbon) to 1538 oC (2629 oF) for pure iron. You cannot produce that kind of temperature and thatmeans the stuff soldifies before it is pure iron.
2. Solidification is inhomogeneous. The solid lumps that form first are austenite with far less carbon than yourliquid; see the picture right below.
3. The temperature might be a bit erratic. The oxidation of the carbon to carbon dioxide (CO2) produces a lot ofenergy or heat and your temperature might actually go up.
4. You also remove all the good stuff like manganese and silicon.
5. And you remove some of your iron because it oxidizes too. This provides energy and thus raises thetemperature even more. You typically loose 25 % of your iron.

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Solidification of 3.6 % carbon cast iron

The example shows what happens if 3.6 % carbon cast iron solidifies in three different ways.
First, doing nothing but by cooling down, the state point follows the dark blue line. As soon as the mix has reached
the austenite (γ) - liquid phase field, it decomposes into solid austenite with at most 2 % carbon and a liquid with acorresponding carbon concentration above 3.6 %. As soon as the temperature drops into the austenite andcementite field, we will find lots of cementite and carbon-saturated austenite. Same thing once more when the final
ferrite (α) - cementite field is entered.
Second, if the carbon concentration is reduced at constant temperature, the state point follows the green line. Once
more the first solid to form is austenite with just about 1 % carbon.
In reality one follows a line like the bluish one that first moves to the left, possibly first going up because of the heatgenerated by forming CO2, burning iron and anything else. Eventually it will come down - the blue line gives an ideaof what that could look like.
It should become clear that you cannot reasonably expect that a solid with a perfectly uniform composition will result. In
the first two examples above most of the carbon has to come out while the stuff has solidified, and that depends on
relatively slow diffusion. Your best bet for making wrought iron is to move left and up as much as you can, taking out the
carbon while everything is still in the liquid state.
If you want to make steel, you now have two basic options:
1. Remove just as much carbon as is necessary to end up with the concentration you want. But how to do this?
How to know when to stop? And how to stop when you know the time has come?
2. Make wrought iron first and then put back some carbon. Complicated but maybe worth the effort because a lot of
people made wrought iron, meaning that it was around and cheap.
Of course you can also mix the two basic ways. Considering that for most of the time people made steel, they didn't'
know a thing about carbon, you can be almost sure that strange and overly complex procedures were used. But all thatcounted was that it worked.
Making Steel by Fining Cast Iron - Examples
Let's look first at making wrought iron from pig iron. I will call the product of the blast furnaces from now on pig ironbecause that was its name for many centuries. Again, wrought iron was in far higher demand than steel. One thing isclear: you should liquefy the stuff first. For fining your cast iron to steel, you run a finery . A finery, on the outside, is
not all that much different from the good old smithy were you worked or wrought your old-fashioned bloom. The
procedure isn't much different either if viewed from a lofty perspective: heat it and bang it! It's the details that make thedecisive difference. The hardware is quite different, for example. While in ancient times you heated your bloom in a pit in
the ground and banged it on a hard rock, you now run a raised and complex hearth blown with bellows, and you bangwith a whole set of hammers (including power hammers) on an anvil or other specially made surfaces. And what you do,exactly, is also different, see below.
It appears that fineries for pig iron were first used in the Sauerland / Siegerland area in Germany, a major iron / steel
producing regions until the advent of coke-fed furnaces, when everything moved to coal-rich areas, for example the"Ruhrgebiet" in Germany.
A good way to start is to break up the pig iron into smaller parts, something not too difficult to do with the brittle stuff.
What might happen next for making wrought iron I give you in the words of Vagn Buchwald (with my markings),
describing the production of "Osmund iron", a Swedish commodity traded far and wide from the 14th to the 16th
century:

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"With hand-blown bellows a helper and the Osmund smith maintained the charcoal fire and moved the pig ironfragments into the oxidizing blast. The iron smelted at 1150 oC - 1200 o (2102 oF - 2192 oF) and transformed into
small drops that started to burn, i.e. react with oxygen. The reaction was violent and accompanied by significant
heat evolution of about 400 kcal per kg of pig iron, all elements of the pig iron participating. Because the pig irondisintegrated into droplets with a large surface, the reaction went to completion within minutes and a new pasty
material, malleable iron with low content of carbon, silicon and manganese was formed. The Osmund smith carefully
manipulated the new iron in the hearth so that it sintered into larger lumps, in the end forming a cake or bun of about
4 kg - 7 kg".
Now did they smelt or melt their pig iron? If you consider pig iron to be some kind of iron-carbon ore, smelting could
be the right word, so I won't criticize Buchwald for using it. But in effect the pig iron was simply melted.
Pasty material means that you have a two-phase mix. One phase is solid, the other one is liquid. In other words,
that's the austenite-liquid mix.
If the reaction really went to completion, i.e. if all carbon was removed, remains to be seen. That Osmund iron was
wrought iron was always just assumed. Historians who looked into the Osmund iron production and trade only founda lot of paper, documenting what was going on. What they did not have was a piece of actual Osmund iron. Thatchanged only recently (beginning around 1980), and finally one could analyze the stuff. Here are typical analyticalresults from Osmund iron, as presented in Buchwald's book:

No.

C

Si

Mn

P

S

Pig iron (typical)
A

4.1

1.10

1.35

0.028

0.028

B

3.06

0.79

0.32

0.018

0.050

Osmund iron
1

0.16

0.07

0.03

0.017

0.005

2

0,58

0.04

0.03

0.024

0-005

3

0,34

0.10

0.08

0.012

0.024

4

0.51

0.10

0.06

0.011

0.019

5

0.97

0.03

0.01

0.009

0.007

Composition of pig iron and Osmund iron

What we have here is steel and not wrought iron! Samples 2 and 4 represent good hypoeutectoid steel that could be
hardened by quenching, and sample 5 is actually a rather brittle hypereutectoid steel. Either the process was notalways completed with respect to the carbon or the old iron mongers put some carbon back into their product.
The picture below shows a whole barrel full of Osmund iron. It was found (but notanalyzed and recognized for what it was) in 1969 close to Gdansk, Poland, in a
shipwreck dating to 1450 -1500. The barrel is now in the Maritime Museum ofGdansk; originally it was labelled "iron ore". That is not quite as idiotic as it
appears since most of the original iron pieces had meanwhile oxidized to stuff
resembling ore. However, some iron survived and was found to be hypereutectoid
steel with about 1 % carbon. So, contrary to "public opinion" in historically mindedcircles, Osmund iron was not exclusively "sehr weiches und zähes, gut
schmiedbares Eisen" = very soft and tough iron, good to forge (German Wikipedia)
but also steel.

Illustration
Osmund;GdanskMaybe the guys doing the production just couldn't control the process very well and involuntarily produced a whole
spectrum of carbon concentrations? Maybe they knew how to make made various steel grades deliberately ? By
method 1 or 2 from above? Were different products offered and traded?
I don't know. But I'm sure we will find out in the fullness of time

Iron, Steel and Swords script - Page 402

A barrel full of Osmund steel
Source Buchwald's book, i.e. from around 1980

Similar fining processes were run elsewhere and elsewhen, for example in the Walloon area (Belgium). Letting the pig
iron melt drop-by-drop was essential. A small drop could heat up enormously by the heat released from all theoxidations taking place, and the large surface-to-volume ratio made it possible to get the oxides out. Note that theresultant carbon-lean iron could not be kept liquid anymore so the resulting particles needed to be compounded once
more by sintering and compacted by banging! By fining pig iron you essentially formed a bloom! But this was now arather uniform and relatively slag-free bloom.
Fining pig iron was not easy. A source as late as 1775 points out that "fining iron is the most difficult operation inmetallurgy", for example.
There were some other ways to get the carbon out. I give you just one example as a taste treat: the "Kärntner
Löscharbeit" (Carinthian extinction or quenching work):
Sprinkle some water on your pool of molten pig iron (be careful!) so the surface layer solidifies. Since the surface
region was exposed to oxygen it might have had a lower carbon concentration than the bulk. The austenite forming
first allows only less than 2 % carbon, anyway. Remove the resulting thin solid and carbon-lean plate. Repeat theprocess and you get a whole collection of thin steel plates called "Blattel" (leaflet), about 6 mm to 1 cm thick andwith around 1.5 % - 2 % carbon. Stack them and heat the batch in an oxidizing atmosphere for a while and you get
wrought iron. Once more, the large surface to volume ratio of thin sheets helps enormously in this.
Eventually - 18th century and beyond - a lot of wrought iron was made from pig iron in one way or another. All methods
depended on getting the carbon out by oxidation in air and on the surface. Wrought iron was in large demand, seeabove, and a sizeable industry revolved around making it.
Steel was also in demand. You didn't need all that much in quantity, but you needed the quality. Many products simply
needed steel; if made with wrought iron their quality was poor or not acceptable. So being able to make steel from pig
iron was crucial and important for competing nations. Everybody could make wrought iron, not to mention that you could
just buy it. But not everybody could make good steel and process it. If you had the better steel, you had a commercial
and military advantage.
Until about 1870 steel was made from pig iron with the two totally different basic technologies given above. Now we will
give them names:
1. "Cementation" = putting carbon into the wrought iron that was made first from pig iron.
2. "Puddling " = making steel by taking some but not all carbon out of pig iron.
There were many variants per basic technology and some precursor in older times but I won't go into this; suffice it tomention the basics.
Let's look at cementation first. The name is a bit unfortunate and has come to mean, in modern terms, solid-stateprocesses where the material to be processed is immersed into (powdered) solids, followed by heating the ensemble.
And yes - cementation does mean carburization of wrought iron! But didn't I stress repeatedly that this couldn't be
done?
No, I didn't!
I did stress repeatedly that a smith couldn't carburize sizeable pieces of iron in his hearth! An industrialist, however, cancarburize sizeable pieces of iron by completely immersing them in carbon dust (plus some magical ingredients)
contained in a cementation box, followed by cooking the whole thing at high temperatures for days in a kind of kiln.

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The process was described in a treatise published in Prague in 1574. Then it was re-invented by Johann Nussbaumof Magdeburg, who began operations at Nuremberg (with partners) in 1601, says Wikipedia. Cementation on a large
scale started in the early 17th century in Germany and then spread; in particular to England - but not to France forsome reasons I don't know of.
The heating lasted for a week or more. The temperature was certainly high but I couldn't find any numbers (notsurprising considering that nobody could measure temperatures this high). The surface of the finished steel productoften shows "blisters", supposedly related to the gases CO and CO2 that were produced in the mix but couldn't getout completely. Personally, I'm pretty sure that the blisters were rather related to hydrogen that quite likely was also
produced - but I won't bore you with details. Just believe me. Anyway, here is the reason why cementation steel
was also known as blister steel.
Henry Cort from England is usually credited with inventing puddling; his patent is from 1784. Puddling essentiallymeans that you stir a pool or "puddle" of molten pig iron with a kind of paddle, getting oxygen in and carbon out. The
stirred region gets carbon leaner, its melting point goes up, austenite starts to solidify since the temperature was around1300 oC (2372 oF) at most.
Eventually the iron "comes to nature", and forms a pasty lump of austenite plus liquid that you can extract and let cooloff. In principle it proceeds exactly as shown for the old Chinese here.

Puddling - extracting the product"A puddler and his helper remove a 150-pound, nearmolten ball of wrought (? Nah, It's steel ) iron from a
puddling furnace at Youngstown Sheet & Tube’s CampbellWorks in the 1920s ."Large picture
Source: Jarret Ruminski's Internet blog.

In practice, however, the Western puddling was far more sophisticated. It was suitable for mass production because
it did not depend on charcoal but used regular coal or coke in a reverberatory furnace. Note that once again a kind ofbloom was produced that needed to be forged in order to make it compact and homogeneous.
Puddle steel was the best steel for its time. It was almost slag-free and halfway uniform. The Eiffel Tower(1887)and the original framework of the Statue of Liberty (around 1885) were made from puddle steel, for example.
But it also had a lot of drawbacks. The quality varied from lot to lot; it depended on the skill of the people doing thepuddling and forging. It was labor intensive, needed a lot of room and fuel, and thus could not be cheap. There is no
economy of scale. If you needed more steel, you couldn't get it by making a bigger puddle furnace but only bymaking more.
Being a "puddler" wasn't a fun job either. However, you didn't have to do it for a very long time since you tended todie young. In more enlightened times this was seen as a bit wasteful.
Puddle steel thus was not really good enough for making large amounts of reliable things like all the steel
implements needed for railroads or elevator cables. With time and cunning, however, one could make remarkable
expensive objects like very good swords.
It's time for a revolution . But before I get to that, I need to look at a few more processes important before 1870.

Iron, Steel and Swords script - Page 404

Making Steel in Other Ways

1. The Brescian Process

You have carbon-rich cast iron and carbon-free wrought iron. It is not a very far-fetched idea to combine the two in someratio that results in a desired carbon concentration. Not too far-fetched, that is, if you know about the carbon and so on.
Back in 1500 people were not really sure if cast iron was essentially the same stuff as their good old bloomery iron.
Moreover, they were still confused by Aristotle and might have believed that steel is particularly pure iron. The idea of
mixing the two then is not so obvious, it is actually a bit outlandish.
It was done in the area around Brescia in Northern Italy, and Biringuccio gives it some room in his 1540 opus.
Brescian steel actually enjoyed some fame in the 14th - 17th century. The process was secret, of course, and is
still shrouded in some mystery.
The only question now is: how to do this? Just dunking a piece of wrought iron into liquid cast iron will produce
something like what's shown below, as a modern smith just found out:

Wrought iron imperfectly coated with cast iron as
obtained by "dunking"Source: Scott A. Roush in the Bladesmith Forum; Internet

It's not unlike dunking a banana into liquid chocolate. You now have a chocolate coated banana but the banana partof the composite is pretty much the same as before.
Well, you have to immerse your wrought iron for quite some time into the molten cast iron if you want it to turn into
steel. The old North Italians dunked their 15 kg blooms for four to six hours, indeed, at a temperature probably around
1200 oC - 1250 o C (2192 oF - 2282 oF) writes Biringuccio. The wrought iron will not melt at this kind of temperature andthe cast iron simply acts as a nice uniform source of carbon that can diffuse into the carbon-lean wrought iron. An ideal
situation for basic diffusion down a concentration gradients - from high to low carbon concentrations - as expressed in
Fick's famous diffusion laws.
For the temperatures and times given carbon atoms can cover a distance in the order of 5 mm. An iron bar 10 mm thickthen could get carburized rather completely up to the saturation limit of the austenite present at these temperatures.
This would be about 1,5 %; just look at the phase diagram above. Thicker pieces would have the 1,5 % carbon on theiroutside and a decreasing carbon concentration with depth, approaching low values after about 5 mm. Cutting thesepieces into smaller ones and repeating the process would produce homogeneous steel. Alternatively, forging with somefolding or piling could also result in good pieces of steel with an halfway uniform "good" carbon content around 0.7 %.
The Brescian process never caught on outside Northern Italy. It is easy to see why. Not only do you need to know a
lot of tricks, you also need money! It is an expensive process, not to mention that it is a dangerous (and secret)process. Immersing into, cooking in, and retrieving heavy iron pieces out of a large vat of liquid iron was hot andunhealthy work, prone to accidents causing major injuries.

Iron, Steel and Swords script - Page 405

Making Steel in Other Ways

2. Cast Steel from Crucibles

Blister and puddle steel was not very uniform and might still have contained some slag. Small but demanding objects
like the springs of clocks needed to be rather hard and very uniform, and the steel available was problematic. It was
Benjamin Huntsman (1704 - 1776) who finally hit upon the obvious: Melt the stuff, skim off the liquid slag and the solid
dross, add, maybe, a bit of this and that, and cast the remaining homogeneous steel into moulds.
Sounds easy, is difficult. First, you need to contain your liquid metal in a crucible, and that crucible must be able totake the heat - around 1500 o C (2732 oF) at the least. The same is true for the linings of you fireplace, kiln,
reverberatory furnace or whatever else you had in mind. So Huntsman applied himself first to making suitableceramics and pottery, and finally succeeded - around 1740 - to produce crucible steel.
Of course, crucible steel had been produced in the East already for at least 1500 years by then; I gave you two longmodules on this. But this wootz or bulad, as we call it now, was ultra-high carbon steel not good for many applications,and it was only made in small ingots.
Huntsman used larger crucibles and produced normal steel - the best there was in his time and the time after.
The local yokels didn't like that, of course, because it threatened their business model. Huntsman had to export all
the steel he made to France at first. Making crucible steel was also rather complicated. You had to make thecrucibles from special stuff, re-line your furnaces a lot, use a lot of coke to get it real hot, and so on. Eventually andgradually, however, crucible steel plus casting caught on. It was the German Alfred Krupp (1812 - 1887) who
perfected it. In the London world exhibition in 1851 he caused a sensation with his cast 2150 kg steel piece"The sensation of the London World Exhibition, thesteel block of Krupp"
Source: Bernhard Woischnik: "Alfred Krupp - Meister des Stahls".
1957. Illustrations from Rudolph Fust

The raw steel used was puddle steel. The achievement was logistics, as we would call it today: making sure thatone kind of steel was molten in 86 crucibles and then transported to and cast into the mould at exactly the righttime. More important than the making of a giant steel block, however, was that Krupp could make axles and wheels
for railway cars that did not break erratically all the time - and cannons that could shoot faster, farther, more often
and with far more power than the competition.
But now I'm reaching the time of the steel revolution around 1870, and this I will cover in the next module. Before I do
this, however, I like to ask a deceptively simple question:
How Good Was Old Iron?
How good was old wrought iron or steel? Good question. But how could we find an answer? Pretty much only bydestroying an old specimen. You can carefully bend an old sword a bit without destroying it but that only gives you alower limit of some property. You can state: it is at least as good as ... (some number) .. as far as bending isconcerned, but no more than that.
Looking at the microstructure would reveal a lot. This is destructive, of course but only for a small area. That's good but
you only get the microstructure from a small area either. Can you really extrapolate from an area at best as big as a ricegrain on the properties of a whole sword or cooking pot? Not to mention that the microstructure does you tell a lot,indeed - but not everything.

Iron, Steel and Swords script - Page 406

Then there is the phosphorous issue. All the way up there I stated that we will look only at "ideal" carbon steel. Real
iron and steel, however, contained other elements, too. Most important was sulfur (S) and phosphorous (P), causing red
and cold shortness, respectively. Sulfur was only bad but the problem could be kept under control. Phosphorous was
bad most of the time but it could also also be good - up to a point. It hardened carbon-lean wrought iron to some extent
but would not allow quench-hardening by martensite formation. It might have made steel more corrosion resistant,witness the ancient iron pillar in Dehli. Ancient smiths are reported to have liked phosphorous iron since it was easy toforge, something the modern smith Lee Sauder rediscovered. But then your steel might become brittle and break all of asudden when it got cold.
Pretty much all iron and steel before, let's say, 1800, could contain some phosphorous. If it was there, it tended tobe distributed unevenly because all the solid-state processes employed to establish a certain carbon concentrationand to make that concentration uniform, did not much influence the distribution of phosphorous. Phosphorous, likeall elements besides carbon and nitrogen, diffuses rather slowly and thus tends to stay wherever it was after the
final solidification.
Inhomogeneous phosphorous concentrations thus go a long way to account for the large spread in properties ofotherwise standardized iron and steel. The problem was eventually recognized in the 18th century. For example, a"Bergskollegio" in Stockholm, Sweden, banned the use of phosphorous-rich iron ore from certain mines formaking iron and steel. In fact, the revolution in steel making around 1870 tied to names like Bessemer, Siemens,
Martin and Thomas, encountered a lot of problems related to phosphorous. Overcoming these problems was the real
beginning of the age of steel.
With all these complications in mind, I ask once more: How good was real old steel? I should be clear by now that asatisfying answer could only result from mechanical testing of large pieces, in particular by performing tensile tests.
Vagn Buchwald actually succeeded in getting a bunch of old (nominally) wrought iron specimens that could be
pulled apart. Here are some of his results:

Yield stress and tensile strength vs. maximum
elongation forthree kinds of old wrought iron from 1750 - 1800
Source: Constructed from tables 11.210. - 11-23 as given in
Buchwald's 2nd book (p 438-441

The wrought iron came from girders taken out of old churches. The pertinent data are:Bærum: Iron made in the Bærum iron works and used in churches in Hatting and Barrit.
Norwegian : Norwegian iron of unclear make used in the churches St. Petri, Copenhagen and in Stouby.
Ulefos / Fritzøe: Iron made Ulefos / Fritzøe and used in churches in Odder and Jørlunde
Not to make too fine a point: This is shitty stuff! There are tremendous fluctuations and some specimen were perfectly
brittle. And no! The Scandinavian folks were not just behind the rest, quite the opposite. They were typically at theforefront of iron and steel technology.
Iron, Steel and Swords script - Page 407

Vagn Buchwald does not give the impurity concentration data of the specimen but notes that "good" wrought ironshould have a yield stress of 160 MPa, a tensile strength of 280 MPa, and a maximum elongation of 36 %.
Phosphorous and slag inclusions go a long way in explaining the bad results. Some of the fracture surfaces
evidently showed the typical shininess of phosphorferrite grains and slag inclusions were evident on microstructure
investigations. Some sample also showed cold shortness.
Could the average steel be better than this run-of-the-mill wrough iron? Yes, because people might have picked thewrought iron for making it with some care and put more labor and cunning into the forging. However, it could nothave been routinely excellent given the problems with the starting material.
I'm not aware of any tensile test results from much older bloomery iron or steel but it is unlikely that they would bemuch better.
Buchwald has investigated more samples than shown here with similar results. We might take then this as typical forcheap and bulky structural iron. But is it typical for fine steel swords?
Probably not. We can safely assume that more cunning and care was put into making fine objects. But we cannot avoid
one major conclusion: Only the very best swords, forged with utmost cunning and a large dose of luck, could live up to
the potential of the basic composition of the steel used. Most, however, must have been inferior. In other words: A
modern 0,7 % carbon steel object will outperform pretty much all old objects with that kind of composition.
Don't believe for a second that I'm trying to put the old iron masters and smiths down for making shitty objects here.
The reverse is true. Given the problems they faced, it is simply marvellous what they could make when they reallyapplied themselves. They wrought unbelievably good and fancy stuff - but no miracles.

Iron, Steel and Swords script - Page 408

10.5.3 Making Steel after 1870
A Few General Words
The year 1870 is as good as any in the second half of the 19th century to mark the turning point in steel production or
simply a major revolution . And if I use the word "steel revolution" I include wrought iron and cast iron because if you
revolutionize steel production you must start with cast iron and wrought iron.
The revolutionizers of steel in the second half of the 19th century were more concerned about the quantity of iron andsteel produced and not so much about the quality of the product. The industrial revolution taking place right then called
for unprecedented quantities of iron and steel. Just consider how much of the stuff you needed in addition to everythingelse when you set out to establish a railway system! "Railway", by the way, translates to the German "Eisenbahn"(=iron path) or the French "chemin de fer" (=iron road) for good reasons.
There was no problem with increasing the production of pig iron. Blast furnaces could be made bigger and bigger andeasily produced tens or even hundred of tons of pig iron per furnace and day. The costs actually decreased because you
had substantial economy of scale effects. The big problem came with the fining needed. The available processes formaking wrought iron by "fining" or steel by puddling, cementation, crucible, whatever, produced a few hundred kilograms
or at most 0.7 tons per unit and day. If you wanted to increase production you needed more furnaces; you couldn't makethem bigger. There was thus no economy of size and that means no cost digression. Right now we have a similar
situation with respect to refining raw silicon needed in exponentially increasing quantities for solar cells.
Bessemer consequently stressed that he could manufacture malleable iron and steel without fuel, i.e. he emphasized acost issue and not that he could make better steel. But as ever so often quantity and quality is interrelated, and the new
methods impacted the quality of the products just as much as the quantity / cost issue. You certainly cannot build arailroad if the material costs of the rails are prohibitively large. But you also cannot operate a railroad for very long if there
are too many gruesome accidents because rails fracture too often due to the fluctuating quality of the iron / steel. And
you don't even need to consider erecting highrisers if there is the slightest doubt about the quality of the elevator cables.
The final result of the steel revolution was that the quantity of quality-guarantied steel produced in new ways started to
grow exponentially ever since. What happened is that the steel revolution allowed new products that in turn caused
major changes of their own. Reliable, safe and cheap railroads allowed to transport people and products far more quickly
and cheaply than before, which allowed to open up vast stretches of so far undeveloped areas like the "West" of theUSA, mixed people of all kinds of backgrounds, bred social problems and improvements, and so on and so forth. The
car industry is unthinkable without steel. In short, an avalanche was started that is still gaining momentum and power just look at the development of the World's steel production below.

Worldwide Iron / Steel production since 1870
Source: Blue curve: "Werkstoffkunde Stahl"; Red curve: Internet alarge

In march 2018 the President of the USA, one Donald Trump, imposed import taxes on steel. One of the reason isthat China now dominates world-wide steel production. According to newspaper, the production capacity is 2.4
billion tons (or be 2400 million tons in the figure above), with China accounting for about one half. However, only 1.5
billion tons are needed, resulting, as always, in some kind of trade war if not a real one.
One cannot possibly overestimate the importance of steel for the development of humanity in the second half of the 19th
century and most of the 20th century. Just a very few reminders. Without affordable steel, having specific and reliable
properties, you would not have:

Iron, Steel and Swords script - Page 409

Buildings with more than 5 floors. Elevators need steel cables.
Railways, large bridges, cars, big ships or simply affordable transportation.
No airplanes either. While they are mostly not made from steel, they couldn't be made without steel tools. They
also need some crucial steel parts e.g. in the engines and the landing gear.
Same thing for electronics. Chips are made from silicon, alright, but chips are made with plenty of steel tools.
Without steel no tractors, harvesters, plants for making fertilizers, and thus no agricultural revolution. No
agricultural revolution and most of us would be dead or would never have been born because of world-wide
famines.
No big cannons, machine guns, nuclear reactors, atom bombs without steel.
And so on.
However, mastering steel is not sufficient for starting an second industrial revolutipon. It is just the first major ingredientdefinitely needed. The second absolutely necessary ingredient for the industrial revolution was cheap energy in the formof coal and later oil plus energy transferring devices like steam engines or gasoline motors. The third - and that is asurprise for most - is rubber. Think about that yourself and you will see why.
If you have all that, you can finally go into electricity and make the really big changes.
Of course, a lot of other things happened around 1870 and later that also changed the world in major ways for better orworse. The Germans invaded Gaul (then called France), for example. Foremost in my mind, however, is the scientificrevolution giving us, for example, electricity. However, no electricity without steel. Things are interconnected. This is as
trite a statement as one can make, so let's stop here and just give a very brief look at some of the key breakthroughs
made in the steel revolution. I will do that by looking at some of the guys whose names are attached to thesedevelopments. Biographical details can be found here.
This is doing grave injustice to many other scientists and engineers. All big names
in science and engineering owe their success to a smaller or larger extent to theircolleagues, including the already dead ones. There are no true scientific giants.
Some scientists and engineers are (intellectually) considerably taller than the
average but they are not giants. They stick out of the crowd because the stand on
the shoulders of all the others that form a kind of intellectual pyramid.
More details about the "steel revolution" and other key people involved can be foundin the link.

Science Link
Steel
Revolution

The Bessemer Process
On August 13th, 1856, Henry Bessemer presented a paper entitled: "The manufacture of malleable iron and steel
without fuel" to the British Associations for the Advancement of Science, an important organization. The paper describedthat by blowing air through molten pig iron, the carbon, silicon and manganese in there were removed, making the ironmalleable.
Before that, between Oct. 1855 and Feb. 1856, Bessemer had filed for 3 patents relating to running air or steam over or
through molten pig iron. What exactly was going on on his mind, what he found out by his own experiments, and towhat extent the was aware of the work of others, is a long and muddled tale; see the link for some details. The
obsession of Bessemer and all the others with filing plenty of patents just makes clear once more: the steel
revolutionaries were primarily concerned about making money and not all that much about advancing science andengineering.
Bessemer must have known the basics about the role of carbon in iron and that it could be removed by oxidationeven so he coyly pleaded ignorance of iron metallurgy. Note that his paper emphasizes that he can do things "without fuel". Note also that the idea of blowing air through a large quantity of molten cast iron may not be seen as
all that innovative. It carries a few connotations, however:
1. You need real power for blowing and something better than bellows for producing the air stream.
2. You need novel high-temperature prove hardware because the temperature went up quite a bit from themelting point of pig iron.
3. You need guts because the idea is preposterous. Blowing cold air through liquid cast iron will simply solidify
it, of course. At least that's what one would expect.
The third point is what most people thought. Bessemer claimed that the melt actually get's hotter! Not quite
believable but Bessemer was right. The energy released by all the oxidation reactions was sufficient to keep the
stuff liquid even so the melting point goes up to a whopping 1538 oC (2629 oF), making point 2 hard to meet. "All theoxidation reactions" include in particular the oxidation of silicon and phosphorous contained in many but not all pig
irons because these reactions deliver a lot of energy, and the oxidation of iron itself. Here we have a first hint thatthe success of Bessemer's process may depend critically on the precise composition of the pig iron.
In the 1856 meeting Bessemer did manage to convince a number of iron masters present that his invention was ofinterest. Licenses were taken and large-scale experiments were started right away. After all, there was a real potential
to "fine" tons of pig iron within 30 minutes or so, a tremendous increase in productivity.
Within just a month, the honeymoon was over. A big problem had emerged:

Iron, Steel and Swords script - Page 410

The Bessemer process produced
shitty iron & steel
The iron produced by using Bessemer's methods was completely de-carburized wrought iron but cold short as well
as hot short, and "oxidized to a cinder"! There were a number of reasons for this severe disappointment, details arehere.
In short: The process had worked on a kind of lab scale but not on a production scale. The major reason was that
normal English ore (in contrast to the "lab grade" ore Bessemer used) contained phosphorous and the Bessemer
process could not get rid of phosphorous.
This problem could be circumvented by using phosphorous-free ore, making suitable pig iron. Unfortunately, English
ore didn't qualify. That caused caustic comments by Bessemer's contemporaries. For example J. Percy, arenowned authority on iron and steel making, remarked in 1864: "....it is only pig iron practically free from
phosphorous that Bessemer can deal with satisfactorily and such pig iron forms merely a fraction of the total
produced in this country. It will be time enough for Mr. Bessemer to sneer at puddling when he can show how thatlaborious operation may be dispensed with. He has not yet done so."
Swedish pig iron "worked", however, as was more or less accidentally discovered during the frantic work Bessemer
and others invested for about 18 month. It just tended to "blow cold" (not staying liquid) because besides
phosphorous it also lacked silicon and thus a booster of temperature.
The next problem that came up was the production of steel. Taking out the carbon completely (i.e. making wroughtiron) was no problem anymore but there was no way to stop the process at precisley the the right moment to retain
a defined concentration of carbon as needed for steel. The solution was to re-carburize the melt with "spiegeleisen",a manganese - iron - carbon alloy that some Germans made. Robert Mushet, a big name in iron / steel, had
patents on this and some cooperation was needed. Spiegeleisen (literally "mirror iron"), via its manganese, also
took care of the sulfur and thus of hot shortness
Finally, Bessemer could produce good iron / steel also with "native" (Lancashire and Cumberland) pig iron that
happened to be low enough in phosphorous and sulfur and the first mass production could start.
Bessemer converters became a common sight and accounted for about 30 % of the World's iron / steel production
between 1880 and 1900. The converter itself was a marvel of engineering; here is a picture of a real one. The picture
below shows drawings from an old illustration of uncertain origin.

Bessemer converter and process
Large picture of a real Bessemer converter
Large picture with old drawings of all kinds of converters
Source: Internet open access; obviously from an old book not
identified.

What we see is:
A: A rendering of the converter.
F: The ladle into which the finished iron is poured.
B: The converter being filled with liquid pig iron.
C: Blasting air through the liquid.
D: Pouring the finished product into the ladle.
Between C and D: Details of the bottom with the tuyeres.
It goes without saying that the lining of the Bessemer converter with some refractory material was crucial. The
ceramic refractory bricks must have been able to take the heat / high temperatures and the extremely corrosive
environment without having to be replaced too often. Injecting the air with sufficient pressure to make it through theIron, Steel and Swords script - Page 411

heavy liquid, and controlling this to some extent, wasn't an easy task either.
More details about the Bessemer process can be found here; and here is a big picture of the real thing.
The phosphorous problem was "solved" by using phosphorous-free pig iron. That was not a real solution, of course. The
real solution can be found below under the heading "Thomas Steel", an important variant of the Bessemer process
covered below.
Around 1892 the total amount of iron and steel made with the Bessemer process and the similar Thomas processsurpassed the production by puddling . The data below show this. They also show that another invention, theSiemens - Martin process, overtook Bessemer in 1900 and everything else in 1910.
We also see that making steel with Huntsman's crucible process or variants thereof declined synchronously withpuddling. Note, however, that all the new processes contain the essence of the crucible process: they produced
liquid iron or steel that could be cast.

Production technology development for iron and steel
Source: Blue curve: "Werkstoffkunde Stahl"

Before I deal with the Thomas process and the Siemens - Martin process, I will give another quick look on the scaleof the iron / steel production in the late 19th century. The "big" picture shown above gives the impression that notmuch iron and steel was produced between 1870 and 1900. That is wrong! It's just a matter of scales! So let's lookat what really was going on in those years:

Early iron / steel production in some key countries
Note logarithmic scale and change of time scale for
Russia and Japan
Source: Redrawn from the curves given in Wertime's book.

All curves increase linearly on average, indicating exponential growth. All curves have roughly the same slope,indicating a ten-fold production increase about every 20 years or a yearly average growth rate far in excess of 10 %.
You just can't install all the infrastructure needed more quickly, it seems.
1892, when the Bessemer / Thomas processes overtook the puddling process worldwide, Great Britain alone
produced about 3 million tons of iron / steel. In 1870 it was about 500 000 tons, still quite a bit - and roughly 50 000
tons were already made with the Bessemer process that came on-line just about 10 years earlier. It just takessome time (not to mention lots of money) to build he heavy-duty infrastructure required with many novel components
and considerable risks for the investors.

Iron, Steel and Swords script - Page 412

The Thomas Process
Many iron ores contain some phosphorous and so does the pig iron smelted from them. Blowing air through liquid pig
iron obviously did not remove the phosphorous. It neither bubbled out as a component of a gas like carbon, nor did it
become part of slag or dross swimming on top. The reasons for this are actually quite involved; here is a short
discussion.
If you want to get rid of the phosphorous, you must make it part of some slag. The Bessemer process did produce slag.
The oxidation of iron produced FeO, known to us by now as wüstite, and the oxidation of the silicon produced SiO2.
Together you get the ubiquitous fayalite - wüstite slag well known from millennia of smelting. Phosphorous would beoxidized to P2O5 during the air blast but would not be able to compete with the SiO2 in the reactions needed for forming
the stable slag ingredients. It would be reduced again by the CO formed in large quantities and then remained in the pig
iron.
The only logical way to remove it thus was to "catch" it with something else. Limestone (calcium carbonate, CaCO3)
added as flux could do the trick but it would also corrode the refractory silica-bearing bricks lining the converter.
With hindsight (and some knowledge of high-temperature chemistry) it is relatively clear what happened but in 1870
things weren't that clear.
For obscure reasons, the words "acidic" and "basic" come up a lot in this context. What that means is bisected insome detail here; suffice it to note that the normal bricks, always containing some silicate (something ending with SiOx
) were acidic and could not deal with basic limestone or quicklime.
What kind of brick should one use for the lining? Without compromising the primary job of the lining like mechanicaland chemical stability in a very hot and corrosive environment. Not to mention that platinum bricks (they migt work)or something else very expensive wouldn't do either. One Sidney Gilchrist Thomas, a civil servant with an interestin iron making and metallurgy, took the bit in his teeth and set out to solve the biggest problem of the 1870 iron andsteel industry. He enlisted the help of his cousin Percy Carlyle Gilchrist, a chemist who worked for an iron making
company. They worked hard but had no luck for several years. Eventually the iron mill Gilchrist worked for gavethem some support and they started experiments with a small lab-type converter, trying all kinds of materials they
selected on "theoretical" grounds. They finally succeeded, announcing the Gilchrist - Thomas process during ameeting of the Iron and Steel Institute in London, March 1878.
They didn't hit it off a first. Almost nobody was ready to believe that two amateurs had beaten scores of professionals
who worked hard at solving the biggest mystery of the iron industry in the 1870ties: how to process phosphorous
containing iron. Finding a way was a big issue because it would allow to use the phosphorous-bearing ores that formed
the vast majority of the known ore deposits.
Believes and doubts are one thing, an actually working process is another. The Gilchrist - Thomas process worked - andfame and wealth eventually descended on the two.
What was the big trick? It looks actually deceptively simple. Just line your Bessemer converter with bricks made fromdolomite, a calcium magnesium carbonate (something like CaMg(CO3 )2). Dolomite is a rather common rock; parts of
the Alps consist of it. "Calcining" (heating) it produced calcium and magnesium oxides. The stuff was ground up, mixed
with dry tar, pressed into bricks and used for lining a converter. Now add a fitting amount of burned lime ("quicklime") as
flux to your molten pig iron, and your phosphorous will end up as calciumphosphate (Ca3 (PO4)2 in the (easily
removable) slag that forms now - while your lining will not be attacked.
It was actually necessary to have quite a bit of phosphorous in the melt for the process to work. The Gilchrist Thomas process wasn't quite that simple, after all. Once more, success depended in doing a lot of things just right.
The Thomas process became far more important than the Bessemer process since 90 % or so of the world's pig iron is
phosphorous rich. Don't be deceived by the percentage data above where the Thomas process has about the same
percentage as Bessemer. In 1960 a certain percentage meant a hell of a lot more production in tons than the same
percentage in 1920, for example.
The Thomas process allowed Germany, Sweden, France and others to use their ore deposits for making large quantities
of iron and steel. The production peaked around 1910, 20 years after the Bessemer heydays - and by then the world
production had increased at least 10 fold!
As an unexpected fringe benefit it turned out that the phosphate-rich slag was an excellent fertilizer. "Thomasflour" was the first synthetic fertilizer and found a big and receptive market. It was still used in the 1950ties and60ties in the farming town I grew up in. Here is a commercial from around 1940

Iron, Steel and Swords script - Page 413

Advertising for Thomas flour
However, while Bessemer and Thomas most certainly were great inventors and remarkable personalities, who left anindelible mark on the iron and steel history, the world at large could have done without them. The competing Siemens Martin process came in only a little later and was so much better that it dominated the industry for a long time as thepercentage figure above nicely demonstrates.
The Siemens - Martin Process
The Siemens - Martin Process is also known as "open hearth" or "regenerative furnace" process. Let's start with
Mr. Siemens' contribution. The first thing to know is that there was not just one Siemens involved but a tightly knit big
bunch of them. The two Siemens brothers most important in this context are :Carl Wilhelm Siemens ; later Sir William Siemens (1823 – 1883, knighted 1883) left for London in 1840 as anagent of his brother Werner, the founder of what is now Siemens Corporation. He stayed in England and becamea knighted British subject. He is the one mostly associated with the Siemens - Martin process.
Friedrich August Siemens (1826 - 1904) joined his brother Wilhelm for a while in England. He went back toGermany in 1857 or so, employing the new technology with great success in the glass industry.
Sir William was scientifically minded and used his knowledge to come up with the regenerative principle for
furnaces. Or did he? During the crucial time around 1847 his brother Friedrich worked with Wilhelm; and it isactually Friedrich who got a patent. If Wilhelm's or Friedrich's contributions was more important I do not know. The
Siemens' brothers however, never produced steel themselves with their invention.
The Martin's (father an son) in France were the first ones who got a licence, and their work was instrumental forfinally coming up with a working Siemens - Martin furnace (see below).
What is it all about? Well, at least Wilhelm's mind was full of the new insights from a scientific revolution in the field ofwhat we now call thermodynamics , tied to names like Carnot, Clapeyron, Joule, Clausius, Mayer, and Thomson. In
particular he accepted the new and revolutionary notion that heat was not a substance but a form of energy.

Iron, Steel and Swords script - Page 414

As far as I can make out, he (or both brothers) used the new scientific knowledge to figure out answers to two
simple questions:
1. How can I produce very high temperatures ....
2. ... with as little energy = fuel as possible?
One could now calculate how much you can achieve with a given amount of energy. In reverse, it also was possible
to calculate how much of the energy actually used for achieving something like the melting a certain amount of iron
was actually wasted, not really needed. It must have become clear to Siemens that a lot of the energy used in ironprocessing simply went down the drain; it was wasted. What could be done about this?
The catch word was and is"regenerative energy". That means to employ energy usually wasted for doing
something useful. You may brake your car electrically for example, using the energy that otherwise just makes thebrakes hot to charge a battery. Or you use the energy still contained in your hot motor exhaust to run a turbo
charger. At the time of Wilhelm and Friedrich the meaning of the term was the same but in addition it also meant tobe generally energy conscious. You can do that only after the concept of energy is clear.
Siemens realized that in burning regular fuel for producing heat, a part of the energy produced is used to heat up thefuel itself. There is not much you can do about that as long as you burn solid matter - wood, charcoal, normal coal,coke - but if you used the town gas that resulted from coke making, you could pre-heat it for free if you used theheat contained in the hot exhaust gases of any furnace treating pig iron.
The Siemens brothers, in essence, came up with the idea of a heat exchanger. Run the hot exhaust gases througha chamber filled with stacked bricks, and you heat up the bricks. Then run your process gases through these hotbricks and you heat up the gases. Have two heat exchanger units and switch back-and forth from one to the other.
Here is the classical drawing showing what the whole contraption looks like:Old drawing of a Siemens - Martin regenerative
furnace
Large schematic picture
Source: All over the Net

I have looked at that drawing many times and could never make head or tail of it. If you can, you have my heart-felt
congratulations. If you cannot, you might profit from activating the link to the large schematic picture. There the concept
is easy to understand.
Let's just say that a working Siemens - Martin regenerative furnace (always of the reverberatory kind) could get asubstantial mass of iron / steel not only up to the melting point of pure iron at 1538 oC (2629 oF) but up to 1800 o C(3272 oF)! And it did so with rather little fuel. That's an impressive achievement - but is it useful? What is theadvantage for fining pig iron and making steel? Can you see it?
On the surface it is not all that obvious why the Siemens - Martin process is so much better than the Bessemer andThomas processes. Looking a bit more closely, however, produces a long list of advantages:
You can take the carbon out of pig iron now by various means because the stuff always stays liquid anddoesn't solidify with decreasing carbon content. There is no entrapped slag either because of this.
Same thing for silicon, phosphorous and so on. In essence you can do standard "chemistry" because
everything is always liquid.
You can put stuff into the liquid for the same reasons. It will distribute quickly and uniformly because
everything is liquid.
In particular you can put scrap iron into the liquid. That is an enormous advantage because it allowed for the
first time the recycling of scrap iron, of which rapidly increasing amounts were generated.
You can take a spoonful out at any time and analyze it (quickly) in the on-site lab. That told you what kind ofmix you had concocted, and thus also what you had to do to get what you want. Too little carbon? Throwsome in. Too much carbon? Blast some air into the stuff. Too much phosphorous? Add some quicklime. A
little manganese on the side? No problem Sir; coming right up.
Iron, Steel and Swords script - Page 415

No more cooking blind and without tasting!
You didn't burn (oxidize) as much iron as in the other processes and used less fuel - that means less moneyis needed.
Siemens - Martin furnaces could be made bigger and bigger without much problems (unlike the Bessemer /Thomas converters that needed to be moveable). There was economy of size! Capacities of 50 tons to 100
tons were the rule, but even 500 tons were possible; just look at this monster. Compare that to the 5 tons or
so of a Bessemer or Thomas converter
A few details (including the problems) can be found here. But now it is time to progress to the Martin's.
The Internet offers very little about Pierre-Émile Martin and his father François Marie Emile Martin - except that theSiemens - Martin furnace translates to "four Martin" in French (of course). I'm not going to help the French by providing
extensive insights into the role of the Martins but will give only hints.
The Siemens brothers actually could not produce liquid steel since in their prototypes the linings of the furnace
melted around 1600 oC (2912 oF). If you look at their contraption, it's not something easily and cheaply build and rebuild. Experiments must have been expensive and slow. Some experience with iron and steel technology (that thebrothers did not have) would also have been quite useful.
Pierre-Émile Martin and his father François Marie Emile, two French iron and steel experts, liked the concept, tookout a licence and began to work. They solved the "melting brick problem" by using better material, and they
probably added a lot of other improvements.
The Martin's succeeded in making very good steel with the regenerative furnace; their product was awarded a (thenvery prestigious) gold medal at the 1867 World Exhibition. Siemens got one too for the invention of the furnace! The
Martin's also filed patents of their own and - unavoidably - had them challenged by some Siemens. The ensuing
litigation reduced Martin to virtual poverty while others were making large profits using "his process". Finally, when
Martin was 83 years old, the Comité des Forges de France (“Ironworkers Guild of France”) instituted a fund for him
that was supported by all of the principal steelmaking countries. Barely one week before Martin’s death, the Iron andSteel Institute, London, honored him with its Bessemer Gold Medal.
The Siemens - Martin process dominated the World production of iron / steel for more than 80 years. Of course, it also
had some drawbacks (like being slow) and after about 1970 "oxygen-blast steel" and "electro steel " took over; seeabove.
Oxygen-Blast and Electro SteelWe are now entering the era of modern steel making and I will keep it short.
Oxygen-blast steelmaking (also known as "Linz-Donawitz-Verfahren steelmaking" or "oxygen converter process")
simply blows oxygen and not air on the liquid pig iron. Linz and Donawitz are Austrian cities, and Austrian companies
first employed this process. The main guy pushing this technique was the Swiss engineer Robert Durrer (1890 – 1978),who studied and worked as a professor at the Berlin Institute of Technology until 1943.
Well, oxygen should be more effective than air, that's obvious, but how to get the stuff in quantity and cheap? Carlvon Linde (German) made it possible by extracting liquid oxygen from liquid air by distillation in 1895; around 1930
the process provided plenty of cheap oxygen. But that's a long story in itself. Suffice it to say that the Linde Group,
founded by Carl von Linde, is presently the world's largest industrial gas company.
After the second world war, the Austrian Iron and Steel mills in Linz, making the modern kind of the Ferrum
Noricum, were majorly kaputt, owing to allied bombs. The decision was to rebuilt by developing and utilizing a newprocess: oxygen blasting. As simple as is sounds, it took some dedication to overcome the problems. The firstexperiments 1949 (my birth year) yielded this result: "Der hergestellte Stahl war miserabel" (the steel produced was
abysmal). The rest is history.
You can use all the methods covered above, e.g. blow oxygen through a Thomas converter and so on. There are several
advantages to using oxygen instead of air, suffice it to mention that you do not get nitrogen into the steel, typically not agood thing, and that oxygen blasting makes processing considerably faster and cheaper.
Electro Steel is made in an electric arc furnace. The principle is simple. Put graphite electrodes (usually three) rightover the (solid or liquid) pig iron and run a substantial current from the electrodes to the iron. For doing that you need toignite an electric arc between the graphite and the iron, and there it gets rather hot. Temperatures up to 3500 °C ( 6332
°F) can be reached, allowing alloying with very high melting point metals like tungsten (W) or molybdenum (Mo).
In essence, you feed the energy needed to increase the temperature of the iron into the system by electrical means andthus with very high efficiency.
You can blow in some oxygen to take carbon out, remove other stuff by forming proper slags, dissolve scrap ironand so on. The process is faster than the Siemens Martin process, and a furnace can be far more compact,
allowing easier access and so on.
However, you better have a sizeable electric power plant nearby. An electric arc furnace is not something you canplug into your kitchen outlet, it needs serious juice for running. Also, you better know how to handle powerfulelectric arcs; not an easy thing to do. It's like trying to control a flash of lightning. It is not very cheap either.
Electric arc furnaces nowadays are typically used for producing expensive high-quality steels. 29 % of the steel
produced world-wide comes from electric arc furnaces right now - about 450 Mio tons!

Iron, Steel and Swords script - Page 416

10.5.4 Making Steel Things
Introduction
Yes, I know - this is supposed to be about swords. Nevertheless I will digress from the topic for a short. time. Swords
are fascinating objects for many reasons; good ones and not-so-good ones. But fascinating things are often not very
useful, consider for example atomic bombs, black holes, Lamborghinis, Las Vegas, opera, or (insert "it girl" of yourchoice). So let's take a little time out and look at a few useful iron or steel objects here.
In order to get an idea of what people really wanted from their iron monger, let's look at what was going on in
Schmalkalden around 1740. Schmalkalden is described in the link; it was a center for mostly "civilian" iron and steel
products for a long time.
There were around 1000 artisans working with iron and steel in the town; for 912 of them I will give details:
No. Artisans% (rounded)

Product200

22Knife (blades)

180

20

Nails

80

9

Awls (for shoe makers, general leather / heavy cloth working)70

8

Locks, padlocks

60

7Horseshoes, simple weaponry

50

5

Tongs, hammers, other tools

50

5pair of snuffers, scales, fittings

50

5

Gun barrels, small arms

40

4

Files

30

3

Chains20

2

Scissors

20

2Special knifes

15

2Special locks for doors etc.

101Curry combs for horses

10

1(Pitch) forks

8

1

Jew's harps

50.5

Pans, kettles

5

0.5

Special needles for shoemakers, sailmakers, ...

5

0.5

Hammers2

0.2

Thimbles20,2

Tools for blood-letting

Source: Buchwald

Quite amazing, isn't it? Eight jew's harp makers, whatever that is? A very simple and affordable instrument (see below)that needed some good springy steel. Don't forget that in those good old times the only music most people enjoyed was
the one they made themselves.
Did you notice that major products are missing on this list? Normal needles for example. Considering that very close to
100 % of all females were constantly making and mending clothes, needles were major items in these times. Not tomention farm / gardening implements like scythes, sickles, pitchforks, plowshares, coulters, spades, shovels, and soon.
Obviously that stuff came from other specialized places, just as swords and armor.

Iron, Steel and Swords script - Page 417

Jew's harp (German: Maultrommel=mouth drum) andhow you play it
It is not surprising that knifes are on the top of the list. Everybody needed a knife all the time as a matter of course.
While a knife blade could be just as complex as a sword blade, they usually weren't. Damaging or breaking yourknife was not a life-and-death matter. You got a new one (possibly making it yourself from a piece of scrap) or you
had it fixed.
It is, perhaps, a bit surprising that nails are No 2. So let's start with these unassuming things.
Nails and Screws
Just think of raising big wooden constructions like houses, barns or boats without nails. You can't have a decent
crucifixion either without these implements. As long as most of humankind made things from wood, including the ships
Columbus used for not finding India, the ships Vasco da Gama employed for actually finding it, and all the ships used for
centuries by all and sundry to bring the goodies robbed from India, America and so on back home, nails were ofparamount importance. They still are.
Same thing, just much later, for their cousins: screws, rivets, clamps - you name it. Modern life is unthinkable withoutthat stuff
So make a nail. Actually not just one but lots. Forging nails from a piece of iron with a hammer in your smithy is not
so easy, especially if you want relatively small ones with standard sizes. Going down in size you reach a point
where you are better of by making wires first and than use cut-to-length pieces on which you put a "head".
That makes clear that making the head is the problem.

Old nailsMore Roman nails (large format)
Source: Roman nails of Inchtuthil; a Roman legionary fortress in
England, where 7000 kg of nails have been found. The nails fromaround 1500 were found by Thorsten Straub with a metal detector in
Germany.
Iron, Steel and Swords script - Page 418

To make a long story short: Nails were hand-forged from thin wrought iron rods with square cross sections until about
1800. A tip was drawn out, then the rod was cut a bit above the thinner parts, stuck into a suitable hole on the anvil
followed by flattening the thicker part into the head. In the picture above the Roman smith did far better than the
medieval one, who either didn't have the skill or didn't care in this case. Maybe the Roman guy used the iron oboli forthat.
I'm not going into the modern methods starting around 1800, when using wires to make "cut nails" in some machines
more or less automatically took over.
Let's stop the nailing business now and go on to screwing. Whenever you do that from now on, consider first how
you, personally, would have made that screw. Think!
I'm rather sure you are going to screw up on this. Screwing around with all types of screws (wood screw, machine
screw, set screw, ...) is far easier than to make one.
You need a machine - some kind of lathe - for doing this, and that's why screws only came up at the end of the 17th
century. Screwing and screwing up, however, are much older techniques.
Needles and Awls
Needles are some of the oldest tools of humankind. A bit larger and without an eyelet you have an awl. With properly
cut spiral grooves you have a drill but that had to wait.

Ancient needles. The real ones are bronze needles
from the Heraklion museum
Needles, awls, and so on, needless to say, should be made from hard steel. That's not so easy, especially if you wantto make small ones with an eyelet.
One idea thus was to make needles from wrought iron and then to turn it into steel. Another one - for finer needles was to use steel wire, anneal it to soften it, work it, and harden it again.
The only point I want to make is that producing a needle was an extremely laborious process. Not only did you haveto work on a fine scale, with tiny hammers, punches, etc. you had to go through many steps before just one needle
was made.
Since there are all kinds of needles for all kinds of jobs, not to mention awls and other related stuff, artisans
specialized on just one basic type: needles for sewing, sailmaking, shoemaking; needles for surgeons, glovers, bag
makers, bookbinders. And so on. The Schmalkalden crowd was not doing much needlewise, just some of therougher stuff. Schmalkalden wives such had to needle their husbands to go and exchange some of their stuff forgood sewing needles from the specialists elsewhere.
Wire
Wires are extremely useful, especially for electricity. Having thin gold or silver wires helps in making fancy jewelry. Butiron and steel wires are also useful. Not just for the hilt of your sword but for many other things. Foremost, perhaps, isthe making of chain mail or just normal chains. More important for most people, however are the normal things you
make from wires: nails, needles, pins, awls, fish hook, sieves, musical instruments, suspension bridges, elevators,
cranes, sailing boats, ...

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Mail shirt remains; Berlin area, around 300 AD
Pictures of Roman Chain mailSource: Photographed in Berlin, Neues Museum

Chain mail failure. The mail was medieval in thiscase.
Source: Photographed in the Stockholm museum

How does one make a wire with some given diameter? I'm rather sure that more than 99 % of all humans living now
do not have the faintest idea. The all should go an visit the wire museum in Altena, Germany. There you will findout.
You do it by drawing a wire with a larger diameter through a die. You start with a relatively thick forged "wire" thatis as uniform and free from slag as you can make it. Than you draw it through a die, decreasing its diameter andthus making it longer automatically. Then you repeat the process with a somewhat smaller die. Then you repeat theprocess with a somewhat smaller die. .....
Wire drawing is a marvelously simple process - provided you do a lot of things just right.

Wire drawing. Only the middle approach is "just right"
Iron, Steel and Swords script - Page 420

The force you draw with must not be too large. More specifically, the stress employed (force per crosssectional area of the wire) must be lower than the yield stress. Otherwise you are just pulling out the wire
just formed.
The die must have an opening that tapers with just the right angle (around 20o in most cases). Wrong angle
and the permissible drawing forces will not be sufficient to do anything.
The reduction in the wire diameter can only be modest. A factor of 1.4 is already quite large. If you want finewires you must do it in many steps, each time reducing the diameter just a bit
The points made above follow from experience but also from (rather involved) modern theory. They are not negotiable. In
addition, there are also some practical concerns:
Your die should be very hard with a polished surface in order to reduce friction. You are also well advised touse some suitable lubricant while drawing.
The drawing forces may be considerable. A yield stress of 200 MPa (wrought iron) calls for a drawing stressof around 100 MPa. For a 2 mm diameter wire this transforms to a force of (200 · 106) · (3.14 · 10 –6) (N/m2) ·(m2)=614 N ∝ 60 kg. In other words: You must pull with almost "all your weight" or use some machinery as
shown below.

Wire drawing
Source: Left: unidentified old book in Nürnberg museum library; Right:
Biringuccio 1540 woodcuts showing use of "machinery" for wiredrawing.

For making dies you use the hardest steel available. Precision was everything and it is no accident that the term"die maker" is still the name for professionals who can make all kinds of precision tools.
Wire pulling was skilled and very hard, not to mention boring work! Of course, the process of wire drawing deformed
or cold-worked the material and thus some work-hardening occurred. Some post-treatment of the wire may havebeen required. And so on and so forth. Nevertheless, wire drawing is an old art. The Vikings did it and probably otherand older cultures, too. Here are some old dies:

Old dies for wire drawing
Left to right: Magdalenenberg, Kärnten, Austria (the"Noricum"), around 50 AD; Vikings, Haithabu,
Germany, around 1000 AD; Vikings, Oslo, Norway,
around 1000 AD
Iron, Steel and Swords script - Page 421

Source: Photographed in the "Deutsches Drahtmuseum" (German wiremuseum) in Altena, Germany

Farming Implements: Scythes, Sickles, Plowshares
A farm then (and now) needs a lot of iron / steel implements. Hinges and latches, knifes and general tools, rings for thenose of the steer and all the other gear around animals, and so on and so forth. All this stuff could be made by the local
black smith from the wrought iron he procured from the nearest smelter.
But there were also a few special things that needed expert makers and special iron / steel. For example:
Scythes and sickles
Plowshares and coulters.
Pitchforks, spades, rakes.
A scythe looks simple but is a complex tool. If somebody gives you a scythe and you try to mow your lawn with it yourwife will roll on the ground in helpless mirth until she needs to call the ambulance to take you away. It takes some
practice to use a scythe but throughout the millennia most people could do it quite well. That is because most people
were involved with agriculture and then a good scythe (and sickle) is absolutely essential.
The blade of a scythe needs to meet pretty much all of the requirements of a sword blade and then some. It must notcost a fortune but it needn't be good for showing off either. Most important, re-sharpening must be easy, and it should be
amenable to minor and major repair. The black smith across the road from my parents house spend quite some time
whetting the scythes of the local farmers during summer and fall.
Scythes were seeing hard use far more often than swords. A week of mowing probably meant more wear and tear for theblade than many swords saw during the life time of their owners. About the same is true for sickles . They relate toscythes like knifes to swords.
The best steel was used by specialized scythe makers, and making the blade was a laborious process:Career of a scythe blade in 15 stages
Source: Museum exhibit; undisclosed

Scythes have been in use for some time; here is a picture from 850 AD:

Iron, Steel and Swords script - Page 422

Illustrating the idea of "July" in 850 AD
Source: a martyrology in verse written by the monk Wandelbert in 848.

Some scythe smiths even used composite technology. A cut was made into a block of softer iron and a piece of hardsteel inserted. Then the blade was drawn out. That is, of course, also the way to make a katana, a Japanese sword.
And that is why scythes make good weapons, too. War scythes were regular scythes adapted for combat by reattaching the blade parallel to the haft. War scythes were widely used by Polish and Lithuanian peasants during revoltsin the 18th and 19th century, here is an example.. Scythe swords were also made but only one seems to have survived.
Scythes, like swords, are hardly used anymore, They have been made obsolete by big mechanical things that can
mow down far more grass or people than one expert swinging a scythe or sword. As far as they have survived,
however, they have hardly changed, witness these two modern blades, hand-forged by some artful modern
blacksmith.

Modern scythe blades
Finally we hit the big question. What, exactly, is a coulter? Maybe you should know, it's in the Bible, after all. The
question is if you ever gave a plow a good look? Here is a rather basic one:

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A plow with a coulter
The second picture is a detail from a Pete Bruegel painting
from around 1527 entitled "The val van Icarus" shown in theBrussel museum
A coulter needs to cut through the earth! That is a rather abrasive stuff with embedded very hard stones. You can't
easily think of something more demanding for a slender piece of metal. When we make coulters we get rather close
to sword making once more. We might actually make one from a sword!
Horse Shoes
I just mention horseshoes because they demonstrate the development of another specialization: farriers had to be both,experienced blacksmiths and veterinarians, knowing a lot about the anatomy and physiology of horses' feet. The word
comes from French "ferrier"=iron guy or blacksmith.
Protecting horses feet by some metal contraption is quite old. The Romans employed some "hipposandal" thatwasn't nailed down, however. It might have been the Celts who first used nailed-on horse shoes; first clear
archeological records are from the tomb of the 5th century King Childeric in France.
The farrier had to fit each shoe individually. Since horses are not overly fond of being shoed, he has to work quickly andwithout making mistakes. Putting in a nail the wrong way could kill a horse, and badly fitting shoes are just as bad for ahorse as for you. Horse shoes should be made from mild steel and that doesn't make the job easier.
A lot of farriers were needed in times when horses provided for the only means of transportation and most of drawing
power. If you use an oxen-drawn wagon, chances are that your oxens were shoed, too.
Sheet Metal and Plate
Nowadays a steel mill poduces a lot of plate and huge coils of sheet metal; see below. The plates may end up as partsof a ship, the coils of shiny steel will turn into car body parts. Continous casting and a lot of roller milling are theprocesses that come to mind for making this stuff.
Here are examples:

Iron, Steel and Swords script - Page 424

Steel plates and coil
Does this mean that there was no need for plate and sheet metal before 1850 (iron ships) or 1900 (cars)?. Not quite.
Armor of all kinds, your war-wear as the fashion industry, no doubt, would call it today, started as sheet metal justlike your car body.

Iron, Steel and Swords script - Page 425

A knight and his horse in sheet metal war-wear
Large picture
Source: Photographed in the Metropolitan

It was Henry Cort (1741 (?) – 1800), the inventor of puddling, who also invented the rolling of iron / steel. In 1783 he got
a patent for a grooved rolling mill and from then on the use of rolling to produce all kinds of shapes was open. You
needed plenty of power from a steam engine for driving the rolls, and very good steel for the making the rolls, so once
more an invention feeds on itself since without puddling steel you couldn't make those things.
How was plate and sheet metal made before this?
With a hammer in a forge, of course. Up to about 1300 sheets were hammered out by hand, then increasingly with awater-wheel driven power-hammer. Standardized sizes emerged in some places. In the Oberpfalz (North Bavaria) the
sheet size was about (25 × 32) cm2, coming in three thickness variants:
Dünneisen (thin iron); 0,46 mm, 290 g.
Bodenblech (bottom sheet); 0.81 mm, 508 g
Pfanneisen (pan iron); 2 mm, 1250 g
That is some amazing precision for working with a hammer! The process was rather involved with some annealing in
between. Here some circle closes. That's what Çrockü and Nölüdyæ, the stone-age types did, when they firstworked native copper.
The names above give us some idea what plates and sheets were needed for. The pan iron was used for making
pans. But not ordinary cooking pans but large (riveted together) salt pans for boiling brine in order to produce the allimportant salt!
The thinner sheets were used for all kind of things (including armor) but mostly for making tinplate, "galvanized"
sheets, so to say, except that the tin coating was produced by dipping the "pickeled" iron sheet in liquid tin and notby electroplating. Tin plates were a German monopoly, very popular with all and sundry since the end of the 15th
century; you still find it in "tin cans". German tinplate was even threatening the English pewter (≈ 90 % tin plus Cu,
Sb, Bi,...) industry and measures were demanded. But the Germans could keep their secret for quite some time
until English spies in 1667 got hold of the process.

Iron, Steel and Swords script - Page 426

11. Making Swords
11.1. The Early Sword
11.1.1 First Swords
11.1.2 The Bronze Sword
11.1.3 The Luristan Iron Sword
11.1.4 Swords of Major Near East Powers in the 1st Millennium BC

11.2 Swords of Celts and Romans
11.2.1 Background to Celtic Swords
11.2.2 Metallurgy of Celtic Swords
11.2.3 Roman Swords

11.3 Pattern Welding
11.3.1 Background to Pattern Welding
11.3.2 More to Pattern Welding
11.3.3 Evolution of Pattern Welding
11.3.4 Metallography of Pattern Welded Swords

11.4 The Transition to All-Steel Swords
11.4.1 Viking Swords
11.4.2 Blades of Viking Era Swords
11.4.3 Ulfberht Swords

11.5 Wootz Swords
11.5.1 The Winner is....
11.5.2 Structure by Dendrites?
11.5.3 Forging a Wootz Sword

11.6 Japanese Swords
11.6.1 The Myth and the History of the Japanese Sword
11.6.2 Making a Japanese Sword - Part 1
11.6.3 Making a Japanese Sword - Part 2
11.6.4 Metallurgy of the Japanese Sword
Iron, Steel and Swords script - Page 427

11. Making Swords
11.1. The Early Sword

11.1.1 First Swords
What, exactly, are swords? I asked that question before and I gave first answers. I told you that a sword is first andforemost a tool for killing or wounding "the enemy". The word actually means "to cut, pierce" in its proto-Indo-European
root "swer". In German a sword is a "Schwert" coming from the same root from old High German "sweran"=to hurt, and"swertha"=the cutting weapon.
I also told you that a sword can be much more. Swords are for example powerful symbols, objects of art and, mostimportant to me, a sword embodies the status of the metal technology in any given culture.
It is now time to realize that swords were among the very first utensils people made only for fighting and warfare.
True, some cave-dwelling stone age guy might have used his stone knife for slashing away at his enemy, and an
early hunter might have used his bow and arrow to shoot at his foe. But all these things, including knifes of stone ormetal, were primarily made for everyday life, agriculture or hunting. They were dual-use or multi-use items, sure, butnever for single use in fighting only.
A sword has many symbolic functions that do not demand to actually wield it. But you simply cannot use it"mechanically" to butter your bread, to cut your steak, to clean your fingernails or to cut a hiking staff from the next
hazelnut bush. In many cultures just the attempt to do something like that would have been frowned upon if notpunished. You can only use a sword for fighting, with the intent to hurt or kill humans. Even hunting animals withjust a sword doesn't make much sense.
People at some point in time might have used bows and arrows that were dedicated to warfare and not used for hunting.
The famous composite bows of the Huns are an example. They allow power-shooting while riding a horse in full gallop.
But you could use them for hunting without any problems and they are still very close relatives of the general bow.
Swords, however, are not just knifes with an especially long blade, just as a knife tied to a sturdy pole is not a knife withan especially long hilt but a lance, something new. Your style of fighting with a lance or a sword is quite different fromfighting with a knife. Fighting is the only thing you do with a sword (if we discount executions). A lance, while certainly
also a fighting tool, has at least some use in hunting, especially if you go after boars.
OK - I felt it is necessary to make this kind of fundamentalist black-and-white differentiation between knifes and swords
at the outset of this chapter. If you, like me, are fascinated by swords, you should consider your reasons for this on
occasion.
Now let's be reasonable and realize that in real life there is almost always some grey in between the black andwhite. There is, after all, a continuous path from your peaceful bread-and-butter knife to your deadly sword. In
between is your large farm utility knife, your butchering knifes, your pointed hunting knife, your dagger, your longfighting knife with a sharp point.
Of course, swords developed out of knifes as soon as the technology was available, and there are manifestations
that were neither here nor there - in metal and stone:

Flint dagger from Denmark, about 1800 BC
Bronze dagger from South-East Asia, around 300 BC
Different scales but comparable sizes; bronze dagger
slightly foreshortened for match.

Iron, Steel and Swords script - Page 428

Source: Top Photographed in the National Museum of Denmark in
Copenhagen 2012.
Bottom. Internet at large

The "fish tail dagger" shown above was not an utility knife; its only use could have been in showing-off andintimidation. Maybe it symbolized the owner's power of stabbing and thus killing you, or just that he could afford toown beautiful but useless items, i.e. that he was rich. It is rather young for a stone age item and might have beenmodelled after metal knifes that already existed but were to hard to come by in 1800 BC. There are many fish taildaggers at least in the North. Here are a few from "my" museum in Schleswig

Fish tail daggers from Schleswig
Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

The shape of fish tail daggers is not exactly the same as the shape of contemporary local daggers but coming
close. There are actually many stone tools that were modelled after bronze objects. A more spectacular one ishere.
We don't know if stone age man had stone blades and axes that were made and used primarily for organized warfare.
The Varna guy from around 4500 BC lived right at the beginning of serious metal usage and had stone and copper axes
in his grave besides all his gold - but no knife and certainly no sword. We might safely assume that the axes do notsignify that he was in the wood working business but that he was a mighty Lord with the power to give the axe to his
underlings.
There is a straight path from your utility stone axe to a war axe or a symbolic / ritual stone axe and later metal axe.
There is no way, however, that a stone-bladed utility knife can evolve into a functional sword.
You might try wooden swords, and metal deprived societies actually made some:Part of a wood sword with shark teeth from Gilbert
Islands
Aztec warriors brandishing obsidian tippedmaquahuitlas (or Macuahuitls)

Iron, Steel and Swords script - Page 429

Source: Photographed at the National History Museum, NYC 2013 /16th-century Florentine Codex

It certainly would be unpleasant to be hit with one of those shark-teeth or obsidian covered things but preferable by
far to being hit with a sharp-edged metal sword. You simply can't make a good sword without a metal. Not all
metals qualify, however. Gold (Au) and lead (Pb) are out for obvious reasons, and so is halfway pure and thus soft
copper. That leaves only bronze for early men, and the first swords were indeed made from bronze around ??? Let'sbe careful now !!!.
I'm about to play our old (and by now somewhat boring) game:

Who made the first swords,
when and where?
Wikipedia comes down in favor of around 1600 BC as the time horizon were practical swords were made that could
actually be used for fighting. Earlier stuff, considered from a warriors point of view, is denounced as long daggers orjust decorative or ceremonial junk.
Then we have the R. Ewart Oakeshott who in his classic "The Archaeology of Weapons" sees the beginning of thesword in Minoan Crete and Celtic Britain around 1500 BC - 1100 BC. He also makes a point about the first swords
being rather pointy because they were used as thrusting weapons.
Some more modern archaeologists beg to disagree. Foremost, perhaps, is Marcella Frangipane from the
Sapienza University of Rome, Italy. Like her compatriot Isabaella Caneva, she digs up old tells or settlementmounds in Turkey. In her case it is Arslan Tepe (Lion hill), close to Malatya in East Anatolia. In 1996 Marcellaunearthed what is now known as "royal tomb" from about 3000 BC. In it she found "Le prime spade al mondo", thefirst swords of the world, as the (Italian) Arslan Tepe site proudly proclaims.
Here they are:

"Le prime spade al mondo" - the first swords of theworld
Source: All over the Net

Iron, Steel and Swords script - Page 430

The longest sword is about 62 cm long and weighs 960 grams. It, like all theothers, was made in one piece by casting arsenic copper alloy in a mould. Someswords were inlaid with silver. All are rather flat and remind me of a (far smaller)
letter opener I once had in my possession. Next to the swords some spear heads
were found, too. All that (and more) was in one place and obviously seen as avaluable treasure.
So, are these things swords? If yes, are they thrusting swords? Many feel thatthese objects are no good for fighting - no good grip and guard, awkward to holdand not pointy / sleek enough for thrusting - and that one should not count themamong "real" swords.

Advanced
Link
Arslantepe

One might see these objects as just some curiosity, something that occurred as a kind of singularity in space andtime. They were probably just used for some ceremonial / ritual purpose for a short time and only in Arslantepe.
After all, nothing else like these things has ever been found?
Well - No! Nothing like these things has been dug up, indeed, but in 2011, Thomas Zimmermann and colleagues
found and described a quite similar sword1). They "found" this piece in the private collection of Necdet Dilek, whichis associated in some way to the Malatya museum where the Arslantepe swords are displayed. The "Necdet Dilek
sword" is about the same size as the silver decorated one from above; it was "found" under unclear circumstances
somehow and somewhere and made it to the antique trade. Tracing its history and analyzing the object gives clear
hints that it is from the region and the time of the "proper" Arslantepe swords.
Here it is:

The "Necdet Dilek sword"; front and backSource: Necdet Dilek's Internet site

That's interesting but only mildly so. The real impact of this find is that the blade shows signs of impacts from otherblades - meaning that this sword was actually used in (sword) fights! That's at least what the authors claim.
The story goes on. Yet another Arslantepe sword has been found. This time (March 2020) in the showcase of an
Armenian monastery in Venice, Italy. How it got there nobody knows but we may safely assume that it was before
Marcella Frangipane started digging in 1966. The sword was investigated and found to have the proprer age andcompositions (arsenic copper bronze). Here it is:

The Arsalantepe sword found in Venice
Large Version
Source: InternetM ascribed to Andrea Avezzu / University of Venice

It looks to me that we are once more at a point where there are more questions than answers. New finds from somedigs may change the present view about the history of swords, only time will tell. However, I do not think that we will
have to change our present views in a radical way. We will most likely not find that Neanderthal men was smelting iron,that the pyramids were built with steel tools, or that working swords are as old as knifes and daggers.
So let's not spend more time with the fascinating but not really very rewarding hunt for the "first sword" but go on tothe "mainstream" bronze swords.

1)

Thomas Zimmermann, Necdet Dilek, und Tolga Kapan Önder: "Ein neues Schwert vom Typus ‚Arslantepe‘ –frühmetallzeitliche Waffentechnologie zwischen Repräsentation und Ritual" Mit einem archäometrischen Beitrag von LatifÖzen und Abdullah Zararsiz. PZ, 86. Band, (2011) p. 1 – 7.

Iron, Steel and Swords script - Page 431

11.1.2 The Bronze Sword
Some Basics
Before I now go into swords proper, I want to make an important announcement that is valid for all that follows:

What follows is about the history
and metallurgy of swords andnot about killing people
I have told you long ago why I am fascinated by swords. Sir Richard Francis Burton , an exceptional scientist,
explorer and swordsman, wrote In 1884: “.... the history of the sword is the history of mankind”. I do not share thissentiment (as far as I'm concerned it should be “.... the history of science and engineering is the history of
mankind”) but if you go with Burton - that's fine with me. You might have different reasons for being fascinated byswords that are also perfectly allright. However you better be clear about that. If you lean in this direction, you may
not profit much from what follows.
What is there to know about bronze swords? My impression until recently was always: if you have seen one, you haveseen all - in contrast to "real" swords. Not to mention that bronze as a material is just not very fascinating - in contrast
to iron / steel once again.
Well, let's see if that is true:

Bronze swords in some museums
More bronze swords in museums
Large picture of "Schleswig" and Copenhagen swords.
Source: Copenhagen, Schleswig: Photographed there. London: Internet"Bronze Age Center"; William M. Athens: Internet at large.

Are they all alike? It's a matter of how closely you look. These sword are certainly more alike than their ironcounterparts but there are also marked differences. By the way, well-kept bronze swords without the grime and patina of
the millennia that makes them green or spotty, were objects of great beauty - look at the replica in this large picture or
this special moduile to get an idea!
I give you just two things to look out for; oversimplifying a lot, of course:
Iron, Steel and Swords script - Page 432

1. How are hilt and blade connected? The three extremes are:
1. The cast blade has no tang and is riveted to a separately made bronze hilt. These swords are known as
Vollgriffschwerter ("full grip swords") or "Naue I type; examples can be seen in the lower right above andright below.
2. The blade has a kind of tang or "tongue" to which the hilt pieces are fastened. By rivets or in the standard
way of later iron swords. These are Griffzungenschwerter (Grip tongue sword); Griffplattenschwerter (gripplate sword) or "Naue II type"). Here is a particular nice one.
3. The blade and the hilt are made in one cast. These kinds are also counted under the No. 2 types above. You
will see examples as you go along.
Julius Naue (1835 - 1907) was a German artist and (self-educated) archaeologist who contributed substantially tobronze age knowledge. The German names above were coined by him and later were "internationalized" by using
his name. Unfortunately, the name "Vollgriffschwerter", literally "full-grip-sword" implies the opposite of what was
intended and thus is used on occasion for the type 3 above.
Of course there are exceptions and in-between's, not to mention hot battles among archaeologists and normal
people about this and that detail.

2. What kind of fighting style is the sword optimized for? This follows from the shape of the blade. The three simple
cases are
1. Thrusting / stabbing only . Typically a slender very pointed blade with a strong midrib. Sometimes this kind of(early bronze) sword is also called rapier, again confusing all and sundry because they sure do not look likewhat one normally associates with that term.
2. Slashing / cutting. For slashing and cutting only you don't need a point. Most swords nevertheless have one,just not very pronounced and pointy.
3. Thrusting and slashing. The compromise.
Of course there are exceptions and in-between's, not to mention hot battles among archeologists and normal
people, etc. etc.
What seems not to be debated, amazingly enough, is that bronze swords "proper", as opposed to the Arslan Tepeswords, evolved out of daggers and first appeared (in bulk) around 1700 / 1600 BC in the Mediterranean, from where thetechnology spread. At this point it is necessary to refer to the excellent Internet pages of Stefanie Gröner and Andrea
Salimbeti , which I have copied for you. Besides providing a wealth of material and illustrations, they also point out that
there are some much earlier copper swords / daggers, too, e.g. from Naxos around 2800-2300 BC and from the Minoansat an unclear but early date .

Iron, Steel and Swords script - Page 433

Nebra (North Germany) swords (1600
BC)

Minoan swords / daggers 1600 or
beforeNebra sword detailMore daggers of similar style
Source: Nebra: Internet / Wiki. Minoan swords

That there were bronze / copper swords before 1600 BC is good because the treasure hunters who in 1999 dug up
the sensational "Nebra sky disk" in Sachsen-Anhalt in Germany (look it up here) also unearthed the two bronze
swords shown above - and all this stuff was dated to around 1600 BC. Compared to the Mediterranean in generaland the Greek islands in particular, Nebra in North Germany was a dark, dank and cold place - the pits, in otherwords. They could not possibly have invented swords there (the guys were East Germans and not Suebians!). But
those Nebra swords are already rather perfect. If they do owe their existence to Mediterranean technology, it stands
to reason that the guys down yonder in the South must have produced stuff like this before 1600 BC. We also learn(once more) that there must have been well established trade relations between the North and the South in thosetimes. The North had amber and blond women to offer.
As it happens, the "Amber road", going down from the Baltic by way of the Vistula and Dnieper rivers to Italy,
Greece, the Black Sea, Syria and Egypt, was in place in 1600 BC, possibly even earlier. The breast ornament ofKing Tut contains large Baltic amber beads, for example. Bronze swords could have made it to the North coming up
this trade route.
In fact, the North European bronze swords appeared rather early and, up to a point, are in a category of their own. Not
only have we found far more than one might have expected, many of these swords seem to have undamaged blades but
worn hilts, suggesting that they were fingered a lot but not actually used in fights. And we have quite a lot of them in"my" State Museum in Schleswig, Germany.
Below are examples of "Vollgriffschwerter" or Naue I type swords, just like the Nebra swords above. It is clear thatthe riveted connection between the blade and the (not preserved) hilt is not able to withstand bending and shearing
forces very well. Think of your garden hand shovel and you understand. Any forces not straight up or down the blade
will tend to rip out the rivets - and that has happened a lot; one of the blades below shows that.

Vollgriffschwerter (Naue I) probably around 1600 BC
Large picture
Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

And here are "Griffzungenschwerter" (Naue II) from a later but not disclosed time. Rivets are still used to fix hilt parts
to the tang of the sword but they are no longer crucial for the mechanical behavior. The hilt now can neither come off
nor bend.

Griffzungenschwert (Naue II) Schleswig
Large picture
Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

Iron, Steel and Swords script - Page 434

Before I go on, let's get some idea of what distinguishes a straight double-edged thrusting only sword from a slashing
only one; and how one could achieve a dual-use blade. The following drawing is taken straight out of Oakenschott'sbook:

The three basic types of bronze swords according toOakenschott
These three kinds of blades may not look all that different to you - but that is deceptive! What you can't see is thatthe geometry of the cross-sections is also quite different. The thrusting sword has a thick ridge running down thecenter, while the cutting or slashing sword is more flat (lentil-shaped) if it doesn't have outright fullers, i.e. is eventhinner in the center.
Of course you will also find anything in between the basic shapes given above. For example the carp's tongue
sword.
Here are some real examples from Schleswig:

Iron, Steel and Swords script - Page 435

Thrusting, cutting and dual use swords
Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

Here are some swords predominantly for thrusting . Note the substantial and thick central ridge for all of themThrusting swords
Large picture
Iron, Steel and Swords script - Page 436

Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

Oakenschott makes a point that the first "true" swords or, if you like, very long knifes optimized and only used forfighting, were of the Naue I type with a thrusting kind of blade. In fact, Naue I type swords could only be used in athrusting mode because they simply would come apart if you whack away with them. The rivet construction just could
not take large shear forces perpendicular to the blade, in contrast to normal forces in the direction of the blade. That iscertainly true, and many of the Naue I kind of swords actually do show damaged rivets and rivet holes.
Fighting by thrusting only is an acquired skill. The natural impulse is to slash around yourself. This might account for thedamage - in the heat of battle you just loose control. So the Naue II sword with a secure hilt construction was developedthat could survive slashing. Somewhat later came the dual-use sword. That is Oakenschott's viewpoint. It sounds
reasonable and might even be true - up to a point!
However, my Schleswig-Holstein Landesmuseum begs to disagree. The experts there argue that long before swords
were used in fighting, people were already whacking away at each other with axes or knifes fit to a pole at right angles.
They were also stabbing and thrusting with lances but at close distance slashing was better. The first swords then weremeant for slashing. Thrusting, as an acquired art needing plenty of discipline, came later. And indeed, there are very old
one-edged swords definitely only good for slashing / cutting, see below. Sounds reasonable, too.
I don't have to offer anything to that topic myself. There is a puzzle, indeed, but it doesn't interest me very much. I haveneither thrust nor slashed at an opponent with anything like a sword or knife so far, and I intend to keep it that way.
What puzzles and interests me is a purely technical point: The Naue I kind of swords / daggers in 1600 BC or so are
products of an already quite advanced bronze technology. It would have been no problem to cast a blade with a hilt or atleast a tang, as was done later with the Naue II kind of swords and with earlier swords of a different kind (see below) .
Why did those early sword makers go for an inferior design? All over the globe and for quite some time? It doesn't take agenius to do better, the technology was certainly available, so why? I do not know.
Some Specialities
All bronze swords look rather alike. They are all straight, double-edged and more or less pointy. Are they? Really all ofthem? Of course not. There are the exceptions to the rule as always in this business. Here is one of the more
spectacular ones:

The Rørby swords
Top: With a flint stone copy as inset (More here).
Bottom: Detail of blade with ship decoration.
Source: Photographed in the National Museum of Denmark in
Copenhagen.

Iron, Steel and Swords script - Page 437

This sword (and another one exactly like it) was found in 1952 in a small bog at Rørby in western Zealand /Denmark. It is shown with a flint copy found somewhere else. The sword is dated to the beginning of the (Danish)bronze age around 1600 BC and thus is on the "old" side. The second sword found in 1957 at the same place isdecorated with a picture of a ship. This is the oldest example of a ship image in Denmark.
The swords were cast in one piece, obviously from the same mould. The two pins at the front end may serve to add
weight to the optimal striking point, where the blade is also quite sharp. Oakenschott considers these swords as"clumsy, hideous, but most deadly". The Stockholm Museum has another one of this type but cast in a different
mould.
Note that the hilt of the Rørby sword is cast together with the blade, making it Naue II type. This goes right with myquestion from above. Why were all these technically inferior Naue I tpyes of swords / daggers ever made? Also notethat this sword is decidedly a slashing sword. The fact that a flint stone copy exists indicates that these swords
were precious and rare, but also that they were known far and wide. They might have been prestige imports fromsome (Southern) place with an advanced technology but nothing like these swords has been found anywhere else
so far.
Then we have the khopesh, the sickle sword, popular in ancient Egypt and Mesopotamia.

King Tut's khopesh (ca. 1350 BC)
Large picture
Source: Internet at large

The khopesh evolved form battle axes like this one and enjoyed some popularity in Mesopotamia and especially
Egypt from at least 2000 BC to 1200 BC.
Note once more that it is decidedly a slashing weapon.
Finally, a note must be made about Greek swords: the xiphos, makheira and kopis.
The xiphos was the double-edged, one-handed straight and relatively short sword used by the ancient Greeks. It
comes in bronze and later in iron and resembles the "classical" leaf-shaped bronze swords or the early Celtic("Hallstatt") swords.

The Xiphos

Iron, Steel and Swords script - Page 438

Top: Some guy names Actaeon, attacked by his hounds,
defends himself with a Xiphos. Detail from a Lucanian redfigure Greek vase (a "nestoris"), ca. 390-380 BC. Source:
Wikipedia.
Bottom: The lot. About all surviving Xiphoi, it seems.
Around 500 BC but with uncertain data. Source: General
Internet; no details given.
Makheira is the term some Greek writers used for Celtic swords, for cutting type swords or just for swords with long
blades. The word (and the sword type) Makhaira is a variant of the Greek word for battle, fighting.
About the same thing for the kopis; the name "kopis" might go back to the khopesh as shown above. The literature
about these swords is a bit confusing and it appears that once more we have ancient pictures but not many
artifacts. In any case, both types are single edged and relatively straight. If there is some curvature, it is concave.
Here is a picture of warriors using kopis' as seen on the bottom of a drinking cup:

Greek hoplite (soldier) and Persian warrior fighting
each other withkopis type of swords. 5th century B.C.

Similar picture from a vase
Source: National Archaeological Museum of Athens / Wikipedia

The pictures are of Greek origin so the Greek soldier ("Hoplite") is winning, of course. Interestingly his opponent has thesame kind of sword.
Pictures are fine, real swords from the time in question are better. Unfortunately it is not easy to find the real things.
That is also why we don't know if these swords were made from bronze or already from iron. Here is the best I could
come up with:

Iron, Steel and Swords script - Page 439

Makheiras (top three) and a kopis / falcata as found in
the Internet
More kopis pictures
Source: Internet at large

The top three objects are Makheiras made from bronze; the bottom one is an (iron?) kopis.
There are, however, also pictures showing makheiras that look similar to the kopis. The
Greek kopis is practically identical to the Spanish falcata, always (?) made from iron, andused with memorable effect against the Romans.
Note for the third time that these swords are primarily slashing / cutting weapons.
The best way to see Greek swords is, of course, to visit Greek museums. Or is it? The link
will tell.

Advanced
Link
Greek
Museums

It is time to stop. We are already moving to iron swords that are closely related to their older bronze brethren. The
typical long iron sword of the Celts, for example, is a straight evolution from their bronze cutting swords like some of theones shown above.
What about the metallurgy? Why didn't I mention it? Because I covered it all before. The data in this link show whatkind of copper / bronze technology existed in major areas at a given time, and, as in the case of iron / steel swords,
one can be rather sure that bronze blades also reflected the best people could do with this alloy.

1)

Stefanie Gröner and Andrea Salimbeti: The Greek Age of Bronze Swords/Daggers; on-line: http://www.salimbeti.com/
micenei/weapons1.htm . Here is a pdf copy of this article

Iron, Steel and Swords script - Page 440

11.1.3 The Luristan Iron SwordThe Enigma of the Luristan Iron Swords

Meet King Luri. Here is another one
Here are more Luristan swords
This is king Luri. He has been dead 3000 year or so but nevertheless challenges you to solve his riddle:(How was I made?). Luri is made from iron just as the rest of the very old
Luristan iron mask sword he is part of. Nobody, as far as I can tell, knows for sure how he was made.
Yes, indeed: The beginning of the iron sword starts with a veritable puzzle, actually several puzlles in one: The
mystery of the "Luristan iron sword". But before I go into this we must pay attention to our little game:

Who made the first iron swords,
when and where?
Science Link
Hub
First ironswords

The first
bronzeswords(more likedaggers,
actually)
were fromaround3000 BC.
Smalliron
objects(includingKing Tut's
iron andgold
dagger)were
often, if
notalways,madefrommeteoritic
iron andappearedwellbefore the"official"

Advanced
Link
Early FeswordsIron, Steel and Swords script - Page 441

beginningof the iron
age in1200 BC.
But whendidcomplexobjectslikeswordsthat weremadefrombloomeryiron maketheir
debut?
You knowthestandard
answerby now:Whoknows? I
have
devotedthe two
specialmodulesto thatquestion;:
one opf
whjoichgoes
iojntpogreat
detaiöl.
The
tentative
answerseems tobe:Complex iron objects like the Luristan
swords appeared around 800 BC
Luristan is definitely a major contender for first iron swords but early celtic swords also fit into that scenario. Not only
are the well-known Luristan iron "mask" swords (or type 1 swords) from around 800 BC, there is also another (andpossibly somewhat earlier) line of Luristan iron swords as shown below . I call these swords Luristan iron swords type2 just for ease of writing.

Iron, Steel and Swords script - Page 442

Luristan iron sword of type 2
More pictures here, here, or here.
Source: This sword has a trick history but is now kept in the Royal art
and historx museum in Brussels, Belgium

What we need to know now is that the Luristan iron technology evolved from an older tradition of very skilled bronze
work. Luristan is also not so far from the places where iron smelting was invented or at least practiced very early on.
Now I need to know that question you got desperate to ask: What the hell is Luristan?
Chances ar that you have never heard of Luristan before so the first .thing to do is to show it on a map. Here is Luristan:

Luristan and potent neighbors around 1000 BC
Source: Internet

Luristan occupies a remote corner up in the high mountains of the Zagros. It is still a remote corner in present day Iranand has never amounted to much as far as empires, large cities or other "high culture" stuff is concerned.
As far as I can make out, Luristan was also of no particular importance 3000 years ago. Luristan had mighty
neighbours, however, like the Elamites, Sumerian / Babylonians, Assyrian, Iranians and so on who controlled its
mountainous region on and off.
Luristan is known now as the region from which enormous amounts of grave goods, mostly bronze objects made it into
shady international markets around 1920. The Luristanis started to dig up the graves of their forebears and sold what
they found via the basars in Teheran and elsewhere. Many thousands of high-qualtiy bronze objects were unearthed andare still biought and sold at antiquity auctions.
If the difgging was illegal is hard to tell. The Luristanis in 1920 were possibly not even aware of their menbershio in thestate of Iran. That some unknown government should have more rights to the grave goods of their ancestors than thelocal people would probably have been an alien thought to them
However one looks at that issue, one fact remains: All these objects are without the scientific context that can only
result from professional excavations. None of the objects can be dated, for example, because no organic residue
amenable to a C14 analysis comes with them.
Lots of fakes and ancient
objects from somewhere else
but marked as "Luristan" also
appeared and are still out there.
Since nobody knows exactly
where the "Luristan" objects
came from and how they relate
to other stuff from that time, theirvalue for unraveling history is
extremely limited.
However, some objects bear
inscriptions of names that are
known, some are similar to otherstuff with know provenances,and some could be dated bymodern methods. Moreover, realarchaeologists have conductedexcavations in the area and a lot
was learned about the Luristan
culture.

Advanced
Link
LuristanIron, Steel and Swords script - Page 443

More to that in the "Luristan"(advanced) link
Of interest to us here are the iron swords from Luristan since they seem to be among the "first" ones.. Once more, there
are two kinds.
1. The rather well konwn " mask swords" or type 1, the major topic here. About 100 mask swords are around, andall but one come from the illicit digging in the early 20th century. They are unlike any other sword ever fpound andhave no obvious relation to older bronze swords (fo which there are thousands).
2. The rather little known straight and long iron swords (type 2; see above)) with close similarities to bronze swords.
Pictures of these swords ar shown here and here.
Here we only look at the type 1
Luristan iron mask swords
since very little is known abouttype 2. There are about ahundred or so mask swords
about, and they are remarkably
similar. Swords of the Royal
Ontario Museum and theMassachusetts Institute ofTechnology could be recently
dated to 1094 BC +/- 60 years
by radiocarbon analysis. That
result was a surprise toarchaeologists and researchers,
as the prevailing opinion untilthat point was that thesedaggers or swords came fromca. 800 BC – 550 BC. One mustbear in mind, however, thatdating steel by dating the carbon
contained in it is not easy, andresults at present must be takenwith a grain of salt.
I actually started a small project
about dating and investigating
Luristan mask swords and someof the results will be given in the"Luristan Special" link.
For now we just note:

Advanced
Link Hub
Luristan
SpecialC14 dating of Luristan swords is not reliableAs you know, Luristan iron swords have exercised me already quite a bit; in the links below you can find out why:
The Luristan iron sword in the Metropolitan.
Muscarella's interpretation of the Luristan iron sword in the Metropolitan.
The following picture shows four of those swords, all of them owned by big respectable museums in the countries
noted.

Iron, Steel and Swords script - Page 444

Four Luristan iron swords
Large pictures of different onesMore Luristan swords
Source: "Maryon" 1); Muscarella's Book,

On a first glance these swords look rather like oversized daggers or dirks - and a bit weird. Certainly not awe-inspiring.
So where is the enigma, the puzzles? Where they made from a high-quality steel, perhaps?
Certainly not. Let's get this outof the system right away:
Around 1000 BC nobody knew
about iron vs. steel. At best
primitive bloomeries produced amix of stuff ranging from wroughtiron to hypereutectoid steel withplenty of slag and other dirt
mixed in. As discussed at
length before, we must expect
the swords to consist of rather
inhomogeneous iron - and that's
exactly what has been found!
It's not the quality of the iron, itis the quality of the constructionthat produces the puzzles.
Construction is the right word!
While all these swords appear tohave been made from one single
piece of iron, they actuallyconsist of about 10 or even moreindividual parts that were put
together in such a way that evenafter 3000 years it is impossible
to see the seams.
But the first and foremost
question is:

Illustration
Link
More Luris

Iron, Steel and Swords script - Page 445

How did the ancient smiths make thefigures on the pommel and at1.
the intersection hilt / blade?
I mean: look at the details - here or here or below. In the picture below you see one of the two lions a theintersection hilt / blade of the Metropolitan Museum, NYC Luristan sword; it's inlaid with carnelian stones. The
head with the beard that is "hanging" down from the flat pommel mutates at its back to another lion as can be seen
here. These ornaments look decidedly like casts - but that is impossible! Metallographic investigations 1) - 4) ofseveral swords proved beyond doubt that they do consist of iron or even steel, and nobody could cast that in 1000
BC. That is a generally accepted fact. Or is it? Lee Sauder has cast some doubt on this rather recently. He
demonstrated the melting of iron in a contraption that people could have operated 3000 years ago. So, maybe,these thing were cast? I won't rule it out categorically but as far as our own investigation showed, nothing was cast.
For the time being we stick to the old dogma: no casting of iron / steel before 1700 AD or so.
It they weren't cast, how were they made?

Top: Details of the Metropolitan Luri with carnelianornaments
Bottom: The Ontario Museum Luri
Large pictures of different ones
Source: Photographed in the Metropolitan Museum, NYC, 2011; Ontario
Museum (with permission) .

One explanation offered is that they were manufactured by swaging or hammering heated metal into a mould. This
is not very likely, however. First, I haven't read anything about the mould material. It needs to be pretty tough - likehardened steel - but that was not around in 1000 BC. Second, while these swords are quite similar, the ornaments
are all slightly different. So no mass production with one or just a few moulds has taken place. Third, you simply
cannot hammer a complex shape with concave areas like the head - lion piece into a mould and get it out again!
One remaining alternative is that some cunning smith sculpted all these things with a hammer and whatever othertools he had. I would tend to think that this is impossible. However, the ancient Luristanis could do quite tricky stuff
with bronze.
Maybe the figures were "carved" like a sculpture? At least for the finer details this appears possible. It is certainyl
easier to carve the iron directly then to carve a negative into a harder material as needed for swaging. Some otheriron artifacts from Luristan tend to confirm this view..
Whichever way it was done, it took a lot of skill and probably also a lot of time. In other words: we are talking
serious money here. Those swords must have been extremely precious.
Now the second puzzle:
Iron, Steel and Swords script - Page 446

These swords were made from many
parts but assembled in a way
2.
that it won't show
Why? And how?
I have provided a lot of sword pictures. Could you see that all these swords were made from many parts? Did you
see any of the many seams where the parts were joined! Here is a picture that supposedly tells it all:Luristan iron sword: X-ray image (right ) and cut (left)
Source Maxwell-Hyslop and Hodges

This looks rather complicated. Note that all these pieces are not "properly" hammer welded at high temperature but
are held together by dowels, clamps and "crimping" (that's what holds the cap on your beer bottle). Those ancientsword makers were rather skilled, it seems.
Or were they? Swords clamped and crimped together will not hold up all that well in battle, one must assume. "Todeal with the latter aspect first, we cannot agree with Joseph Ternbach when he says of the blacksmiths who
produced this type of sword that 'highly developed skill and artistry had been achieved in working the metal.' The
truth would seem to be quite otherwise. A competent blacksmith does not rely upon rivets and bands and burrededges to hold his work together; he uses, rather, a hammer weld carried out in the hot. To be blunt, seen in terms of
black- smithing these swords are a mess, and any of them could have been better made by the barbarian smiths ofcentral Europe, certainly by the eighth century BC" write Maxwell-Hyslop and Hodges in their review paper.
So why, oh why? Maybe they couldn't do better with the new material? Maybe, but making the ornaments inwhatever way did need some skill. Maybe these swords were never intended as real weapons?
All and sundry assumed that all or most mask swords were builr like this. Surprise! They are not! The "many parts"
scenario resulting from this early investigation is not the rule but the exception. Meanwhile a number of swords has been
X-rayed or otherwiese investigated and they all were made in a much simpler (if still very skilled) way from less parts.
More to that here, where you also will find details to the picture below:

Iron, Steel and Swords script - Page 447

Luristan iron mask sword cut in half and etched forstructure revelation
Source. Luristan project

You see a mask sword that was cut in half and then Nital etched. You see that the main body, including thecomplete blade, was forged from one piece of iron and that the "sculptures", the rings, and the top plate wascrimped-on as described before. You also see a kind of stripy structure that is typical for "faggoting" (i.e. repeatedfolding and weldin) but that needs a more detailed discussion then I can give here. Use the link for detals.
The third puzzle is:

Why Luristan? A rather remote corner
3. even then. Why switch to iron when
you were excellent at bronze?
Luristan is know because of its bronze artifacts. The iron swords cannot possibly be better than the bronze swords
the Luris manufactured with great skill and in great numbers. One possible answer is that the "Luristan maskswords" are actually not from Luristan but from the large and mighty kingdoms around them that had mastered ironworking very early: Elam, Babylonia or Assyria, for example.
We can speculate all we like. As long as no such sword is found "in situ" in its natural environment (a grave) byarchaeologists, we will not get final answers. Since serious archaeology seems to be taking place in the Iran again,
there is hope.
The Metallurgy of the Luristan Sword

Iron, Steel and Swords script - Page 448

Let's start by enumerating the questions we need to ask here and in future chapters:
1.
2.
3.
4.

General quality of the bloom. Phosphorous / sulfur problems?
Did the smith / metal master conscientiously select different grades of iron / steel from the bloom?
Quality of the billets, bars or whatever made from the bloom. Sorted into different grades of wrought iron & steel?
Capability of the smith? His infrastructure? Stone hammer and stone anvil on the floor or dedicated special
equipment in a forge with a hearth?
5. Smith aware of fire welding and capable of doing it?
6. Smith aware of carburizing or, far more important, de-carburizing during forging?
7. Smith knows about hardening by quenching?
All we have here for directly answering these questions aresome finished iron / steel products, the Luristan swords, often
heavily corroded, and mostly not open to structuralinvestigations. If we are more lucky we have also remains ofancient smelters, some blooms and intermediate products likeiron bars or double pyramids for trading. No such luck here.
We don't even know for sure where, exactly, these swords
were made.
It is not quite as bad as it appears. We have a lot of bronze and other metal objects from the time and region inquestion. The (Proto) Elamites in Susa, not all that far from Luristan, could do amazing things with silver 2000 years
before the advent of the Luristan swords, for example, and "Luristan bronze" is famous in its own right. I will look into
this in this special module a bit more closely. For the topic here we just note that a very high level of metal working
existed around 1000 BC in Luristan and all around it. Making bronze by thoughtful alloying and not by luck, melting andcasting, plus cold-working it with a hammer and special tools was mastered by many.
And yet, working iron is quite different from working bronze.
Not being able to cast does make a huge difference. And yet
again, the Luristan smiths could work with iron extremely
skillfully. Whosoever can make one of the ornaments without
casting it must be an extremely skillful artisan, indeed.
One might consider the swords to be "a mess" if one
compares them to swords forged from one piece of iron /steel. That does not change the fact that making all theindividual parts and assembling them without revealing theseams does take a lot of skill. Making a fancy mechanicalwatch does take a lot of skill, too - and the product is a messcompared to a cheap electronic one. But then, you do not
sport an expensive mechanical watch so you can tell the time,
just as you don't sport a Luristan sword so you can fight.
Luristan bronze smiths could make fanciful bronze swords in
one piece, and they must have known that this is superior
from a fighting point of view to swords made from riveted
together parts. If they didn't do that for iron swords it most
likely means that it couldn't be done. If we now look at thatbackwards, a new question comes up: Why didn't the Luristan
artisan make bronze swords in the style of the iron swords?
They most certainly could have done that. No bronze swords
remotely similar to the iron ones have been found so far,neither in Luristan nor somewhere else. Maybe someentrepreneur started a new fashion?
We don't know. Maybe time will tell
I have just answered question No. 4 from above, admittedly in an indirect way. Yes, the smiths were up to the task.
Obviously, you can see it.
So what about questions 1 - 3? Good question but hardly any definite answers. From the analysis of the swords weknow that phosphorous and sulfur was not a problem - but that was likely just dumb luck. The bloom was probably small
and the usual mix of anything between wrought iron and steel or even cast iron; it also contained slag. This is justindirect inference but it can't be too far off the truth. The smiths did not select different grades or at least were not very
carefully about that. They did not know about property changes due to forging and quenching. This much we can inferfrom the analysis of the swords

Iron, Steel and Swords script - Page 449

One must bear in mind that the investigations were madequite some time ago. This necessitates to be a bit carefulwhen reading the old papers (and some new ones). The issue
does come a bit confused. Many of the old papers were
written under the assumption that bloomeries produced
exclusively wrought iron. Any finding of steel then was
attributed to "caburization" by the smith - and that is wrong!.
Confusing the issue even more are sentences like this one:
"Forging caused the transformation of the brittle bloomery iron
into wrought iron (with a carbon content of 0.5% to 0.25%) by
reducing the amount of carbon in the iron" 5) in an otherwise
superb paper of the editor of the magnificent "Arms and Armorfrom Iran".
Here is a structure picture showing ferrite (white) and pearlite(dark) in the beard section of the Toronto sword. This looks
like a Widmannstätten structure, indicating a rather highcarbon content.

Structure in the beard part of the ornamental head of
the Toronto sword
Large picture of blade
SourceAll things considered the Luristan iron swords are quite remarkable but we cannot yet appreciate them fully. We needmore data. Modern analytical methods might reveal mor details about the way they were made but most important
would be new in-situ finds by scientists.
Let's wait and hope.

1)

Herbert Maryon, R. M. Organ, O. W. Ellis, R. M. Brick, R. Sneyers, E. E. Herzfeldand F. K. Naumann: "Early Near
Eastern Steel Swords", : American Journal of Archaeology, Vol. 65, No. 2 (1961), pp. 17- 184

2)

Kate C. Lefferts. "Technical Notes on Another Luristan Iron Sword", American Journal of Archaeology, Vol. 68, No. 1(1964), pp. 59 - 623)

Vera Bird and Henry Hodges: "A Metallurgical Examination of Two Early Iron Swords from Luristan", Studies inConservation, Vol. 13, No. 4 (1968), pp. 215 - 223

4)

K. R. Maxwell-Hyslop and H. W. M. Hodges: "Three Iron Swords from Luristan" : Iraq, Vol. 28, No. 2 (1966), pp. 164 176: containing also: Vera Bird: Metallographic Report on Two Swords from Iran.

5)

Manouchehr Moshtagh Khorasani, “Bronze and iron weapons from Luristan”. Antiguo Oriente: Cuadernos del Centro deEstudios de Historia del Antiguo Oriente 7 (2009).

Iron, Steel and Swords script - Page 450

11.1.4 Swords of Major Near East Powers in the 1st Millennium BC
What's It About
You know that I'm not an expert for swords. I do know a thing or two about semiconductors, and I also know something
about the Materials Science and Engineering of metals. I know a sword if I see one and I have some idea about how it ismade and what - mechanically - it can do. But I did not know about akinakai (singular is akinaka or akinaces), forexample, until I had finished the preceding module and found out about these things more or less by accident. I also justrecently run across the Moroccan Nimcha sabre. I'm sure I don't know a lot of other sword-related specifics and I canthus not go into the swords of the early Afghanistanis, Albanians, Algerians, ... (add 190 more member states of theUN), nor do I feel a necessity to do so - except if I come across something of interest with regard to iron and steel
technology in this context.
This applies to akinakes but not to Nimcha sabres. What I found out about akinakes is: an akinakes is a kind of doubleedged straight dagger or short sword, made from bronze or iron. It was mainly used in the first millennium BC in theeastern Mediterranean region or Near East They are also connected to the Scythians and possibly to the Luristani stuff
in some not-so-clear way. Now I'm interested.
But not all that much. Most akinakes, it seems, are "found" in the antiquities trade and that means four things:
1. They may be fakes.
2. Even if they are genuine, the data (if given at all) about where and when they have been found may be wrong.
Illegal finders lie. Dealers lie. Even innocent mistakes do happen.
3. A lot of the scientific literature is hard to get and often in Russian or in other lmnaguages not open to me.
4. Not counting one exceptions: They have never been metallurgically examined.
Many akinakes, I'm sure, rest in some museums, particularly in the former Soviet Union, Iran, etc. - and I'm notaware of them. The ones I am aware of, while supposedly genuine, are usually not all that well described either. And
the number of museums that give a minimum of correct metallurgical information appears to be presenty zero.
The point I'm trying to make is: This Hyperscipt is about Materials Science (you must have noted that by now). It places
special emphasize on iron and steel, including the history of these metals. Swords are the paradigmatic embodimentsof iron and steel, and that's what makes them interesting to me. I'm also interested in many of the other aspects ofswords but my priority is with Materials Science.
It follows that some arbitrary iron sword from the first millennium BC is of some interest to me - but not of much interest
if I learn nothing about its metallurgy and how it was made.
Iron making in bulk did start in the East Mediterranean or Near East, and it is thus straight forward to assume thatsword making also started in this region. The Luristani iron swords bear witness to this. That's why in this module I
look a bit into the swords of the major powers that were present in this region in the first Millennium BC. However,when I looked more closely into the matter, it came to me as a surprise that only a few swords seem to be known
from before 700 BC, say. Let's look at waht we have.
Akinakai
Here are some akinakai according to the description given by their sources. As you see, the come in bronze only, iron
only, iron with bronze or gold hilts, and solid gold. You can classify them as short swords, dirks, or daggers. Take
whatever pleases you; I don't care.

Iron, Steel and Swords script - Page 451

Akinakes
Some more of Scytthian type
Source: Left two: auction catalogue. Middle: Museum of Russian art.
Right: Khorasani

The gold betrays Scythian influence and dates the objects to 600 BC - 650
BC, as stated by the Russian museum and fitting to the Scythianconquest of "the West" including what's now Iran. The Medes were able tokick them out to some extent, while the Scythians were able to fend off aninvasion by Darius the Great of Persia's Achaemenid Empire in 513 BC.
The Scythians are still rather mysterious, but we do know that they werenomadic living people with horses, and that they had achieved an amazing
mastery of gold metallurgy if not metallurgy at large - just like theLuristanis. "Scythian gold" is a well-known entity but they might also havemastered iron as shown be their very specail akenakai. That's why I
decided to add a "Scythian Special" in 2020.

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Scythian
SpecialThe golden akinake is dated to the Achaemenid Empire, the first Persian empire founded by Cyrus the Great, ca.
550 BC – 330 BC. There was a cultural interchange in other words (like plundering the cities, killing the men, raping
the women,..., as well as taking over the metallurgy knowledge) and that's probably how Scythians skills made it to
the Achaemenids.
All these objects (except possibly the Russian one) come from illegal digging: Their historical value is thus limited.

Full iron akinakes. Shown in segments because it's
too long
Source Khorasani's book

The rusty thing above looks far less fetching than the pieces one can buy. It is far superior, however: it was dug up
by archaeologists in Persepolis, the capital of the Achaemenid Empire. That allows us to conclude that around 500
BC somebody in the large Achaemenid Empire knew how to forge a 65 cm long sword in one piece. That's almost
impossible without fire welding.
Unfortunately nothing else seems to be known about the iron /steel used for akinakes. We will have to wait.

Iron, Steel and Swords script - Page 452

The Scythians might have "invented " the akinake and used them as weapons and as ceremonial objects. The othercultures, especially the Persians (and that includes Luristan) adopted the design and akinakes became popular in the
Mediterranean region and Near East. One might even see akinakes as the forerunner of the Chinese "jinglu sword", theGreek xiphos, and the Roman Gladius.
Akinkakes were primarily a thrusting / stabbing weapon. I would tend to believe that they could not have been the main
weapon for people living and fighting mostly on horse backs like the Scythians and Parthians.
Assyrian, Babylonian, Elamite, Achaemenid, and Parthian Swords
In the larger Eastern Mediterranean around 1200 BC iron gradually bcame a less precious item (in some places) andappeared in larger quantities. However, what we have found so far, tends to be small and relatively simple stuff. The"first" full iron swords might be from from Luristan, a hard-to-get-to highland area of apparently no historic consequencethen or ever. Areas of consequence were empires or became parts of empires, like it or not. The important empires
between 1200 BC and roughly 250 BC are the ones relating to the names in the head line. In addition, we have the(usually not-so-innocent) bystanders like the Scythians, Greeks, Egyptians, Cimmerians, Lydians, Phrygians, Luwians,
Urarturians...., and, not to forget, the Jews, Philistines, and so on. King David, one of the more unsavory characters of
the Old Testament / Tanakh lived around 1000 BC - if he lived at all.
It is a complex and possibly close to impossible undertaking to unravel exactly who made big progress in irontechnology where and when. However, we may state with some reliability that major iron use, including the forging ofcomplex objects did not take place before, roughly, the 8th century BC
All these names relate to the Eastern part of the Mediterranean or Near East. On
the West we had the Etruscians, Phoenicians, Romans, and so on. To the North
we had the Celts (and some proto-Germanic people). All of them (except the North,maybe) had some iron industry in the first millenium BC and, at the latest after 500
BC or so, made iron swords.
I have already looked at the iron production in the "West" (Etruscans, Romans) andthe North-West (Celts) after 500 BC.
The question is what we know about the Assyrians, Babylonians, and so on. The
answer is: Next to nothing. At least I couldn't easily find much that is worthwhile tobe mentioned here. And I did spend some time in looking around.
Just so you know what I'm talking about, I give you a quick list of the relevant
empires with maps and a few facts in the link.

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Link
Empires

Swords of the Assyrian Empire
The Assyrians ruled with the proverbial "iron fist", meaning that they wielded iron weapons that were superior to theweapons of their opponents and that they were rather brutal in using their iron. That they did have a large iron industry(or took over a large industry of vassal states) is proven by the huge hoard of iron (160.000 kg!) found in the remains of
the palace in Khorsabad.
Here is all I initially could find about Assyrian iron / steel weapons:

Assyrian weapons and an actual iron armor plate
Source: Internet at large; Metropolitan Museum NYC.

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All I found besides the iron piece from the Khorsabad hoard is an old drawing depicting Assyrian weapons thatsomebody I don't know made some time ago, and an actual iron plate from some Assyrian armor. The Metropolitan
Museum in NYC has many of these sorry things but nothing else the ancient Assyrians made from iron.
Well, several years later (it is now March 2020) I have to correct that statement to some extent. I found1. John Curtis' book: "An Examination of Late Assyrian Metal Work with Special Reference to Nimrud" (Oxfordpress, 2013). In this book many iron objects are shown and discussed. But it's typically iron spearheads,
arrowheads, armor scales and other small stuff. There is a kind of large saw blade but there are still no (good)swords! All we have is the sorry lot shown here. One of the objects shows some similarity to what I have called theLuristan type 2 sword.
2. The article "IF I HAD KNOWN THAT MY LORD WANTED IRON. The beginning of the common use of iron in
Assyria" from Caroline van der Brugge. Here is the link. The article is most illuminating and makes for goodreading. Caroline argues that no iron ore is found in the Mesopotamian plane and that the Assyrians thus depended
on others to supply iron or iron ore. She make a convincing case that large scale iron use in the Assyrian empire
did not start before the end of the 8th century BC.
How do we know that Assyrian swords looked like the ones shown in the drawing? From numerous large stone reliefs
these guys left all over the place, in particular in Khorsabad .
Here is Sargon II, fingering his sword (not necessarilly made from iron!)

Sargon II fondling his sword
Large pictures of more Assyrian sword carriers
Source: North palace Ninivah; 645 BC; Internet

However, these guys weren't just fondling their swords. They defeated about any other power around by then, the list
is quite impressive. The following picture shows parts of the taking of a Mannean fortress in 715 BC, as depicted ona now lost relief from room 14 (slab 2) of Sargon II's palace at Khorsabad. Nobody has ever heard from theManneam kingdom ever since.

Iron, Steel and Swords script - Page 454

Sword fight! Note also the wheeled siege engine on
the right.
Link to full relief
Source: Internet articel: Mannea, a forgotten kingdom of Iran. Karen
Radner, 'Mannea, a forgotten kingdom of Iran', Assyrian empire
builders, University College London, 2013
Drawing from P.-É. Botta and E. Flandin, Monument de Ninive, vol. 2,
Paris: Imprimerie Nationale, 1850, pl. 145.

However! There is some evidence that the Assyrians did not really use swords in battle. Maybe the cavalry (if they
has that) but not the infantry. The guys up their doing a sword fight actually use rather short swords (akinakai?), if
you look closely.
Whenever the Assyrian (fighting) nobility became bored of killing people, they went out to kill some lions. With theirsword!

Assyrian Noble stabbing a lion with his sword
Source: Khorsabad (I believe); Internet at large

There are many more picture like that, especially on seals.
Those pictures makes me almost a liar. I wrote: "Even hunting animals with just a sword doesn't make muchsense." Well. I do believe that even the most dedicated hunters out there today would be reluctant to hunt lions
Assyrian style. Except, of course, the Romans. Sometimes they lost. But seriously now: You can't stop a charging
lion like that. A grown lion weighs up to 820 pounds or 375 kg, the equivalent of 4 big people. Even if you manage tostab him as shown, he would throw you down quite forcefully and live long enough to take your head or damage you
substantially in other ways. It is impossible for mere mortals - and thus only the king could do it as shown.
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What did we learn about Assyrian swords? Not much. Essentially we can only state:
They had swords, very likely iron swords but we can't be sure.
And that applies possibly only to the upper crust and not to commoners including soldiers.
They (the nobility) carried their swords, embellished them, and showed them off.
They (the nobility) trusted their swords - or the liked to take very high risks in hunting lions.
But, maybe, the trusted more in the naivete of their underlings
Given the quality of the iron hoard in Khorsabad, their iron swords couldn't have been too good. They are probably
no better than Celtic swords
There is no way of telling if Assyrian smiths knew anything about the iron / steel issue and about hardening by
quenching.
They may not have used long swords in (infantry) warfare. Too expensive and not good in close-up fighting.
However, if they had a cavalry (I don't know) these elite guys might have had long swords.
We never found long Assyrian swords so far.
A bit more about Assyrians and their contemporaries can be found here

Swords of the Neo Babylonian Empire
You are never too old to learn a new trick! Putting "babylon sword" into Google, gives unexpected and possibly exciting
results; try it.
Otherwise nothing. Nada
Here is all I could find otherwise:

Babylonian scepter, iron and copper, 800 BC - 700 BC
Source: "Babylon Wahrheit"; the Book to the big Babylon exhibition of
the Vorderasiatisches Museum Berlin, Germany, 2008

The two books going with the exhibition mentioned in the figure source contain about 900 pages and more than
1000 pictures. The one above is the only one showing some iron. Maybe the Babylonian kings didn't use a sword todemonstrate who has is the biggest but a scepter instead. There is a likeness
Babylonian art, e.g. the famous pictures made from glazed tiles, does show soldiers but none with a sword. One
relief showing a guy with a sword is assigned to Babylonians or Assyrians, depending on which source you read.
So forget it.

The end. Sorry.
Swords of the Elamite Empire
We know the Elamites from way before as the makers of amazing silver and gold objects already around 3000 BC. Hereis another example. One might assume that they must have been pretty good at bronze and iron, too. Bronze - yes. Iron
- we don't know. Here is just one example for excellence with the three metals mentioned:

Bronze God, gold and silver Kings / Worshippers
Source: Internet. The two on the right are probably in the Louvre.
Iron, Steel and Swords script - Page 456

The Elamite area is East of the Sumerians and Babylonians, containing mountainous regions of what today is Iran. Thismap gives a rough idea. The so-called proto Elamites who made the good stuff were around in 2700 BC. Even then they
were having constant fights with the powers down in the valley like the Sumerians; many of which they lost, leading to
occupation and so on. Just a few highlights.
Shulgi of the 3rd dynasty of Ur (around 2050 BC) conquers Elam.
Babylonian Hammurabi (around 1770 BC) crushes Elam in 1764 BC.
Elam King Kutir-Nahhunte I attacks Samsuiluna, Hammurabi's son, around 1730 BC and deals so serious a
defeat to the Babylonians that the event was still remembered more than 1000 years later.
Tukulti-Ninurta I of Assyria (around 1230 BC) campaigns in the mountains north of Elam. The Elamites under
Kidin-Khutran, second king after Untash-Gal, countered with a successful and devastating raid on Babylonia.
Shutruk-Nahhunte (ca. 1160 BC) makes Elam powerful again. Two equally powerful and two rather lessimpressive kings followed, together they made Elam one of the great military powers of the Middle East. One
Shutruk-Nahhunte captures Babylon and carries off to Susa the stela on which was inscribed the famous law
code of Hammurabi.
Nebuchadrezzar I of Babylon (1124 - 1103 BC) attacks Elam and is just barely beaten off. A second Babylonian
attack succeeds, Elam is overrun, and that's the end for a while.
The Elamite King Shutruk-Nakhkhunte II (716–699 BC), was routed by Sargon's troops during an expedition in
710, and another Elamite defeat by Sargon's troops is recorded for 708.
Assyrian King Ashurbanipal takes Elam and destroys Susa in 627 BC. THE END, it seems
There is not much we have from the "iron age" Elamites. They appear rather in not-so-nice reliefs of the Assyrians:

Destruction of Susa in 627 BC by Assyrian King
Ashurbanipal
Source: Internet / Wikipedia

Assyrian scribes doing a head count.
The heads are probably from Elamites.
Source: Internet.
Iron, Steel and Swords script - Page 457

I gave you all this because everything I have to say about Elamite swords you can find in this link!

Swords of the Achaemanid Empire
Let's not waste time and space this time. Cyrus the Great conquered almost all there was to conquer (except the
Greek), and he did that seemingly without swords. Even Khorasani's wonderful book doesn't offer a single picture andhas very little to say. There seems to be one fries or whatever showing a guy with a long straight sword and one with akind of kopis. If those things were made from bronze or iron is unknown
In Persepolis, Cyrus' capital, we have many reliefs showing all kinds of people including soldiers. Almost none
seems to be carrying a sword, Some preferred pretty handbags, it seems:

Not carrying a sword
Source: Internet a large

The exception is King Cyrus' weapon bearer who is shown on a large mural / frieze / relief, whatever you like to callthat. Here is the important part:

Iron, Steel and Swords script - Page 458

The weapon bearer of King Cyrus he Great
Source: Internet a large

Big deal. It's an akinake !
Sorry - but that's it. We have no idea what Cyrus' smiths could do with iron.
Swords of the Parthian Empire
The Parthian Empire (247 BC – 224 AD) came about because one Arsaces I of Parthia, original a tribe chief, took theregion of Parthia from the Seleucid Empire, the sequel to Alexander the Great's masterpiece. That's why it is also
known as the Arsacid empire. King Mithridates I of Parthia (ca. 171 BC – 138 BC) greatly expanded the empire to whatis shown here. The Parthians were essentially Persians and a clash with the Romans who were running a huge empireof their own by then, was unavoidable.
Why do I mention Parthian swords here and not, for example, the "xiphos", the regular sword of the Greeks, swords
from the empire of Alexander the Great, and so on. Because there is absolutely nothing to learn about iron swords
from these guys. We simply do not have many, if any. In contrast to the Parthians!
Here are Parthian iron swords:

Iron, Steel and Swords script - Page 459

Parthian swords; 1st or 2nd century AD
Source: Khorasani's bookNothing to get very excited about. But at least those things were swords. The left one was 67 cm long, the right one 87
cm. There is no big difference to the blades of the Celts or to any "Spatha" between 500 BC and 1500 AD. It is hard tosay but the blades appear to have neither a ridge nor a fuller, possibly just the basic lenticular cross-section.
No seams due to insufficient welding are visible, but also no indication of conscientious piling of different iron / steel
grades. And of course there is no way of telling of these swords were hardened by quenching. There is also no way oftelling if those sword are perhaps of Celtic origin. After all, my forebears were roaming the area already in 279 BC andeven hung around for a few 100 years in Anatolia.
So, sorry, but the Mediterranean and the Near East is a bit disappointing, sword-lore wise. It is time to move to themore exciting West and North - but not before a closing paragraph.
Weird Swords
Museums own a lot of weird stuff. You just will not see it because it is usually stored in the basement and locked up.
Somebody sometime had dug up something weird, and it wasn't clear what it was or it looked very unassuming. You
can't throw it away, and you can't admit defeat either, so it goes into a box and into the basement. And that's where it
belongs because most of the time it is just random debris, indeed. But not always. Look up the "machine of
Antikythera", for example.
It goes without saying that there many weird metal artifacts, including weird swords, had been dug up and confined tothe basement
Khorasani, in his magnificent book, shows one weird sword. It is actually displayed in the Teheran Museum
but nobody seems to have taken notice. Others turned up in auction catalogues. Here are a few:

Iron, Steel and Swords script - Page 460

Weird swords
Left: Auction catalogue; identified as Luristani, 1000
BC.
Middle: Teheran Museum, dated to probably 1000 BC.
Right: Auction Catalogue "Hermann Historica" 2015,
supposedly Celtic
The sword on the left, believed to come from Luristan, is 91 cm long. It looks like it has a cast-on bronze hilt of aquite unusual shape since it has no pommel or lobes or other enlargements ensuring that the hand doesn't slip.
The Teheran sword was confiscated; its length is 104 cm; the blade alone measures 75 cm. What at a first glance
looks like a long rusty tang is actually a cast-on slender bronze hilt that tapers to a point instead of of having a
pommel of some kind. Its design and the way it is fixed to the blade seems to be unique. It is definitely very
unusual.
Both swords are of the "bi-metal" type with an iron blade and a bronze hilt. M;ore to those sword here.
The "Hermann Historica" sword is described as: "Eisernes Griffzungenschwert" (Naue II), South-East Europe, 8th
century BC. It is an exact copy of a bronze sword, a rather unusual thing. Here is a rather similar one.
Both swords have not been excavated so it is possible that they are fakes. It is not likely however, because nobody in
his right mind fakes unknown objects. What makes these two swords so special is the fact that they seem to be theonly long iron swords on (easily accessible) record for the first millennium BC in the East Mediterranean / Middle East!
That is quite remarkable, if you think about it.
Could these swords be younger than 1000 BC? Well, yes - but they also could be older. There is just no way ofknowing, short of doing a C14 analysis.
Could these swords be Celtic in origin? The Celts, after all, did make it to Anatolia in 278 BC - as hired
mercenaries. Even before that they were employed as fearsome warriors by Mediterranean potentates. They did
have their long swords then and earlier. Maybe a few made it to the East as booty from some battle or as trade
object.
I do not think that this is a good explanation of the swords above but so far it seems to be the only one.
Constant warfare was a fact of life in the East Mediterranean / Middle East, just as about everywhere else. Why did we
not find long swords in all the stuff dug up from about 1000 BC to 0 AD? The simplest explanation would be that there
weren't many around. Depending on the fighting style, a long sword is not necessarily a good weapon. The Roman
army, after all, did rather well for many centuries with the short gladius and the pilum (spear). Long swords or spathas
were weapons for mounted warriors or crazy single-fighter egomaniacs like the Celts.
Iron, Steel and Swords script - Page 461

Long swords also make sense for executioners. From there it is a short way to long swords becoming symbols for
power over life and death, a symbol for the King. As a side benefit a normal King, not to mention a King of theuniverse, looks so much better with a long heavily embellished sword (in addition to his gold dagger or akinake) thanwith a short one.
The hilts of the swords above make them not particularly fit for fighting. The balance without a pommel must be
rather awful, and your grip could not have been very secure either. It is conceivable that they were only for
representation, sort of highlights in the collection of strange war trophies. The hilt must have been added locally, and
it is conceivable that is was made deliberately in a strange shape to emphasize the exotic nature of the sword.
This is all wild guessing, of course. But more than that I cannot do.
There is a whole literature out there about long swords vs. short swords, and thrusting vs. slashing in fighting. Add
fighting modes like single combat style to phalanx (closed ranks) style, fighting on horseback other mounted warriors or
foot soldiers, and you can come up with endless lists of who should have had what and when. Add on top a certain
amount of human stupidity, like fighting tanks on horseback because we are a cavalry unit after all, and everything ispossible. The introduction of the metal shields, for example, might have changed fighting style from thrusting (shortswords) to slashing (long sword or axe). Or maybe not.
Then it also matters to whom size matters. No to women but to men; excuse me: not so much to the disciplined
Roman soldier who just did his job but to the Celtic egomaniac who never ceased to believe that bigger is better, nomatter how often he was rejected.

1)

JUSTYNA BARON and BEATA MIAZGA: "Scythian akinakes or medieval kidney-dagger? Archaeometric study of a
recent find from Legnica (south-western Poland). Article in: Archaologisches Korrespondenzblatt · January 2013

Iron, Steel and Swords script - Page 462

11.2 Swords of Celts and Romans

11.2.1 Background to Celtic Swords
Preface
About everything relating to Celtic swords can be found in Radomir Pleiner's book "The Celtic Sword". So go, read it.
Or read on. That's much easier for two reasons:
1. You won't be able to get Pleiner's book. It is out of print and not available on the second-hand book market.
2. It contains 211 pages. What follows is based on Pleiner's book to a large extent but will be much shorter and fareasier to read. It is also less specific and less accurate.
The first thing to note is that there is no such thing as "The Celtic Sword", just as there is no such thing as "The
German Car". True, the German (or better Suebian) Carl Benz did make the first gasoline-driven car, and his wife Bertha
took it upon herself to go out on the very first car ride, but in the 126 years that followed many different types of Germancars evolved. There were even periods without decent cars. Other countries also made cars, based on inventions of theirengineers, and in actual fights (on racing courses) German cars even lost on occasion. Nevertheless, almost anybody inthe world (provided he is male) associates something specific with the denomination "German cars".
It is pretty much the same with "Celtic iron swords". There is something to that classification but it is neither welldefined nor clearly distinguished from "Non-Celtic" iron swords of the time. Celts also used bronze swords for quite
some time in parallel to iron swords. Then there were periods were only few Celtic swords were found, times wereswords were predominantly found in the graves of chieftains, and times were they were found in common graves.
Sometimes they were rather long, sometimes rather short. Hilts came in various shapes, and scabbard design
could be rather plain or rather complex. Then there are a few exceptional, totally atypical swords:"Knollenknaufschwerter " with very long thin blades having a more or less square cross-section, altogether rather
similar to the much later rapiers .
Nevertheless, with a little bit of background knowledge you know a Celtic sword when you see one.
Why do I start with Celtic swords after having discussed early Near-East swords? Because we have plenty of Celtic
swords and because they are among the oldest long iron swords we are aware of. More important: they are the mostadvanced iron / steel objects of their time, demonstrating some new degrees of cunning as far as working with iron andsteel is concerned.
What exactly defines "The Celts" is not all that clear but they certainly did run
around Europe and the Near East a lot in the second half of the first millennium BC,
wielding big swords of bronze or iron. I gave you a whole module on this already.
They were out to make booty and not to build an empire and eventually succumbed(around 0 AD) to the better organized and more disciplined Romans (the Celts were
not proto-Germans, obviously!). And nobody would have called them "Celts": The
Germanic tribes called them "Walah", the Greeks "Galats", and the Romans"Galli". Celtic tribes had names like Boii, Lingones, Senones, Insubres, Gaesatae.
In 390 BC a Gaulish=Celtic warband first defeated the Roman army at the Battle ofAllia, moving on to sack Rome in 387 BC. Then they left again with plenty of gold
and the well-known quip: "vae victis" (woe to the vanquished).

SpecialModuleThe Celts

The Roman empire at this time was small and confined to Italy whereas Celtic tribes controlled a much larger area.
This map gives an idea of what the Western Mediterranean empires looked like around 600 BC - 300 BC and how
the Celts related to their neighbors:

Iron, Steel and Swords script - Page 463

The Celts and other powers in the "West" around 600
BC - 300 BC
Large picture
Source: Wiki common; Alexikoua.

Why do we have so many old Celtic swords, often in excellent conditions, while we have hardly any Greek iron swords
and not too many Roman ones? I don't know for sure. One reason I can think of is that early archaeologists digging up
the quite visible remains of ancient Egypt, Mesopotamia, Greece, Rome and so on simply did not care for occasional
pieces of rusted iron or remains of smelters and forges. They treasured well-preserved bronze swords if they foundsome, and rusty remains if they were associated with some gold, but other stuff might have been gone unnoticed. Not
that I blame them. There were simply far more exciting things to discover than rusty swords, not to mention that much ofwhat we know today wasn't known then. However, when pretty much all you dug up were Celtic swords like in La Tène ,you had to take notice.
What we dig up iron-wise today is closely related to the way old cultures used their metal things. Let's look at extremes
with respect to swords to illustrate what I mean.
1. A sword was the ultimate symbol of a free man. You received your sword at some coming-to-age ceremony fromsome authority, you treasured it and gave it a name. It went into your grave with you (or was passed on as holy
heirloom).
2. A sword was one tool among many needed by soldiers. You got it as standard issue with your other gear, andyou gave it back when no longer needed. You had no emotional attachment to it. The iron might have been
recycled in peaceful times.
The Celts and in particular the Germanic tribes lumbering in the North-East (and the Japanese, the Parthians andothers) leaned more to the first extreme, the Egyptians, Romans, Greek and others more to the second. King Tut
did have his khopesh (sickle sword) among his grave goods but it had no special status. Egyptians ranking below a
Pharao did not have swords in their graves as far as I know.
If swords were not conscientiously put into a special place like a grave or sacrificed by throwing them into rivers,
lakes or bogs, chances are small that we will find much today. It goes without saying that the sword-conscious
societies were also the ones with a tendency to sacrifice the swords of the beaten enemy (not to mention thesurviving enemies).
As far as the development of iron / steel technology in certain cultures is concerned, we simply can't find out muchwithout having some artifacts. Whatever, for example, the ancient Greeks or Egyptians did in this respect, we hardly
know. That is deplorable but probably no big loss. It stands to reason that the development of iron / steel technology
mostly took place in societies that attached importance and cult status to swords.
The Celtic Sword as Seen by Writers
The written history of the Celtic sword actually begins with remarks of Greek and Roman writers about the Celts ingeneral and their swords in particular. However, Roman and Greek history writers often lied, just like governments ingeneral and the American Government in particular, or some writers of some Holy Books, and we should not necessarily
believe everything we read. The Celts chose to be illiterate so we have no accounts from them before about 500 AD
when some written stuff with roots to Celts appeared in Ireland. Celtic culture could survive there for some centuries
because the Romans never bothered to invade the Island.
About the earliest writer dealing with Celts and their swords is the Roman Polybius (ca. 208 BC - 125 BC). Polybius
was a cavalry commander who got around and a writer of history books. He has a lot to say about Celts, certainly quite
a bit from his own experience. But he also recounts earlier stuff from accounts of other writers that are now lost to us.
Even before the Celtic Senone tribe under Brennus sacked Rome for the first time in 387 BC, the civilized citizens southof the Alpes ("cisalpine") got to know the "transalpine" Celtic people from the raids inflicted on them. All authors
recounting these events agree that the citizens of the Cisalpine regions "were horrified by the savage way in which the
Celts prosecuted their campaigns. The hordes of men with their unusually large physiques and barbarian battle-customs
filled them with terror of the Gauls. Celtic warriors provoked their enemies before battle (writes Diodorus) with 'senselessbravado' (Dionysius of Halicarnassus), threatened them by shouting, singing, and by brandishing and clashing theirarms. They immolated (=sacrificed, e.g. as ornaments to a bonfire) their captives and decapitated the enemy dead. The
ritual basis of these practices is reflected in reports by Diodorus, by Strabo and Silius Italicus. The desperate aspect of
the naked fighting men of the Gaesatae, equipped solely with their arms and golden ornaments created a horrificimpression (Polybius). The nudity of selected warrior groups was certainly based on symbolic and ritual approaches tolethal combats, and achieved a considerable psychological effect" writes Pleiner.
Here are a few direct quotes:
Dionysius of Halicarnassus (end of the first century BC):
"Thus at one moment they would raise their swords aloft and smite after the manner of wild boars, throwing thewhole weight of their bodies into the blow like hewers of wood or men digging with mallocks, and again they would
deliver crosswise blows aimed at no target, as if they intended to cut to pieces the entire bodies of their adversaries,
protective armor and all ..."
However, he continues:"While their foes were still raising their swords aloft, the Romans would duck under their arms holding up theirIron, Steel and Swords script - Page 464

shields, and then stooping and crouching low, they would render vain and useless the blows of the others, whichwere aimed too high, while for their own part, holding their swords straight out, they would strike their opponents in
the groin, pierce their sides, and drive their blows through their breast, into their vitals."
Most ancient accounts generally describe swords as the weapons of the rank-and-file, often accompanied by aspear. But other authors state explicitly that the sword was the main weapon of the Celts.
Plutarch (ca. 46 – 120 AD) relates that the strength of the Gauls depended on their swords.
Livy (59 BC – AD 17) states that the Galatae in Asia Minor had no other offensive weapons than swords.
Dionysius of Halicarnassus wrote: "As weapons of offence they (the Celts) have spears and very longslashing blades"
Diodorus Siculus (first century BC) states: "In place of the short sword they carry long broadswords."
However, there is also some agreement on the poor quality of the Celtic swords.
This does not necessarily mean that the quality of the iron / steel was bad but thatthe weapon was not efficient against Roman gear and fighting styles. This leads right
into the famous paragraph found in The Histories of Polybius II where he describes
the battles of Cannae (216 BC) and Telamon (225 BC):"The Romans are thought to have managed matters very skilfully in this battle, their
tribunes having instructed them how they should fight, both as individuals andcollectively.
For they had observed from former battles that Gauls in general are most formidable
and spirited in their first onslaught, while still fresh, and that, from the way theirswords are made, as has been already explained, only the first cut takes effect;
after this they at once assume the shape of a strigil1), being so much bent
both length-wise and side-wise that unless the men are given leisure to rest
them on the ground and set them straight with the foot, the second blow isquite ineffectual.
The tribunes therefore distributed among the front lines the spears of the triarii whowere stationed behind them, ordering them to use their swords instead only after the
spears were done with. They then drew up opposite the Celts in order of battle andengaged. Upon the Gauls slashing first at the spears and making their swords
unserviceable the Romans came to close quarters, having rendered the enemy
helpless by depriving them of the power of raising their hands and cutting, which isthe peculiar and only stroke of the Gauls, as their swords have no points.
The Romans, on the contrary, instead of slashing continued to thrust with theirswords which did not bend, the points being very effective. Thus, striking one blow
after another on the breast or face, they slew the greater part of their adversaries".
Pure slander as far as all those Celt aficionados out there are concerned. But,
maybe, it's true? We shall see.
Polybius did have on thing right: If you are fighting naked, without armor, you areparticularly vulnerable to opponents who are skilled at thrusting with their (short)swords. As Vegetius Renatus (4th century AD) wrote, looking back: "They [theancient Romans] were likewise taught not to cut but to thrust with their swords. For
Romans not only made a jest of those who fought with the edge of that weapon, but
always found them an easy conquest. A stroke with the edge, though made withever such force, seldom kills, as the vital parts of the body are defended both by thearms and armor. On the contrary, a stab, although it penetrates but two inches, isinvariably fatal."

A strigil

So far the reports from the side fighting the Celts (and, of course, winning all the time). From the other side we only havewhat archeologists dug up. We also can try to put things together from several written sources and do a bit of reading
between the lines.
What emerges is that the Celts were not always wildly energetic but ill-disciplined single fighters; at least some
Celts at some time engaged in organized warfare. They were among the first ones charging and fighting fromhorseback, i.e. acting as cavalry. They also used chariots (after that had been out of style for centuries).
The "TRUTH" is not black or white but grayish, it seems. One fact, hover, remains: The Celts in the 5th century BCor so were on the verge of turning into a "High Culture" with the concomitant empire building. They didn't - whereas
the Romans did.
Finding Celtic Swords
Where does one find Celtic swords? There are three major sources:
1. Graves. From simple graves of normal people to the huge tumuli or barrows erected for VIPs, full of goodies.
2. Places of sacrifice or concealed hoards. There one might find lots of stuff in a small area.
3. Accidents. Artifacts get ploughed up in a field or trenched up from river beds, for example.
Let's look at a few examples.
Iron, Steel and Swords script - Page 465

3.
What comes first to mind concerning Celtic graves are the Hallstatt graves that gave the name to the "Hallstattculture", and the large graves below major tumuli in South Germany like the "Klein Aspergle" or Hochdorf in my oldromping grounds.
Hallstatt today is such an extremely picturesque small town that the Chinese havecreated a copy of the whole thing, so they do not have to travel all the way to see
it. The original is located in Austria, not too far from Salzburg. In 1846 the Hallstatt
community exploited the salt mines in the area, like their predecessors for the last
several thousand years, and it was then that a large prehistoric cemetery of proto
Celts or whatever you like to call them was discovered, yielding more than 1000
burials.
A time line from 1200 BC to about 500 BC is covered in Hallstatt, and the 800 BC 500 BC range marks the start of the European iron age and the Celtic culture.
Among the many metal objects found were (mostly bronze) swords, and among theswords were some special ones that appeared in bronze, in iron, and in mixes.

SpecialModuleHallstatt

Quite similar stuff was later found in many places in Europe and these swords are commonly referred to as
Mindelheim sword or Mindelheim type. About 100 Mindelheim swords have been found, 60 have iron blades. They
are decidedly of the slashing type, rather long, and often come with a characteristic "Mexican hat" pommel:

Mindelheim-type swords from Hallstatt.
A prime example of a Mexican-hat Mindelheim type iron sword was found in Oss, Holland; rather far North incomparison to most other finds.
Some other types of swords were found too. The so-called Guendlingen sword was quite prominent and mostly
bronze; from 180 known swords only 18 have iron blades. Here are a few pictures. Books could be written (and havebeen written) about the Hallstatt swords and all the other stuff but never mind, I give you Kirk Spencer's short article
about the Mindelheim (and Gündlingen) swords instead. Now let's consider the swords from the big graves of majorchieftains if not kings.
Well - tough luck. There aren't any worthwhile mentioning. In fact, even in Hallstatt the swords got shorter and moreinsignificant as time moved on. The big Mindelheim-type swords shown above are from the so-called Hallstatt C
period, about 800 – 600 BC. In the Hallstatt D period (600 – 475 BC), elaborate show-off daggers replaced the longsword as the essential weapon put in the grave (besides often a spear). Here are a few examples. The comparatively
large cities going with the big barrow or tumuli graves fall in this period.
The Celtic "Fürst" (more or less a King), as these guys are called in German, didn't need a sword anymore toadvertise his power and prowess in battle. He had underlings for the dirty jobs and showed his position by imported
Iron, Steel and Swords script - Page 466

luxury items as shown here
Graves are good places for digging but places of sacrifice or hoards aren't bad either. While much rarer, you get morethan one sword per dig. The problem is that it in contrast to graves, it is not always possible to figure out why several
swords (and other goodies) were deposited in one place or within a confined area. Maybe somebody was just hiding his
goodies from the incoming enemy? Maybe a ship with several warriors went down, depositing their goods in a river bed?
Some finds however, can be best understood by assuming that the goodies were sacrificed, conscientiously thrown into
a bog, for example. That will come up in a major way again when I come to the Nydam treasure about 600 years into the
future.
Now look at this picture:

La Tène swords
Large picture
Source: A somewhat different version of this picture was originallyassembled by Kirk Spencer from the Sword Forum Family.
The pictures themselves come from the book of J. M. De Navarro 2)

All these swords (and more) were found close to the small village of La Tène in
Switzerland, situated right at the shore of the Neuburger See (Lac de Neuchâtel).
The name of the village, like Hallstatt, served to identify the La Tène culture. The
La Tène culture stretched over a huge area of much of Europe and it is a bit ironicalthat the town of La Tène was right at its southern edge. The "early" La Tène culture
is dated to (450–250) BC; the late one to (150 - 0) BC; in between is "middle La
Tène". All the swords above are from the middle period.
La Tène is also just right beyond the borderline where the Swiss switch from talking
German to talking French. It thus comes as no surprise that the archaeologicalhistory of La Tène is a mess. No - I didn't mean that. The early excavations wereactually supervised by a Oberst (Colonel) Friedrich Schwab, a German officer.

SpecialModule
La Tène

La Tène is not the only place where Celtic swords have been found in bulk, although it certainly leads by sheer
volume.
Then we have the accidental finds. During peat digging around Lindholmgård in Denmark an almost perfectly preserved
La Tène type sword with its scabbard came up, for example:

Iron, Steel and Swords script - Page 467

Lindholmgård sword. Almost like new!
Large picture
Source: Photographed in the Copenhagen museum

Also during peat digging the world famous Gundestrup cauldron was found, also from the La Tène period. And soon. Sometimes special swords turn up, like the ones with an anthropoid hilt, typically found in graves of the very richand important in later times (1st century BC).
The long and short of all this is: There are plenty of Celtic iron swords for performing a thorough investigation into their
metallurgy and the processes employed for making them. So let's see what has been done in this respect.

1)

A strigil is a small, curved, metal tool used in ancient Greece and Rome to scrape dirt and sweat from the body before
effective soaps became available. Showers and towels had not been invented yet either.

2)

J. M. De Navarro: "The finds from the site of La Tène" Oxford University Press (November 1972)
The first (and unfinished) attempt to get some order into the La Tène finds.

Iron, Steel and Swords script - Page 468

11.2.2 Metallurgy of Celtic Swords
What to Look For
What do we know about Celtic swords from a Materials Science and Engineering point of view? Quite a bit - and notenough!
We already have some idea about the production of Celtic iron and steel in bloomeries and the kind of quality they could
achieve. I gave you three examples:
1. The "Ferrum Noricum". While the term is usually associated with the Roman iron production around 0 AD, theCelts or proto-Celts were there earlier. The place is not all that far from Halstatt, after all.
2. Snowdonia, a place in Wales, where the local strain of Celts made iron and steel.
3. Wetzlar, as an example of an area where iron production in bloomeries was done from about 800 BC to 1200 AD
by the Celts and whatever other culture happened to be around within this time span.
We know from these examples that iron making in early bloomeries - during the Halstatt and early La Tène period,say - was a tricky affair, producing small blooms of uncertain quality. We know even more. We can be certain that
only a tiny percentage of the sites where the old Celts ran bloomeries has been discovered by now. We can also be
certain that the way the bloomeries were run and the bloom was processed differed from place to place and fromtime to time.
You and I know even more then most archaeologists who worked on Celts. We know that we don't have to ask
ourselves how the old Celts made steel because we know that their bloomeries produced (wrought) iron and steel
and not just exclusively wrought iron as all and sundry believed not that long ago (some still believe that today). Thatmeans that we do not have to worry about how the old smiths "carburized" their wrought iron. We know that thatwas not the way they made (bulk) steel for the simple reason that it can't be done.
What we do have to worry about is how the old smiths picked different grades of iron from a given bloom.
One can't discuss Celtic swords without mentioning the special ones. Besides the "Knollenknaufschwerter " alreadymentioned, we have the ones with an "anthropoid" or human-like (bronze) hilt (see below) and the "antenna hilt" type.
Those are very distinctive hilts but the blades seem to be no different from the more usual ones.

Anthropoid bronze hilts on iron Celtic swords /daggers (late La Tène)
Far more
Source: Left: Photographed in the British museum. Right: North
Grimstone / Yorkshire sword

We also know that iron / steel was traded. The Celtic double pyramid or bipyramidal iron bars go back to at least 450
BC. The so-called "currency bars" or "sword bars" (much better German name) go back to at least 200 BC. They
consisted of rather inhomogeneous iron / steel, just like the Roman standard iron bars centuries later.
A Celtic sword smith thus definitely had access to iron / steel. He either bought some of the standard stuff fromtravelling salesmen, from the local iron monger, or he made it himself. Then he made a good-looking sword. We knowthat he could do that because we have them, see also the examples above.
Now we have to ask a tough question: Was it just a good-looking sword or also a good sword? There is a difference,just think of (insert name of your choice).
So let's assume you got hold of an old Celtic sword. Let's also assume you have a metallurgical lab at your disposalthat allows you to analyze your sword to your hearts content. So what are you going to do?

Iron, Steel and Swords script - Page 469

If you are new in the business you would tend to run samples through all the equipment you have got. I see that a
lot when I referee science papers from countries that are rather new in the R&D business. They have a piece ofsilicon with some trimming (maybe its porous on one side) and run it through all they have. Lo and behold, X-ray
diffraction shows unambiguously that this piece of silicon actually consists of silicon, and scanning electron
microscopy leaves no doubt that on the polished surface nothing can be seen. I kid you not.
Back to swords or to doing material analysis proper. The kind of analytical method you want to use depends on thequestions you want to find answers for. So consider your questions. Then consider that not all questions are equal.
Some questions are just nonsense, some have only wrong answers. You want examples? OK - here goes: is anelectron only green whenever it is not red? Should your wife wear item 1 or item 2 for whatever function you are going to?
With respect to swords a not-so-smart question would be: is Polybius right? Can you find an answer to that question by
analyzing your sword? No you can't. You might find that your sword is easy to bend but that does not prove that theswords Polybius saw in action bend easily, too. If you analyze a lot of Celtic swords, and they all bend easily, than you
might say that there is a strong probability that Polybius was right. In other words: if you only have results from one
specimen (or from just one location on the specimen), it is dangerous to generalize.
A good and interesting question could be: What is the average carbon, phosphorous, and so on, concentration in theblade? That is a question you can answer. The price, however, is the complete destruction of the blade. This is usually
not permissible so you need to compromise.
If you now think long and hard you will eventually come to the conclusion that the best compromise between
destroying as little as possible while getting the best possible results for answering relevant questions (I come tothat) isLook at the structure of etched cross-sections.
Do micro-hardness tests on these cross-sections.
Determine the concentration of some critical elements like phosphorous and manganese from a few small
samples.
You want to do that for a sizeable number of swords that represent a certain age and culture in order to get somefeeling for what is typical.
It needs only some quick thinking now to figure out the serious drawback to this approach: It's a lot of work! It willtake years of skilled and hard work. You can only attempt this if you are a professor who can command cheap
skilled labor also known as graduate students, people who love to do stuff like this as we have figured out before.
I sure hope that Radomír Pleiner had plenty of graduate students helping him to do his rather long and involved work
as described above. Pleiner analyzed about 120 La Tène iron swords from 400 BC - 200 BC in great detail anddescribed the results in his book. In what follows I will try to summarize his results.
But first let's consider the questions we would like to get answers for. They are not so different from the questions
we have asked with respect to the Luristani swords:
1.
2.
3.
4.
5.
6.
7.

Are the swords made from one piece or by "piling", i.e. by fire welding several pieces?
Was the material first homogenized by "folding"?
Did the smith conscientiously use different grades of iron / steel if fire welding was used?
Was the smith aware of the "phosphorous issue"?
Was the smith aware of surface carburizing or, far more important, de-carburizing during forging?
Did the smith know about hardening by quenching?
Capability of the smith? His infrastructure? Stone hammer and stone anvil on the floor or dedicated special
equipment in a forge with a hearth?
A First Result of Pleiner

Let's start by looking at one result of Pleiner's work and then take it from there.
Here is a picture of the sword "Tuchomysl 6.13, NW Bohemia". The two places where a half cross-section has been
cut out are marked by arrows. Below is a low-magnification view of the etched cross-section. The greyishness
roughly marks the carbon concentration; it increases from light to dark.

Celtic sword and half of the etched cross-section
SourceIron, Steel and Swords script - Page 470

What you can see quite clearly is that you can't see much. You need to look at many pictures at high magnification if
you want to get an idea of what is there. But you can't publish that; editors do not enjoy square-meter sized
photographs for science journals or books. You must render your results publishable by making schematic drawings likethis one:The schematic structure of the cross-section of thesword above
The carbon concentration decreases from red to grey.
Source. Adopted from Pleiner

The black lines mark weld seams (not always clearly discernible), the colors the rough carbon concentration. In
addition, micro-hardness values are given for the positions indicated.
What we can conclude, being ever so careful 1), is:At least one Celtic smith used pilingconscientiously. And he did not harden
by water-quenchingNot bad. But then Pleiner looked at many swords and now we must take note that the sword above was about "TheBest". Before I go deeper into this, let's look at a much earlier "analysis" of Celtic swords found at Marix (wherever thatmight be), assigned to one Colonel Verchère de Reffye. In a 1866 book 2) he is quoted as follows:'"'We may remark,' he says, ' that the cutting edges of these swords are not of the same iron as the body of theblade. The workman, after having forged this part out of very tough iron (tres-nerveux, very fibrous iron), drawn out
lengthwise, welded on each side little strips of soft iron to form the cutting edges; this iron was afterwards beaten toan edge by the hammer. The soldier could thus after the fight repair with the hammer the damage done to his sword,
just as a reaper sharpens his scythe when it is notched."
Could that be true? Celts made swords with a hard core and soft edges? Yes, indeed. Some Celtic swords had softedges, and, as we shall see, some pattern-welded blades made 700 or so years later were built the same way. I
knew about this phenomena before I knew about the Colonel's explanation for this. His explanation was one of thetwo that had occurred to me, too. The other one is that the smith was drunk.
It's time for making a statement that might come as a surprise for some:Swords of the same kind are typically very different in theircomposition and construction
This is true for the Celtic La Tène swords I'm looking at here, for pattern-welded swords, Viking swords, and so on.
After a PhD student I'm advising dug out a medieval smithy (800 AD - 1200 AD), he analyzed about 10 remains ofknives and found everything! Perfectly constructed blades with a hard edge and a soft inside, blades banged
together randomly from up to 5 kinds of iron / steel, and anything imaginable in between these extremes.
The statement is probably also true for many other kinds of old swords (e.g. "wootz" blades) but one needs toanalyze a large number of swords of the same kind to be able to prove or disprove that statement, and that has
mostly not been done.
What that signifies is not really clear. One might assume that some smiths were very good, some very bad, and therest in between, but that does neither help much nor can it be concluded from the still far too few data.
Iron, Steel and Swords script - Page 471

Celtic Swords According to Pleiner
Pleiner gives very detailed statistical data that I need to simplify to make them digestible. They are also slightly garbled
on occasion, like percentages not adding up to 100 %. The numbers in what follows are therefore always justapproximations or order of magnitudes.
I will run through the major findings by answering questions.

1. Were swords forged from a single piece of iron / steel, e.g. from a currency bar or a part of a bi-pyramidal piece?
Yes! Some but not many of the swords investigated were made from one piece as far as one can tell. In this casethe material was typically wrought iron to mild steel.
Pleiner also employed a smith and with his help figured out a few points about the making of swords. For example,
they proved that it is possible, indeed, to forge a blade from one piece of iron just with a hammer. Possible but noteasy.

2. How about the material? Wrought iron or steel?
About 40 % of the swords investigated were made from wrought iron or mild steel - and characterized by Pleiner as"inferior". The "single-piece" swords are part of this group. The rest contains some steel. The wrought iron group,
however, includes iron with appreciable concentrations of phosphorous, and the blades may be harder than
expected for pure wrought iron.

3. What about fire-welding pieces together? That is a tough questions for several reasons. Before I address it, I need to
get the vocabulary clear:"Piling" is the general word used for the process of making a bigger piece of iron / steel by fire-welding
several smaller pieces.
"Folding" is the term used when you weld one piece of iron / steel to itself by, well, folding it.
"Faggoting" is the term used for making a piece of iron / steel more uniform by folding and stretching several
times. The word does not address the process but the intended result. The link goes deeper
Piling itself can be done in many ways. I list them here in increasing order of sophistication:"Random structural piling" means that the shape of the pieces welded together didn't matter.
"Random compositional piling" means that no discernible strategy was followed in choosing the carbon /phosphorous content of the of iron /steel welded together. Random structural piling is mostly random as tocomposition, too.
"Structural piling" means the opposite. The pieces to be welded have defined geometric shapes. It still
could be random compositional piling, though.
"Compositional piling" tries to establish special compositions in selected parts of the object, e.g. hardedges / soft core for a sword. It is then automatically also structural piling.
"Pattern welding" is a sub-group of compositional and structural piling or welding. The different pieces ofiron / steel are welded in such a way that an intended pattern becomes visible on the surface after somesuitable etching or other treatment.
This is essentially a list of options for the smith. It is rather clear, and a smith might go for any of the fivepossibilities (and mix everything a bit, too). There is no problem for the smith.
There is a problem, however, for the archaeometallurgist looking a the product much later. He might find one ofthose swords with a hard inside and soft edges made by "face welding" (see below) a soft iron piece on both facesof a hard core piece. While this indicates structural piling it is not clear if the smith also attempted compositional
piling. That would mean that the smith, for reasons of his own, wanted to make a soft-hard-soft structure and knew
exactly what he was doing. But the smith just as well might have taken pieces at random and the soft-hard-soft
result is purely accidental. The same question comes up for all those swords where just one edge consists of hardsteel.
In the same vein, random compositional piling might produce a blade that develops a pattern on its surface aftersome suitable treatment. It is not pattern welding, however, since that pattern was not intended.
One last problem needs to be addressed. If a smith piled pieces of the same kind of iron in whatever way, we may
not be able to see that. Well-done welding seams in this case are not easy to recognize after a few hightemperature treatments. What looks, for example, like a uniform piece of wrought iron might well have been madeby piling. The opposite might be found as well: clearly recognizable welding seams even so no piling by the smith
took place. In this case we look at welding seams that go back to the consolidation of the bloom and the forging of
the half-products like the bipyramidal bar.
Now you are prepared to appreciate the magnificent work Pleiner has done in the face of all these vagaries.
Look at the picture below that shows how old Celtic smiths made not-so-hot swords by structural piling but with notmuch regard to compositional piling. They just piled thin wrought iron / mild steel bars in order to get a blade:Iron, Steel and Swords script - Page 472

The various (random) piling geometries of wroughtiron (W.I.) swords
Source. Adopted from Pleiner

Note that one or two cross-sections are not necessarily representative for the whole length of a blade. But what
becomes clear in any case is that Celtic smiths used many different ways to construct sword blades by fire or hammer
welding wrought iron or mild steel bars. Some piling might have been random, in other cases the smith might have madean attempt at structural piling but essentially failed.
This looks a bit stupid on a first glance. If you fire weld a few pieces of wrought iron, the result is one piece of wroughtiron. So why bother?
Here are some possible reasons.
1. The smith must first have made the relatively small wrought iron bars needed for welding. And he could havemade them by cutting off small pieces from a bipyramidal bar that he stretched out to a long bar with somefolding in between. In other words: he was fagotting his pieces. It is most likely easier to fagott or
homogenize several small pieces than one large piece by folding. Fire welding the smaller pieces than
produces a more uniform large piece than working with the raw material directly.
2. Phosphorous was employed to harden the wrought iron ferrite. We have already seen that this "works" tosome extent. Of course the smith had no idea about phosphorous but knew perhaps that welding pieces fromdifferent suppliers (with different phosphorous content) gives good results. Or he had other reasons. It is
impossible to fully assess phosphorous issues from one cross-section but it is possible to determine that
phosphorous played a role and that might have been an inducement to piling.
3. The smith knew what he was doing but we don't. His reason might have been good or just plain BS andsuperstition; we simply don't know.
Whatever these smiths thought they were doing, and however skilled they forged their iron, their blades were notvery good. They were rather on the soft side everywhere. However, all the piling might have made them somewhat
more resistant to fracture.
Before I go on to better blades made by structural piling, I need to outline the three basic geometries used for structuralpiling:Iron, Steel and Swords script - Page 473

The three essential welding geometries
Source. Adopted from Pleiner

The picture is sufficiently clear and needs no long explanation. If you imagine more than two colors for different iron /steel grades, you see that a lot of different structures could result. If you go for face welding or staggered welding
you need to start from a few thin and wide bars or sheets, if you go for butt welding you need a number of longrods with more or less square cross-sections. Butt welding is obviously more involved than face welding.
The question of course is: which way of piling is the best? The answer, as always, is simple: it depends! On all
kinds of things but also on how well the smith can fire-weld. I'll come back to this.
It's time to look a the more interesting swords that Pleiner found in his investigation, the swords that contain medium tohigh carbon steel. Here are the types of cross-sectional structures found:

Cross-sections of Celtic La Tène blades showing piling
structuresand carbon concentration (scaling with greyishness)
Source. Adopted from Pleiner

I'm not going into details because that would take forever. Even so it becomes quite clear from the picture that:
Some Celtic smiths were able to to produce good swords with hard edges by doing compositional piling,sometimes in a rather complex way.
Some Celtic smiths produced swords with soft edges (e.g. No. 6 above), quite likely by compositional piling.
Why they did that we don't know.
Some smiths made complex asymmetric structures, at least to some extent by compositional piling. Again
we do not know why.
There are several blades with just one hard steel edge. This might be accidental but it seem just as likelythat this was done intentionally by compositional piling in various ways.
A few blades get close to pattern welding. However, the iron / steel rods were usually not twisted and it does
not appear that the smith wanted to produce a pattern. There is only one exception (No. 12) where twisted
rods appear to have been used. This sword looks rather like one from the 2nd or 3rd century AD. However,there are Celtic swords not investigated by Pleiner that show definite pattern welding utilizing "striped rods".
Here is an example
There is no clear indication of hardening by quenching.
Based on Pleiner's insights as outlined above, we can now attempt to answer all the questions from above. Note thatwhenever I say, for example, "Celtic smith" I actually mean1) "at least one Celtic smith at some place in the larger
Celtic regions and at some specific time between 500 BC and 100 BC". From investigating some few 100 artifacts,
found all over Europe and from a time span covering several 100 years, one just can't generalize too much and allnumbers should be seen with error margins of at least 10 %. But using all the necessary disclaimers all the time makes
the text unreadable.
First let's look at a summary of Pleiner's results (with subdivisions only for the "full cross-sections" part):
Iron, Steel and Swords script - Page 474

GroupA Wrought Iron
swordsB

Full cross-section

Half cross-section;parts

40 % (25
Swords)60 % (20 Swords)

A1
No weld

11%

A2
Face welded

16 %

A3
Butt welded

13 %Hard edge swords

60 %(37 Swords)

B1
Two hard edges

40 %

B2
Single hard edge

20 %40 % (13 Swords)

Pleiner defines 6 sub groups for the B1 type swords but that brings us close to the edge of the statistics abyss.
You can't do a meaningful statistical analysis anymore when the number of objects you try to classify is not muchlarger than the number of classes you need. In other words: every one of the swords analyzed is rather unique. I
already needed to show how 18 different kinds of compositional cross-sections to classify about 100 swords!
Here are our old questions once more. Some I have already answered but let's go through all of them anyway; it doesn'thurt to see it twice. The answers are my answers:
1. Question: Are the swords made from one piece or by "piling", i.e. fire welding several pieces?
Answer: Both. But piling is more prominent than one-piece forging; see the table above.
2. Was the material homogenized by faggoting?
Answer: It is quite likely that fagotting was done. But one can't be absolutely sure. You simply can't tell from justone cross-section. The picture in this link, however, might illustrate some faggoting of a Celtic swrod.
3. Question: Did the smith conscientiously use different grades of iron / steel if fire welding was used?
Answer: Yes. Definitely. However, he might have gotten it wrong.
4. Question: Was the smith aware of the "phosphorous issue"?
Answer: Hard to tell. It is noteworthy in this context that about 1/3 of the wrought iron blades had relatively hardedges due to phosphorous. It does appear that some smiths conscientiously picked phosphorous iron for theedge parts.
5. Question: Was the smith aware of carburizing or, far more important, de-carburizing during forging?
Answer: No. There is no clear indication for this.
6. Question: Did the smith know about hardening by quenching?
Answer: No. A very few blades appear to have been rapidly cooled but that is neither certain nor does it seem tohave been done intentionally.
7. Question: Capability of the smith? His infrastructure? Stone hammer and stone anvil on the floor or dedicatedspecial equipment in a forge with a hearth?
Answer: The smiths were rather good. Just to shape a decent sword from a lump of iron is rather skilled work; fire
welding is even more tricky. Some of the fire welded constructions could only have been done by real masters.
There were probably no anvils as we know; forging most likely happened on stones. The set of tools was primitive
but not much different from what you would have found in a 19th century smithy. In the hands of a master they
were very effective. But we hardly know anything about the smiths.
It follows that Celtic La Tène swords look about the same from the outside but the insides could be rather different.
Some bad or mediocre swords were made because the smiths apparently couldn't do better. Alternatively, maybe,
you just got what you could pay for. Some bad or mediocre swords, however, were made with plenty of skill andcunning. Why a smith conscientiously should have made a sword with a hard core and soft edges we don't know.
Then we have well-constructed swords and some quite elaborate ones, leading up to the pattern welding thatreached its full bloom around 400 BC, 600 - 800 years later.
Did you notice that a new big question is lurking in all the questions and answers above? No? Well, you must havenoticed that a lot of fire welding (also called hammer welding, forge welding, ...) was going on. Big deal you might think,that's what happens already during the compacting of the raw bloom, no to mention the forging of bipyramidal bars or
any other form of trade iron. Yes, but making a sword by fire welding several strips of iron in one of the many ways
shown above is a different story. The Celtic smiths could do it - but with varying quality. There are blades with very good
welds and bad welds next to each other.
OK - but what is the question? Here it is:Iron, Steel and Swords script - Page 475

How come ancient Celtic smiths could
do fire welding while modern
Materials Scientist cannot?
As I have outlined before, you only can join iron to iron if you remove the oxide(FeO) first. This is supposedly done by sprinkling some sand (quartz; SiO2) on the
hot surfaces to be welded, liquefying the oxide or scale. The liquid stuff is thensqueezrd out under the hammer. That's what I have told you way back.
In the meantime, however, we have learned that this is a more complicatedprocess. What really happens when you sprinkle sand on the surface is that you
produce fayalite (Fe2 SiO4), the main component of slag. Fayalite is liquid, indeed but only around 1200 oC (2192 oF), a temperature rather too high for normalsmithing. I have alluded to this mystery before and I shall get back to it. Meanwhile
the advanced module gives some more information about the topic.

Advanced
Link
Fire Welding

But now it is time to answer the big question. Was Polybius right? Pleiner devotes several pages to this question,
coming up with: "the metallographic evidence shows that Polybius was right up to a point". Then he goes on to showthat the "point" Polybius comes up to is actually rather low. So my statement is:

Polybius was wrong - up to a point
My reasons are:
1. More than 60 % of the swords investigated by Pleiner would have been definitely good steel swords, not given
to heavy bending on the first blow.
2. From the remaining 40 % wrought iron swords a noticeable percentage would have been hardened byphosphorous and these swords would not have been given to easy bending either.
3. Pleiner had two wrought iron swords made that were "soft" iron throughout and tested them by hitting all
kinds of things. While deep notches were produced, no heavy bending occurred. The swords would havecaused major injuries not only on the first strike but also on many following ones, no matter how heavily
notched or slightly bend they were.
Of course, it is possible that Polybius or his source witnessed a bunch of Celts with particularly bad swords. It isjust as possible that Polybius reported unsubstantiated rumors he had heard, that he exaggerated a bit, or that hewas befuddled because heavily bend Celtic swords do exist, indeed - in the graves of the warriors. These swords
were ritually "killed" by bending and possibly even by notching.
Nevertheless, some Celtic swords might not have made a big impression on Roman legionaries. A badly madewrought iron blade, possibly with some major internal inhomogeneities like large slag inclusion or bad welds, either
from the stock material or from forging, might do strange things after the first blow - in particular if the guy wielding
the sword wasn't so hot either.

A "killed" La Tène typ sword; 100 BC
Source: From burials near Tudvad, Denmark. National Museum
Copenhagen.

1)

A mathematician, a physicist, and an engineer are riding a train through Scotland. The engineer looks out the window,
sees a black sheep, and exclaims, "Hey! They've got black sheep in Scotland!" The physicist looks out the window andcorrects the engineer: "strictly speaking, all we can say is that there's at least one black sheep in Scotland." Themathematician looks out the window and corrects the physicist: "strictly speaking, all we know is that there is at least
one sheep in Scotland that is black on one side."2)

Ferdinand Keller: The lake Dwellings of Switzerland and other parts of Europe" (1866), translated

Iron, Steel and Swords script - Page 476

11.2.3 Roman Swords
An Extremely Short Overview
The "Pax Romana" (the "Roman peace"), lasted from about 27 BC to 180 AD. It was a time of relative peace and quiet
for about 200 years in most of the area shown in color in the map below. The "Pax Americana" by comparison, haslasted about 65 years by now (with the USA actually being engaged in some war somewhere most of this time). The
beginning of this blissful period is connected to the rise of power of Augustus the founder of the Roman Empire and its
first Emperor. He ruled from 27 BC until his death in 14 AD.
If you compare Augustus' empire to that around 300 BC you can see that the Romans did rely on the might of the sword
to an astonishing degree.

The Roman Empire (colors) around 31 AD
Large map
Source: Wikipedia

The empire was already rather large when Augustus started his term. During his reign it grew quite a bit and that didn't
happen by gently persuading the various neighbors to come forward and sign up. Just consider the bit of unpleasantnessthat happened in Bethlehem around 0 AD and again in Jerusalem some 30 years later. Roman legionaries essentiallyconquered all the colored territories outside Italy and radiated enough power from the borders to keep the pink ones inline. The legions won the various battles for all kinds of reasons - but not because of superior swords.
I'm not saying that their swords were inferior. All I'm saying is that they were not very remarkable from a
metallurgical point of view until about 200 AD - 300 AD when sophisticated pattern welded swords appeared. The
team-work fighting style of legionaries, with fancy group maneuvers and so on, was probably far more remarkableand deadly to the undisciplined wielders of long and well-made swords. Here is a picture from the battle in
Sagnlandet Lejre (probably taken with an extremely early Leica).

Roman legionaries
Large picture of the "turtle" formation
Source: Photographed at Sagnlandet Lejre in Denmark, an outdoor
museum where Danes like to play Romans and Barbarians on
weekends.

The legionaries are holding a short sword, the gladius, one of their standard-issue weapons used for centuries
without much change in the general shape.
Iron, Steel and Swords script - Page 477

While most everybody in a legion was a pedestrian, the Romans also had a cavalry ("equites Romani"). In Augustus'
time and later this was mostly a Roman Auxilia (literally "helpers") cavalry, recruited from non-citizens in occupied
territories (called provinces) that had strong native cavalry traditions.
Here is a Danish auxilia training on casual Friday without the prescribed uniform:

Roman mounted auxilia, practising with his spatha
As outlined before, a short sword is not optimal for fighting on horseback. Here you need the real thing: a longslashing kind of sword called a spatha by the Roman and everybody else. The picture illustrates what is quite clear
anyway: If you fight from horseback you simply need a longer sword than a foot soldier.
As far as Roman swords are concerned I have given you a picture already. Before I go into details concerning gladiusand spatha, it can't hurt, however, to have a quick look at the pugio too, the standard-issue Roman dagger. Here are a
few examples:

Late Roman pugiosMore pictures. And even moreIron, Steel and Swords script - Page 478

Source: Archeology Museum Munich, Germany; From the "romancoins"Internet site

Those pugios are from the late Roman period, 300 AD say. I appears that at least the two in the front have a patternwelded mid-rib with a fishbone pattern.
These late pugios look pretty much like earlier ones. Romans were not great scientists, maybe, but they definitely
were good engineers and heeded the first law of engineering 1). Pugios also look a lot like the Celtic show-off
daggers so popular in the graves of nobles after swords disappeared as grave goods.
Gladius and Spatha
Polybius and others Roman writers were making fun of the poor quality of Celtic swords, implying that the Roman ones
were much better. A metallographic analysis should show if that really was the case, and what exactly the Roman
metal workers could do better than the Celts. There is only one problem:

We do not have many gladii and spatha
from the Roman military!
However, we do have many Roman-made swords that were used by the Barbarians in the North and sacrificed by other
Barbarians who defeated them. Fortunately, these guys pitched most of what they took from the dead enemy into a holylake or bog, where some of the stuff was preserved exceedingly well until today. Typically, the swords are from the thirdand fourth century AD and most of them were pattern welded.
I will go into those and other pattern welded swords in great detail in the next sub-chapter. Here I only look at the
Roman gladius and spatha as it was used by Romans typically before 200 AD.
As pointed out before, a Roman legionary did not have an emotional attachment to his gear, in contrast to his barbarianor Teutonic opponent in the North-East. And even if he had, he couldn't take his trusty gladius into the grave with him.
He had to give it back (in good condition) when he left the army - or else. We know from inscriptions that Roman swords
had more than one (temporary) owner. I do believe (or rather hope) that modern armies tend to collect the M16s or
Kalashnikovs too when some soldier is discharged; in millennia to come very few will be found in graves.
To give a number: In all of Great Britain, according to the BBC, altogether 8 spathae have been found so far. I do nothave numbers for other countries and for the gladius but there just aren't many - while we have far more than 1000
Celtic long swords of the La Tène type. That means not only that there isn't much to investigate metallographically
but also that museum curators will be even more reluctant than in normal cases to have these artifacts analyzed.
It also means that we cannot have a good idea for what was typical. Even worse, there are indications that some of
the gladii or spathae found were especially precious ones and therefore atypical. They might have been sacrificed by
the winner and that's why we found them.
Before I turn to the what little data there is, I will look a bit more closely at the objects of interest: the gladius and thespatha. First, let's be aware that Roman legions were running around for about 500 years in much of Europe. We must
assume that the gladius of a guy in Spain might have differed somewhat from the one issued in Turkey at the sametime, and that a 200 BC spatha was different from a 200 AD one. They also differ "somehow" from non-Roman swords
but it is not always easy to put that into into words. Nevertheless, most of the time you know a gladius / spatha when
you see one.
There are plenty of books and articles about the details. A few salient points concerning the gladius (taken from thearticle of Janet Lang 2) are:
The name "gladius" in Latin simply means sword. It is believed to be a Celtic loanword derived from ancient
Celtic "kladi(b)os" or "kladimos"=sword. A gladiator is a swordsman and a gladiolus is a plant with sword-likeleaves.
History: During the conquest of Spain in the 3rd century BC the Romans supposedly encountered the
Gladius Hispaniensis or "Spanish Sword", took over the design and kept it for 600 years or so.
Length: Somewhere between 590 mm and 367 mm. Most, however, come with lengths between 380 mm and
430 mm and there is a good reason for this "shortness": it is the practical length for easy drawing if you only
have one hand for doing this! As a right-hander you then draw your sword with only the right hand from ascabbard on the right side of the body. You need to do this because your left hand holds your big shield. A
long sword typically hangs on your left side and you must hold the scabbard with your left hand while you
draw it out with your right hand.
Shape: Two basic shapes are distinguished. The so-called Mainz type, in use before the middle of the first
century AD, and the Pompeii type after that. The Mainz type had a short, slightly waisted blade about 500
mm long and and a long point, the Pompeii type had parallel edges and the typical triangular tip. It was
relatively short (45–50 cm) but "grew" in length as time progressed until it became a spatha.
There is no clear distinction between a gladius and a spatha. Swords 770 mm long have been described as
gladius although with this length it should be rightfully a spatha.
Iron, Steel and Swords script - Page 479

Here are a few gladii of the two basic types:

Mainz type Gladii
Source: From the "Roma Victrix" Internet site. The top on is in the
Zagreb museum (Republic of Croatia) the other two are from private
collections

Pompeii type Gladii
Source: Left: Guttmann collection; from the site of Bill Blake. Right:
Photographed in the Nijmegem museum, Holland

Now a few words to the Roman spatha. The "Roman" is important because the term "spatha" is used by many as thegeneral term for any straight double-edged sword. There is no clear distinction from a gladius. As a practical matter one
can take the length: A Roman sword longer than about 75 cm we call a spatha.
Spatha in Latin means sword, just as gladius. It probably goes back to the ancient Greek "spathi", a term for awooden blade or paddle. The spade you use for digging (German; Spaten) is language-wise a close relative of thesword. Espada means sword in modern Portuguese and Spanish; the French, as always, mutilated it to épée.
The term "spatha" for sword was introduced by Tacitus (ca. 56 AD – after 117 AD). He used it to distinguish thelong swords of the (unidentified; possibly Celtic or Germanic) mercenaries (called "auxilia" or auxiliaries) from thegladii of the legionaries during the chastising of the rebellious British king Caractacus.
Here are some spathae:

Iron, Steel and Swords script - Page 480

Roman spathae
Source: Top: Herford museum, 200 AD - 300 AD. Middle: Wikipedia.
Bottom, Shrewsbury museum.

The spatha probably came to the Romans via their Celtic mounted "auxilia", the hired Celtic cavalry, in the early imperial
period. Eventually, sort of in the second half of the 2nd century AD, the spatha started to crowd out the gladius. Thatmight be due to the increasing importance of the cavalry and a general change of military tactics. In a paralleldevelopment the sword was carried increasingly on the left side and pattern welded swords appear.
The Metallurgy of Roman Swords
What do we know about the metallurgy of Roman swords (before, let's say, 200 AD)? Not all that much. Janet Lang's
study 2) from 1988 is still the standard; a newer study on Roman armor 3) tends to confirm her findings. There are a
few studies of isolated objects before 1988; the result are covered in Janet Lang's paper.
Janet investigated five Roman swords from the British museum and one from Chichester; below are pictures for 4 ofthem. They are:
The sword of Tiberius. First half of the first century AD.
The Fulham sword. First half of the first century AD
Sword found in the Thames. First to second century AD
Sword found near the Mansion House, London. Late first century AD
Sword from Hod Hill. Mid to late first century AD
Sword from Chichester. First half of the first century AD

Some of the swords investigated
Source: British Museum; Internet

A schematic summary of the findings almost tells it all:Iron, Steel and Swords script - Page 481

Schematic structure of the Roman swords
investigated.
Numbers refer to Vickers hardness
Source: British Museum; Internet

What we have, in short, is:Five different structures for six swords. From rather bad to perfect.
Compositional piling is definitely used.
Hardening by quenching is definitely used.
Going a bit into detail we learn:
The Fulham and Chichester sword might have been made without piling from one solid piece of steel. It is,however, just as likely that traces of piling were obliterated by forging.
The three swords on the right were definitely made by essentially piling wrought iron.
The Tiberius sword was made by piling hard steel to the outside of softer steel.
The swords on the left were quenched and possibly tempered. Tempering could have been done intentionallyor by a quench short enough to leave the inside still hot, heating up and thus tempering the outside
somewhat after withdrawal from the quenching medium.
The smith making the Tiberius blade made the edge by filing / grinding, removing the outside layer of hardsteel in the edge region. That doesn't make much sense.
The somewhat earlier swords (before about 50 AD) are better than the later ones.
Janet Lang goes into some length to discuss these results. Six swords do not allow to extrapolate on other swords,
however, so we cannot learn anything about trends and so on.
One sword however, is already enough for one major conclusion:

Around 50 AD, at least one smith in the
Roman empire knew everything needed
to make complex composite swords
Here he is. An authentic Roman smith with his helpers, as shown in an amazing picture from a house in Pompeii
and thus dating to - roughly - 50 AD.

Iron, Steel and Swords script - Page 482

Roman smith
Source: Photographed in the Archeological Museum Naples, 2018

This is a picture from Pompeii, showing a smith at work. Pompeii went down the drain (so to speak) at 79 AD, so
the time is about right. The picture (besides being a masterpiece of composition etc.) shows the main ingredientsneeded to make complex composite sword: knowledgable assistants (nowadays known as grad students). I'm notsure why they need to be naked.
We also know from looking at the production of Roman iron that this was a highly organized activity. The quality was notmuch better that that of the non-Romans, but the quantity increased substantially, and everything was standardized.
Look at those iron bars found in the Rhone ship wrecks to get an idea. We might assume that the military industrial
complex that made all the weaponry and so on, was just as organized. It is quite possible that standard equipment
including swords was not made at a top quality level but only up to meeting specifications (including costs, maybe).
However, without a sufficient number of specimens, this is just speculation.
All things considered, the Romans did quite well with their swords for several centuries. The Barbarians overthrowing theRoman empire eventually did just as well or better. Their swords were straight and double edged and thus related to thespatha. And they were pattern-welded and at least earlier in the first half of the second millennium acquired in one way
or another from Roman sources. This leads us almost straight to our next topic, pattern welding.
Before I go into this, however, we need to give a quick glance to more "Roman swords:
Swords of the Byzantine Empire
In the West we always learn that the Roman Empire collapsed on at 476 AD. This is not quite correct, however: it was
only the Western part of the Roman empire that came down for good. The Eastern part survived for almost 1000 years,
until 1453 and became known as Byzantine Empire. It not only survived, it was the most powerful economic, cultural,and military force in Europe during most of its time.
Constantine I (324–337), who reorganized the full empire, made Constantinople (=Byzanz=Istanbul) the new capitalof the empire and legalized Christianity. Sultan Mehmed the Conqueror finally took the city (and the empire), after a
53-day siege that had begun on 6 April 1453. Constantinople's "invincible" walls were breached by the early (first?)
use of cannons.
So what did the Byzantine empire give us in terms of iron and steel technology?
Nothing, it appears. At least I could not find anything written or shown in museums. I did not search very hard,though, but I doubt there is much to discover. I have found nothing at all in the museums in Istanbul. The Byzantines
probably just carried on what they had and did not add anything worth to note.
That goes with their achievements in almost all other "disciplines" you care to mention: Philosophy, literature,music, art, ship building, general technology, whatever - except, perhaps, architecture. The built the Hagia Sophia, after all, around 535, and this building is still a site to behold. They also were fanatic about mosaics but that getsrather boring long before thousand years have passed.

1)

First law of engineering: If it ain't broken, don't fix it.

2)

Janet Lang: "Study of the Metallography of some Roman Swords", Britannia, Vol. 19 (1988) pp 199 - 216

3)

Michael Fulforda, David Sim, Alistair Doig, Jon Painter: "In defence of Rome: a metallographic investigation of Roman
ferrous armour from Northern Britain", Journal of Archaeological Science, Volume 32 (2005) pp 241 – 250.
Iron, Steel and Swords script - Page 483

11.3 Pattern Welding

11.3.1 Background to Pattern Welding
What is Pattern Welding?
Pattern welding is a special way of constructing a sword blade from a lot of iron / steel parts. Many different kinds of iron/ steel parts are fire welded in such a way that a pleasing pattern can be observed on one or both sides of a blade. The
pattern results because two sufficiently different kinds of iron / steel that intersect the surface reflect the light differently,
in particular after some special polishing or etching.
You thus must use very special shapes of the parts to be welded to produce a specific pattern, and you must use quite
different kinds of iron and steel to render the pattern visible. In other words: You must do structural and compositional
piling, and you must do it in a way that produces the pattern you are after.
It is time now to look a bit closer at a few words that relate to the ways of making a sword. The first thing to note is thatthese words and their definitions had not been engraved by the finger of some God in tablets of stone or metal. They
have not been handed down as unalterable eternal truth as claimed for some other stuff. There is, for example, no uniqueand undisputable definition of what "damask" or "damascening" means. It has meant different things to different people
at different times. Come to think of it, even in the rare cases where writings in tablets of stone came down from high up,
different people at different times interpreted these words differently. They even developed a strong tendency to killeverybody not agreeing with their interpretation even so one of those writings reads rather unambiguously "Thou shalt
not kill".
What follows are therefore my personal definitions. I keep as closely as possible to the direct meaning of words, toestablished meanings in Materials Science, and to customary uses in the iron, steel and swords community. All ofthese terms I have used and defined before. Here goes:
Pattern welding: Fire welding different kinds of iron / steel in such a way that a specific pattern occurs on thefinished (and possibly etched) blade.
Banging together (by fire welding) random pieces of iron / steel in a more or less random way will also produce apattern on the finished blade. That pattern, however, is random and not intended. The resulting sword is not apattern welded sword but a sword made by piling.
Patterns will result if sufficiently different steels have been used and appear at the surface of the sword. Sufficiently
different" in this context means that light is reflected differently, especially after some etching. It doesn't matter if thesteels are mechanically or otherwise different; all that matters is that they are optically different. It is also importantthat both steels show at the surface. If one kind is completely enclosed by the other kind, for example in Japaneseblades, you cannot possibly see it and there can be no pattern. I use the term "piling" for that.
However, there are some (vague) reports that visible patterns can also result if identical or similar pieces of steel
were badly welded. In this case large slag inclusions along the weld seams provide for the visible pattern. I have yet
to see such a blade and will ignore them in what follows.
Pattern welded swords belong to the group of composite swords.
Pattern welded swords are often associated with the term "damascene", causing a lot of confusion.
Piling: I have defined piling before, the link gets you there. Most generally it meansthat a big piece of iron / steel is made by fire welding smaller pieces. Piling can bedone completely random or in very complex ways. Composite swords and patternwelded swords are always made by highly complex piling. Moreover, a smith could
do complex piling in smart or stupid ways. Welding soft iron for the cutting edgesto-be to a hard core appears to be a rather stupid way of non-random piling, forexample.
Any pattern welded sword is a sword made by compositional and structural piling.
But not every sword made by compositional and structural piling is a patternwelded sword; take a Japanese sword as example.
Damascene technology. This term has been used and still is used for aconsiderable number of completely different things, most of which have nothing to
do with the city of Damascus. More, the term was more than once introduced
because of a misunderstanding or mistake. I try to avoid it as much as possible
here.
The special module gives all the details.

SpecialModuleDamascene
Meanings

Damascene swords. There is no such thing as a damascene sword, i.e. a peculiar type of sword that originatedfrom the city of Damascus. A lot of people, however, do not know this and assume that a damascene sword is aextremely good sword that shows some pattern. The property of being very good is somehow associated withexhibiting a pattern. That leaves four possibilities
1. The sword is a pattern welded sword. Indeed, these swords are often called "damascened", in particular inGermany, for unclear but faulty reasons.
2.
Iron, Steel and Swords script - Page 484

1.
2. The sword has been forged from a suitable crucible steel in such a way that a "watered silk" pattern appars
on the blade. No piling and thus no pattern welding of any kind is involved. These "wootz" blades, as I like tocall them, are sometimes called "true damascene", again for no good reason.
3. The sword was made by compositional piling but with no intention to produce a pattern. Many swords all over
the world were made this way and none of them has anything to do with "damascening".
4. The sword has no intrinsic pattern whatsoever but somebody "painted", scratched, etched, or encrusted
some pattern on the surface. Either to make it more beautiful or to fake a "damascus" pattern. Those fakes
are sometimes called "false damascene".
So simply stop using any variant of the word "damascene" and you will do yourself and everybody else a big favor. I
will avoid this term as far as possible.
Pattern welded swords are primarily objects of art. Pattern welding in its prime was never done because that techniquemakes for better swords. It was done because it makes for more beautiful swords.
There is only one problem with that statement:

Nobody today has ever seen an oldpattern welded sword in its full glory.
Old pattern welded swords are at least 1000 years old. They were en vogue around 200 AD - 800 AD in Northern
Europe, after 800 AD they slowly disappeared. Of course, pattern welding did not spring up with all its complexities
over night. There was a continuous development from piling to complex pattern welding and early on some attempts
at (simple) structural and compositional piling did produce better swords and (simple) patterns on the side. But
going beyond that will only make your sword prettier, not better. I'll get to this in more detail later.
What is left of pattern welded swords typically looks like this:Pattern welded swords from the Nydam treasure
Source: Photographed at Schleswig-Holstein Landesmuseum,
Schleswig, Germany

These swords belong to the "Nydam treasure", all kinds of things unearthed froma Danish bog. In fact, Danish bogs yielded a lot of swords (more than 400) fromaround 100 AD - 500 AD, most of them Roman, and most of them pattern welded.
That's why there are a lot of modules around those finds.
Discussing pattern welded swords means to look at a period of about 800 years in(Northern) Europe, give or take a a few centuries here and there. But all we haveare the swords found in Danish bogs and a a few hundred, maybe close to athousand, found in odd places or in graves all over the place but mostly in certain
areas like South Germany. In other words: our knowledge from archaeological finds
Iron, Steel and Swords script - Page 485

SpecialModuleBog
Sacrifices

is rather patchy, in time as well as in space.
Not all that long ago almost nobody knew what a pattern welded sword in its prime looked like. However, in the last 20
years or so enterprising smiths have started to duplicate old blades. Foremost in Germany (and probably the world atlarge) was Manfred Sachse, whose replica of the "sword from Ingersheim" from 1992 in the Stuttgart museum moreor less started me on this enterprise. Meanwhile quite a number of smiths make pattern welded swords. Patrick Barta,
for example, specializes in making rather close replicas of some old swords, including making his own iron / steel in abloomery.
Here are some of the patterns he realized:

Patterns in pattern-welded swords
Source: From the Internet pages of Patrick Barta; http://www.templ.net ;with friendly permission.

It is impossible to convey the magnificence of pattern welded swords in small pictures. This link leads to to somelarge-format pictures showing some replica swords from Patrick Barta. If you do not have the desire to own such asword, you are a lost cause.
Now to business. If you look long and hard at the picture above, you should realize that any ancient smith who
attempted to make blades with patterns like these must have been able to do two things on top of what his older
colleagues could do, who already could make very good swords by compositional piling. And I don't mean hardening by
quenching; that was well-known before pattern welding came into its own.
You see it? No? Fine, I will tell you:
1. The pattern is only visible if the two materials used are quite different. You
may use low carbon and high carbon steel, or wrought iron and phosphorus
iron, whatever. What you cannot do is to weld wrought iron to wrought iron or
medium steel to medium steel, something the Celtic and Roman sword
smiths did quite often as we have seen. There might be a pattern but you
won't see it.
That means that you, the smith, must be able to recognize and select two
specific kinds of iron / steel from what's out there, and your error marginmust be small.
2. The pattern is only uniform if your two steels are uniform. In other words, thecarbon (or phosphorous) concentration in one kind must not change going
down the blade as it is usually found with the older Celtic or Roman swords.
That requires a kind of uniformity that is far better than what you typicallyhave in the pieces you selected. The uniformity needed can only beachieved by substantial folding and rewelding the selected pieces. In otherIron, Steel and Swords script - Page 486

SpecialModuleFaggotingwords: you need to do heavy faggoting. More to that topic in the special
module.
There are undoubtedly many pattern welded swords out there where the material was not faggoted. They still may
have sported a nice pattern because the smith was lucky. There must also have been pattern welded swords withnot so good patterns, washed out here and there, and with ill-defined contours. We do not know because extremely
few old pattern welded swords have been repolished, so we simply do not know what their pattern looked like. For
more or less the same reason we also do not know if the steel used for making pattern welded swords was faggoted
or not, see below. We also should not extrapolate from the swords we have to the bulk of swords used a long timeago. What we have tends to be the top-of-the-line products, sacrificed because taken from the Chief or entombedwith the Boss. The normal every-day stuff was re-used or re-cycled and just disappeared.
At least one of the Celtic blades (No 12) investigated by Pleiner had essentially a very complex pattern welded
structure, quite different from all the other ones. If there isn't a mistake with the dating of that sword, and I don't suggestthat there is, we must conclude that all the techniques and skills needed for advanced pattern welding existed several
100 years before pattern welding became mainstream. Why didn't it catch on? Maybe because the uniformity of thewelded bars was no good enough to produce a clear pattern all the way? Maybe faggoting was not invented yet?
This is just idle speculation. We just don't know for sure what these ancient smiths could do with respect tofaggoting. Why? As pointed out before, you cannot judge the uniformity of a long bar of steel by just looking at a
cross-section. You need to look at it lengthwise, and that is almost never done because it would "destroy" the whole
length of the blade. Whenever it was done with less precious stuff (double pyramid bars, roman iron bars), the stuff
was always non-uniform with respect to the carbon and phosphorous concentration. Since the pattern in a patternwelded sword is created by a defined difference in the two kinds of steel, typically the phosphorous concentration,
fluctuations of the phosphorous concentration would produce fluctuations of the color difference and therefore patchy
pattern with washed out parts. Modern smiths do not have that problem. The darkness and brightness of the twokinds of steel is the same everywhere.
The point I'm trying to make here is that the general switch to making pattern welded swords around the 2nd century
AD implies that the long bars welded together must have been reasonably uniform. It just makes no sense to dopattern welding with doubtful materials. Since the blooms and all the semi-products made from blooms were notuniform at all, the smith must have used faggoting in one way or the other to achieve uniformity.
We can be fairly certain about that - and we have a few direct observations. Recently Stefan Maeder subjected
some old Western swords (Including a pattern welded one) to the Japanese kind of polishing, and that does makefaggoting visible up to a point. More to that in the link. Closely looking at Danish bog swords (not easy because themuseums mostly keep them in the basement, in the dark, or far behind reflecting glass), one can see clear
indications of faggoting; here is an example.
If we mull this over a bit, a major conclusion will emerge:

The end is near.
A smith who could make a pattern welded sword like the ones shown here around 300 AD - 600 AD has reachedthe zenith of working with bloomery iron / steel. There is nothing left to improve upon. Such a guy could makeanything that can be made with iron / steel by hand forging. If you supply him with better iron / steel, he might makea better sword but not because he uses better forging techniques. There are no better ones.
Does that mean that we are close to the last page of the Hyperscript? Not really. I still have to tell you how a patternwelded sword is made, and I will also look into the making of "Japanese" swords and wootz swords. In addition, I will
give you some stuff about the properties of sword and the mechanics of wielding a sword.
Basic Ways of Pattern Welding
If you want to know almost all there is to know about pattern welding, read the book of Manfred Sachse! It is amarvellous book with lots of high-quality pictures - and there is no way that I can improve on it. So I will give you just a
short and very general introduction into what pattern welding is all about in this module. I'm going to look into some moredetails in the next module.
Quite generally pattern welding employs butt welding. At least 4 rods are needed, and more than 10 have been
employed. Two rods are almost always made from uniform hard steel and are used for the edges of the blade. The
rods that will produce the pattern are made from two different steels. A kind of standard often encountered was apackage of seven layers; 4 made from "soft" steel, 3 made from "hard" steel. That is the way it is usually described
but I put soft and hard in quotation marks because the hardness is not what counts. The effect you are after is abright -dark contrast in the finished blade and not a hardness difference. The best way to achieve that is to use use
phosphorous-rich and phosphorous-free iron, and that seems to be the most common approach for making what I
will call a "striped rod". Iron containing sufficient phosphorous has a bright whitish appearance, phosphorous-freeiron or steel is dark. In what follows I will therefore use the neutral terms "bright" and "dark" iron / steel.

Iron, Steel and Swords script - Page 487

What's more: coupling phosphorous-free carbon-lean and carbon-rich steel is not such a good idea. During all thehigh-temperature smithing required for fire welding, the carbon concentration will more or less equalize by diffusion.
There cannot be a well defined color change at the boundaries any more. In contrast, since phosphorous diffusesmuch more slowly than carbon, the difference in phosphorous concentration is not washed out.
Let's start by making a rather simple pattern welded blade with just three patterned striped rods (two would be theminimum; eight are about the maximum).
What you, the ancient smith, needed to do for a simple pattern welded sword was:

1. Get enough raw material with the following specifications:
1. Bright steel. Phosphorus-rich wrought iron might be best
2. Dark steel. Maybe phosphorous-free medium steel - whatever will provide for a good contrast to your brightsteel.
3. Hard steel. Needed for the edge. Your steel should have at least the eutectoid composition (0.7 % carbon).
Take the highest carbon concentration you can still work with since you will loose some carbon duringforging.

2. Faggot all three materials before you form bars. In other words: hammer into a sheet, fold and weld, hammer into asheet, ..... Repeat 8, 9, 10 , ...times. Make sure that the welds are perfect and that you do not introduce too much"dirt" like oxide, slag or flux inclusions by the welding. In the end make two rods from the hard steel, about as longas the blade to be, and 12 or 9 plates from the bright and dark steel, respectively, about 4 cm x 7 cm wide / longand 7 mm thick.

3. Make three packages from 4 bright and 3 dark steel plates each as shown:

Package, striped rod, and twist

4. Fire weld each package and than draw it out to a rod about as long as the blade to be - as shown above. The crosssection of the rods should be about 1 cm × 1 cm. What you have now is what I like to call a "striped rod". It is thestarting material for many - but not all - pattern welded swords.

5. Twist the striped rods evenly or, for a more complex pattern, alternate twisted and non-twisted regions, making surethat the alignment of the layers in the non-twisted regions is the same everywhere (striped sides always "up", forexample). You many also change the twist directions (clockwise / counterclockwise). Now you have a twisted
striped rod

6. Put all rods next to each other as shown below (for just two twisted striped rods). In the non-twisted regions thelayers should be perpendicular to the picture plane so that a stripe pattern can emerge.
You may grind down the rods somewhat, especially flattening the sides to be joined. You may also want to fit thetwisted parts exactly so they interlock like two screws with the same thread. That necessitates, of course, that thepitch of the twist is exactly the same in the two rods, something next to impossible. The two hard steel rods go on
the outside. You may want to bend these rods a bit as shown below in order to obtain a snug fit at the end where
the point will be.

Iron, Steel and Swords script - Page 488

Arranging the rods to be welded, and welding
Source: From the Internet pages of Patrick Barta; http://www.templ.net ;with friendly permission.

7. Fire weld the assembly, making sure that the weld seams are perfect. Forge it into the basic sword shape desired.
If necessary, supply a tang by fire welding. Alternatively, extend some of the rods into the tang.
That gives the raw blade as shown above (together with some parts for the hilt)

8. Make fullers by forging if so desired. Grind the blade, giving it the cross-section desired. Note that the pattern you
will get depends on how deeply you grind into the twisted rods.

9. Quench-harden the edges. Before you do that, cover the body with some protective mud (for what is called"differential hardening"), making the cooling rate much larger in the edge part than in the body of the blade. And
yes, that is the famous way of making Japanese swords with particularly hard edges. And yes again, our ancestors
may have done it too, even so this has not been advertised a lot so far.
Now temper a bit (annealing at low temperatures) after quenching. Alternatively, keep the quenching time so shortthat "self-tempering" occurs since the inside is still hot and heats up the outside again after pulling the blade out of
the cold quenching liquid. Do some "slag-quenching", in other words.

10. Finish by polishing the blade and exposing the pattern by one way or the other, e.g. by some etching. Allow a lot oftime for doing that.
Add a nice hilt, matched to the beauty and value of the blade.
Have a beer or two.
You have now made a simple pattern welded blade. Of course, now you wonder what the resulting "torsion damast"pattern will look like? I yet have to meet somebody who can imagine what the distribution of bright and dark iron looks
like in different depths of a twisted striped rod. You are welcome to figure that out by yourself - but here are the pictures:

Patterns disclosed by successively grinding down thelength of a twisted clay model striped rod
Source: Lee A. Jones: "The Serpent in the Sword: Pattern-welding in
Early Medieval Swords" 1997; Internet article

The pictures above and below are from an Internet article of Lee A. Jones. The article still makes for good reading;here it is.
The clay model rod in the picture contained sixteen alternating layers of white or black clay (and not just seven as
in the text); it was prepared by bladesmith Dan Maragni. Note that in making and twisting a striped rod you will not
be able to keep the layers exactly parallel everywhere. Some distortion is unavoidable, an example of one real
cross-section is shown in the upper left-hand corner.
The striped rod was progressively ground and reduced in overall thickness by the percentages shown in the picture.
The pattern at each each interval was photographed. so these are real patterns. Further leveling of the striped rod
will produce mirror images of the patterns shown
The next picture shows the effect of the numbers of layers used.

Iron, Steel and Swords script - Page 489

Pattern variations shown in clay models with 16, 8,
and 2 layers
Source: Lee A. Jones: "The Serpent in the Sword: Pattern-welding in
Early Medieval Swords" 1997; Internet article

Once more we have photographs of a clay model striped rod. The two-layer rod shows the pattern after justflattening it with a hammer. No grinding is needed in this case.
Let's take another look at the structure but now with "theory". What we see below are computed drawings of an ideal
structure with perfectly parallel layers. The cross-section is indicated on the top of the striped rods.

Ideal pattern variation with depth in a twisted rod
Source: J. Ypey: " Europäische Waffen mit Damaszierung.
Archäologisches Korrespondenzblatt 12 (1982) ppp 381 - 388.

The picture also indicates how one can get an uninterrupted wavy line by proper alignment of perfectly matchedrods ("effect" side). This is considerably more involved than just a random alignment, of course.
What we have made might look like this:Simple pattern welded swords with three twisted
striped rods (left)
and two twisted and one untwisted striped rod (right)
Cross-sections do not relate to the swords shown

Iron, Steel and Swords script - Page 490

Source photographs: From the Internet pages of Patrick Barta; http://
www.templ.net; with friendly permission.

Note that the front and back will look about the same. What you get depends on how deep you grind and that
depends to some extent on the cross-sectional shape chosen as schematically indicated. How deep you can grind
is limited by the thickness of the blade. If you want a thickness of 5 mm in the center, you can only grind off 2.5mm on each side of a 10 mm rod, of course.
In other words: you cannot get the more circular or "flowery" patterns deeper down in the rod.
Now that you have made a relatively simple pattern welded sword, you want to try your hand at a more complicated one.
You want to have full freedom for the patterns, different patterns on the two sides of the blade, and a very fine pattern.
Then we talk about cross-sections like this one:

Complex pattern welded blade
You make eight striped rods with 16 layers each. You grind down as deep as you want to get the desired pattern on
one side (with the final grinding after the blade was forged). You also grind down the backside so you can fire weld
these thin rods to an additional core; 4 on the front side, 4 on the back side. You need 64 each of faggoted brightand dark iron plates to start with, plus the centerpiece and the hard steel for the edges.
What you get is essentially a sword made by piling with a thin veneer that produces the pattern. It is clear that the"veneer" could not be all that important for the sword properties; it was essentially just for show. It also concealed
all the flaws from imperfect welding, large slag inclusions and so on that might have been visible on the "naked"
blade. Here is an example of what a good "naked blade" might have looked like. Putting on some veneer was adefinite improvement in looks.
What the real thing might look like is shown below. It is a blade fragment from the Nydam treasure. it is badly corroded
and most of the edge part is missing. Nevertheless, it is quite clear that the structure is similar to what is shown above.
We have three striped rod on both sides. On one side the rods ware twisted and ground down to reveal a pattern akin tothe ones shown above. On the other side the rods were untwisted and thus display a stripe pattern.

Fragment of a Nydam sword with complex pattern
welding
Large picture"Only" three and not four (partially) twisted layers on one side. But front and backside are now different so we have
six twisted layers altogether
Making a sword like this gets to be real work! And extremely skilled work because one mistake, just one wrong bangwith the hammer or being a fraction of a millimeter off during grinding, and your blade is ruined.
A whole sword might look like the Spatha of Ingersheim:

Iron, Steel and Swords script - Page 491

Ingersheim Spatha 1)
Source Used with permission

A lot of different patterns can be produced by (twisted) striped rods; even more than what I have shown here.
However, some patterns found in ancient swords need even more involved work; I'll get to that.
If you look at the cross-section above and give it some thought, you realize that in essence you have a sword made fromsolid steel with a thin "veneer" of patterned stuff on both sides. It is clear that the "veneer" part cannot be of much
importance to the properties of the sword. This makes very clear that at least at this stage the pattern welded part isonly decoration with no function whatsoever for the fighting value of the blade. Its function was in pleasing its owner
either by its beauty or because he could afford it, and in sending signals to others about the significance of its owner. In
other words: it was a fashion statement.
Just give the Stuttgart Psalter a quick look to convince yourself that these sword bearers were fashion conscious:

Fashion around 825 AD
Source: Internet site of Württembergische Landesbibliothek, Stuttgart,
Germany
Iron, Steel and Swords script - Page 492

If you look at the general outfits of those old sword bearers you realize that they were far more into fashion than atypical physicist of our time. They were into fancy, fashionable stuff, about on par with present-day catholic priests
or rock stars.
It was important to be fashionable and to show your importance by sporting the proper sword (and scabbard), even if you
couldn't quite afford it. That's perhaps, why some pattern welded swords had patterns only on one side. The last "goldhilt spatha" found around 1970 in Pleidelsheim 1), South Germany, (increasing the number of known South-German
gold-hilt spathas to 18) had gold only on the show side of the sword, like some others. This show-off pattern weldedsword belonged to an Alemanni who lived around 550 AD next to my home town. If some no-nonsense fighting was
required he probably used the plain sax that was also buried with him.
If you assume that the general attitude towards fashion was not all that different from that of today, you know that thetime of the pattern welded sword would be over some time after it had reached its summit. When you can't put morelace around, or tatoos on your neck, because there is simply no more room, you switch to something different sooner orlater. Fashion changes might not have been as frequent as today in those more slowly moving times, but changes would
occur for sure.
It was thus to be expected that the complex "veneered" pattern welded sword would eventually loose ground to a radical
new fashion like the "Ulfberht sword".
Before I look at the "Ulfberht swords", I will give you a bit more about pattern welded swords and the (patternwelded?) sax that was used in parallel to the pattern welded spatha as we call all double-edged straight and longswords.

1)

Ingersheim in Ludwigsburg county is a small town at the left-hand side of the river Neckar in South Germany. It actuallycomes in two parts: Groß-Ingersheim and Klein-Ingersheim. It's one town down-river from the town were I was raised. In
1969 and later in 1988/90 around 250 "Frankish - Alemanni" graves that contained pattern welded swords among manyother things were mostly found in Pleidelsheim (other side of the Neckar). Ingersheim is also a quarter in not-so-far
away Crailsheim.
The Alemanni were a confederation of Suebian Germanic tribes on the upper Rhine river. First mentioned by the
Romans in 213 AD, the Alemanni expanded into present-day Alsace, and northern Switzerland, leading to theestablishment of the Old High German language in those regions. In 496 AD., the Alemanni were conquered by Frankish
leader Clovis and incorporated into his dominions. The legacy of the Alemanni survives in the names of Germany inseveral languages; they are more or less my direct forebears.
Stefan Maeder mentions the sword of Ingersheim at least twice. For reasons of his own he refers to it as the sword from
Ingersheim / Crailsheim county or Ingersheim / Schwäbisch-Hall county. I do not know where it really comes from but myguess would be Pleidelsheim.

Iron, Steel and Swords script - Page 493

11.3.2 More to Pattern Welding
Points to be Addressed
There is a lot more to pattern welding than what I gave you in the preceding module. There is so much in fact that I'm notsure of where to start. Making a list always helps, so here goes:
1. How to make complex patterns not possible with twisted striped rods, e.g. the blade at the bottom of thispicture?
2. Was anything else made by pattern welding? How about sax blades and lance heads, for example?
3. Were pattern welding techniques used outside of Northern Europe? When? What for and how?
4. How do pattern welded swords fit in with Celtic, Roman and Viking swords, and so on?
5. What about quench hardening of pattern welded blades? Was it done at all and if yes, was it really similar to thefamous procedure used for Japanese swords?
6. How does pattern welding relate to Damascus? Are "damascened" blades better than others?
7. What about the revival of pattern welding in the 19th century?
8. How to treat the surface to reveal the pattern. Is "Japanese polishing" better than "normal" polishing followed bysome etching?
9. The history of the making of pattern welded swords. Who made the first ones when and where? How did thetechnology develop and spread?
10. The history of the discovery of the pattern welded swords. How many have been dug out when and where. Where
are they now? What kind of investigations took place? Why are the Danes so pissed about the Nydam treasurein Schleswig?
11. The metallurgy of the pattern welded sword. What do we know and what doe we guess?
That's a long list and it is probably not even complete. Some questions have short answers, some merit own chapters.
And they all are interconnected. Some of these questions cannot be answered without referring to other ones.
Here I will deal quite shortly with these questions; details can be found in plenty of additional modules
To say it once more: If you want to know a lot about some of these topics, do what I said before:

Read Manfred Sachse's book!
You will find answers to many but not all of the questions above.
Now let's start.
Complex Patterns: The Serpent in the Sword
Piling (partially) twisted striped rods can make a wealth of pleasing patterns; just lookat all the examples given. There are, however, a few old pattern welded swords that did
have rather unusual patterns that could be made with striped rods but not with straightrods. An extra process was needed for swords exhibiting a so-called "serpent in thesword" pattern, i.e. undulating lines running down the center of the blade. I havealready shown an example; there are more in this link.
There is some speculation that these undulating lines symbolize something like
serpents, symbols imbued with mystical powers. That's why the "Serpent" swords havetheir own module.
Maybe other patterns have some symbolic meaning, too? We don't know.
How does one make a serpent? If you have no better idea, this would work:

Iron, Steel and Swords script - Page 494

SpecialModuleSerpent
swordsMaking a serpent in the sword. One side has been
ground to be flat.
Produce a regular striped bar. Weld two other bars of whatever you like left and right. Forge into an undulating
shape. Flatten the sides by grinding. You obtain one bar with a "serpent". Use it for making your sword.
This looks like tricky and time consuming work. I wonder if there is an easier way. All those modern smith who canmake "serpents", for example Patrick Barta, would know. Ask them.
Complex Patterns: Wood Grain and Mosaic
There is more that one can do with striped rods. Here is the next example:
Make the stripe rod a bit bumpy or wavy. Cut through it at more shallow angles. Look at wood and you know what
you can get. The following picture gives an example:

Woodgrain
Now make your striped rod bumpy in a defined way. Make little hills or bumps (bang it from behind with a ball-shaped
hammer, arranging the bumps in a kind of grid) until the surface looks kind of like an egg carton. Then grind it flat
again. What you will get are more or less well-defined systems of rings on one side:

How to make mosaic patterns
A wood grain example in the lower left corner.

Mosaic patterns - old and newIron, Steel and Swords script - Page 495

Source: Left: Illerup Ådal; Vol. 11, 12
Right: From the Internet pages of Patrick Barta; http://www.templ.net;
with friendly permission.

The "Illerup" sword shown is rather unique. It belongs to what I have termed "Illerup swords with special patterns"
and there are several special modules that go with that:SpecialModuleSpecialModuleIllustr.
ModuleScienceModuleBog
Sacrifices

Illerup
Adal

SpecialPatterns

Sword
Types

The "Link Hub" for Danish The place where manybog finds, the places where swords with special
many pattern welded
patterns have been found,swords were foundoften extremely wellpreserved

Details about some swords The scientific classificationfrom Illerup with specialof 12 sword types for thepatterns
first 5 centuries AD.

Now let's look at pattern that cannot be made with striped rods.

Complex Patterns: Palmette and Chevron
Let's look at question No. 1: How to make complex patterns?
Some swords found in the Danish "bog treasures" and in other places showed what is often called a chevron pattern,a palmette pattern, and combinations of the two. There are many examples in the "Illerup Swords with Special
Patterns" module. But we also find them in the probably very first publication that addresses pattern welded swords:
Conrad Engelhadt's books about the Nydam finds.
Here is what I mean:

Chevron pattern
Top: Engelhard's picture of the sword part
Middle: Photograph of sword detail
Bottom: Photograph of what's left
Source: Engelhardt's book and 2)

Iron, Steel and Swords script - Page 496

Palmette patternLeft: Engelhard's picture of the sword part
Right: Photograph of actual sword
Source: Engelhardt's book and 2)

The two swords are presently in the Copenhagen museum but apparently not on display. They are listed as No. 388 and
498 in 2) and carry the stock No. 25 234 and 25 249, respectively. They are probably from around 350 AD. The hilt of the"palmette" sword, however is in Schleswig:

Right: Photograph of actual hilt
Left: Engelhard's picture of the hilt
Source: Photographed in Schleswig; Engelhardt's book

There are more swords found in Danish bogs with chevron and palmette patterns; especially from Illerup Ådal. Not a lot
but enough to ascertain hat these patterns were routinely made. This link shows details. Chevron and palmette patterns
are quite interesting for a simple reason: How does one make patterns like these? And combinations thereof?
Sometimes the chevrons are "filled" with palmettes; sometimes with something else - at last this is claimed in theliterature. One example is shown here.
How does one make pattern welded swords with chevron or palmette pattern? Good
question. Looking at just the palmette pattern, one way would be to first making
rods with a palmette cross-sectional pattern. Then cut your rod them into thinslices, which you weld on the blade, little piece by little piece.
This leaves the question of how you make a rod with a palmette cross-sectional
pattern? I simply don't know. I could guess but so can you; keep in mind that theseguys also knew how to make wires that could be used for making finer structures.
But even if you have a "palmette" rod, how do you cut it in thin slices? Precision
metal saws did no yet exist.
More to that in the Illustrations module. Here we simply note:

Illustration
ModulePatterns

Nobody seems to know how
chevron / palmette patterns were made!
Several authors deal with the problem by not mentioning it (e.g. the Illerup Ådal (Vol. 11, 12) books or J. Ypey's article1)). I do have some ideas, though.
Iron, Steel and Swords script - Page 497

Now let's consider that I have answered - to the best of my ability - the first question: how to make complex patterns. It'stime to look a the other questions
Quickies
What I'm going to do now is to run very briefly through some of the other questions from above. Here goes:

Question No. 2: Was anything else made by pattern welding? How about sax blades and lance heads, forexample?

Answer: Yes.
However, typically far less often, and mostly (but not always) less elaborate, as far as I can tell. If one looks at all
the graves were some important person was buried with a sword and a sax, chances are that the sword was patternwelded and the sax was not.
A few lance heads out of thousands were decorated with patterns, sometimes elaborate.

Question No. 3:: Were pattern welding techniques used outside of Northern Europe? When? What for and how?
Answer: Yes. Most of the time, mostly for show, and more or less as described above.
Seriously now: Whoever worked with iron and steel at any time after, say, 1200 BC had to make a sword oranything else not too small by some kind of piling - except for the people using crucible steel. At the very least you
had to "pile" your bloom. It is unavoidable that on occasion a random pattern results, and it is equally unavoidable
that somebody somewhere sometime started to develop piling to a point where the pattern is no longer random but
intended. In particular if Mr. somebody had seen a true pattern welded sword that somebody else had brought backas a souvenir from his business trip to Northern Europe. In contrast, some others like the Japanese might have gone
for rather tricky structural and compositional piling but without the intention to produce a pattern.
Be that as it may, it is now time to clear up a few statements about he iron / steel technology of "The Others" thatcome up all the time and rather confuses the issue.
1. Nobody on this globe could make a sword that comes close in complexity to the pattern welded swords of
the Celts / Romans after about 200 AD or even much earlier.
2. Statements like: "For Japanese Samurai blades several thousands of layers were welded together, fororiental damascene (meaning wootz) we have a few hundred, and the Indonesian Palmor has a few dozen. In
Europe, however, one rarely exceeds ten layers" 1) (my translations) are pure BS. The statement not only
confuses faggoting with piling, it also assumes that the quality improves with the number of "layers". We
know that some North European sword smiths used faggoting because of Maeders's fine analysis, and we
can assume with confidence that it was done most of the time as pointed out before. They had "thousands oflayers" too, in other words.
3. But what about the Chinese? Well - read this module. I do not doubt that "the Chinese" made fine swords
around 200 AD, too, but I challenge you to prove that they made one that was more complex or simply better
than some of the finest Nydam / Illerup swords.
This is about iron and steel technology. So far I have not found a convincing reason that other areas on this globe
were ahead of the Europeans as far as working with bloomery iron and steel was concerned.

Question No. 4: How do pattern welded swords fit in with Celtic, Roman and Viking swords, and so on?
Answer: It should be clear by now that the prime examples of pattern welded swords from the Danish bogs were from
Roman "factories". That doesn't exclude the possibility that the were actually done by Celtic smiths who in 200 AD had
become Romans.
The term "Viking" refers to people living in Scandinavia (including parts of what is now Germany) from about 800
onwards. Their swords are a kind of in-between the old pattern welded after-Roman sword and the new "Ulfberht" allsteel type sword. I'll get to that.

Question No. 5: What about quench hardening of pattern welded blades? Was it done at all and if yes, was itreally similar to the famous procedure used for Japanese swords?
Answer: Yes. And: maybe.
This is a bit tricky. A smith might have quench hardened a blade by dunking it in water without having hardening in
mind; maybe he just wanted to shorten the cooling down time. A smith might have conscientiously quenched his
blade to induce some case hardening but failed because he didn't do it right (too shortly, for example) or because
the steel he used for the edges was too low in carbon. Maybe he had phosphorus steel that can't be quench
hardened, or worse, a steel with both phosphorous and carbon (plus God knows what else) where all kinds of things
can happen during quenching.
Only quench hardening produces martensite in "normal " carbon steel. Metallographic analysis of pattern weldedswords did find martensite in some steel edges, so quench hardening was employed. And why not? We know thatthe earlier Celtic La Tène swords were not quench hardened while some early (not yet pattern welded but
laboriously piled) Roman swords were. However, in other samples martensite is absent - indicating either noquenching or failed quenching.
Was differential quenching used (that's the fancy name for what the Japanese did much later)? In other words, wasonly the cutting edge exposed to high cooling rates by protecting the bulk of the blade with some clay? There are
Iron, Steel and Swords script - Page 498some indication for this this - but it is too early to tell.
I'll come back to the topic later

Question No. 6: How does pattern welding relate to Damascus? Are "damascened" blades better than others?
Answer: The answer to the first question is clear; I have dealt with that already: pattern welding has nothingwhatsoever to do with Damascus.
The second question is a bit more tricky to answer. Yes, "damascened" blades are better than others because"damascened" or pattern welded blades had to be made with great cunning and care and thus were better thansome banged together discount swords. No , because you can't beat a sword made from piling good homogeneous
steels without producing patterns. Maybe because a composite of tightly interwoven rods of relatively bad steels
could be better than a simple structure made from these steels. More to that later.

Question No. 7: What about the revival of pattern welding in the 19th century?
Answer: A very tricky question with no easy answer. I will perhaps write a special module as soon as I see "thelight". Until then just a few points:
First let's look a the "facts" as far as I know them. Much of what follows is from Manfred Sachse's classic book.
Pattern welding went never out of style in the "Orient". In contrast to Europe it was used for all kinds of things
in Turkey and farther East, including armor, the Indonesian Kris, and in particular gun barrels.
When guns an pistols became private items for hunting (or duelling) in the 17th century, the "West" becameaware of the "Eastern" pattern welded gun barrels and started to import these items. That happened aroundthe end of the 18th century, i.e. 1680 or so. It is certainly connected to the general awareness of "the Turks".
First because one needed to throw them out of Europe (look up the 1683 "battle of Vienna", featuring thesuper-hero Prince Eugene of Savoy), and second because the Turkish culture and way of live made a big
impression on the Europeans; witness, for example, the collection of "Turkish" things by August the Strong,Elector of Saxony and later King of Poland (1670 – 1733), now on exhibition in the "Türckische Cammer"(Turkish Chamber) in Dresden.
However: military guns of all sizes in Europe were always made from one kind of (more or less) homogeneous
steel or cast iron (if not from bronze or brass) and never by pattern welding. Private pattern-welded guns
appeared around 1780; and some French, Belgian and English guys were instrumental in this.
At the beginning of the 19th century several European places made "Turkish damask", foremost Liège in
Belgium. It was a big industry and huge amounts of pattern welded gun barrels were made. An example of acatalogue is shown here; the real thing is right below.
As far as swords are concerned, piling and pattern welding went out of style after - roughly - 900 AD and wascompletely abandoned around 1200 AD in favor of all-steel swords. These swords were typically piled withsofter steel inside. They would not have shown a pattern. More or less in synchronously with pattern weldedgun barrels, pattern welded blades became fashionable again and a "damascened" sword was common in
the 19th century and the beginning of the 20th century in Europe.
The picture below illustrates what I'm talking about. It's a close up of a two-barreled gun with a torsion "damascene"
pattern. It's done by the usual production of a twisted striped rod plus grinding. Then the patterned long strip is
wrapped around a core, followed by fire welding. The final step is reaming the bore and straightning by experts.
Complicated but not really of much interest to us because (in Europe) it is a 19th century technology.

Iron, Steel and Swords script - Page 499

Pattern welded gun barrel and how it's done
Source: Photographed in the weapon museum in Suhl, Germany

The problem I have with all of this can be put into two question:
1. How does the revival of pattern welded "damascene", somehow triggered by "Turkish damascene" tie in withthe craze about wootz steel and blades around the same time? Note that any terms containing the word"damascene" in connection with patterned blades from the East could mean wootz blades or pattern weldedblades, and possibly also blades with encrusted designs.
2. How did the general ubiquity of contemporary "damascene" swords and things in the 19th century influence
the interpretation of the ancient pattern welded swords dug up systematically after about 1850? In otherwords: Did Conrad Engelhardt, when he dug up pattern welded Roman swords, recognize immediately that
he looked at "torsion" damascene and so on? He did mention "damascened swords" but it is not clear what,
exactly, he meant.
It is quite clear that there was some confusion - or better a lot of confusion - about patterns produced by using
crucible steel ("wootz") and by pattern welding. We also know of bitter fights concerning the difference in quality of"damascened" blades vs. single steel blades, including increasingly cast steel. Nevertheless, how all of thatconnects is not clear to me. Do no forget that as late as 1819 the science titan Faraday made completely wrong
pronouncements about the nature of (wootz) steel.
The second question is open. It will come up again when I deal with the history of discovering ancient pattern
welding.

Question No. 8: How to treat the surface to reveal the pattern. Is "Japanese polishing" better than "normal"
polishing followed by some etching?
Answer: Before I go into this, I advise you to look up this module.
OK, now that you are back, I can elaborate a bit about what that question implies. "Polishing", in the broadest
possible meaning, entails one or several of the following points:
1. Generating the basic geometry of the blade surface by "polishing" (or grinding) off surplus material. A flat
surface where this is wanted, a nice round fuller, or two, and so on. The surfaces should be reasonably"shiny".
2. The surfaces should be like mirrors, not showing any structure.
3. The surface should reflect the internal structure right after finishing polishing.
4. The surfaces should be good enough to allow some kind of chemical etching to produce a pattern. Either themacroscopic pattern intended by pattern welding or the microscopic pattern intended for structuralinvestigation with microscopy.
5. The polishing should keep lines and ridges perfectly straight and ridges sharp.
The last point needs explaining; best done with a figure showing a sword with fullers in cross-section:

Iron, Steel and Swords script - Page 500

5.

Top: Ridges / Edges perfectly straight and sharp after
polishing.
Bottom: Ridges / Edges rounded and somewhat wavy
The bottom one would look ugly and would be totally unacceptable, of course. However, the fighting value of the ugly
sword would be just as good as the one with the perfect structure. In other words:"Polishing" is mostly for show!
So what about the Japanese method of polishing a sword blade that, according to Stefan
Maeder, is so much better than what "we" did and do? In essence, Japanese polishing is acombination of point 3 and point 5 from the list above. It defines lines on the blade with theutmost precision and it reveals structures. The first part is not mysterious, it is just very
advanced precision work.
How does Japanese polishing reveal structures? And which structures exactly? Who knows;
I have yet to see a scientific investigation of "Japanese" surfaces. The principle is clear,
however. If the polishing particles in your slurry are harder then regular iron / steel, but softer
than martensite, for example, the surface structure on the iron / steel part will be different
from that on martensite, and that means you can "see" it.
Find out more by reading the special module

SpecialModulePolishing /Pattern

Enough! The last three questions left (No. 9 - 11) will be dealt with in the next module.

1)

J. Ypey: "Damaszierung"; in: Reallexikon der Germanischen Altertumskunde", Band 5, S. 191.

2)

Güde Bemmann and Jan Bemman: "Der Opferplatz von Nydam. Die Funde aus den älteren Grabungen. Nydam-I und
Nydam-II. Band 2: Katalog und Tafeln". Pictures photographed thanks to the library of Gottorf castle.

Iron, Steel and Swords script - Page 501

11.3.3 Evolution of Pattern Welding
We still have three questions to deal with
9. The history of the making of pattern welded swords. Who made the first ones when and where? How did thetechnology develop and spread?
10. The history of the discovery of the pattern welded swords. How many have been dug out when and where. Where
are they now? What kind of investigations took place? Why are the Danes so pissed about the Nydam treasurein Schleswig?
11. Most important: The metallurgy of the pattern welded sword. What do we know and what do we guess?
The last questions merits its own sub-chapter. I will deal with questions No. 9 and 10 right here.
History of Pattern Welding
I have put a lot of emphasize on the pattern welded swords found in Danish bogs. Almost all of them were from Roman
work shops that were supposedly located somewhere in South Germany / France or along the river Rhine. The"Romans" who made them might have been Romans in the same way as the guys who produced the atomic bomb or
rockets were Americans. The "Romans" in South Germany used to be members of Celtic tribes before they were
coerced to become Romans. Later (after 200 AD, say) they gradually turned into Alemanni (more or less forcefully)
before they became (very forcefully) Merovingians and then members of the Carolingian empire.
A number of bog-swords from around 300 AD where made with pattern welding skills that could not be improved uponthen or now - provided you work with bloomery iron / steel and a manually wielded hammer. So let's consider 300 AD as
the point in time when pattern welding technology climaxed.
Looking at the history of pattern welding we thus need to ask two questions:
1. What happened before 300 AD? How did pattern welding evolve?
2. What happened after 300 AD? How did pattern welding go on and eventually decayed?
Besides the history of pattern welding, there is also the history of discovering the pattern welding of old. It is one
thing to find an old pattern welded blade, and quite another thing to recognize it for what it is. The basic concept oftwisted striped rods is not so obvious if you (and everybody else you know) has never heard of that. I will give that
topic a quick look, too.
How Pattern Welding Evolved Before 300 AD
How did pattern welding evolve? Who knows. There are no written records and what has been dug out of bogs andgraves does not mirror the distribution of pattern welded swords 2000 years ago. There are far more Roman patternwelded swords in museums in Northern Europe than in Italy or Southern Europe because the barbarians up there
sacrificed a lot of swords in bogs where iron was preserved and they put swords into the graves of the warriors. The
Romans did neither. We need to go for educated guesses based on the few things we do know.
It is helpful to realize that here is a continuous transition from random structural piling to pattern welding of complex
patterns. Since all cultures working with bloomery iron had to do some piling for making products, it was unavoidablethat:
1. Structural and compositional piling developed, e.g. by using hard steel on the outside of a blade for the edges.
The Roman "Thames" sword from the 1st / 2nd century AD offers a good example for a thoughtful way ofstructural and compositional piling that did not produce a pattern. It was essentially made from one broad stripedrod.
2. Random patterns were produced on occasion and must have made people aware of the aesthetic potential ofcompositional piling.
Eventually striped rods became standard, producing not only a pleasing pattern but preventing sudden and complete
fracture, especially in cold weather, for all swords employing phosphorous steel for the harder parts. Many in-between
situations are imaginable and that means there is no definite beginning of pattern welding. The Celtic (La Tène) swords
bear witness to this. Some swords had their iron / steel parts piled in such a way that a pattern might have resulted,
possibly without the smith being aware of that. Contrariwise, another smith might have attempted to produce a certain
pattern and failed.
At least one Celtic smith making a "La Tène sword" around 300 BC (No. 12 in the picture accessed by this link)produced a complex pattern welded sword that looks suspiciously like one of the the more complex pattern weldedswords made about 600 years later. Far be it from me to doubt Pleiner's analysis of this sword. But this sword justdoesn't make sense. It is possible that a particular talented La Tène smith was 500 years ahead of the rest, it's just notvery likely.
Then again, in 2015 (after I had written this module), two Celtic swords (with anthropoid hilts) and pattern welded blades
turned up in an auction catalogue! The pattern resulted from simple striped rods that might have been employed forincreased fracture toughness but it sure looks like a pattern was clearly intended. Here is a detailed picture of one blade
and here are the descriptions from the auction catalogue.
Yet more amazing is the celtic blade from the middle La Tène period (2nd century BC) that came up somewhat later in
Iron, Steel and Swords script - Page 502

an auction in April 2016. It definitely employs two very well made twisted stripes rods. Here is a picture and thedescription from the auction house.
Let's see what seems to be definitely known as we ascend upwards in time:
Sword Data; Time / Place

Pattern / Structure

SourceMiddle Latène (250 BC - 150 BC)- Unknow location

Structural piling; face welding appears.
- 2 striped rods (and anthropoid iron hilt)- 2 twisted striped rods
First indications for twisting. Not in sci.
literature

Pleiner; Lang & Ager
- Antique trade- Unknow location- Antique trade

Late Latène (150 BC - 0) swords- Heiligenstein / Speyer (Germany)- Llyn Cerrig Bach/ Anglesey (England)

Three striped rods all through the blade. Phosphor contrast.

Late Latène
Sword with full pattern welding- Cuvi (Italy)First known example with twisted striped
Ypeyrods and complex structure in the sci.
Maederliterature.
PleinerThis is the fully pattern welded No 12 swordof Pleiner

Latène swords found in- Wachock / Ilza (Poland)- Saône / France- Museum Rouen / France- Port Switzerland

Some pattern welding.

No Roman pattern welded swords from the
1st century AD.

Ypey
Lang & Ager
Antique trade

Ypey
MaederAs stated by:
Ypey

However, from the 1st half of the 1st
century AD we have Pugios with stripe
patterns from- Munich, Germany- Leuven, Nijmegen, Velsen (Netherlands);- Mainz (Germany)

Most Pugios, however, are not patternwelded. The ones that are seem to havepattern welded stripes only for decoration.
Typically the "classic" 4/3 iron/steel layer
package was used.

Ypey

Spathae, around 200 AD- around Oslo; (Norway) with Victoria/ Mars
incrustations- South Shields / Durham (England)- Lauriacum / Linz (Austria) spatha

Fully pattern welded- 5/4 low/high phosphorous steel plates;
some twisting.
- 2 counter twisted rods.
- 6 torsion strips on both sides!

Ypey

Around 300 AD
Danish bog spatha

Climax of pattern welding technique

500 AD - 1000 AD

Percentage of pattern-welded blades rose;
dramatically after ≈ 500 AD, peaked to ≈as far as investigated by
100 % during the 7th century, and fell again Lang & Agerduring the 9th / 10th centuries.
After 800 AD swords with pattern-welded
inscriptions appeared

In England

MaederThat is not particularly illuminating. But what, exactly, is it that we want to know? It is quite simple. We want to know
how the following three techniques originated and evolved:
The making of striped rods; including the selection of "bright and "dark" steel.
The twisting / grinding of the striped rods.
Faggoting of the two materials before making a striped rod.
How, where and when? From the above one might guess that pattern welding evolved in Celtic regions north of the
Alpes. But we simply know too little in general, and next to nothing about the use of faggoting in particular. And let me
say it once more: If low / high phosphorous steel was used for the bright / dark parts, no clear pattern could result
without first faggoting, i.e. homogenizing the phosphorous concentration, since phosphorous is always distributed rather
inhomogeneously in the "raw" iron /steel. And phosphorous steel was used a lot!

Iron, Steel and Swords script - Page 503

Did you appreciate that I have hidden a contradiction in terms in the statements above? No? I thought so. Let me
explain: If you are able to select the right steel grades and you can do faggoting, you do not need to go into pattern
welding at all. You could make a superior all-steel swords right away. That pattern welding nevertheless dominatedsword making (but not sax making) for about 3 centuries then tells us that:either the conditions above were not fully met, then pattern welding might have made sense,or they were met and pattern welding made no sense from an utility point of view - but people liked to have"pretty" swords.
The compromise was the full-steel sword with a pattern welded "veneer" that we find so often around and after 300
AD.
It is not clear to me when the first striped rod was made. The "Hermann Historica" sword shown here definitely shows
two striped rods running the length of the blade. A (better preserved) second sword looks like it also incorporates stripedrods but the catalogue picture are not conclusive.
Unfortunately no provenance is given for these swords. They are supposed to be Celtic and from the middle La Tène
period (3rd century BC). While there can be no doubt about the Celtic origin of these remarkable swords, the dating
is not beyond reproach since Celtic swords with an anthropoid hilts are typically assigned to the late La Tène (1stcentury BC) period.
We thus can be sure that Celtic smiths understood and used pattern welding with striped rods as early as about
100 BC, possibly earlier. We don't know, however, if Celtic smiths invented pattern welding with all that implies or ifthey imported the technology from somewhere else. While I'm not aware of pattern welding being practiced outsideof Europe in the first few centuries before the common time, that doesn't mean much. We may not have discoverd
the relevant artifacts or we may not have given them proper attention. Having said all this, I nevertheless like tostate:

Pattern welding was invented by
Celtic smiths sometime between
300 BC and 100 BC.
The Celts used the technology, and so did the Romans. Around 300 AD pattern welding was routine and "Roman"blades with incredibly complex strucures were routinely made. However, we do not know much about the time
between 100 BC and 300 AD.
Let's stop here and look at the second point from above: What happened to pattern welding after 300 AD?

How Pattern Welding Matured Between 300 AD - 600 AD
Good headline - I just don't know much about the topic. All I could figure out so far is that "late" pattern welded swords
were found in graves all over (Northern) Europe. I have no idea about statistics (percentage of graves with swords,
percentage of pattern welded swords, where and when) and thus will give you only a few numbers from one tiny area forthe beginning:

Iron, Steel and Swords script - Page 504

Area of "Sindelfingen swords"
Sindelfingen is a town about 15 km south-east of Stuttgart, sporting a large Mercedes plant. It is likely to be an
Alemannic settlement like all towns in South-West Germany with names ending on "-ingen". The Allemani graves in the
Sindelfingen area are by no means special; there are plenty similar ones all over South Germany. I only focus on thembecause Dorothee Ade compiled a detailed analysis of what has been found in the Sindelfingen area in her 2012 PhD
thesis. Most of the stuff is from ancient cemeteries, some from single graves.
Starting about 1860 people payed some attention to artifacts from old times other then treasure that were occasionally
dug up, and some of the stuff ended up in museums. Nowadays the location of several ancient cemeteries are known
but the graves are left alone for future generations of archaeologists. We already know of another Alemannic cemetery in
Pleidelsheim, just to the North in the map above, and unexpected finds are made all the time, too (see below).
I'm talking mostly about Alemanni graves here. The Alemanni, as pointed out before, coming from the North (andEast), crossed the Roman Limes, the fortified boundary "wall", in 260 AD and occupied parts of what is now South
Germany, Switzerleand and France. After the official end of the Roman empire in the second half of the 5th century,
the Alemanni were more or less dominated by Ostrogoths in the East or the Frankish Merowingians in the West.
The Alemanni were nevertheless a culture that has left deep traces until their nobility was wiped out for good at the"blood court at Cannstatt" (Blutgericht zu Cannstatt) in 746. What happened was that Carloman, the eldest sonof Charles Martel, Charlemagne's grandfather, invited all nobles of the Alemanni to a council at Cannstatt (close to
Stuttgart). Carloman arrested the several thousand noblemen who had followed his invitation, accused them oftaking part in the uprising of Theudebald, Duke of Alamannia and Odilo, Duke of Bavaria, and summarily executed
them all for high treason. The action eliminated virtually the entire tribal leadership of the Alemanni and ended the
independence of the duchy of Alamannia, after which it was ruled by Frankish dukes. Things like that happen when
you neglect to invade Gaul (now called "France") from time to time!
Anyway , the Alemanni buried their mighty ones with their weapons, and that included pattern welded swords. Here isan especially interesting burial in Niederstotzingen from around 600:

Iron, Steel and Swords script - Page 505

Alamanni grave in Niederstotzingen / South Germany(about 600 ±)Large picture plus a picture of the real things
Source: Old drawing shown in many places, e.g. here or in Menghin'sbook

Three warriors, each fully equipped with a big sword, a sax, and many smaller items. And one of those warriors was- surprise! - a woman as a relatively recent DNA analysis proved 2).
Here is what those swords might have looked like:"Sindelfingen swords"
Large picture with more examples
SourceIron, Steel and Swords script - Page 506

You don't want to see drawings but the real thing? OK - here are some of the newest ones:

Arian (left) und Tarik Wissendaner show what they
foundin 2012 while perusing an Altingen construction site.
Source: Local newspapers

Altingen is on the edge of the circled area in the map above. While South-German museums are full of (patternwelded) Alemanni swords, there seem to be very few pictures around. Manfred Sachse showed a good one in his
book, and this link hub leads to a few more.
I have also started to take pictures myself; here is one (large scale) example. Even more pictures can be found in
this link
So what do we know about the Alemanni swords found in the "Sindelfingen" area? Here is a list of what was found injust a few places in the area investigated:
Place

No.
gravesGraves with
SpathaGraves with
Sax

Hailfingen

661

25

3.8 % 41

6.2% 500 525

Schretzheim

630

105

16.7% 82

13.4% 500 525

Holzgerlingen

302

12

4.0% ?

? ≈ 550

Nusplingen

278

15

5.4% ?

? ≈ 550

Marktoberdorf

238

24

10.1% 68

28.6% ≈ 550

Esslingen-Simau

222

16

7.2% 52

23.4% ≈ 550

Sontheim

197

178.6% 26

13.2% 550 600

Heidelberg-Kirchheim

149

10

6.7% 13

8.7% ≈ 500

Güttingen

113

98.0% 22

19.5% ≈ 590

Sindelfingen

?

(21)

? 28

? 450 500

Sums / Averages

2.790

233

8.35% 332

15.02% 450 600

Iron, Steel and Swords script - Page 507

Time
HorizonEven if half the graves were for (unarmed) females, it is clear that not all men and women had a sword. But whoever
had a sword was very likely also in possession of a sax. Some, however, had only a sax. By the way, the town
names ending in "ingen" signal Alemannic origin. In contrast, the ending "Heim" (=home) signal Merovingian
dominance. From some towns it is known that the name changed after the Merivigians took over, e.g. from
Hessingen to Hessigheim.
Pretty much all of the swords in the table above were pattern welded. The first blades without pattern welding were fromthe beginning of the 7th century and their number increases towards the end of the 7th century. As far as one can tell,
exclusively twisted striped rods were used for pattern welding, producing simple herring bone patterns (like in the picture
above or here) or more complex ones like in the "Ingersheim sword" (almost in the area discussed above). No complex
chevron or palmette patterns have been found.
So much for the larger Sindelfingen area. But what about the rest of Europe? And for times after about 600 AD, when
Sindelfingen ends? Tall questions with very short answers:
As far as sword blades are concerned, the technology appears to have been about the same everywhere in(Northern) Europe. Pattern welding was the standard. However, I have yet to see blades that surpass the 350±
Nydam / Illerup blades. Around 600 AD the first sword blades that are not pattern welded but made by laminating
pieces of supposedly faggoted steel appear in some areas (like South Germany). In other areas (like England)that transition might have happened somewhat later. Pattern welding, however, never went quite out of style foranother 400 or 500 years.
We need to be a bit careful about the statement above. A corroded pattern welded blade might just appear not tobe pattern welded. Look a the one right below or the ones in the link. Was pattern welding involved in the one
below? It doesn't look like it but only X-ray pictures or metallographic investigations will tell for sure. Indeed, more
recent X-ray investigations did produce evidence that pattern welding was used for blades that did not show it.
Contrariwise, a blade with a clearly visible pattern could have been made from solid steel while the pattern was
only encrusted, inlayed or "damascened" into the surface of the blade.
In contrast, while there are some pattern welded saxes, the majority of that "utility weapon" seems to have been
made without pattern welding. To what extent piling and faggoting was used I can't tell.
What had happened with respect to making pattern welded blades between - very roughly - 400 AD and 700 AD
was and is totally eclipsed by what had happened to the hilt. That was true then and is true now. There are far
more papers in the present literature about hilt details than about blades for that time span.
In other words: For the top-of-the line "show-off" swords the hilt became the distinctive part; it also must havebeen far more expensive than the blade. That doesn't mean that the blade was not top; it just means it wasn't
used for fighting. You don't use your Porsche, Mercedes or Bentley four-wheel drive luxury off-road car to actually
go off-road either. For menial jobs you have other cars, not to mention people, for God's sake. But your Porsche
would be up to the job! We just don't have all that many fighting swords from that period, not to mention thatwarriors might have used a sax for that.
In other words: As far as steel technology and pattern welding is concerned, the technology was established and didn'tchange much for several centuries. That the focus shifted to the hilt was then to be expected. Basic car technology withrespect to the "mechanics" of cars became an established technology around 1980. Gone are the times when youngmen (like me and my buddies) discussed at length and with a lot of emotions the relative advantages and shortcomingsof suspension systems (Längslenker, Querlenker, Schräglenker, Raumlenker... there are no English terms because theAmerican car industry has yet to discover those techniques). Nowadays the sound system of your car is far moreinteresting than the suspension system.
In other words:

Decadence!

Iron, Steel and Swords script - Page 508

Gold hilt spatha, Stotzingen, Germany; Ellwangen
museumSource: Left: Ellwangen / Germany museum
Right: "Photobucket", Matt Bunker's (medicusmatt) picture

Is that a pattern welded blade? It doesn't look like one but one must be careful in making such a judgement. It wascertainly a sword for showing off. Gold was and is in short supply in Northern Europe, and the little that was pannedaround the Rhine must have been very precious. I doubt very much, however, that a sword with such a hilt would
have been any good in a fight. It has no pommel, must be badly balanced, and easily slips out of your hand.
Gold hilt spatha were in use from about 450 AD – 490 AD and are seen by someas derivatives of Romano-Byzantine designs. Alemanni mercenaries, serving in thearmy of the Byzantine empire, might have brought them home as a kind ofmemorials and show-off piece. after they This link, this one, and in particular thisone gives a few more pictures. King Childeric's sword from about 480 AD embodies
the culmination of the gold hilt sword and also leads over to the lavish use of
almandine (red garnet) and gold adornments in the time span from (roughly) 500 AD- 700 AD.
The gold hilt swords could be seen as the first step into the new fashion ofemphasizing the hilt. This is not so interesting to us here (we are into steel, notgold, after all), so I only give you a (long and lavishly illustrated) special module on
the hilt business.

Illustr.
ModuleFancy Hilts

Hilt fashion development, however, is good for something: dating swords! Hilt fashions changed more quickly with timethan blade fashion, just look at the years before about 300 AD. Certain types then are seen as typical for certain times
and areas. Fancy hilts, containing gold, silver or bronze, corrode far less than iron or organic materials and often theseparts are about all that has been left.
The reference for hilt fashions is still the 1939 book of Elis Behmer. He sifted through much of what has been found inconnections with swords, in particular the metal pieces left from hilts and scabbards. Pommels, cross-guards, chapes,
lockets and so on in later "migrations period" years. Behmer's successor, up to a point, is Wlifried Menghin with his
book "Das Schwert im frühen Mittelalter" (Swords during the Early Middle Age).
It's all in the special module. We now look at:

Iron, Steel and Swords script - Page 509

The Years After 600 AD
As far as hilts are concerned, one can see In Behmer's systematic that hilts and pommels became less fancy once
more. Here are two examples from Behmer's book:

Type 8 (left) and type 9 sword grips after Behmer
Large picture with more examples and explanations
As far as blades are concerned, we have a (slow) transition from the Merovingian / Vendel / ... pattern welded "fancy
hilt" sword to the Frankish / Viking non-nonsense (laminated/piled) all-steel sword. This took quite some time (400+years) The new kind of sword will be dealt with in the next chapter.
The History of Discovering the Pattern Welded Swords of the 1st Millennium AD
People must have unearthed 1st millennium swords all the time without looking for them. Farmers unearth things, andso do builders, peat diggers and children. But interest in old things other than treasures was not large before about
1750, when serious archaeology started by dedicated digging in Pompeii and Herculaneum. It took another 100 years
before old rusty iron found some interest, and yet another 100 years needed to go by before the science of iron andsteel had developed to a point where one could try to figure out what old iron / steel artifacts could tell us.
Let's play the old game and ask:

Who first noticed that he was looking
at the result of pattern welded twisted
striped rods when he contemplated anold sword? When was that?
I certainly don't know. I have sifted through 100+ old papers but couldn't figure out who exactly had made the firstdecisive step in the right direction. But as we shall see, it will be sufficient to look a the work of just a few prominent
old researchers to arrive at a surprising insight:

Something went spectacularly wrong!
Let's start with Conrad Engelhardt and the Danish bogs. Systematic digging there started in 1859 - 1863, look up the
special modules for details. Pattern welded swords were found and recognized as such by Engelhardt. So what did
Engelhardt state with respect to pattern welding?
Engelhardt published his findings in 1886 (in English) and referred to the swords unearthed in Nydam as being"damascened". This was quite natural if unfortunate. Now let's see how Engelhardt described the process of"damascening" in 1886.

Iron, Steel and Swords script - Page 510

"The Nydam swords are of iron, long, straight, andtwo-edged; the blades are for the most part ninety out of a hundred - richly damascened invarious patterns, and afford good illustrations of
the poet's sword, " the costliest of irons, with
twisted hilt, and variegated like a snake"(Beowulf). Iron wires, arranged in patterns, havebeen laid in grooves made in the surface of theblade, and then the whole has been welded
together, so that the surface must originally havebeen smooth. That we now see the patterns
raised is probably owing to unequal oxidation.
Among the many elegant and ingenious patterns
represented on Plates VI and VII, l would callspecial attention to Fig. 5 and 5a, with borders offlowers freely rendered in twisted iron wire."
Page 52
That is a description of "tauschieren ", and there is no proper English word with exactly that meaning; words like
inlaying, incrustation come close. The proper word would be "damascening" but that is now misleading since it was
misused as another word for "pattern welding" (mostly by Germans). Whatever - we note that Engelhardt in 1886
was obviously not aware of the twisted striped rod technique.
Now lets move up to 1939 and look at what Behmer has to say. He studied the literature quite carefully, and if the"twisted striped rod technique" was generally known by then, he would most certainly refer to it.
Here is the decisive paragraph from his book:"Im Zusammenhang mit"In connection withden Blutrinnen tritt so gut
fullers we find pretty
wie stets Damaszierungmuch always
auf. In jeder Rinne sinddamascening. Eachdann auf dem Grunde längs fuller groove
der ganzen Klinge lange,
contains hammeredparallele, einander
in wires down its
kreuzende, gebogene oder whole length,
wirbelförmig gewundene
probably made from
Drähte, vermutlich aus
steel, running in
Stahl, eingelegt, die in das parallel or wavy,
Schmiedeeisen der Klinge crossing each othereingehämmert sind.
or forming eddies.
Klingen, die keine
Blades without
Blutrinnen aufweisen, sind fullers are often
oft in ähnlicher Weisedamascened in adamasziert.
similar way.
Der Zweck dieser
The purpose of this„unechten" Damaszierung, "untrue" damascene,
die von derthat one should
morgenländischen „echten" strictly distinguishDamaszierung, mit der das from the "true"
Abendland erst in der Zeit damascene, thatder Kreuzzüge bekannt
was only known towurde, wohl zu
the West after theunterscheiden ist, dürfte
crusades, might
der gewesen sein, durch
have been to render
Einhämmern von
the soft material
Stahlstreifen in ein
more strong andweicheres Material dieses elastic by
Iron, Steel and Swords script - Page 511

stärker und elastischer zu
machen."hammering in steel
wires"

Page 38

My translation

54 years went by since Engelhardts publication, and nothing has changed! It is mostly but not completley pure BS,mind you, since some swords have been "patterned" this way.
It was Herbert Maryon in 1940 who coined the term "pattern welding " and, as far as I can tell, had almost the rightideas about the striped rod twisting.
Next, in 1954, the year Germany won the soccer championship for the first time, J.W. Anstee and L. Biek published "A
study in pattern welding" 3) and related their results of attempts to replicate an old pattern welded sword by forging.
Those were probably the first attempts in "experimental archaeology" with respect to pattern welding. They did use akind of twisted striped rod and experienced big problems with fire welding. They did not only use striped rods but also
wires. The idea was to fill the grooves of the screw-like spiral obtained after twisting with a wire to obtain a smoothersurface in order to facilitate welding.
The essential picture of the paper tells it all:Anstee's and and Biek's geometries
We do not need to go into details. It is clear that Anstee and and Biek came close but weren't quite there yet. Hereare a couple of interesting quotes:"Alternate strips of carbon-free and low carbon metal have been thought necessary to produce such apattern, and up to 0.6% of carbon has been reported in some material. As the present work shows, however,patterns are obtained even with strips of the same, virtually carbon-free, iron".
The role of phosphorous iron in pattern welding was not known by the authors. Here we probably have thesource of the myth that patterns could be produced with one kind of steel. That a pattern was obtained
probably relates to their problems with welding:"Some of the difficulties inherent in this natural and apparently simple method of construction were revealed
when a number of such rods were made in the Laboratory. No welding was then possible; the twisted rods
were merely flattened, soft-soldered and ground away to varying levels to reveal the consequent changes inpattern."
What that means is that their weld seams, if "taking" at all, were likely full of oxides and thus could haveshown a "pattern".
"Furthermore, the herringbone and other patterns observed, either on the surface or (on X-radiographs) within
this type of blade, could evidently be produced by (the remains of) composite rods, each pile-forged from thin
strips of iron, and adjacent ones twist-welded in opposite directions"That is the correct idea.
"The answer to the problem of scale removal was now clear. As during the work the oxide layer became
thicker (and duller) it was forced from all surfaces by the twisting stress. The best solution was to allow thescale to form, twist a little, then tap the hot bundle with the hammer. In this manner the strips were finallyscrewed up on to themselves, the whole length being traversed in short sections altogether four times-twice
up and down. Even so, much fine scale was left in the joints; nevertheless, all internal welds there appeared
to be perfect, except at one or two points where lumpy particles had been trapped."
So twisting makes welding easier!?
I do not know when finally everything was right - must have been around 1960. I do know something else, however:Iron, Steel and Swords script - Page 512

The twisted striped rod technique wasan industrial standard in 1850 and earlier!
I have dealt with that already - not so long ago. All of the guys named above must have seen pattern welded
contemporary objects like guns for hunting and military (dress) swords in their time. In the larger German-speaking
areas (including Denmark, etc.) these pattern welded objects were called damascened and were standard issue stuff.
While many smiths or companies employed the technique, mass production of twisted striped rod stuff took place inBelgium.
How Engelhardt and Co. could miss that is beyond me and that's why I say that something went spectacularly
wrong. However, they were men of the pen and not the sword and therefore might have become early victims of the"damascene" confusion, believing that the "damascened" gun barrels and swords they must have seen were madeby "tauschieren"=inlaying, encrusting; just as described by Engelhardt and Co.

1)

Dorothee Ade: "Funde aus frühmittelalterlichen Gäberfeldern auf der Gemarkung Sindelfingen und aus dem nördlichen
oberen Gäu"; PhD Thesis 1991; on-line 2012 in two installments

2)

Tobias Schneider: "Mehrfachbestattungen von Männern in der Merowingerzeit", ZAM (Zeitschrift für Archäologie desMittelalters), Jahrgang 36, 2008; Verlag Dr. Rudolf Habelt GmbH, Bonn

3)

J.W. Anstee and L. Biek: "A study in pattern welding", Medieval Archaeology /1954) p.6

Iron, Steel and Swords script - Page 513

11.3.4 Metallography of Pattern Welded Swords

Wouldn't it be nice if some archaeometallurgis would have written a review about our topic here, including everything
known about the metallurgy of pattern welded swords? Of course, a good review is more than just an enumeration ofwhat has been published. It is rather a careful analysis of what has been published, appraising every contribution as toits correctness, completeness, methodology, and thus relevance. The knowledge thus gathered then is ordered, forexample along the following topics / questions:
Bright vs. dark steel. What was used? With particular emphasize on the phosphorous issue.
General nature of the steels used.
How did the smith select his various steels?
How homogeneous was the blade? Was faggoting used? In what ways?
How good are the welds? Nature, density and shape of inclusions at weld seams? Any indication of special
welding practices?
Chemical analysis of the slag inclusions. Can we identify the origin of the iron / steel this way?
Was there any quench hardening? Followed by some annealing?
All of the above as function of the time and place. How did pattern welding change in one place over the
centuries? How did local know-how diffuse into other regions?
Alas! Such a review does not exist. And I'm not the one who is going to write it. First, because there aren't enoughhard facts out there, and second, because it would be hard and demanding work, the kind that only grad students
love to do. So I can give you only some tidbits from what I found, always with the questions from above in mind.
Let's start with the results of the great old man of iron and steel research: Vagn Buchwald's 2000+ investigation ofIllerup and Nydam artifacts. He looked at lance heads and swords. This is what he found for lance heads:

No

Object
Lance
heads

[C]
%

[P]
%

Hardness

Structure

Slag Properties;
Origin11880 YTL

0.6

0

186
-213

Spheroidized fine grained pearlite

Similar to Valdres; Norway

2

1880
VUD

0.6

0

186
-224

Slightly spheroidized fine grained
pearlite.
Yellowish weld line

Similar to Valdres; Norway

3

1.BLX

?
Small

(0.4 0.8)≈150

Very large ferrite grains, Fe3P
precipitates

Very different to above.
Maybe Western Jutland,
Denmark

4

1.KB? Similar to
above

135
-192

Coarse ferrite grains, Fe3P
precipitates; Neumann bands

Similar to 3

5

1.BQY

?
Small

(0.2 0.4) %

180
-209

Coarse ferrite alternating with finegrained phosphorferrite. Fe3P
precipitates??

6

1880 IUZ

0.2 %

0.2 %

112
-120

Coarse ferrite grains with Fe3P
precipitates; ternary Fe-P-C
structures

Very different from above;
not identified

7

1880
QLN

0.2 %

0.2 %

118
-131

Similar to 6

Probably linked to the one
above

Those lance heads were from the first Illerup deposit, about 200 AD. None of the investigated ones was quench
hardened. No.1 and 2 were outstanding steel pieces, made in Valdres / Norway where "special ores enabled steel
production".
As far as swords are concerned, Buchwald was able to re-examine 8 blade fragments from the Nydam treasure. Here iswhat he found:

Iron, Steel and Swords script - Page 514

Numbers give Vickers hardness at places indicated[C] = (0.4 - 0.6) % in ferritic - pearlitic steel; [P] = 0.2 % in
phosphor-ferrite
Twisted striped rods, good edge hardness but no quenching.
Slag high in Mn but no identification of ore origin is possible.

Striped rods from (0.4 - 0.6) % C and 0,5 % P steel. Edges
fine-grained and homogeneous with some martensite (bluedots), Quench hardening was attempted but not fully
successful.
Slag analysis inconclusive.

Ferritic - pearlitic structure in what is left. Ternary Fe-C-P
structures (0.3 - 1.0) % P, 0.2 % C in the stripes.
Slag rich in P 2O5.

Stripes made from (0.4 - 0.5) % C steel and (0.3 - 0.4) % P,
0.2 %C ternary stuff. Edges extremely fine grained pearlite
and martensite, obviously quench hardened.
Very fine sword!

Pattern welded inner part similar to No. 4157 and No 4154
above. Edges consist of (soft!) phosphor-ferrite with (0.2 0.3) % P.
The striped rods alternate high phosphorous ((0.5 - 0.6) %P) with medium carbon steel ((0.4 - 0.5) % C)).
This sword had already been investigated by R. Thompson
in 1992, who found that the striped rods had been foldedback as shown here and below:

Iron, Steel and Swords script - Page 515

Central part (low carbon) with two different patterned layers
on each side; only one is partially preserved. Homogeneous
fine-grained edges. Not or not successfully quenched.
Ternary Fe - P - C for the striped rods with up to 0.4 % P
and quite different P / C ratios.
High P and Mn concentrations in slag inclusions.

Quite similar to No. 41 above. Not enough left for going into
details.

Irregular pattern, rather pure ferrite and heterogeneous
phosphor-ferrite with up to 0.3 % P. Very soft edges welded
to an already rather soft core. Not a good sword.

What can we conclude from those data? Quite a lot actually:
It would be a hell of a lot of work to produce the review requested above! First you need data, and the data I havegiven you here for just 7 lance points and 8 swords are already quite voluminous and a bit confusing. And what
you see here are are only a few percent of the data that needed to be generated. Note that I have not shown any
one of the several 100 microscope pictures taken for these 15 specimen.
Getting a good idea of what was going on in all of Europe for several centuries would need a close analysis of atleast a few hundred swords. This needs still to be done.
So no review yet. Nevertheless, the results shown above do allow to draw some conclusions and to make educatedguesses:

1. We had only only 15 specimen but a few were quite similar to each other and quite different to the rest. Somewere very good and some were very bad. In particular, among just 8 swords one had soft edges welded to a hardercore, something we have encountered before, and one was soft throughout.
We might conclude that different places had different traditions and skills. In fact, there is evidence from other but
metallurgical considerations that at least for the time span covered by the Danish bog finds (300 AD±) "simple"
objects like lance heads were made locally, while complex pattern welded swords were imported from the"Romans". There seems to be some evidence that the Roman smiths worked along the Rhine, in the occupied
territories that now are Germany, France, Belgium and possibly the Netherlands.
When the Romans "left" and the Alemanni and all and sundry moved in, the art of smelting iron and steel plus
making pattern welded blades was still in place, and we might assume that in the later period Alemanni andMerovingians smiths also knew how to forge fine pattern welded blades.
Iron, Steel and Swords script - Page 516

What happened elsewhere, in particular in Scandinavia and in "the East", where pattern welded swords have also
been found in somewhat later times (after 300 AD), I don't know. But without a highly organized and export oriented
Roman weapons industry it is likely that local smiths did the best they could but could not come up to the oldstandards most of the time,

2. All 8 swords investigated used some kind of phosphorous steel for producing a pattern. Or worse, a ternary Fe C - P alloy. Phosphorous stuff is great for the "white" part of the pattern. It also provides for some hardness
compared to wrought iron and might even offer some corrosion resistance. Here is a picture from my own work on asword fragment from the Nydam treasure. The phosphorous steel shows the typical "ghost structure".

Stripes of phosphorous steel and regular (wroughtiron) steel
The bright strucure in the P-rich regions are "ghosts".
Source: The picture was taken by one of the indispensable gradstudents (Jan-Hendrik Morjan in this case)

However, phosphorous steels cannot be quench hardened and are prone to "cold shortness", i.e. it becomes brittle
when it is cold.
Phosphorous steels are nevertheless a good choice for pattern making. As long as the rest of the blade andespecially the edge consists of good steel, the edge could be hardened and the cold-shortness didn't matter much.
The alternative to phosphorous steel is a combination of hard and soft steels (or wrought iron) for making the basic
striped rod. This is not so good for the simple reason that carbon diffuses rapidly in iron and at the always claimed
1200 oC (2192o F) needed for welding, carbon atoms would cover a distance of about 10 µm in one second in thefcc phase then prevalent. In 100 seconds it would be 100 µm or 0.1 mm (the distance increases with the square rootof the time!). Given the total time at high temperatures, the carbon concentration would tend to wash out and sowould the pattern. In the worst case, instead of having, for example, a striped rod with sheets of 0.2 % and 0.7 %carbon, you end up with a rather homogeneous piece with (0,2 + 0.7)/2 % or 0.45 % carbon. Please note how
cunningly I avoided to use the equation sign - so still no equations here!
Don't tell me now that I'm wrong because for modern smith this seems to work. They use two kinds of steel without
phosphorous. Yes, true, but they do not use two different carbon steels. Whatever they use also has different
concentrations of, for example, manganese (Mn) or other alloying elements, and it is a safe bet that these elements
and not the carbon are responsible for the pattern. Phosphorous (and all other alloying elements) diffuses muchslower than carbon, so the pattern does not wash out. But for the same reason phosphorous is always distributed
very inhomogeneously in the primary bloom and in the double pyramids, currency bars, clods, or whatever madefrom the blooms and used for trading. The unavoidable conclusion is:Iron, Steel and Swords script - Page 517

If you use phosphorous iron forpattern welding, you must faggot it first!

The reason is clear; I have discussed it before: If the phosphorous concentration varies down your striped rod, thevisual contrast varies too. From black / white to light grey / dark grey or whatever. This is not what you want to see.
Of course, nobody so far has investigated how severe that effect would be or, in other words, what kind of tolerance
window exists. Maybe phosphorous concentration variations of ± 20 % would still be OK, maybe that's already far
above the limit. We don't know at present.

3. We do not know much about faggoting from analyzing sword blades. Buchwald and most everybody else nevereven mentions it. Analyzing just cross-sections of blades, the standard technique, will not allow to assess the issue
and we thus have almost no data at all. Buchwald mentions several times that the structure (of a cross-section) isvery homogeneous and that might be a weak hint that faggoting was employed.
So far we have only Maeder's data showing that faggoting was used at least in the second half of the 1st
millennium, it seems.

4. Looking at just 8 swords we got 2 very good ones with remarkably hard edges, 4 were acceptable, and two were
lousy. The very good ones were quenched and it worked! The edges have a rather high hardness. The makers of theother ones might have tried to quench harden them too, but martensite will not form in phosphorous steels, no tomention wrought iron. We might conclude that quench hardening was known and used but not understood around
300 AD.
That is one of the things that have changed in the next few centuries. Maeder's two fully analyzed blades, a spatha
and a sax from 600+ AD show signs of a sophisticated hardening process, where parts of the blade might havebeen protected from cooling too rapidly, akin to the celebrated (much later) Japanese process. It is, however, far too
early to be sure.

5. Determining the chemistry of slag inclusions in the different parts of a sword blade and relating them to the originof the iron / steel in question is no yet possible for swords but for the simpler lance heads. Buchwald, who is theexpert for this, could not yet do it. However, using all the modern analytical techniques will one day allow todetermine specific "markers" for a given blade, a kind of fingerprint, that will allow to place it into a specific context as soon as the required large data base has been implemented.
All of the above relied on Buchwald's and Maeder's work. Is here anything else? There certainly is - I just couldn't findmost of it. Or it is outdated. The stuff I found was often published in rather obscure journals so it is hard to know whatelse is out there. But whatever there is, it is not much. So I give you only one more example here and some more in a alink to a science module hub. I hope that the number of examples covered there will increase with time.
Jiri Hošek and Jiri Košta 4) published a paper in (probably 2013) about themetallurgical analysis of two swords found in graves in the Stará Kourim stronghold(Kourim, Kolín District), located in central-eastern Bohemia, Czech Republic; not
far from Prague. The swords are from about 825± - 975±. One was pattern welded(akin to the Ingersheim sword but with four twisted striped rods an both sides), one
was not.
Here is one of the many pictures they produced. It shows part of the cross-sectionof the pattern welded sword

Section of the pattern welded sword

Iron, Steel and Swords script - Page 518

ScienceModuleStructure P.
W. swords

Their major results, in short, are:
The core consists of fine-grained eutectoid steel (i.e. 0.7 % C).
The twisted rod panels consist of ferritic-pearlitic layers (about 0.5% C) and phosphorous ferrite.
Some of the welding lines are accompanied by chains of very fine inclusions and welding is not always
perfect.
The welded-on cutting edges contained hypereutectoid cementite - pearlite structures with a carbon content
of up to 1.4%.
The blade was cooled down rather quickly but was not really hardened, presumably because thehypereutectoid edges were already hard enough.
The steel for the edges might be crucible steel ("wootz") imported from the South-East.
What do we learn from this? First, that phosphorous steel was still used for pattern making. Second, that fire welding isa tricky business. Third and most important, that some smith finally had a good knowledge of carbon steel. If the highcarbon stuff was actually imported from the South or produced in local bloomeries (definitely possible according to theauthors) doesn't matter. It has been recognized for its value and could be procured somehow.
Personally I tend to believe that the use of high-carbon steel went hand-in-hand with a better control of local bloomery
processes since large amounts of wootz imports should have left some traces in the literature. But that is just an
opinion; we will encounter some evidence for wootz imports right in the next chapter.
That's it. I have not found much more than that offers new insights onto the metallurgy of the pattern welded swords.
But more and more people are at it. Time will tell!

1)

Dorothee Ade: "Funde aus frühmittelalterlichen Gäberfeldern auf der Gemarkung Sindelfingen und aus dem nördlichen
oberen Gäu"; PhD Thesis 1991; on-line 2012 in two installments

2)

Tobias Schneider: "Mehrfachbestattungen von Männern in der Merowingerzeit", ZAM (Zeitschrift für Archäologie desMittelalters), Jahrgang 36, 2008; Verlag Dr. Rudolf Habelt GmbH, Bonn

3)

J.W. Anstee and L. Biek: "A study in pattern welding", Medieval Archaeology /1954) p.6

4)

Jiri Hošek, Jiri Košta: "SWORDS UNCOVERED AT THE BURIAL GROUND OF THE STARÁ KOUØIM STRONGHOLD(9TH CENTURY) FROM THE PERSPECTIVE OF ARCHAEOLOGY AND METALLOGRAPHY". No proper reference is
given

Iron, Steel and Swords script - Page 519

11.4 The Transition to All-Steel Swords

11.4.1 Viking Swords
What are Viking Swords?
The first thing to note is that there is no such thing as a "Viking sword". In fact, I'm strongly tempted to proclaim that
there is also no such thing as a Viking. There is, however, a kind of consensus that people who lived in Scandinavia
between 800 - 1050, roughly in areas now known as Denmark, Sveden and Norway, are called Vikings. The origin ofthat name is not clear. One interpretation is that the Old Norse word "vikingr" signifies "one who came from the"vik"=fjord creek, inlet, small bay". Since the guys who came from there typically murdered, plundered, raped and took
slaves, the word "Viking" became a synonym for "freebooter, sea-rover, pirate". But that is far from certain, and themeaning of "Viking" is much debated among present-day scholars.
Whatever and whoever the Vikings were, they were given far more to wielding a sword than a pen. They certainly had
swords, used them, and quite a few were buried with them. That's why we do have swords that once belonged to a
Viking, and you can call such a sword a "Viking's sword", of course. However, the term "Viking sword" denotes
something quite different;spelling details do count here. It is perceived as addressing a particular kind of sword, aspecial class, related to and made by Vikings. While we do have a lot of Viking's swords, they are not necessarily
Viking swords. Nice little (s)word play here. Indeed, historians held and hold the view that most swords of the Viking era
were produced in a region along the Southern part of the river Rhine in the heart of the Fankish / Ottonian / German
empire, and that the Vikings, like everybody else, purchased or stole these swords.
We do not know much about Viking's swords from the Vikings themselves. They didn't write much since most of themwere illiterate. In this they weren't much different from everybody else at this time. The big difference is that before about1000 AD they weren't Christians and thus did no have abbeys and monasteries, full of monks and such that could andwould write a lot.
A Viking intellectual who felt inclined to write something typically restricted himself to one or two sentences expressedin runes. Runes are a rather primitive script, more or less just a vague remembrance of the glory of Latin writings. All
the tall tales from Northern Europe relating to Vikings are from later times.

SpecialModuleVikings

In contrast, we know quite a bit about the Frankish
empire (and its successors) from extensive
contemporary writings that survived until today. That is
not to say that these writings are fully reliable. Theremight be quite a bit of mythology involved, take theRoland saga as example. Not to mention that thereligious people forged documents as a matter ofcourse 2). With careful interpretation we do get firsthand information, though. What we do not have aremany Frankish swords.
Nevertheless, in serious history the general view
emerged that superior iron and steel weapons, inparticular swords, were a monopoly of the Frankish
empire, exported all over Europe and parts of Asia.

SpecialModuleFrancia

Swords made elsewhere could not measure up to the Frankish swords. That is particularly true for the famed"+VLFBERH+T" swords.
This view has been (partially) contested more recently; I'll get to that. Meanwhile I'll give you two special modules
about the Vikings and Franks plus more background to Viking's swords.
As ever so often, the badies are better remembered than the goodies. As times passes on, they might even get a bit
glorified, witness "pirates" in general and Attila the Hun in particular. To quote the present (2014) Queen of Denmark,Margrethe II: "Up to this very day, the interest in the fascinating and glamourous Vikings has never abated". Well - yes.
Just like dinosaurs. You like 'em much better as soon as they are definitely extinct.
The Vikings are often portrayed as ruthless robbers and conquerors, only bend on murder, rape, robbery anddestruction. Alternatively, they are described as mostly peaceful and innovative farmers and traders, given to longand profitable business travels. Just their young ones got muddled up in some deplorable excesses now an then;sowing some wild oats and so on. The truth is probably not quite in the middle in this case. The more advanced andliterate contemporary cultures have nothing good whatsoever to say about them. Of course those writers werebiased. You tend to overlook the amiable properties of the guys who burnt down your town, raped your women, andtook all able bodied and not yet killed people away as slaves.
While it is true that Vikings were also large-scale traders, one of their most profitable trade goods were slaves.
Slaves did no leave behind much written material for obvious reasons but we can be fairly sure that they weren't allthat fascinated by their glamorous tormentors who didn't smell so good - imagine 80 men spending 2 weeks in asmall boat without a rest room 1). Or, maybe, it's better you don't.
The map below gives an idea about Viking home lands and settlements, their way around Europe along rivers andIron, Steel and Swords script - Page 520

sea shores, and their dash across the open sea to Iceland, Greenland and America. The special module gives somemore details about the Vikings.

Viking places and travel routes
More maps here and here
Source: Adopted from "Der Spiegel", 36, 2014

Here we are not so much interested in the Viking culture, to use that word loosely, but in their swords. Below are
pictures of typical "Viking swords":

Typical Viking sword with pattern welded blade
Source: Privately owned sword in Denmark. Thanks for letting me havethe pictures

There is no shortage of Viking's swords and pictures thereof. It is a safe bet that any (historically inclined) museum inNorthern Europe has some Viking's swords. Here are examples from the National Museum of Denmark in Copenhagen:Iron, Steel and Swords script - Page 521

Typical Viking sword hilts as shown in Copenhagen
Large pictures (with 2 more hilts)
Source: Photographed in the Copenhagen museum

A lot more pictures can be found in the the following links:
Regular size pictures
Large pictures
The blade of typical Viking swords was broad, double edged with both edges being sharp, and tapered in both ways:
Profile tapering, meaning he sword gets narrower closer to the tip.
Distal tapering, meaning its thickness decreases from the base to the tip.
The sword was a dedicated cutting weapon, well balanced and responsive, made for use by only one hand since theother one held a shield. Blade lengths from 60 cm to 90 cm have been found; 70 cm - 80cm might be most typical. In
later times blades became as long as 100 cm. The total weight of a sword was between 1 kg - 2 kg; a bit on the heavyside. The pommel, even so it's hollow, may have served as a counter weight, in contrast to the pommels on earlier
swords.
These swords were optimized weapons despite their fancy hilts. "Many modern replica blades are not made with any
distal taper, resulting in a blade that, when wielded, will feel unresponsive and heavy" asserts Wikipedia, and I tend tobelieve that. Details of the sword geometry do count.
Interestingly, museums in locations far outside the Viking sphere of influence also have "Viking swords". Here is an
example.Why is that? Because, as mentioned before, there is no such thing as Viking swords but just Viking era
swords or Viking's swords. Vikings simply used the same kind of sword as everybody else in Northern Europe (andbeyond), and they did not invent it. While Vikings smelted iron and Viking smiths made lots of iron things including quite
likely swords, only Frankish smiths made the top-of-the-line swords.
All the fancy swords possessed by Viking chieftains are likely of Frankish origin. The not so fancy ones that were madelocally emulated the Frankish type. That is not only true for swords but for many things: The Vikings liked the Frankish
stuff and copied it to a large extent (if they didn't rob it).

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How do I know this? Do I have any proofs for these claims as far as they concern swords?
Good question.
The answer is: No, I do not have direct and irrefutable proof for the sword bit. For the rest, yes, it is easy to prove but we are not interested in copied jewelry, for example.
I could provide references to any number of learned papers that, based on circumstantial evidence, come to theconclusion that Viking's swords were of Frankish origin - but nobody so far could provide straight-forward simple
facts for that. Unfortunately for us, the Franks or Carolingians ceased to deposit grave goods at the beginning of
the eighth century west of the Rhine, and at the end of that century everywhere. That means we have almost no
finds from the core region where the superior swords were supposedly made after 800. We have indirect evidence,
however, and in what follows I will give you now some ideas about that. More details can be found in the module
about the Frankish Empire.
As a first piece of minor evidence, look at the hilts shown in the "Stuttgarter psalter"" from 825 AD. The people in thesepictures are definitely not Vikings. Now look at their swords:

Some sword hilts form the Stuttgarter psalter
Large picture with the rest
Source: Württembergische Landesbibliothek, Stuttgart; on-line libraryThose hilts would be addressed as "Viking", and the general shape of the blades (look at the large picture) also fits
the picture.
Among the many swords exhibited in Rothenburg / Germany are a few that look a lot like the ones shown in the Psalter.
They are labelled "Viking swords" but who knows where they came from - the Vikings never made it to Rothenburg inSouth Germany3). Here is one:

Sword hilt from the (early?) 10th century as shown in
the Stuttgarter Psalter
Source: Internet at large; originally probably from Niels Provos (thanks!);
photographed in the "Reichsmuseum Rothenburg"; Germany.

More evidence for the Frankish origin of Viking's swords can be found here.
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The message is: beware of "Viking sword" labels. Serious literature typically does not discuss Viking swords but Viking
era swords, i.e. swords made and used in Europe between about 800 - 1050. They are classified by their hilts and thegeneral shape of their blades but not by the metallurgy or the forging technology of the blade.
So far I have only looked at the hilts of Viking's swords. We do like good-looking hilts on interesting blades, of course,
just as we like good-looking frames around interesting pictures. We do not really care for hilts, however, we care for theblades to the extent that they tell us something about the progress of iron and steel technology. The big question thusis:

What about the blades of
Viking era swords?

Viking Sword Classification
Before I tackle this issue, I need to address the issue of sword classifying systems. A lot of swords aficionados arevery keen on classification systems and while there are good reasons for that, these systems are not really of muchinterest to us here.
We have already encountered the system of Behmer in the context of migration period swords, and found it very usefulfor putting hilts into an approximate temporal and spatial context (when and where).
Behmer's system covers swords from about 300 - 800. For the Viking era and early middle age, you turn to thesystems of:
Ian Petersen, as described in his 1919 book "De Norske Vikingesvert" (The Norwegian Viking swords).
Petersen sorts sword types mostly by the hilt characteristics, like Behmer.
Ewart Oakeshott in his 1960 "The Archaeology of Weapons. Oakenshott improves on Petersen's system andtakes into account also the blade morphology, covering mainly the time after the middle of the 11th century.
Alfred Geibig supplied the newest and most elaborate system in his 1991 book "Entwicklung desSchwertes im Mittelalter" (The Development of the Sword in the Middle Ages). He categorizes a lot of of
blade and pommel dimensions of swords from the dawn of the 8th century through the close of the 12th. Hereare some pictures of 15 blade types and 12 pommel types (there are more):

Blade and pommel types according to Geibig
Source: An article by Christopher L. Miller in myArmoury.com

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Geibig gives the relation between blade and pommel types, all kinds of numbers for properties, and a lot more. So if
you find some old sword from the time horizon in question, you can compare it to Geibig's systematic and identify
blade and pommel type. That will tell you a lot about your sword: At what approximate time was it used in which
general region? Is it a run-of-the mill sword, with many closely related brethren in museums and collections, or arare breed?
What you do not learn is anything about its metallurgy and how it was made. But that is what we are interested inand that is the reason why I don't go deeper into the various systems.
Now let's turn to the actual topic - in the next sub-chapter.

1)

Ahmad ibn Fadlan was a 10th-century Arab traveler who made it to the king of the Wolga Bulgars and thus also Wolga
Vikings. He writes:"They are the filthiest of all Allah’s creatures: they do not purify themselves after excreting or urinating or washthemselves when in a state of ritual impurity after coitus and do not even wash their hands after food".

2)"Taken as a whole, medieval monks and clerics were probably the most prolific forgers of all time. For centuries they
controlled access to official documents, placing them in a perfect position to alter or forge those documents, should they
so desire. And judging by the volume of their output, they evidently did so desire. What's more, their superiors could becounted on to overlook, or even approve, any textual inventions that benefitted the Church" says the "museum of hoaxes"
and every scientist involved in (church) history agrees.

3)

Alfred Geibig meanwhile told me that this sword comes from the "Baumann collection". It goes back to the late 10th
century and originated most likely in the Kazan-Wolga region (Russia). It is not quite as old as the Stuttgart psalter but
dates to 900+.

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11.4.2 Blades of Viking Era Swords
Several of the swords shown here and in the accompanying modules have standard pattern welded blades, technicallyno different from the ones the Alemanni made a few centuries ago. Some blades do not show pattern welding on firstsight but might do so on second sight, especially if you look with X-ray vision. Some blades are all-steel blades, somecarry large inscriptions on the blade (like VLFBEHRT) and some small inlays. In most cases we do not know the exact
age of the blade. We might be able to date the hilt by its particular style or the owner of the grave by radiocarbon dating,but that doesn't necessarily give the age of the blade. Since good blades were passed on from father to son, possibly
acquiring new hilts in the process, some Viking era blades might be far older than their hilt or the guy they were buried
with.
As far as pattern welded blades are concerned, I have dealt with those. There seems to be no discernible difference inforging techniques between Alemanni pattern welded blades from around 600, say, and later Viking era blades from 800
or later. That is no surprise if all these blades were actually forged in the same region, along the lower Rhine. The people
who made them may have been called Celts, Romans, Alemannis, Merovingians, Suebians, Franks or whatever - they
had the necessary knowledge and passed on their skills and trade secrets to their progeny.
So let's forget about pattern welded Viking's swords and turn to the interesting stuff:

Viking era swords include
all-steel swords
With "all-steel" swords I mean swords made mosly from relatively high carbon steel. Maybe from just one piece ofsteel but mostly by piling (or laminating) several pieces.
In fact, after about 800, pattern welded blades slowly disappeared and were replaced by all-steel swords. After about1000 AD only all-steel swords were made. So far historians saw that as an indication that a kind of revolution insword forging techniques took place. Here are some quotes:"Shortly before the tenth century, a new technique of blade forging was developed in the Rhineland. With thisnew innovation, Frankish smiths improved the strength of the blade while also enhancing its maneuverability.
The new Frankish sword became highly sought after by the Northmen as well as by the Saracens to thesouth. This new technique created hard-elastic blades, which were entirely steel." 2)"Eighth-century blades were often damascened, but this practice began to die out in the ninth century,
almost certainly as a consequence of improved forging techniques which produced blades of higher quality
steel." 3)
Is that true? No, it isn't. We shall see why in a moment. First let's look at the alleged revolution from a customers pointof view.
Pattern welded swords could only have disappeared because an alternative became available - all-steel swords - andbecause the customers went for it. What reasons could there be for this behavior of sword owners? I can think of four:
1. All-steel swords became just as good or even somewhat better than the pattern welded ones at comparable oreven somewhat higher costs. Than important people will switch because it is cooler to have the new design. I'm
talking fashion here, as I did before.
If your status is low, you tend to emulate your superiors and thus you also go for an all-steel sword with the newcool shape but with a cheap hilt / pommel.
2. All-steel swords became much better at comparable prices than pattern welded swords. Than anybody in thearmy or otherwise given to killing people by the sword needed to have one; your life is at stake here, after all.
3. All-steel swords became much cheaper at comparable quality. Than all the upper crust guys who were requiredby their liege lords to equip largish numbers of soldiers with weapons would be going for it.
4. All-steel swords were much better and much cheaper than pattern welded ones. No comment needed; large
amounts of money could now be made.
The first point is easy to see. It is simply inconceivable that people who could afford a costly pattern welded sword
with a fancy hilt would settle for less than the best. They might have wanted something different than their ancestors
for fashion reasons but they would not settle for something technically inferior. As long as pattern welded swords
carried the day, all that could be done fashionwise was to change the hilt and to a smaller extent the shape of theblade. As long as your sword is in its sheath nobody sees your fancy pattern welded blade anyway, so it makes
sense to announce your high status by fancy hilts and pommels. So full steel swords must have been at least as
good or likely better than pattern welded ones - and that is perfectly reasonable from a "theoretical" point of view; I'll
get to that.
The second point is obvious; no need to enlarge upon it here.
The third point need a bit of explaining. During the building of the Frankish empire and ever since, the organization of
warfare changed. Before Charlemagne and his peers, an "army" was more or less an assemblage of whatever local
chieftains could raise and put at the disposition for their Overlord. Their equipment consisted of whatever they could
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afford; swords were rather rare; look a the statistics here. Charlemagne's army, while still put together from men
send by his vassals (in particular bishops and abbeys), was heavily armed with standard equipment that was
specified in detail. This cost money and one can be rather sure that cheaper products that met specifications werefavored by the ones who had to pay. The soldier himself had nothing to say in that.
The fourth point is obvious once more.
Whatever point carried the day sometime and somewhere after 800 AD, one thing is also sure: It takes a while
before the last conservative will catch on. I bet that some of you still use old-fashioned incandescent light bulbs,
read texts printed on dead wood, and drive non-German cars. So we must expect that some pattern welded swords
were still around after 800 AD, carried by dyed-wool conservatives or people in more remote places (like England)
who hadn't heard yet of the newest fashion on the continent. We must expect fairly long transition periods for thewhole of Europe even so transitions might have happened far more quickly locally.
Before I go on, let's recall an important fact: While we perceive the building of the Frankish empire as a succession of
war and constant fighting between the top dogs, quite the opposite is true. Many normal people in the heart of Europe
finally did have some peace and quiet for an appreciable stretch of time. The chaos days after the fall of the Roman
empire were about over, civilization and business recovered. Huge stone buildings were raised once more in the cities,
like the Palatine chapel of the Aachen cathedral; built by Charlemagne between 796 and 805:

Inside the Palatine chapel in Aachen, Germany
Source: Internet a large

You need peace and some prosperity to build something like that, not to mention a lot of iron and steel tools. While
we focus on swords, let's not forget that the amount of iron and steel used for making swords and other armor wasalways just a small percentage of allthe iron and steel coming out of smelters. Only a small percentage of all thepeople then living had a sword - but everyone had a knife, and most a scythe, a sickle , a hatchet or the stuff listed
here. In conclusion, the manufacture of iron and steel products must have increased enormously in the 8th / 9th
century to meet the demands of prospering societies and the ever-growing armies. This requires not just a hell of a
lot more people doing business as usual, this requires changes at doing things. In the limited space where iron ore
was dug out, more people would just have been in each others way, for example. And even if digging could bescaled up in one place, you could not scale up the charcoal supply very much without exhausting the local supply
rather quickly. Increasing the iron production required to open up new mines, increasing the productivity by getting
more iron out of the same amount of ore, and utilization of low grade ore that didn't do so well in old fashioned
bloomeries. And so on.
How was that done? I don't know but I do know that you, the ancient iron monger, did not sit down, mulling all thisover, and then proclaim the new ways of doing things. You just did it. And you go better at it. A rapidly increasing
demand for iron and steel in relatively quiet times when one didn't have to run for one's life all the time, facilitatedplenty of improvements for all steps in the production chain just by doing business. Investors were around, and you
also were more receptive to what you heared from other regions, including from empires far away.
So exactly what happened to the iron and steel technology between 750 and 1100, more or less the "Viking era"? And
why?
Let me tell you right away: It's not just me who doesn't know - nobody knows! That doesn't mean that there are notplenty of theories around. Thankfully, we do not need to look much into anything older than 20 years or so, since more
recent findings overthrow most of that. There is still a lot of confusion, however, and on top of that we have the enigma of
the Ulfberht swords; more to that in the next subchapter.
One thing, however, is obvious to me and should now also be obvious to you:

Iron, Steel and Swords script - Page 527

Forging techniques did not improve.
It was iron and steel smelting
technology that improved.
Obvious, isn't it? No? Well - just remember: Forging techniques already peaked 400 or so years ago. A techniquethat produced elaborate pattern welded swords like the ones found in the Danish bogs has already reached its
climax, you simply can't improve upon it. You can only get better products if you supply the master smith with
better materials on a reliable base. And no, it's not that the old master smiths had not discovered hardening by
quenching and so on. You can take for granted that at least some old smiths had working recipes for proper
hardening that would have worked all the time with good material. If they failed, it was the materials that failed them.
Of course I'm no the only one who noted that. Alan Williams, to name just on major sword researchers, knows it, orMikko Moilanen
To illustrate my claim that the demise of the pattern welded sword was not due to better forging but better smelting
techniques, I give you a remarkable figure:FeO ("Wüstite") content in slags vs. time
Numbers 1 - 6 refer to Hermaringen, Großkuchen,
Essingen-Weiherwiesen, Frickenhausen, BeurenWeileräcker, and Metzingen - all towns on the"Schwäbische Alb" not far from Stuttgart / Germany andright in the heartland of Alemanni and Frankish sword
production.
No. 7 denotes slag from Kippenheim / Südbaden /Germany; No. 8 Kierspe / Middle Germany; No. 9
Vinarhyttan and No. 10 Lapphytta; both in Sveden
Source: Andreas Hauptmann und Ünsal Yalcin paper

The shaded areas show typical FeO concentrations in slag from bloomeries or blast furnaces. Concentrations
decrease a bit with time because smelting temperatures went up a bit with time. The (elliptical) dots show
measured concentrations.
This is an amazing figure. It is based on research conducted by two heroes of archaeometallurgy who we have met
many times before: Ünsal Yalcin and Andreas Hauptmann from Bochum, Germany.
What does the figure show? Back when I discussed iron smelting in some detail, I made abundantly clear that the slagof "classical" bloomeries always contains a lot (50 % or more) of iron monoxide (FeO) or wüstite for reasons that arequite clear. In contrast, blast furnaces produce cast iron only if operated with limestone as flux and concomitantly low
wüstite concentration in the slag.
Analyzing the wüstite concentration in slag from different times thus allows to see when the transition from bloomeries
to blast furnaces occurred. This is exactly what the figure shows.
Three conclusion are unavoidable:
1. The transition was gradual and took about 500 years. That is not surprising. We know that blast furnaces andbloomeries coexisted for many 100 years and that some furnaces produced a bloom and cast iron at thesame time,
2. The transition started long before 1000 AD. Around 800 AD, the time of interest here, it had definitely
occurred in the "Schwäbische Alb" region" from where much of the data originated.
3. Smelting with limestone as flux (the reason for the low FeO concentration) was done in several places at thelatest in the 11th / 12 th century - considerably earlier as assumed so far.
This goes right against the "old" wisdom positing that a more or less sudden jump in (forging) technology happened
around 900 AD. What really happened was that a continous progress in smelting technology occurred when things
calmed down again somewhat before the dawn of the "Viking era" as pointed out above. That iron smelters could makecast iron far earlier as believed until not so long ago is not the crucial point, however. The crucial point is that smelting
became far more more efficient (you got more iron /steel output for the same input of ore / flux / charcoal) and that thequality of the bloom increased. In short: you got more and better iron and steel. The bloom was less spongy, cleaner,and various steel grades could be recognized and separated more easily. Control of phosphorous and sulfur was
possible "somehow" too, and so on and so forth.

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Don't forget that the iron / steel people of old knew about the different grades of "iron" already for centuries by then.
They somehow could tell phosphorous iron from plain iron, enabling them to make striped rods, and they knew
about the existence of carbon-rich "hard" steel that they used for the edges. They might have believed that iron andsteel were two completely different materials that just looked about the same (like silver and tin, for example) but
that doesn't matter. They had working recipes to deal with the stuff, including the far-from-trivial fire welding and all
kinds of quenching procedures. If a master smith failed in making a good product on occasion, it was the material
that must be blamed, for sure. There was simply no way to distinguish between good raw material and not so good
one as long as the basic criteria were met.
I won't give you details about the better melting processes and the resulting increase in product quality because we
don't have a clear picture yet. The articles of Yalcin and Hauptmann give some hints but much more work is needed(including a better understanding of the smelting process itself) before the last word will be in. The key, however,
was to raise the temperature by better smelter design (including making it bigger) and by paying attention to details:
kind of ore, pre-treatment of the ore, adding suitable flux (instead of unknowingly relying on the gangue and smelter
walls), and so on. That should sound familiar
All things considered, in the 9th century and later sword smiths by and by could obtain better grades of iron / steel
at lower prices. That resulted eventually in better and cheaper swords because forging became easier. What more
do you want?
So let's look at blades now. Below is another figure that will tell us a lot. It shows the quality of about 100 swords fromthe 10th to the 17th century; thus going far beyond the Viking era. The quality is expressed in seven "grades" like inGerman schools. A "1" is the best grade, a "7" the worst (see the details in the lower part of the figure). All theseswords have been investigated in some detail by metallography.
About 10 swords per century is of course a ridiculously small number for drawing general conclusions. But that is all wehave and against the odds some insights will emerge. Here is the figure; the colors symbolize the numbers of swords
investigated.

Improvement of sword quality after the 10th century
Source. Alam Williams book: "The Sword and the Crucible".

Neglecting for a moment the 10th century "Viking" blades we recognize that the general quality went up as time
progressed. Very slowly, indeed, but swords did get better. Of course, at any time and in any place there were excellentsmiths and iron masters and poor ones, like in every profession. We must thus expect a certain spread in quality at all
times. Nevertheless, general improvements must be due to improvements in the material quality and not so much inforging techniques.
The figure also shows in full brutality the enigma of the 10th± century "Ulfberht" swords. Among the 59"Ulfberth's" swords investigated by (mostly) Alan Williams, about 25% were better, and about 20 % were worse thananything produced in the next 500 years! The rest merits something between grade 2 and grade 6. I have lumped
them together because the grade definition used for these swords is somewhat different from the one given for theother swords. There are about 170 known ""Ulfberht" swords, so Alan Williams investigation covers about 1/3 ofthem and thus has some statistical significance.
We have a real puzzle here. A possible and highly advertised solution was given by Alan William; the next subchapter will go into that.
For now we will look a bit more closely at the blade construction after pattern welding went out of style.

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Making All Steel Blades
While the best possible sword consists of one kind of homogeneous steel with possibly quench hardened edges, I also
allow swords in this category that were made from several pieces of steel by piling. That seems to bring us right back to
the old Celtic times before pattern welding came into its own. However, we need to add one more criterium: Piling now isdone for almost sure with faggotted steel and any piece runs (typically) the whole length of the blade. Something likethis:

Schematics of an all steel sword
Sorry for the clumsy graphics so let's look at the real thing:

All steel sword from the 9th century
1-3 denotes steel, 4 and 5 wrought iron
Large picture
Source (5)This is one of 16 swords (Grave No. 438) that have been found in an early medieval stronghold at the site of
Mikulèice (Hodonín county) in Moravia (Czech Republic); it dates to about 830 - 900. Moravia bordered the Frankish
empire and the swords found there are likely "Frankish". More to this sword and its brethren can be found in thisadvanced module.
The sword shown is remarkable for several reasons:
It is an early very good all steel sword with at least partially high-carbon steel
It carries an inscription done by encrusting twisted striped rods. It is no longer readable but it is definitely not"VLFBERHT".
It has been expertly quench-hardened.
It was forged by piling long strips of (probably) faggoted iron / steel as shown in the schematic figure.
In essence, it is built like a late pattern welded sword but with a coating of good steel instead of the thin "veneer" ofground-down twisted striped rods. That makes sword forging a hell of lot easier, of course. That is also true for other allsteel swords. They were made by piling strips of steel lengthwise to a (possibly) iron core. The steel edges might havebeen welded on, too. Quench hardening was used. As usual, very good and very lousy swords were made this way.
Some were used for show and equipped with fancy hilts and scabbards, some were inscribed with symbols or names.
Fancy hilts and inscriptions were not necessarily a sign of high quality, however. Some of those swords had actuallyrather bad blades.

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Now you wonder. I have been going on at full steam in this subchapter for quite a while and all that happened in thetransition from pattern welded swords to all-steel swords is use plain steel as a kind of veneer on the blade insteadof fancy patterned one? Well, yes, but it is not as simple as it looks.
The question to ask is why that didn't that happen much earlier? The sword might not look as good but it is muchcheaper. At least the not-so-rich ones who lived by the sword should have provided for a good market. I can think ofseveral reasons:
The rich upper crust did not want the hoi polloi to own swords at all and saw to it that swords were notaffordable for all but a few. That only changed in the 9th century when their liegelord asked then to provide
standardized equipment for the soldiers they were obliged to provide.
A pattern welded veneer actually made for a better sword than a solid steel sheet. This could be the case aslong as the solid steel is still pretty bad, with lots of microcracks, large slag inclusion, phosphorous-richzones, and so on. It then was prone to cracking in contrast to an entangled mix of bad steel. A fitting
analogy is rope made from twisting many not-so-good thin filaments. It is always better than a rope with thesame diameter consisting of only one not-so-good filament.
The surface of all-steel swords doesn't look so good if the steel is not uniform and contains visible flaws(large slag or oxide inclusions, large cementite particles, patches of different luster due to inhomogeneous
phosphorous distribution, ...). A patterned surface nicely covers all that. A certain amount of dirt is far more
obvious on a white carpet than on one with a a salt-and-pepper pattern.
There might be more to this but the general direction is clear: All-steel swords need more and better steel thatpattern welded ones. We're right back to square one: Progress in smelting technology enables all-steel swords. No
progress in forging technology is needed. Making all steel swords is actually easier than making pattern welded
ones.
Inscriptions
Many of the early all-steel swords carry long inscriptions while pattern welded swords from the same time horizon
typically don't. Why is that?
A simple explanation suggests itself: An inscription would not go well with the pattern. True enough - but only for huge
inscriptions made in a comparatively artless way. If you consider what artisans could do with the hilts, one could haveexpected very fine and beautiful work on (small) parts of the blade, too.
Some pattern welded swords actually do carry "inscriptions" or adornments. Earlier ones may sport small figures
made from copper or other metals. Later ones might have symbols like rings inlaid into the blade by making thesymbol from a thin twisted striped rod that is hammered into the blade. The smith may first make suitable grooves
into the blade that hold the symbol or he might just bang the (cold) symbol directly into the (hot) blade. Mikko
Moilanen has written a detailed paper about his experiments concerning that; read it if you want to know more.
I'm not yet talking "+VLFBERH+T" or "INGELRII" signatures but far more simpler stuff, essentially just symbols ofsome kind, as shown here:

Symbols and strings of symbols found on "Viking era"swords
Source. From Janet Lang's and Barry Ager's work

All-steel blades might also carry these kinds of insignia. The better known ones carry the words mentioned above; here
is an example Two questions come to mind:
1. What do these symbols, strings of symbols or whole words signify?
2. Why is the material rather special (twisted striped rods) but the execution rather artless?
It appears that nobody before me has asked the second question. Why did the famous smith Ulfberht (if he existed)mark his swords by inlaying crude letters of iron and not perfectly made letters of gold or copper? The prize couldn't
have mattered, just look at the hilts! Moreover, why were the rather crude and uneven letters not made from somesuitable wire of, e.g., phosphorous steel, providing for a nice contrast to the blade steel, but made from hard-to-maketwisted striped rods?
We have two question here. I do not know the answers but I can guess:

Iron, Steel and Swords script - Page 531

The letters are rather big, crude and uneven because:
1. your opponent should be able to see them. And you didn't want to give him aesthetic pleasure uponbeholding your drawn sword, you wanted him to become afraid.
2. It was important that the smith made the inscription. Some specialized goldsmith could do some fancy
engraving on any blade but only the smith who had forged the blade could make the kind of inscription we arelooking at here. I had to be done during the forging of the blade. You can't do it properly anymore after theblade has been finished; it would oxidize to much and get too thin if you heat it up an bang it, and grind it
again. The inscription had to be done by banging to into the blade at high temperatures and thus cannot bedelicate and precise.
Why were the letters made from a twisted striped rod wire? My answers are:1. I don't know. A simple phosphorous steel wire would have done just as well. In fact, simple steel wires werealso used; as far as one can tell mostly in later times.
2. I can speculate. Let's look at an analogy. The portraits of all your noble ancestors that are hanging in yourhall had been painted by "classical" artists, who needed many sittings before they were done. Now, when it
is your turn, all famous artists paint like Picasso, are done after a few hours, and the result takes somegetting used to. You would feel much better if the guy who did you at least signs his work by painting aperfect little miniature picture in the corner in the classical way. That tells you that the guy actually could
have done it in the old-fashioned way. If he doesn't work in the old-fashioned way any more, he must be
convinced that the new way is better.
King Harald V of Norway might have felt this way upon beholding his portrait displayed in the Town Hall of
Oslo:King Harald V of Norway
Source: Photographed in Oslo Town Hall

Now we are almost ready to give the "+VLFBERH+T" swords and his brethren a close look. Before I do that, however, I
need to look at a new and unexpected find: The fully embellished or encrusted 8th century sword shown below was
found in a Bavarian lake by a diver. "It was examinated by the archaeological department of the university and by thearchaeological state collection of Bavaria. The metallurgic and x-ray examinations proofed the sword to be authentic "reports the finder in the vikingsword.com forum.
Here it is:Iron, Steel and Swords script - Page 532

Symbols and strings of symbols found on "Viking era"swords
Source: vikingsword.com forum

To me this sword looks like an all-steel sword that has been embellished with a recurrent motive (as crudely
outlined) on both sides in essentially the same twisted striped rod technique that was used (later?) for making the
VLFBERHT etc. inscriptions. This might be totally wrong but if it isn't, we might make some wild guesses:
1. Making incrustations into all-steel blades with twisted striped rods was a well-known technique in South
Germany, then part of the Frankish empire. Far more complex designs (like the one above) then what weknow from the VLFBERHT swords were made.
2. The known "VLFBERHT" swords are probably just a tiny fraction of all comparable swords produced in the
Frankish empire. Maybe they were mainly for export?
3. Maybe swords with complex embellishments made from twisted striped rods that include letters andsymbols were just a variant or advancement of the old technique of having a kind of veneer with the usual
twisted striped rod patterns? A kind of missing link between old-fashioned pattern welded swords and the allsteel "Viking" or better "Frankish" kind of sword? We just don't know because we have almost no surviving
examples?
Well - there seem to be some more remarkable survivors. One is resting in the Provinciaal Museum van Drenthe,
Holland. Here it is:

The Drenthe sword, front and backside
Another late and strange one
Source: Jeff Pringle; in a 2011 "myarmoury.com posting. The primarysource is an article by J. Ypey 7)

Iron, Steel and Swords script - Page 533

Unfortunately we do not have a date for that sword. If it is "early", say around 800, it would go right with what I
surmised above. It is probably form later times, however; Ypey suspects the 10 th century
While I'm not sure what the "SIGBRHANI" on one side fo the blade signifies; the "+INGERIHFECIT" cleary meansthat some Ingeri... has made ("fecit") that sword.
Note that the letters are clearer and neater than in many VLFBERHT swords, and that the "+" sign only appears
with the signature of the maker, supporting Anne Stalsberg's hypothesis that this signifies the orgin from an"industrial" enterprise run by a monastery.
But I'm getting ahead of myself. Only time (and looking a the "hidden treasures" in museums) will tell.

2)

Valerie Dawn Hampton: "Viking Age Arms and Armor Originating in the Frankish Kingdom", The Hilltop Review (2011)
Vol. 4, Iss. 2, Article 8.

3)

Simon Coupland: "Carolingian Arms and Armor in the Ninth Century" Viator: Medieval and Renaissance Studies, Vol. 21(1990) (???); on-line via "De Re Militari", Soc. for Medieval Miltary History.

4)Ünsal Yalcin: "Zur Technologie der frühen Eisenverhüttung", Arbeits- und Forschungsberichte zur SÄCHSISCHEN
BODENDENKMALPFLEGE, Band 42 (2000), p. 307 - 382
Andreas Hauptmann und Ünsal Yalcin: " Archäometallurgie der früh- und hochmittelalterlichen Eisenverhüttung im
Vorland der Schwäbischen Alb". In: "Abbau und Verhüttung von Eisenerzen im Vorland der mittleren Schwäbischen Alb",
Forschungen und Berichte zur Vor- und Frühgeschichte in Baden-Württemberg, Band 86 (2003) p. 127 - 158.

5)

Jirí Hošek, Jirí Košta, Patrick Bárta: "THE METALLOGRAPHIC EXAMINATION OF SWORD NO. 438 AS PART OF ASYSTEMATIC SURVEY OF SWORDS FROM THE EARLY MEDIEVAL STRONGHOLD OF MIKULÈICE, CZECHREPUBLIC", Gladius, XXXII (2012) pp. 87 - 102
Patrick Bárta is well-known to us as the master smith who makes all these beautiful replicas of pattern welded swords.

6)

Mikko Moilanen: "ON THE MANUFACTURE OF IRON INLAYS IN SWORD BLADES: AN EXPERIMENTAL STUDY",
Fennoscandia archaeologica XXVI (2009) p. 23 - 38

7)

J. Ypey: "Einige wikingerzeitliche Schwerter aus den Niederlanden", Offa 41 (1984) pp. 213 - 225

Iron, Steel and Swords script - Page 534

11.4.3 Ulfberht Swords
The Basics
Ulfberht Swords are all-steel swords from the Viking era that carry the inscription "Ulfberht" or variants thereof in big
letters on the blade. The letters were mostly made from a thin twisted striped rods and hammered into the blade. The
smith may have chiseled out the contours of the letters before he hammered them in or, more likely, he might havebanged them into the hot blade just so. Consult Mikko Moilanen's article for details.
Besides the Ulfberht swords we also know the "Ingelrii" swords (here is one) and a few more with inscriptions. Ulfberthand Ingelrii appear to be names but there are also (abbreviated) invocations like "in nomine domini" (in the name of theLord). Sometimes something else, including symbols as before, is found on the other side of the blade.
What makes Ulfberht swords so fascinating can be stated in two sentences:
Swords with Ulfbehrt inscriptions were among the very best - and the very worst! They were neither
surpassed nor underpassed by swords forged in the next 5 centuries or so; see the figure in the preceding
sub-chapter.
The top-notch Ulfberht swords were made from (Indian) crucible steel and not from local bloomery steel.
This is fascinating, indeed. So if you want to know all about the topic, my advice is:

Read Alan Williams' book:
The Sword and the Crucible
There is nothing I can state here that goes beyond what he has written on the subject, based on his own
metallographic work. I will therefore give you only a short account of the essentials. I do that by first going throughthe W questions

What are Ulfberht Swords?
Ulfberht swords are swords like these:

Ulfbehrt sword
Source: 1889 drawing from the Norwegian archaeologist Lorange.
Internet; Shrine of Dreams 2012

This is about the best "picture" I could find. The real swords look like this:Iron, Steel and Swords script - Page 535

Ulfbehrt swords
Here are details and more pictures (large format)
Source: Internet at large

The top one is more typical than the other two ones. In other words: the inscription is mostly barely recognizable.
These swords may or may not be "true" ones; I'll get to that.
In what follows I also count swords under "Ulfberht swords" that have a completely garbled inscription like
"VLFBEH" or "VLGPIR".

When do we encounter Ulfberht Swords?
Strangely enough, Alan Williams seems not to supply clear dates. So let's turn to the other big Ulfberht person:
Anne Stalsberg 1).
Anne states "Vlfberht blades are found on handle types from around AD 800 to the 11th. century, possibly also aslate as from the 12th century". Dating was only done by looking a the hilt and that always leaves some uncertainty
because old blades might have been fitted with a new hilt.
Nevertheless, it is likely that Ulfberht swords were made over a time span of up to 300 years and that tells us forsure that it wasn't just one master smith but a lot of smiths; possibly not all of them "masters", who made bladeswith some kind of Ulfberht inscription.

Where did one encounter Ulfberht Swords?
We have two question here: Where did we find Ulfberht swords.and where have they been made?
What we know rather well is where we modern people found them. The following map gives an idea about that.

Iron, Steel and Swords script - Page 536

Where Ulfberht swords were foundSource: Based on work of Michael Müller-Wille

Obviously the about 170 known Ulfberht swords (Anne Stalsberg counted 166 but a few more have been found in themeantime) were mostly found in graves in Scandinavia or in the Baltic region. Actually, 44 out of 166 known Ulfberht
swords have been found in Norway, plus some 2500 normal swords and around 650 saxes form the Viking time.
That does not mean that they were most prominent there, only that it was more likely that they ended up in a grave.
As noted before, burying people with their stuff went out of style in the Frankish empire already in the 8th century
because grave goods were contrary to Christian doctrine (you were supposed to give your precious to the church).
Only the pagan Vikings and other unbelievers in the North / East stuck to the old custom for a while longer.
Anne Stalsberg in her paper gives many maps concerning details1) but the basic fact remains: From the supposedFrankish heartland of advanced sword makings we have only a few finds, mostly from riverbeds, and therefore
without any context. That makes all but certain that only a very small percentage of Ulfberht swords has been found,and that many thousands must have existed 1000 years ago.
Now we know where the swords were found but we still need to consider where the blades were made. We do not worry
about the hilts. These quite likely were made locally (at least the vast majority of the not-so-fancy hilts).
Well, the blades most likely were forged in the Frankian empire for the reasons given before plus the fact that the letters
are not done with runes but in a kind of "Carolingian Minuscle", a script form developed by you guess who. Ulfberht, as aname, can also be traced to the Fankish realm, where it has been recorded in many versions like "Uolfberht" or
Wolfbert". There was no standard spelling by then and Monks (the usual writers) wrote names as they felt was right.
However, as we shall see later, Alan Williams has some doubts about this.

Who was Ulfberht?
What we can state with some certainty is that there was one original "Ulfbehrt" and a lot of copy cats. We don't
know, however, if "Ulfbehrt" was a person or an organization. Even if "Ulfbehrt" was a person, he needn't have been
the master smith who personally made the blades. Just as well he could have been the boss of some enterprisethat produced the swords. Christian Dior did not stitch together the garments sold in his name all by himself either,for example.
Anne Stalberg makes a detailed case for the latter alternative. She goes even further and suggests that Ulfberht wasa Bishop or other high dignitary of the church, and that Ulfberht swords were perhaps made in abbeys ormonasteries. Those were big industrial enterprises in the good old days. We know that Alcuin, Charlemagne’s
Anglo-Saxon adviser, was the abbot of four abbeys which owned more than twenty thousand slaves.

Why?
There is not just one "why" question but several:
1.
2.
3.
4.

Why "signing" a blade at all?
Why not just straight with the name "VLFBERHT" but like this: +VLFBERH+T (the Latin V is our modern U)?
Why are there a lot of variations in the spelling?
Why using coarse iron letters instead of nicely encrusted gold or silver?

The fourth question I have already answered. I only might add here that there is actually an "Ulfberht" with silver
instead of iron letters:

Iron, Steel and Swords script - Page 537

Ulfberht type sword with silver lettering - a fake?
Source: "Neues Museum"; Internet at large; and here

It appears that the "letters" are made from silver, "damascened" into grooves cut with a chisel. Then it would be an
obvious fake for an illiterate customer. However, as Ingo Petri assured me, who had the opportunity to analyze thissword in some detail, this is a "true" +VLFBERH+T sword. An over-eager custodian of the museum, some time ago,
"painted" some silver color over the insets he could recognize, muddling up the lettering and the appearance in thisprocess.
VLFBERHT Variants and Blade Quality
Let's give some thought to why one would want to have some symbols or signatures on a sword blade. Reasons mightbe:
1. Showing off. That was an important reason for pattern welding, after all. More modern swords often have highly
embellished blades for that reason. However, the always visible hilt is a better object for showing off than theusually covered blade.
2. Magic. Some special signs or symbols, like a Victoria or a Mars on Roman swords, might bring luck. Invocationsor quotes from Holy books became popular much later too, for essentially the same reason.
3. Identifying the owner or the organization. The blade is the important part of a "working" sword and thus a better
place for an indentifier than the hilt.
4. Identifying the maker. That only makes sense if the sword is not a standard issue, run-of-the-mill weapon. For
reasons given before, that necessitates to make the inscription on the blade during forging. It also necessitates
to use iron / steel letters and to make them rather large.
5. Impressing or better scaring your opponent in a sword fight. That necessitates that the inscription is as large as
possible and well visible. Since those guys were typically illiterate and had no time to spell out a word during asword fight anyway, its general appearance should be instantaneously recognizable
From this and all I have written before, it is clear that points 4 and 5 apply to Ulfberht swords. Point 3 might come inwhen one looks at the backside of Ulfberht swords where often only symbols are displayed.
Alan Williams set out to investigate as many as possible Ulfberht swords as closely as possible. In his book hedescribes 55 swords in some detail. While each sword is unique, it can be assigned to one of five quality groups,
essentially determined by the carbon content of the steel, which are:
1. Blade made from (one?) piece of hypereutectoid steel, i.e. the carbon concentration is larger than 0.8 %.
2. Blade made from eutectoid steel (carbon concentration about 0.8 %).
3. Hardened steel (around 0.4 % carbon) for the edges with a softer core.
4. Unhardened steel (around 0.4 % carbon) for the edges with a (wrought) iron core.
5. Wrought iron (less that 0.2 % carbon) throughout.
That is the "grade" scale for the 10th century swords that I have referred to in a preceding figure.
Grade 1 swords are supposed to be top-notch swords, far better than anything made before or after for hundreds ofyears. That is no just due to hypereutectoid steel as material but also to the observation that this steel was rather
slag-free and forged in the "right" way. Grade 1 Ulfberht swords, in other words, were made from crucible steel bysomeone who knew how to work with this difficult material. I'll come to that.
Grade 5 swords were extremely bad; worse that anything made in later centuries and, with some restrictions, alsoearlier centuries
Alan made two sensational discoveries:
1. Crucible steel was used for some - the grade 1 - Ulfbehrt swords. That is a sensational discovery - provided it istrue. I have no reason at all to doubt Alan's analysis but as a scientist I only accept sensational results if there isan independend confirmation.
2. The quality is tied to the accuracy in spelling "Ulfberht". The correct rendering is: +VLFBERH+T, and the twocrosses are importantIron, Steel and Swords script - Page 538

2.
The following table supplies some data and examples from Alan Williams' and Anne Stalsberg's work. "Early","Middle" and "Late" mean, according to Anne::
Early Viking Age; sword blades with their main existence in the 9th. century.
Middle Viking Age; swords with their main existence in the 10th. century.
Late Viking Age; swords with their main existence in first half of the 10th. century - 11th. century.
Anne's time ranges are a tad unclear in the middle but the general time sequence is clear.
Alan Williams' Table
Grade

No
of
swordsSpelling
examples1

92

Anne Stalsberg's table
Spelling

Early

MiddleLate

6:+VLFBERH+T
3: Close+VLFBERH+T

11
25%

20
45%

1
30%

5

2:
+VLFBERH+T
3: close,
missing cross+VLFBERHT+

15
68%

4
18%

3
14%

3

14

+VLFBERH,
VLFBERN+

VLFBERH+T

1-2

0

4-3

4

16

Many wrong+ VLFBERH-|variants,
Te.g.VLFBER++,VLFBPH T,
and completely
garbled

4
44%

4
44%

1
12%

5

11

Very wrong("VLEHBA"),
non-latin letters,
symbols
instead ofletters

6
42%

4
29%

4
29%

+VLEBERHIT+VLFBEHT++VLFBERH*

Anne Stalsberg distinguishes between 7 spelling variants (including "non-definable") for the Ulfberht signature andthe backside symbols but doesn't tie that to blade quality. The table above with only 5 variants does not include the"undefinables" and a group with only 2 undatable specimen.
She does interpret the crosses as part of the signature of church chieftains. Indeed, some Bishops or other highchurch officials still put a cross in front of their signature up to this very day.
Taking everything together, one possible scenario emerges: Somehow crucible steel from the "East" must have made it
to the North, and some sword smiths figured out or learned from others how one had to deal with the stuff. Swords
superior to anything known so far were made from the crucible steel and became an expensive high-prestige weapon fora few.
It goes without saying that as soon as "true" Ulfberht swords acquired some fame, Ulfberht fakes were produced allover the place. The fakers made an all-steel blade and added an Ulfberht inscription. Since they probably had never seen
an original, were illiterate anyway, and might have been taken in by an inscription that was already a fake, the wholething deteriorated. In the end only meaningless symbols were put on a blade.
The Copenhagen museum provides a nice example for not paying close attention while faking. Its museum store offers
Ulfberht replicas that look like this:+ ULFBERHT + instead of +VLFBERH+T(Not to mention that the "Times" font with serifs (look it up)
hadn't been invented then)
Source: Photographed in the Copenhagen museum

Iron, Steel and Swords script - Page 539

If the museum couldn't get it right, you can't blame ancient black smiths for goofing.
Now would be a good moment to read up the essentials of crucible steel. Here I will only refresh your memory by
enumerating the crucial points:
1. Crucible steel was molten once and thus does not contain slag inclusions. That is a huge advantage relative to
bloomery steel.
2. Crucible steel is always hypereutectoid steel with a carbon concentration typically well above 1 %. It is thus
perfectly brittle and useless, except if "tricks" like spheroidizing the cementite are used during forging.
3. After the cementite is spheroidized you must forge the steel at low temperatures. If you ever exceed the transition
temperature to austenite around 730 o C (1346 oF), most of the cementite dissolves and upon cooling you areback to the brittle stuff.
4. Wootz blades made from crucible steel employ very special forging technique. The cementite must be kept fromlining the grain boundaries (as it does here) and induced to "spheroidize" (as shown here). This can be achievedin various ways.
I don't think that a Northern smith could figure this out all by himself. In fact, the metallographic analysis does showthat some if not all "true" Ulfberht swords did not consist of the good spheroidized cementite but contained "bad"cementite encased pearlite grains and cementite needles as shown below for the Stuttgart sword:

Microstructure of "Stuttgart" Ulfberht sword
Source: One of Alan Wiiliams publications (ca. 2005) without proper reference in the Net.

What we see are grains completely encased in cementite plus some cementite needles inside the grains. It does
look a lot like the structure of crucible steel right after solidification.
Of course, one picture does not prove that the whole sword had a microstructure like this. It is likely, however, andwould made for a rather brittle sword. What that means is that the sword would fracture as soon as the elastic limit
is reached. However, since there are no slag inclusions, the elastic limit is at a relatively high level and the sword
might still have been better than the bloomery steel swords of the time. Or maybe not; it is an open question. Its
broken end may indicate that the blade broke because it was brittle.
This sword thus is not comparable to the "wootz" blades of a later time.
One might conclude that exporting crucible steel to the North made only sense together with a manual of how to work it,
possibly in the form of a slave. However, the makers and users of crucible steel might not have figured out the best way
of forging it at the Viking time either.
So which of the cultures / empires empires around the Frankish empire or the Viking infested Northern area could have
traded crucible steel? If you look at this map long enough and then compare it to this map, two possibilities emerge:
1. We know that the Vikings got down the river Dnieper all the way to the Black Sea and possibly beyond quite
early. One Viking actually scratched a graffiti (in runes) into a marble balustrade in the Hagia Sophia in Istanbul(or Byzanz as it was called then). From there it is not so far to sources of crucible steel, and they might wellhave taken some back. They certainly took silver coins from the Samanid empire (today's Iran) all the way backto what now is Sveden, where plenty of these coins have been found.
In this case the "true" crucible steel Ulfberht's might have been forged in Eastern Europe and not somewhere in
the Frankish Rhine area. Alan Williams seems to favor this scenario.

Viking graffiti in the Hagia Sophia
Partially unreadable but something like: "Haludan was here" (8th century)
Source: Photographed in the Hagia Sopia
Iron, Steel and Swords script - Page 540

The Franks had many dealings - bloody and otherwise - with the "Moors" in Spain. The Moors were themedieval Muslims that inhabited large parts of what is now Spain. They were in turn connected (bloodily andotherwise) to the "Caliphat" of the Abbasides that ruled much of North Africa, Arabia, the Middle East, Iranand so on - look at this map. There was a lot of trade and crucible steel may well have made it to theFrankish sword forging centers along the Rhine.
Is it answer 1 or answer 2? It is too early to tell. While I have no reason to doubt Alan Willams' pronouncement thatthe "original" Ulberht swords were made from crucible steel, it is good scientific practice to wait for an independentconfirmation before something is considered certain.
Since only a few of all the Ulfberht swords were made from crucible steel, we might surmise that the supply was limited
and probably only available for a short period of time. While many efforts to emulate the "true" Ulfberht swords failed,some quite miserably, it might have triggered a new look into making iron and steel in bloomeries, leading slowly toprogress in the technology.
Is It True?
Much has been made about the "Super" weapons of the Vikings in the form of the "true" Ulfberth sword, made from"wootz" steel. Some quotes:
Although some have been identified as sloppy counterfeits, the real thing was obviously a fabulous piece of work.
They were stable, weightless and particularly lethal.
Web: "Medieval Histories"
Ganz Europa schätzte die Superwaffe. Die Klingen der sogenannten Ulfberht-Schwerter zählten vor tausend
Jahren zur Hochtechnologie der Rüstungsmanufakturen des fränkischen Reichs. Das Kampfgerät war stabil,besonders leicht und damit hocheffizient.
Süddeutsche Zeitung, July 30th, 2014.
The Vikings were among the fiercest warriors of all time. Yet only a select few carried the ultimate weapon of
their era: they feared Ulfberht sword. Fashioned using a process that would remain unknown to the Vikings' rivals
for centuries, the Ulfberht was a revolutionary high-tech tool as well as a work of art. Considered one of thegreatest swords ever made, it remains a fearsome weapon more than a millennium after it last saw battle.
From the NOVA broadcast, 2012.
As I'm writing this, the "Süddeutsche Zeitung", one of Germany's leading daily newspapers, has an Ulfberht on page 1,
pointing to a major article in its science part. In the (surprisingly good) article some doubts are expressed about the"super steel" from the East" hypothesis. The "Süddeutsche" is already quoted above. In its July 30th, 2014 article, withthe heading: "Ulfberht"-Swords - wonder weapons from monasteries", the paper is all stricken with the super weapon.
So is that true? The claims to the superior qualities certainly are not! The weight and "feel" of the Ulfberht swords
was no different from that of others made to corresponding dimensions, of course. A sloppy wrought iron sword wasjust as lethal as a steel sword if used against unprotected civilians. One of the greatest swords ever made? How thehell can those guys tell this from a micrograph showing the structure of a tiny part of the blade?
And be aware of a little detail: While true Ulfberht's might have been made from crucible steel, they are not akin to
the famous "wootz" blades that show a "water pattern" and were also made from crucible steel.
On a more serious note I need to mention that Alan Williams' insights are not universally accepted by all and sundry.
This is especially true for claims that Alan did not even make himself but which "evolved" somehow in the media and infollow-up work.
Here are my comments on some topics that are maybe not all that clear.

1. Is "+VLFBERH+T" the original correct way of the inscriptions followed (later) by "+VLFBERHT+" and all
the other variants?
Anne Stalsberg disagrees. As the table above clearly shows, 68% of the +VLFBERHT+ variants are dated to theearly Viking period - but only 25 % of the +VLFBERH+T's.
Since +VLFBERHT+ makes a lot more sense than +VLFBERH+T, one might speculate that the latter resulted froma mix-up of a cross and a T / t.

2. The "originals" - whichever they are - were made from crucible steel that originated somewhere in "India" orthereabout!
There is no reason to doubt Alan Willams' analysis. The pictures in his book support his view (of course!). However,
Alan only shows that a few tiny areas of the blades consist of hypereutectoid high-carbon steel with no or little slag
inclusions.
There is no reason to accept his analysis as eternal truth either as long as there is no independent metallurgicalanalysis done by other researcher that corroborate Alan's work. Moreover, it is all but sure that hypereutectoid highcarbons steel have been made in Europe, too, albeit in a bloomery and not in a crucible. What this means is that
small sword fragments that look a lot like crucible steel Ulfberht's under the microscope may actually be European
bloomery-steel swords. More to that in what follows.

Iron, Steel and Swords script - Page 541

3. Are swords made from crucible steel always much better than swords made from bloomery steel?
This is certainly wrong. Some confusion comes from equating crucible steel swords with "wootz" swords, thefamous (and considerably later) swords with a "water pattern" on their blade. While all "wootz" blades were madefrom crucible steel, most blades made from crucible steel are not "wootz". The first and decisive difference is that inwootz blades the cementite has been spheroidized (=balled up) in a tricky process, while in regular crucible steel itlines the grain boundaries and extends into the grains as needles. Just as in the "Stuttgart" Ulfberht sword shown
above and in others according to the (not very good) pictures in Alan Williams' book.
Swords with such a structure must have been rather hard but also quite brittle. If some phosphorous was involved(often the case with crucible steel), they were also prone to cold shortness. It is hard to judge how well they would
hold up in a fight with a capable but conventionally armored opponent, but is is almost certain that they could nothave been a lot better than a well-made bloomery steel sword with a hardened edge like the Moravian swords - ifthey were better at all!
Alan's claim that even "an imperfectly homogenised crucible steel would have been considerably better than the
fragments of bloomery steel" (page 25) is unsubstantiated, to say it politely.
4. The crucible steel for the "true" Ulfberht's came from India or some related place via trade routes runningalong major rivers in the East (today's Russia) and the Ulfberth's were forged somewhere in the East too.
True?
The first part is not unlikely. A lot of oriental stuff, in particular coins, did make it this way to the far North. However,here is another possibility, too. The Frankish empire had close relations with the "Caliphat" in Spain and in otherplaces. While not much seems to be known about the steel type used by Muslim warriors in Spain, it is not unlikelythat they had access to crucible steel blades and crucible steel. From there it could have made it to Frankishsmiths. This is just a possibility with no direct proof at present. But this hypothesis has not been disproved either.

5. Ulfberht is the name of the smith who made the first and "true" Ulfberht's some time around 850. A lotof other smiths made inferior forgeries for 200+ years to come. True?
This is rather unlikely. It is all but certain that most of the "true" +VLFBERH+T (or is it +VLFBERHT+; see above)
swords have not been found, and that the number of all the Ulfberht swords made exceeds the capacity of one smith
by far. I would rather go with Anne Stalsberg's hypothesis that Ulfberht was for swords what Enzo Anselmo Ferrari(1898 - 1988) was for Ferrari's. I believe I need not explain to you guys out there, including the part with cheap andnot-so-cheap copies.
The Ulfberht manufacturing business might well have taken place in monasteries as Anne supposes. They simply
were the major "industrial" centers in the Viking time period, just look at their size of the work force!
All things considered, it is perfectly reasonable to doubt the major thesis that "true" Ulfberht's were made form Indian
crucible steel. If stripped down to the essentials, Alan Williams bases his claim on just two points: A very high-carbon
steel with no slag inclusions can only be crucible steel. This is true but only if both conditions are met simultaneously
and for a large piece of the material. In particular, just having a very high-carbon steel doesn't prove anything. It is rather
clear by now that this kind of steel was also produced in Europe around 800 AD and later. While European UHCS wasnever completely slag-free, it is not impossible to find areas in a blade where slag inclusions are not obvious.
Buchwald's two books contain a lot of structural pictures that do not show obvious slag, for example 2. Since Alan, tothe best of my knowledge, has not shown that large areas of the swords investigate were free of slag, there are some
general doubts as well.
Personally, I consider it absolutely possible that high-carbon steel with very little slag inclusions has been madeinside the Frankish empire or somewhere else in Europe. If you look at the new and rather breathtaking findings ofthe iron and steel smelting development on the "Schwäbische Alb" (the old haunts of the Alemanni) between 500
AD and 1100 AD, I would not be surprised to learn that on occasion they made the kind of steel typically associatedwith crucible steel. That is pure speculation, though.
That (probably) normal Frankish swords contemporary to the Ulfberht's show (in parts) a microstructure that looks
very much like that of the Stuttgart Ulfberht is a fact, however.
For the sake of the argument, let's assume that very high carbon steel from bloomeries was available. In contrast totrue crucible steel, however, it must be expected to contain some slag. The amounts might have been small,
however, and so much broken up during faggoting, that the slag inclusion are not always visible in typicalmicrographs. Here are examples:

Iron, Steel and Swords script - Page 542

Upper left: Microstructure of Stuttgart Ulfberht (supposedly crucible steel).
Upper right: Frankish sword made from bloomery steel.
Bottom: Svedish axe blade; around 1000 AD. Pearlitic grains enveloped in cementite; i.e.
hypereutectoid steel. No visible slag (Buchwald; p. 308)
Large picture of hypereutectoid bloomery steel with no visible slag
More pictures of European hypereutectoid bloomery steel
In any case, the arguments for a Frankish origin of the "true" Ulfberht swords, though not irreproachable, are still far
stronger than the arguments in favor of an Eastern origin. Very recently (2014), a new "Ulfberht" has been found in theriver Weser, North Germany. There was some lead in its pommel that could be traced to the "Rheinisches
Schiefergebirge", not far from the old and powerful monasteries of Fulda and Lorsch. While that finding doesn't proveanything it does make the Frankish origin of Ulfbehrt's a bit more likely.
Alfred Geibig, known to us from before, the author of a 1991 book about swords of the middle ages, and certainly one of
the top German authorities on swords, is also sceptical according to the "Süddeutsche ", and considers a local origin ofhigh carbon steel as possible. Robert Lehmann from the University Hannover who analyzed the Weser sword (and foundthe lead connection mentioned above), based on his (not yet published) analysis also votes for a local origin of the steel.
Add to this that at least one of his analysis is most likely wrong. The Hamburg Ulfberht sword, while a true Ulfberht
and counted among the crucible steel Ulfberht's by Alan Williams, shows clear "striatons" along its edges. So it
was most likely made from fagotted and piled bloomery steel. Judge for yourself by contemplating the picture below
and this picture.

Iron, Steel and Swords script - Page 543

Hamburg's Ulfbehrt sword with striated edges.
Large size
If the sword would have been made from crucible steel, there would not have been a reason for faggoting and piling.
The new "Ulfberht" from the Weser also shows some striations in an corroded edge part, possibly also indicating
faggoted steel.
Nothing helps. If we want to find out what really happened in the Viking era to the iron and steel industry, we need far
more metallographic investigations of regular swords, and in particular a clearer picture of the progress made in smelting
technologies. It also wouldn't hurt to know more about the kind of swords that the Islamic Moors carried in Spain, and if
and how technology transfer took place at the border to the Christian empires.
And so on. I doubt very much that the last word has already been spoken with regard to Viking era swords including
Ulfberht's.

1)

Anne Stalsberg (Museum of Natural History and Archaeology, The Norwegian University of Technology and Science,
Trondheim, Norway): "The Vlfberht sword blades reevaluated", 2008 Internet source: Jenny-rita.org., Stavanger.

2)

We find many pictures in Buchwald's book that do not show obvious slag. That does not mean that the steel was slagfree, only that the area in question was slag-free or at least did not contain slag particles large enough to berecognizable. Some examples :of such "slagless" steel are:
Buchwald I: Figs.: 118, parts of 122, 174, 245, 270, 330, 334
Buchwald II: Figs.: 12 (most parts), 16, 17, 53, 95, 129 (parts), 259, 304, 306, 356, 376.
To be sure, there are more pictures that clearly do show slag inclusions.

Iron, Steel and Swords script - Page 544

11.5 Wootz Swords

11.5.1 The Winner is....
What It's All About
Wootz swords in my terminology are swords that were
1. made from crucible steel, and2. show a nice "water" pattern on the blade.
The great Verhoeven - Wadsworth Jousting Tournament was all about how to make wootz blades. So who won thetournament? Before I tell you, I need to ask if you remember what, exactly, the contestants fought for? I thought so. One
tends to forget what was so important to merit a life-and-death fight if one doesn't watch all the time. Why, exactly, did
the Church burn Giordano Bruno some time ago? Which church?
So let's recall what it is all about. The short version is here.

Still at it.
Source: Sir Thomas Holme's Book of Arms; ca. 1440

The big question was (and is):What does it take to produce a nicewootz pattern on a piece of steel like a sword.
The way I put it the emphasize is on "nice", and that is not a good scientific word because it is hard to attach anumber measuring the degree of nicety. It is just as hard to define what separates a nice wootz pattern from a runof-the-mill one, as it is to define what separates pornography from art. Yet you just know it when you see it.
Below are nice wootz patterns; here are a few more

Nice wootz patterns
Note: The cementite-rich regions are white here
Source: Commercials for not-so-old wootz swords (18th century or
younger) you could buy from antique dealers in 2014

You only see the pattern after the (polished) blade has been properly etched.
True connoisseurs have with little success tried to classify "nice" in more detail; consult theillustration module if you must know. In essence one distinguishes:
Stripe pattern
Water pattern
Wave pattern
Net pattern
Wood Grain pattern or Mottled pattern
Step pattern or Mohammed's ladder (kirk nardeban) with or without "roses".
Iron, Steel and Swords script - Page 545

Illustr.
ModuleWootz
PatternsMy own definition of "nice pattern" is simple (and rather useless): A "nice pattern" is basedon a structure that would allow, in principle, to produce a "kirk nardeban" or rose pattern.
In the crucible steel chapter I have given you already a lot of information about wootz steel; now is a good time to refresh
your memory.
Having you back, I propose that you now make a wootz sword with a nice pattern. You started out as a smith already inchapter 2, after all. By now you are a smith in chapter 11 and you have learnt a lot about iron and steel in the meantime.
Let's see if all that knowledge allows you to do the job. It shouldn't be all that difficult because several modern smiths
are at it right now - and some have succeeded. I'm going to help a bit, though.
Le's start by working our way back and see if we can figure out what it takes to make a wootz sword. Generating theprocess recipe will also bring out the still open questions and allow us to focus on what, exactly, all the jousting isabout.
So what do we know "for sure" about the making of wootz swords?
First of all we do know what causes the pattern, the interlaced dark and bright regions on the blade. The "color"reflects the difference in the cementite concentration or, being a bit more precise, the difference in the concentrationof largish cementite precipitates. You must etch your blade a bit to make this difference visible but this is arelatively trivial (if sometimes frustrating) part of the recipe and we will not discus the various techniques for that.
Looking at the blades above with a microscope at medium magnification (around 100x) will give pictures like these:

Black cementite particles in a (pearlite?) matrix
Note: The cementite is black here.
Source Verhoeven 2002

So let's ask a simple first question. We know that one needs high-carbon steel for wootz patterns. So just how muchcarbon do we need to form sufficient cementite for forming the pattern?
Let's start by considering how much cementite is actually there "to see" in a steel sample with, to make it easy,
1 wt % carbon. A simple question but the answer needs a bit of thought.
From Carbon to Cementite
In order to keep things simple we envision a 100 g (or 100 pound or 100 ton) cube of carbon steel. If 1 % of the weightcomes from the carbon in there, we have 99 grams of iron and 1 gram of carbon, obviously.
The carbon will eventually turn into cementite, Fe3C. Any carbon atom thus takes three iron atoms away, and thatmeans you have less iron now. I know it is a bit confusing because you still have the same number of iron atoms in the
cube. But an iron atom contained in cementite is not part of an iron crystal (ferrite at room temperature) anymore, justas an oxygen atom in a water molecule is not part of the air anymore.
Now to the big question: How much room does the cementite occupy in our cube? And what could we "see" by looking
at the cube? Simple questions but the answers take quite a bit of thought.
We need to keep track of atom counts now and in order to do that we first need to go to atomic concentrations. I gave
you a whole module dealing with that, and you can look up there how it is done. Or just believe me:
1 wt% of carbon corresponds to 4.81 at% of carbon.
That means that from all the atoms in our 100 grams of steel 4.81 % are carbon atoms, and 95.19 % are iron atoms.
Now imagine a smaller cube containing 9.519 iron atoms and and 481 carbon atoms and you get the right relation.
Altogether we have 9.519 + 481=10.000 atoms (surprise?).
Now we form cementite. Our 481 carbon atoms will need 3 × 481=1443 iron atoms to form one molecule ofcementite, Fe3C. That means we have only 9.519 - 1443=8.076 iron atoms left for being iron. Relative to the 10.000
atoms we started with this equals 80.76 at% and the rest, 19.24 % of all the atoms in the cube, are now in the
cementite! That's what just 1 wt % of carbon will do! With 6.7 wt% carbon only cementite would be left
I'll illustrate that with a very simple picture:4)

Iron, Steel and Swords script - Page 546

Visualizing percentages in concentrations
The small blue cubes in the upper part of the picture just visualize the percentages.
The big cube demonstrates what you could get by breaking up the solid block of cementite. First look a the righthand side. The grey part corresponds to the volume the cementite takes up if it would be in one block. Now consider
that block as being built up by rods, e.g. three abreast as shown on top. Now break one rod into cubes and justleave every other cube in place. Than you can pack six rows of interrupted cubes into your crystal replacing thethree full rods shown. Continue on the next level and you have the structure on the left-hand side of the big cube
above.
What seems to become clear is that you can make a lot of rather big cementite particles this way, or a hell of a lot ofsmaller ones - from just 1 wt% of carbon! With some special arrangement of all these precipitates you should be able toproduce a pattern.

Too bad that this is wrong!
You don't see it? Then look at the phase diagram. Or just believe me when I remind you that with the first 0.76 wt%
of carbon you simply form pearlite . A cube of just 0,76 wt% steel would simply consist of pearlite grains, i.e. grains"filled" with the by now well-known "zebra" structure. Of course, part of the "zebra" are the cementite lamellae but
everything is so small (around or below the 1 µm region) that you simply cannot see any pattern on a pearlite
surface, not to mention a "nice" one. The cementite in the pearlite is effectively invisible to us and the only opticaleffect is the "pearl-like luster".
In our 1 wt% example we have only 0.24 wt% carbon left to form some extra cementite but that might not be enough forforming visible cementite.
For the formation of a nice wootz pattern we need cementite in excess of the one in the pearlite, and this means that weneed to go well above the eutectoid 0.76 wt% carbon concentration. So let's take 1.76 wt% and we are right back to the
picture above (with the "blue" in the cube now denoting pearlite).
Incidentally, that's a typical carbon concentration for crucible steel and wootz swords.

Iron, Steel and Swords script - Page 547

Getting High Carbon SteelNow we know what we need: a sufficient amount of about 2 wt% carbon steel, i.e. ultra-high carbon steel (UHCS).
Where should you look for that before 1800 or so? It's a tough assignment - even for the time traveler who knows allabout steel. For an ancient European smith it was almost impossible to get UHCS. If you followed me you know by now
that all the bloomeries of old did not just produce wrought iron but all kinds of carbon (and phosphorous) steel, up to andincluding cast iron. However, 2 wt% of carbon is difficult to make in a bloomery. It is too much carbon for a regular solidstate bloomery process (look at this picture to refresh your memory). If you would try to smelt 2 % C UHCS in abloomery, you would quite likely run into the other extreme and end up with cast iron, getting carbon concentrations thatare too large.
Europeans thus couldn't easily have forged wootz swords - they lacked the raw material.
Smart Indians or Iranians, on the other hand, employed a crucible process after smelting raw iron / steel in a bloomery
and made UHCS conscientiously. No, they did not! They did not produce steel with about 2 wt% carbon intentionally ,they produced it by default. They would for sure have preferred to make 0.7 wt% steel but couldn't because their process
was temperature limited.
If everything worked, the resulting wootz or bulat cake was liquid once with a bit of liquid slag on top. Cooling downsolidified the steel without incorporating the slag. This made crucible steel superior to bloomery steel with respect toslag inclusions.
Of course, crucible steel was not pure high-carbon steel and it was not always "perfect" either. It contained theusual impurities, e.g. phosphorous, depending on what was contained in the ingredients. There seems to be someevidence that the stuff wasn't always completely molten either, just what one would suspect. The resulting cakethen was rather inhomogeneous.
But let's go on. Let's assume that you, the ancient smith, did get into possession of a good wootz cake with therequired 2 wt% carbon or so, and not too much dirt and other problems. What's next?
Shaping the Cementite
You now have a 2 wt% carbon steel that will produce sufficient cementite for pattern formation. But you, like all of us,
know that during cooling the cementite forming first (the "primary cementite") will tend to line the grain boundaries , andthat the resulting steel is completely brittle and thus almost useless for swords - but not for many other things likepunches or dies for wire drawing. I'm saying "almost" useless since the famed Ulfberht swords, if indeed made from
crucible steel, would fall into that category. Why they might have been perceived as very good is not so clear; I havealready made some comments to that.
Somebody, sometime (maybe around 500 AD) and somewhere (in India or thereabouts) ran across the first major trickthat needs to be employed to avoid this:Ball up (spheroidize) your cementite!
Produce little "spheres" or just pebble-like particles or precipitates instead of shells around grains, long needles(look up "Widmanstätten") or anything spreading in some direction. The process for doing this is called"spheroidization ".
I already gave you a list of how that can be done. Read up on it; here I only emphasize the major points:
Since we do not want cementite at the grain boundaries, it is essential to nucleate the stuff inside the grains.
Having very strong carbide-forming elements like (Nb), titanium (Ti) and vanadium (V) around is certainly helpful oreven necessary. Metal carbides will form first and then act as nuclei for cementite precipitation.
Banging with a hammer or just deforming heavily helps because it mechanically breaks up large cementite
particles, making it easier to form many "spheres" out of one large sheet or needle.
Cycling at temperatures around the A1 temperature of 727 oC (1341 oF) helps. If done right it will coarsen the
cementite particle and sharpen the distribution; see below. The smith does both when he forges a blade. Heat itup, bang it, cooling, stop. Heat it up, .... A tricky smith might even use more heats then necessary to makemany cycles.
Whatever you did to get your cementite to ball up - after that has happened the second major trick comes into play:

Forge at low temperatures!
You must never ever again raise the temperature to well above the A1 temperature of 727 oC (1341 oF) where ferritechanges to austenite! If you do, a lot of the spheroidized cementite will dissolve and chances are that it precipitatesin unwanted shapes during cooling. A little bit above A1 for a short time - OK. But never a lot above A1 or for longtimes!
Iron, Steel and Swords script - Page 548

This goes against all normal
principles of forging!
The smith just must be acutely aware of all of that. An ancient European smith who by accident got hold of somecrucible steel was not likely to find that out by playing around a bit with the stuff. Western 18th and 19th century smiths
indeed didn't get it according to some sources.
Since this is not something you find out yourself, getting in possession of some crucible steel just couldn't do muchgood in the "West".
In contrast, the ancient smiths in India and Persia knew what to do 1600 years or so ago. They did make blades from
crucible UHCS that contain spheroidized cementite and are no longer brittle. The link shows what that looks like.
Did you believe that? You sucker! The link shows what modern scientists ( O. D. Sherby and J. Wadsworth, actually)
can do with modern methods and knowledge. The theory, though a bit involved, is also well-known by now 1), not tomention that times, temperatures and impurity content are known and controlled.
The question is: Did the really old smiths working with crucible steel produce spheroidized cementite?
I have yet to see a micrograph of old crucible steel that shows spheroidized cementite. In contrast, I (and you) haveseen structures that show what we want to avoid: grain boundaries solidly encased in cementite. Just look at the
picture of the "Stuttgart" Ulfberht sword that as been made from crucible steel according to Alan Williams.
"But what about the pictures up there", you might say. "Don't they show spheroidized cementite in bands?" Yes,
they do. But these pictures are from much later wootz blades with a pattern and we aren't there yet. Moreover, thesteel has been etched in a way to bring out the wootz pattern and not to show the structure. You just do not know
in these cases what you do not see because of the undefined etching.
What we would need to see at this stage are metallographic examinations of crucible steel blades that do not show awater pattern. Alan Williams in his book about Ulfberht swords supplies quite a few pictures of that - and not one ofthese pictures shows good spheroidization!
There are certainly more metallographic investigations into the structure of old crucible steel, and I do not know them all.
From what I know I show you one example:

Phosphorous-lean area

Phosphorous-rich
area

Cementite (white) in (forged) crucible steel
Source: M. R. Barnett et al. 2)

The sample origin is a bit unclear. It's probably 19th or 18th century, it is certainly not ancient. We see several
remarkable things:
There is good spheroidization - but only in parts of the sample that contains an appreciable phosphorus
concentration. This illustrates that nucleation and thus trace impurities might play a major role in crucible steel
processing.
The crucible steel people obviously did have a phosphorous problem like everybody else; at least on occasion.
The phosphorous is inhomogeneously distributed. There are obviously limits to uniformity even in formerly liquid
steel.
At this point we simply learn that not all crucible steel swords are born equal. If everything worked and thecementite is nicely spheroidized everywhere, these blades were very hard throughout but not brittle. But rather brittle
blades must have been made, too, as well as blades given to cold shortness, inhomogeneous blades and whateverelse results if not everything is "just right" in the production of the blade.
The picture below shows a small section of an otherwise magnificent wootz tulwar where the pattern is not present
in parts:

Iron, Steel and Swords script - Page 549

"Defective" area in a wootz tulwar
Source. Tulwar restored and photographed by me

Did something go wrong during the forging of this wootz blade? Well, yes - but in a peculiar way:

Surprise!
This blade is actually "faked wootz"

SpecialModuleFake Wootz?

As I learned just recently (fall 2017), this blade has a core of regular non-wootz steel with a thin layer of wootz steellaminated to both sides. In the "defective" area, this thin wootz layer has been polished off. More to that in the link
given above.
Now let's assume that you managed to forge a blade that contains nicely spheroidized cementite. Now we come to the
key question:

Would your blade show a pattern?
If it does, would it be a nice pattern?
A pattern or no pattern? This is the question. Then we have follow-up questions:
Could a pattern result without you, the smith, being aware of that?
If a pattern does result: could you have prevented it?
If a pattern does not result: is there anything that you, the smith could do to generate one?
If a pattern does result but it isn't "nice": is there anything you can do to change that?
In the link you find a lively discussion among real smiths where some of these questions are addressed. In what
follows I will spend quite some time on this topic, so be patient.
Forming a Pattern You Can See - Some Basics
We want to make a nice clearly visible pattern. The first question in this context is: What can you see and what is
invisible? Not an easy question. With proper light, you can see a single hair. A hair is about 30 µm (=0.03 mm) thick but
pretty long. Could you see a 30 µm diameter cementite sphere, cut in half and embedded in featureless "polished" iron?
(Left hand picture below). Probably just so, as a tiny speck under certain good illumination condition. Illumination isimportant; at night you can't see all that much after all. So let's assume that you have always the best illumination tokeep the subject simple.

Iron, Steel and Swords script - Page 550

Could you see a lot of (cut in half) 30 µm or so cementite spheres that are uniformly distributed in a (polished) ironmatrix? (Middle picture below)
No, you can't. You cannot "see" all the individual particles. A polished sample after etching might look darker andbit motley compared to a pure iron sample - but that's it.
You only "see" something if the cementite is distributed in a non-uniform way in some kind of banding (right hand
picture below).
Here is my not very good attempt to illustrate all of this in a very schematic way:"Seeing" cementite
Note that we need at least four parameters to describe the banded structure in the upper right-hand corner:
Size distribution of the cementite particles. At the minimum we need the average size and the "standard
deviation", a measure of the spread in sizes.
Average distance between the particles in a band.
Average distance between bands.
It is easy to come up with more variables but let's stay simple. Now ask yourself. What is going to happen to thevisibility of the pattern if I change one of those parameters? The extremes are clear. Make the average diameter ofthe particles or the distance between bands very small and there goes your visibility. Otherwise it is not so simple,
not to mention that the etching and the lighting also come into play.
Are there any rules of thumb for those parameters? Yes - all you need to do is to look at the pictures above or the oneright below. They show microscopic cementite particle distributions that do produce a clear pattern:

Parameters for visible cementite bands
Source: Verhoeven, Pendray 3)

We "see" that a distance between the bands of around 50 µm on the blade is fine, and that particle sizes around 5µm are fine, too - provided there are a lot! Average distances between particles in a band should obviously be small,well below 5 µm. In three dimensions we have parallel sheets or bands of cementite particles, of course. Since thesurface intersects those bands at a small angle, the distance between the bands will be considerably larger there;
look at the picture below or this module to see that.
Now we have a good idea of what we need to make:

Iron, Steel and Swords script - Page 551

Sheets (or bands) of cementite particles with the parameters fromabove that are intersected by the blade surface.
We knew that all along, of course. But now we know also some numbers - and that is a very valuable asset.
We know now, for example, that we need not only to spheroidize our cementite, we need to do it in a way where we geta high density of particles with a diameter of several µm. If we do that and distribute these particles uniformly in theblade, we will not get a visible pattern. If we distribute them in well-defined layers about 50 µm apart, we will be able toproduce nice patterns on the blade.
How about something in between? Not a uniform distribution, but no well-defined layered structure either? That mightalso produce a pattern - but not necessarily a "nice" one!
We are getting closer to what the fight is all about. Simplified, the Wadsworth group maintains that it is relatively
easy to get patterns with just about any UHCS steel, including old-fashioned crucible steel, by following a few
simple rules:
Cool slowly, producing a relatively coarse grain structure and possibly some
Widmanstätten cementite structure.
Break up the cementite by forging; heavy forging produces finer structures.
Reheat somewhat, inducing spheroidization.
Most important: Get close to but never above the transformation temperature
A1
This recipe is not all that new. It is actually what Käthe Harnecker - a woman! working for the "Zwilling J. A. Henckels" corporation did in 1924! In words: nineteen
twenty four! She made some very good knifes from 1.2 % - 1.5 % carbon steel thatshow a clear cementite pattern!
We might not rate it as a "nice" pattern but then we have only bad copies of theoriginal pictures that do not show details of the structure. It is certainly as good as
the one shown by the Wadsworth group.

SpecialModuleKäthe
Harnecker

Käthe Harnecker and possibly the Wadsworth group, however, did not yet include another key ingredient into theirrecipe, the third major trick: Cyclingthe temperature just around the A1 transformation temperature. This will tend to
make the cementite particles larger and the size distribution narrower, and the region in between precipitate bands moredevoid of the stuff.

I'm talking Ostwald ripening here!
Strangely enough, I have rarely encountered this term in connection with wootz patterns. Ostwald ripening,sometimes called "particle coarsening", is a process that kills small precipitates in favor of larger ones.
Start with a distribution of a lot of precipitates with all all kinds of diameters, dosome Ostwald ripening, and you are left with fewer precipitates, all of which arelarge - just as in the picture above. Originally, there might have been a lot of smaller
cementite particles between the bands but after some Ostwald ripening they all
have disappeared. Precipitates below a certain size shrink and the carbon they
release goes to the bigger ones so they grow.
What does it take to inducing Oswald ripening? In the most simple case you justkeep your sample at high temperatures for a while. If you want to be a bit moresophisticated, you use a transition temperature around which you oscillate thetemperature like this:ScienceModuleOstwald
Ripening

Go just above A1, so all precipitates start to dissolve, meaning they shrink in size. This takes some time.
Large precipitates take longer to disappear than smaller ones.
Keep the time so short that only small precipitates had enough time to disappear completely while the larger
ones are still around, just smaller.
Cool below A1 so precipitation starts again.
The not yet dissolved remains of the originally large precipitates now act as nuclei and grow - to a size evenlarger than their starting value. The originally very small ones do not reappear.
Repeat.
Repeat - until the desired coarsening has been achieved or you run out of beer, whatever comes first.
Of course, everything needs to be done "just right" and there are many ways of doing it wrong. More to that in the links
given. What you might get looks schematically like this:Iron, Steel and Swords script - Page 552

Cementite distribution before and after Ostwald
ripening
In the microscope picture above you can see that severe Ostwald ripening was employed. You don't see it?
Consider:The precipitates in the bands are all rather large.
There are hardly any small precipitates.
The second band from the left has few and smaller precipitates than the other three ones. It is also right inthe middle between the two more prominent bands. Add a few more cycles and it will disappear, feeding the
precipitates in the bands to the left and right.
Now take some UHCS, employ all of the above, and optimize the many parameters involved. It might produce produce awootz pattern; maybe even a reasonably nice one.
So Wadsworth wins? Not yet! Two questions remain:
1. While patterns obviously can be obtained from UHCS steel by following rather clear guidelines, we do not reallyknow why they form! Our guidelines only provide for spheroidization and narrowing of the size distribution. They do
not "somehow" provide for the required non-uniform cementite precipitate distribution in bands . Think about it!
There is so far no reason whatsoever, why the precipitates should not be distributed homogeneously.
2. Even if we "somehow" do get a non-uniform or inhomogeneous cementite precipitate distribution, we do notnecessarily get parallel layers of cementite particles or bands, needed for making some of the fancier patterns
like "kirk nardeban" also known as Mohammed's ladder and therefore for "nice" patterns.
Wadsworth and others certainly tried to answer the question implicitly contained in these two statements. I won't go
into that here, however, because it is not convincing. It is more rewarding to invoke Verhoeven now. Most of his work
centers on these two points. So let's see what he has to offer.
Forming a Pattern You Can See - Some Possibilities
How do you get cementite precipitates to agglomerate in the right geometry? Sheets of cementite particles runningroughly parallel to the blade surface at sizes and spacings as discussed above?
There are several possible answers, let me list four of them:
1. The process of drawing a compact piece of UHCS (a wootz cake, billet, ingot or whatever else) into a thin andvery long, more or less 2-dimensional object like a sword blade, if done "right" by forging, milling or whatever, willproduce an inhomogeneous precipitate distribution even if it was homogeneous in the starting ingot. The structure(=cementite distribution) of the starting material could be uniform in this case.
That this works to some extent was demonstrated by Harnecker, Wadsworth, Furrer, and meanwhile manyothers. However, fancier patterns like "kirk nardeban" have yet to be made in this way. It might not be possible,
however.
2. The process of making a compact piece of UHCS (a wootz cake, billet, ingot or whatever else)" is decisive. You
must get the cementite precipitates, or potent nuclei for these precipitates, to agglomerate with the rightgeometry already in your ingot: sheets running roughly parallel to the wootz cake surface but at a much larger
spacing than later in the blade.
You need a much larger spacing because you now must forge the blade by drawing out the cake in such a way
as not to disturb the arrangements. Since the blade is much thinner, the sheets of precipitates are moving muchcloser to each other.
3. You need some mix of the two mechanisms described above.
4. There are other mechanisms involved.
Wadsworth and his followers lean to the first possibility; let's call it structure by forging. Verhoeven and his followers
champion the second one, which I will call structure by dendrites for reasons you shall see shortly.
Now let' s look at some basic possibilities for forming a pattern. Not yet a nice pattern, just a pattern.

Iron, Steel and Swords script - Page 553

1. Possibility. Starting point: UHSC with cementite-encapsuled grains and some pearlite inside like in this picture.
The structure is uniform.
All you need to do is to draw out your cake or billet with a hammer or roller. The initially "roundish" grains will
deform into a longish structure. The cementite shell cannot deform since it is brittle. It will break up into small
pieces that are still sitting at the grain boundary. Schematically this looks like this:Braking up cementite shells by elongation.
This is actually a calculated picture!
Source: Fraunhofer Institut für Werkstoffmechnik; Halle, Germany;
Jahresbericht 2013; p. 7.

In the picture above I have drawn in schematically two cementite shells in white, and how they would end up as
particles in the elongated structure.
Now polish the surface, etch and look at it. What you see might look like this:"Grain boundary " wootz
Source Taleff; Wadsworth group

The picture should look familiar; you have seen it before. Note that I'm not claiming that the real structure shown inthese pictures is exactly what I have described, just that it looks like it. The way it was made, however, would fit thegeneral idea.
What we have is a certain amount of alignment of cementite particles just by drawing out the material. A purely
geometric effect, in other words. I wouldn't call it a nice wootz structure, however.

2. Possibility. Starting point: UHSC with long cementite needles all over the place, uniform distribution
I'm talking about a structure like this:Iron, Steel and Swords script - Page 554

Wootz steel with cementite needles
200x, 1 % - 1,2 % carbon, wootz from the Deccan region,
early historical period (whatever that means)
Source: David Scott

On top is supposedly real wootz cake material with predominantly long (white) cementite needles. The picture at thebottom is from a "prill" stuck to the lid of a crucible; it features needles and grain boundary cementite. I leave open
at the moment how one gets all these needles; you might also just look up the "Widmannstätten" module
Draw out your cake or billet with a hammer or roller once more. The initially "roundish" grains will deform into a longish
structure as before. The cementite needles will break up in shorter needles and particles. As the grains get elongated,
the needle salad will get a preferential orientation into the drawing direction. A purely geometric effect once more.
.Schematically this looks like this:Pattern formation by orienting needles
Sorry - I'm not an artist. The red lines just illustrate how the elongation of the grain aligns the needles that keep theirrelative position to some extent. Now imagine the situation in three dimensions with a higher density of needles andneedle fragments. Polish the surface, etch and look at it. It might look like this:Pattern formation by orienting needles?
The picture should look familiar once more; you have seen it before. Note that I'm not claiming that the real structure
shown in these pictures is exactly what I have described above. The way it was made, however, would fit the generalidea.

3. Possibility. Starting point: UHSC in "cake" shape (for example a wootz cake) with cementite or strong carbide
forming elements arranged in a layered or striated structure as shown:

Iron, Steel and Swords script - Page 555

Wootz cake with striated distribution of cementite /carbide formers
If the picture looks slightly familiar - that's because you may have seen in in chapter 9.
You may now wonder how you run a crucible process in such a way hat this kind of structure evolves. The answer is: I
don't know. I have made suggestions but I have no idea what, exactly one needs to do to make it work nor if it ever justhappened or if it is possible at all in UHSC. I do know, however, that this kind of structure is observed in lots of otherstuff that solidified from a melt.
And no! This has nothing to do with dendrites and what Verhoeven proclaims about making a final striated structure
in a blade - I'll get to that.
Le's just assume you have a wootz cake with this structure, and that the distance between two striations is large.
Then all you have to do is to draw out the cake into a blade, making sure that the cake top / bottom ends up as thesides of the blade as evident from this this simple graph:

Producing a "perfect" pattern from a striated wootz
cake
We know that the distance between the cementite sheets should be around 50 µm and that means that the
distance in the striated wootz cake should be correspondingly larger (around 500 µm=0.5 mm, say).
All you have to do is to precipitate large cementite particles in the striated structure and that isn't too difficult if you
already have small cementite particles or very strong carbide formers in the desired structure. What you get after
polishing / etching the surfaces might look like this in cross-section, note the "shallow angle magnification" effect:

Iron, Steel and Swords script - Page 556

Striated wootz blade; cross-section
Source: Verhoeven

Note that I'm not claiming that the real structure shown in these pictures is exactly what I have described above.
The blade was actually made with the "Verhoeven recipe" and the starting material may not have contained a
striated cementite / carbide former distribution.
However, Verhoeven would have a hard time to prove that this was not the case.

Please note that in all three cases it is generally possible to make the structure more pronounced by employing
Ostwald ripening by cycling as described above.
It should be clear by now that in our wootz blades we want to get the striated distribution shown right above. It
allows the smith to produce the more complex patterns by manipulating the geometry of the cementite distribution
during forging; I'll get to that.
In the third example here I have shown that a special structure in the wootz cake or whatever starting material you use
is one potential way for doing that.
Now let's look at other ways, in particular Verhoeven's ideas.

1)

A. S. Pandit and H. K. D. H. Bhadeshia: "Divorced Pearlite in Steels", Proc. Royal Soc. A (2012)

2)

M. R. Barnett, R. Balasubramaniam, Vinod Kumar and Colin MacRae: "Correlation between microstructure andphosphorus segregation in a hypereutectoid Wootz steel", J Mater Sci (2009) 44:2192–2197"The tool (=sample inevstigated) that was used in the present study was obtained from a blacksmith named MandalojiGangaram from the village of Konapuram, located in Kammarpalli Mandal of Nizamabad district of Northern Telangana
region in Andhra Pradesh state in India. This was collected and recorded during the recent survey of Wootz steel-making
sites in Medieval Telengana . This village is in very close proximity (15 km) to the famous Wootz-producing center ofKonasamudram".
Well. One might assume that the sample is not all that old; 19th century, maybe?

3)

John Verhoeven and Alfred Pendray: "The Mystery of the Damascus Sword", Muse, Volume 2, Number 2 (1998) pp. 35 43

4)

Yes, you purists out there, you are right. I should have considered the volume change too, the fact that 1 atom of carbon
and 3 atoms of iron in cementite occupy a volume somewhat different from that those 4 atoms take up in pure iron withthe carbon atomically dissolved. Forget it!

Iron, Steel and Swords script - Page 557

11.5.2 Structure by Dendrites?
Verhoeven's Dendrite Model Step by Step
Let's start by looking closely at Verhoeven's "nice wootz structure by dendrites" hypothesis. A short version of the"structure by dendrites" hypothesis a given in this module; I will repeat it here for easier reading:According to Verhoeven, what you need for making a wootz sword with a "nice" pattern that is based on a striateddistribution of cementite as discussed before, are the following ingredients:
1. Proper starting material. If you want a "nice" pattern it is not sufficient (as Wadsworth claims) to have broken-up
cementite particle in the starting UHSC that align themselves to a pattern upon rolling or forging.
2. You need traces of certain elements known as strong carbide formers (vanadium is best) in your starting
material. These elements act as nucleation centers for metal carbide particles like VC or some combination of VFe-C and their formation competes and interacts with the "normal" Fe3C cementite formation.
3. The distribution of the metal carbide particles in the final blade must have the same basic pattern as the
cementite particles that actually form the visible pattern. This necessitates an inhomogeneous distribution of the
crucial impurities in the starting material, and that comes about because:
4. Something that happens during the dendritic solidification of the original melt that produces a suitable
inhomogeneous distribution of the metal carbides, which, upon drawing the ingot into a blade by forging (orrolling), produces a suitable banding i.e. the required layered structure of the cementite particles.
5. Points 1- 4 might already be sufficient for producing a pattern. For the formation of a well-visible nice pattern you
need in addition several temperature cycles during (low temperature) forging,Yes, this is quite complicated. And let me make clear right away that the " banding" mentioned above, while playing a
key role in the whole process of wootz blade making, is a process that might also happen in modern steel making andthat it is something that is not very well understood at present.
Verhoeven and "his" master smith Al Pendray have succeeded in producing a very good kirk nardeban and rosepattern from scratch. So far nobody else seems to have been able to do that. That is certainly a strong point in thefavor of Verhoeven's "dendrite" hypothesis, if not an outright proof? Well - not quite. Lots of ancient smiths have also
produced "kirk nardeban" patterns from scratch, and their theories, if they had any, were certainly wrong.
In what follows I'll discuss the "structure by dendrites" hypothesis of Verhoeven in some detail and put it into
perspective. His 2007 paper, accessible by this link, provides the base.
First, let me point out that Verhoeven's hypothesis could easily work - provided a few "minor" points are met. It could
easily work because most of it is based on sound and well-known scientific ingredients.
The first point to look at is the solidification of a liquid iron - carbon mix, that also contains traces of some key
impurities, via formation of dendrites.. That is not an easy thing to do. I have given you an "easy" backbone module forthe topic and you might want to refresh your memory now by looking at it.
If you're not easily scared, you may also want to look at the following science modules dealing with solidification,
segregation and dendritic growth:
1. Basics of Segregation.
Topics covered are: 1. Some basics about segregations. 2. Phase diagrams, "macroscopic" segregation andthe segregation coefficient. 3. The flow of energy and particle currents through the solid-liquid interface duringfreezing - and what it implies.
Mostly prose. Discussing why solidification is so unbelievably complex as soon as one looks at details.
2. Constitutional Supercooling and Interface Stability
Topics covered are: 1. Non-equilibrium and how systems try to get back to equilibrium. Exploiting thedifference between currents and current densities. 2. What is constitutional supercooling and calculations fora simple model. 3. Supercooling, interface stability and dendritic growth plus some remarks to convection in
the melt.
Getting to the heart of dendrite formation. Some equations and a lot of illustrations.
3. Supercooling and Microstructure.
Topics covered are: 1 How supercooling plus segregation determines the microstructure of the forming solid.
2. A closer look at what happens when we cast an object. 3. Temperature gradient and interfaces velocity are
the most important parameters for the microstructure.
What solid structures look like depending on crystallization conditions. The relation between dendrites andgrains.
4. 4. Segregation at High and Ambient Temperatures
Topics covered are: 1 What could happen during cooling. 2. A simple model for macrosegregation at hightemperatures 3. Microsegregation at high temperatures. 4. What is left at room temperature and a simple
way to look at the effects of diffusion. The importance of microsegregation for the nucleation of precipitates.
How the room temperature structure evolves and what all the impurities are doing till the end
5. Striations.
Striations, an universal expression of microsegregation, are necessary for wootz steel patterns but notcontained in the preceding modules. Examples are given and discussed.
Iron, Steel and Swords script - Page 558

Forming striations right during solidification. This might happen in steel and certainly does happen in somematerials. It might have some bearing on wootz pattern formation.
Now let's look at Verhoeven's "nice wootz structure by dendrites" hypothesis step by step. Before I start I need to pointout two things:
1. Verhoeven does not always explicitly list the necessary spheroidization of the cementite. It thus must happen"on the side"; something entirely possible. Nevertheless, it is important.
2. In some of his papers Verhoeven seems to imply that the necessary layered structure of the cementites, also
called "banding", comes directly from a banded structure of the carbide formers in the originally wootz cake. This
is not correct. Verhoeven does not mean to imply that. Here is a quote with the correct statement (from this link):"...the large mechanical deformation at the hot rolling temperatures has caused the planes of dendrites ... torotate parallel to the surface of the steel plate during hot rolling...".
What this means is that he forging (or rolling) is instrumental for obtaining a good layered cementite structure.

First step: Have Strong Carbide Formers
For starters, the high-carbon crucible steel material must contain some impurities that are strong carbide formers like(Nb), titanium (Ti) or vanadium. In the "science of alloying" module I have written:" Very strong carbide forming elements, such as niobium (Nb), titanium (Ti) and vanadium (V), always form alloy
carbides, preferentially at alloying concentrations less than 0.1 %. The microstructures of steels containing theseelements will be radically altered."
Note that these elements form niobium, titanium or vanadium carbides and not iron carbide or cementite in the first step.
Verhoeven claims a vanadium (V) level as low as 0.004 % is sufficient to cause nice wootz patterns later. Other just"strong" carbide formers like molybdenum (Mo), chromium (Cr) and tungsten (W) might also be good.
A concentration of 0.004 % or 40 ppm is extremely low for iron / steel. Plenty of ancient crucible steels might havecontained these impurities at such low levels. There is no particular problem yet with Verhoeven's hypothesis.
However, it does sort UHCS samples in two camps: those with the proper impurities and those without. Only the
first group is suitable for making blades with nice wootz pattern.
Wadsworth would disagree

Second step: Have large dendrites during solidification
Solidify in such a way that large dendrites are produced at the solid-liquid interface. Note that it is not good enough tohave dendrites. They must be rather large because in Verhoeven's model their average distance determines the distance
between the cementite bands that form the pattern in the blade. Since forging reduces this distance (akin to what isshown here), it needs to be in the 0.5 mm region.
To achieve that is quite possible. I have provided already several pictures that show large dendrites in steel. You
need a slowly moving solid-liquid interface and a suitable temperature gradient or just the "right" slow coolingconditions during the solidification.
Note that it doesn't matter for this how fast or slow you cool after everything has solidified.
It is certainly possible to achieve this. Chances for getting large dendrites / grain structures tend to be better if thesteel was liquid well above its melting temperature or well superheated and not just barely so; look at this picture.
Verhoeven illustrates this (and a bit) more with the following picture:

Verhoeven's illustration of dendrite structure duringsolidification
There is nothing wrong with that picture, except perhaps that it insinuates, just like this picture shown in the famous"Scientific American" article, that all dendrites, everywhere and at all times, are the same size are growing parallel
to each other all over the place. That is not the case!

Iron, Steel and Swords script - Page 559

Third step: Realize that an inhomogeneous distribution of the carbide formers results
During solidification the carbide forming impurity atoms (and the carbon) strongly "segregate " into the region between
the dendrites. This means that the iron between the dendrites, the iron that solidifies after the dendrites have formed, isenriched with carbide formers (and carbon), i.e. the concentration there us much higher than the nominal concentration.
Inside the dendrites themselves the concentration is much lower, they are denuded of carbide formers (and carbon).
It is thus far more likely that carbides like vanadium-carbide forms between the dendrites than in the dendrites when thesteel cools down. Since these metal carbides act as nucleation centers for the cementite that also needs to form duringcooling but somewhat later, the primary cementite forming in hypereutectoid steels a high temperatures will also
predominantly be found in the interdendritic areas, especially if you don't cool down very fast. This may also help tospheroidize the carbide.
All of this is absolutely correct; it just makes ingenious use of basic segregation theory. One only needs to add that
other defects like grain boundaries might also nucleate some primary cementite in competition with the metal
carbides.

The big question: Does Step 3 produce sheets or bands of cementite in the blade?
Now it gets interesting. In the figure above there are dotted lines labeled "sheet geometry". The text going with it reads:"As shown in view B of Fig. 4 (the figure above), the interdendritic arrays possess a geometry that displays sets of
discrete sheets or bands".

This is supposed to get you to believe that the carbide formers andthus also the cementite is arranged in regular bands inside yourwootz ingot as soon as it has cooled down a bit after solidification.
It is not! Or only up to a point. There are several reasons for this:First of all, there simply aren't planes of high vanadium or whatever concentration. There are lines! This pictures
makes that clear.
Second, even if one accepts the "sheet geometry" in Verhoeven's picture shown above for the sake of the argument,
it does not exist like this in real materials, even within just one grain. Just look a the following pictures and imagine
the black dots to be the top of the dendrites:

Areas denuded of something (black) and enriched insomething (white)
Does the "something" form bands?
You are looking at pores in indium phosphide (InP; left) and silicon (right); a bit more to that is here. But it doesn't
matter what exactly is shown in the picture above. Think of the dark spots as tips of dendrites coming straight up atyou. What you see is that the area between the dendrites can be described as three overlapping bands, indeed, but
only as long as the dendrites are arranged in a rather perfect repetitive pattern (forming a "crystal", in other words).
Real dendrites won't do that; the pictures in this link show that. So arrange them a bit disorderly like in the righthand picture - and where are your bands?
Third, the steel is poly-crystalline. The dendrite orientation changes from one grain to the next one, and so do the"sheets" or "planes". Modifying Verhoeven's picture to take this into account yields this:Iron, Steel and Swords script - Page 560

There are no aligned sheets in poly crystals(schematic view)The drawing shows a schematic structure with perfectly aligned dendrites. An actual structure can be seen in thislink or below

Real dendritic structure in 1.6 % C as-cast steel
Source: Verhoeven's book: Steel Metallurgy for the Non-Metallurgist;
Fig. 15.4

Ironically, this picture is from Verhoeven's book: "Steel Metallurgy for the Non-Metallurgist". It just makes clear that
there no sheets aligned for long distances in poly crystals.
Enough! It is absolutely clear by now that there are no parallel sheets or bands of high impurity concentration becauseof dendrites that run nicely parallel to each other through the whole wootz ingot right after it solidified or after it cooled
down to room temperature. This is not to say that there isn't an inhomogeneous distribution of impurities - it is just notbanded in an orderly fashion because of dendrites!
To make that very clear:

No!
Verhoeven's "structure by dendrites" mechanism has not produced
a wootz cake with a banded or striated distribution of carbides /cementite as shown in this picture.
Verhoeven knows this, of course. In this article he writes: "The ingots (of wootz crucible steel made by him) are flat
across the top displaying large radially directed surface dendrites. Their microstructure displays a combination ofgrain boundary and Widmanstätten cementite with no apparent relationship to the prior dendrite arrays." .
So let's look at the crucial next step:

Iron, Steel and Swords script - Page 561

Fourth step: Mechanically deform the ingot / wootz cake into a blade shapeThat is the step where the necessary banded structure of the metal carbides and thus the banded structure of thecementite originates. Interestingly, this step is not prominently mentioned in Verhoeven's papers. Verhoeven, however,is quite aware of the importance of the mechanical deformation discussed here as a necessary ingredient for making
wootz swords with a nice pattern. Here are some relevant quotes:
A systematic study of longitudinal microstructures versus the extent of forging revealed that the alignment of thecementite particles occurred gradually during the forging process.
The interdendritic arrays possess a geometry that displays sets of discrete bands. The metal flow during the hot
deformation of the ingot into a plate form causes some of these band sets to rotate into alignment parallel to thesurface of the deformation.
In plain words: Whatever distribution of carbide formers / cementite particles you have in the UHCS that you use forforging a blade, it is the massive mechanical deformation (by hammer in the old times, by a roller mill today, bywhatever) that might align cementite particles in bands.
That is - in a small way - what I have shown to happen for purely geometric reasons before.
That's what Wadsworth more or less claimed all along. However, he did not invoke carbide formers, and they will
make a difference as we shall see.
It is important to note:
You cannot align just the carbide former atoms. They are just impurity atoms, sitting preferable in that part ofa crystal that has solidified last, i.e. in the interdentritic space. Since they don't move much by diffusion
during the whole process, their relative position doesn't change much. They go to wherever the iron atoms
around them go.
You cannot align carbon atoms. Since they move around like crazy by diffusion, their originallyinhomogeneous distribution homogenizes quickly during normal solidification.
But you don't have carbide formers and carbon atoms around for very long. First the carbide formers form
carbides like vanadium carbide right where they are, removing some of the carbon atoms. Then the remaining
carbon forms cementite precipitates wherever nucleation is easy - at the metal carbides and grainboundaries. And (relatively large) cementite particles you can alignAlso note that after solidification is complete, the dendrites do not exist any more. All that exists is a crystal likeaustenite that contains some dirt and possibly already some primary cementite. Only the distribution of those
things in the crystal supplies a kind of vague memory of the former dendritic structure. In addition, there might be a
few small-angle grain boundaries in places where the dendrite alignment was a bit off.
Now comes a surprise: Running a (hot) piece of any steel through a roller mill, reducing
its thickness, often produces banded structures with a nicely staggered sequence ofcarbon-lean, carbon-rich, carbon-lean, .... , layers. Consult the advanced module fordetails. Verhoeven has actually written a big review paper1) about banding as thatphenomena is called, full of complex stuff. It is entitled: "A Review of Microsegregation
Induced Banding Phenomena in Steels".
However, Verhoeven (and everybody else) is rather vague about exactly how thismechanical alignment process works. He goes through great lengths to elucidate thevarious (and rather complex) mechanisms of cementite formation in various kinds ofhypo- and hypereutectoid steel, and how it depends on cooling rates and God knows
what else. Here is what he has to say about the mechanisms that are responsible forforming the bands during the heavy plastic deformation occurring during milling (orhammering):

Advanced
ModuleBanding

An interesting question that has not been studied in the literature is how the dendritically produced segregationarrays become so well lined up into the two-dimensional planar bands during rolling or forging of sheet materials.
When observing strongly banded structures, it is amazing how well the bands line up with the deformation planein sheet materials.
The morphology of the ferrite and pearlite bands depends on the type of deformation employed. It has been foundthat deformation to rod shapes produces cylindrical morphologies, while deformation to plate (sheet) shapes
produces planar morphologies.
The presence of the planar bands in the deformed ingots indicates that during deformation some set of IR(interdentritic region) lattice planes probably becomes aligned in the deformation plane during the hot
deformation. If this suggestion is correct, it seems likely that it is one of the high density planes of the IR lattice,{100} or {110}, that lines up in the rolling plane, perhaps by some type of lattice rotation.
In this case, carbide banding is inevitable in the wrought product as the carbides often cannot be made todissolve into the austenite on forging and will simply remain in the steel and align during the hot working process.

Iron, Steel and Swords script - Page 562

In other words: Verhoeven (and everybody else) does not know exactly how this mechanical alignment process
happens. Nobody knows. I have studied a lot of papers and books and found no convincing explanation. Prettymuch all authors weasel a lot because this is acutely embarrassing. Banding is a major (and mostly very unwanted)
effect that occurs in much of steel processing - and we don't know exactly what happens!
However, Verhoeven concludes that pronounced banding is easier to obtain if the material already has "pre-banded"regions. He might well be right about this because banding does not always occur in structures containing mixes of
hard and soft regions. The "grain boundary wootz" of Wadsworth or Harnecker's wootz is observed in steel that
seems not to have produced banding upon deformation. I'm not sure if I subscribe wholesale to Verhoeven's point ofview but Verhoeven knows a lot more than I do about banding and making wootz structures so let's go with it for thepresent.
Let's just look at a simple picture to illustrate what happens:

Schematics of banding during rolling / mechanicaldeformation
it is a very simple picture but shows the essentials (and I am repeating myself to some extent on purpose here):At any temperature after solidification (including room temperature) the slow-diffusing impurities, including allstrong carbide formers, are still more or less where they were right after solidification at temperatures close
to the melting point. They simply can't go very far if the cooling rates are not excessively slow.
That is not true for atomically dissolved carbon. While it was also enriched between the dendrites duringsolidification, it can diffuse rapidly and covers large distances already at high temperatures. The distribution
thus might be rather uniform at high temperatures.
If strong carbide formers like vanadium (V) are present, the respective carbides may form already at hightemperatures; they would tend to be found in the interdendritic regions.
For UHCS steels, primary cementite forms as soon as the ACM temperature is reached (look at the phase
diagram!). This cementite may be found at the austenite grain boundaries, forming Widmanstätten typeneedles, or nucleate at metal carbides and form more or less spherical precipitates. Nobody has seen thatstructure because it transforms completely at the A1 temperature.
As soon as austenite transforms to ferrite at the A1 temperature, the 0.76 % carbon still in solution needs toform cementite. In hypoeutectoid steel this is the first time cementite is is formed, in hypereutectoid crucible
steel this secondary cementite comes on top of the primary cementite. In the most simple case the primarycementite just grows. If carbide formers dominated the cementite nucleation, the cementite and thus carbonrich regions mirror the distribution of these slow diffusing impurities, a least up to a point. That would not,however, result in well-defined bands for all the reasons given above
Rolling at high temperatures or equivalent hammer-forging, is the decisive process that causes the bands.
Banding due to rolling occurs in hypo- and hypereutectoid steel, including steel with no known addition of strong carbide
formers. This might be seen as implying that carbide formers are not all that important for the formation of a nice pattern,in contrast to what Verhoeven claims. That is not quite true, however. The difference shows in three situations; two of
which are (related) :Without strong carbide formers the primary cementite forms at grain boundaries, making spheroidization difficult if
not impossible.
Anneal the stuff at high temperatures for a long time. The cementite will dissolve and the released carbon atoms
diffuse all over the place, homogenizing their concentrations in both case. The carbide forming elements,
however, stay pretty much in place since they diffuse much more slowly than carbon. They also do not dissolvethat easily. Now cool down again and cementite formation occurs once more at the places where the carbide
formers are concentrated and thus in a banded distribution. Without carbide formers it would precipitate more
uniformly all over the place.
In other words: Without the carbide formers you loose an originally present banded structure during heating, with
Iron, Steel and Swords script - Page 563

carbide formers you reconstitute it.
A banded cementite structure caused by banded carbides from carbide formers is more forgiving and easier tomanipulate for the reasons given above. Exceed the transformation temperature once during forging and thestructure will soften. But you can not only easily reconstitute it but even sharpen it by proper thermal cycling and
Ostwald ripening. And that leads us to the:Fifth step: Thermal cycling / Ostwald ripening
We now have a banded distribution of at least the carbide formers if not the cementite. It might be sufficient for
producing a pattern but not yet for producing a nice pattern on wootz blades. Verhoeven lists as one of his 7 conditions
for nice patterns: "There are no significant differences in particle size or shape on transverse versus longitudinal
sections".
In other words; the cementite particles should all have about the same (and not too small) size.
Well, we already know how to achieve that. Either straight Ostwald ripening at high temperatures but still below A1or thermal cycling between just a bit above and below A1. I have described that that in detail before; here I will let
Verhoeven describe what happens:
These results show that during the thermal cycling the microsegregated impurities are causing the cementite
particles to gradually increase in size and density along the remnant IRs (interdentritic regions) of the forged ingot
as the number of thermal cycles increases.
...
During the heat-up part of each thermal cycle the smaller cementite particles will be removed by dissolution while
the larger particles will remain at a reduced size. During the cool-down portion of the cycles the larger particles willgrow. It is not likely, however, that the smaller particles will reform at adequate rates to replace themselves duringcool-down because this requires nucleation, and the presence of the nearby larger particles provides sites for
cementite growth without need of nucleation. Hence if bands of larger particles once form, the cycling process willcause them to grow at the expense of the smaller particles.
...
Hence it seems most likely that the cementite is simply nucleating on austenite/ austenite grain boundaries during
the thermal cycling and then forming into aligned bands of c!ustered particIes by the coarsening processes such asthat discussed above along with some coarsening due the classical Ostwald ripening mechanism.
Now we are almost done - as far as "Structure by Dendrites" is concerned. I only need to mention that in some of what I
have written you might replace the A1 temperature (where secondary cementite forms) by the ACM temperature (where
primary cementite forms) and look at the austenite formation instead of ferrite formation for getting some important
inhomogeneities. But things are already complicated enough, so let's stop here.
Whatever happens in detail, the steps described above, if done right, make sure that the blade now contains sheets orbands of proper cementite particles that are roughly parallel to the blade surface. We can now produce nice patterns byusing some forging tricks.
That will be covered in the next sub-chapter. Here it only remains to state two things. First:

Producing nice wootz patterns requires to do a lot of things "justright". There is, however, nothing mysterious about those "things".
Second: I still need to announce the winner of the Great Verhoeven - Wadsworth Jousting Tournament. So:

The Winner is...
Me, of course, for figuring out what this was all about. But seriously now: Verhoeven does come out ahead!. He andhis co-workers did shed a lot of light on the specifics needed to progress from a pattern to a nice pattern. Moreover, they
actually made nice wootz structures, including kirk nardaban with roses, somebody nobody else so far has achieved as
far as I know.
My only criticism is that some crucial issues are a bit underdeveloped in some publications (on both sides) and that it is
not always stated outright that there are still some open questions.
It should also be clear by now that Verhoeven's work leads right into some topics of modern iron an steel research thatare not yet fully understood. And that allows me to make a suggestion of my own:

Iron, Steel and Swords script - Page 564

All the problems around producing parallel bands of first carbide formers and later cementite precipitates disappear ifthat happens right during solidification. It is clear by now that this does not happen by a simple "dendrite
mechanism". What about some other mechanism?
The wanted structure is actually known from the solidification of many other liquid-solid systems and called
striations. I have already written a lot about that so I just give you the links:
What are Striations?
The 5th module in the "Segregation Science" Superlink. All about what striations are, where they have been
observed, what causes them, and how they might relate to wootz patterns
Segregation and Striations in CZ Silicon
In his module you learn all about striations always found in the huge single crystals of silicon. They are quite
well understood - and the mechanism behind their formation is not the same as the suspected one incrucible steel.
Microsegregation and "Current Burst" theory
A highly speculative hypothesis of striation formation in normally solidifying melts including dendrites
Science of Alloying
Some hints to striations in steel. An Application to "Wootz" Steel?

Enjoy!

1)

John D. Verhoeven: "A Review of Microsegregation Induced Banding Phenomena in Steels", Journal of Materials
Engineering and Performance (JMEPEG), Vol. 9/3 (2000) p. 286 - 296

Iron, Steel and Swords script - Page 565

11.5.3 Forging a Wootz Sword
Early Wootz Swords
Let's engage in our stupid little game once more:

Who made the first wootz sword with a nice patterned blade?
When and where?
Like always, it is a tricky question with no definite answer. First I will make clear what I did not ask:
I did not ask who made the first blade from crucible steel. That happend probably much earlier. But blades
made from crucible steel do not necessarilly show a pattern. The "Ulfberht's" possibly made from crucible
steel around 1000 AD did most certainly not show a pattern. That can be deduced from their microstructure .
I did not ask who made the first blade from crucible steel that showed some pattern by accident. Any UHCS,
as we have seen, will easily produce some pattern - but not necessarily a nice one.
I did not ask who made the first blade from crucible steel that could have shown a nice pattern if properly
etched. It is conceivable that smiths made blades with the proper banded cementite structure for a nicepattern without having been aware of that. Since rather special forging techniques are needed, it doesn't
appear to be very likely, though.
The question is thus only about the smith who conscientiously forged a blade and finshed it with the intent ofmaking a nice pattern.
There is of course no definite answer to this question. We can be rather sure that "pattern forging" evolved overmany years, from a process where blades with some pattern were created more or less accidentially, to a process
where materials and forging techniques were optimized. That took many steps and the process of making bladeswith a nice pattern probably required a century or two for maturing.
The first blades with (very) nice patterns shown in Khorasani's magnificient book are from the Timurid period 1370 AD 1500 AD. Here is one:Samshir from the Timur period in Iran
Source: Khorasanis's book

The patterns on the shamshirs shown are so perfect that they must have been based on an older tradition. While quite
likely older blades with a nice pattern exist somewhere out there, I have yet to see one. So for answering our question
we must turn to early writings.
I have already done this in the special module "Antique Texts Concerning Crucible Steel " There you can read that
Al-Kindi (ca. 800 AD - 873 AD) mentions that swords made from pulad (=wootz) exhibt a pattern (known then as"firind" or "jawhar") and that might be the first description of the "water" pattern obtainable with some crucible steel,
Then we have AI-Biruni (973 AD - 1048 AD) who also comments on the "water" pattern that could be produced withcrucible steel. And so on.
We also have Anna Feuerbach's analysis of a few old blades from the 3rd–4th
century AD that were made from crucible steel that sported aligned spheroidal
cementite, the metallographic feature needed for a nice visible pattern. It is notclear, however, if the smith was intentionally going for a pattern and what it would
have looked like.
Iron, Steel and Swords script - Page 566

cementite, the metallographic feature needed for a nice visible pattern. It is notclear, however, if the smith was intentionally going for a pattern and what it would
have looked like.
All things considered we might be justified in assuming that blades with a nicepattern have been around a least since 800 AD. Perhaps even somewhat longer but
probably not much longer because in many much older documents from India,
crucible steel and patterned swords are never mentioned.
That opens the interesting questions if one of the most famous swords in history,
the Zulfiqar of the Prophet Mohammed, was a wootz blade?

Advanced
Link
Zulfiqar

Making a Mohammed's Ladder
From the preceding modules it should be rather clear how a "normal" wootz blade was forged. The key points were:Start with a suitable "wootz cake" or "bulad egg". It needs to be a high carbon steel, homogenous without slag
inclusions, and preferably with traces of strong carbide formers like vanadium (V); some manganese (Mn)wouldn't hurt either.
Spheroidize the cementite if that has not already happened during the cooling of the crucible steel. It is not clear(to me) if the ancient smiths used some special procedure for doing that right at the beginning of the blade forging
or if spheroidization happened as a by-product of the forging process.
After spheroidization you must keep the temperature rather low. If the blade ever gets above the A1 temperaturefor some time, all is lost.
The necessary Ostwald ripening demands several temperature cycles between just above the ferrite - austenitetransformation temperature around 730 oC (390 oF) for just the rigth time. That may just happen by the forging
process itself if done just right.
Depending on all the details, you end up with a wootz blade that shows one or the other of the less intricate patterns .
But now we want to make a step pattern, better known as kirk nardeban" or Mohammed's ladder with "roses" init.
The picture below (from am Indian wootz blade in my possession) shows a few weak "steps". The smith has madean attempt at a kirk nardeban pattern and succeeded for some ladder rungs in parts of the blade but not everywhere.

Three faint rungs of a kirk nardeban pattern
How is it done? The principle is easy. Make a hump in the otherwise somewhat wobbly but planar stack of yourcementite precipitate planes. Schematically (very schematically, I'm not an artist) you could produce something likethis:What also works is to cut grooves as shown below, followed by the more tricky part of "filling " them again, This"evening out" the blade must be done in such a way that the cementite planes are arranged as shown.

Iron, Steel and Swords script - Page 567

You might also make grooves by cutting with a chisel and God smiths know in how many other ways. That this works
has been demonstrated by Al Pendray, his results are shown here and below I show them again:

Ladder and rose pattern made by
Al Pendray around 1998 .
The ladder and rose pattern produced by groovesa) cut orb) forged into the surface of the nearly finished blade
Source: Verhoeven, A.H. Pendray and W.E. Dauksch

I really don't know how you do all this in detail - ask a smith! The only problem is that there aren't too many around right
now who could tell you. And the few who could will probably keep their mouths shut.
Anyway, the principle of manipulating wootz patterns is clear. The principle for making a major marble sculpture like thisone is also quite clear: Take a big piece of marble and knock off whatever is not needed.
The guy who makes a great marble sculpture we call an artist, and his work a piece of art. I do not hesitate to call asmith who makes a wootz sword like the ones shown here an artist too, and his work a piece of art. And now weare right back to the beginning of this hyperscript, far, far away.
The Myth Around Wootz Swords
Wootz swords with a nice "water" pattern were supposed to be unbelievably good, far better than anything else. A whole
mythology developed around this. Since the "Japanese sword" enjoyed the same mystification process, I won't go intomuch details here but do that in the next module.
Wootz swords, for example, were believed to be unbelievably sharp. You even could cuts stones with a wootz blade
without the slightest damage to the blade. And of course you could bend them around your waist without any problems.
We have encountered some of these claims before:
In this link Sultan Saladin cuts a soft silk cushion with his wootz scimitar.
Here the (wootz) blade is "bent around the body of a man and breaks not". The author of this contribution
actually makes fun of the wootz mythology but must have based his satire on the claims he encounteredaround 1890.
In this module a stone is cut in half by a wootz blade wielded by one of Germany's biggest if fictive hero.

Iron, Steel and Swords script - Page 568

Of course, the mythology around wootz swords owns quite a bit to all the early and later writings concerning the"secret" of the Indian steel, and to the fact that crucible / wootz steel was indeed better in some respects than other old
steels throughout the millennia. No doubt about that. However, even the best wootz is just a (ultra) high carbon steel,and even with spheroidized cementite this steel has its limitations.
How good wootz (or "true" damascene) blades really are is something one can find out. Prof. Zschokke (an early
metallurgist from Switzerland) was lucky enough to get a few wootz blades for (destructive) investigations. This is quite
unusual because these blades are valuable and museums and collectors do not easily agree to have some of them
destroyed.
Manfred Sachse in his book reports some of Zschokke's results. Here are a few:
General composition
Sample

[C]

[Si]

[Mn]

[S]

[P]

1. Wootz Saber

1.874

0,049

0,005

0,013

0,127

2. Wootz Saber

0,569

0,119

0,159

0,032

0,252

3. Wootz Saber

1,324

0,062

0,019

0,008

0,108

4. Wootz Saber

1,726

0,062

0,028

0,020

0,172

5. Modern welded steel saber

0,606

0,059

0,069

0,007

0,024

6. Modern cast steel saber

0,499

0,518

0,413

0,038

0,045

Properties
Sample

1

2

3

4

5

6

Bending toughness

13,4

15,2

11,5

14,5

21,6

30,0

Work to bend

94

221

55

63

361

622

Angle of bending

27

59

19

17

69

78

Hardness

216

233

193

248

347

463

Specimen 1 - 4 were wootz blades, 5 and 6 were modern early 20th century welded and cast steel blades from
Solingen. They were the winners in every category.
Nothing very special or very good about wootz blades. Well, we already know that from what I have written before. You
can also read a short article from Stephan C. Alter from 2017, entitled: "On Slaves and Silk Hankies. Seeking Truth inDamascus Steel" that puts all these myths in perspective.

Iron, Steel and Swords script - Page 569

11.6 Japanese Swords

11.6.1 The Myth and the History of the Japanese Sword
The Myth
I started this enterprise because I wanted to know more about a few things concerning iron, steel and swords. I'm amaterials scientist after all, and I should know a bit more than just the essentials about iron and steel, even so my
speciality are semiconductors. Somehow the project went out of control. By now I have written around 370 modules, farmore than anticipated. Now I'm about to write the last modules about sword making. I'm now getting to the ultra-famous
Japanese Sword! The climax is near!
You know what?

I'm bored
And I'm fascinatedI'm bored because the making of a Japanese sword just doesn't contain much new stuff. Pretty much everything ofbasic metallurgical interest connected to the making of Japanese swords has been covered before.
Note that I'm not saying that a Japanese sword isn't a supreme weapon or a major piece of art. I also have noproblem asserting that it counts among the best swords a smith can make with bloomery-made iron and steel.
I do state, however, that the same can be said for a well-made Iranian wootz shamshir with a kirk nardaban pattern,a Roman pattern welded sword, a Frankish all-steel sword and many other swords. In other words: when
considering Japanese swords, art appreciation is often more important than metallurgy.
I'm fascinated for a number of reasons. Most prominent, perhaps, because the "Japanese" look at "their" swords
primarily as pieces of art and not weapons, indeed. The art created by a smith, no less! Important features of thepiece of art called, for example, a katana, are how the smith manipulated finer details of metallurgy to achievecertain delicate features visible on the blade if you know how to look. The attention to details, in other words, is justway above anything encountered elsewhere, as far as we know.
My fascination is real - I actually acquired a "Daisho" from the Edo Kanbun era (1661 - 1673); more about that here
So what is so special about Japanese swords or katanas? I'll give you a whole list below but the first point is simple:
they are still around in prime conditions! The same goes for (wootz-bladed) shamshirs, tulwars, and so on.
In contrast we do not have a single old pattern welded sword that still looks like new. All you see in most cases is apiece of heavily corroded steel and that makes it difficult to admire that thing as a masterly piece of the smiths art. One
needs to bear in mind that a typical pattern welded sword is about 800 - 400 years older than the typical nihontos or
shamshirs from 1200 or later.

The swords that cut it all?
Large picture
Source: The Beauty of the Japanese Sword, History and Traditional
Technology. Michihiro Tanobe; The Japanese Sword Museum. From the
Macao Museum of Art page.

Iron, Steel and Swords script - Page 570

Looks do count, as the fashion industry knows. Good looking models routinely do make more money thanknowledgable and useful engineers. The Tizona of El Cid is probably just as good in a fight as Japanese swords
from about 1050 AD or later but she is just not as showy. The Tizona neither is highly polished nor does she sport a"hamon". We don't know if she has the hardened martensitic edge necessary for a hamon but it is quite likely forswords of her age and prominence.
A Japanese sword just looks great. Some sports cars are described that "even standing still they seem to break the
speed limit" and a Japanese sword gives you a similar impression as to what it can do. In its highly polished glitteringsplendor it already looks much sharper than your regular dull-bladed straight sword. Japanese swords just look good,even the old ones. That is the first point for understanding how a whole mythology could develop around the Japanesesword. It does look like a deadly awe-inspiring weapon and, being perfectly preserved and polished, it looks just great.
What else is there? Quite a bit. I only give you a few of the salient points; the Net is full of details. Note that much ofwhat follows also applies to wootz swords; I mentioned this already. Here is my list of all the particulars that work
together for producing the myth of the Japanese sword:
1. It's perfectly preserved and still looks great after 800 years or so. See above.
2. The Japanese themselves created a huge cult about their swords and what the possession of a sword meant for
its bearer. Look up the "code of the Samurai" etc. The Germanic tribes in the (early) first millennium might have
had a big sword cult too, but neither did they write anything down nor do we have well-preserved swords. No
competition there.
3. Some Japanese swords come with a certificate of what they could do. It's chiseled in the tang. And we talk about
the results of experiments here, like how many heads could be severed in one blow. If you own such a Japaneseblade you actually know that it severed a few heads; maybe many. That makes for this special feeling you just
don't get with other swords.
4. The Japanese swords come with a large number of great sounding Japanese names for an unbelievably large
number of very important details. Learning all this stuff puts you into an exclusive group with grandmasters andall, and that feels good.
"A long HOSO-SUGUHA that becomes gently ASAKI-NOTARE KO-MIDARE BA in deep NIOI-FUKAi and KONIE. There is ASHI and YO, and KINSUJI strikes through figures becoming slightly SUNAGASHI", says a recent
advertisement for a sword you can buy. Can't beat that. Here is an illustrated guide for the most important terms
around Japanese sword, and here is a full treatment that might infect you with the Japanese Sword appreciatiponbug.
5. The manufacturing process did not change much in more than 1000 years. Bloomery steel was and is used.
Since there is a general myth that ancient techniques are somehow better than modern ones, this adds to themyth about the Japanese sword.
6. The Japanese sword is known to be unbelievably sharp. Far sharper than anything else, because it was polishedand finished by experts drawing on hundreds if not thousands of years of experience and of course with special
and ancient secret ingredients. This is mostly plain old BS but just too good to be disbelieved.
7. A good Japanese sword effortlessly cuts through about anything without suffering damage, especially through all
the non-Japanese and thus inferior swords. This is completely plain old BS. Since owners of valuable Japaneseswords never try to cut a stone with it, for example, the myth lives on.

17th century Japanese sword for sale (about 36.000 €)Large picture with text
Source: Japanese Sword Shop Aoi-Art, March 2015

Iron, Steel and Swords script - Page 571

Enough. There are plenty of books and innumerable Internet sites dealing with the Japanese sword. And there arepeople in Japan right now who smelt iron and steel the old-fashioned way, and smiths who forge sword blades just as
their ancient forebears. That is a wonderful thing, to be sure. It is not an unique thing, however. Patrick Barta from theCzech republic does all of that for pattern welded swords, and several Americans (and others), foremost Al Pendray,successfully try their hands on making and forging wootz steel.
A few Remarks About the History of the Japanese Sword
The Japanese have (of course) an elaborate system for classifying their swords according to history. Here is the generaloutline:1. Jokoto Ancient swords, until around 900 A.D
2. Koto Old swords from around 900–1596
3. Shinto New swords, 1596–1780
4. Shinshinto New new swords, 1781–1876
5. Gendaito Modern swords, 1876–1945
6. Shinsakuto Newly made swords, 1953–present
Due to a bit of unpleasantness related to loosing a war there is a hole in the history from 1945 - 1953. It probably could
be termed "stealing of Japanese swords by Americans". Some claim that after the war there were more Japaneseswords in the United States than in Japan.
Looking a the Jokoto swords one finds, first of all, not all that much and second, straight double-edged "spatha" typeblades. Here is one known as "ken" (or "tsurugi") type:

A "ken" type 5th century Japanese blade
Source: Metropolitan Museum,, NYC 1)

The next picture, often encountered in the Net but with no clear description, shows mostly Japanese swords but
also one or two Chinese swords from the 6th century. Note that they are single-edged; technically they arebackswords

Japanese / Chinese 6th century swords
Large picture
Source: Metropolitan Museum, NYC 2)
Iron, Steel and Swords script - Page 572

There is no clear descriptions because the Metropolitan is a bit vague about these treasures 2). There also seems
to be little known about the metallurgy of these swords (couldn't find anything in a short search) but they are likely
less sophisticated than their 6th century pattern welded counterparts in Europe.
These swords embody the Jokoto (or chokuto) swords mentioned above. Their blades might consist of (faggoted?)
quench-hardened steel since this technique (known to the Celts and Romans) was first used in the 6th century inJapan.
Generally speaking, the early Japanese sword, or the technology for making it, supposedly came from China and /or Korea. I'm not debating that but considering that China's steel products were made from cast iron and not frombloomery iron / steel, it is not clear to me why Japanese swords were made from bloomery steel only up to this veryday.
Next we have the koto sword (900–1596). If you look at the picture above or the full scale rendering, you see a numberof koto swords. They look more or less like the rest, and they have about everything that metallurgically defines aJapanese sword.
No. Don't send me now hate mail or worse. I know of course that there are huge differences between koto, shinto,
shinshinto, and so on - if you only look at Japanese swords. But if you look at all swords, all of the above qualifies justas "Japanese swords". And that's why I will only give a few highlights with regard to these blades.
Koto. Old swords from around 900–1596
The typical sword of that period is the tachi. It is somewhat longer but otherwise quite similar to the later katana.
Many katanas, in fact, were made by shortening an old tachi. A tachi was always worn suspended from cords on abelt with the blade facing downwards. Early models had uneven curves (i.e. not given by parts of just one circle orone "radius of curvature") with the deepest part of the curve at the hilt. It was in essence a cavalry sword.
The making of koto swords marks the climax of Japanese sword forging. Masamune (c.1264–1343), widely
recognized as Japan's greatest swordsmith, made kotos around 1288 - 1328. Here is the so called "Ikeda
Masamune". It was a tachi but later shortened to be a Katana.

Masamune sword
Source: Swordforum 2006

Shinto. New swords, 1596–1780
These are considered inferior to most koto. Manufacturing complexity was lower in this period. Katanas appear andthey are now worn stuck through a sash or belt and paired with a smaller blade, the wakizashi , to form a "Daisho"(literally: "long - short"). The blade faces upwards in both cases.
The quenching technique had been fine-tuned to produce intriguing if occasionally ridiculous results, in particular in
the Edo era (1684 -1763). As a Japanese source states in somewhat ungrammatical but rather clear English: "Thismeans that Samurai corrupted".

Edo katana blades with flower power hamon design.
Source: Japanese Sword School Internet site around 2000; now under
http://www.nihonto.ro/

Shinshinto. Literally "new new swords" 1781–1876.
Going back to the koto style; "shinshinto" can also be interpreted as "new revival swords". Shinshintos are
considered superior to most shinto, but still inferior to koto.

Iron, Steel and Swords script - Page 573

Gendaito. Modern swords, 1876–1945.
Shinsakuto. Newly made swords, 1953–present
Forget them. The one remarkable thing about shinto and later is that all these swords were still made from bloomery
iron and steel. The Japanese sword manufacturing business never switched to blast furnaces and steel fined fromcast iron. If that makes the swords better is open to doubt. That this makes the swords a hell of lot more expensive
is a fact.

1)

The text of the Metropolitan to the ken (slightly shortened):
This ken was discovered in one of Japan’s most famous early burial mounds, known as the Eda Funayama Kofun (burial
mound), located in Kumamoto Prefecture, on Kyushi Island, in southern Japan. The mound, which was excavated first in
1873. Swords of this period are extremely rare and show the earliest stage in the development of Japanese sword blades.
The ken, a sword with a straight double-edged blade based on Chinese prototypes, was used in Japan from at least thethird century until the sixth century. At the end of that period, the double-edged sword was gradually superceded by thesingle-edged type, from which all later Japanese swords developed.

1)

There is only one text for one of the swords. As far as I can make out, it is the one in the middle:
Sword with Scabbard Mounts. Date: ca. 600. Culture: Chinese. Medium: Iron, gilt bronze, silver, wood.
This sword is said to have been found in an imperial tomb at Mang Shan, north of Luoyang, Henan Province. The Pshaped scabbard mounts, probably derived from long swords worn by nomadic Sarmatian and Sasanian horsemen,
served as a prototype for the Japanese tachi (slung sword). The ring pommel takes the form of two confronted dragons.
The rest only caries descriptions like:
Sword with Scabbard Mounts. Date: 6th century. Culture: Japanese. Medium: Iron, gilt bronze, gilt copper, silver.

Iron, Steel and Swords script - Page 574

11.6.2 Making a Japanese Sword - Part 1
The Japanese Way
Entering sword in a search engine in March 2015 netted 205.000.000 entries. Entering Japanese sword yields
11.100.000. One should think that it is easy to get a bit of unambiguous information about the basics.
Not so. A lot of the entries with high ranking are of Japanese origin and are often written in Japanese or in asomewhat questionable English, always with a lot of Japanese terms. And I include papers found in sciencejournals here. If you do not know, for example, that a "tatara" furnace is just one of the many variants of the good oldbloomery, you won't learn that from most of what you find in the Net or the science literature.
As for the iron sands used as ore; I have given up trying to figure out exactly what that stuff is. Here are examples
that shall go unnamed:
1. This material (iron sand), which consists of weathered granite, contains about 58 % iron along with very small
amounts of titanium and other impurities.
2. Iron sand is a type of sand with heavy concentrations of iron. It is typically dark grey or blackish in color. It
comprises mainly magnetite, Fe3O4, and also contains small amounts of titanium, silica, manganese,
calcium and vanadium.
3. The iron sand used is also of two vastly different types. They are the masa iron sand used chiefly with the
kera-oshi method, and the akome iron sand used for the zuku-oshi pressing method. Masa iron sand comesfrom a kind of granite made of acidic rock and has low titanium content. Akome iron sand comes from a kindof diorite made of basic rock and has high titanium content, with the presence of TiO2 at 5% or greater.
4. Iron sand with 2–5% content of iron mined from mountains ... is concentrated to the degree of 50–60% by amagnet system (...) Such enriched iron sand called masa satetsu contains 8% of pure iron Fe and iron oxide
Fe2O3 (=haematite ) with a very small amount of impurities such as 0.026% P and 0.002% S being injurious
for carbon steels. Chemical compositions are shown in Table 1:

Huh? Pure iron is contained in iron sand? A lot of TiFe appears after enrichment? Plus wustite (FeO), something
normally not found in nature. Fe 2O3, by the way, is non-magnetic hematite containing 69.9 % iron. The magnetic
stuff would be magnetite with 72.4 % iron by weight.
And so on. I have yet to find an article that describes the making of a Japanese sword in the framework and language ofmodern iron and steel science and technology. That adds mystery, of course, and that is always good for having
something look more interesting and special.
In what follows I will stay mostly within the terminology used throughout the hyperscript. I do apologize if I "translated"something not quite correctly from the typical Japanese confusionalese. Much of what follows is based on various
Wikipedia articles, Hitachi Metal Internet sites, and various scientific articles, foremost some of Tatsuo Inoue 1).
Ore, Charcoal and Flux
For feeding your smelter you need ore, charcoal and flux - look it up here if you have forgotten. Everything at smelting
needs to be "just right" but as far as the ingredients are concerned, you must go with what you have.
Ore: The ore is iron sand, whatever exactly that is. It was "mined" from deposits of sand (probably alluvial fanssomewhere) and the heavy iron oxide particles were separated from the lighter stuff by the usual flotation technique:run the mix through a canal and the heavy stuff separates from the lighter one since it isn't carried downstream as
fast and as far.
Obviously the main ingredient of the iron sand is magnetite, the richest ore of all. That allows to separate it from therest also with a strong magnet. That was certainly not the technique used in ancient times so we don't care aboutthat here.
Part of the confusion may result from describing magnetite as a mixture of Iron(II) oxide FeO (wustite) and iron(III)oxide Fe2O3.
In contrast to the ore used about everywhere else, the iron sand ores consist of rather small grains instead of sugarcube sized lumps and that necessitates some special care during smelting.
Charcoal: Whoever smelted iron knew that you need the right kind of charcoal. It needs to be just right for theprocess you use and it is thus no surprise that the ancient Japanese iron masters had clear ideas of what theywanted, just as all iron or smelter masters elsewhere.
Flux: For an old-fashioned bloomery process you typically need something (=flux) containing silica (SiO2) forforming the liquid slag that is so important for efficient smelting. Quite often the flux is simply the gangue, the"rocks" still sticking to the iron oxide or ore. In addition, the clay used for building the furnace also supplies silica,
getting "burned off" in the process. There is then no need to add flux consciously and that is what the JapaneseIron, Steel and Swords script - Page 575

smelters did.
However, your smelting process than tends to be less efficient and that is particularly true for the Japanese "tatara"
type of bloomery.
The "Tatara" Bloomery"The traditional Japanese furnace, known as a “tatara”, was a hybrid type of furnace. It incorporated bellows, like theEuropean blast furnace, but was constructed of clay; these furnaces would eventually be destroyed after the first use"says a Wiki article. Sounds like the tatara was special. Well, it wasn't. All bloomeries after 1500 BC or so had bellows
and were made from clay that would eventually be destroyed. Except for the bloomeries that were about contemporary
with the tataras, the Stückofen or Catalan forge, for example. They were of similar size but not completely destroyed
after a smelting.
I do not know how the tatara developed, it certainly hasn't always been as big as the ones that are run now or some
hundreds of years ago. So let's look at what one perceives as the typical (late; say after 1600) tatara and see how it
differs from your run-of-the-mill bloomery:
It is rectangular with a footprint as large as 3m × 1m and thus even bigger than (older) late European bloomeries.
That means that several bellows are needed to supply the necessary air. The bloom (called kera) produced after
running the tatara for something like 3 days weighs 1.500 - 1.800 kg. There is then no way to get that monster outof the furnace (like the 150 kg blooms of the Catalan furnace or even the 900 kg monsters of the 1770 Stückofen.).
The walls of the furnace supply the silicates needed for producing the necessary slag. The initial furnace wall
thickness of 200 mm 400 mm is reduced to 50mm -100 mm. That means that the reaction can not behomogeneous since in the center of the furnace flux material is not available. Note that there seems to be no
defined tap hole for the slag, it just oozes out at the bottom.
Indeed, the bloom seems to be thicker at the edges and that's also where the high-carbon steel is found. The nonuniform reaction thus may actually be good for quality of the product - but it is not so great for the efficiency of thefurnace.

Old and modern tatara furnaces
Source: Internet at large

In some drawings of tataras an elaborate underground structure is shown (obviously not present in the two furnaces
shown above) that is supposed to make sure that no humidity is encountered. "To produce optimum tamahagane it
is important that all moisture is removed. To combat this, the tatara smelter is built on top of a large 3 metre deep
underground structure. The structure includes air ducts, called ko-bune, through which the moisture is drawn out
during the manufacture process", says a source that shall go unnamed. Why moisture is a concern for Japaneseironmakers but not for their colleagues in wet Europe, and how the underground structure draws the moisture out,
remains mysterious.
Iron, Steel and Swords script - Page 576

Since the ore particles are rather small, conditions are quite different from a normal smelter where the size of theore and charcoal pieces should be several percent of the smelter dimension, i.e. 5 cm - 20 cm for a tatara. Whatthat means for the smelting process in a tatara is anybodies guess but the air flow resistance and the wall effectmust be a concern.
During the 3 day smelting about 8.000 kg of ore (iron sand) and about 13.000 kg of charcoal are fed to the smelter,
producing a bloom around 1.500 kg. The ratio of ore : bloom thus is around 5 : 1, not a great value for a large-size
smelter.
Here are some blooms:

Blooms(kera)
producedin tatara
furnaces
Source:Internet atlargeThis is not clean stuff but the usual messy sponge-like conglomerate of iron / steel with all kinds of carbon
concentrations plus enclosed slag, charcoal, and dirt pieces. It is certainly bigger but not necessarily better than
European counterparts. It does not contain phosphorous though, due to the ore used. That is generally very good
but prevents decorative pattern welding that relies on phosphorous steel for color contrast.
For a piece of not-so-great iron / steel, the bloom produced in a tatara furnace is fantastically expensive. The costs
for making a tatara bloom are in the $100.000 region, about 100 times more than what you pay for the same amountof modern steel.
Producing the Starting Material
The first "nihonto", the curved single-edged Japanese swords, were "koto" or old swords from around 900–1596.That
time period covers 700 years and the swords forged around 900 were of course different from those made 700 years later- if not much in looks, certainly in composition.
The very early Japanese sword smith forged swords around 1000 AD in the same way some of his colleagues did that inEurope about 1000 years earlier. He made a blade from one piece of iron / steel. He might have used just one bloom but
more likely he first made that one piece of iron / steel by fire welding smaller pieces.
How do I know this? From reading a few short remarks in the few contributions related to the topic that I could find in theNet. The picture below attests to this:Development of the complexity of the Japanesesword blade
Large picture
Source: http://ohmura-study.net/994.html.This is not the original source
but a student paper without recognizable references (parts were
written in Japanese). I could not find the source of the original picture.

Iron, Steel and Swords script - Page 577

Early single-piece blades are not of much interest to us at this point, so let's go for the more complex ones with apiled construction. That implies that you need at least two different kinds of steel. European pattern welded blades,
for example, used carbon steel and phosphorous steel but the Japanese, being lucky, did not have to put up withproblematic phosphorous steel. They thus needed to separate high and low carbon steel from the blooms they got.
In Japan there was a tatara bloom and the smith (or his co-workers) now needed to do this:
1. Sort bloom pieces into low carbon (wrought iron) and high carbon ("tamahagane"). If you have that, you canmake "medium" carbon steel yourself.
2. Fire weld the small pieces into a large one and faggot the large pieces extensively.
If all goes right, the smith was now in possession of two largish and halfway homogeneous lumps of different steels.
The decisive part of the first point was to find the tamahagane, the "noble steel, which is spelled as mother of metal in
Japanese characters". Tamahagene is the high-carbon steel that is needed for making the hard parts of the blade. Good
tamahagane contains around 1% - 1.5 % of carbon. That is a relatively large carbon concentration; too large actually forthe blade to be. The extended forging, however, will lead to a reduction of the carbon concentration and you must startwith concentrations higher than what you want to have in the end.
I have already pointed out in detail that a bloomery is likely to produce carbon steel but not necessarily high -carbon
steel. If conditions were chosen to encourage high carbon steel production, there was always a risk that the furnace
would switch to producing (useless) cast iron. Indeed, there are reports that (undesirable) cast iron can be produced in atatara, and that you have to pay close attention while running it for avoiding that.
Getting medium and low carbon steel was easy in comparison. That was the major product of the "civilian" iron industry;
you just bought it or found it otherwise. I'm rather sure that the Japanese were running many "normal" bloomeries
parallel to tataras to produce that every-day commodity.
Now let's assume that a successful smelting has been done in a tatara furnace and that a huge bloom wasproduced. The blade smith (or his commercial partner) now needs to bang off pieces with high carbon concentrationand possibly also some with low concentration. How is that done?
Well - I don't know for sure but from what is written and a bit of logic, a number of points emerge; see also themodule "tricks of Smiths":
Experience. You just know that the high-carbon tamahagane is on the outside of the bloom, forming part ofthat jagged ridge you see in the pictures above. Medium and low carbon than is found in more central
regions.
Looks . There are differences in what the stuff looks like. I have no idea of what to look for myself but here
are some pictures of tamahagane:

Tamahagane pieces
Source: Internet at large

Iron, Steel and Swords script - Page 578

Hardness . Bang away with your hammer. Hard steel -surprise! - is harder than soft steel and you feel that.
Brittleness. Steel with 1 % or more carbon is perfectly brittle. It will hardly change shape but will fracture if
you bang it hard enough.
Fracture surfaces. If you managed to fracture a steel piece, the fresh fracture surface looks somewhat
different for high or medium carbon concentrations.
Specialities. Maybe the colorful parts in the tamahagane pictures above are not seen in the other steel
kinds? Maybe tamahagane rusts a bit more quickly than the low carbon steel when you sprinkle somevinegar on it? I have no idea myself about that but feel certain that there are some more tricks known to the
cognoscenti.
All of these points apply to working with the bloom right at its place of production, possibly while it is still hot. The
smith, after he has obtained pieces with a supposedly known carbon concentration, has a few more ways to checkif everything is right:
Beat your supposed tamahagane into a thin sheet, then break it into small chips. You will experience "fiveways" of breaking: 1. Difficult to break; just deforms. 2. Breakable with some effort. 3. Easy to break and thefracture surfaces are smooth. 4. Easy to break and the fracture surfaces are rough. 5. Brittle, shatters into
many pieces. Now you have sorted five grades of steel, from mild steel to brittle high-carbon steel.
Throw hot pieces into cold water and watch what they do. High carbon steel may shatter. Try the hardness
after quenching with your hammer and do fracture tests once more. Medium and high carbon steel haveturned into martensite and are now brittle.
The essential part, once more, was the high carbon steel, the tamahagane. The softer steels could also be obtained
from other sources, even scrap iron would do:

What Miyairi Akihira (1913-1977), sword smith andliving national treasure when the pictures were taken,
used to forge a blade
Source: Samuraisword.com.

Of course the ancient smiths didn't look for low or high carbon steel; they didn't know a thing about carbon or martensite
after all. They looked for "tamahagane" and whatever they called the other stuff, for materials having the properties theyneeded for forging a blade in their particular way. With plenty of experience they could do a sorting process quite well. I
would be very surprised, however, if there wouldn't have been occasional glitches.
In any case, the smith had now piles of little pieces of the various steel kinds. What he needed to do now was to:
1. Hammer weld these small pieces into a bigger one.
2. Homogenize the bigger pieces by faggoting.
Yes! Faggoting! That's what the repeated folding, welding and stretching is called in English. There is no need to callit "orikaeshi tanren" (Japanese) or "gärben" (German) when you write in English. The link tells you all there is toknow about faggoting. Faggoting was not invented in Japan and the only question around this process is how thesmiths achieves almost perfect weld seams, considering that the "theory" of fire welding seems to be more difficult
than the practice. I have dealt with that extensively so I won't repeat it here.
The Japanese blade smith piled rice straw or rice ash on the pieces to be welded and / or dribbled clay water onthem before welding. I can't see what good that does but then I'm in no position to tell a smith who actually can dofire welding that he isn't doing it right. Since quite a number of Japanese smiths are forging sword blades right now,there are plenty of pictures in the Net. Here are some:Iron, Steel and Swords script - Page 579

Miyairi Akihira (1913-1977), living national treasure
when the pictures were taken, forges a blade
Large picture (with additions)
Source: Top: Samuraisword.com.

You faggot or fold about 10 time, possibly changing the folding directions in between. Ten foldings would give you
1024 layers as we have asserted before. In a blade that is 5 mm thick, the distance between the layers then isaround 5 µm, just about visible in a high-powered optical microscope. Filing into the blade at a shallow angle will"magnify" the distance between the layers: about 10-fold for an angle of 5o and about 30-fold for 2o. Now you can
see the layers with the "naked" eye!
For 6 times folding you get 64 layers at a distance of 78 µm, and 14 foldings yield 16.384 layers 0.17 µm apart. So
around 10 foldings are fine. Your steel will be rather uniform after that but you still could see a structure on theblade, the "hada".

Top: "Hada" in cross-section after 16 layers are folded
Bottom: Various "shallow angle" hadas in actual
blades
Source: Top: FUKUDOME Fusayuki's Japanese Swordsmith Workshop.
Bottom: Meiboku.info site.
Iron, Steel and Swords script - Page 580

The smith can manipulate the hada by making the layers less regular. Fold this way and that way, make the surface
uneven by uneven hammering, and so on. It is quite similar to what wootz sword smith can do.
But I'm getting ahead of myself. We haven't made a blade yet. What we have are two or possibly three bricks ofhigh, medium and low carbon steel, fairly uniform with respect to the distribution of carbon, slag particles andwhatever else is in there due to the faggoting. Slag particles also tend to be small because all that hammering brokethem into many small pieces.
The medium carbon steel brick we might have made by piling low carbon and high carbon sheets, fire welding andfaggoting. The carbon concentration after 10 foldings will have averaged quite nicely to medium.

1)

Here is a rather recent article of Tatsuo Inoue: "Tatara and the Japanese sword: the science and technology", Acta Mech
214, (2010) pp. 17–30

Iron, Steel and Swords script - Page 581

11.6.3 Making a Japanese Sword - Part 2
Forging the BladeYou're a Japanese sword smith around 1500 or so. In contrast to your European counterpart, you are not seen as an
undistinguished dirty craftsman but as an accomplished expert and artist, sort of. You were on level three of the social
ladder (level 1 were the samurai, level 2 the peasants) but one above the merchants and bankers! Ain't that nice? Of
course, your local daimyo or overlord would chop your head of in less time than it takes to say f*** if you just looked at
him the wrong way. He used that extremely sharp sword you made for him for doing that. But as long as the headstayed on life was good. As far as it went.
Now you are in the process of forging a new sword. You had already made three blocks of well-faggoted high, medium
and low carbon steel and now you would use these blocks to produce a new katana with superior quality.
First you need to make a decision. How are you going to pile the ingredients for your blade? The softer steels
inside, the hard one outside, of course, but there are many ways you can do that - if you are a Japanese smith or
believe in Japanese mythology, that is.

Various ways of making a Japanese sword blade bypilingthree grades of steel according to Japanes sources
Source: Basic drawings of this are all over the Net

Masamune (c.1264–1343), the most accomplished smith of Japan, supposedly made the most complex sword
blade, soshu kitae. Of course. Maybe he did; I just couldn't find any proof of this claim. Not to mention that I wouldfind it hard to believe that the complex "Soshu Kitae" way of piling offers any advantage relative to the less involved
ones. Asking if the "orikaeshi sanmei" kind of piling is better than the "soshu kitae" or "gomai" is like asking if a
Renoir painting is better than one from Cezanne or Monet.
To some extent we are back to the myth. "The vast majority of historical blades were kobuse construction (softcore, hard jacket), followed distantly by san mai (hard edge, soft spine, medium jacket), followed very distantly bymaru (solid). Other construction methods are relatively rare and were the result of experimentation, various pseudoscientific theories (there was no deep scientific understanding of metallurgy after all), traditionalism, etc. Some ofthem are arguably apocryphal, like Soshu-kitae" writes an unidentified but obviously knowledgeable source in an
Internet forum.
Iron, Steel and Swords script - Page 582

I won't challenge you now to make a "Soshu Kitae". You (and I) do not really know how to do that and as far guessing
goes, you can do that yourself. Let's make a kobuse instead. No European smith around 1300 or even 1000 plus years
earlier would have had a problem doing that.
So first bang your steel "bricks" into roughly sword blade shape. Two from hard steel and one from soft / medium.
Then laminate a somewhat wider piece of hard steel between two pieces of softer one.
Yes, that would work but the Japanese did it in a slightly different way. They first forged one piece of "brick"tamahagane into a "V" shape and then inserted the softer steel into the gap. Then you fire weld the package andhammer it out into the desired shape of the blade. Well - not quite. You actually curve the blade a little less thandesired since the quenching produces additional curvature.
Before you quench, you must semi-finish the blade by filing and grinding since you can't remove much material after
quenching. What you do is "case-hardening"; only the outer layers will be affected and if you file them off later you
got a problem´´

Forging a kobuse style Japanese sword
Top: The basic idea
Bottom: the real thing
Source: Michael Morimoto, Colorado School of Mines. "The Forging of aJapanese Katana", June 14 th , 2004

Quenching the Blade
Rapidly cooling steel with at least 0.3 % of carbon or so produces very hard and brittle martensite instead of medium
hard pearlite plus soft ferrite. Read it up! Quenching a 1% carbon or so tamahagane steel easily brings you in the 800
Vicker's hardness region. Turning the whole tamahagene of your kobuse style blade to that kind of hardness plus theconcomitant brittleness would not be so good, however. You only want the edge to be ultra-hard, compromising for theunavoidable brittleness, but the rest should not be brittle.
It is clear what you need to do. Just quench - rapidly cool - the edge part and allow the rest to cool down more
slowly. Given the cross-sectional shape of your blade that will happen automatically to some extent. Thicker parts
unavoidably cool more slowly then thinner parts, just as the outside cools down more quickly then the inside. Thereis a what is called a hardness depth, after all.
Plunging your hot blade into cold water thus will never turn the inside hard and brittle but quite possibly more of theoutside than what you have in mind. You need to do something. What you do for your steel is exactly what you dofor yourself when you don't want to cool down too quickly getting out from your warm house into a very cold winterday. You wear protective clothing that acts as a barrier or thermal insulator, decreasing the heat flow from yourwarm body to the cold air.
You do exactly the same for your blade. You protect the areas not supposed to cool down too fast with a thermal
insulator. Goose down or coyote fur, however, will not do in this case since that stuff cannot take the heat. Ceramics are
better, in particular because you can easily coat your blade with some pasty clay stuff that fires into a ceramic as soon
as you heat up your blade. You are doing some special kind of of pottery. You even can influence the local cooling rates
by varying the thickness of you protective clay layer. The thicker the layer the slower the cooling. What you are doing
now is known as differential cooling.
Iron, Steel and Swords script - Page 583

It is of course not quite as easy as it sounds. Your clay paste must have the right properties, like sticking well tothe blade, firing well, and so on. Then you must not only heat your blade well above the A1 transition temperature of
727 oC (1341 oF), the blade needs to have the same temperature everywhere. That calls for a rather large and welltended hearth plus experience to substitute for the lack of thermometers.
Then you may encounter a little paradox: Those parts of your blade that are coated with just a thin layer of clay willcool even faster than the bare blade! That's like wearing metal clothing - you get cold faster than with no cloths atall! Why? Well, when you stick something very hot into cold water, the water will start to boil right at the hot
surface. Air bubbles are produced. Air bubbles are terrific thermal insulators, preventing rapid cooling. On a clay
surface the bubbling is different than on a metal surface and less air bubbles may speed up the cooling.
The composition, size and temperature of your quenching bath is also of some importance. It is not quite asimportant as the smiths of old believed but of some importance nonetheless.
So quenching was a tricky process that might have been left to a specialist. In return it offered a number of good
points:1. The edge can be made ultra hard. It will also be brittle but its "attachment" to a ductile body allows you tolive with that.
2. The edge can be made ultra sharp and it retains its sharpness as long as you don't hit objects harder thanitself.
3. Other parts (e.g. the back) can be much softer, allowing to absorb impacts from other swords more easily.
4. The quenching process induces some additional bending of the blade, making its shape more "perfect".
5. "Painting" on the clay paste with a certain shape of the transition region between thin (fast cooling) and thick(slow cooling) areas produces a hamon with a certain shape or pattern that provides for beauty and a kind of
type-signature on your blade.
6. The quenching process leaves residual stress and strain in the blade. This can make the edge stronger for
cutting.
The first three points are sufficiently clear by now. The others need some explanation. Let's first look at point 4 insome detail; point 5 will emerge from this.
So why should quenching induce some additional bending of the blade? That is a tricky question. There are several
reasons for this that all work together. Understanding the basic processes is easy, understanding the details is rather
difficult.
In order to grasp what is happening, imagine a small cube somewhere inside your hot blade, ready to be quenched. It
contains a number of iron atoms arranged in the face-centered cubic (fcc) austenite lattice and some carbon atoms
according to what kind of carbon concentration you have at the point you have chosen. Now let that little cube cool down
to room temperature and watch what happens to it, always keeping the same number of atoms inside. There are twobasic phenomena that will try to change its size
1. As it gets colder the cube will want to shrink in size. That is just the opposite of the well-known thermal
expansion, the observation that all materials expand when they get hotter. When they get colder they contract.
2. As the blade gets colder we have a phase change, the atom arrangement inside the cube will change. For regulariron there is the switch-over from the fcc austenite where the iron atoms are most closely packed, to the moreloosely packed bcc ferrite. That means that the cube must now expand somewhat. If you have carbon in in there
too, you also get some cementite now but that does not change the basic picture: the cube expands
We have two unavoidable effects that will tend to change the dimensions of your blade - and they oppose each other.
That is a nuisance but also a great thing! We have used that already to our advantage for experimentally establishingphase diagrams by a method called dilatometry
But now we must look at complications induced by quenching a katana blade. There are essentially four:
1. The phase transitions occurring in a quenched katana will also produce martensite besides ferrite andpearlite. While that also calls for a volume change, it is different from that of the other phase changes. It also
happens later, at lower temperatures.
2. If the volume changes in different parts of the blade are different at a given time as in the case above, theblade will now be under stress and must deform. If, for example, the edge regions wants to expand more thanthe back region, the blade must bend into the katana-shape direction.
3. Volume changes will also be different if the temperature is different in different parts. While the edge area isalready cold and thus wants to contract quite a bit, the back is still hot and wants to contract less. Thermal
stress develops and the blade then is forced to bend into a more concave "yatagan" shape.
4. The total stress at any given point and time is the sum of the thermal stress and the phase change stress. It
can become rather large in certain places at certain times. If it exceeds certain local limits, plastic
deformation or fracture will occur.
Note that many of this complications do not apply to double-edged blades with asymmetrical cross-section. The cold outside of the front part will also tend to bend
the blade relative to the still hot inside. But the backside, just as cold as the front
side, wants to do the same amount of bending - but in the opposite direction. The
stress introduced by both cold surfaces cancel each other and no bending will beobserved. It's not quite that simple but definitely far simpler.
I have discussed this before in some detail and I gave you the long science module.
Iron, Steel and Swords script - Page 584

the blade relative to the still hot inside. But the backside, just as cold as the front
side, wants to do the same amount of bending - but in the opposite direction. The
stress introduced by both cold surfaces cancel each other and no bending will beobserved. It's not quite that simple but definitely far simpler.
I have discussed this before in some detail and I gave you the long science module.
If you read it or not - by now it should be clear that what is going on inside theblade during quenching, in terms of stress, strain and deformation, causing theblade to bend, deform or even shatter, is rather complex and not given to simple
back-of-the envelope calculations. You need to use the front of a largish envelope
and a big computer.

Science Link
ThermalstressThat's what Tatsuo Inoue did and here are some results:

Shape and temperature development of an initiallystraight
katana during quenching
Source: Inoue

Starting form a straight blade the curvature first is concave before it turns around for the final convex shape. Whythat happens is rather clear in principle. Of course, the details depend on many things: what kind of clay, how thickexactly, the kind of quenching fluid, the volume of the fluid (a large volume will no heat up as fast as a small one) ,and so on.
I'm also not sure if Inoue took into account that the soft core might undergo plastic deformation, a process hatchanges the stress distribution. I would even guess that a soft core is necessary to avoid fracture during quenching.
I have reasoned about this in detail here, so I won't repeat myself.
Quite a lot is going one during quenching a katana (or any other single edged blade). We understand it now but for theold smiths this must have been pure magic. If all went well you got a very hard edge formed by rather pure martensite,
followed by a transition region from martensite via bainite to pearlite. The transition region could be made visible quite
well by proper polishing, meaning " special Japanese polishing" in this case. Your blade now showed a hamon:

Examples of real hamons and four drawings (out of27) used to classify hamons
Source: Commercial sword selling sites; all over the Net

Iron, Steel and Swords script - Page 585

Is the wavy type of hamon better than the more straight one? That's like asking: is red better than green? So let's
not go deeper into this. A hamon adds beauty and complexity to a blade, what exactly that means is in the eye ofthe beholder. There are undoubtedly persons out there who could tell off-hand what kinds of hamons are shown
above, for what kind of period and smith they are typical, and so on. It's a great thing to be able to do this eiterh
professionally or as a hobby. It's just not materials science but rather something like art history.
Is the differential quenching procedure a typical and unique feature of Japanese swords? Do other swords have ahamon? Is the alleged superiority of the Japanese sword embodied in the hamon?
As far as wootz swords are concerned the answers are clear. They are not quench hardened because they are
already very hard throughout and the heating before quenching would destroy their unique structure. They cannot
have a hamon, not to mention that a hamon would destroy the beauty of this blade type. If a Japanese sword issuperior to a wootz blade is open to doubt, however.
As far as European blades are concerned, the situation is not so easy. Nobody has seen a hamon on surviving old
European swords but that doesn't prove that there isn't one. The blade simply may not have been polished orotherwise conditioned to show its hamon.
So let's do a Japanese polish on an old European sax blade. Here is what you get:South German sax from 600 AD - 750 AD after
Japanese polishing
Large picture of whole sax
Source: Stefan Maeder's thesis

That's just another picture of the sax shown in the faggoting module. We can also be pretty sure that some Romanswords would have shown a hamon, given their cross-sectional structure with hardness values. The same is true forsome Moravian swords.
The major ingredients for producing an European variant of the Japanese sword - faggoting, piling and quenching were well known in Europe already during Celtic and Roman times. We have, however, almost no metallurgical data
for whole blades and not too many for cross-sections. If clay coating before quenching was known and used is thus
simply not clear at present. In any case, we can be pretty sure that some European swords were just as good astheir Japanese counterparts for the same time period and much better in earlier times.
It remains to consider point 6 from the list above: the quenching process leaves residual stress and strain in the blade.
That is easy to see given the "bending" picture. Whatever is going on inside the blade during quenching, in the end it
wants to bend into a convex shape. That results mostly from the need of the martensite of the edge to expand a bit
more than the rest. To do so necessitates to squeeze the back but the relatively small volume of the martensite edges
will only be able to compress the voluminous back to some extent and not as much as needed. That means that themartensite is not as relaxed as it wants to be but still somewhat compressed:.

The edge of a Japanese sword isunder compressive stress

Iron, Steel and Swords script - Page 586

Is that good or bad? Good question. Consider a spring that you can pull out or compress a certain length before it
breaks. Now put some mechanical "´bias" on it, for example a fixed weight. The spring will expand somewhat and is
now under tensile stress relative to its unbiased state. What that means is that you now need less force or stress toextent it to the length were it will break but more to compress it to the crucial size. If you bias the spring into
compression, it is the other way around.
The edge of the katana is under compression, meaning it takes more force to increase the curvature of the sword(=making the edge longer) relative to a stress-free edge to the breaking point. The same for the back, just with thesigns reversed. In a bending test in the right direction your katana now appears stiffer. If you hit something hard, thecurvature will also increase. Your katana with the built-in stress will then bend less than it would in a stress-freestate. That might be good.
However, the forces acting on your edge in a real sword fight are not exactly parallel to the edge, trying to make it
longer. It is far more complicated than that. After all, when something hits your edge it will tend to compress thematerial at and near the point of impact and stretch the material farther away. If the edge is already undercompression, it takes less "bang" now to compress it to the critical value where something will give. That is bad.
So, all things considered, is the internal stress in Japanese swords (and others) good or bad on average? I have aclear answer to that: I don't know!

1)

Tatsuo Inoue: "Tatara and the Japanese sword: the science and technology" Acta Mech 214, (2010) pp 17–30) D

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11.6.4 Metallurgy of the Japanese Sword
Materials and Processes
Japanese smiths made Japanese swords or nihonotos exclusively from bloomery iron and steel. That business started
around 1000 AD and was kept up with only small interruptions until the present day. Bloomery steel only! That is thefirst special point from a metallurgical point of view. Why? Well - consider:
The Koreans and Chinese neighbors to the West, supposedly the people from whom the technology wasborrowed, made their steel from cast iron already more than 1000 years before the Japanese started to makenihonotos. At least the Chinese did; about the Koreans I do not know anything.
The Indians, even more to the West, made their swords from crucible steel also long before 1000 AD. The samecan be said about parts of Central Asia.
The Europeans did work with bloomery iron in 1000 AD but switched to blast furnaces and a cast iron based
technology in 1300 and beyond.
The katana started to become prominent in the 15th century and at that time almost nobody besides the Japanese
made swords still from bloomery iron and steel. That means that Japanese swords still contained inclusions of slag andwhatever else trapped in a bloom. Moreover, a bloom is always rather inhomogeneous with respect to the carbon
concentration (and anything else in there). Working with a bloom was always a problem, and keeping up with theadvanced competition, however remote, then necessitates special measures:
1.
2.
3.
4.

Optimization of the bloomery process to minimize the "dirt" always encountered.
Optimization of the bloomery process to produce high-carbon steel, the difficult thing to produce with a bloomery.
Finding ways to asses and classify the needed steel grades (low, medium, high carbon).
Extensive faggoting to homogenize the always non-uniform bloomery steels. That, in turn, requires the ability tofire weld with near perfection.
5. Some luck.
Everything else needed for making a Japanese sword is more or less independent of the steel production process. The
differential quenching technology with the clay coating and all, would be the same for a blade piled from cast steel, forexample.
The first two points are covered by the "invention" of the tatara furnace. It obviously could do the job. There might havebeen better ways to deal with the first two points but the tatara worked. It was an expensive and not very efficient
process but so what.
A tatara could and would produce cast iron 1) . From what I read I would guess that it might have contained molten
steel too on occasion and that would account for almost slag-free "tamahagane ". European smelters had also beenable to produce high carbon steel in their bloomeries but we do not know all that much about these bloomeries andhow they were run.
Point three applies to all smiths working with structural and compositional piling. What the Japanese smiths did toassess their steel is relatively clear, I have already dealt with that. A bit more about the "tricks" of the smiths can befound here.
I'll deal with point 4, faggoting, below but before I do that let's look at point 6: some good luck is needed!
Being lucky is essential. On the one hand, the Japanese had tough luck since they do not own a whole mountainmade from decent iron ore like the Austrians or Svedish. On the other hand, their "iron sands" are virtually free ofphosphorous and sulfur. This is just good old dumb luck that compensates for the lack of iron ore mountains.
Let's have a quick look at the "West" for comparison. Large advances in bloomery techniques were made around 1000
AD, give or take century or two, and that allowed to replace the (expensive) pattern welded sword by the better andcheaper piled all-steel sword. While there may or may not have been some imports of high-carbon wootz steel to makethe "true" +VLFBERH+T" types of Viking swords, self-made high-carbon bloomery steel was definitely around in Central
Europe, witness the "Moravian" swords and many others. The trick seems to have been to run your bloomery at hightemperatures while avoiding to produce cast iron. Details, however, still evade us (at least me).
Faggoting was also know in the West. However, we hardly know anything about that since the number of old swords
metallurgically examined to determine if and how faggoting was done is close to zero. I'm only aware of Stefan
Maeder's work in this direction. I have (convincingly!) argued, however, that elaborate pattern welding simply
makes no sense if you didn't faggot your steel before you used it.
The situation in Japan is as different as it can be. Assessing the quality of Japanese blades from 1000 AD onwards
included looking at the "hada", the visible structure on the blade that results from faggoting. I have dealt with that
already. It would be premature, however, to conclude that "the Japanese" were better at faggoting than everybody
else. Here is a comparison:

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Left: Japanese faggoted steel from the 20th century.
Nital etch
Right: 300 BC Celtic Sword from La Tène. Japanesepolishing
You need to be aware of the fact that this is a completely random comparison! The Japanese sample comes from the20th century Japanese sword smith Shimizu, who left it for analysis. It is not yet a finished blade but close to thatstage. The investigation of this sample was done by Jang-Sik Park in 2004 1). He used classical metallography,
polishing followed by Nital etching, to reveal the structure.
The Celtic sax was investigated by Stefan Maeder; I have used this picture before. In this case "Japanese polishing"
was used to reveal the structure. Of course, these two samples cannot be seen as representative for untold number ofswords forged during 1000 years or so. And yet! They do show that faggoting was used in both cases and that there aremany similarities.
There are simply not many other pictures like that. There might be a few around that I'm not aware of but there aren't
many for sure.
What we see is that the steel is not even remotely homogeneous, despite faggoting. There is a layered structure
and that means that something is distributed in a layered fashion. It might be the carbon concentration but withmore folding and thus smaller and smaller thicknesses of the layers, the carbon concentration would eventually evenout by diffusion. It thus stands to reason that we see weld defects, small particles and the like, that are in found in
the weld seams. In fact, there are a lot of sharp dark "dots" visible that could not have resulted from a carbon
concentration gradient.
Faggoting means fire welding every time you fold. Doing that you cannot completely avoid getting some "dirt" like oxide
inclusion into your weld seam, and you may have occasional other weld defects. Every folding increases the number ofthese defects, and every stretching draws them out. Drawn out defects like oxide or slag inclusions may break up into
strings of small particles. Very schematically, things proceed like this:Iron, Steel and Swords script - Page 589

Folding, stretching and defects in the weld seam
Faggoting with 10 foldings or even more then demands high welding standards; otherwise you defy the purpose.
However, welding will never be perfect and the small defects in the seams will produce the faint pattern you actually see,the "hada" or whatever. In other words: The fact that you actually see something on a Japanese blade is a sign for asomewhat non-uniform, a somewhat imperfect material. A homogeneous and well-polished steel is simply free of any
structure that you could see without a microscope. Nevertheless, Japanese smiths certainly had mastered fire welding
as well as everybody else. I wonder how they solved the problems I have listed here.
Metallurgical Investigations"In contrast to the reputation of the Japanese sword, however, not much attention as been paid to the dynamic evolutionof its microstructure on its way to be manufactured from the tatara ingot" writes Jang-Sik Park in 2004. "There are a few
references written in English (to the metallography), unfortunately. Further, the precise metallurgical characteristics ofJapanese sword have not been clear yet" writes M. Yaso et al. 2)
It certainly appears that they are right. I have yet to see cross-sections that clearly show one of the more complex
constructions in the claimed variety of styles.
As far as the simple constructions are concerned - one piece (maru), soft core, hard jacket/edge (kobuse) and hardedge, soft spine, medium jacket (honsanmai) - what do you expect? Hard edge martensite will look like martensite,
medium jacket steel will be pearlite, and soft core steel will go into the ferrite direction.
Points of interest are rather:
How many inclusions of slag and other defects are observed. How did this develop from 900 AD to thepresent day?
How was faggoting done and how did it develop?
Here is one pictures showing that a Japanese sword form around 1400 had plenty of inclusions:

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Slag inclusion in a 2nd generation Muramasa sword
from around 1400.
Source: M. Yasoa, et al..

The specimen was taken from an old sword which was produced by the 2nd generation of Muramasa about 600 years
ago. It had been hardened as demonstrated here:

Hardness via distance from edge for 2nd generation
Muramasa sword
Source: M. Yasoa, et al..

It is not clear, however, if hardening with a clay coating has been used; no mention of the hamon is made. It is also
not clear if piling was used and what kind. The pictures given do not show faggoting. The authors refer to faggoting
though, but in a nonsensical manner ("The grain size of sharp edge part is observed to be very fine, about 10-15 µm
as a result of the effect of 10 several times-forgings in sword making process").
The microstructural pictures provided in 2) show essentially pearlite outside the martensitic regions. Since a
hardness value of 800 can be reached with eutectoid or even somewhat hypoeutectoid steel, it is possible that thisblade was actually made from one piece of (0.6 - 0.8) % carbon steel.
I'm not saying that this is so. I'm saying that we have far to few studies and that the ones we have do not address,
not to mention answer, some of the open questions.
As far as fagoting goes, the picture above is one of the few I know of. From the same paper we have a few more picturesof some interest. They show that stage in the forging where the smith has fire welded a number of tamahagane pieces
and possibly folded them over once:

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Top: Broken up and banded cementite in a plate oftamahagane fire welded from a number of smaller
pieces.
Bottom: The fine structure of the cementite particles
and the pearlite in between. Note change of scale
Source: M. Yasoa, et al..

What you see is that all this hammering and flattening does not only make up the cementite as one would expect
but lines up the fragments, producing a striated or banded structure. That is not necessarily what you would expect- except, perhaps, if you have read the little module about banding, written in the context of wootz swords.
That reminds us of the basic truth that is at the core of this Hyperscript:
The mind-boggling complications of iron and steel engineering gives us all these different swords, objects of supremeterror and beauty, embodying the powerful principles of learning by doing and mastering the manifold complexities ofyour trade. But all of this pales before the magnificence of a few simple principles of science, whose beauty and power
far outshine any katana, shamshir or pattern welded spatha.

The End 3)

1)

Jang-Sik Park: "Traditional Japanese Sword Making from a Tatara Ingot As Estimated from Microstructural
Examinations", ISIJ International, Vol 44 No6 (2004) pp. 1040 - 1048

2)

M. Yasoa, T. Takaiwa, Y. Minagi, K. Kubota, S. Morito, T. Ohba, A. K.Das: "Study of Microstructures on Cross Sectionof JAPANESE SWORD", Proc. ESOMAT 2009, 07018 (2009)2)

Sort of. It is the end of what I have to say about swords and material science. There is one more chapter, however,deailing with the physics of wielding a sword.
There also might be sequels. You might see that as a threat or a promise.

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12. Properties of Swords
12.1 The Basics
12.1.1 Sword Performance

12.2 Static Sword Properties
12.2.1 Sword Bending: Purely Elastic
12.2.2 Sword Bending: Deformation and Fracture
12.2.3 Sword Buckling12.2.4 Sharpness
12.2.5 Sword Types and Static Properties
12.2.6 Static Properties of Composite Swords
12.2.7 Experimental Tests of Old Steel and Swords

12.3 Dynamic Properties
12.3.1 Moving a Stick12.3.2 Center of Mass
12.3.3 Translational Movement
12.3.4 Rotational Movement
12.3.5 Moment of Inertia
12.3.6 Translational and Rotational Movement
12.3.7 Percussion Point
12.3.8 Vibrations

12.4 Wielding Your Sword
12.4.1 The Effective Mass or Apparent Inertia
12.4.2 Dynamic Properties Combined
12.4.3 Hitting Something
12.4.4 Impact
12.4.5 The End

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12. Properties of Swords
12.1 The Basics

12.1.1 Sword Performance
How a Swordsman Looks at Sword Performance
What defines the quality of sword? If we consider its fighting value and not its prestige value, it can only be its
performance in a sword fight with another sword bearer. Swords for showing off or for hacking defenseless people into
pieces need not to be particularly good and thus are of no interest here.
John Clements, an experienced swordsman, made a list1) for essential swords properties, here are the major points:
Cutting Ability
Thrusting Ability
Guarding Capacity
Speed
Technical Versatility
Durability
John discusses these points by comparing a Japanese katana and a medieval longsword. Let's look at his points one byone, to some extent in John's own words.
Cutting ability: This is the blade's capacity to deliver powerful shearing and cleaving edge blows. The katana, with
its living tradition of practice, is well known for demonstrating its cutting power. Its single, hardened, wedge-likeedge has long been shown to be capable of extraordinary sharpness.
The longsword, has not acquired a similar reputation. It is certain that both weapons successfully faced opponents
wearing soft and hard armors without great difficulty. Nonetheless, a curved blade is mechanically superior to astraight one at delivering edge blows to produce injury. And due to its hardness, the single curving edge of thekatana is very good at penetrating even hard materials with straight-on strikes. Verdict: Katana.
I wonder why John does not consider wootz blades, also famous for extreme sharpness and cutting power. From a
metallurgical point of view, you don't just want a sharp edge, you want it to stay sharp when you hit something, andyou want it not to break. That calls first for a hard material, and second for a material with the ability to disperse a
considerable amount of energy released in a small area / volume without fracture or much deformation. That
necessitates a large "fracture toughness" and thus a material that is first uniform and free from small defects likemicrocracks or micro-inclusions and, second, somewhat deformable or ductile and not completely brittle. No steel
offers both properties equally well, so for cutting ability alone you tend to go in the "ultrahard but somewhat brittle"
direction, i.e. for a katana.
Thrusting ability: This is the capacity for a weapon to make penetrating stabs with its point. Whether against
armored or unarmored opponents, a thrust has long been recognized as more difficult to defend against, easier todeliver a fatal wound with, and quicker and farther reaching than a cut. As has been known since ancient times, thegeometry of a straight weapon means its thrust hits more quickly and deceptively than does a curved or semi-curved
one. Verdict: Longsword.
Guarding capacity: This is the weapon's ability to be moved to ward, parry, and block the assorted strikes of otherweapons it had to face in combat. Its design affects the physical mechanics of how the object can be wielded
defensively and the resilience and toughness of the blade is a component in this. All things being equal, the inherent
defensive potential then comes down to the tool's geometry, or shape. Verdict: Longsword.
Much of what John relates here (and I have considerably shortened it) also applies to the 4th point "speed".
Speed: Speed is the velocity at which any hand-weapon can perform defensive and offensive actions to deliver hits
or impede blows. The quickness of a hand-weapon depends partially upon the user's own prowess, as the weapon
itself does not move, the swordsman moves it. Since the relative weights of both sword types are nearly equal, theissue comes down to the geometry of how each can be moved. A shorter curved blade can slash more quickly, but
a longer, narrower, straight blade can certainly thrust more quickly. The slashing cut of a shorter curved weapon
wielded in strong fluid motion can be more maneuverable than the less oblique cuts of a longer straight blade
similarly used. Verdict: Katana.
Technical Versatility: This is the mechanical utility the weapon has for being employed in distinct offensive anddefensive actions. Surely the most controversial category to rate any sword on is its fighting capacity. The katana isthe extreme single-edged cutting performer while the longsword is an excellent multitasker. Both are capable ofnumerous slashing, slicing, and stabbing techniques. Both weapons utilize counter-striking and defensive
displacements. However, straight double edges permit cutting along 16 different lines of attack compared to eightwith a single-edged curved blade. Verdict: Longsword.
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Durability : Durability in a fighting sword refers to its general tenacity and its resilience and in delivering blows andreceiving impacts over time without breaking or becoming bent. The more resistant to brittle catastrophic failure asword blade is, however, the more malleable it becomes - meaning the easier a bend will set in.
The katana required more rigidity for its hard-cutting design, while for its utility the longsword was more of a spring.
The katana's edge leaned towards more brittleness while its spine was more prone to bending. In both weapons,
cross sectional shape compensated for weaknesses while capitalizing on strengths. Flexibility, or the ability for a
blade to deform but return true, though regularly exaggerated in modern times, was actually of very little concern for
swords intended for serious combat, and does not enter into the criteria here.
No sword is indestructible. All are produced as perishable tools with a certain expected working lifetime. Whichblade historically could possibly be called the more durable in combat is then an exceptionally complex issue toaddress and perhaps unanswerable. Verdict: Unknown.
Those points are important for the user of a sword. However, they leave the materials scientist or even the maker of asword somewhat puzzled. How can you grade these properties? That means you must produce a number, that comesfrom an objective measurement. How are you going to do this?
The answer is simple: you won't. The properties expressed in the key words above relate to many "technical" aspects ofswords and to "properties" of the person wielding it and there is no way to measure those properties objectively without
involving human opinion. A violinist will find a Stradivari or Guarneri violin far superior to "normal" ones but scientists
cannot tell how the small differences they might find by making all kinds of measurements relate to the judgement of theexperienced users.
My point there is that what counts is the judgment of the user. Nothing will convince him to use the "scientifically"
superior sword if it doesn't feel right to him. And that's as it should be.
However, since I'm not a user of swords, I only can give you the science point of view. Happily, we are in asomewhat better position than the musical instrument guys. Science will be able to come up with some points that
do relate rather directly to the performance of a sword.
So let's look at sword performance now from a scientific point of view. We will distinguish two very basic cases:
static properties and dynamic properties. What follows is a general introduction of the meaning of those terms.
Static Properties of Swords
For starters, you could go back to chapter 3 where I introduced the definition of major static material properties and how
they are measured. Properties like Young's modulus or hardness emerged, and we will need that here. But now we arelooking at static properties of a sword, and not just a homogeneous material. What we do, in essence, is to put a staticor fixed load on a sword at rest all the time and consider how it responds. Look at the picture below to get an idea ofwhat that could mean.
We already know that we can get three fundamental results:
1. The sword deforms elastically. After removing the load it resumes its old shape
2. The sword deforms plastically. After removing the load it remains permanently bend.
3. The sword fractures.
We will only consider the first case for starters.
"Static load" in the most simple version means that you fix your sword at some "point" to something unmovableand then apply forces somewhere. One example of how to do this is shown below.

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Basic sword bending experiment.
Unloaded (top) and loaded in different directions
relative to the blade cross section
Source: Photographed Feb. 2018

A smallsword with a triangular blade was used, the hilt was fixed to a window sill. A (full) beer bottle provides for adefined force near the tip of the blade. The sword bends quite a bit but differently if loaded at right angles to the longside of the triangle defining the blades cross-section (middle picture), or parallel to it (lower picture). I would guessthat nobody is going to be very surprised about the outcome of this experiment. You have a "feeling" for the kind ofcurvatures you get in this case. You also could predict that outcome if I would have used a more substantial sword,
for example a katana: There wouldn't be any noticeable bending.
But that's it. If I now would ask you to calculate the exact curve that the sword assumes, you will not be able tocomply (with some 99.999 % probability). Few are the people who know how to calculate a "bend beam".
Let's generalize a bit. For assessing static properties, we need to first immobilize at least one point of our sword in orderto make sure that it cannot move around or rotate. All it can do is to bend (including plastic deformation and fracture) if
you now apply forces - all kind of forces - on the "free" parts. Under the influence of the forces your sword will assume
some bend shape, and as long as the forces hold, nothing changes anymore. That's what static means: Nothingchanges.
You might, however, slowly increase the magnitude of the forces and watch what happens.
One way of doing that would be the good old tensile test - clamp it and pull. You would not produce a large effect,
however, with a real swords and forces applied by humans. This is not necessarily true for the reverse, compressive
testing; I will get to this.
The natural way to go at it for starters is to immobilize the hilt and than apply a force at a right angle to the bladenear the tip - as shown above.
We will deal with static properties in the next sub-chapter. I will look at:
1. How do parameters of your sword influence how much it bends? That necessitates to consider the basic "beambending" experiment as shown above a bit more closely.
2. How do parameters of your sword influence "buckling", the shape-change if you push straight and at a right angle
at an immobile hard object?
3. What can we say about bending and fracture of a sword (and not just a material)?
4. How do different sword types compare - wootz, pattern-welding, katana, uniform steel, and so on? Moreprecisely: what kind of advantage - if any - do these materials / forging techniques offer?
5. Sharpness and retaining it. That's a static property, too. What has Materials Science to say about that?
Doing that without equations is quite a challenge. Far more challenging, however, is what comes next: dynamic
properties.
Dynamic Properties of Swords
It may come as a surprise that you can look at dynamic properties while your sword is still (partially) immobilized
because the hilt is clamped to an immovable object. The blade, however, can still vibrate. In the simplest way, the tip
moves back and forth with some frequency, in the not-so-simple version a more complex "vibration mode" might occur.
This is seen as a dynamic property, however.
A quick look at the physics of vibrating sword blades will teach you one thing: Forget it! Calculating anything is rather
involved. I will look at vibrations at the end of the next sub-chapter; so let's go for other dynamical properties first.
Dynamical properties emerge as soon as you move your sword. We are going at that in three steps:
1. The sword is moved by forces applied by massless ghosts. In other words, we just look at the basics physics ofmoving an object with a longish shape.
2. The sword is moved by you. Unfortunately you are not massless. And you never just move your sword, but indoing so you always move some part of yourself too. So we have a combined system: a well defined hard object
with a fixed and not too complex geometry that is loosely connected to an ill-defined slimebag with changeable
geometry.
3. The sword is moved by you and actually hits something. All three entities experience forces acting on then: thetarget, the sword, and you (mostly your hands and arms).
This is going to be complicated, make no bones about it! Looking just at the first point, we will first consider straightmotions or translations without rotating the sword. An example could be an ideal thrust as illustrated below (note theghost)!

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Moving your sword
Source: Net; from a 1610 book about fencing wreitten by one
Capo Ferro

But moving your sword without rotating it is certainly not what you do most of the time. Whatever you do, the total
movement of the sword can best be described by looking separately at the two ingredients of that movement:
1. The movement of the center of gravity of the sword along some line in space.
2. The rotation of the sword while moving along.
Look at the picture below to get an idea of what I mean. The ghost of a samurai is at work here. The red line
describes the path of the center of gravity of the sword. The three angles indicated give an idea of the rotation of thesword relative to a vertical l line at the points in question. Note that the sign of the angle changes, this is indicatedby different colors.

Moving your sword
Source: Internet at large

With ghosts at work, this is still easy to grasp.
Now let's replace the massless but powerful ghost by you. At any point in time during the swing you need to exert
specific forces and torques to the sword hilt in order to produce that movement. You do that with your hands but
they are attached to the rest of the body by arms and so on. In making the sword move in a certain way, you moveyour hands, your arms and other parts of your body. To do that, you need to exert proper forces and torques tovarious parts of your body. And you feel forces and torques in your hands, mostly, but also in other parts of you
body.
If you try to make the movement shown above with different swords or with a battle axe, you need to apply different
forces and torques, and you will experience quite different feelings, too. With some swords you may not even beable to make the desired movement, or at least not very fast.

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The forces and torques you experience by "body feel" thus are always a combination of what it takes to move and rotate
the swords plus what it takes to move your body parts. When you swing your old and familiar sword you are so used toit that your body exertions don't register much. When you test a new sword by swinging it around, getting a feeling for
its "speed" and so on (see above), you notice the differences in what your body now has to do relative to what it's used
to. In particular you notice possible limits you might encounter. If, let's say, a swift rotation of 90 o takes and effort of 90
with your familiar sword, with your limit at 100, than a sword that would need a 110 seems "unmovable" to you. In
physical reality the new sword takes only about 20 % more effort for the move difficulty but for your feeling the difference
is much larger. That's why swords that are not all that different from a technical point of view might feel very different toyou.
We now progress to the last and most complex part of sword dynamics: We hit something! Three basic questions comeup in this context:
1. What happens to the object we hit? Think in terms of transferring force, momentum, energy, and how that
impacts the object. What do these parameters mean to the object hit?
2. What happens to your sword? What kind of deformation will it experience? Will it start to vibrate and if so, how?
3. What "feeling" is transmitted to your body? What do I feel, upon impact, in the hand holding the sword? The arm?
The whole body? How does that depend on the sword properties or on the position on the blade that actually hits
the target?
The first thing to note about this is

Tackling this needs rather
involved physics
It's rather complicated!

I'll do my best but don't get your hopes up too much. You will have to put up some effort too.
At this point it is time to introduce the major contributions that you can find in the Net (or with the links given below andelsewhere) for sword properties in general and for dynamic properties in particular.

1. George L. Turner:Dynamics of Hand-Held Impact Weapons 2).
George Turner's work is rather amazing if not all that easy to read. It is actually a 150 page book with plenty ofequations. I would vote for awarding him a German Ehrendoktor", a Ph.D "honoris causa", for this work. I learned
much from it and used it throughout of what follows.

2. Vincen Le Chevalier has published several outstanding "papers" in the Net; some you cna access from here 3).
He also offers a "Weapon Dynamics Computer" in the Net, a tool designed to compute and document the dynamic
properties of swords and other hand-held weapons. You can access it through Vincent's homepage. Peter
collaborated here with Peter Johnsson (see below) who provided design insights and precious sword data, during the
preparation of the exhibition ‘The Sword – Form & Thought’" 4) .

3. Peter Johnsson, sword maker, contributed to the "The Sword - Form and Thought" book 4) that documented a
special exhibition (Sept 2015 - Fbe. 2016) in at the "Deutsches Klingenmuseum" in Solingen, Germany.
Peter supplied fetching graphics that relate to a special geometrical analysis of the swords shown in the exhibition,and the result of the calculations done for most of these words by Le Chevaliers with his computer program.
The first two authors found it impossible to explain major dynamical properties of swords without resorting to equations(and, of course, assuming that the reader has some working knowledge of physics and math). I tend to agree with theirpoint of view but are nevertheless sticking to my guns sword: no equations!
Since there is no such thing as a free lunch, you will get a lot of words instead.

1)

John Clements: "Longsword and Katana Considered", The Association for Renaissance Martial Arts (ARMA), Internet
Essay (1999).
John has some experience in using a sword (in sports only), in contrast to me, and seems to know what he writes about.

2)

George L Turner: Dynamics of Hand-Held Impact Weapons, Sive De Motu, Association of Renaissance Martial Arts
(2002) posted on the pages of "ARMA - the Association for Renaissance Martial Arts". The book can be directly
accessed here

Iron, Steel and Swords script - Page 598

3)Vincent Le Chevalier; selected papers, all accessible via his home page: or directly if links are given below:
1. "A dynamic method for weighing swords" November 15, 2014.
The title is a perhaps a bit unfortunate because the article describes much more than "weighing" your sword. In
essence, it discusses the important parameters of a sword, how to obtain them experimentally, and how they
connect mathematically (lots of equations in the appendix). It also introduces the "two masses on a stick" model
for simulating dynamics. It helps you to find the parameters of your sword that you need to supply for the:2. On-Line weapons dynamics computer. You have to find it in the Net, the link may help.
3. Modelling impacts and damage. The article does exactly what the title says. If does so with equations on just a
few pages.
4. Simulating Sword Properties. Explaining how the simulation program works and in particular some information
about vibration modes computation.
1.

4)"Das Schwert - Gestalt und Gedanke ("The Sword - Form and Thought"). Hrg.: Barbara Grotkamp-Schepers et al. The
book to a special exhibition at the "Deutsches Klingenmuseum Solingen", Sept. 2015 - Feb. 2016.

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12.2 Static Sword Properties

12.2.1 Sword Bending: Purely Elastic
How do parameters of your sword influence how much it bends elastically ? That necessitates to consider the basic"beam-bending" experiment as shown when I first asked this question.
Assessing static sword properties means to try to change the shape of the sword by using forces acting on it. You
could, for instance, try to make it longer by pulling at it. That sounds a bit weird but that is how we assessed basic
static properties of materials in chapter 3. Remember the tensile test? That gave us Young's modulus, among otherthings. Doing a tensile test in reverse - pushing instead of pulling - was also mentioned and we will deal with that in thenext sub-chapter.
Here I look at a static load applied "sideways" or a classic bending experiment. Fix the hilt of your sword tosomething unmovable and then apply forces at right angles to the blade in the tip region. If we avoid immediate
fracture by not using forces that are too large, the blade will bend. If we avoid permanent bending or plastic
deformation by keeping the force below some limit, we will experience elastic deformation - the sword will assume
its old shape again upon removing the force - and that's what we go for here.
In other words: we go for the classical "bending beam" situation. That was already discussed by Leonardo da Vinci
and Galileo Galilei - but it is still the night mare of fledgling engineering students.
How you could do the experiment with an actual sword I have shown you before. Below is therefore a picture
showing only the abstract essentials needed for an in-depth analys

Basic "bending beam" experiment. The crosssection can have any shape
Imagine that pink thing to be your sword seen sideways. What you would want to know is how much it bends for agiven force. You can express the magnitude of bending - the distance indicated by the double arrow in the picture for a given force in millimeters (or inch), so we get a number for one property of a sword now.
Measuring that number is not too difficult. But calculating that number is a daunting task. "Beam bending" is thefirst thing that all students have to master who are forced to attend "Technical Mechanics" lectures, and it will havebeen an unforgettable experience to the surviving physicists and engineers. You not only had to understandsomething called "area moment of inertia", you actually had to understand and be able to solve a fourth-orderdifferential equation, requiring proficiency in differentiation and integration and a fearless mind. The links, by the way,lead you to the science modules dealing with the topic in question without avoiding equations.
This is bad news already but it will get worse! It is tough to calculate the bending of a beam with a constant crosssection but you just about can forget it completely for a variable cross-section, like for your sword. For a computer it
is no problem at all, but if you try to do it with pencil and paper only, you will run into your limits rather quickly.
Now the good news: The result of rather tricky calculations is simple and easy to grasp. Let's see what we can deduce
for a "sword" with a rectangular cross-section; i.e. a thickness of d and a width of b as indicated in the picture above.
The thickness might be in the order of 5 mm, and the width might be around 40 mm, for example. If you apply someforce - for example by putting a weight on the tip region - it will bend down a distance zmax; we may call that the
deflection. What might we guess about that quantity? And what is the truth?
1. Guess: Double the force F and you will double zmax?
Reality: Correct as long as zF is much smaller than the length l0 of your blade and the force is not too large.
2. Guess: Double the length, and the deflection zmax will double?
Reality: Completely wrong! The deflection increases with the third power of the length! Double the length and it
will be 8-fold , half it and it will be 1/8! That's why your sword will wiggle a lot more if you make it just somewhat
longer.
3. Guess: "Stiff" materials - those with a large Young's modulus Y - will bend less than resilient materials. So theIron, Steel and Swords script - Page 600

3.
guess is that zmax goes inversely with Y?
Reality: Correct - that is what happens. Increase Y by a factor of 2 and the deflection z max will be halfed.
4. Guess: A thin blade bends more than a thick one. So zmax goes inversely with the thickness d? Doubling the
thickness leads to ½ of the deflection?
Reality: Completely wrong again! The deflection goes with the inverse of the third power of the thickness! Double
the thickness and the deflection will be 1 / 8 of the old value.
5. Guess: A wide blade bends less than a narrow blade. So the deflection goes inversely with the width b of theblade?
Reality: Yes - that's correct.
Let's summarize that:

The deflection increases
1.
2.
3.
4.

linearly with the magnitude of the force. Doubling the force doubles the deflection.
with the third power of the length of the blade. Doubling the length makes for 8-fold deflection.
inversely linearly on Young's modulus Y. Doubling Y halves the deflection.
with the third power of the inverse thickness of the blade. Doubling the thickneass makes for 1/8
of deflection.
5. inversely linearly on the area momentum IA that describes the cross-sectional geometry in just
one number. Doubling IA halves the deflection

Maybe you realize by now that mathematical equations are great inventions. All of the above and much more can becontained in just one line of precise symbols! The thing to remember is that the "bending property" of a sword isparticularly sensitive to the length of the blade and its thickness. Or, to be more precise, to the average thickness since
we never have a rectangular cross-section. If one wants to be really precise, the exact shape of the cross-section has tobe taken into account by calculating its area momentum. That might be a daunting task but the result is exceedingly
simple: Just one number!. The larger, the smaller the bending.
What we got so far is tricky enough - and we have not yet considered that the cross-section (and therefore the area
momentum) typically changes as we go along the length of a blade. Not to mention that for curved blades we no longer
have a "simple" one-dimensional problem. How do we deal with that?
Not at all - besides pointing out the obvious: The basic rules as outlined above are still valid in principle for every
blade. If your sword blade tapers form hilt to tip, just conceive it as a sequence of pieces with constant but
diminishing cross-sections. Each sequence bends according to the rules above, and the total shape is given byconnecting the pieces. This can be seen nicely in this picture where the bending of the thin regions is more severe
than in the thicker regions closer to the hilt.
If your blade is curved, it will usually not bend very much anyway since it is not very thin at any place. There is no
curved equivalent of the small sword shown in the bending picture. Otherwise - see above.
What we are going to look at next is how the bending experiment and what we learned from it relates to our "classical"
tensile test experiment.

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12.2.2 Sword Bending: Deformation and Fracture
Bending and Relation to Tensile Testing
Heeding the first law of Materials Science, we know that in a simple bending experiment we can permanently deform oreven fracture our sword. How that works becomes clear as soon as we consider what happens in a bending experimentis not really all that different from what happens a tensile test experiment. The picture below illustrates this. You may
have seen it before; it was hidden in a science module way back. Now we need it in the main module but if you made itthat far you will now be ready for it.

Part of a bend blade
On the convex side, the material is stretched. Maximum stretching occurs at the parts farthest away from thecenter. Moving into the blade, the tensile stress and strain reduces and is zero at the center where we have what's
called a "neutral line" (or neutral axis, neutral plane) that experiences no deformation of any kind. If we forget
about secondary effects coming from things like "lateral contraction" (things pulled get longer but also get a bit
thinner) we have actually a neutral plane right in the center of a symmetric straight blade
On the concave side everything is the same, just with the signs changed: Instead of tension we now havecompression.
We know that ductile materials first deform elastically but switch to plastic deformation if the stress exceeds a criticalvalue called "yield stress" or yield strength. After some plastic deformation they will eventually break.
Brittle materials do not deform plastically at all, only elastically, and break as soon as the stress is "too high". What
exactly that means, and what kind of number goes with it, depends not only on the kind of brittle material in question
but also very much on its internal structure, in particular the presence and size of the nano- and microcracks it contains.
Refer to this module for a refresher.
The consequences of this are clear. As soon as the stress in the outer layer exceeds one of those limits, deformation or
fracture will occur.
Simple! Well - not quite. The statements above are certainly true but not sufficient to describe what really happens
to a real sword. There are a number of sword-related questions we now must ask:
1. Are the tensile stresses on one side of the blade really doing exactly the same thing as the compressive
stresses on the other side?
2. When the bending increases, thin layers on the outside of the blade are the first to experience criticalstresses. So these layers deform or break? And if they do so, does that make a noticeable difference to theblade properties at large?
3. Everything about critical stresses, like the yield stress and so on, always related to perfect homogeneousmaterials. What about real (ancient) steel, full of slag inclusions and other large particles, making it rather
inhomogeneous?
4. Many ancient swords were composite swords, consisting of different steels with different yield stresses andso on. Some parts might even have been rather brittle. Take pattern welded blades or Japanese katanas as
examples. How do these blades deform or break upon bending?
5. How about curved blades?
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5.
Most of the questions from above I will answer somewhat later. Here I will look at the easy ones; leading up to
answering the more difficult ones later.
Getting RealThe first question is easy. What happens at some nominal stress in compression is not exactly the same as intension . Buckling, for example, only happens for compressive stresses. Of course, the thin layer on the outside of theblade can't buckle just so; it is after all intimately connected to parts that do not want to do that. It might deform a bit
differently than its stressed counterparts on the other side of the blade, however, in particular because it can do so inthree dimensions .
As far as plastic deformation is concerned, there are also differences. Parts of the problem comes from the definition of
the nominal stress that does not take into account that the cross-section of the sample changes when it is stressed.
More to that in this link.
Nevertheless, as long as stresses are relatively small, there isn't much difference in the elastic behavior for thetensile or compressive regions (except for the change of sign, of course). As long as you only deform elastically, thedifferences should be minor.
Since you can bend a good blade quite a bit (once around your body if old tales are to be believed), stresses are notnecessarily allways small, though. Nevertheless, as long as you deform only elastically everywhere , there isn'tmuch difference between tensile and compressive behavior.
The key word is "everywhere". You only deform the same way everywhere if you material is perfectly homogeneous.
In pronounced contrast, if your material contains microcracks or other "largish" internal defects, there is a big
difference between compressive and tensile behavior. Tensile stress tends to open the cracks and thus eventually
to enlargement and catastrophic sudden failure by fracture, while compression tends to close the cracks. That's
why brittle materials like your toilet bowl or stone / concrete columns or walls can take lots of compressive stress
but not much tensile load.
The long and short is that with increasing bending your real (old) blade, containing internal defects of all kinds, will
eventually fail - by permanently deforming or by sudden fracture. Chances are that the failure starts on the tensileside.
The second question is a bit more tricky. If the outer layer experiences stresses just above the yield strength, behavior
will be different from what you find in a classic tensile test. In the latter case you have essentially a one-dimensional
problem. What happens somewhere in the sample happens anywhere else, too. All parts of the sample experience thesame stress and react in the same way (provided the sample is perfectly homogeneous). The sample is a cylinder, ageometry with the highest possible symmetry for this case. Couldn't be easier for theoretical analysis and that's why itis the standard test.
In a bending experiment with a real sword things are far more messy. Stresses vary a lot across the sample crosssection and the geometry is tricky, to say it politely. We have a three-dimensional problem, meaning that deformation
does not occur in the stress direction only.
Luckily a good computer can tell you what is going to happen for a particular sword (still made of perfectly
homogeneous steel!). Provided, of course, that someone intimately acquainted with tensor math and high-level
programming has produced a suitable piece of software. Forget detailed theory for a real sword made frominhomogeneous steel.
So I'm not going to dwell on this much longer but only point out one consequence. Let's assume that you did reachthe yield stress for the outer layer. Then that layer will deform plastically, meaning it would stay a bit longer on thetensile side and a bit shorter on the compressive side after the stress is released. Your sword then should bepermanently bend to some extent.
Well - yes, but to a smaller amount then you might expect. The reason is that next to your plastically deformed
outer regions you still have a lot of only elastically deformed material in the inside. A tensed spring, in other words.
This internal "spring" will exert forces on the plastically deformed parts, deforming them back to close to their
original length. Your sword thus will be almost perfectly straight again - but its microstructure in the outer layers has
now changed! They are elastically deformed and under internal stress. Your sword will now respond somewhat
differently to the next bending experiment, and with tough luck it deteriorates from one test to the next.

Bending too hard and too often
is not a good idea!
Generalizing a bit, what I have described above is a kind of "ageing" process for a blade. It looks the same asalways, but its properties have changed.
Maybe you realized that we are now already deep in question 4 from above. If your sword is a composite swords,
consisting of different steels, one will yield before the other on bending or whatever stress happens to be around. Now
let's turn around that question and ask: Is there any advantage of having swords made from different steels. Toughquestion with no easy answer.
I will look at that shortly, but for now we give question 3 some consideration: "What about real (ancient) steel, full ofIron, Steel and Swords script - Page 603

slag inclusions and other large particles, with carbon (and possibly phosphorous) concentration varying from one part ofthe blade to another?
That's easy to figure out. First, the yield stress will be different in different parts of the blade; I gave you a picture
relating to this already. In an bending experiment, "weak" parts on the outside regions will thus already deform
plastically while the rest is still in the elastic region. Everything said above comes into play, just in a morehaphazard way.
Worse, regions with large microcracks might experience too much stress and the microcrack starts growing. In anotherwise homogeneous material evenly stressed everywhere, conditions for crack growth would lead to immediate
fracture; that was the essence of fracture science, after all. In the more messy condition of an inhomogeneousmaterial with stress gradients (because of bending), the crack growth might stop if it reaches a different kind of
material or regions with stresses too low. Your blade might look the same after the bending test but at the next test
it might fracture. You are testing a different material now. Its microstructure has changed after the first test, even so
its outward appearance seems to be unchanged.
You also might experience sudden fracture if you bend too much - even so your material is, on average, rather
ductile and should have deformed plastically first. How can that be?
Well, for sudden fracture only a relatively small part of your blade needs to be rather brittle - because of a locallyhigh carbon concentration, a large (and brittle) slag inclusion, or something else. If a microcrack there starts
growing, it might already be too large to stop at a more ductile region. It keeps going and your blade fractures totallyor over most of its cross-section.
You get the drift. Real swords, especially old ones, are a far cry from being homogeneous, and that tends to make aconsideration of their mechanical performance very complicated.
From what I have written so far, it appears that things always get worse if you do not have just one kind of homogeneous
steel. If that would be true, their couldn't be any advantage to the production of complex pattern welded swords or any
kind of "two-steel" composite swords.
Indeed, most of the time there isn't an advantage if you compare a composite sword with a sword made from justone kind of perfectly homogenous steel. However, a composite sword made from several kinds of inhomogeneous
steel might still be much better than a sword made from "one" kind of inhomogeneous steel, the kind of steel
humankind had to work with for most of the iron and steel history.

This is a major statement. Savor it!
Let's give question 5 a quick look. What happens when you bend a curved blade? The answer is: In principle, much of
everything related above still applies. It is just a bit messier to describe in numbers since you now have always a threedimensional problem.
What does that mean? Well, if you look at the picture above relating to a straight symmetric blade (edges on bothsides), it actually shows the strain in the material. For a given distance from the neutral plane in the center of theblade, it is the same, the difference between front and back is only in the sign of the strain, and there is not muchvariation when you go along the blade parallel to the neutral axis either
Not so for a curved blade with an edge only on ones side and a broad back on the other. The strain and thus thestress might even vary from one side on the back to the other one. Somewhere on the blade stress are highest but
where that will be depends on many things.
If you bend "too much", parts of your blade may do unpleasant things, just as the straight blade from above. In bothcases it is rater unpredictable since we do not know the microstructure of the always inhomogeneous steel of old
blades.
What we still need to consider is bending while pushing forward in a perfectly straight line. It's called "buckling" and welook at it in the next sub-chapter.

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12.2.3 Sword Buckling
How do parameters of your sword influence "buckling", the shape-change if you push straight and at a right angle at an
immobile hard object?
Your sword will respond to static load somewhere on its blade by some elastic deformation - as long as it doesn't break,chip or deform permanently. Bending the blade "sideways" is the first basic situation that comes to mind and I havedealt with that in the preceding sub-chapter. The second basic possibility is running your blade straight against
something hard, causing it to buckle:

Basic "buckling beam" experiment
Applying force as shown above constitutes a compressive test, the opposite of tensile testing. I have treatedcompressive testing, including buckling, very briefly in the science part of chapter 3 but now we need to consider itin the backbone main section.
The long and short of buckling under compressive stress is:
For forces (better would be stress=force per area, remember?) below a certain limit, the beam (or sword) deforms
elastically by getting somewhat shorter as shown (exaggeratedly) in the middle situation above.
For forces at or above a certain critical limit the beam (or sword) deforms elastically by buckling sideways as
shown (in the right-hand situation above).
Increasing the force beyond that critical limit makes the buckling more pronounced, followed by permanent
bending (plastic deformation) and eventually fracture.
Buckling occurs for all structures under compressive stress - like columns, towers or simply most of architecture.
If your column or wall starts to buckle because it was designed too flimsy or the load gets too large because
other columns holding up the structure were destroyed, it is all over! The World Trade Centers in 2001 bear
witness to this.
It remains to determine how this "critical force" depends on parameters like the blade geometry and the material
properties. It is not too difficult to calculate this for a simple geometry and I will do just that in a science module. Once
more a simple equation that contains all (and more) of the points in what follows.
What would we guess - and what is true?
1. Guess: Thick columns are more stable than thin ones. So double the cross-sectional area and you double
the critical force?
Reality: No. The critical force is not proportional to the cross-sectional area but to lA, the area moment ofinertia. If you increase the area by a factor of two, the area moment of inertia increases much more than that.
For a beam with square cross-section, for example, lA increases with the square of the area!
2. Guess: Stiffer materials are less sensitive to buckling. So the critical force is proportional to Young's
modulus Y?
Reality: That is correct.
3.
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3. Guess: A long blade will buckle more easily than a short one. The buckling force thus might be inversely
proportional to the length?
Reality: Not really. The critical force decreases with the square of the length!
Will your sword buckle when you hit a target straight on? In particular your small sword with a tip region like a needle? If
you know a bit of math, you can easily calculate it, or at least get a good approximation, by using the buckling
equation.
How about an experiment? Hold your sword tip against some unwielding object and slowly increase the "pressure"(=force). Observe when it suddenly buckles.
When you then kill your wife since your sword ran right through her instead of buckling, you might be somewhat
surprised if not sorry. Well - I meant mechanically unwielding, of course! Why didn't your sword buckle?
Simple. Wives are typically not hard and unyielding objects (mechanically speaking). If the force it takes topenetrate a target is smaller than the critical force, you just cannot built up the critical force in the tip region. Even if
your sword hits now a wall on the other aside of your (former) wife, it will not buckle anymore. Why? Because thewife impaled upon the blade is now part of the blade (again mechanically speaking) The cross-sections increases byquite a bit and the critical force is now much larger.

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12.2.4 Sharpness
Defining and Measuring Sharpness
Your sword or knife that's just lying there is either sharp or blunt. So sharpness is a static property. Well, yes, but there
are properties closely related to sharpness that are more dynamic:
Retaining (or loosing) sharpness while using the blade.
Reconstituting sharpness after it was lost.
And now I have opened a rather large can of exceedingly squiggly worms! Let me make one thing very clear right away:

No, I don't have that easy fail-proof
recipe for keeping your blades sharp
I have enough trouble to keep myown blades (medium) sharp
All I can give you is a little "theory" of sharpness and retaining same. But that is not overly helpful for sharpening a
blade. It is a bit like playing the piano (or any other musical instruments): Knowing all about the theory of musicalnotation and how that transfers into hitting the right key the right way at the right time, will not a piano player make.
And the top players (who do certainly know the theory) don't know exactly why they are somewhat better at it thenthe second (still very good) tier of players.
Some top experts can sharpen your sword better than "normal" experts but nobody knows what, exactly, they dodifferently. That's why sharpening a blade by hand is still an art. Sharpening blades by machines is different. The
razor blades you buy are all extremely sharp (even so there are some differences between brands) and comestraight from a machine.
For reasons not all that clear to me, the concept of sharpness did not receive much scientific attention until quite
recently. References 1 and 2 (freely available in the Net) give examples of recent papers dedicated to the subject; theirliterature lists will lead you on if you like scientific fights and heavy math. What I learned from perusing some more
publications is that there is no general agreement on how to define and measure sharpness. Greatly simplified, twobasic ways of defining the sharpness of a given blade by a number are pursued:
1. Sharpness relates to the geometry of the blade, in the most simple case it relates to the inverse of the radius ofcurvature of the edge.
2. Sharpness relates to the performance of the blade, e.g. how deep it cuts into a standard substrate for a given
force pushing it down.
The picture below gives an idea of how one could relate sharpness to the radius of curvature of a blade:Sharpness demands a small radius of curvature
at the blade edge
Sharpness sort of begins at a radius of curvature of a few micrometers (µm). If you want "razor-sharp", you need to
do better: A radius of 0.01 µm (=10 nm) is a good number then. The limit, of course, is the size of an atom (imagine
the circle in the picture to be an atom), giving a radius of about 0.0001 µm or 0.1 nm. That would be a more than
10.000 fold improvement on sharpness relative to a 1 µm radius.
I'm not sure if anybody has made a length of blade "atomically" sharp. But one-atom tips are common goods in"scanning tunneling microscopy" or STM.
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But is it only the radius of curvature that determines sharpness? Of course not, consider the next two pictures:

Blades with identical radius of curvature but
different shapes

Ideal and real edge
Not much needs to be said. The upper picture shows blades with the same radius of curvature but different blade
geometries, Would they all be of identical perceived sharpness? Probably not - but it always depends of what you
have in mind. Cutting hairs close to the skin without cutting the flesh certainly would profit from an optimized blade
geometry like the one on the left. A meat cleaver wouldn't do so well with this shape, though.
A more severe problem, however, results from the fact that most likely the geometry changes as you move along
the blade. The radius of curvatures will not be the same at every point, the edge is not perfectly straight, and so on.
My drawing skills cannot do justice to that but you get the idea. Irregularities along the blade are probably not sogood for cutting straight into something by only pressing the blade down but might give better results compared tothe "ideal" blade if you start "sawing". Saws do not have teeth just for looks, after all.
To conclude:
1. The (average) radius of curvature of your blade is not a unique and precise measure of the sharpness of yourblade. But the trend is clear: A smaller radius of curvature will tend to increase the sharpness.
2. The (average) radius of curvature of your blade is not a convenient indication for the sharpness because it isdifficult to measure. Cut your blade and look at the cross-section in a light microscope? Won't work, you need far
higher resolution than what a light microscope has to offer. You need a (scanning) electron microscope!
Sharpness is nanoscience!
3. Getting numbers for the radius of curvature thus is possible but not convenient.
Indeed, if you look for high-magnification pictures of blade cross-sections in the Net, you won't find many, if any - aslong as you do not hit on the pages of "scienceofsharp". This site features many excellent pictures that were taken
in a "scanning electron microscope" (SEM); here are a few:

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Rather good edge (left), and a somewhat crumbly
one (right)
Source (for all SEM pictures here): from the scienceofsharp web
page
Whoever you are (the site doesn't reveal the maker), thanks a lot
for sharing!

About as sharp as it can get
It's not easy to obtain an edge like that! Don't ask me how to do it! Consult the page I mentioned.
But now let's look at the second way of defining sharpness. You measure how well a given blade cuts some test
material. Easier said than done. What kind of material do you use? How is the cutting done? Just by (statically)pressing the blade on the target material, by (dynamically) hitting the target? With or without "drawing" the blade during
the hit? Or would you do a repeated kind of sawing motion?
The Japanese already judged the sharpness of their blades by hitting a target and observing how deep the cut went. I
have covered that already. Starting in the 16th century they formally judged the sharpness of their swords by having
experts cut through piled-up bodies (hopefully already dead). The result was inscribed on the tang of the blade. Good
blades in the hand of expert testers cut easily through two if not three bodies piled on top of each other. I have dealt withthe shortcomings of this method already; use the link.
In the Western world no "standardized" testing like this was done but from old pictures you get the impression that there
were some inofficial demonstrations of what an expert could do with a good, sharp blade.
Nowadays we need to be more objective and quantitative. So a machine does the test and takes numbers while it's
doing so. We also use standardized, non-biological materials for the test. In essence, you do the reverse of a tensile
test - a compressive test - pushing the blade to be tested down onto a target material. You may do that with constantIron, Steel and Swords script - Page 609

(slow) speed, monitoring the force needed to get to the depth as given by speed times time. Curves result that are notunlike the stress - strain curves treated in detail here, and from all of this you might derive a number for the sharpness ofthe blade tested. Reference 1 elaborates on thisBut this test only covers a kind of static cutting without moving the blade. That might cover the use of chisels but
even then you tend to apply very large forces for very short times (you bang it with a hammer) and a static test
might not cover that adequately. A blade that "won" the static test would be be inferior to a less sharp one if it
blunts under the first stroke of the hammer, for example
So let's not look at these tests anymore but turn to the pressing issue of edge retaining.
Retaining Sharpness
It's difficult to produce a sharp edge but it is impossible to retain a sharp edge if you use your blade frequently. Whatcauses an edge to blunt, and how does that happen in detail? Rather tough questions, in particular the second one.
If you want answers to the detailed mechanisms of blunting, you need to look at the blunted blade with a high-powered
electron microscope once more. That's not for everybody to do, and if you want pictures I must refer you to the thescienceofsharp site once more. Or even better, the article of our old acquaintance, John D. Verhoeven 3) who has
written an extensive article with many (SEM) pictures about the subject.
The first question is easier to tackle - at least up to a point. All of us know one sure way of blunting a blade: Use it on
something harder than the edge of the blade. Hit a decent stone with most blades and they are now definitely dull - if not
fractured, dent and bend
What happens is quite simple in principle. During impact (slow or fast) stress builds up on the blade edge and on
the regions of the target that is hit by the edge. Hardness essentially measures the stress needed to induce plastic
deformation (the yield stress) or, more loosely speaking, the onset of local cracking, and the softer material will
"give" first, deforming in some way and thus blunting itself.
Here are a few pictures showing what could happen:

Razor edge dulled by pulling it "sideways" overglass
No surprise here. We just bend the edge by plastic deformation. This can be reversed to some extent by "stropping"because the sharp edge is still there. You "only" need to bend it back.

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Edge dulled by drawing it across the lip of a
glass beaker
Here we have a bit of bending but mostly deformation by compression and "filing" or abrasion, resulting in a bluntedge. Glass is just quite a bit harder than most steels and thus acts as the file; the softer steel will be the filée
The hardness of a material is a reasonable well defined property, I have gone through that. Below are some old
examples:MetalsVickers
Hardness

Ceramics

Vickers
HardnessTin (Sn)

5

Limestone

250

Aluminum (Al)25

Magnesia (MgO)

500

Gold (Au)35

Window glas

550

Copper (Cu)40

Granite850

Pure iron (Fe)80

Quartz (SiO2)

1200

Good tin bronze (Cu + 10% Sn)

220"China" (Mostly Al2O3)

2500

Mild steel

140

Tungstencarbide (WC)2500

Hardened steel (extreme)

900
Polymers

Polypropylene

7

Polyvinylchloride (PVC)

16

Polycarbonate

14

Epoxy

45

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This table makes clear why our ancient forebears were reluctant to embrace early iron technology, considering thatthey had marvellous bronze blades that were generally superior to blades made from wrought iron or mild steel. It
also makes clear why case-hardening the edge of a steel blade by quenching makes all the difference. You mightend up with an edge that could, in principle, cut glass or granite! However, the first law of economics still applies!
You pay dearly because there are plenty of problems, too:
1. You need good and homogeneous carbon steel to start from.
2. You can re-sharpen your edge only a few times (if at all) because you quickly wear off the thin layer of hardmartensite.
3. Your edge is rather brittle and chips easily.
The Japanese sword demonstrates what it takes to make the best out of extreme edge hardening while not yet inpossession of superior modern steel that was liquid once and can be cast.
Now to the trickier points of blunting a blade. All of us know that our kitchen knifes will eventually become dull even if wenever ever try to cut anything hard! One of the key words hear is "wear" and with that you open the door to hell. I'm notgoing through it. I'll just show two pictures demonstrating what can happen:

Formerly sharp (and hard) knife blade after
cutting
about 7 m of heavy (but soft) cardboard

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Razor edge after cutting a few cm of bond paper
Paper is normally considered to be much softer than hard steel. But "steter Tropfen höhlt den Stein" (constantdripping wears the stone) as the Germans know, and the wear of the steel cylinders of rotary presses (used, e.g. foryour newspaper) caused by their exposure to "soft" paper is a major issue in technology.
If you want to know more than that, you are best of by reading the article of Verhoeven and colleagues about wear ofsteel blades 4). Here is the abstract:.
A study is presented on the relative wear rates of two
carbon steels, a Damascus (wootz) steel and astainless steel, using the Cutlery and Allied Trades
Research Association (CATRA) of Sheffield Englandcutting test machine. The carbon steels and stainlesssteel were heat treated to produce a fine array ofcarbides in a martensite matrix. Tests were done at
hardness values of HRC=41 and 61. At HRC=61 thestainless steel had slightly superior cutting
performance over the carbon steels, while at HRC=41
the Damascus steel had slightly superior cutting
performance.

1)

C: T. McCarhty, M.Hussey, and M. D.Gilchrist: "On the sharpness of straight edge blades in cutting soft solids: Part I indentation experiments", Engineering Fracture Mechanics, Vol 74 (2007) p. 2205 -2224
Available in the Net

2)

P. Stahle, A. Spagnoli, and M. Terzano: "On the fracture process of cutting", Procedia Structural Integrity, Vol. 3 (2017)P. 468 - 476

3)John D. Verhoeven: Experiments on Knife Sharpening
Directly published in the Net

4)John D. Verhoeven, Alfred H. Pendray, Howard F. Clark: "Wear tests of steel knife blades"Wear, 265 (2008) pp 1093 –1099

Iron, Steel and Swords script - Page 613

12.2.5 Sword Types and Static Properties
Comparison of "Ideal" Swords - Bending Within the Elastic Limit
Let's perform a classical elastic bending experiment with completely different kinds of swords that are, however,completely identical in their geometry. Same blade length, same cross-section, same tapering etc. Let's look at thefollowing list
1.
2.
3.
4.
5.
6.

Bronze sword
Wrought iron sword
Good ("eutectoid") steel sword
Wootz steel sword
Pattern welded sword
Japanese type sword (katana)Let's start by assuming that all those swords are made from homogeneous and uniform materials, not containing anylarge defects or inclusions. In other words, we have perfect or ideal swords from a material point of view.

Basic geometry of the bending experiment
We know that for a given force acting on the blades as shown above once more, the amount of bending or maximum
deflection (given by the distance zmax) increases
1.
2.
3.
4.

linearly with the magnitude of the force. Doubling the force doubles the deflection
with the third power of the length of the blade. Doubling the length makes for 8-fold deflection
inversely linearly on Young's modulus Y. Doubling Y halves the deflection
inversely linearly on the area momentum IA that describes the cross-sectional geometry in just one number.
Doubling IA halves the deflection
Now let's bend these swords but within the elastic limit. That means that we use forces that are not large enough tocause permanent changes in the blades. First we compare sword No 1 and No. 2:
The only difference between these swords is Young's modulus. For wrought iron and bronze we have
YBronze=115 GPa
Yw. I. =210 GPa
So wrought iron is considerably stiffer than bronze; about 80 % to be precise, and thus will bend about 80 % less thanthe bronze sword.
You should now be a bit confused since neither bronze nor wrought iron are well-defined materials. Do I mean 90% Cu /10% Sn bronze? Arsenic bronze? Wrought iron with almost no carbon or with 0.2 % carbon? Those are different
materials after all.
That is perfectly true. Nevertheless, Young's modulus for all those different copper or iron alloys, summarily
addressed as bronze or wrought iron, is about the same. Differences are at most in the 10 % region and that is
negligible for what we are doing here. I have emphasized that before and I have given the scientific reasons for that.
In essence, Young's modulus is a property resulting from the bonding between atoms and as long as most atoms
are of one kind, it is much the same. It doesn't depend much on what kinds of other atoms are mixed in as along as
there are only a few percent.
Now let's include swords No. 3 - 6 in our comparison. They are made from very different kinds of steel or from several
kinds in some composite construction. Nevertheless, their bending behavior in the experiment above is not noticeably
different from the wrought steel sword. That's because Young's modulus of all (low-alloyed) steels is about the same forthe reasons given. The large majority of bonds is still found between iron atoms.
However, in some of the steels we now may have a lot of cementite, (iron carbide, Fe3C). Doesn't that make adifference?
Yes, it does. Young's modulus of a composite material with large percentages of other atoms will be some kind of
average of the individual moduli of the constituents. I have shown you how to calculate this.
Wootz steel for example, can be seen as a composite of ferrite (=iron) and cementite (=iron carbide Fe3 C).
However, as it happens, Young's modulus of cementite, around 200 GPa, is not much different from that of iron
Iron, Steel and Swords script - Page 614

around 210 GPa. You don't have to believe me, in reference 1 I give you one serious source plus the abstract of that
paper. So no matter how you average, you end up around the value of iron.
Of course, if you look closely you will find some differences. But here we don't care about differences of 10 % or so.
We simply commit to memory:

All iron / steel swords with identicalshape behave the same elastically.
Differences in elastic behavior ofiron / steel swords are always due
to differences in geometry
I know that this contradicts a large amount of what has been written about "elastic" properties of composite swords.
Pattern-welded swords are almost always described as a combination of a hard but brittle steel with a soft but elastic
one, giving you hard and elastic as a result. Wrong on three counts:
1. It's almost always a combination of a "regular" low carbon steel with a (somewhat harder, OK) phosphorous
steel.
2. Why should the result be hard and elastic? Why not soft and brittle?
3. The elastic properties do not depend on what kinds of steel you combine. They are the same for each steel andany combination of steels you can conceive.
Other common mistakes often found in the literature are:
1. Considering that "elastic" means "not being brittle" or in other words, confusing elastic deformation withplastic deformation.
2. Confusing yield stress (or fracture toughness) with elasticity. A steel with a high yield stress (=hard steel) is
seen as "more elastic" than a "soft" steel!
A sword might be pronounced to be more elastic for example if you can bend it to a larger degree than some othersword before something unpleasant happens.
That leads us to the second point we want to look at here: How do those still ideal swords compare if I increase theforce in the bending experiment to a value where "something" happens?
Comparison of "Ideal" Swords - Bending Beyond the Elastic Limit
So what happens if you bend until something happens? What will happen? For the first three swords the answer issimple. All of them are ductile and therefore all of them will deform plastically as soon as their yield stress is reached.
This will first take place in the outer layers as described before as soon as a critical force is reached on the bending
experiment. Then the stress in the outer layers exceeds the yield stress of the material. It is not too difficult to calculate
the stress in a bending experiment from the force but it is no longer straight-forward as in a tensile test experiment.
If you keep increasing the force beyond the critical level, the plastic deformation spreads into the interior because
deeper and deeper parts experience the yield stress. In the "neutral line (or plane) in the center, the stress is (ideally)
always zero.
Since yield stress is (more or less) just another word for hardness, and hardness depends not just on the chemical
nature of the material but also very much on its internal structure, only general statements about the behavior of ourswords can be made.
The first general statement is easy: As soon as parts of your blade deformed plastically, it will not "snap back" tobeing perfectly straight after you release the force. The permanent bending effect, however, may be small forreasons considered below.
Bearing this in mind, we now look cursorily at our examples form above:
1. Bronze is comparable in hardness to wrought iron or even mild steel. So there shouldn't be much of difference
between a bronze sword and one made from wrought iron with respect to the critical force. However, since
Young's modulus of the bronze sword is smaller than that of the iron sword, it will have curved considerably morethan the iron sword before it starts yielding plastically.
2. Sword No. 3 was made from eutectoid steel, i.e. very good steel. Depending on its processing it could be harderthan a bronze sword and thus could resist larger forces before plastic deformation commences. You might beable to bend it into a semicircle before "something happens", i.e. plastic deformation.
3. The behavior of No. 4, the wootz steel sword, is not easy to predict. It should be considerably harder than abronze sword and thus able to take a lot of force before plastic deformation starts, just like No 3. But it also could
be brittle and fracture right away at some not-so-well defined stress.
4. Pattern-welded swords as No. 5 come in many types; they are all of the composite type. If you see a pattern,
there are at least two kinds of steel on the outside and the one with the lower yield stress will give first. You may
not notice that, however, if the other one is rather hard, and mistake its behavior as still being fully elastic when in
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fact it isn't. have I have covered that before. We also may experience that "something else" happens:delamination in parts of the welds. In what follows I will look into the behavior of composite swords a bit moreclosely since this is important for what follows
5. There is of course no straight double-edged katana. But we can imagine such a composite sword with a soft core
and a hard outer shell like a katana; up to a point it is what's called a Viking sword. As long as the hard outershell gives first, everything is about the same as with No 3 or 4, except that permanent bending progresses more
quickly when the plastic deformation zone reaches the soft core.
It gets more interesting, however, when the soft core starts to deform plastically before the hard outer shell. Think
about that yourself for a while, I will get to it later.
In the case of swords No. 4 and 5 we are looking at properties of composite swords. They are by definition"inhomogeneous" if still ideal swords. In other word, we have a composite of at least two steels with quite different
behaves concerning plastic deformation and fracture, even so they have the same Young's module and thus behave
identical as long as only elastic deformation is concerned. But each steel of the composite construction is still perfectly
homogeneous as we assume here.
We can't avoid any more to look a bit more closely on how an (ideal!) composite material performs in a classic
tensile test or bending experiment. I will do that in the next subchapter.

1)

A. P. Miodownik: "Young's modulus for carbides of 3d elements (with particular reference to Fe3C)", Journal Materials
Science and Technology Volume 10, 1994 - Issue 3; Published online: 19 Jul 2013
Absract:The Young's modulus of transition metal carbides has been calculated from their assessed thermal properties to
explain why the modulus of steels and white cast irons can be only marginally altered by changes in composition or heat
treatment . It is shown that the modulus of cementite (200 GN m-2) is virtually identical to the value calculated for pure
ferrite (215 GN m-2). The predicted systematic variation for the modulus both with structure and position in the periodic
table rationalises previous isolated experimental observations and confirms that the MC carbides of the group IV elements
should have the most powerful strengthening effect in a matrix of their parent metal.

Iron, Steel and Swords script - Page 616

12.2.6 Static Properties of Composite Swords
A Little Bit of Theory: Plastic Deformations of Composite Swords
Here we look a bit more closely on how composites perform in static mechanical testing. First we look at how acomposite made from ideal materials performs in a classic tensile test experiment. This is a good exercise to get a firstidea of what we are up to. Next I will generalize to real composite swords made from not-so-ideal materials.
We start with comparing the stress-strain diagrams of a hard ("red") and soft ("blue") ideal steel. They are shown below.

Stress - strain diagram for a hard steel,deforming only elastically, and soft steel,deforming elastically and plastically
The rectangles sybolize shape change
We apply stress until a certain elongation (=strain) is reached that shall be the same for both steels. It is indicatedby the yellow dot on both strain axes. The red steel can do this strain at a stress (red dot on the stress axis) that isstill in the purely elastic deformation region. The blue steel deforms plastically after its yield stress is reached (pinkdot at the stress axis; at the deviation from the straight line). It is evident that the red steel needs more stress (reddot on its stress axis) than than the blue steel (blue dot on its stress axis) for the strain chosen.
The red or blue rectangles symbolize the specimen lengths at the various points in question.
When we now release the stress, the red steel goes right back to its original length while the blue steel isplastically, i.e. permanently deformed and stays a bit longer (green dot at its strain axis). If I want to return it to its
original length I have to "push it down", i.e. apply compressive stress as indicated by the purple dot on the negative
stress axis of the blue steel.
Now let's do a tensile test with a composite of the two steels as schematically shown in the next figure. Just weld thetwo pieces together somehow, making an "ideal" weld, of course. Let's go through what happens step by step.

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Tensile test for a composite of soft and hard steel
1. In the beginning of the test both steels are elongated elastically and the stress-strain curve is identical to the firstpart of both individual curves above since both steels behave identically - they have the same Young's modulus,
after all.
2. As soon as the yield stress of the blue steel is reached, it will now deform plastically. That takes less stressthan the elastic deformation, so the total stress the machine needs to apply can go down a bit. Upon further
elongation the stress-strain curve gets a bit flatter and deviates from the straight line as shown.
3. The pre-set strain is now reached at a somewhat lower stress level indicated by the lower yellow dot.
4. Releasing the stress, the blue steel would like to stay a bit elongated as indicated by the dark blue dot on thestrain axis. That would, however, leave the red steel elastically stretched and "under stress" as indicated by the
red dot on the stress axis.
5. The red steel is fully attached to the blue steel and acts like a tensed spring. It pulls the blue steel "down",
putting it under compressive stress.
6. The final state will be some slight elongation of the red steel, retaining some tensile stress, and somecompression and compressive stress in the blue steel. The "winner" with the lowest stress will be the steel thatoccupies a larger volume in the composite.
In the schematic picture above the relation between red and blue is about 50 : 50 so the effect will be noticeable.
The red part will be a bit too long, the blue part a bit too short compared to what they would like to be at zero stressvalue. The whole contraption thus would bend somewhat to the left.
We can immediately transfer these insights to the bending situation of a one-material sword. As discussed before,
plastic deformation starts on the outside because that's were stresses are highest. In a way, it's not so different from acomposite with a soft and a hard part. Here the outer layer is the soft part. In the beginning the plastically deformed partof the blade will be just a small part of the whole blade. The plastic deformation effects will be hardly noticeable in the"stress - strain" curve, which, in the bending case, would be the force vs. deflection curve. You would not notice theslight bending of the blade after the test because the large part that was only elastically deformed will have "pulled back"the small plastically deformed parts on the outside.
But the outer layers now contain a "build-in stress". It is compressive on the side that experienced tensile stress during
the experiment and tensile on the other side.
You may not notice that. However, if you now bend the blade again and in the other direction (maybe because yoususpect that it might no longer be perfectly straight), the outer layers will reach the yield stress earlier because theirbuilt-in stress from the earlier experiment must be added to the outside stress. Plastic deformation then starts earlier
and a larger part of the blade will be affected. The still far larger part that was only elastically deformed will pull the bladeback to being (almost) straight again
You get the point. Repeated bending back-and-forth that appears to be fully elastic in the beginning, might slowly
built up structural changes in your blade that will weaken it. One bending experiment too much then might damage
the blade since it remains bend. Worse, your blade might now fail you in battle when large stresses areencountered.
How about bending a composite sword? The katana type (soft inside, hard shell) can now experience several modes ofdeformation, e.g.:
1. Stresses everywhere are below the yield stresses of both materials. Purely elastic behavior, in other words.
2.
Iron, Steel and Swords script - Page 618
3.

1.
2. The yield stress in the outer (hard) layer is reached but no yet in the softer interior
3. The yield stress in both materials are reached4. The yield stress in the softer inner materia is reached but not in the outer hard shell.
his calls for a systematic approach and none better than a good picture:

Deformation modes in a composite (soft core,
hard outside) blade. Identical stresses (=fixed
bending) is assumed but the yield stresses of the twosteels are somewhat different
We look at one half of a section of a blade edge-on. The stress axis, in other words, would be the edge of the blade
and we see the right-hand side of the blade. The soft core (light blue) is somewhat thicker then the hard outer shell(yellow). The blade is under stress (consider it bend) and the red line shows how the stress increases from zero at
the neutral line smack in the center of the blade to the outside. The blue and red dashed lines denote the yieldstresses of the two steel.
In this example we have the same stress distribution in all four cases but somewhat different yield stresses of thetwo steels. What do we see?
Case 1: In both steels the maximum stress is below the yield stress. Only elastic deformation takes place.
Case 2: Stresses are larger then the yield stress in the outer layer of the hard steel but still below the yield stressof the blue steel. Some plastic deformation in the outer layer occurs.
Case 3: In both steels the yield stress is reached in some parts. Plastic deformation occurs in the outer layer anddeeper inside.
Case 4: Only the soft steel experiences stresses higher than its yield stress. Plastic deformation occurs inside theblade.
This gives some impression of what could happen if your two steels are somewhat different, everything else being thesame. Now let's look at what happens to a given blade as the stress is increased. You just increase the bending to dothat as schematically shown by the black curve on top of each diagram.

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Tensile test for a composite of soft and hard steel
Once more and unavoidably, we start with elastic bending only (case 1) but then - surprise! - comes plastic
deformation of the soft core (case 2) before the outer shell is affected! More bending introduces plastic deformationin both steels (case 3) and finally we have continuous plastic deformation of most of the body of the blade (case 4).
In any case, we have more parts of the sword plastically deformed than we would have in a one-steel sword
It should be clear from what I pointed out before that the only elastically stressed parts will try to "undo" the plastic
deformation of the other parts as soon as the outside stress is relieved. It should be equally clear that in any caseyou now have tensile and compressive stresses inside your blade that change its behavior upon encountering newstress.
We may draw a first conclusion: We can make the simple composite blade discussed above from steels with all kindsof yield stresses and in many different geometries. Many different responses to bending stresses are thus possible forthose blades. It should thus be no surprise that some smiths, some schools, some regions, and so on should havebeen particularly famous because they happened to produce a particularly good sword. Small details matter! The
precise geometry, the materials used, the way the forging and heat treatments were done, and so on, made thedifference. And I'm still talking ideal materials here! Ulfberht swords come to mind, for example.
I went through this in some detail to demonstrate a major points

A sword made completely from theideal hard steel will have a superior
elastic limit and will always
suffer less plastic deformation
than a composite sword
for a given stress
I have used the term "elastic limit" in the sense of how far you could bend a blade before "something happens". It isa property that is easy to understand in principle but a bit tricky if you look at it in detail. In purely scientific terms
the elastic limit is reached as soon as parts of the blade experience plastic deformation. That means - again inpurely scientific terms - that the elastic limit is nothing but the yield stress of the "softest" component. In practicalterms, however, the situation is more complex for the following reasons:
1. As pointed out above, a composite blade made from ideal steel may undergo considerable plastic
deformation in parts but bend back to being almost straight again when the stress is relieved. The "bender" ofthe sword who does the test would be inclined to assign an elastic limit to the blade that is well above the
one given by the lowest yield stress.
2. For a composite blade made form real and inhomogeneous steel, the "scientific" elastic limit is reached assoon as some particular weak part somewhere in he blade "gives", i.e. deforms plastically. A human tester
wouldn't notice that and once more assign an elastic limit far larger than the "scientific" one.
We have a problem now. A properly measured elastic limit for composite blade tends to be lower than what ahuman tester would come up with by just bending the sword. But nobody is interested in the scientific number,
Iron, Steel and Swords script - Page 620

firstly because it just doesn't do justice to a real sword and, secondly, because it almost never exists. Quantitative(and by necessity more or less destructive tests) are almost never done with real swords. In what follows I will use
the term "elastic limit" therefore in the less precise but more human context.
If we now look at pattern welded swords, nothing changes in principle. The major difference is that plastic deformation
now will occur here and there in the twisted striped rods, depending on the local geometry and the resulting stress
distribution.
We now have arrived at a major "theoretical" result for ideal steels:

The elastic limit behavior of composite
blades is worse than that of the hardand better than that of the soft steel
Same thing for the plastic behavior,"Worse" means that the elastic limit is lower and that more volume deforms plastically upon bending.
We have just hit upon what's known as "law of averages" for composites. It simply states that a specific property of acomposite is some kind of average of the properties of its constituents. Not your usual average, and not necessarily
easy to calculate, mind you. I have given you a detailed example of how that works for Young's modulus. The
consequence is that a composite property can never be outside the range found by its constituents.
The law of averages is not a real law, just a guideline, though. It is not overly helpful when it comes to "digital" properties
that cannot be easily expressed in numbers. If you combine a ductile and a brittle material, the plastic deformation orsudden fracture properties cannot be an average of the individual properties . What numbers would you average?
Nevertheless, the composite in question would be less prone to sudden fracture but possibly bend a lot instead.
Plastic Deformation and Fracture of Composite Swords Made from Real Old SteelIf you have worked your way through all of the above, you know that predicting the precise bending-test behavior of a real(old) composite sword that consist of different inhomogeneous steels, is well-nigh impossible. What could happen issudden fracture after just a bit of elastic bending, major plastic deformation after a decent elastic interval, or fracture insome parts, plastic deformation in other parts and nothing (i.e. purely elastic behavior) in the rest.
Whatever kind of real composite blade you have, some regions will have a lower yield stress than others. Maybe thesteel there is of the soft variety, or maybe your hard steel has a weak spot there. Under loads of all kinds, the yieldstress might be reached and plastic deformation occurs, whereas neighboring regions still are only elastically strained.
Without a load, plastically deformed regions will be "pulled back" to some extent by the elastically deformed regions
around them, and the blade looks much the same. But there are now all kinds of compressive and tensile stresses inthe various parts.
That is not necessarilly a bad thing. Real blades may contain considerable internal stresses from the way they were
made. This is particularly true for curved blades with an edge on only one side or even straight blades withasymmetric cross-sections like backswords. I gave you a whole (albeit scientific) module on this.
However, the biggest problems does not result from variations of the yield stress in your inhomogeneous blade materials
or from internal stress built-up but from the presence of rather large slag inclusions or other large defects. Around these
defects local stresses can be much larger than in the rest of the material, and locally you may reach fracture conditions
even in otherwise ductile steel long before that happens in the undisturbed material. And as soon as you run into local
fracture somewhere inside the material, total fracture is not too far.
That's particularly true if things happen quickly, like when you get a hit one your blade. Plastic deformation is themechanism that distributes the large local impact energy into the volume of the material but it needs some time to do
this. If locally present microcracks opens faster than the energy-dispersing dislocations tied to plastic deformation can
move, it is all over. Your blade will fracture.
Somewhere in all of this lies the explanation why old steel is typically far more brittle and with a yield strength far
smaller than what one would expect from its carbon content. Moreover, you can expect substantial differences
between different batches of the same steel. In a way of speaking, "old" steel is already a composite material
combining "good" parts of the basic material and bad parts. The law of averages than tells you that old steel is neveras good as modern homogeneous steel with the same nominal carbon concentration.
In other words: Looking at composites of old steels is a messy enterprise. Even the most simple deformation
experiment, the tensile test, get's messy. A still quite simple bending test is even messier, and what happens at areal test - hitting something with your sword - is hard to conceive by theory. Be grateful that it is not all that difficult
to conceive experimentally.

Iron, Steel and Swords script - Page 621

As far as static mechanical properties are concerned, there seems to be no advantage for composites of two or more
steels. Well - not quite. If one of your steels has extremely bad properties in some parts, like being too soft or too
brittle, "averaging" it with another one, will make this better. Not good, but better. The brittle part might even fracture but as long as its just a part of the blade, the blade is now damaged but still serviceable.
I'll look at bit more closely into this in the next sub-chapter.
If we now consider "real" (old) steel instead of ideal steel, where does that leave us with respect to our list of swords
from above? I'll give you short answers here:
1

Bronze sword.
This sword was cast and therefore contains no large "dirt" particles like slag inclusion and such. It might, however,contain large voids from trapped gas. This has indeed been found in some old bronze swords and would haveresulted in sudden fracture under stress.

2

Wrought iron sword
This sword would have less than 0.2 % carbon on average but would contain slag inclusions and so on, areas withrelatively high carbon concentration, and possibly some phosphorous in some parts. It thus would have beensomewhat harder than clean and homogeneous wrought iron. It could have been relatively ductile or rather brittle,
depending on many parameters that are not known. See the net sub-chapter for examples.

3

Good ("eutectoid") steel sword
This would be a very good sword, especially if the edge was quench-hardened - provided the steel is homogeneous.
If it isn't (and that's certainly the case for all old steels), see above. You will find the full range of properties - fromvery good to critical since brittle.

4

Wootz steel sword
This kind of sword supposedly was very good, if a bit on the brittle side. However, it is quite likely that wootz bladescame in all kinds of qualities. There are very few experimental tests, one is shown here. The tested wootz steel was
not too bad but generally inferior to modern steel.

5

Pattern welded sword
We can be quite sure that swords with a full pattern welded body were rather lousy; I will get back to this. If they
contained a steel core and had pattern welded parts only on the outside ("veneer" type), the sword might have beensomewhat better. The phosphorous kind of steel always found in pattern welded blades would have made the sword
rather brittle and the bad quality of old steel didn't help much either.
However, cracks that developed in one part of a "striped rod" might have been arrested in the other one. That
damaged the blade but prevented sudden complete fracture. So pattern welded blades were probably better thanreally lousy blades made from just one type of (lousy) steel. They were definitely much showier.

6

Japanese type sword (katana) (in its "Viking sword" manifestation)
We have a hard outside and a soft core, both made from inhomogeneous bad steel, full of slag and other inclusions.
However, at least the steel of real katanas was homogenized by faggoting. That made not only the distribution of big
defects more homogeneous, it also broke them up and instead of a few large ones you now had a lot of smaller
ones. That may have helped to prevent sudden fracture upon impact.
The soft core could absorb local energy bursts and stop crack growth initiated in the ultra-hard (and completely
brittle) edge. "Katanas" or Viking-type swords may have been the best swords one could make from lousy bloomery
steel but they wouldn't be a match for swords made from modern steel.
If the Viking sword was made from faggoted steel and if it had a hardened edge has never been thoroughly
investigated. Personally, I would be surprised if the better ones weren't made that way.

Iron, Steel and Swords script - Page 622

12.2.7 Experimental Tests of Old Steel and Swords
Testing Old Iron and Steel
While there is a lot of speculation (often erroneously put forward as facts) about the properties of old steels and swords,
there are very few experimental data. That is understandable as far as old swords are involved. They are precious
antiquities and no museum or collector enjoys to have his treasure destroyed. However, there is no excuse as far as
steel, and in particular not-so-old steel is concerned. Whenever an old building comes down (either by demolition or byearthquakes etc.), quite often old steel used for girders, wall anchors. and so on becomes available in quantity. In
general, however, the old steel goes to the junk yard and not to a laboratory.
Sometimes we also have large amounts of iron / steel from shipwrecks (e.g. Roman and Svedish steel) or from finding
the treasury of the old palace in Khorsabad filled with 160 tons of iron. There are also plenty of Celtic swords, sword
parts and in particular double-pyramid bars. Sacrificing some of that iron / steel for tensile tests would not constitute a
severe loss.
I'm only aware of one investigations with relevance for the topic here. It is the outstanding (like always) contributionof Vagn Fabricius Buchwald that I already discussed shortly before .
Below is the decisive figure once more, augmented by some more data, and a picture of fractured specimen.

Yield stress and tensile strength vs. maximum
elongation for three kinds of old wrought ironfrom 1750 - 1800 plus results from more moderniron
Source: Constructed from tables 11.210. - 11-23 plus table 14.7.
and other information as given in Buchwald's 2nd book (p 438441; 535

For comparison I included the properties of clean modern wrought iron (0% C, 0% P, 0.02 % Si, 0.0o2% Mn)
according to Buchwald, and a range of nominal Bessemer, Thomas and Siemens-Martin wrought iron with 0.1 % 0.25% C from 1897.
Below are pictures of tested specimen showing quite different behavior.

Iron, Steel and Swords script - Page 623

Some fractured specimen with very different
elongations.
Immediate brittle fracture in the middle
Source: Constructed from tables 11.210. - 11-23 plus table 14.7.
and other information as given in Buchwald's 2nd book (p 438441; 535

Buchwald obtained his specimen from old (Norwegian) churches. They were made from pig iron in one of the many
ways used (and described here). But details do not matter. This actually not-so-old "wrought iron" can be seen as
typical for all old iron, including the really old stuff made in a bloomery and not in a blast furnace. It isheterogeneous with regard to the carbon (and possibly phosphorous) content, and it contains inclusions of slag andwhatever on top. What we see is:
Properties vary widely. We have completely brittle (zero elongation) material and samples coming close tomodern wrought iron.
Properties may be quite different even for samples cut from the same piece of raw material.
The old iron is typically quite harder than modern clean iron. It just is quite dirty, in other words.
Bessemer and colleagues did not only make mass production possible, their methods also increased
substantially the qualityof the iron produced.
So much for old wrought iron, the major product of all old iron smelters. What about steel ? Well - I don't know. I'm notaware of any mechanical tests concerning old steel.
We know that the ancients treated steel as something different from iron, and that they were somehow able to sort raw
iron into grades of steel. Making a pattern-welded sword demanded to have phosphorous steel and mild steel (orwrought iron) for making the striped rods typically used for evolving a pattern, and hard steel for the edge. Did they pick
the proper pieces from various parts of one bloom (like the Japanese) or did they run dedicated bloomeries for making
different kinds of the raw material? I don't know.
Could the old smiths assess the quality of a given steel? How? I could think of possible answers but in essence I just
don't know.
All things considered I tend to believe that the quality of old steel was not substantially better than that of wroughtiron. Quite possibly smiths payed more attention to quality issues when they forged a sword and not just somegirder for some church. One way of doing that is to go for the (expensive) stuff of some special supplier who just hadthat superior steel.
But nothing helps. As long as you have slag inclusions, maybe some phosphorous, and carbon concentrations
varying inside a given batch and from batch to batch, you had steel that was on average just as inferior toIron, Steel and Swords script - Page 624

homogeneous modern steel than its wrought iron counterpart. That does not preclude - just as in the wrought ironcase above - that some pieces were of rather good quality, and that rather good swords have been made in some"schools" here and there, or by some individual smiths who were particularly good (or lucky).
"What about crucible or wootz steel?" It certainly was more homogeneous and free of large slag inclusion and so on.
Yes, but if not treated exactly right at every step in the production to a blade, it was simply hard and brittle. I'm notaware of any mechanical tests of old wootz ingots or finished old blades. The tests done by Prof. Zschokke and reported
here were, most likely done with 19th century blades, and all those blades tested rather badly in all aspects whencompared to modern normal steel blades. And that includes hardness!
There is no reason to assume that much older wootz steel and the blades made from it where substantially better.
However, only serious tests will tell.
So far it looks like all of antiquity had to resign itself to be stuck with iron and steel that was inferior to what we havenowadays. Since they did not know how good iron or steel could be, they just lived with it. Whatever they had wasstill a lot better than bronze, the only contender here. That is evidenced quite convincingly by the observation thatbronze weapons disappeared completely after iron and steel technology had reached first maturity around 800 BC.
The thing to do then was to work on perfecting and advancing what you had. On the smelting part, selecting andtreating the ore and all the other stuff going into your bloomery became more sophisticated, jus as the design andthe running of the bloomery. On the forging part, various composite technologies developed into a high art in somecases. Prime examples are the pattern welded swords of the Celts / Romans / Alemannis and (early) Vikings; the"soft core / hard outside" all-steel swords of the Carolingians and their successors in Europe, and the Japanesenihomotos.
The obvious question now is:

How do composite constructions
perform in tests?

Testing Old Swords
I regret to say that there are very few if any tests of old composite swords that are not Japanese katanas. No big
surprise - we have almost no suitable European composite swords. The owners of the very few Celtic / Roman /Alemanni pattern-welded swords that would still be suitable for a bending tests (the Moesgaard Museum in Aarhus;
Denmark, comes to mind) would shoot you on sight if you suggest some destructive mechanical tests of their treasures.
As far as katanas are concerned, I have actually not found much either but that might be due to my lack ofunderstanding Japanese. One example (a bit confusing, though) of testing Japanese steel / katanas is given in reference
7
Same thing more or less for the Viking type composite sword, take the VLFBERHT's for example.
What we have are tests with newly-made composite structures including some where the steel was made in a (modern)bloomery. Tests of such composite swords or structures (see the references below ; all coming with links to the actual
papers) provide relatively clear answers
1. As far as the elastic limit and plastic deformation is concerned, composite swords are worse than single-material
swords
2. As far as fracture is concerned, mostly no advantage or just a small one is found.
That's pretty damning but in line with what I stated based on "theory" in the preceding sub-chapter. But is it true?
Well, there is no reason to doubt the experiments. They are just not always fully to the point. Not to mention that
there are only a few.
So let's look at the question a bit more carefully. Let's start by giving a quick look at undeniable advantages:
A blade made from homogeneous and hard but brittle steel will have a large yield stress and thus elastic limit but will
fracture almost instantaneously after the elastic limit is reached.
A blade made from soft homogeneous steel will yield at a lower stress but then deform plastically quite a lot before it
finally fractures. Upon fracture it has absorbed far more energy than the hard steel.
A blade made with soft steel inside and hard steel outside will fracture its outside at a stress lower than the yield stressof the hard steel but higher then the yield stress of the soft steel. That produces cracks on the outside. However, thesecracks will not penetrate the inside. Instead the blade bends or deforms otherwise plastically. It can absorb more energy
before it finally comes apart than a sword made only from the hard steel but less than a sword only made from the soft
steel.
I have just described in many words the "law of averages " once more. It is nicely illustrated with a picture frompublication 6 cited below. The layered composites are right in between the two "parent" steels with a closer affinity
to the weaker parent, actually.

Iron, Steel and Swords script - Page 625

Temperature influence on the fracture toughnessof modern steels (spring and tool steel) andcomposites ("dam. steel") made form them with84 or 168 layers, resp.
SourceThe question to ask once more is simple: Is our composite sword as discussed above better or worse than its twocounterparts made entirely from one of the two steels?. Can you answer straight away without giving it somethought?
Right.

It depends on what you are going to do with your sword!
This is an important point. What you typically are not going to do, is to subject it to tensile and bending tests. What
you are going to do, is to hit things with it and to have it hit by opponents blades. Upon impact in either case, large
forces act on small areas producing stresses that will often be above the yield point of the steel at the impact point.
You then much prefer local plastic deformation to fracture.
Being left with a sword that has some nicks or dents on its blade but is still in one piece is certainly advantageous
to a broken sword in a bloody life-and-death battle. That gives an "edge" to composite swords. However, if you are
an exceptionally big guy, you might be better of with a heavy hard steel-only blade that cuts through your opponents
lighter composite swords without suffering much damage, being very heavy and thick. And so on.
What about composite swords made from real (old) steel? Composites than make sense, up to a point. Just consider asimple examples. You use two different steels both of which contain "killer" defects somewhere that would induce
sudden fracture at low stress. Making a composite averages this locally "very bad" property typically with something
less bad. And that is better than very bad. Only if you happen to superimpose the "very bad" areas of both steels at thesame place, thing go very wrong. But that is unlikely as long as you have only a few "very bad" parts.
We used (and possibly still used) that kind of principle in the most advanced material of mankind: the gate "oxides"of the transistors in integrated grated circuits. they are extremely thin (just 30 or so atomic layers) and unavoidably
have a few defects where they go up in smoke at the working voltage. So make several layers (usually a silicone
oxide - silicon nitride - silicon oxide sandwich or "striped" layer. All three layers have defects but with just a little bitof luck never right on top of each other. The composite is able to take the "electric stress", i.e. the applied voltage.
You can now run through all kinds of other properties and get the same result. What's better depends on
circumstances. We know that, generally speaking, that there often are circumstances that favor composites. If it
wouldn't be so we would not have concrete , consisting of hard stones embedded in soft cement; steel enforced
concrete, or CFC and GFC (carbon or glass fiber composites). Nature would not have evolved wood , a supreme
composite material. The list goes on.

Iron, Steel and Swords script - Page 626

If you think about this for a minute, hard steel has all the properties you want - except fracture toughness and"lightness". There is nothing you can do about its density (determining the weight of your blade) by making acomposite with other kinds of steel because they have the same density, just as there is nothing you can do about
Young's modulus either. The high yield strength of hard steel is compromised by using it as part of a composite withsofter steel, so the only reason to go for a composite is fracture toughness. Here you might gain - but you pay for itwith the other properties.
Simple enough. Well - not quite. You also might gain in appearance (pattern welded swords just look much better),marginally in corrosion resistance (if you employ phosphorous steel), and you still may have the hard part in places
where it counts, e.g. at the cutting edge.
Not to forget, you might have the huge advantage that you can actually forge your sword. I have this nagging
suspicion that Japanese katanas simply would shatter upon quenching if they wouldn't have the soft core.

1)

Adam Thiele, Jiøí Hošek, Pawe Kucypera, László Dévényi : "The role of pattern-welding in historical swords –mechanical testing of materials used in their manufacture", Archaeometry, July 2014
Abstract
The pattern-welding is well known technique that was widely employed in manufacture of swords. While the decorative
effect of the genuine pattern-welding (employing phosphoric iron) is indisputable, its reinforcing effect is up to date rather
unclear. In order to understand this issue better, wrought iron, phosphoric iron, steel and various pattern-welded samples
were prepared, mechanically tested and the results obtained were discussed in detail. Both the mechanical testing andthe long-term metallographic investigation of medieval swords suggest that pattern-welding does not have any significant
positive effect on the mechanical properties of swords and we should consider it a primarily decorative technique.
Ádám Thiele, Jii Hošek: "Mechanical Properties of Medieval Bloomery Iron Materials - Comparative Tensile and Charpytests on Bloomery Iron Samples and S235JRG2", Periodica Polytechnica Mechanical Engineering, 59(1) (2015) pp. 3538,
Abstract
Ductility, toughness and strength of medieval bloomery iron materials were highly important mechanical properties,
strongly affected by their microstructure and chemical composition. An attempt was made to characterize the mostimportant mechanical properties of representative samples of main bloomery iron materials extracted in smelting
experiments and compare them to the well know reference modern steel of S235JRG2. It was confirmed that notching
and the stress concentration effect of slag inclusions strongly decrease all the characteristic values of ductility andtoughness of bloomery iron materials . Typical medieval bloomery P-iron is a brittle material with almost zero or very low
characteristic values of ductility and toughness but revealed similarly high strength as hardened and tempered bloomery
steel.

2)

F. Carreno , J. Chao, M. Pozuelo, O.A. Ruano: "Microstructure and fracture properties of an ultrahigh carbon
steel–mild steel laminated composite", Scripta Materialia 48 (2003) pp. 1135–1140
Abstract
A seven layer steel based (mild steel and ultrahigh carbon steel, UHCS) laminated composite was processed by rollbonding. Impact properties were improved in comparison with the UHCS. Delamination plays an important role bydeflecting cracks, absorbing energy and imposing the nucleation of new cracks in the next material layer.

3)Thomas Birch: "Does pattern-welding make Anglo-Saxon swords stronger?", This paper arises from work conducted in
2006-7 as part of an undergraduate dissertation under the supervision of Dr. Catherine Hills (Department of Archaeology,
University of Cambridge).
Abstract
The purpose of pattern-welding, used for the construction of some Anglo-Saxon swords, has yet to be fully resolved. One
suggestion is that the technique enhanced the mechanical properties of a blade. Another explanation is that patternwelding created a desired aesthetic appearance. In order to assess whether the technique affects mechanical properties,
this experimental study compared pattern-welded and plain forged blanks in a series of material tests. Specimens were
subject to tensile, Charpy and Vickers diamond hardness testing. This was to investigate the relative strength, ductility
and toughness of pattern-welding. The results were inconclusive, however the study revealed that the fracture
performance of patternwelding may owe to its use.
M. Zgraggen, S. Trüllinger: Influence of the number of layers on the notch toughness of layer Damascene or Welded
Damascene steel", · Praktische Metallographie 42(5), (may 2005), p 219-238
Abstract
Layer Damascene samples with, arithmetically, 13, 73, 145 and 973 layers were produced to determine the influence ofthe number of layers on the notch-impact toughness. The investigation studied the notch-impact strength of ISO-V
samples at room temperature, the microstructure, and the fractography of the fracture surfaces. Carbon diffusion between
layers and the loss of carbon resulting from the method of manufacture were analysed. It was shown that there is a clear
tendency to higher notch-toughness values as the number of layers increases.

Iron, Steel and Swords script - Page 627

J. Wadsworth and D. R. Lesuer: "Ancient and Modern Laminated Composites — From the Great Pyramid of Gizeh toY2K" This article was submitted to International Metallographic Society 1999 Conference, Cincinnati, OH, October 21 –November 3, 1999 March 14, 2000
Abstract
Laminated metal composites have been cited in antiquity; for example, a steel laminate that may date as far back as2750 B.C., was found in the Great Pyramid in Gizeh in 1837. A laminated shield containing bronze, tin, and gold layers,
is described in detail by Homer. Well-known examples of steel laminates, such as an Adze blade, dating to 400 B.C.canbe found in the literature. The Japanese sword is a laminated composite at several different levels and Merovingian blades
were composed of laminated steels. Other examples are also available, including composites from China, Thailand,
Indonesia, Germany, Britain, Belgium, France, and Persia. The concept of lamination to provide improved properties has
also found expression in modern materials. Of particular interest is the development of laminates including high carbon
and low carbon layers. These materials have unusual properties that are of engineering interest; they are similar toancient welded Damascus steels. The manufacture of collectable knives, labeled “welded Damascus”, has also been afocus of contemporary knifemakers. Additionally, in the Former Soviet Union, laminated composite designs have beenused in engineering applications. Each of the above areas will be briefly reviewed, and some of the metallurgical principles
will be described that underlie improvement in properties by lamination. Where appropriate, links are made between theseproperty improvements and those that may have been present in ancient artifacts.
Excerpts and comment"...It is to be noted that the tensile ductility of most of the laminated composites is lower than that predicted from the ruleof averages when the difference between ductility of the two components is large.""The dramatic improvement in the impact properties of the laminated composite is a result of notch blunting by extensive
delaminations that occur on either side of the initial crack direction in all samples.""Extensive delamination" means that the layers come apart extensively. Not everybody would agree that this is a"dramatic improvement in the impact properties".
6)

Rastislav Mintách, František Nový,*, Otakar Bokùvka, Mária Chalupová : IMPACT STRENGTH AND FAILUREANALYSIS OF WELDED DAMASCUS STEEL, Materials Engineering - Materiálové inžinierstvo 19 (2012) pp. 22 - 28
Abstract
The aim of this work was the experimental research of damascus steel from point of view of the structural analyze, impact
strength and failure analyzes. The damascus steel was produced by method of forged welding from STN 41 4260 spring
steel and STN 41 9312 tool steel. The damascus steel consisted of both 84 and 168 layers. The impact strength was
experimentally determined for original steels and damascus steels after heat treatment in dependence on temperature in
the range from -60 to 160 °C. It has been found that the impact strength of experimental steels decreased withdecreasing temperature behind with correlated change of damage mode. In the case of experimental tests performed athigh temperature ductile fracture was revealed and with decreasing temperature proportion of cleavage facets increased.
Only the STN 41 9312 steel did not show considerable difference in values of the impact strength with changing
temperature.

7)

Okayasu M, Sakai H and Tanaka T: Mechanical Properties of Samurai Swords (Carbon Steel) Made using a Traditional
Steelmaking Technology (tatara). J Material Sci Eng 2015, 4:2
Abstract
The material and mechanical properties of samurai swords (Japanese swords), made using a traditional steelmaking
technology (tatara), are investigated experimentally. The quality of these swords appears to be low because of thepresence of a large number of inclusions, including oxide- and phosphorus-based structures; however, their mechanicalproperties are relatively good because of their fine-grained structure and high residual stress. The swords consist of
several carbon steels, with a fine microstructural formation being obtained in the sharp edge of the sword (knife) as aresult of the forging process. There is high residual compressive stress in the thick edge of the sword (mandrel), causedby bending due to the martensitic phase transition in the sharp edge. The carbon content of the sword varies depending
on region: the sharp edge is found to have 0.55% C, which is more than twice the amount in the thick edge. The Vickers
hardness and tensile strength in the sharp edge region are about 6 and 1 GPa, respectively, which are about three times
higher than the corresponding values in the other regions of the sword. The hardness in the sharp edge region is almost
the same as in a conventional carbon steel (Fe-C0.55) produced by presentday steelmaking technology. The tensile
strength of the sharp edge of the sword is relatively high, but is slightly lower than that of the conventional Fe-C0.55 steel,despite the fine-grained structure and high residual compressive stress in the sharp edge region. This is caused by thepresence of various inclusions in the sword.

Iron, Steel and Swords script - Page 628

12.3 Dynamic Properties

12.3.1 Moving a Stick
General Movement = Translation plus Rotation
I need to make a comment first before I delve into the topic "Dynamic Properties of a Sword". While static properties still
are part of Materials Science, dynamic properties are not. How a sword bends, for example, depends on material
properties like Young's modulus (and the geometry expressed in the area moment of inertia). How a sword moves
depends only on its weight (distribution). In other words: Two swords made from completely different materials but withthe same weight and geometry handle or move in exactly the same way.
Since the focus here is on Materials Science, I tried to keep this subchapter short.
I failed. The topic is exceedingly complicated and it is almost impossible to describe the important parts without
equations. I tried anyway but needed to use many words.
When your sword moves, its movements can be described as a combination of a pure translation and a pure rotation.
Sounds a bit involved but the basics are very simple, just look at the pictures below:

Pure translation of a sword. There is no rotation
The center of mass is symbolized by a blue circle
The center of mass of the sword (blue point) moves along some line but the orientation of the sword in space does
not change. You know what is meant by "center of mass"; otherwise don't worry. I will get to it quite soon.
A translational movement contains all movements where the center of mass of something moves in any way. Up /down; left / right, to and fro, in a circle, whatever. A pure translational movement implies that the orientation of theobject in space must not change. Nothing rotates.
Here is a thought: All movements of a "point" are always translational. A point has no orientation in space and thus
cannot rotate. A ball could rotate, but a ball is not an infinitesimally small point. Now you know why physics
teachers and all and sundry love the "mass point" so much. You avoid having to cope with the difficult subjects ofrotating things.
If the center of mass moves, some net forces must act act on the object. Newtons's first law couples forces andmovement and allows to calculate what happens. When we consider the movements of a sword, it is useful todistinguish two kinds of forces:
1. Forces that act on the sword all the time. Gravity, for example, is always there acts on any point on your sword.
It wants to move your sword "down". Your hand around the grip is also always there and exerts force but only on
the grip all the time.
2. Short term forces. The best example is the force acting on the edge when you hit something. It lasts only ashort time.
The pictures that follow contain many arrows symbolizing forces. They cannot not distinguish between permanent andshort-term forces and you need to be aware of that.
The drawing above is simple and it's easy to imagine all kinds of movements in this way, including movement in three
dimensions. What's not so easy is to answer this question: How can you produce a pure translational movement likethe one shown above? Obviously some forces are required. This is right but I will add right away that those forces must
only act on the center of mass all the time for pure translational movements, i.e. if rotations are "forbidden".
Before I delve deeper into this, let's look at the case of pure rotation:

Iron, Steel and Swords script - Page 629

Pure rotation of a sword. There is no translation
The arrows symbolize the movement
You will have no problem to grasp this "pure rotation" concept. Did you notice that the rotation axis runs through thecenter of mass? Probably yes. But do you know that for pure rotations this is a must? The rotation axis must run
through the center of mass! Think about it. If it wouldn't do this the center of mass would move, and if the center of mass
moves, we have a translation and thus no longer a pure rotation.
How can you produce a pure rotational movement like this? If you remember finer details from physics, you will tellme that some moment of force is required, also known as torque, torsional moment or turning moment.
A moment of force is generally the product of the force causing a rotation times the distance of that force to the axisof rotation. That is a somewhat oversimplified and unscientific definition but it will be good enough for the time being.
We have encountered torques before, but only in the science section about beam bending.
For a pure rotation we actually need a force couple meaning two forces that are equal in magnitude and with
opposing directions. They then cancel each other to a net force of zero with respect to translation. Otherwise theobject would move and we wouldn't have a pure rotation anymore.
I'll get back to this in gruesome detail but first let's look a the general case of movements: translation and rotation are
somehow combined

Translational and rotational movement of aswordBlue arrows show movements

We have the simple picture from above but now the sword translates and rotates. You would have to apply proper(and somewhat crazy) forces that also produce torques to cause such a movement, and calculating what it would
take to cause such a movement is actually not all that easy.
In many cases of movement it certainly looks as if the object simply rotates around some point that is not the center ofmass. Think of your grandfather clock pendulum. It swings back and forth around a pivot point that is certainly not
located in the center of mass, of the pendulum. Describing its movement as a rotation around its center of mass plus atranslation of the centr of mass seems just not right. It appears to be overly complicated. I agree. It just wouldn't lookright.
So let's look at a case that is somewhat similar

Iron, Steel and Swords script - Page 630

Translational and rotational movement of asword thatcan bedescribed as "rotation around a pivot
point"
This certainly looks like a simple rotational movement around a clear axis or pivot point. Let's call it "pivot point
rotation". Having a name always makes things less scary.
Simple it may look but it is nevertheless is not a pure rotation around an axis at the tip of the sword. The center ofmass moves too (in a circle) and that is translation by definition. You have to supply a torque for the rotation but
also some forces acting on the center of mass to cause its movement in a circle. You actually know that force. It'sthe (negative) centrifugal force (then called centripetal force) you experience when you swing your kid around. In the
picture above the axis is experiencing that force.
The earth experiences the gravitational force from the sun when it circles around the sun. You simply need a force
that pulls the center of mass inwards towards the rotation axis to keep your kid (or the earth) form from flying off.
To make the point once more in a different way: It is perfectly possible (and "legal") to describe the movement in the
picture above as a pivot point rotation with a pivot point that does not coincide with the center of mass. In a moregeneral point of view you can describe any movement as a rotation around some instantaneous or apparent rotation
axis or pivot point that moves around in some way. It's a matter of preference and of being aware of the requiredchanges in the math. Just don't mix up a pure rotation, always around the center of mass, with a rotation aroundsome arbitrary axis.
Before I go on discussing sword movements, I need to give the center of mass a closer look. I'll do that in the next subchapter

Iron, Steel and Swords script - Page 631

12.3.2 Center of Mass
For starters test yourself if you know the meaning of "center of mass" (COM), also known as "center of gravity".
Where would you look for your personal center of mass? And how? I'll tell you how you could do it. It's not easy, though
You need to exercise a lot so you can perfectly stiffen your body. You should be able to do this:First step in determining your center of mass
Here you can see how it could be done
If you do it as shown above, you will actually feek a torque working on your stiff body that invariably would rotate you
and bring your lower end down. You need some magic to counter its effects. Your friendly neighborhood magician
might be able to help you here. Bit to make life it easier I allow you to abandon magic and to use a second chairright under your feet.
Stay rigid and now have a column with a pointed tip put right under your body somewhere in the middle. If you put
the tip right below your center of mass you will not tilt in one way or the other if the chairs are removed and you canrest in peace until the beer gets too warm. The vertical line from the tip through your body runs through your centerof mass.
This may take some practicing and possibly some drugs to keep you stiff

Second step in determining your center of mass
In a third step you do the experiment sideways, rotating 90o. The line from the tip through your body runs throughyour center of mass once more, and your center of mass is where the lines from the two experiments intersect
inside your body.
This can be a fun thing to do as long as it's not your center of mass your buddies try to find. Finding the center of massof your (straight) sword or any longish straight object that is not too heavy can be done in a much easier way, though.
Rest the object on a finger of your left and right hand, starting on the outside. Move your fingers together, easily sliding
along the object. The center of mass is right between your two fingers when they eventually meet.
This is shown below

Iron, Steel and Swords script - Page 632

Finding the center of mass of a straight sword
Easy enough. Whichever way you pick, the result is always the same: If an object is held right at its center of mass(or exactly below it), it does not rotate . It just stays in place without any movement.
No movement means there is no net force, and no rotation means there is no net torque.

The crucial word is net
We most definitely have forces in the pictures above! The legs are pulled down by gravity, and so is the head and justabout everything else. We also have torques. The weight of the head times the distance to the lever point provides for a
substantial torque; same for the feet and so on.
However, if we add all the forces and torques, including the force that the tip exerts upwards on the body, the net resultis exactly zero in both cases.
Of course there is a strict physical / mathematical definition of what constitutes a center of mass and how you
calculate it - consult the science module if you want to know. Here we focus on the essentials. All you need toknow is:1. If an object has some symmetry (like your typical straight double-edged sword, where the left half is themirror image of the right half), the center of mass will be in the symmetry plane (in the middle of the blade)
2. For a straight sword, the center of mass is closer to the heavier end. Sort of trivial, but:
3. For a curved sword, the center of mass might be outside the sword. Below is a case where it is exactly atthe edge. Change the mass distribution a bit (e.g. by taking off the hand guard at the hilt) and the center ofmass is outside the blade.

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A tegha (kind of oversized tulwar) resting on therubber end of a pencil
4. If you drop your sword, the center of mass will move down towards the earth (you knew that). The sword will
not rotate if their is no friction (supplying forces). Since the air does supply some friction, some rotation
might take place but we forget about that here.
5. If you want to produce specific motion patterns of your sword, i.e. make the center of mass move in a certain
way and make the sword rotate, for example doing what that Samurai does, you can ask a physicist to
calculate the force and torques you need to apply with your hands. She will tell you that this would be a very
complicated job to do and suggest to do something easier and more fun instead.
Now you can begin to see the problem I'm facing here. Most people can make all kinds of fancy movements with asword, a tennis racket or a hockey stick without any problems whatsoever. And they never waste a single thought on
the complex physics involved! They just do it. Your muscles produce movements of major parts of you plus rotations inyour wrists, elbows and shoulders in am exceedingly complex pattern of forces and torques. Unbelievably difficult to
calculate (or simulate; our present day robots would not yet make great sword fighters).
How am I supposed to teach you just the basics of what is involved? Without equations? You would need vector
calculus if not tensor algebra to deal with this stuff, so it would be hopeless anyway. So why bother?
Because there are limits of what your body / brain combination can do in the "auto" mode. And your "natural"reaction on how to hit something with the longish object you are wielding in order to achieve some desired effect(score a goal in hockey, send your tennis opponent into a remote corner, check your enemy...) might not be thebest way to "swing".
Getting to know the limits and finding out the best ways for swinging your stick necessitates to look into thephysics, unfortunately. And that, as remarked before, is not something easily done.

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12.3.3 Translational Movement
The Problem and How to Deal with It
Let's jump right into the deep water now. We consider a sword with some force acting on it for a short time. Something
like that:

Sword impacted by some (short lasting) force onsome impact point somewhere.
You may see that as the situation prevailing at the precise moment when you hit something right on what I called
the "impact point". To make things easy for starters, we assume that you released your grip a fraction of aseconds before impact, so your hand is not transmitting any forces on the sword at impact time. For the same
reason we do this experiment in outer space, so no gravity needs to be considered.
What is going to happen?
Not so easy to tell. Partially because I was deliberately vague about what one calls the starting condition.
Is the sword just sitting there at rest with no movement whatsoever and then, suddenly, out of the blue, some forc
hits it for a short time? That's what the picture implies. In this case the sword will move up ("translate") and rotate to
the left (or better "counter-clockwise") around its center of mass. After the force disappears, it would keep moving
and rotating at constant speed (we are in outer space, remember?).
Contrariwise, if the sword is actually swung down somehow, and the picture shows the moment of impact, the force
encountered will slow down both movements, the translational and the rotational one. If the target is someunwielding large mass, the velocity of the sword will have to come down to zero since it couldn't go below the
impact point. It could even reverse its movements to some extent; the sword then is "kicked back" or reflected.
Maybe everything could work together in such a way that the sword just comes to a complete rest in the position
shown?
Did I mention that sword movement physics is complicated? I think I did. So let's get at it systematically and slowly.
Here goes:
If we look at some body moving in a way we don't know much about, we are well advised to split the movement in two
parts that we then consider separately:
1. Pure translation of the center of mass
2. Pure rotation around the center of mass.
After we did that we add up the results in order to obtain the total movement. In this module we look at the translation
part in some detail; rotation will be the subject of the next module.
A pure translation results from forces acting on the center of mass and nowhere else. We do not have this situation in
the picture above so we need to generate it. How do we do that? By using a simple trick of physics. We "copy" theforce we have and apply this (yellow) "double" to the center of mass. In order to compensate for the excess force weapply a third (blue) force that is the "mirror" image of the double also to the center of mass. The two extra forces thus
cancel exactly and that's why we are allowed to do it.
Sounds a bit strange but is very powerful. Let's see why by looking at a picture of the situation

Adding a (yellow) force "double" at the COM andits (blue) compensation
Things look more complicated now. So what did we gain? Quite a lot because now we can split the situation in our
two cases. First we consider only what the "double" does:

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Looking at pure translation since there is notorque and only a net force acting on the COM
We have a force that acts right at the center of mass. It will only cause a pure translation in the direction of theforce. That's what we look into here. But, for sake of completeness, let's look at what's left over:Looking at pure rotation around the COM
because there is only a torque and no net force
Pretty cool, ain't it? We have "de-constructed" the problem into two separate problems. One deals with puretranslation, the other with pure rotation. Find the two solutions and then superimpose them for the grand total.
We will do just that. In this module we look at the pure translation, in the next one we will consider the rotation.
Translational Movement
We have the case of a force acting right on the center of mass (COM). What is going to happen? Well, as you all should
know, the force will move the object in its direction and, as long as it acts, it will increase the speed of the object at aconstant rate or acceleration. Very basic physics tells us that. A force acting on an object causes a constantacceleration of that object that is proportional to the force and inversely proportional to its mass. This is Newton's firstlaw, after all. You can't get more basic than that.
In other words. If, as in the picture below, we start with velocity equal to zero at the start, we have some velocity v1 andsome distance covered after 1 second, After two seconds we have doubled the velocity and quadrupled the distance.
After 3 second we have three-fold velocity and 9-fold distance. And so on - as long as the force acts on the sword.

Purely translational sword movement
On bottom the "mass point" analogy is shown
So the force shown acts on the same point of the sword all the time! and points in the same direction all the time! .
Easy to draw - but can that be? If you supply the force, you must move your arm out, or move your whole person, or dosome combination. Note that it is not good enough to "keep up" with your rapidly disappearing sword but you must to
keep pushing at all the time with the same force, meaning you must accelerate just as much as the sword. Obviously
you can't do that for very long..
Gravity, however can do just that. Just turn the picture by 90o to the right and you have a well-known situation: gravity
pulling at your sword (and everything else):
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Sword movement in gravity

The top part shows schematically how gravity pulls at every piece of the sword. Lots of force arrows but no torque.
You can come up with as many force times distance to the COM products as you like but if you add them all up,
they will always come out to zero. That is the definition of the COM, after all.
That's why we may simplify the problem by having the full "weight" pulling at the center of mass only as shown. Now
we have the good old mass-point problem. Without air and therefore friction, the sword will fall with increasing
velocity towards the source of the gravitation, i.e. the center of the earth until it hits a surface.
So it's actually not just a possible situation, it's a situation that is always there since you (and I) cannot switch off
gravity as long as we are running around on the planet earth.
Gravity pulling at your sword (and you) is always there. What it does is relatively easy to figure out. It is, however,quite unimportant when we look at what you do with your sword. The forces encountered in sword fights, or bypracticing sword fights, are far larger than the gravitational forces. You can put your blade on the neck of somedelinquent for as long as you like but no head will roll because gravity pulls the blade down. You have to supply
forces substantially larger than those supplied by gravity to see some action. In what follows we will therefore
neglect gravitational forces most of the time.
When you use a sword (or an axe, a golf club, a tennis racket, or a hockey stick, or...) you usually hold it on one end(the hilt). Neglecting gravity, all forces acting on the sword thus concentrate on the hilt, some distance away from thecenter of mass. When you forcefully move your sword, these forces must be far larger than the gravitational force pullingat your sword. And yet, gravity will give a respectable speed (around 4 km/hr or 1.1 m/s) to your sword, when it
accidentally falls down.
You might believe that with the much larger forces from your hand you can make your sword moving arbitrarily fast? No,
you can't. All objects resist to being pushed around by forces, and some objects resist more than others.
In the universe we occupy the degree of resistance objects put up to pure translational movements depends on one
object property only, that can be expressed in one simple number; the mass of the object!
Couldn't be easier! The shape, the density, the kind of material the object is made from, the weight, and so on, doesn't
matter. It's the mass and only the mass that affects translational movements. Double the mass and the velocity after
one second is half of what it was, the distance covered is a quarter of what it was, and so on.
Now wait a second! The weight doesn't matter? No it doesn't. It is just a measure of the force that gravity puts on agiven mass close to the surface of the earth. In outer space the weight of your sword is close to zero, but its massis the same as on earth or wherever. Its resistance to forces is the same too, even if it is weightless.
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The very simple relation between force F, mass m and acceleration a has a name, by the way. It's called

Newton's First Law 1)

Newton's first law states that force equals mass times acceleration or acceleration equals force divided by mass.
Couldn't be simpler.
Notice once more that it's the mass and not the weight of the object we are discussing here. The weight of an
object is just another word for the force it experiences in some gravity. Your weight on the moon is quite different
from that on the earth (the gravity there is much smaller), your mass is the same, however.
Notice once more that I'm talking about movements by translation only. As soon as rotation comes into play, therules change substantially!
Of course you have vague memories from high-school physics that there is something called Newton's first law, andthat it somehow relates to the movement of mass points. The earth running around the sun was surely brought up, withboth earth and sun imagined as points in space, imbued with some mass. Then you assumed that those two masspoints interact via gravitational forces and solved the resulting differential equation for various boundary and starting
conditions.
Ha ha. Very funny. You had trouble enough figuring out why the earth runs around the sun without fancy math. But even
if you would go through all of the above, using up quite some space on the black board for all the lengthy equations, you
still would not arrive at the well-known fact that the earth also rotates around its own axis exactly once a day. Just
another reminder that we are only discussing translational movements here.
The force you can apply to your sword is larger than what gravity can do, but it is still limited. This limits the speed yoursword can attain. Consider an almost massless sword. How fast can you make it move? Certainly no faster than you
can move yourself running at top speed (at best around 35 km / hr). Now consider a 100 pound sword. How fast can you
make it move? Right.
How fast can you make your fist move? Whatever number you come up with, your fist holding a sword cannot possibly
move faster. We see a first criterion for selecting the proper mass for your sword: It should hardly slow down the velocity
that your body (parts) can attain without it. That allows you to attain maximum speed before impact and to release theforces you apply just before impact since you have already obtained maximum speed. This is a smart thing to do (forexample when you chop wood with an axe) because that will minimize the impact on your wrist and arms at the
moment of contact.
That calls for a small mass. However, don't make the mass too small! Having a kind of long feather as a sword willallow you maximum translational speed but your opponent is not all that afraid of getting hit. Also, do not forget, that
we are still talking translational, and only translational movements here. As soon as we look at rotation, moreconditions for the optimal mass will appear and in the end we have to look for the best compromise.
Movement Without Forces
You have applied some force to your sword, making it move (with you attached) but now you let it go. No more forces
are acting on it . What will it do?
Well, it will fly off and fall down. That's because there are still forces acting on it. One is gravity, making it fall down,
the other one is friction. The friction comes from the air. It's not large for a sword but it's there. Use a feather insteadof a sword and you will see.
So once more we have to resort to outer space. What will happen then is easy: The center of gravity of your sword
will keep moving with exactly the velocity - magnitude and direction - it had at the moment you let go. It's called:

Law of momentum conservation

Momentum is velocity times mass and it simply gets preserved, i.e. will not change as long as no forces are acting
on the object. You might recall that the energy gets preserved, too. That is correct but here momentum is thedecisive property.

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No more needs to be said. The momentum you imparted on your sword by the forces you supplied will be preserved
until impact (forget the rather tiny contributions from gravity and friction). The thing to note is that the momentum (andthe energy) will even be preserved during (and after) impact but not just for the initial single object (your sword) but thewhole system (your sword, the object hit, possible attachments to the object hit, and so forth).

1)

Isaac Newton: F = m · a; m = F / a; a = F / m

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12.3.4 Rotational Movement
Rotation With Torques
Here we look at a pure rotation of some object. That means, by definition:
1. Its center of mass doesn't move at all. You only will observe that if there are no net forces acting on the object.
Once more the emphasis is on "net".
2. The object must rotate around its center of mass. Otherwise the center of mass would move, something we justexcluded!
That leaves only one way of introducing a pure rotation: Apply (at least) two forces, equal in magnitude but different
in sign (= direction) at some distance from the center of gravity as shown schematically below. And have them act
always at right angles to the objects geometric axis, i.e. the forces rotate with the object. Only then you have aconstant torque in time.

Pure rotation of sword
As long as the torque is acting on the sword it will rotate around its center of mass with increasing angularvelocity. Torques cause accelerations of the angular velocity just as forces cause accelerations of the "normal"
velocity.
The angular velocity comes in whenever things move in a circle, it is simply how large an angle is covered in a timeunit. You might cover 35o in a second or just 6o per second. That would make 6o · 60 = 360 o per minute or one fullcircle. Then you would call it 1 round per minute or 1 rpm. Now you know.
We now must ask ourselves: how does everything depend on the forces used? Well - wrong question. Not totally wrong,of course, just a bit awkward. The better question is: How do rotational movements of arbitrary bodies depend on thetorque it experiences?
Before I go into that, I will give some more consideration to the meaning of "torque ". Of course, all the nuts out there
know what a torque is, and so do the bolts. You can even buy wrenches that allow to apply a pre-defined torque, like theone shown below

Applying defined torques

A torque comes up when something needs to be turned around a pivot and is simply defined as force (measured in
Newton, N) times distance (measured in meter, m) between the point the force acts on and the pivot point. A torqueis thus is measured in Nm - Newtonmeter; see the picture above. This is very clear to everybody who has evertightened a nut.
Unfortunately it is also very misleading. We need to be very careful here. The familiar process of tightening a nut
with a wrench like the one shown does involve a torque but it does not speed up your nut and makes it rotate fasterand faster. And the sum of all forces isn't zero either - only one big force is applied, after all. It nevertheless works
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because there is always a lot of friction involved and because you do not just move the nut around but also your tool
(not to mention parts of you), and the wrench is typically much heavier than the nut. Not to mention that the object
the nut belongs to (like your car) is rather heavy and "tied down" by brakes (= lots of friction) so it doesn't movedespite the force acting on it not being zero.
So sorry, but the "nuts and bolts" kind of experience with torques doesn't get us very far here. We need to look at the"ideal" situation of applying torques to objects. Ideally some object (e.g. a sword or just a long rod) in outer space (nogravity / friction) that is manipulated by massless ghosts applying forces / torques, for example as shown below:

Torques more abstract
Not that this is a picture of equations, which is not thesame thingas using equations!

Two forces act on our rod. They have equal strength (= equal length of the arrows) but opposite signs so their sum iszero. No net forces, no movement of the center of mass (COM).
Now we will make a distinction that's a bit outside of standard physics but will help to keep the issues clear. We call thetorque produced by a set of forces that add up to zero a "pure torque"
Pure torques thus can only cause pure rotations around the center of mass. Pure torques by necessity consists of twoparts. We have :force F1 times its distance l 1 to the COM (that must act as the pivot point), and F2 times its distancel2. The total torque is the sum of the two single ones.
Now I need to mention something rather strange, certainly not obvious: Every point on the object above feels thesame torque. I show why in the picture below; skip it if you feel out of your depth, It is not important for what follows.

A force couple with F 1 = –F2 causing a pure
torque T. Its value is thesame for any point on the blade !
Amazingly enough, the toque for any point is the same. Since the sword here must rotate around its center of mass
(there is no net force since the forces F 1 and F2 add up to zero) it doesn't matter in the case above where you
attach the forces as long as the distance between them is the same.
All we need to know is that the presence of a torque does not automatically define the axis of rotation. In the caseof pure rotations it can only be the axis through the center of mass, but for pivot rotations, the far more interestingcase I will get into shortly, the rotation axis through the pivot point must be found by other means.
The pictures above give hints of how to simplify things tremendously. Since torques are for rotary movements what
forces are for straight movements, it is advantageous to describe them with little arrows too. That is simple. Take thetorque arrow to run along the axis of rotation and make its length proportional to the magnitude of the torque. The
direction can be tied to a clockwise or a counterclockwise rotations. Doing that makes the math a lot easier (provided
you have some idea about vector, or even better, tensor calculus).
We use representations like this:Iron, Steel and Swords script - Page 641

Arrows parallel to the rotation axis represent
possible torques. The length symbolizes themagnitude in Nm.
One more thing. The second picture above could be interpreted as showing the torque your hands impose on the hilt ofyour sword. Well, almost - but not quite for two reasons:
1. When you hold your sword at the grip you must indeed apply a torque to counter the torque felt by your wrist due
to the mass of your sword. The force of gravity pulls the center of mass down and you have to counter that tokeep your sword horizontal. That needs not just a torque but also a net force as we shall soon see. The sword in
the picture above is obviously kept in outer space since there is no gravity. Under the conditions shown it would
start to rotate.
The sword shown below does feel gravity. See if you can figure out what else it shows.
2. You might be able to produce forces / torques like that shown (two) above or right below for starters. The forces
will make your sword move and rotate. But there is no way you can keep the torque constant for any appreciable
span of time because that would mean that your hand, producing the forces, rotates with the sword.
A constant net torque is not something you or I can supply. A tricky contraption with a kind of "round sword"
inside a housing, featuring magnets and coils with some current running through them might come close to
applying a constant torque all the time. We would call that an electrical motor. A gasoline engine can also do
this. The crankshaft of your car supplies a constant torque to the wheels and so on. But you and I can't do that.
Handling your sword (or anything else) in real life just doesn't encounter constant torques in no-friction, no-gravity
environments. You rather have changing torques and forces, acting for short times only. Things in real life are just notthat easy. That's why it is far more difficult to be a human than a God.

Forces while holding your sword horzontallyat rest with gravity pulling downwards.
Consider what it means to just holding your sword horizontally. The pivot point would be around your forefinger /thumb and there you must add a force countering the force of gravity acting on the center of mass. But just putting
your forefinger under the hilt there would keep the pivot point at rest but the sword would rotate "down". To counterthat you must "push down", i.e. apply a downward force F1 at the "other end" of your fist; above your pinky finger.
How large it needs to be is easily calculated, the result is shown.
But your sword doesn't move and no movement means that there are no net forces and no net torques. Nothinghelps but to add a force of magnitude - F1 on the pivot point.
So if you want to move your sword just up and down without rotating it, you simply increase the force at the pivot
point. If you want to rotate it only, you increase the force a the pivot point and with exactly the same (negative)
amount at your pinky. If you want to move and rotate, ....

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Don't get scared. I'm only doing the simple things here. All we need to know for pure rotational movements (notranslations) is:
A pure torque acting on your sword will make it rotate around its center of mass (COM) with increasing angularvelocity.
The rotation can be around any axis that runs through the COM since the torque (seen as an arrow) can have any
direction.
As long as the torque acts on the sword, the rotational speed will increase (we assume no friction) or decrease if
the torque is applied "the other way around" to a spinning object.
This increase / decrease or acceleration of the rotational speed is proportional to the torque and some property ofthe body called "moment of inertia" that takes into account the mass of the body and how it is distributed.
Yes! All of the stuff above was only to ease you into the concept of theMoment of inertia

In short, the moment of inertia is for rotations what the mass is for translations. Since you rotate your sword far morethan you translate it. As far as handling is concerned, its moment of inertia is the most important property of your sword
since you usually rotate or "swing" it quite a lot.
We will need to spend some time on this. There are difficulties, however.
The moment of inertia, unlike the mass, is not just a simple number that one can attribute or assign to some given
object. The best one can do for a given sword is to come up with one number relative to some rotational axis running
through the center of mass. Change the rotational axis and the number changes.
Seems there are an infinity of moments of inertia for my sword - after all there are infinitely many possible rotational
axes? Well - no! At most 6 numbers take care of the moments of inertia for any object. Fewer numbers are required
for an object with some symmetry; for a sphere (maximum symmetry) one number would suffice.
Why is that? Well, the moment of inertia, in contrast to properties like mass or temperature, is not a "scalar", given
by one number. It isn't a vector either, like the velocity, where you need three numbers (the components of thevelocity for the three axes of space), worse, it is a tensor needing 9 numbers if things are really bad!
Oh f...! You certainly do not want to go this deeply into math. Well, don't worry, be happy. I'll get you there without too
much pain.
Rotation Without Torques
You have applied some torque to your sword, making it rotate, but now you let it go. No more torques are acting on it.
What will it do?
Same question as before for forces and translational movement. Well, the answer is much the same too.
It will keep rotating with the rotational speed it had before you let go. And no matter what kind of rotational axis was
active while you "worked" your sword, it will now rotate around an axis running through the center of mass. Here isan illustration of that. Otherwise the center of mass would move, which can't be because no net forces are around in
our ideal situation.
In real life your sword will fly off, rotating to be sure, and eventually fall down. That's because you cannot possibly
apply a torque only with no net forces. Moreover, there is always gravity, making it fall down, and we have friction.
The friction comes from the air. It's not large for a sword but it's there. Use a feather instead of a sword and you willsee.
If we resort to outer space once more what will happen then is easy: You sword will keep rotating with exactly the
angular momentum it had at the moment you let go. It's called:

Law of angular momentum preservation

Angular momentum is angular speed times moment of inertia and it simply gets preserved, i.e. will not change, aslong as no torques are acting on the object.
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No more needs to be said. You may have a beer now.
Then we proceed to a thorough discussion of the moment of inertia.

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12.3.5 Moment of Inertia
What is the Moment of Inertia?
The moment of inertia, sometimes also called angular mass or rotational inertia, is an intrinsic property of everythingthat has a mass and a defined body or shape. We know it's a tensor but for the time being we treat it as a number thatcan be used to describe a specific property of a body just like other numbers defining, for example, its mass, volume,
Young's modulus, color, bra size or average income.
Bodies with the same mass can have very different moments of inertia, as they can have different volumes, colors, orsex appeal coefficients.
The following picture gives an idea of what needs to be taken into account when we determine the moment of inertia of agiven body.
Consider the bodies shown below. A longish rod with a mass of 100 something (kg, g, pounds, ounces,...), various
spheres at the end of a thin and essentially massless rod, always with a total mass of 100 and the center of massright in the middle, plus a body. Guess what kind of torque it needs to make all these bodies rotate in the same way("with equal acceleration of the rotational speed") around the axes indicated. I've indicated my guess by the lengthof the torque arrows.
There is no way to guess the exact length of the torque arrows but one thing is certain: It's far easier to rotate therod around its long axis that around its center, or the one big sphere in comparison with two spheres far out on thethin rod.
The effort or torque needed to obtain a certain acceleration of the rotational speed is directly proportional to themoment of inertia. The length of the red arrows in the picture below thus also symbolize the moment of inertia of thebodies considered for the rotational axes shown.

Rotating bodies with equal mass but different
moments of inertia
The rotation axis runs through the center of mass inall examples
The picture also makes clear that one and the same body can have quite different moments of inertia. Giving only
one number thus implies that you also give the rotational axis.
As a rule of thumb we can state that the distance of masses from the rotational axis is what counts for the moment ofinertia. Far-out masses are more difficult to spin around than masses close to the axis. In fact, the distance from therotation axis counts quadratically. Double it, and you need four times the effort because the moment of inertia
quadruples..
Calculating the moment of inertia for any object (relative to a given axis) is easily done if you follow this simple recipe:
Divide you body into tiny cubes (think of it being made by tiny Legoblocks).
Take the mass of a cube and multiply it by the square of the distance tothat particular rotational axis running through the center of mass that you
have in mind.
This gives you a number with the unit kg · m2. Write down that number.
Repeat the procedure for all the other blocks that you needed to produce
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Science Link
Moment ofinertiathe body.
Add up all the numbers. The result gives you the moment of inertia in unitsof kg · m2 with respect to the axis chosen.
Of course, if you know the least little bit about calculus, you know that the recipe above tells you to do an integral
and that all of the above reduces to an equation shorter than the words "moment of inertia". How that works isshown in the science link.
However, it's far easier to measure the moment of inertia of your sword than to calculate it. How that is done I will isoutlined in a science link and here.
Now let's look at the only really important point in all of that:

The moment of inertia is forrotational movements
what the mass is fortranslational movements.
When you pitch a spear, a baseball or a stone (translational movement) you "feel" essentially the mass of theobject opposing the force you exert. It's more difficult to get larger masses moving.
When you rotate a gyro or your sword, it's the moment of inertia that you feel opposing the torque you apply. It's
more difficult to get larger moments of inertia spinning.
Of course, the moment of inertia contains the mass of the object. But how that mass is distributed relative to therotation axis is also part of the moment of inertia, and that is usually more important than the mass.
If you are still with me, you may have noted that we still have two major problems with respect to the moment of inertia
of our swords:
1. There are many (in fact infinitely many) possible rotation axis one can run through the center of mass of somebody. In the picture above two are shown for the rod and the body. The rotational behavior of the two cases, andthus the moment of inertia, will be quite different. We need two numbers for two axes! Three number for threeaxes and so on? In contrast, if we rotate a perfect sphere, all axes' are equal - only one number for the momentof inertia is needed for all possible axes!
2. Using my sword, I rarely rotate it around the center of mass. I rather rotate it around an axis or pivot point in thehilt (because I rotate my wrist) or an axis not even inside the sword, like an axis running through my elbow orshoulder. Generally, I can rotate it around any axis I can think of. Another infinity of possibilities and infinitely
many moments of inertia?
Good questions. The answers are obvious and simple - for people with some background in physics and aknowledge of tensor algebra.
Here we go:
1. The moment of inertia happens to be a tensor - a collection of at most 9 "normal" numbers; but already 6 or
fewer will do in our case. A tensor is a mathematical entity a bit more advanced than a vector (somethingneeding three "normal numbers" to define it) but still rather basic stuff and just a kind of advanced number.
2. If you know the moment of inertia tensor for rotations around axes running through the center of mass, you
can easily calculate its value for any axis. Well, maybe you can't, but I and my buddies have no problem
here.
So the moment of inertia is a "number" as stated above, just not your usual or "normal" boring kind. You haveencountered that before. You would give the velocity of your car as a normal number - 123 km/h for example - but on
closer consideration you realize that velocity is a vector - an entity that needs three "normal" numbers to fully describe
its magnitude (123 here) and the spatial direction of the movement. Typically you give the components of the velocity
along the three axes of some coordinate system - three numbers!
The moment of inertia is a tensor, something a bit more complex than a vector but still in that mathematical league
where "normal" numbers or scalars are known as tensors of 0th rank, vectors are of 1st rank, tensors like the moment ofinertia (or stress and strain tensors) are of 2nd rank, and so on.
The moment of inertia thus is an entity uniquely associated with some body of material. We need to know it if we want
to do any calculations involving rotations of the body. Young's modulus, to give another example, also turned out to be atensor upon closer inspection. Young's modulus is actually a tensor of 4th rank, needing up to 21 "normal" numbers orscalars to fully describe it.

Iron, Steel and Swords script - Page 646

Working with the Moment of Inertia
Now to the good news: Not all axes of rotation are equal! You may have infinitely many axes running through the centerof mass of some body but one or two immediately catch the eye if that body is not completely irregular but has somesymmetry. Let's look at some examples:

Principal axes
Those special axes are called "principal axes" and - surprise - one of them will correspond to the largest possible
moment of inertia the body can have, another one to the smallest, and the third one to something in between. As itturns out (after some heavy math), only rotations around principal axes are stable, and the one around the axis withthe largest or smallest moment of inertia is the most stable.
If two of the three moments of inertia are identical (e.g. for cylinders or bodies shaped like an egg) only the axis withthe unique value of the moment of inertia is stable.
What does "stable" mean in this context? Well, nothing whatsoever as long as we look at rotations of rigid bodies infrictionless outer space. Things change if we look at the rotation of real bodies in an environment with some (ever sosmall) friction.
Bodies rotating around some arbitrary axis in an environment with gravitation and some (small) friction or otherdisturbances (like wind blowing), will start to wobble and eventually rotate around the axis with either the largest,
smallest or unique moment of inertia.
That's part of the reason why a hard-boiled egg induced to spin while lying on its side will upright itself eventually andstand on its tip. It's actually far more complicated but here is where the fun starts. Spinning objects can do very strange
things!

Rotating egg standing on its tip
Thank God (or me) we don't have to delve into this. As long as the rotational speed is not very large we do not have toworry much about stable and unstable axes, centrifugal forces, and all the exciting stuff relating to "gyroscopes".
Iron, Steel and Swords script - Page 647

When you swing your sword, inducing a rotational movement, you swing it through a fraction of a full circle in a
fraction of a second. Its rotational speed is thus around one round per second or 60 rpm. That does not qualify aslarge rotational speed so we forget about the complexities alluded to above.
We need to delve into one more aspect of the moment of inertial though. You now understand why your battle-axe, when
you throw it, would fly like this:Playing with an axe
On top we see a thrown axe, first rotating around a pivot point close to your fist but after release, in free flight,
rotating around its center of mass. This is a stable rotation because the rotation axis is not only a principal axis but
the one with the largest moment of inertia. In the second and third example the axe also rotates around principal
axes but its flight is less stable. It would probably start to wobble. Of course, nobody ever throws an axe like this(how would you do it?).
The Rotation Axis Does Not run Through the Center of Mass
Finally I'm moving up to the real world! You got it by now that any movement can be de-constructed into a puretranslation and a pure rotation but ther are many movements that look very much like being just a rotation and why
should you describe that as a mixture? Think of a clock pendulum, your ride on a merry-go-round, the dials of yourwatch. We called these rotations "pivot point rotations". I will get to that in detail in then next subchapter, here I only
need to point out the good news:

You can describe pivot point rotations
with the moment of inertia too!

Let's look at meaningful pivot point rotations now. Whatever we look at then rotates around a fixed axis somewhere; at apivot point that need not be identical to the center of mass. Here are examples:

Iron, Steel and Swords script - Page 648

Rotations around pivot points
In the left case the pivot point coincides with thecenter of mass. In the right case the pivot point is
outside the object (sword), possibly in your elbow. The
middle would correspond to rotations from the wrist.
For all three cases we need a torque. You could imagine that torque to be delivered by a crankshaft perpendicular to thescreen and ending on the pivot point. If you can imagine this, you just as well can imagine the torque being an arrow in
crank-shaft direction, "sitting" on the pivot point with a length that is proportional to the value of the torque applied. That's
just how I described a torque way up in the text.
If your muscles are somehow involved in delivering the torque, they will definitely feel an increasing resistance to arotational movement if the distance between the center of mass and the pivot point increases. We know already thatthe resistance for rotations around the center of mass was given by the moment of inertia for that rotation axis. For
rotations around some other axis or pivot point as shown we need to use the "parallel axis theorem" ("Satz vonSteiner" in German), and that is a rather simple theorem.
It states that the moment of inertia for some axis is given by the moment of inertia for an axis running through the centerof mass parallel to the axis considered, plus mass times the distance between the axes squared.
Let's look at an example: If your axes or pivot point of your 1 kg sword is 10 cm away from the center of mass, you add
1 kg · (0.1 m)2= 0.02 kgm2 to the moment of inertia given for the center of mass.
You don't have to delve into this. All it means is that it gets quadratically more difficult to swing your sword or axe withincreasing distance between the pivotal point of your choice and the center of mass. That already explains why it is fareasier to swing a sword with a certain weight than an axe with the same weight. In the first case the center of mass is
not very far from the hilt were we have the pivot point; in the second case the distance is large.
We are getting closer to being able to discuss the "handling" of elongated object like swords, axes, or golf clubs,
the "feeling" you get swinging them around, and why small differences in the geometry may matter a lot. Before wedo this, however, we need to delve a bit deeper into the dynamics of these objects. Partially just for fun, partiallybecause there are still a few useful things to learn.
Illustrating the Moment of Inertia and the Parallel Axis Theorem
It is very illuminating to look at a few numbers now. Let us take an average sword with a weight or better mass of 1 kg.
A bit on the light side but I'm going to use easy numbers here. The density of iron is ρiron = 7,78 g/cm3 and thatdemands a volume of V = 128,5 cm3. The moment of inertia then depends on how we spread out that volume and where
we choose to have the rotation axis.
Below the results for three basic geometries are shown, more details can be found here. We have a simple sphere, a"blade" with two axes of rotation, and a "club" or "axe" with the whole weight at the end of a 100 cm long "weightless
stick. Here are the numbers:
Isphere=4 kgcm2·

Iblue= 84,7 kgcm2

Ired= Iblue + 1 kg · (50 cm)2 = 2 585 kgcm2

Iclub

=

10 004 kgcm2

We have a variation of the moment of inertia from around 4 kgcm2 to 10 000 kgcm2; an easy factor of 2 500! Rememberthat it is the moment of inertia that resists your efforts to swing something! The shape of your sword does matter a lot
for its handling and even details may matter far more then "meets the eye".

Iron, Steel and Swords script - Page 649

12.3.6 Translational and Rotational Movement
Grand Synthesis and the Pivot Point
I'm going to use our example from before to consider now the combination of pure translation and pure rotation for thegeneral case. I'll just rotate the picture by 90o to provide some diversifications. What we get is:

Combining pure translation and pure rotation to
the total movement
Clear enough (I hope). The sword moves some and rotates some around the center of mass; what you get after someshort time is what you see on the right. .
What you also see is that for that particular moment in time you could just as well have described the movement asa rotation around the "pivot point" outlined in the drawing. A movement like that could be considered to be just a
rotation around the pivot point. It could be achieved by only considering the torque you get by multiplying the force F
by the distance t between impact point and pivot point. Graphically, with the torque shown as vector, it looks likethis:

Combining pure translation and pure rotation to
the total movement
The moment of inertia opposing the rotation now needs to be determined by the "parallel axis theorem" and thatbrings us right back to the preceding sub-chapter.
This looks like a smart thing to do - we get the total movement in one fell swoop instead of going through two cases
separately followed by adding them up. Well - simple pictures are often deceiving! Doing real calculations for this is notas simple as it looks in the picture because:
1. You don't know the position of the pivot point without calculating it first.
2. Here it changes with time; it is not a fixed point!
Nevertheless, the pivot point you get right after impact is of prime importance. I will devote the next sub-chapter to it(where I'm going to rename it to "percussion point").
Iron, Steel and Swords script - Page 650

There is, however, a simple if a bit violent way to keep the simplicity of the picture above. Nail down the system(literally!) by fixing some pivot point. Force whatever is going to rotate to do that around a fixed axis or pivot point.
You then simply enforce a pivot point rotations. Look at the examples already provided to see this. Here I'm justgoing to repeat some of that stuff to make it stick.
Can you see that all pivot point rotations have one thing in common?

The center of mass moves in a circle!

You can produce this movement with a single torque acting on the axis, and you can calculate the rotational speeds
etc. by using the relation between torque, moment of inertia for the pivot of your choice. You don't have to introduce
forces, even so the center of mass actually moves. That doesn't mean there aren't forces. Your "nail" providing the pivot
point might experience severe forces but as long as it holds up, you just can ignore that.
But your rotating object (and you, if you are attached to that object because it is your sword) will experience forces. You
know that force, it is the centrifugal force. You will even experience the centrifugal force after you took the torqueaway; for zero torque. The system then rotates with constant angular speed and the center of mass also moves in its
circle with constant angular speed. But that doesn't mean that its velocity is now constant. It has the same magnitude,
yes, but it changes directions all the time. That counts as change of speed and thus acceleration and necessitates aforce - the centrifugal force

Centrifugal forces are needed forchanging the direction of thevelocity, they don't affect themagnitude of the velocity!

We don't have to worry much about centrifugal forces, however, because for typical sword masses and rotational
speeds they are not all that large.
Apparent Center of Rotation
Going all the way back to that Samurai swinging his katana in a wide arc, we see that the center of mass does not quite
move in a circle, but it is not all that far off. So it is not a simple pivot point rotation but maybe we can come up withsome way to describe this movement as some other simple kind of rotation?.
Here is the picture once more:Iron, Steel and Swords script - Page 651

The red line describes the movement of thecenter of mass of the sword
Source: Internet at large

What we need to do is to define the "apparent center of rotation"., also known as "instantaneous center ofrotation".Easy. Draw a line through the object (here the length of the sword) at some moment in time, and repeat theprocedure a short moment after. Where the two lines intersect, you have the apparent center of rotation for the point intime chosen. If we do that for the Samurai, we get the following result:

Apparent center of rotation
The green stars correspond to the intersection pointsof the green lines running through successive
positions of the katana
Surprise! While it does appear that the Samurai swings his katana by rotating his arm plus katana around hisshoulder, the apparent center of rotation of the katana is rather close to the wrist. What we have is a combination ofrotations around three pivot points: Shoulder, elbow, and wrist.
Notice that the distance between the apparent center of rotation and the center of mass is about the same of mostof the swing, meaning that the Samurai experiences about the same moment of inertia throughout.
Now you have a first glimpse into ways of analyzing sword performance. We needed to do that so we can move up to
the next two important quantities: The percussion point and the effective mass of your sword.

Iron, Steel and Swords script - Page 652

12.3.7 Percussion Point
Let's start by reconsidering our "experiment" from before. We hit something and that means applying a force for a shorttime to our sword at an impact point. We hit a point well down on the blade like this:Basic experiment to derive the percussion point
We know by now that this induces:
1. A translational movement in the direction of the force arrow.
2. A (here counterclockwise) rotation around the center of mass.
We look now once more on what that means right after the hit, i.e. at a time where the movements are still very small.
What we get looks (schematically and exaggeratedly) like this:Iron, Steel and Swords script - Page 653

Results of basic experiment and deriving the
percussion point
The translation only (shown with red arrows at the center of mass) moves the sword a bit to the right. The rotation
only rotates the sword around the center of mass, and the combined movement translates and rotates. Nothing new
here.
However, the drawing shows that there is a point on the hilt, that we now call percussion point, that has not moved
at all. That is so because at this special point, the two movements cancel. The translation to the right is just as
large as the movement of that point per rotation to the left.
We now have two special points on our sword: an "impact point" below the center of mass, and corresponding tothis point and only this point, a percussion point above the center of mass. Basic physics tells us that theexperiment also works in "reverse". Make the present percussion point the impact point and you will find that the old
impact point is now the percussion point. Change the position of one point, and the position of the other one
changes as well. In other words:

There is no single percussion point.
Percussion points always comepaired to a pivot point
When we consider a sword we usually talk about its percussion point, i.e. only one point, and that is always a point
down on the blade and not, as in the picture above, on the hilt. How come?
Well, when we consider swords, we hit things with the blade and hold the sword at the hilt. When we rotate thesword around the percussion point and hit something right at the impact point, we do not feel forces or torques in
our hand because the percussion point that does not experience forces, is right inside our hand. That is a majorstatement and we need to look at that in more detail below. But first let's look a bit more on general things.
In order to use the conventional nomenclature we now change the naming of the points as follows:"Pivot point" = the "point" on the hilt where you rotate the sword around (the percussion point in the drawing
above). Usually close to your thumb and thus cross guard.
Percussion point = corresponding point on the blade (the impact point in the drawing above).
We can do that because the two points are completely interchangeable. If you take the upper point as pivot point,
the percussions point is down on the blade. If you would rotate around this point on the blade, the percussions point
would now be at the hilt. Since we rarely do this, the naming as defined above makes sense.
Yes, it is a bit confusing but not quite as confusing as most of the stuff you read on the Net. Just to make it veryclear, here is a picture showing that plus the two decisive lengths coming with it:

Iron, Steel and Swords script - Page 654

Major "points" on your sword
Now we have three points on the sword that are of overwhelming importance to its handling. Let's see why. But first I
need to make clear that the most important properties of your sword are
1. its mass m, and
2. its moment of inertia I relative to the center of mass. This concerns the distribution of the mass in space and thisis determined by the basic geometry that also determines the position of the center of mass (one of our threepoints in the drawing above).
When we now start to consider how to optimize a sword for actual sword fights, it is good to realize that you do not havemuch choice with respect to the mass. Your sword should be as heavy as it can be considering that you must be able
to handle it for some time. The mass thus is a very personal thing but given within narrow limits like 0.8 kg - 1.5 kg..
The basic geometry is also your personal choice. You want it long or short, straight or curved, slender or broad, forwhatever reasons of your own. OK - that defines the basic geometry to a large amount. Now the "fine-tuning" starts.
Realizing that the pivot point is rather fixed (close to the cross-guard), you are now looking for getting a good
position for the center of mass and the percussion point of your sword. These parameters are now the mostimportant properties of your sword after you picked mass and basic geometry (always assuming you use yoursword for actually fighting and not just for showing off). Why?
The position of the center of mass relative to the pivot point, together with the moment of inertia, is crucial for thehandling as far as rotations are concerned. You want it relatively close to the hilt but not too close because thatprevents to have a good location of the percussion point and the ability to deliver large energy on impact.
The position of the percussion point is probably the most important parameter. You want to hit your target close to thispoint because then you don't feel jarring forces in your hands that tire you quickly if not breaking your wrist. You alsodeliver substantial or even maximum impact energy.
Obviously you want the percussion point not too far from the tip of your swords because there is sense in having a long
blade if you need to hit targets on a point way up on the blade.
Nothing helps. We need to figure out how to find the position of the percussion point (relative
to a pivot point on the hilt). For a given sword there are two ways for doing that:
1. Calculate the percussion point position.
2. Find the percussion point position by some experiment
The Science link shows how to do the basic calculation. It's actually easier than thecalculation for the center of mass or the moment of inertia. In essence, we want to calculate
the distance b between the center of mass position and the percussion point position as
Iron, Steel and Swords script - Page 655

Science Link
Percussion
pointshown in the drawing above.
How you can find the percussion point experimentally is explained here
What theory gives us are essentially the following rules:
1. The distance b between the center of mass position and the percussion point position is directly proportional tothe moment of inertia. Since we tend to keep the moment of inertia small, this tends to move the percussion
point "up", i.e. closer to center of mass.
2. The distance b between the center of mass position and the percussion point position is inversely proportional tothe mass m. Reducing the mass thus tends to move the percussion point "down". However, reducing the mass
also reduces the moment of inertia and that moves the percussion point "up". Both effects tend to cancel eachother.
3. The distance b between the center of mass position and the percussion point position is inversely proportional tothe distance p between the center of mass and the pivot point. Making this distance smaller / larger moves thepercussion point down / up on the blade.
Where does that leave us? Can we produce a sword with a given mass and a basic general geometry and then adjust
the the position of the percussion points (or center of mass point) while not changing the position of the others by somefine-tuning of the shape? The answer is simple

No !!!

Make a change to some parameter - the length or width of the blade, the tapering of the blade, the weight of thepommel and so on - and you change the moment of inertia, the position of the center of mass, and the position of
the percussions point (for the given position of the pivot point).
Optimizing your sword is not an easy thing, in particular if you consider that there are two more points - the nodes ofthe second-order oscillations dealt with in the next sub-chapter) - that should have special positions.
I will get to that in more detail later. For the time being we just note that medieval or older swords are often wonderfully
optimized with respect to all these parameters, while some of the modern replicas, looking pretty much like the original,
are rather bad. What that tells us is:

Optimizing your sword means:
Details matter!

Working With the Percussion Point
Look at what I had called the "basic experiment to derive the percussion point" again. Something is hit by a sword at the"impact point", later called percussion point". Or is it?
Simple pictures are often deceiving (while sophisticated pictures are incomprehensible). I see a sword at rest impacted
somehow by a force. No hitting there. The next picture goes with that interpretation. The sword, originally at rest, starts
to move in a combination of a translation to the right and a rotation around the center of mass.
It is quite illuminating to look at this more closely. The picture below shows what happens:

Movement of sword (in outer space) upon a short
impactIron, Steel and Swords script - Page 656

The sword increases both velocities - translational speed straight to the right and rotational velocity around the center ofmass - as long as the force lasts. Then it keeps moving with whatever velocities it acquired, spinning and moving forever.
The red dotted line traces the movement of the pommel to give some idea.
if we wouldn't be in outer space but on earth, the sword would do exactly the same thing plus falling down withincreasing velocity downwards (while still doing its spinning and moving to the right) until it hits the ground. The center ofmass would run on a downwards (parabolic) curve.
Note that we only have a "pivot" or "percussion" point, a point that doesn't' move at all, for the first moment of
impact.
Now, for contrast, let's look at the case where the force is there for some time and always at a right angle to the blade.
We have a constant torque in other words. What happens then is shown below

Movement of sword (in outer space) for aconstant torque
Interesting, isn't it? The sword moves in a circle with the apparent center of rotation being the percussion point. We havea pivot point rotation, in other words. It is still a rotation around the center of mass plus a translation of the center ofmass. The translation is not just to the right as before but changes directions all the time since the force changes its
direction all the time too.
Now you see the full meaning of the "percussion point". As long as the torque is on, it won't move. You also see why
the percussion point is sometimes called "center of oscillation". More to that here
What happens if the torque stops? Exactly the same thing as in the first case except that the sword will now fly off(spinning all time) in the direction its center of mass was moving at the moment the torque stops.
What happens if we come back from outer space and turn gravity on? Well - the sword falls down. You probably
could have guessed that. We can prevent that if we "nail down" the percussion point (now better called pivot point)
as described before. The nail or better rotation axis then exerts a force (and feels a force; actio = reaction to quote
Newton to the cognoscenti here) that exactly cancels the gravitational force pulling down.
This was possibly helpful but certainly needed. Now we will finally hit something with our sword. I need to distinguishtow (extreme) cases:
1. Very shortly before impact you completely release your sword. Your body, arm and wrist movement stops andyou open your fist. I know you can't do that perfectly but you should try. I have no problem doing that in my brain
and then writing down what will happen.
2. You stick to your sword and you try to keep it moving at the impact moment.
The first case we have already dealt with. It may come as a surprise but in simple mechanics (what we are doing here),time is reversible. All calculations work just as well in reverse. If you make a movie of some calculated movement,
nobody could tell if you run it normally or in reverse.
All we need to do then is to run the picture from above in reverse. I will only show the final scene just before impact. For
varieties sake I reverse the direction. Here goes:

Iron, Steel and Swords script - Page 657

Sword hitting something
I assume that the sword impacts the target at the first dashed line and then cuts its way inside until it comes to afull stop. And that's indeed what would happen. The force put up by the target would last as long as needed to stop
all movement. If your hand was just about "hovering" over the grip,. it wouldn't feel much since the hilt around thepercussion point is not doing much during impact.
That was cutting for some distance into a relatively soft object. Now let's consider what happens if you hit a big
stone. The distance for stopping the movement then gets rather small, so all we have to do is take off the twodashed lines on the left as well as the force arrow on the middle positions. The sword then must stop all movement
instantaneously. ????
You know that can't be true. Your sword will fracture, bend, kick back like crazy or do other unwelcome things but it will
not just stop with your hand not feeling anything at the hilt. I agree. Nevertheless, theory tells us unambiguously thatrigid bodies do just that. And that was the assumption behind all the "theory" so far. We are dealing with rigid bodies,things that do not deform or break or have any internal properties. There are no rigid bodies in nature but doing theory
with real bodies is just far messier if not simply impossible. A good steel sword, however, is an almost rigid body undermany circumstances and that's why we can use that approximation in many cases.
Rigid body theory is actually pretty good as long as the bodies in question do not experience forces that more orless destroy themThat, however, is what happens if you hit a solid rock forcefully with your sword. Hit it hard with the percussion point
or in any other way you like. You probably have a good feeling of what is going to happen without doing any
calculations and you certainly will not like the result.
Let's look a the second case. You are still attached to your sword and trying to keep it moving. Imagine you swing yoursword with closed eyes. You don't know when you are going to hit something and just keep swinging to with all you
have. Now we have three problems:
1. You are definitely feeling something in your hands and body at impact. After all, the sword by itself might havecome to a smooth stop if you found the percussion point, but that doesn't apply to your hands and body. Thatneeds to be stopped too and that needs some force.
2. All calculations for the percussion point and so on are no longer fully valid because parts of your body are now
parts of the system.
3. Taking that into account is difficult to impossible because you do not have an almost rigid body (like your sword).
We would need to use the "slime bag" approximation and that is notoriously very difficult.
One last topic needs clarifying. We always consider pivot points at the hilt and discuss what you will feel in your wrist
when you hit something. Hitting things at the percussion point is favorable because it minmizes forces to your wrist. Allof that is true. And yet, the apparent center of rotation for many movements is not at the wrist but closer to the elbow,
as shown here, for example. Shouldn't we consider pivot points further up and jarring of the elbow?
No, we shouldn't. The reason for this can be found in the old "beam bending" science modules. The force acting on
the impact point tries to bend the blade and that implies that forces and in particular torques "travel" up (and down)
the blade, producing some (small) elastic deformations. And these forces and torques is what your wrist will feel, nomatter where the apparent center of rotation is situated. You elbow might feel it too, but will notice it less because
this joint is just much stronger than the wrist.
All things considered, having an optimized percussion point position on your sword is a good thing. It won't do miracles,
however. For all the reasons considered here and because we need to add the next point: vibrations of sword before wecan discuss final optimization .
Iron, Steel and Swords script - Page 658

12.3.8 Vibrations
The Basics
In most of the modules in this section your sword was treated as a "rigid body". It could not deform or change its shapein any form. From a Materials Science point of view it was a boring dead object with only 2 boring properties: mass andshape, i.e. mass distribution. Your sword, however, is at least an elastic object. It deforms elastically to some extent
when forces are applied. Worse, it even may deform plastically or even fracture but this we will still neglect.
The elastic properties we cannot neglect any longer because they are the reasons for the vibrations of the blade(and the handle) you may encounter whenever you hit something sufficient hard. You may see the blade actually
vibrating and you will feel vibrations in your hand. If your life depends on your sword (and your ability to wield it), youwill pay a lot of attention to this subject since it is a major point (and problem) in a sword fight.
So what can I tell you on this subject? Certainly that it is very complex if you want to look at it quantitatively, i.e. derive
numbers. That's why I'm keeping this short and qualitative.
Let's start with an experiment. Hold your sword up and hit the blade on its flat part hard with a hammer or something. Or
simply throw it down on the ground. Changes are that you will see the blade vibrating roughly like thisVibrations (Sword seen sideways)
We see what is called a "second harmonic" and the question is what this means. And why we don't see the first or
seventeenth harmonic. The we have tow more special points in the sword, called "vibrations nodes" in the picture
above. How do they relate to all the other points that we already discussed, e.g. the percussion point?
Tough questions. Let's start by considering in a very general way what will happen to (reasonable) objects if they are
shaken by something with a given frequency ϖ. Take your spouse and shake him because he deserved it for one reason
or the other. The frequency then is rather low and you spouse will just wiggle with the frequency you employ. The
second you stop shaking, he will stop wiggling. This is because the wiggles or oscillations he performed while forced areheavily damped, i.e. decay rapidly without external influences. Every oscillating body will stop oscillating sooner (heavy
damping) or later (small damping) when the forces causing the oscillations are stopped. If you're not sure about themeaning of terms like frequency, wavelength, destructive interference and so on, consult the basic module outlined
below.
If strong or weakdamping is
experienced
depends on theoscillation
frequency, theobjects geometry
and the material
properties of theobject. In the caseof your spouse, thematerial properties
dominate by far
and cause heavy
damping at all(reasonable)
frequencies. The
reason for this issimple: yourhusband is a slime
bag! You knew that
all along but now
you have theirrevocable proof.
There is no
stiffness or
hardness in his
body (at least mostof the time and in

Basic Link
Waves

Iron, Steel and Swords script - Page 659

most of the body),
and that always
causes heavy
damping.
So let's look for something more rewarding then your spouse when you shake it. A bell, for example. Something likethis:

Big bell
Source: Internet at large

In order to save time, we don't just shake it with one frequency, then with another one and so on to figure out its
response, we shake it with many superimposed frequencies in parallel. Any physicist will tell you that this amounts tohitting it with a hammer. If you watch closely (very closely) you will see that the bell vibrates with all frequencies while
you hit but that right after the hit, vibrations with most frequencies "die out", i.e. are heavily damped and disappear, whilea few with some particular frequencies last for quite a while.
You know that because you hear it. The bell rings with a well-defined pleasant tone after being hit with a hammer orsomething (in contrast to your spouse who won't ring or produce pleasant tones of any kind upon being hit with ahammer). The vibrating bell makes the air around it vibrate too, and that is what you hear as long as the frequencies arein the auditory region of roughly 20 Hz to 20.000 Hz. The bell rings with a clear tone or basic frequency (plus a few"harmonics") and not with all the frequencies that were contained in whatever caused the vibrations. The reason behind
this phenomena is that only some particular and special frequencies, the "Eigenfrequencies" of the bell, can "live" inthere for a long time (several seconds instead of just milliseconds for all the other frequencies). You might say that all
frequencies except a few Eigenfrequencies are heavily damped. Two questions emerge:
1. What determines the Eigenfrequencies of the bell (or any other object, in particular musical instruments)?
2. Why are all other frequencies heavily damped?
It's actually only one question, just asked in different ways. The answer is simple in principle:
1. Besides Young's modulus of the material (and a few other minor material contributions), it is the shape, thegeometry of the object, that determines the Eigenfrequencies.
2. All frequencies besides the Eigenfrequencies cancel themselves by "destructive" interference and therefore
disappear very quickly
Easy enough in principle and devilishly difficult to calculate for non-trivial geometries in more than one dimension.
Now we know that all "elastic" or "hard" objects, including your sword but not you slime-bag spouse, can vibrate withsome special Eigenfrequencies. They do so in what is called "Eigenmodes ". A vibration means that some points on
the objects are moving back and forth with the Eigenfrequency of the Eigenmode but not necessarily that all points do
this. In fact, some points will not move at all - we have "nodes" of no movement.
Another strange word. "Eigen"-frequency, "Eigen"-mode (not to mention Eigenvector, Eigenvalues, and so on. Well,
you just experience mixed German - English words. "Eigen " is German and means "own" in both sense of theenglish word: it's your own and you own it. Just a little historical reminder that large parts of modern Math andPhysics were originally conceived in the true language.
For one-dimensional systems like strings the nodes correspond to points on the string; this can be seen in the picture
above. For two-dimensional objects like the drumhead of drums, the nodes are lines. It looks like this:Iron, Steel and Swords script - Page 660

The nodes (black lines) on a vibrating drumhead
Made visible by coating it with a black powder thatcollects in the nodes.
Source: Internet; see inset in the picture

Looks complicated, is complicated. But you have seen nothing yet. Look at the picture below, showing the nodes for a
lot of Eigenmodes of a vibrating square blade:

The nodes on a vibrating square plate
Pretty, but try to calculate that!
Source: As above

The real fun, however, starts when you look at three-dimensional objects like your sword. Before we do that we givesomething much simpler a quick look: A hollow sphere. Think of an ocarina if you like to consider musical instruments.
Its Eigenmodes now produce surfaces of no vibrations (or alternatively maximal amplitudes of the vibrations). It look likethis:

Iron, Steel and Swords script - Page 661

Some Eigenmodes (known as sphericalharmonics) "living" in a sphere
Source: "Kugelwellenfunktionen"; basic (advanced) math stuff

Some of you now might feel that they have seen a picture like this before, just in a completely different context.
Well, yes. Above you actually get a glimpse into the basics of quantum mechanics. Look it up here.
Three last words before we look at the vibrations of a sword.

1. There is always an Eigenmode with the lowest frequency. We may call that the fundamental mode or frequency.
It defines often (but not always) the musical note or pitch you hear. The Eigenmodes with higher frequencies we sortaccording to frequency and call them first, second, third, ... harmonics. In simple systems like vibrating strings theirfrequency is doubled, trebled and so on relative to the fundamental frequency.

2. The Eigenmodes of a given body depend to some extent on the confinements (boundary conditions in math lingo) of
this body. You might hold the hilt of your sword in a vice to study its vibration modes, i.e. forcefully reducing theamplitude of any vibrations to zero a this defined point. You might also "clamp" the tip, any point in the blade, or
nothing at all. You will get different Eigenmodes and different Eigenfrequencies. The picture below gives an idea forthis. In the middle you have a mode sometimes called "diving board" mode.

Fundamental Eigenmodes of a (schematic) sword
seen sideways with different "boundary
conditions"

3. Vibrations are not restricted to "up and down" as shown in all those pictures. The blade could also rotate
rhythmically (torsion vibrations) or get periodically shorter and longer. This is not really going to happen in any
appreciable way with a real sword -but it is a possibility.
All these possible vibration states are Eigenmodes with some Eigenfrequency. And yes, it is fairly complicated. It getseven more complicated when you ask which of these many possible modes actually get "excited" and live for some time
when you do something to your sword, like hitting something with it.
But now to the two good news: .

Iron, Steel and Swords script - Page 662

1.
Forget most modes. The important ones
are the fundamental modes
and a few low-order harmonics
2.
It is sufficient to treat swords as
one-dimensional objects

Vibrations of Your Sword
What can I tell you about the vibrations of your sword? Not all that much. First of all it is rather complicated as all the
stuff above should have made clear. Second, doing the full theory of your swords vibration modes and so on is possible
but involved. You need a computer and powerful software. Vincent Le Chevalier can do it 4); an example of his work isshown below. If the results help you very much in your day-to-day experience of wielding your sword is open to question.
Not only does the way you move and hold your sword influence what is going on vibration-wise, what you perceive ishighly subjective and thus cannot be predicted by theory. The rather heated ongoing discussion in various forums bears
witness to this.
In what follows I just run you through some points that are important to understand the topic and to put it into
perspective with the other properties of a sword.
The first point to notice is that usually just the basic modes of vibration perpendicular to the blade are considered, as
shown in the picture below on the left. Let's call that side-to-side oscillations or simply blade oscillations. It is easy tomake your sword vibrate that way: Hold it around the cross guard and hit the pommel hard with your hand. It will vibrate
as shown in the right-hand side of the picture below. This is a screen-shot from a very useful Youtube Video 2), one ofmany posted by Matt Easton. You should definitely see it

Vibrations (Sword seen sideways)

Iron, Steel and Swords script - Page 663

Part of apicture fromPeter
Johnsson /Le
Chevalier's
work 1)

Matt Easton of Schola Gladiatoria in
one of his Youtube videos 2)

Reproducedwith gracious
permission of
the authors.

The drawing illustrates what is know as the "second harmonic". It is "second" because it has two nodes. It is also
considered to be the major vibration mode in swords. Matt Eaton's sword in the picture seems to be doing a "divingboard mode" but in the video you see second harmonics too. Note that modes can coexist; you typically may findseveral modes superimposed.
The frequency of side-to-side or blade vibrations in low-index modes like the second harmonic is rather low, at bestaround 10 HZ or so. Definitely far below anything that would make a kind of musical noise. No singing sword 3) here.
You induce these modes by any (sudden) force with a component vertical to the blade, for example when you hit
something not exactly at a right angle relative to the blade and away from the two nodes. Of course, when you deflect
your opponents swing with the flat of your blade, you will excite these modes too.
What these modes really look like can be seen very nicely in some computer simulations done by Vincent Le Chevalier4):

Calculated blade vibrations for a sword with andwithout pommel and crossguard
Source: Adopted from Le Chevalier's work 1) with friendly
permission.

Shown are the vibration maximums for the 2nd, 3rd and 4th mode (somewhat exaggerated). You see that the nodes forthe 2nd mode of the pure blade are very roughly at about 1/4 and 3/4 of the blade length and that adding cross guard
and pommel changes the location of the hilt nodes more than that of the blade modes.
The simulation also shows how the positions of the center of mass (COM) and of the percussions points (for two fixedhilt pivot points) changes. Quite a bit! With a "proper" pommel and cross guard, the COM moves appreciably closer tothe hilt, increasing the agility of the sword, while the blade percussion point move out to a position pretty much identicalto the blade node. That is a bit fortuitous but exactly what you want.
We get a first impression that the kind of hilt you supply is of prime importance to the dynamic performance of yoursword. I will get back to this later in more detail.

Iron, Steel and Swords script - Page 664

The major point is that we now have two more major points on our sword (besides the two trivial ones giving the
beginning and end of the sword). We have the position of the hilt node and of the blade node addition to the three points
discussed before (pivot point, center of mass, percussion point). The claim is that any stick or sword has these fiveimportant points! Can that be true? That's where a lot of confusion starts. So let me clarify:
For a simple homogenous stick, three out of the five points are "trivial" . The center of mass is exactly in the middle, andthe nodes of the second harmonic are found at 1/4 and 3/4 of the length. That leaves two "special" points: An arbitrarily
located pivot point of your choosing and the corresponding percussion point.
For a real sword this is different. All five points are special. They are related, of course, because the defined geometry ofa sword determines most of the calculations. There is, however, no obvious relation.
Yes, you got it, I do actually claim

Vibrations nodes are generally not at theposition of the percussion point!
This is often claimed or somehow mixed up because it is desirable that the percussion point and the blade vibration
node coincide. That has caused sword makers to design their swords in such a way that these points actually are close
to each other. This is possible (see the picture above) but not necessarily an easy thing to do. Producing such a"harmonically balanced" sword, as it is sometimes called, needs either centuries of experience and "know-how" or a
powerful computer plus somebody who can program it with the required physics.
Why would we want these two points to be close together (and not too far from the sword tip)? Because if you hit
your target a the percussion point you feel no force in your hand and deliver substantial if not maximum impact.
When you hit your target at the position of the node you do not excite (second order) vibrations of the blade, hurtingyour hand and diminishing impact force. So having the points coincide is often a very good idea. But you have to do
this by optimizing the sword design. There is no natural and unavoidable coincidence of these points.
As Michael Tinker Pearce (Sword Maker) puts it in a "Sword Forum International" contribution: What harmonic
Balance does for a sword - prevents shock from being transmitted to the users hand when striking with the sword.
This conserves energy- the sword doesn't 'waste' energy shaking the user even when the strike lands off of theCOM. It also prevents the user from losing control of the sword because of vibration transmitted to the user's hand. It
also minimizes the sword's tendency to damage it's hilt assembly through vibration. All good things! A sword that is
not 'harmonically balanced' is not, in my opinion, a 'good' sword.
Modern experts (like Matt Easton and in particular Geoge L. Turner) who have given old swords a close look findthat pretty much all of them are harmonically balanced while that is not true at all for many modern "replicas". The
may look like the original but their balance is off. Their percussion point may even be off the blade, e.g. some cm infront of the tip (perfectly possible: look at the math!) I
Now I want to promote a new and somewhat disturbing idea. If you excite side-to-side or blade vibrations as discussed
above and then quickly put your ear on the blade, you might actually hear a tone. Maybe you can even produce a
directly audible tone with your particular "singing" sword. That can only mean that you have some "high-frequency" (e.g.
around 100 - 400 Hz) Eigenmodes that can live in your sword in addition to your very low frequency blade oscillation
modes.
The only contender for these modes are "edge-to-edge" vibrations. Something like that:

Fundamental Eigenmode of "edge-to-edge"
oscillations
You excite these modes when you hit something with the edge of your blade. They thus may come more naturally
then the side-to-side oscillations from above - but are rarely mentioned! Perhaps because their amplitude is so smallthat you don't see it easily - in contrast to the blade oscillations where the amplitude can easily exceed several
centimeters!
Now to my last point. Maybe you should forget most of what I have written above!?
The claim is: While side-to-side oscillations are showy and bothersome, what you really should worry about are theedge-to-edge oscillations. They are the ones that "sting" your hand or otherwise impede your performance.
That's the viewpoint of Geoge L. Turner, who so far has written the most detailed treatise about sword dynamics. Lookup chapter 11; pp 130 - 137pages. While his viewpoint is still open to some doubt; I do believe that he makes a goodand valid point.

Iron, Steel and Swords script - Page 665

So you should worry about the nodes for the second harmonics of the edge-to-edge vibrations and not about thenodes of the blade vibrations? Yes you should. But not too much, because the positions of the nodes is likely quite
close for most sword geometries.
I'm stopping here. Much more could be said (for example that so far we treated a sword essentially as a onedimensional object).

1)Peter Johnsson and Vincent Le Chevalier: Documenting the dynamics of swords; Vincent Le Chevalier' blog "Ensis Sub
Caelo".

2)

The link to the video is: https://www.youtube.com/watch?v=j4zwyVw4NdA It worked in Feb., 2019 but I can give no
guarantee

3)

The Singing Sword is the primary weapon of the fictional character Prince Valiant, a Knight of the Round Table in theservice of King Arthur, in the long running comic strip Prince Valiant, created by Hal Foster in 1937.

4)

Vincent Le Chevalier; : Simulating Sword Properties. Explaining how the simulation program works and in particular some
information about vibration modes computation.

Iron, Steel and Swords script - Page 666

12.4 Wielding Your Sword

12.4.1 The Effective Mass or Apparent Inertia
What is the Effective Mass?
Finally! In this last subchapter we are going to wield a sword. First we will just swing it around to get a feeling of how it
handles but then we will actually hit something or somebody with it. For example you. Right on the head. That will give
us an idea of what I mean with the term "effective mass" or "apparent inertia" in the headline.
I'm going to use Damocles sword to hit you with. To make it easier for me (and you) I will use an idealized version ofthat, just a plain, uniform rod. Consider it dangling above your head in various positions relative to your head, and then
the thin string rips. What will you experience?

Damocles sword hits you
Note that my drawings are gender mainstreamed
Let's start with the center of mass (COM) of the sword exactly above your head as in the upper pictures above. In theideal physical world so beloved by basic physics teachers, the sword will hit you and come to rest in the dent on yourhead. That happens because your mass is much larger than that of the sword, and your head is rather soft. What you
fell is painful since the total energy of the falling sword is transferred to your head. This energy is directly given by by the
total mass of the sword. If you remember anything from your physics teaching, you know that it is simply mass m times
the distance d between the hanging sword and your head (times the constant acceleration of gravity = 9.81 m / s2). Thispotential energy of the sword relative to your head is converted to kinetic energy (one-half of mass times velocity
squared), and that's what you feel.
Note that the sword is rather stupid, It doesn't know if its velocity just before impact is due to free fall in earth's gravity or
because somebody is moving it with his hands.
Now let's consider what you experience if the swords COM is not lined up with your head as in the lower pictures above.
The sword will hit you somewhere along its length and then tumble down rotating. What do you feel? An impact lesspainful then the first one. The pain decreases with the distance between the COM of the sword and the point where
it hits you. The least pain is encountered if you are hit by its very end.
How can that be? After all, the energy of the sword at the moment of impact is the same in all scenarios? Yes, indeed but not all of that energy is transferred to your head. Some kinetic energy remains in the sword because it keeps moving
and some rotational energy is building up. It is not too difficult to calculate what exactly is happening for a simple
uniform rod, a sword, an axe, or whatever. I'll do that in an science module but here I'll keep it simple
And I have good
news: There is aningenious shortcut:
Since any point of afalling object has theIron, Steel and Swords script - Page 667

And I have good
news: There is aningenious shortcut:
Since any point of afalling object has thesame velocity when
it hits you, you can
describe the different
energies transferred
to you by assigningan effective mass tothe sword that
depends on position
along its length.
Turner calls theeffective mass
"apparent inertia"
or "apparent mass"of the sword, which
is fine too. I'll use theterm "effective mass"
because that issomething physicists
are used to, it comesup, for example, insemiconductor
physics all the time
In the experimentwith a uniform rod
discussed above, we
can deduce without
any calculations thatthe effective mass
must be equal to thereal mass at theposition of the centerof mass, right in thecenter of the rod, andthen it must
decrease somehow
towards both ends.
That is exactly what
it does if you run
through thecalculations: Here iswhat we get for a 0.3
kg sword:

Science Link
Effective
Mass

Effective mass distribution
What we also get is that the only necessary parameter of the object in question that we need to know is its moment ofinertia relative to its center of mass (COM). That is rather amazing and allows many insights into the optimization of realswords, as we shall see.
I use the term "optimization" because we want to optimize as opposed to maximize properties. That involves going forcompromises since measures that might be good for one property will turn out to be bad for another one. With theeffective mass we have yet another key parameter - sort of a mixture of the mass and the moment of inertia - that will
not only prove quite helpful but is essentialfor understanding what follows.
Iron, Steel and Swords script - Page 668

Applications of the Effective Mass Concept
First let's look at what happens of we change the moment of inertia of our rod from above without changing its weight.
We might do that by putting a sphere containing most of the weight in the middle (while making the rod thinner to keep
the mass constant) or two half-spheres at the ends as shown below. The first measure decrease the moment of inertia
quite a bit, the second measure increases it.

Effective mass of three rods with the same mass
(0.3 kg) but different mass distributions (asschematically indicated) and thus moments ofinertia I
The effective mass curve responds simply by constricting or widening as shown for a rod weighing 0.3 kg. What you
would feel in the Damocles sword experiment is also quite clear. The impact with the COM hitting your head isunchanged. It hurts the same for all three rods. Getting hit by the end of the rod is different, however. Far less painwith the low-I rod. far more with the high-I rod.
Next we look at the effective mass curve of a real sword and an axe. We get something like this:Effective mass of sword and axe
The curves, by the way, are not actually calculated for the weapons shown but just give the idea qualitatively. What you
perceive for sure is that you rather have the business end of a sword fall on you than the business end of axe. Its
effective mass at this point is much higher than that of the sword and thus also the energy transmitted to your head.
Well - the sword is preferable to the axe only as long as both objects fall and thus hit you with the same velocity. If
somebody swings these weapons, chances are that he can swing the sword much faster than the axe, so it hits
you at higher velocity. And the energy, remember, goes with the mass and the square of the velocity! There is areason why you might prefer your axe whenever you have all the time in the world to get it up to speed but go foryour far more agile sword if there is high-speed fighting.
What you want is an appreciable effective mass at the tip of your sword so its hits will be felt but without compromisingon all the other points like manageable total mass, small moment of inertia for agility, and a percussion point (plus theimportant vibration nodes) at the right place.
And now you start to see the magnitude of the problem we are facing when we want to optimize a sword.

Iron, Steel and Swords script - Page 669

12.4.2 Dynamic Properties Combined
Graphics to Show it All
First let's go through the basic parameters that determine your swords dynamical properties:
1. Its mass m. This is a single number, easy to obtain and typically between 1 kg - 2 kg. Mass is a clear thing that
does not need more words.
2. The center of mass. (COM). Once more a single number that gives the distance (in cm or mm) to somereference point. It is also a sufficiently clear entity by now. Typically we want it on the blade but not too far fromthe hilt.
3. The moment of inertiea I. This is a measure of the distribution of the mass. It is not a single unambiguous
number and it is not all that easy to calculate. Its value (given in kgm2) is always relative to a rotation axis. It is
usually given with respect to a rotation axis through the COM at right angles to the blade and then designated
ICOM. If ICOM is known, it is then easy to calculate values for other axes perpendicular to the blade at somearbitrary distance from the COM.
Generally we want a small moment of inertia since this makes it easier to swing the sword.
4. The effecive mass. This is not a number but a curve with a shape that is determined by the mass and themoment of inertia of the sword. It gives values (in kg) that decrease from a maximum at the COM (with a value
equal to the total mass) to lower values at both ends of the sword.
The value of the effective mass at some point relates to the impact felt at that point.
5. Percussion points. There are always two points! One point is usually chosen as the pivot point on the hilt close
to the cross guard. The corresponding percussion point then is somewhere down on the blade (or even outside;
off the tip). Its distance from the center of mass depends on the mass m, the moment of inertia ICOM relative to
the COM, and the distance of the pivot point from the COM. We want the percussion point to be found in the tip
region because hits on the percussion point do not transmit forces to the hand at the pivot point.
6. Vibration node points. Typically swordsmen are concerned about the location of the two nodes of the (lowfrequency) second order side-to-side vibrations. They are easy to excite and to see. The two nodes of the (highfrequency) second order edge-to-edge vibration might be more important, however. Luckily, they coincide more orless with the first variant. Ideally, we want the lower vibration node to coincide with the percussion point.
Vibration node positions are not easily calculated. It is also not easy to change their position substantially. They
tend to be - very roughly - around the hilt and about 3/4 down the blade.
7. Point of maximum impact. I have not discussed that yet but it is clear that whenever you hit something you
transfer some energy from your sword to the hittee. There must be a point somewhere on the blade that delivers
the most energy and that is the point of maximum impact. I'll discuss that later in detail.
In essence, all these parameters result from the distribution of the materials defining your sword. In other words: It is
the shape or geometry that counts - and details matter! Change something there and all the parameters above willchange. Some more than others.
What that means is simple. You cannot sit down, consider what you want with respect to the parameters given above,
make a list with the resulting numbers and curves, and order your sword maker to produce a sword that meets yourwishes. All these parameters are simply not independent.
You must compromise. There is no "ideal" sword for you, only compromises. Swords may give you satisfaction withregard to some parameters while leaving something to be desired with respect to others.
Peter Johnsson has come up with a very attractive way to illustrate the sword properties that result from Vincen Le
Chevalier calculations 1). His pictures are mostly published in "The Sword - Form and Thought" 2) and I use some ofthem here with the kind permission of Peter, Vincent and the Solingen museum.
Here is what it looks like with some explanations added by me:

Sword dynamics graphicallyIron, Steel and Swords script - Page 670

The text insets are from me and I used my nomenclature that on occasion is somewhat different from that of Le
Chevalier. Pictures like that are generated by a computer program that is available for everybody in the Net 1). You must
supply the basic data, of course, and that involves some precise measurements. Le Chevalier has explained most of themath behind the calculations and, as far as I'm concerned, it is sound.
There is a lot of information in these pictures. Let me go through the pertinent points:
1. You see the basic shape of the sword in some detail and you find the mass.
2. The effective mass curve is shown below the sword and the effective mass at some special points may be given
as a number and in percent of the full mass.
3. The center of mass is indicated.
4. Two pivot points are chosen, always close to the cross guard or to the pommel. The corresponding percussion
points on the blade are calculated and shown. Since the real pivot point will be somewhere between the two
shown, the blade part between the two percussion points is where you want to hit (with some preference to thefront one).
5. The two nodes of the second order side-to-side vibration are shown.
6. The sword's response to attempts at translations are shown as an oval centered at the cross guard pivot point.
The smaller the distance from the pivot point to somewhere on the oval, the harder it is to move the sword in that
direction.
For straight thrusts the full mass is used, for movements at 90o to the blade the (reciprocal) effective mass in that
direction is used. For movements in arbitrary directions, a suitable mixture of the two values is employed.
Assumed is that you just apply a force in the specific direction which, except for the straight thrust, always
results in translation plus some small rotation.
7. The sword's response to attempts at rotations are shown as two cones centered at the cross guard pivot point.
The larger the cone, the easier it is to rotate the sword around the cross guard pivot point. The essential
parameter for this is the moment of inertia for rotations around the pivot point.
8. Some more information, e.g.. effective masses at some special points, might be given as the need arises.
The power of these diagrams (from the Solingen book) becomes clear when you use them to compare swords.
The sword on top is
described as a handand-a half Sword
from 1480 - 1500. It
is 105 cm long with athe blade length of
81.5 cm and weighs
only 0.822 kg
The sword on thebottom is actually an"Ulfberht" sword. Its
length is 83.3 cm,
with a 70.2 cm
blade. It weighs in at
0.79 kg, quite low
too.
The "Solingen
Swords" Link
provides a lot of
pictures like theones discussed here
plus some data. It
includes very lightand very heavy
swords, long andshort ones, andallows a lot of data
extractions like theone below.
Here are the two
characteristics ofthese swords:

Illustr. Link
"Solingen"
SwordsIron, Steel and Swords script - Page 671

Property comparison of a hand-and-a half Sword
from 1480 - 1500 and a Ulfberht sword from ca.
1000 AD.
The Ulfberht has a slightly better translational response, simply reflecting its slightly smaller weight. Its lower percussion
point coincides with the vibration node but is a bit far from the tip. The effective mass at the node point is respectable
but practically the same as that of the longer sword. The long sword has a far better rotation response. That means thatyou can get it to swing with a larger rotational speed than the Ulfberht. Its percussion point (also close to the node point)
thus moves considerably faster that that one of the Ulberht and thus delivers far more punch (the power goes witheffective mass and the speed squared!). It is just a much better sword - if wielded by an expert. It needs more room forswinging and that needs practice.
I doubt very much that the longer sword was intended for "one-and-a-half" hands. There is actually ample space fortwo hands on the hilt but given its small mass I tend to believe that it is meant for one hand only. Why then the longhilt? The answer is simple:

Optimizing the dynamical properties ofyour sword means optimizing:
the pommel and thethe blade taper
The long sword obtains its superior properties to a large extent because its pommel is far away from the center ofmass without taking too much mass away from the blade. The blade is actually thicker then the Ulfberht blade but
more slender and cunningly tapered. There are many interesting pictures of people (including angels) wielding thoseswords always with just one hand, here is the link.
Finding the best pommel mass and distance plus a fitting taper Is not easy because of all the parameterinterdependence. There are no simple rules. I'll give you a few examples of what can be done.

Iron, Steel and Swords script - Page 672

Optimizing Pommel and Taper
I'll show you two pictures, one from the "Solingen book" and le Chevalier's / Johnsson's work, the other one from Turner's
seminal contribution.

What a optimized pommel can do
Unfortunately, the basic data of the sword are not given but it is quite obvious that an optimized pommel will:
Add some mass, making the sword heavier and thus a bit less agile.
Move the center of mass much closer to the hilt, substantially increasing agility,
Move the vibration node close to the hilt "up" quite a bit into the hilt. This substantially reduces the vibration
amplitudes your hand will feel.
The vibration point close to the blade tip only move a little bit "up" on the blade. You actually would like it to be
farther out and closer to the tip but there is no way to achieve this with a pommel. So be happx that it only moves
a little bit in the wrong direction.
The percussion points move quite a bit down on the blade. That is good. Having a percussion point coincide withthe vibration node might be even better but for those kind of long swords this is not practical. Anyway,
considering that for a pivot point around the vibration node of the hilt, the percussions point will not be too far fromthe blade node, this is quite acceptable.
We have a first quite instructive example for what can be done, and that you always must compromise.
Turner looks a the effect of pommel from many directions (read his book if you want details). What I will show you fromhis work is what a pommel will do to the effective mass: The pivot point here is assumed to be somewhere between yourwrist and your elbow but that doesn't matter much.

Iron, Steel and Swords script - Page 673

Adding various pommels to a 1 kg blade andtheir effect on the effective mass

You see the increase in mass and the shift of the center of mass towards the hilt. You also see a large increase of theeffective mass around your hand position (around 0.3. m) that will decrease the translational response (you more or lessfeel the full increase in weight there). The rotational response, , however, is far less impaired because the COM getscloser to the hilt.
What you probably don't see is the 30 % increase in the effective mass at the tip of the blade for the 0.5 kg pommel!
It is there, believe me, you just need to "enlarge" the tip region in a (precise) drawing to see it. In other words: Increasing
the weight of your sword by 50 % by a substantial pommel will not impair maneuverability very much (far less then 50%) while giving you 30 % more "punch" for hits close to the tip region. That might well be worth the effort.
We see once more the importance of optimizing the pommel or better yet, pommel and the rest of the hilt.
Far more could be said about pommel and hilt, followed by lengthy discussions of blade design (length, width,
thickness, taper on thickness and width, number and length of fullers, cross-sectional geometry, ....) but I will havemercy on you (and me). I will just five your the results of extracting some data from the wonderful work in the "Solingenbook".

Relation between the length of a sword and its
rotational response
Large size version

What I did was to measure the angle of what I have called the "rotational response" in the drawing above. Then I plotted
the length of the sword versus this angle; the result is shown above.
I did the same thing for the relation between the "rotational response" and the mass, the result is shown here.

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When I started this I had no idea of what I would get. What we see is very little correlation. For any given angle or
length you care to select, there is wide range of length or angle values, respectively. The same is true for mass andangle values. What that tells us is
The "bandwidth" for optimizing your blade is rather large. You can obtain high agility for any reasoable length(or mass) if that's what you want.
You will have to pay a prize, however. If you go for extremes, some other properties will also get extremes. A
great rotational response will always cost you impact power because your effective mass near the tip goes
down (and vice verse), for example.
Summarizing in a somewhat superficial fashion, let me say this:One certainly can produce swords that have good masses, are well put together, employ good steel and otherfine materials, and looks good - but they are definitely lousy swords. Just look at their "dynamical behavior
diagram " and you shall see.
Turner claims that quite a few replica swords out there are lousy in this respect (with percussion points in front of
the tip, for example). I see no reason not to believe him but I cannot supply objective prove.
One certainly cannot produce "the" superior sword. Any good sword is a compromise, emphasizing someproperties at costs to others. Which compromise is best for you, depends on you. There is no "one sizes fits all".

1)

Vincent Le Chevalier; selected papers, all accessible via his home page or directly if links are given below:
1. "A dynamic method for weighing swords" November 15, 2014.
The title is a perhaps a bit unfortunate because the article describes much more than "weighing" your sword. In
essence, it discusses the important parameters of a sword, how to obtain them experimentally, and how they
connect mathematically (lots of equations in the appendix). It also introduces the "two masses on a stick" model
for simulating dynamics. It helps you to find the parameters of your sword that you need to supply for the:2. On-Line weapons dynamics computer. You have to find it in the Net, the link may help.
3. Modelling impacts and damage. The article does exactly what the title says. If does so with equations on just a
few pages.
4. Simulating Sword Properties. Explaining how the simulation program works and in particular some information
about vibration modes computation.

2)"Das Schwert - Gestalt und Gedanke ("The Sword - Form and Thought"). Hrg.: Barbara Grotkamp-Schepers et al. The
book to a special exhibition at the "Deutsches Klingenmuseum Solingen", Sept. 2015 - Feb. 2016.

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12.4.3 Hitting Something

We are finally ready to hit something with our sword. But before I teach you the physics of hitting, I must remind you ofa simple truth from long begone days, back in chapter 2.1:

Swords are evil objects if you consider only
their intended or actual use as weapons.

Nothing has changed. There is no reason to hit other living beings with the sharp edge of your sword. Forget it. You
are not the chosen one who has to redeem this or that, nor are you the special hero who in his spare time rescues
those maidens in distress. Dragons count as endangered wildlife and are heavily protected anyway.
There are, however, good reasons for hitting balls with tennis rackets, golf clubs, baseball bats and so on. There are
equally good reasons to whack at each other in simulated sword fights with practice swords. Mankind needs to play
and that includes swordplay for fun. Keep that in mind when you read what follows.
When your sword hits something it will do so at some point on the blade, let's call that the impact point. Of course, in
principle you could hit a planar target with a length of the blade and not just with a point but that would not be a good
strike. Curved blades are curved after all, to make initial contact with the target on a point.
Equally of course you may not hit a point on the target with a point on your blade but deliver a thrust with the tip of yourblade. I'm not going into that because the physics of stabbing is rather simple. You stab a target much softer than yourblade and you penetrate it, or you stab a target about as hard or harder than your blade and you brake your blade (andpossibly your wrist).
As far as hitting is concerned, we need to look at the physics of collisions or impacts . This part of mechanics isgoverned by the conservation law of (linear and angular) momentum plus the conservation law of energy. It is not allthat complicated but a certain amount of math does come into play. The kind of collision that relates to sword
strokes will require the solving of 11 equations with 11 unknowns, for example. I'll do that in special module, here wewill start with what we already know without solving equations.
The somewhat idealized situation we are going to look at is shown below. We swing our sword as shown, with anapparent center of rotation somewhere around the elbow. It is roughly what that Samurai is doing at that point in time
when his katana is about horizontal. The sword (plus parts of you) rotates with some angular velocity expressed by its
circular frequency ω that gives the impact point a linear velocity v. The target is something with some mass m T, an
arbitrary shape in reality but a circle in the picture for ease of drawing. The target is also mobile. Not only can it be
moved, it might even have some initial speed of its own (not shown in the drawing). Think of a tennis ball flying towards
you, for example. The target also has some properties that will come into play later.

How we look at hitting something

Now let's recapitulate the things you definitely know, even if you are more mathematically challenged than the averagebanker or USA president. You know what you want to do with some target. It should look like this:Iron, Steel and Swords script - Page 676

Producing "good" target damage

You want to run your sword right through the target, neatly cleaving it in two parts. Your sword keeps moving but
with reduced speed. Alternatively, you cut the target partially and your sword comes to a stop inside the target.
Whatever happens in detail, you know that all or parts of the initial kinetic energy of your sword was used for
creating damage since it takes energy to fracture or deform some material.
If the target is not some "body" but another sword because you need to deflect a blow of your opponent, you consider
this situation:

A fully elastic collisionYour blades meet (flat side to flat side, hopefully) deform somewhat on impact, and then "bounce off" to someextent, reversing their velocity directions. You sure hope that your sword comes out undamaged of this encounterand this means that its deformation upon impact needs to be fully elastic ! Same for the sword of your opponent.
Now we have our first key topic: fully elastic collisions! If your physics teacher ever pestered you with collisions, it will
have been this type. It is fairly easy to deal with - look up the science link to this topic to refresh your memory. The
important insight to memorize is

Fully elastic collisions will not damage
your sword. Nor anything else

Let's move on. There is another thing you know for sure. It is shown below:

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Damaging your sword

The target is heavy and hard. A big rock or an anvil, for example. If you don't own Siegfried's magical sword Notung,you are not going to do much damage to the target but you will heavily damage or fracture your sword (and possibly
your wrist). It is not an elastic collision because there is damage albeit to the wrong object.
Nothing helps. If we want to optimize damage to the target, we must look at what is called an inelastic collision. The
way to do that is to look first at fully inelastic collisions, the opposite of fully elastic collisions. But that would leavetarget and sword damaged, so in the end we need to look at the mixed case somewhere in between the extremes.
Below I show you what would happen for the classical fully inelastic collision in our scenario:

Fully inelastic collision with damage to bothobjects

During the collision both target and sword are inelastically, i.e. permanently deformed, then stick together and move
together with some common velocity that depends on the "starting" conditions, i.e. the two masses and respective
velocities.
just to be on the safe side, I'll give you the two extremes - fully ellastic or inelastic collision - once more for a different
kind of scenario:

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The two extremes of collisions: fully elastic andfully inelastic

We are interested in the in-between case. The target should behave inelastically, allowing some damage, while ourblade should behave fully elastically, not suffering any damage.
Nothing helps but
going through thephysics of that. It is
actually not all thatdifficult. The
conservation lawsfor (linear andangular)momentum andenergy is prettymuch all one
needs. Linear
momentum is linear
speed times mass,angular momentum
is angular velocity
times moment ofinertia. As far as
energy isconcerned, we only
need to consider
the kinetic energy,
the energy
contained inmovements. It
scales with massor moment ofinertia times therespective speeds
squared. If weassume forsimplicity a target
at rest, the thing to
do is:

Science Link
Collisions

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Calculate the starting kinetic energy Ekin, start that is contained in your sword stroke.
Calculate the final velocities (both linear and angular) of sword and target after the collision.
Calculate the final kinetic energy Ekin, final going with these final velocities
Calculate the difference of final and stating kinetic energy, Ekin, final – Ekin, start. That must be the energythat did damage since the total energy is conserved.
You can look up how that is done in the science module. It is quite illuminating and not all that difficult (no morethan 11 equations for 11 unknowns).
The outcome is as expected.
For fully elastic collisions the total kinetic energy before and after impact is the same. Sword and target
move with some velocity. There is no energy left for damage to the target.
Fully inelastic collisions provide for maximum damage energy to the target (and the sword). The damage
energy delivered to the target, however, is always smaller than the total energy invested into the collision.
"In between" collision provide some damage energy to the target but always less than fully inelastic
collisions.
That can best be described by invoking an "energy transfer efficiency"; a number between 0 and 1. A value of 1
would mean 100 % energy transfer, zero would mean 0 % energy transfer, and something in between, like 0,56,
denotes a transfer with 56 % efficiency, i.e. at most 56 % of the initial energy is used to cause damage to thetarget.
Before I go into details, we must come clear about one major point. The kinetic energy in your sword stroke has to dowith the speed of your blade and the mass of your sword. The way I have drawn the situation, the sword has someangular speed (measured by its circular frequency ω or in rpm if you like that better). But at the point of impact we needto know the linear velocity v (symbolized by the red arrow in many of the pictures above) and not the angular velocity.
And that speed is different for different points on the blade. The tip moves much faster than a point close to the hilt, forexample. No big puzzle here: the speed v at some point at a distance d from the apparent center of rotation is justdistance times circular frequency. You should be able to figure that out by yourself, otherwise use this link.
Moreover, you are not hitting the target with the full mass of your sword as long as the impact point is not at the centerof mass. This needs to be taken into account. And we have already covered that, look at this picture again. It is theeffective mass at the impact point that counts!
So in order to translate the "sword impacting a target collision scenario" from above to the standard "moving(spherical) object hits another moving (spherical) object" scenario, we have to "translate" as shown in the picture
below"Sword hits target" scenario and how it isconverted into "object hits object" scenario

For maximum impact or damage we obviously need two ingredients:
1. A large starting energy, translating into finding the best combination of effective mass and speed. That implies
finding the best point on the blade to hit with.
2. A high energy transfer efficiency. That will certainly depend on target properties and possibly other parameters.
We shall look at that in the next - and last! - subchapter.

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12.4.4 Impact
Energy Transfer
Below is the picture from the preceding subchapter once more. We are now considering the impact of your blade on atarget with some properties:
It has a mass m T . That might be simply its real mass. Then it might be the mass of the target plus the mass ofwhatever it is in close contact with. In case the target is your opponent sword, it is its effective mass at the pointof impact.
The target may have a speed on its own as shown in the picture. This speed might be zero on occasion but eventhen we might assume that the target can be moved; at least the part that you slice off. We do not hit big rocks,
anvils, or other immoveable objects any more.
The target might be rather hard (like your opponents sword) or rather soft. We already know that we can only
damage targets that behave inelastically, meaning that they must be appreciably softer than your blade.
.

"Sword hits target" scenario and how it isconverted into
"object hits object" scenario
We know that he damage inflicted on the target scales with
The energy contained in the blow.
The energy transfer efficiency.
Let me start with considering the last quantity first.

First of all, there is no such thing as an energy transfer efficiency in the literature about hitting things with sticks. I havemade up that term. In serious collision science we would call it damage efficiency and that is indeed the term I usedin the collision science module. It is easier, however, to discuss energy transfer efficiency, in particular if one is notallowed to use equations.
It is sufficient to look at simple collisions of two bodies as shown in the right hand corner above to get useful results. We
assume "in-between" collisions, not 100 % inelastic but at least with a high percentage of inelasticity.
Here is what we will find for the energy transfer efficiency. First, it is a product of two components. The first one
describes the degree of inelasticity of the collision, the second one the relation between the (effective) masses of sword
and target.
What do we know about these quantities?

1 The inelasticity related energy transfer efficiency increases quickly with increasing degree of inelasticity of the target2). For a collision with only 20 % inelasticity, we still get 36 % transfer efficiency, for 30 %, 50 % or 70 %inelasticity, we get energy transfers of 61 %, 75 % and 91 %, respectively.

2 The mass related energy transfer efficiency increases with increasing target mass and decreasing effective blade
mass. A few examples are shown in the table below

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Mass relation Target : blade

Transfer efficiency

10 : 1

91 %

5: 1

83 %

2:1

67 %

1:1

50 %

1:2

33 %

1:5

17 %

1 : 109%That is a bit strange. Since I can't control the mass of the target, my best bet would be to use an extremely lightweight blade? Well, yes and no! For a given target mass the energy transfer efficiency for a light sword is larger thanfor a heavier one, indeed. But don't forget, we are talking transfer of energy here. With a very light blade you will
indeed transfer more of the initial energy - there just isn't much energy to start with!
If you and your buddy buy a lottery ticket that wins 100 $, your cash transfer coefficient is 50 % and you are left
with 50 $. If you and your remaining 99 buddies from your sword club buy a lottery ticket that wins 1.000.000 $, yourcash transfer coefficient is only 1 % but you are left with 10.000 $.
Nevertheless, we can draw a few conclusions from the general rule, and I will just repeat what I have already pointed out
in the collision science module.

1 You can't damage very small masses with your sword! The efficiency is essentially zero. In other words: Don't goafter that mosquito with your katana. You might be able to move it around quite a bit but you cannot damage it. This
joke 1) is thus quite funny but physically unsound. Wait until the mosquito sits down on a wall (moving up the target
mass to near infinity; mosquito + wall + earth) before you hit it. And this applies to fly swatters as well as toswords.

2 Forging should be done on an heavy anvil. It is the total weigh of the anvil and the material to be forged that counts.
You want to deform your iron, i.e. damage it. Use a not too heavy hammer and hit with speed.
Same thing for chopping wood with an axe.

3 Drive that nail into the wood with a relatively heavy hammer. You don't want to damage the nail, you just want to giveit speed so it can damage the wood.

4 Guns work. The projectile is very light and will thus inflict damage on anything still lightweight yet much heavier thanthe projectile. The projectile is very light but extremely fast (up to 1000 m/s) and thus contains a lot of energy
despite its tiny mass, and that leads to severe damage.

5 Light swords do not work for the reasons considered above. They will transfer their energy very efficiently toeverything substantially heavier, but there is not much energy to transfer. Modern guns have muzzle speeds of morethan 1.000 m/s and that gives even a light weight bullet plenty of energy. You can't get close to that speed with yoursword ( 50 m/s tip velocity is already as high as it will get). And remember that speed counts quadratically.
Putting things together we have, for example a mass related transfer efficiency of 0.91 or 91 %, and an inelasticity
related transfer efficiency of 0.75 or 75 %. That gives us a total transfer effciency of 0.91 · 0.75 = 0.68 or 68 %.
In other words: you will not easily get close to 100 %!
But relax. The simple collision theory employed does not account for a lot of things. First, your sword doesn't do all
the fighting by itself but with you attached. That changes masses and might increase the efficiency if you use yourbody mass wisely.
Second, whenever your sword gets "stuck" in a partially cut target, your transfer efficiency will be close to 100 %.
You can only get stuck in a heavy body, and in this case it is an almost fully inelastic collision even so your blade
gets not damaged.
Blade Energy
The stating point here is the simple truth that the energy of that part of your blade that impacts the target is given by
one-half of the effective mass at that point times the square of that point's velocity. The big question now is:

Which point on the blade has thehighest energy?

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This is a rather tricky situation for two reasons:
1. The answer is not obvious.
If I move out towards the tip, the velocity increases but the effective mass decreases. Where does the
product of effective mass times velocity squared peak?
2. We want to hit the target with that point, obviously. But we already have two other points we want to hit thetarget with: the percussion point and the vibration node point. Can we get these three points to coincide?
I don't know the answer to the last questions but I tend to believe that is is either not possible or only with severe
sacrifices to other properties. Let's see why by looking at Turner's calculations for the blade energy as a function of the
impact point position.
What we need to do is to select some sword with a known effective mass curve and move it. We could just rotate itwith some circular frequency ω around its center of mass (COM) or we move it in whatever way and describe that bea rotation with ω around an apparent center of rotation. A point at position x on the blade then moves with a velocity
that is simply given by ω times the distance of the point to the rotation center.
Take the equations for the effective mass and multiply it with the equations for the velocity squared and you have(twice) the kinetic energy at the point x considered. The picture below shows schematically the two curves thatneed to be multiplied. Note in particular that the velocity squared curves are different for different center of rotations.

Effective mass and velocity squared curves

Spelling out the equations doesn't help much because you (and even I) will not just "see" what the resulting curves will
look like. Nothing helps but to wind up your computer and getting it to work. George L. Turner has done just that so I
can use his results. Here is an example:

Effective mass, velocity and total kinetic energy
curvesTurner doesn't supply the full set of sword data so the sword inset is from me. We can deduce the apparent centerof rotation because it must be at the point where the velocity is zero.

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What we can see is:
The position of maximum kinetic blade energy is certainly not at "the" percussion point, the one we typicallydefine with respect to a pivot point close to the hilt. This particular percussion point is not indicated for this sword
but would be much farther down the blade for sure.
The position of maximum kinetic blade energy would certainly change for different center of rotations (the orange
velocity curve would move to the left or right) . It thus cannot be at one fixed point anyway.
The position of maximum kinetic blade energy is actually located at the percussion point related to the apparent
center of rotation. That is a result from Turner's book. It is, however, based on somewhat unclear math.
The position of maximum kinetic blade energy is certainly not at the position of the vibration node which is notindicated for this sword but would be much farther down the blade for sure.
The kinetic blade energy decreases from its maximum point when you go towards the tip of the blade but
considerable less so than the effective mass.
Even so the tip has the highest velocity, it does not carry the highest energy.
All things considered, having the maximum energy point not coinciding with "the" percussion point and the vibration
node is not so bad. In "modern" sword fights, real ones or for sports, your opponent is not heavily armored any
more. If you can score a hit, it would be bad for him, even if the energy delivered is not the maximum. For thrusts
the whole discussion is moot anyway. Now consider that most of your moves actually do not touch your opponent
because he is deflecting your move with his sword. Half of the time you deflect his moves and that you do not withthe tip area but farther down the blade - closer to where you can invest maximum energy.
What I'm saying is: Don't just look at strokes that actually damage something. Most of the time this is not what you
do!
Putting Everything Together
I just told you not to focus too much on the damage energy questions. But that is exactly what I'm going to do now, justto finish this topic.
It only remains to combine the energy transfer efficiency with the blade energy. You can do that yourself following thequalitative rules given above or you could run through the math once more. Or you take it straight again form Turner's
work as I'm going to do.
Tue next picture shows it all

Hitting a heavy target(KE = kinetic energy)
Source: George L. Turner

We hit an inelastic 10 kg heavy target (that can move) with a sword as shown above. You see that the maximum
amount of damage energy (light blue area) is delivered about 15 cm down the blade from the center of mass, i.e.
closer to the hilt than to the tip. The target is damaged by about 125 J from the total 140 J present, a 90 % all-overefficiency. If you hit with the tip (around 85 cm distance) you still deliver a little less than 100 J or about 70 %. The
rest of the energy is mostly in the sword translational movement (dark blue area). The target only gets moved a little
bit (yellow area).
Next we look at the same general situation but with much lighter targets:

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Hitting light-weight targets(KE = kinetic energy)
Source: George L. Turner

Now you deliver maximum damage energy with the tip area. In the 0,5 kg target case it is about constant for thewhole tip region. However, your maximum efficiency is down to about 55 % (0,5 kg targer) or 35 % (0,145 kg target;
something like a baseball). A lot of energy remains in the translational movement of the sword and also in therotational movement. The target gets up to about 15 % of the energy just for movement, too.

The End

The End ?????

No way. This can't be the end. I can't possibly finish a hyperscript with around 480 modules and 2900 pictures bywhacking you on the noggin with a sword. So read on.

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1)

Once the Shogun gave a reception to honor the best swordsmen in Japan. All the top samurai were in attendance alongwith Court nobles and beautiful geisha. A geisha approached the third highest ranked swordsmen and asked; "Sir, canyou demonstrate your sword skills for me?" At once, the samurai drew his sword and cut a hovering fly in half. "Veryimpressive", said the geisha. When she saw the samurai who was the second highest ranked swordsmen in Japan she
asked him the same question. He immediately drew his sword and with two quick strokes quartered a fly. "Mostimpressive", said the geisha. Then she spotted the samurai that was the highest ranked swordsmen in all of Japan.
"Honorable Sir", she said "would you be so kind as to demonstrate your sword skill for me?". The samurai drew his sword
and cut into the air in the direction of a nearby fly, but the fly buzzed away. "Oh, so sorry you missed", said the geisha.
"But I didn't miss", said the samurai humbly "that male fly will no longer be able to have offspring."

2)

Using the so-called coefficient of restitution e, a number between 1 (fully elastic) and 0 (fully inelastic), that part of theenergy transfer efficieny is given by 1 – e2.

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12.4.5 The End
This Hyperscript was actually about the Materials Science of iron and steel. I then took that as the guiding line to thehistory of iron and steel. Swords were just employed to make it more interesting. The serves as the paradigm for ironand steel.
I made a lot of excursions into neighboring areas like the history of metals in general, the forging of specials swords, orthe physics of hitting things with sticks.
There are 474 modules (+ 9 hidden ones) and around 2900 pictures in this Hyperscript and I just can't finish it withteaching you how to inflict maximum damage on whatever target you hit with your sword.
So what should I chose to end this enterprise with? By giving you some peaceful advice:

Finally Read That Preface(or send me some money)

Reading that will send you to sleep and you can't get more peaceful than that. Alternatively you could finally do thatbeer experiment.

Cheers!

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