CERTAIN IMPROVE- MENTS IN THE PRODUCTION AND MANUFACTURE OF IRON AND OF STEEL
Year: 1849

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, J, Sir FRANCIS
CHARLES KNOWLES, of Lovell, in the County of Berks, Baronet, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Fourth day of July,
One thousand eight hundred and forty-nine, in the thirteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Francis Charles Knowles, my exors, admors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said Francis Charles
Knowles, my exors, adiňors, and assigns, and such others as I, the said Francis
Charles Knowles, my exors, adñors, or assigns, should at any time agree with,
and no others, from time to time and at all times during the term of years
therein expressed, should and lawfully might make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, and in the
Islands of Guernsey, Jersey, Alderney, Sark, and Man, and in all Her said
Majesty's Colonies and Plantations abroad, my Invention of "CERTAIN IMPROVE-
MENTS IN THE PRODUCTION AND MANUFACTURE OF IRON AND OF STEEL;" in which
said Letters Patent is contained a proviso, that I, the said Francis Charles
Knowles, should cause a particular description of the nature of my said Inven-
tion, and in what manner the same is to be performed, by an instrument in

page_text: writing under my hand and seal, to be inrolled in Her said Majesty's High
Court of Chancery within six calendar months next and immediately after the
date of the said in part recited Letters Patent, as in and by the same,
reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Francis Charles Knowles, hereby declare that the nature of the said Invention,
and in what manner the same is to be performed, are fully described and
ascertained in and-by the present Specification thereof, reference being had to
the Drawings hereunto annexed (that is to say) :-
--
The nature or object of my said Invention is fourfold, videlicit :-
First, the making of malleable iron from iron ores by a direct process without
any previous smelting of the same.
Second, the making of steel directly from iron ores.
Third, the preparing of iron ores by cementation thereof in retorts or kilns
separate from the blast furnace, in order to the making of cast iron from the
same, by smelting them thereafter in furnaces, as usual.
And, fourth, the substitution of certain iron ores, herein-after described, to be
used as a flux to other ores in the making of cast iron, and as a substitute for
the limestone flux. at present employed therein.
: And the manner in which I carry my said Invention into effect is as
follows: For the first two of the above objects or purposes I select such iron
ores as are the most free from earthy matter in their composition, and as
approach most nearly to pure oxides of iron, the more nearly the better. For
the third object or purpose I use all iron ores indifferently, excepting only such
as contain much sulphur or arsenic, that is to say, all such iron ores as are at
present used in the making of cast iron. The ores must be first broken into
pieces of moderate size, so as that when placed together in a heap there may
be interstices between them capable of admitting the passage of a gas or vapour
through the heap or mass without any great obstruction thereto. Further, if
the ores contain any volatile or gaseous matter other than oxygen in their
composition, or if they contain water in combination as hydrates, they must be
roasted by some one or more of the methods now in use in order to expel the
same. I then treat as follows the ores which have been so prepared :-I place
them in retorts rendered as air-tight and gas-tight as may be, and I raise the
said retorts to about a red heat, or more by means of fuel burning around them
in furnaces or kilns, into which the said retorts are properly set for that
purpose. Each of the said retorts (of which I employ a series, according to
the quantity of the ores to be cemented, as herein-after described,) is to be
connected with gas pipes furnished with stop-cocks in such a manner as that

page_text: a current of either of the gases or of the vapour, to be herein-after mentioned,
may be passed through the said retorts and their contents, or cut off at will, as
occasion may require. The form of the said retorts may be cylindrical, as
represented in the Drawing.
Figure 1 is a front elevation of a set of retorts; Figure 2 is a horizontal
section taken on the line a, b, of Figure 1, in which the arrows denote the
direction of the current of gas or vapour; and S, s, are the stop-cocks at
the entrance of the gas or vapour into the retorts, and its exit therefrom
respectively.
Each retort is to be provided with a small gas jet in its interior, for the
purpose of preventing any explosion before the retort is cleared of the atmo-
spheric air contained in it, after it is charged with the iron ores and closed;
and such explosion is prevented by lighting the said jet of gas and allowing..it
to burn for a short time after the retort is so charged and closed, whereby the
oxygen necessary to such explosion is consumed; this done, the jet is to be
extinguished by the stop-cock S outside the retort. During these preparations
the fire must be kept down by a damper connected with the gas pipes of
entrance, and exit S, P, s, p, as aforesaid. There are to be gas mains M, M,
and m; m, communicating with gasometers, such as are now in use in ordinary
gas works, that is to say, a main; M, M, with the gasometer or gasometers
which supply the gas before it passes through the retorts and is submitted to
the action of the heated iron ores, and the main m, m, which receives the gas
in its altered state after such passage and such action. I do not claim any
particular, form or construction of apparatus for the purpose of cementing the
ores of iron by submitting the same to the action of the gases or vapour, as
hérein-after more particularly described, but I merely give the above as what
appears to be a good and convenient form or construction for the
purpose. The
retorts also may be made of cast iron or even of fire clay, if they be made so as
not to be liable to crack, and if the gas or other fittings be carefully adapted
thereto, so that the whole inay, be thoroughly air-tight and gas-tiglit. Care
must also be taken to apply the heat to the retorts as uniformly around-them
as possible, so as not to produce unequal expansion, whereby they would
become liable to crack. It will accelerate the process of cementation if the
gas after leaving, the gasometer (or the vapour) be passed through an ordinary
liot blast apparatus, so that it may enter the retorts in a heated state. For the
purpose of cementing the iron ores by the above or some similar and convenient
apparatus, I make use of two sorts of gas, namely, coal gas, such as is now
used for lighting-streets and houses, the same being first purified by the known
methods in usc. from sulphur or other impurity, and carbonic oxide gas, prepared

page_text: -by-slow combustion from charcoal, coke, anthracite, or stone coal, peat, or other-
carbonaceous matter, or otherwise; I do not, however, confine myself to these
two sorts, of gas alone, for the vapour of coal oil or naphtha, of petroleum, of
camphine, or of any other hydrocarbon sufficiently abundant and cheap, may
be also employed for cementing the iron ores; neither do I confine myself to
the use of gas such as is prepared from coal only; but I claim also the use of
gas resembling coal gas in its general composition, the same being made
from peat, wood, or other materials, the said gas being such as to consist
mainly of carburetted hydrogen or of olifiant gas, or of both combined in
various proportions together, and occasionally with carbonic oxide, hydrogen,
&c., as is well known to persons making gas for public use. I do not claim
any particular mode of generating the said gas or gases, or the vapour to be
herein-after and above named, but I claim the use of them for the purpose
of cementing the ores of iron. I use the coal gas, or gas resembling coal gas,
and the said vapour indifferently, whether I propose to make malleable iron,
steel, or cast iron from the cemented ores; but I make use of carbonic oxide
gas only in order to make malleable iron, or where it is not intended that the
ores should absorb any carbon during their cementation in the retorts. When
I use the vapour of naphtha or coal oil, of petroleum, of camphine, or other
hydrocarbon, I submit the fluid hydrocarbon to heat in proper vessels, as in the
ordinary distillation of the same, and I pass the said vapour when so obtained
through the heated iron ores in the retorts, as I do the gas, but with this
difference; that I conduct the said vapour at its exit from the retorts into a
worm with a refrigerator, whereby it is again condensed for use. Also in
order to carry off any gas which may be evolved from the said vapour by the
action of the heated iron ores thereon, I employ a main pipe connected with the
condenser and leading to a gasometer, as in the use of the gases. After the
gas has passed from the retorts into the main m, m³, which I call the exit main,
it is to be purified again by any of the ordinary methods, so as to become free
from useless ingredients and fit for further use. It will be convenient to have
several series of retorts and mains to be used successively in employing the
gas over again; as the fresh gas contains most carbon, the first of the series
should be employed where steel or cast iron or malleable iron is sought to be
produced; and the second, where malleable iron is the proposed product and
less carbon is required. In all cases it will be desirable to employ at the exit
main a trial jet, by means of which the composition of the gas may be examined
at pleasure. There should also be a receptacle connected with the retort
itself, such as to admit of its being cut off from the body or current of gas in
the retort, and of its withdrawing a portion of ore for examination; or a trial

page_text: retort, by the aid of which, charged at the same time with the ordinary retorts,
the progress of the cementation of the ores may be carefully watched by the
workman, and the same arrested at the proper point.
The process will now be as follows:-The retorts must be charged with tho
prepared iron ore, closed carefully, and if need be, luted with fire clay, and freed
from atmospheric air by the gas jet before described; the gas, previously heated
or not, is then to be passed in a gentle current through the heated retorts by
appropriate pressure on the gasometer or otherwise; it will then act upon the
iron ore as follows:-The ore being mainly an oxide of iron, the hydrogen of
the gas, or hydrocarbon, if such be employed, unites with the oxygen of the
ore to form water, while the carbon unites with the oxygen to form carbonic
oxide or carbonic acid, as the case may be, thus leaving metallic iron as the
results. It is best to carry this process of cementation a little further (except
where carbonic oxide gas is used), so as to allow of a small absorption of
carbon by the reduced metal; this carbon is readily burned away in the puddling
furnace next afterwards to be used. The iron ore being so far reduced, and
whether absorption of carbon has or has not taken place, the next stage of the
process, when malleable iron is the proposed product, is to shut off the gas on
both sides of the retorts, then to open the retorts and to transfer their contents,
that is to say, the reduced iron ore, to the ordinary puddling furnace, and to
treat the iron as in the common way of puddling iron, until it "comes to
nature," as it is technically termed, and balls, or coheres, or agglutinates
together into a mass, when it is to be put under the shingling hammer and
rolled out, according to the ordinary methods of manufacture. It may be
further cut, piled, reheated, and rolled as usual, according to the nature of its
destination or the quality required. If stéel be the product required, the
cementation in the retorts must be carried further, until the reduced metal
shall have absorbed about one per cent. of carbon, after which the gas is to be
shut off, the retorts to be opened, and their contents removed as before. The
progress of the absorption of carbon must be examined from time to time, just
as is at present done in the cementation of iron bars for conversion of the
same into steel, until the requisite degree of cementation is attained. The
reduced and cemented ore is then to be put into crucibles or melting pots, and
to be run down into ingots in wind furnaces, as is now done in the making of
cast steel. If the earthy matter in the ore be such as to require it, some
proper flux for the same is to be added, according to the known methods of
fluxing iron ores. If cast iron be the product required, the cementation must
be carried on until the metal shall have absorbed about three to four.per cent.
of carbon, after which it it to be transferred to the cupola or blast furnace,

page_text: -with-a-proper nux, if need be, to be run down as is usual in making cast
iron.
I further claim, where cast iron or steel is the product required, the separate
cementation of iron ores with charcoal, coke dust, anthracite coal, coke, &c.
in close retorts or kilns heated as above, but I do not claim the use of char-
coal in retorts for the production of malleable iron directly from the ores.
After such last-mentioned cementation by means of charcoal, the cementel
ores are to be transferred to the cupola or blast furnace, or so the melting pot,
as before, according as cast iron or steel is the product to be obtained.
I clain, moreover, the treatment in manner following of certain ores of
iron in order to the production of steel; namely, the pure specular ores of
iron, the red hematite or oxide of iron, the brown hematite or hydrated oxide
of iron, the black oxide of iron, the red and brown ochreous iron ores (when
the same are not combined with much earthy matter), the magnetic iron ores,
and the ores called spathose (or spathic) iron ores, sparry iron ores, or some-
times white iron ores (from their color being accidentally white), the said
spathose ores being carbonates of the protoxide of iron, and being other than and
different from the argillaceous iron ores of the coal measures or carboniferous
series of rocks above the mountain limestone. The said term, videlicet, " spa-
those ores," is a received and general description of the minerals in question, and
is applicable and applied to them, even when from partial decomposition they
pass into the peroxide of iron, or are combined with it in greater or less propor-
tions. I first prepare any of the ores last before mentioned by roasting them if
necessary to expel volatile matters, and by previous cementation to about one
per cent. on the weight of the metallic iron in the ore by some one or other
of the methods before described, and I then smelt them in a blast furnace or
cupola, or other suitable furnace, with wood or peat charcoal, or any fuel free
from sulphur, using a proper flux, if necessary, of a nature suited to the earthy
matters contained in the ore to be smelted, according to the present methods
in use.
The furnace or cupola, if such be employed, must not exceed twenty
to twenty-five feet in height, and must be constructed so as to be very steep
in the boshes, in order that the charges of ore, flux, and fuel may pass rapidly
through it, and that the metal in coming down may absorb as little more
carbon as possible, and the lowest temperature is to be used which is sufficient
completely to bring down the metal; the metal so obtained I call "steel
metal." For coarse purposes this metal may be worked up directly without
further preparation as an inferior steel, by tilting or hammering and rolling it
as usual. For finer purposes, and where superior quality is required, I take
this "steel metal" and I melt it again more than once, if need be, in crucibles

page_text: or melting pots, as in the common way of making cast steel, by means of wind
furnaces, for the purpose of rendering the ingot when cast as homogeneous as
possible. It may be desirable to obtain such ingot with varying proportions
of carbon in it, according to the purpose for which the steel may be destined,
and these proportions will be obtained by varying the degree of previous
cementation of the iron ore accordingly. It may further be necessary to
correct any excess or any deficiency of carbon in the "steel metal;" the excess
may be corrected by the addition of a small quantity of very pure oxide of
iron, or of the oxidized scales thrown off the bars of steel by the hammers or
rolls, and the deficiency may be corrected by the addition of a small quantity
of charcoal in each case to the crucible or melting pot before putting it into
the wind furnace. For very superior and highly homogeneous steel, it may
be necessary to re-melt the "steel metal " more than once. The average
proportion of carbon to be aimed at is about one per centum of the whole
weight both in the previous cementation of the iron ores whether for making
malleable iron, steel, or cast iron, and in adjusting the proportion of carbon in
the "steel metal," and in the ingots of steel much must be left to the care and
the skill of the workman, and just as in the present cementation of iron bars for
the conversion thereof into steel, the progress of the operation must be care-
fully watched throughout. Where malleable iron is the product to be obtained,
the progress of the operation may be conveniently tested by cutting the ores
with a file or a knife and by trying the filings with a magnet. When tho
final ingot of steel is obtained, it may be hammered out or tilted, cut, piled,
re-heated, and rolled out to the proper size, according to the methods well
known and used in manufacturing steel.
In respect to this last branch of my Invention, I do not claim the simple
reduction of the said ores of iron by smelting them with wood or peat
charcoal, or other fuel, into what is called "natural steel;" but what I do
claim is, the combination of the above process of previous cementation with
such smelting, and these (or the last-mentioned simple reduction) with the
re-melting of the said "steel metal" in crucibles or pots, in order to render-
ing the same perfectly homogeneous and of superior quality.
I use also, by means of a series or sets of retorts, such as I have above
described, the gases which are at present evolved from blast furnaces, and
are consumed and burned at the heads thereof. I collect these gases by
means of pipes or other convenient apparatus attached to the furnace in tho
higher parts thereof, closing up the head of the furnace entirely if necessary,
and in such case charging it through a sliding door or revolving hopper in the
side of the tunnel head as gas-tight as may be; I then purify the said gases

page_text: by passing them-through water and an ordinary purifier like those now used
in gas works, and I conduct them into gasometers communicating with the
mains connected with the retorts, and I then employ them in preparing iron
ores, just as I do the other gases before mentioned and described i or I pass
the said gases at once and without purification or collection in gasometers
through the retorts directly in their heated state.
I do not claim any particular form of apparatus for collecting the said
gases, nor do I claim the employment of them for other purposes than the
cementation of iron ores as before described. The said last-mentioned gases
consist of a mixture of nitrogen, oxide of carbon, hydrogen, carburetted
bydrogen, and other gases or vapours; but I claim the use of them in their
actual state of combination or mixture, and just as they may happen to be
generated, and after purifying them as above mentioned, or without such
purification and directly from the furnace, as above described.
And, lastly, I claim the use of the above-described spathose iron ores, and
the ores called "soft mine" derived from them by partial decomposition, and
found in the same mine therewith, as a flux to supersede the use of limestone,
which is at present used as the flux in blast furnaces in the making of cast
iron, and I use the said spathose ores as follows:-First, I roast them to drive
away the carbonic acid and the water which are contained in them, and then
I mix them, either first cemented as above, or not, with some of the other ores
of iron, in such a proportion by weight that the lime contained in the aggregate
of the ores and of the fuel may bear the same proportion to the other earths,
silica and alumina, in the same aggregate as the lime derived on the whole
from the limestone now used from the other ores and from the fuel is made
to bear to the said earths, silica and alumina, in the last-mentioned aggre-
gate of limestone ores and fuel. This proportion according to the known rules
being thus: alumina as one, lime as two, silica as three, and the spathose
iron ore containing a considerable proportion of lime as its earthy matter, and
often oxide of manganese, I substitute it as a flux for the limestone now used.
When richly carburetted cast iron is sought to be produced, the furnace should
be made flatter in the boshes so that the charges may descend slowly, and
that the ores, especially if not cemented previously, may have time to absorb
the required proportion of carbon.
In witness whereof, I, the said Francis Charles Knowles, have hereunto
set my hand and seal, this Fourth day of January, in the year of
our Lord One thousand eight hundred and fifty.
FRANCIS C. (L.S.) KNOWLES.

page_text: AND BE IT REMEMBERED, that on the Fourth day of January, in the
year of our Lord 1850, the aforesaid Sir Francis Charles Knowles came
before our said Lady the Queen in Her Chancery, and acknowledged the
Specification aforesaid, and all and every thing therein contained and specified,
in form above written. And also the Specification aforesaid was stamped
according to the tenor of the Statute made for that purpose.
Enrolled the Fourth day of January, in the year of our Lord One
thousand eight hundred and fifty.