Named after the Titans in Greek mythology, the element titanium has

been known to exist since the late 18th Century. The technological

development and application of the metal and its alloys, however, have

only been making significant advancements in the US since the end of

World War II. For the past 60 years or so, US industry, academia and

government have been engaged in efforts to unravel the refining and fabrication problems posed by this metal, which

holds several promising properties and characteristics. Processing titanium was a particular challenge, partly because the metal becomes very

chemically active at elevated temperatures. One

of the more notable achievements in the advancement of titanium fabrication technology was the

development of rammed graphite casting. This

casting process, which is the subject of the feature

article in this issue, has been in use for more than

half a century.

The properties of titanium remained somewhat

of a mystery into the early part of the 1900s. For

example, it was initially believed to have a melting

point greater than 6000°F. The General Electric

Company looked into using the pure metal form

for lamp filaments to replace carbon. This pursuit

was dropped when it was determined that the

actual melting point of nearly pure titanium was approximately 3000°F,

and the company settled on tungsten instead. In addition, there were several attempts to develop a large scale process for reducing pure titanium

from its naturally occurring ore form. It took until the middle part of the

20th Century before a commercial scale process was developed for producing raw titanium stock. By the mid-1950s titanium production grew

to significant levels. Ever since, the production of titanium has been dictated by the demands of the aerospace and defense industries, which cycle

through highs and lows. The significant technological advancements for

the metal and its alloys have also traditionally been driven by the aerospace and defense industries. 

This past spring I came across a historical relic that was very influential in the development of titanium technology. At the conclusion of 

the Aging Aircraft Conference in Palm Springs, California, I drove to

Palmdale to visit my brother and sister-in-law. (Palmdale is a small city in

Antelope Valley, which is on the western edge of the Mojave Desert and

the home of Lockheed Martin’s famous Skunk Works®*.) While there 

my brother and I went to Blackbird Airpark, a relatively small, outdoor

aircraft museum that is now the home of a few very historic 

aircraft. Among the notable aircraft on display was the A-12 #60-6924,

the first A-12 ever flown. The A-12 aircraft (the original Blackbird and

predecessor of the more famous SR-71) was developed in the late 1950s

and early 1960s for the Central Intelligence Agency (CIA) under a highly

secret program, Project OXCART; it was designed as a potential replacement for the U-2, a high-altitude reconnaissance aircraft. 

The design and material selection for the A-12 was daunting due to the

supersonic and high altitude performance requirements. The aircraft

skin, for instance, would be subjected to high temperatures, which precluded most common aircraft metals from use. The one metal that could

bring their design concept to reality was titanium, even though there were

several technological advancements that would need to occur first. Ultimately, a beta titanium alloy, which had a great

strength-to-weight ratio and good resistance to

high temperatures, was selected. Practically the

entire aircraft was made from titanium. Machining

of titanium was also especially difficult, and new

tooling was developed for the explicit purpose of

fabricating titanium parts for the A-12.

Even though the program was highly secret, 

President Johnson acknowledged that the US had

been engaged in an effort to develop an advanced

jet aircraft. (He did intentionally mention the name

of an earlier design, the A-11, rather than identify

the existence of the A-12.) The President also noted

during his public announcement that a “mastery of

the metallurgy and fabrication of titanium metal”

had been achieved to help make the program a success. In this case, the need for an advanced aircraft

design pushed the technological development of

titanium metallurgy and manufacturing processes, ultimately resulting in

the A-12 – the first aircraft built out of titanium. Its famed successor, the

SR-71, was also built out of titanium.

The history of advancements and applications of titanium technology

is interesting, especially the era between the late 1940s and early 1960s,

and much of this history has been preserved. AMMTIAC is a center 

that is the culmination of numerous predecessors, the most notable of

which was the first: the Titanium Metallurgical Laboratory, established in

1955. Much of the history of the development titanium, therefore, has

been preserved in AMMTIAC’s library. If you’re interested in any legacy

or current information on titanium, do not hesitate to contact me. And

if you’re ever in the Palmdale area, I highly recommend making a stop at

Blackbird Airpark.

Ben Craig

Editor

GENERAL REFERENCES AND NOTE:

“Titanium Progress to Date,” Titanium Metallurgical Laboratory, March 25, 1957.

D. Eylon and S.R. Seagle, “Advances in Titanium Technology – an Overview,” 

Science and Technology of Light Metals in the 21st Century, Journal of the Japan

Institute of Light Metals, Vol. 50, No. 8, 2000, pp. 359-370.

T.P. McIninch, “The Oxcart Story – Record of a Pioneering Achievement,” CIA

Historical Review Program, Central Intelligence Agency, 1994. (Approved for

Release)

* Skunk Works is a registered trademark of the Lockheed Martin Corporation.

A Brief History 

of Titanium

(Metal of the Titans)

The AMMTIAC Quarterly is published by the Advanced Materials, Manufacturing, and Testing Information 

Analysis Center (AMMTIAC). AMMTIAC is a DoD-sponsored Information Analysis Center, administratively

managed by the Defense Technical Information Center (DTIC). Policy oversight is provided by the Office of the

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Inquiries about AMMTIAC capabilities, products, and services may be addressed to 

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EMAIL : ammtiac@alionscience.com URL : http ://ammtiac.alionscience.com

We welcome your input! To submit your related articles, photos, notices, or ideas for future issues, please contact:

AMMTIAC

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Editor-in-Chief

Benjamin D. Craig

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Product Sales

Gina Nash

The A-12 #60-6924 – the Original Blackbird and First Titanium Aircraft – Located

at Blackbird Airpark in Palmdale, CA.
INTRODUCTION

Design engineers are faced with multiple considerations when it

comes to component design and fabrication for military applications, including ease of assembly, weight reduction, structural

integrity, corrosion resistance, long term maintenance costs, and

overall affordability. These considerations often conflict as design

engineers begin to weigh the costs and benefits of each option. 

In the quest to achieve the best cost/benefit scenario, older 

technologies can get overlooked in favor of newer technologies. A

prime example of an older technology that can meet today’s needs

is titanium rammed graphite castings for military applications.

HISTORY

Titanium rammed graphite castings have been used for commercial and military applications since the late 1950s. Originally, the

cast titanium parts were desired because of their superior performance in severe service applications like seawater, but design

engineers quickly discovered that other benefits could also be

realized by utilizing cast parts. A primary benefit was the ability

to produce near net shapes that required less material, less

machining, and reduced scrap. Titanium’s weight advantage

compared to steel also became an advantageous characteristic.

Over the last 50 years, titanium rammed graphite castings

have been used for multiple military applications, such as fire

pumps, water pumps, condenser head covers, and hose-to-hose

pipe connectors on surface ships, torpedo ejection pumps, large

seawater pumps, various sizes of ball, gate and butterfly valves,

and other defense components. Figures 1 and 2 show examples

of four different titanium components made using the rammed

graphite casting process.

THE PROCESS

Patterns and Molds

Titanium rammed graphite castings are made using wood, metal or

plastic patterns to produce a mold, as illustrated in Figure 3. Similar

to conventional sand castings (see sidebar), rammed graphite castings

use the standard cope and drag patterns, with and without cores.

Many parts can be cast using the same patterns originally constructed for the casting of other metals. Standard loose or match-plate 

patterns made of either wood or metal can be used for titanium

rammed graphite castings. Standard core boxes can also be used

unless they are designed to be used for core blowing only. Most patterns for ferrous and nickel-based alloys will conform dimensionally.

Pattern shops can accommodate modifications or new construction.

Generally, pattern equipment designed for sand casting processes can

also be utilized with modifications to gating and riser systems.

Titanium is very reactive in the molten state, and therefore

graphite is used as a mold medium. Graphite powder is mixed

with water, pitch syrup, and starch, which act as binders. This

mixture is pneumatically tamped and rammed around the pattern

to form the mold.

Stephanie O’Connor

ATI Wah Chang, an Allegheny Technologies Company

Albany, OR

http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 3

Figure 1. Cast Titanium Pump Casing (Left) and a Cast Titanium

Seal Head (Right).
4 The AMMTIAC Quarterly, Volume 2, Number 1

The mold is air dried for approximately 24 hours to achieve a

green (uncured) strength before it is baked at a low temperature to

prevent steam generation and cracking during the firing step. The

amount of baking time depends on the thickness and shape of the

mold. Molds are fired in excess of 1500°F to develop the final

bonds and to burn off binders, resulting in a hard and rigid final

product. The molds are then cleaned and assembled, and gates and

risers are cut into the molds (Figure 4). These must be carefully

designed to allow the proper flow of molten material during the

casting process and to ensure that shrinkage takes place in the gates

and risers rather than in the finished casting. The maximum size of

a titanium pour is approximately 1800 pounds, yielding an end

cast part that weighs about 1300 pounds; however, larger castings

have been produced by utilizing multiple pours and molds. The

maximum single pour has been 50 inches in diameter by 72 inches in height. Wall thicknesses as thin as 0.1875 inches have been

produced using the rammed graphite method.

Melting and Casting

Titanium rammed graphite castings are currently melted using a

vacuum arc skull furnace. This method uses consumable electrodes

that are melted into a water-cooled copper crucible; electrodes are

either forged billet, consolidated revert, or a combination of the

two. The mold assembly is placed on a table in the bottom of 

the furnace where the titanium can be centrifugally or statically

cast depending upon the geometry and specifications of the casting. Extreme care must be used during the melting process since

titanium can easily be contaminated by oxygen, hydrogen and

nitrogen. The furnace is sealed, a vacuum is drawn and an arc is

struck on revert material placed in the crucible, and the titanium

is then melted. When the proper amount of material is melted, the

crucible is tipped and the molten material is poured into the mold.

The mold assembly is left in the furnace under vacuum until the

metal has cooled to the proper temperature.

After the mold assembly is taken out of the furnace, the graphite

is removed by traditional “knockout” methods, and the gates and

risers are cut off by an oxyacetylene torch. The metal surfaces in

contact with the mold will have a carbon-contaminated layer,

which must be removed by blasting and/or pickling. The pickling

solution is generally a mixed acid solution of 15 to 30 percent

nitric acid and 3 to 5 percent hydrofluoric acid, with the balance

being water.

Finishing and Testing

Once the “knockout” has been completed, the casting goes through

nondestructive testing (NDT) and inspection to determine any

necessary finishing processes for the casting. Depending on the

product and customer specification, castings may be inspected

using visual, liquid penetrant, and/or radiography methods; castings may be checked for dimensional precision as well. Common

Figure 2. Cast Titanium Enclosed Impeller (Left) and Cast Titanium Valve Body & Bonnet (Right).

Figure 3. Wood Pattern Used to Produce Rammed Graphite Molds.

Figure 4. Fired Molds Waiting to Have Gates and Risers Cut Before

the Pour.
http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 5

finishing processes include sandblasting, grinding (Figure 5) and

hot isostatic pressing (HIP). Chemical composition and mechanical properties can also be evaluated.

During the HIP process, the castings are placed in a vacuum

chamber, the temperature is raised to 1500°F and a pressure of

about 16,000 psi is applied. The voids are “healed” by pressing 

of the material. After the HIP process, penetrant inspection is

usually performed. Defects found through penetrant inspection

include porosity and voids on

the surface of the cast part. If any

of these defects are found, the

casting is weld repaired. Radiographs of castings can also be

performed to detect if there are

any possible graphite inclusions

that were not healed during the

HIP process. Such inclusions 

are very rare. The combination

of HIP and penetrant inspection

has greatly reduced the need 

for radiography. Eliminating or

greatly reducing the use of radiography can cut the cost and

lead time for a cast part significantly and, therefore, should

only be considered for the most critical applications or on a

sample basis.

THE ADVANTAGES OF RAMMED GRAPHITE CASTINGS

Titanium rammed graphite castings have become a viable alternative to the conventional fabrication methods of titanium plates and

components. The labor intensive fabrication methods that previously relied on cutting, machining, and fitting plates to be welded

are being replaced by simpler near net shape castings. Titanium

foundries have successfully replaced welded fabrications on many

occasions. This provides engineers with less costly near net shaped

castings that have a lower chance for error because there are generally fewer welds on a casting than on cut, fitted plates.

The fact that a rammed graphite casting is repeatable is also very

desirable to contractors and end users. The low upfront cost of patterns is desirable and affordable when compared to the tooling

required for investment castings. Titanium castings use a pattern

that is dimensionally correct each and every time, based upon the

end users’ drawing requirements. The casting will maintain the

dimensions that are designed into the pattern, so the larger

envelopes that often accompany forgings, billet, and plate stock

will be eliminated by utilizing casting technologies. A near net

shape can eliminate extra hours of machining and milling as well

as solve the problem of handling the extra chips and turnings that

are generated by machining large amounts of titanium.

Rammed graphite castings often provide the advantage of being

more readily available than fabricated or machined components.

The current titanium market is experiencing unprecedented lead

times for mill products such as plate, billet, and forgings. It is not

unusual to wait 30 weeks for the arrival of the raw materials before

any fabricating or machining can take place. Rammed graphite

casting lead times can be significantly shorter because the melt

stock raw materials are more readily available than mill products,*

and processing lead times for rammed graphite castings are much

shorter than that for plate, billet, and forgings. Generally, a prototype casting can be available within a 15- to 20-week lead time,

which also includes the production of the patterns. More complex

parts may require longer lead times.

CASTINGS FOR THE MILITARY

Titanium rammed graphite castings have been used in the military

for many years, but only recently companies that design tanks

and fighting vehicles for the US

military have been interested in

these products. The lightweight

and durable characteristics associated with titanium have caused

designers to consider titanium

rammed graphite castings for a

growing number of applications

on military vehicles. Suspension

system components have been

reviewed and prototype castings

have been produced for a number of companies with very good

results. The combination of being

lightweight, having good fracture

toughness qualities, and the ability to produce near net shapes have

made some engineers sit up and take notice. Idler wheels, idler

arms, sprocket carriers, and other components for suspension systems are ideal candidates for titanium rammed graphite castings.

Titanium rammed graphite castings are cast from any number of

grades of titanium. Grades 2 and 3 are commercially pure and are

the most requested grades for chemical processing applications. In

applications where corrosion is more severe, grades 7 and 12 are

often chosen. Grade 5 (Ti-6Al-4V) is a popular alloy for applications where strength and ballistic resistance properties are an issue.

Recently accepted by the ASTM as Grade 38, Ti-4Al-2.5V currently is being considered for military applications. Grade 38 has

proven to be very castable and much easier to pour than Grade 5,

which historically has been used for military applications. In their

short existence, Grade 38 titanium castings have found their way

into a number of military applications and in some cases have

replaced Grade 5 castings. The advantage in specifying Grade 38

titanium castings is cost savings. While the properties between

Grade 5 and Grade 38 are similar, Grade 38 has a slight pricing

advantage over Grade 5 because the raw material cost is lower.

There is also an added corrosion benefit with Grade 38 titanium

over Grade 5. To date, Grade 38 titanium has been selected for

suspension system applications, cast hatch covers, and other 

components for fighting vehicles. Ballistic tests on cast Grade 38

materials are currently underway to determine its level of threat

resistance capabilities. Table 1 shows the chemical compositions of

the titanium alloys commonly used in rammed graphite castings.

Rammed graphite castings play a very important role in the casting marketplace by providing a technically sound near net shaped

cast part to the end customer. By selecting and specifying titanium

rammed graphite castings for military and defense applications,

near net shape technology can be utilized, eliminating unnecessary

scrap accumulation and the machining of oversized sections.

Figure 5. Flash Being Ground Off of a Casting; One of the Many

Finishing Techniques Used.
CHARACTERISTICS OF CAST TITANIUM

In Corrosive Environments

The majority of titanium alloys (wrought or cast) are very resistant

to corrosive attack and virtually immune to many oxidizing and

reducing environments. This is due primarily to a tenacious oxide

film that is formed when titanium is exposed to the atmosphere.

The oxide film acts as a barrier to the surrounding corrosive environment and thereby protects the titanium alloy from further 

oxidation and corrosion. By combining titanium with small

amounts of palladium or molybdenum and nickel, the corrosion

resistant properties of the titanium alloy can be improved further.

Strength and Structural Integrity

Unlike aluminum and steel alloys, which tend to lose structural

integrity and strength when cast, titanium tends to maintain

structural integrity and strength that is comparable to wrought

titanium products. Table 2 illustrates this point by comparing

tensile and yield minimums for wrought and cast titanium alloys

commonly used in chemical processing and defense applications.

Dimensional Control of Titanium Rammed Graphite Castings

Rammed graphite castings made with titanium alloys are either

static or centrifugally cast, depending on the shape and size of

the cast part. Common tolerances for titanium rammed

graphite castings are listed below; tighter tolerances can be

achieved with additional trials and correction efforts:

• Minimum Section Thickness: 3/16", 1/8" if less than one

square inch of surface

• Base Tolerance:

• Up to one linear inch: ± 1/32"

• 1 inch up to 10 inches: ± 1/16"

• 10 inches up to 20 inches: ± 1/8"

• 20 inches up to 60 inches: ± 3/16"

• Additional Tolerances:

• For dimensions across the parting line: ± 1/8"

• Added tolerance for dimensions affected by parting line and 

parallel to the parting line (mismatch):

• Less than 10 inches: ± 1/16"

• 10 inches and above: ± 1/8"

• Radius Dimensions:

• General radius conforms to base dimensions

• Sharp to 1/8" radius ± 1/32" (convex)

• Up to 1/2" fillet radius ± 1/32" (concave)

• Finish Stock:

• Nominal 1/8" on all machined surfaces on dimensions less 

than 12"

• Nominal 3/16" – 1/4" on all machined surfaces greater 

than 12"

• Angles: ± 1 degree

6 The AMMTIAC Quarterly, Volume 2, Number 1

Table 1. Chemical Compositions of Various Grades of Titanium.

Chemical Composition, max wt.% 

ASTM Designation Ti (min) C H O N Fe Others

Grade 2 98.885 0.10 0.015 0.25 0.03 0.30 0.30

Grade 3 98.885 0.10 0.015 0.35 0.05 0.30 0.30

Grade 5 Remainder 0.10 0.015 0.20 0.05 0.30 6.75 Al, 4.50 V

Grade 7 99.005 0.10 0.015 0.25 0.03 0.30 0.12-0.25 Pd

Grade 12 Remainder 0.10 0.015 0.25 0.03 0.30 0.2-0.4 Mo, 0.6-0.9 Ni

Grade 38 Remainder 0.00 0.00 0.25 0.00 1.50 4 Al, 2.5 V

Casting is a manufacturing process that has been in use for several millennia; cast metals, for example, have been

dated back to 4000 B.C. There have been advancements in the process over the years, but the basic principles have

remained. A molten or liquid material (either a metal, polymer, or ceramic) is poured into a mold, where it conforms to the shape of the cavity, and then is solidified to create a finished or nearly finished product. The process

is often used to efficiently form complex parts and is typically a cheaper route compared to the alternative 

fabrication methods, such as forming or machining from a solid. The size of the castings can range from hand held

pieces (and smaller) to multi-ton items such as ship propellers.

A pattern is the three dimensional model that is designed and used to create a mold cavity, which will ultimately

form the final casting product. Patterns can be reusable or expendable. The reusable patterns are typically made from

wood, metal, plastic, or a composite material and can be used to make duplicate molds. Expendable patterns, on the

other hand, are made of materials such as wax, polystyrene, or other plastics and are disposed of after making the

mold. In the case of the lost Styrofoam® method, the pattern is vaporized during casting process.*

Traditionally, the molds for casting metals have been made with prepared sand (called green sand casting because

it is unfired), although other materials can be used. Typically these mold materials include a binding material (clay)

and a small percentage of water so that after molding the sand retains the exact inverse of the pattern shape. The

prepared sand retains an imprint of the pattern to create the casting cavity that will eventually host the molten

metal. A common practice of casting metals is to create the mold in two parts. The top part of a mold is called 

the cope and the bottom part is called the drag. These two components are separated at what is referred to as a

parting line. Molds are held in place and supported during the casting process using a frame called a flask, which

is typically made of wood or metal. A core is a separate solid material within the mold cavity that is used to make

an internal void or passageway in the final product. The pattern is modified to allow for the positioning and retention of the core in an exact location. Figure 1 illustrates some of the common components of a mold.

The Basics 

of Metal

Casting

Benjamin D. Craig

AMMTIAC

Rome, NY

* Styrofoam is a registered trademark of the Dow Chemical Company.
Size and Weights

While the size and weight of titanium rammed graphite castings

can vary depending on the manufacturer, 1 to 1300 pounds is a

common weight range for cast titanium alloys. Larger castings

can be produced by fabricating several castings into a single 

component. In certain configurations, casting weights in excess

of 1300 pounds are possible but they should be evaluated on a

case by case basis.

CONCLUSION

While titanium rammed graphite castings are not new to the

military, they are often overlooked as an alternative to traditional manufacturing processes and wrought products utilized in 

the production of defense components. Today, design engineers

can realize many military objectives by utilizing titanium

rammed graphite castings to ease the burden of assembly, reduce

component weight, maintain structural integrity, increase 

corrosion resistance, cut back lead times and reduce long term

maintenance costs. While titanium rammed graphite castings

may not be the newest technology available, it certainly could be

the best choice – especially when weighed against the military

objectives of today and tomorrow.

NOTE AND REFERENCES

* Melt stock raw materials are more readily available than mill products

because mill products must be manufactured from the ground up,

whereas melt stock raw materials can be taken from mill products that

have already been produced and are in the inventory.

[1] “ASTM Designation B 367 – 06,” Standard Specification for 

Titanium and Titanium Alloy Castings, ASTM.

[2] “ASTM Designation B 265 – 06b,” Standard Specification for 

Titanium and Titanium Alloy Strip, Sheet, and Plate, ASTM.

GENERAL REFERENCES

M. Guclu, I. Ucok, and J.R. Pickens, “Effect of Oxygen Content on

Properties of Cast Alloy Ti-6Al-4V,” Symposium on Cost-Affordable 

Titanium, Charlotte, NC, March 2004, The Minerals, Metals & 

Materials Society, Inc., pp. 135-143, DTIC Doc.: AD-P016696.

D. Eylon, F.H. Froes, and L. Levin, “Effect of Hot Isostatic Pressing 

and Heat Treatment on Fatigue Properties of Ti-6Al-4V Castings,” 

Proceedings of the Fifth International Conference on Titanium, 1985, 

pp. 179-186, DTIC Doc.: AD-D135659.

R.D. Williams and J. Dippel, “Comparisons of Titanium Investment

and Rammed Graphite Castings,” Titanium Net Shape Technologies, 

The Metallurgical Society of AIME, 1984, pp. 193-199, DTIC Doc.:

AD-D134602.

More Titanium Rammed Graphite Castings reports available through

Private STINET and TEMS. Qualified users can access these databases

through the DDR&E Research Portal (https://rdte.osd.mil/).

The mold cavity in the cope and drag can be formed using different types of patterns, such as a standard loose 

pattern or a match plate pattern. The match plate has a pattern mounted on both sides of the pattern plate and

conforms to the parting line between the cope and the drag parts of the mold. The match plate system typically

uses an interlocking feature that surrounds the exterior edge of

the pattern. This ensures a very accurate registration of the mold

halves and restricts movement of the mold during solidification

of the metal.

During the casting process, shrinkage of the casting material can

occur during solidification. To account for this, risers are used

which act as a molten metal reservoir to fill any voids created when

the casting shrinks inside the mold cavity. Risers that do not have

an outlet on the topside of a cope are called blind risers. Vents are

used to allow for gases to escape in order to reduce the occurrence

of voids in the casting. A sprue is the vertical channel in the mold

that connects the pouring basin to the gating system. Some molds

do not have a pouring basin, in which case the molten metal is

poured directly into the sprue. The gating system is a series of passageways that distributes the molten metal between the sprue and

the casting cavity. Design of a proper gating system is important

because it allows the liquid to flow and enter the casting cavity properly in order to avoid defects in the final casting. 

The use of so called green (unfired) or fused sand allows for the easy removal of the sand from the solidified 

material. Additionally, the sand can be reprocessed, and when clay and water are added it can be used for the next

series of castings.

http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 7

Table 2. Comparison of Strength Specifications for Cast and

Wrought Forms of Various Grades of Titanium [1], [2].

Titanium Grade Tensile Strength, min. Yield Strength 

0.2% Offset, min.

Ksi MPa Ksi MPa

Cast Grade 2 50 345 40 275

Wrought Grade 2 50 345 40 275

Cast Grade 3 65 450 55 380

Wrought Grade 3 65 450 55 380

Cast Grade 5 130 895 120 825

Wrought Grade 5 130 895 120 828

Cast Grade 38 130 895 115 794

Wrought Grade 38 130 895 115 794

Figure 1. Components in a Green Sand Casting Mold. 

Compacted Green Sand

Gating System

Flask

Parting

Line

Sprue Blind Riser

Vent Hole

Cope

Core

Drag

Mold

Cavity

Pouring Basin
8 The AMMTIAC Quarterly, Volume 2, Number 1

September 2007

Corrosion Solutions 2007 

6th International Conference

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2007 Conference and Exhibition)

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24th Annual ASM Heat Treating Society Conference 

and Exposition

17-19 September 2007

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For additional information:

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2007 SAE AeroTech Congress 

& Exhibition

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For additional information: 

www.sae.org/aerotech

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18-19 September 2007

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For additional information: www.asne-tw.org

Materials Processes & Medical 

Devices Conference 

23-25 September 2007

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For additional information: 

www.sae.org/events/dod/

Advanced Materials and Manufacturing Technology 

for Naval Applications Conference

14-15 November 2007

Baltimore, MD

For additional information:

www.nmc.ctc.com/index.cfm?fuseaction=eventinfo&id=45

National Nano Engineering Conference (NNEC 2007)

14-15 November 2007

Boston, MA

For additional information: 

http://nasatech.com/nano/

December 2007

Tri-Service 2007 Corrosion Conference

3-7 December 2007

Denver, CO

For additional information:

www.nace.org/nace/content/conferences/triservice07/

Calendar of Events
John C. Keefe

Alion Science and Technology

Rome, NY techsolutions 4

http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1

INTRODUCTION

A precious metal (PM) can be defined as a rare metallic

chemical element of high economic value.[1] Precious

metals, as a group, have a set of physical and chemical

properties that are unrivaled by many other materials. If 

the availability of these materials was greater (in both

quantitative and economic terms), there would be far more

application overall. Due to the cost and availability,

however, these materials are limited to applications where

only small amounts are used, such as spark plug tips and

electrical contact plating. Under certain circumstances,

precious metals are used in large quantities for applications

where there is no feasible substitute. In applications and

industries that use a large amount of PM, the capital cost

can be great (tens of millions of dollars), and there is also a

substantial cost associated with managing and securing the

metal assets in a company’s inventory.

The Eight Precious Metals

There are eight precious metals: gold (Au), silver (Ag),

platinum (Pt), iridium (Ir), palladium (Pd), rhodium (Rh),

ruthenium (Ru), and osmium (Os). They are grouped in a

rectangle on the periodic table existing in two periods and

four groups. A subset of this group is called the Platinum

Group Metals (PGM), which includes all but two of the

PMs (Au and Ag).

Mining the Raw Materials

Typically the PGMs are found combined together in rich ore

and are then chemically processed to extract the individual

elements in the group. Also notable are the elements above

the precious metal group on the periodic table: iron (Fe),

cobalt (Co), nickel (Ni) and copper (Cu). All of these metals

have relationships with the eight precious metals, in that

they are found in the primary ore, or they are used as

alloying elements to impart improved properties in many 

of the precious metal formulations. The short supply (there

are only a few major mining locations), economic value 

and costly mining and extraction methods have raised the

cost of these metals to the high prices that exist today.

Gold and silver have been in use for a very long time,

but the other precious metals have a much shorter history.

The discovery of PGMs occurred significantly later since

they are not typically available in the pure metal nugget

form in which gold and silver are found. Mining locations

for the PGMs are very limited. The key areas of PGM

production are the US (Stillwater, Montana), Canada (most

commonly the Sudbury, Ontario area, as a byproduct of

nickel mining), Russia (Norilsk region, which is first in Pd

production), and the Zimbabwe region in South Africa (first

in Pt and first in PGM general production). In 2004, South

Africa produced a total of five million troy ounces (to)* of

Pt (70% of the world’s output) and eight million troy

ounces of PGMs (50% of the world’s output).[2] Today the

processing of PGMs requires about a ton of rich ore to

produce approximately one troy ounce of PGMs at best.

Some mines only produce PGMs on the level of 5 to 25

grams per ton of processed ore. Whereas PGMs are mined in

fewer locations, the occurrence of gold and silver is much

more common and they are found in larger quantities.

BASIC PROPERTIES OF PRECIOUS METALS

The properties of PMs are typically different than conventional metals in two primary areas: melting point (MP) and

density. The melting point for steel (low alloy iron) is in the

range of 2800°F with a density in the range of 7.8 g/cm3;

compare this to the group to see the differences on the

physical property side. These features, coupled with their

resistance to chemical attack, set PMs apart from most other

A Brief Introduction to Precious Metals

9

Table 1. Basic Properties of Precious Metals.

Name (Symbol) Atomic Crystal Melting Density, 

Number Structure Point, °F g/cm3

Ruthenium (Ru) 44 HCP† 4190 12.45

Rhodium (Rh) 45 FCC‡ 3560 12.41

Palladium (Pd) 46 FCC 2829 12.02

Silver (Ag) 47 FCC 1764 10.49

Osmium (Os) 76 HCP 5522 22.61

Iridium (Ir) 77 FCC 4429 22.65

Platinum (Pt) 78 FCC 3216 21.45

Gold (Au) 79 FCC 1947 19.32
techsolutions 4

10 The AMMTIAC Quarterly, Volume 2, Number 1

materials on the periodic table.[3] Table 1 shows some of

the basic properties of the eight precious metals. Several

mechanical properties of the PMs are provided 

in Table 2.

Electrical and Thermal Conductivity

Many of the PMs have excellent electrical and thermal

conductivity properties, as shown in Table 3. Silver has the

distinction of having the highest room temperature

conductivity of the PMs, as well as the highest of all

metals. It should be no surprise that copper is the metal

more predominantly used for electrical wire instead of 

Ag because of the cost difference. The main drawback to

Cu is that it readily forms an oxide film, which can lower

the electrical properties unless the oxide film is cleaned

from the electrical contacts. This problem is commonly

resolved by plating the contact area of Cu electrical 

devices with gold.

Nobility

The precious metals are often called the “Noble Metals”

because they are resistant to most types of environmental

and chemical attack. One of the few chemical solutions to

attack the precious metals (with the exception of iridium)

is aqua regia (Latin for “royal water”). Aqua regia, a

mixture of one part nitric acid (HNO3) with three parts 

of hydrochloric acid (HCl), earned its name because it

dissolves Au and Pt, the royal or noble metals. This

solution is used as an etching solution for metallurgical

analysis of many metals.

APPLICATIONS

As with most materials, the range of applications for PMs

is diverse. However, PM materials are also used in

applications where other materials cannot be used. The

following sections provide an overview of typical PM

applications.

Corrosion Protection

The use of PMs to resist corrosion is long-standing due to

their inherent nobility. Additionally, these metals and their

alloys are used in cathodic protection systems to protect

large systems from the effects of corrosion.

Catalysts

The use of Pt, Pd, Rh and their various alloys as catalysts

in large and small chemical reactors, such as car exhausts, 

is widespread. The catalytic surface can be applied by

“washing on” a rich solution of material onto a ceramic

substrate. The surface can also be a robust construction of

woven wire in order to provide a large-scale surface for

chemical production. These applications account for the

primary usage of PMs. Platinum-based catalysts have been

used for nitric acid production for more than 100 years.

High Temperature Applications

Combining high MP temperatures with the additional

feature of low reactivity at elevated temperatures is a key

characteristic of PMs for many applications. Steel melts at

approximately 2800°F, while Pt has a MP of 3200°F.

Vessels made from Pt, Pt-Rh, and Ir are used in the making

of fiberglass and silicon ingots, as well as for the melting 

of other high MP, reactive media. One clever application

uses Pt and zirconium oxide to form a powdered metal 

that is a highly creep resistant material even when heated

close to its melting point. Zirconia Grain Stabilized (ZGS)

platinum and Pt-Rh alloys have been used in the glass

Table 2. Mechanical Properties of Precious Metals [3,4].

Name Tensile Strength Elongation in Hardness Young’s Modulus (Static) Poisson’s Ratio

(MPa) 50 mm (%) (HV) at 70°F (GPa)

Ruthenium 496 3 220-270 414 0.25-0.31

Rhodium 1379-1586 2 13-100 319 0.26

Palladium 324-414 1.5-2.5 105-110 115 0.39

Silver 290 3-5 25 74 0.37

Osmium - - 31-350 558 0.25-0.28

Iridium 2070-2480 15-18 600-700 517 0.26

Platinum 207-241 1-3 90-95 171 0.39

Gold 207-221 4 55-60 77 0.42

Table 3. Electrical Resistivity and Thermal Conductivity of PMs

Compared to Copper and Aluminum [5].

Metal Electrical Resistivity Thermal Conductivity 

(10-6 ohm-cm) (W/m-K)

Silver 1.55 419.0

Copper 1.70 385.0

Gold 2.20 301.0

Aluminum 2.70 210.0

Rhodium 4.30 151.0

Iridium 4.70 147.0

Ruthenium 7.20 116.0

Osmium 8.12 91.67

Palladium 9.93 71.20

Platinum 10.6 69.10
industry for many years. The addition of zirconium and its

subsequent oxidation during metal spraying create a grain

structure that limits grain growth and increases the high

temperature creep strength.

Thermocouple Devices

Platinum and platinum-rhodium wire pairs for thermocouples are the most effective at measuring temperature.

Platinum thermocouples exhibit the widest range of

temperature measurement, accuracy and linearity, which 

is required for critical applications. Currently, the producers

of wire are able to make wire diameters small enough that

the cost of PM material is kept to a minimum.

High Temperature Heating Coils

A heating coil can obviously only go as high as the melting

point of the material used to construct the device. Additionally, in many operations repeated oxidation cycles can reduce

the life of the heating coil. The use of PGM alloys satisfies

both the issue of high service temperature and the problem

of long-term oxidation attack.

Spark Erosion Resistance Applications

In the new generation of cars and trucks, replacing spark

plugs could be a thing of the past. The development 

and application of Pt alloys, Ir alloys, and pure Ir (some

combinations of PMs are patented) make plugs that 

last for more than 100,000 miles. To accomplish this, some

manufacturers use ball bearing fabrication equipment to

make small Pt alloy spheres that are then resistance welded

onto the plug to form the electrode pair. For the more

critical applications on aircraft, short pieces of Ir rod stock

material are centerlessly ground§ to an exacting size and

form and then installed in the spark plug. Additionally,

electrical contacts with an extended operational life

capability have been made from Pt and Pd strip stock 

for various devices by high speed stamping of small 

crowned circular blanks.

Fuel Cell Applications

Fuel cells are similar to conventional batteries in that they

are silent with no moving parts and generate electrical 

power by an electrochemical reaction within the cell. The

best part about a fuel cell, unlike a battery, is that it 

requires no recharging and it will run continuously as long

as the fuel supply lasts. The electrical output from the 

fuel cell is made by combining hydrogen (the fuel) and

oxygen (from air) over a catalyst such as platinum.

Biocompatibility

Not all materials have the ability to be implanted within or

used in contact with the human body without causing an

adverse reaction or poisoning. Those that can be are termed

biocompatible. The medical devices produced from PMs

include: stents, marker bands for angioplasty devices,

pacemaker wire, heart muscle screw fixations, endoscopy 

tips and special surgical tools. The material used for such

applications is mainly Pt (or alloys of Pt), and in dental

applications the use of Au and Pd is common.

Radio-opacity

X-rays do not easily pass through Pt, Au and Ir because 

of their atomic absorption coefficients, as well as their high

densities, and thus these materials typically show up as a

white area on film or scanning device. This property,

referred to as radio-opacity, coupled with their biocompatibility characteristics allows for the location of these

materials to be determined when used within the human

body. The identified location of these materials is called the

“marker band” because it marks the location to allow the

surgeon to correctly position the angioplasty device within

the body during surgical procedures.

Pharmaceutical Use

Platinum-based drugs, such as cisplatin, have been in use 

for 30 years to treat cancer. The treatment of testicular

cancer with cisplatin has been widely accepted as a standard

course of treatment. A new drug, stataplatin, is under the

last stages of FDA approval for treatment of a form of

prostate cancer. This new drug will offer an alternative to

those patients that did not respond well to chemotherapy.

Gold has also been used for the treatment of prostate 

cancer, whereby small gold “seeds” are irradiated 

and injected into the cancer site to kill the cancer cells 

by the slow release of radiation.

Labware, Equipment & Related Devices

Platinum and gold have an excellent resistance to attack

from many substances, and as such they are used as

crucibles, electrodes, inoculating loops, ignition boats and

many other forms of labware. Since these materials are

noble, the testing method is not skewed by contamination

from the test equipment. Basic forms of material (wire, tube,

sheet, and strip) can be fabricated into countless products as

required for industrial use. Joaquim Bishop, a former lab

assistant at the University of Pennsylvania, established the

first Pt works in the US in 1842 for the purpose of refining

Pt and the production of Pt labware. His early success in

this work earned him a prestigious Franklin Institute silver

medal in 1845 for “skill and ingenuity in the manufacture of

Pt scientific instruments.” Many of the complex Pt alloy

fabrications have been used in the production of glass

melting “bushings” for the fiberglass industry.[6]

Photographic Applications

Photography’s impact on society has been vastly important

over the last 150-plus years since its discovery. During the

formative period of discovery, precious metals played a key

role in making the art a reality. At one time, the Eastman

Kodak Company was the single largest user of silver in the

world. Many films and photo papers used silver compounds

as the light-sensitive emulsion. Platinum and palladium

compounds were used to make black and white printing

paper, which was and still is considered by many to be the

best paper for reproduction of the complex tonality on black

and white negatives. These prints are the most archived of

any produced because of their resistance to environmental

attack. Famed photographer Ansel Adams used gold chloride

http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 11

AMMTIAC A DVANCED M ATERIALS , M ANUFACTURING AND T ESTING
toner to add permanence to his work and advocated this to

all photographers who wanted to extend their work’s life.

Coinage, Collector’s Items and Jewelry

Precious metals have been used throughout history 

for currency and jewelry, as well as other objects that have

become collector’s items. Our ability to examine past

cultures is due, in part, to the nobleness of these materials

since they are able to survive hundreds or even thousands

of years of concealment and burial and still be viable as 

a historical record. Jewelry accounts for the second largest

demand of PMs, with China, Japan and the US accounting

for 85% of the total demand. The history of coinage is

filled with the use of metals, especially gold and silver.

FABRICATION TECHNIQUES FOR PRECIOUS METALS

As with most pure metals, the properties of PMs are

improved by alloy additions. This is true of the precious

metals where the alloying elements are other PMs or similar

metals. This is important especially in machining, where

pure metals cannot be cut as precisely as metals that 

are slightly alloyed due to their ductility and less than

clean shearing nature.

QUICK FACTS ABOUT PRECIOUS METALS [1, 3, 7-8]

Gold

As a material, gold has the longest and most storied history of all the precious metals. The chemical symbol,

Au, is derived from the Latin word aurum, meaning “gold”. It is the most malleable of metals and therefore can

be worked with simple tools to form complex shapes. Gold’s low MP has made it one of the first metals that

could be readily cast. The visual allure of gold and the economic value acquired with its possession have driven

the mining of this PM throughout history. It is used for numerous commercial and industrial purposes. Its excellent 

corrosion resistance and thermal and electrical properties have made it a top design choice for many devices. The ability 

to plate gold in very small thickness still allows for more extensive application of the material. The cost of gold is 

constantly varying; currently it is approximately $668/to.

Silver

Silver has the best room temperature electrical and thermal conductivity of all metals. The largest silver ore 

deposits in the US were discovered in 1859 at the Comstock Lode in Virginia City, Nevada, and in northern

Idaho at the world-famous Sunshine Mine – the richest silver mine in American history, which has had more

than 350 million ounces of production over the past century. The principal sources of Ag are Cu, coppernickel, Au, lead and lead-zinc ores obtained from Canada, Mexico (historically Batopilas), Peru, Australia and the US.

Silver has found many applications primarily because of its lower melting point and ease of fabrication. From coinage and

tableware to its extensive use in the photography industry, silver is part of our lives each day. Silver is the most available

and least costly of the precious metals at $14/to.

Platinum

Platinum was discovered in South America first by Antonio de Ulloa in 1735 and again by Charles Wood in

1741. Platinum occurs naturally and is accompanied by small quantities of the other PGMs. When pure,

platinum is a beautiful silvery-white metal that is malleable. The metal is extensively used in jewelry, wire,

vessels for laboratory use, and in many valuable industrial products including thermocouples, medical devices

and anti-cancer drugs. It is also used for electrical contacts, corrosion-resistant devices, and in dentistry. Platinum-cobalt

12 The AMMTIAC Quarterly, Volume 2, Number 1

techsolutions 4

Table 4. List of Fabrication Methods Used for PMs.

Machining • All methods, including:

• Electrical discharge machining (EDM)

• Wire EDM (especially for Ir crucible making)

Grinding • All methods

Cold working • Rolling

• Drawing (wire, rod and tube)

• Spinning

• Stamping

• Forming

Welding • All methods, including:

• Metal inert gas (MIG)

• Tungsten inert gas (TIG)

• Electron beam

• Laser

Hot working • Forging

• Drawing

• Rolling

• Swagging

Casting methods • Gas fired (low MP materials)

• Induction

• Vacuum induction

• Electron beam (EB) vacuum melting

• Argon carbon arc vacuum melting
AMMTIAC

http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 13

A DVANCED M ATERIALS , M ANUFACTURING AND T ESTING

alloys have powerful magnetic properties. One such alloy, made of Pt-23.3 wt.% Co, offers a maximum magnetic field

strength almost twice that of Alnico V, a strong permanent magnet material. Platinum resistance wires are used in the

construction of high-temperature electric furnaces. It can be drawn into wire, then knit into fabric referred to as gauze, 

and fabricated into a large catalytic surface. Platinum is an excellent catalyst, having long been used in the process for

producing sulfuric acid (H2SO4) and nitric acid (HNO3). There is much current interest in the use of Pt as a catalyst in

fuel cells and in anti-pollution devices for automobiles. The present cost for Pt is approximately $1200/to.

Iridium

Iridium is the rarest precious metal and the densest material known. It was discovered in 1803 in the insoluble

residue from platinum reduction with aqua regia. It earned its name from the highly colored iridium salts.

Iridium is more difficult to mechanically work than any other face-centered cubic (FCC) metal. This has 

been attributed to a reduction in ductility caused by trace element impurities that are picked up during the

mining and refining process. These impurities cause a modification of the grain boundary behavior. Due to its high tensile

strength at elevated temperatures and high MP, it has been used for crucibles in crystal growing. Hot working, which is

mechanical working of a metal above its recrystallization temperature, is one of the few ways to reasonably work the

material. To achieve precise dimensional cutting, either grinding or wire EDM must be used. Iridium possesses quite

remarkable properties. It is the most resistant of all metals to corrosion; it is insoluble in mineral acids including aqua regia.

The earliest uses were for making durable, wear-resistant tips for fountain pen nibs and compass bearings. Resistance to

spark erosion has made this element popular for spark plug applications.

Palladium

Palladium was recognized as an element in 1803. Deposits are found in the former USSR, South and North

America, Ethiopia and Australia. It is a steel-white metal; it does not tarnish in air and it has the lowest density

and melting point of the PGMs. Palladium is attacked by nitric and sulfuric acids. At room temperature the

metal has the unique property of absorbing up to 900 times its own volume of hydrogen. Hydrogen readily

diffuses through heated Pd and development of this property provides a means of purifying the gas. Its alloys are used in

the jewelry trade. White gold is often produced by addition of Pd. Like Au, Pd can be beaten into leaf form as thin as

1/250,000 of an inch. The metal and its alloys are used in dentistry, watch making, surgical instruments, catalytic

converters and electrical contacts.

Rhodium

The name for rhodium comes from the Greek word, rhodon, meaning rose and was selected for the many 

“rose colored” solutions that are distinctive of rhodium’s presence. It was discovered in the early 1800s 

in a crude Pt ore obtained from South America. Rhodium occurs naturally with other PGMs in river sands 

of the Urals and in North and South America. It has a high reflectance and is hard and durable. Sputtering

targets of rhodium are used to make the reflective surface for automobile mirrors and other optical instruments. As 

a bulk metal, it is mostly used as an alloying agent to harden Pt and Pd. Such alloys are used as furnace windings,

thermocouple elements and to make bushings for glass fiber production. An addition of Rh increases both the operation

temperature and the mechanical properties of the material. It is a useful electrical contact material due to its low 

electrical resistance and low and stable contact resistance, as well as its high resistance to corrosion. Rhodium is also 

used for a range of catalyst applications and as alloys and coatings for jewelry. Rhodium has the current distinction 

of being the most costly precious metal at over $6000/to.

Ruthenium

Ruthenium is found naturally occurring along with other PGM members. It was discovered in 1827 when

examining the residues left after dissolving crude platinum from the Ural mountains (Russia) in aqua 

regia. Ruthenium is a hard, white metal mainly used as an alloying agent for platinum. An addition of 0.1%

ruthenium to titanium immensely improves the corrosion resistance. It is a versatile catalyst and can be 

used to promote the splitting of hydrogen sulfide. Pure ruthenium is a very difficult material to work.

Osmium

Used almost exclusively as an alloying agent, osmium has the distinction of having the highest melting point 

of the precious metals. Certain forms (tetroxides) are highly toxic. Osmium tetroxide is used in forensic science 

as a stain for fingerprints, microscope samples and DNA materials. Osmium was discovered in 1803, and 

it occurs in Pt-bearing river sands of the Urals, North and South America, South Africa and elsewhere. 

The metal is lustrous, bluish-white, and extremely hard and brittle even at high temperatures. As a pure metal it has

relatively few industrial uses, but can be used to produce very hard alloys with other PGMs.
The AMMTIAC Quarterly, Volume 2, Number 1

The method for production of PMs into a desired form

is similar to other metals. Platinum is very tough on

tooling for turning, drilling and milling, even when carbide

tools are used. The use of polycrystalline diamond (PCD)

tools, however, can significantly extend tool life when

machining PMs. Typically welding of Pt in air is done with

oxy-hydrogen torches, not oxy-acetylene, in order to deliver

enough heat to the weld area to accomplish the task.

Precious metals have very high MPs, and therefore when

welding or performing any other process where the MP is a

factor, it is important to be able to focus the energy in a

local area to minimize the heat affected zone (HAZ).

The problem areas with PM fabrication come into play

when formability, work hardening or melting point have a

part in the manufacturing process. Iridium most notably

has problems with formability and even though it is a FCC

material, it does not behave as such. This could be

improved by hot working, but since Ir has a MP greater

than 4400°F, the range of hot work temperatures can

quickly compromise the equipment if the process is not

monitored carefully. Table 4 provides a list of fabrication

methods that can be used for PMs.

FUN FACTS

The density of gold and platinum is almost twice that of

lead (Pb, density = 11.34 g/cm3), which has been typically

viewed as being a very dense, heavy material by the general

public. In most of the old western movies, and more

recently in the George Clooney movie, Three Kings (1999),

the “bad guys” are shown loading up stacks of gold bars.

This is a bit far-fetched since many of the bars at the sizes

shown would weigh approximately 80 to 90 pounds. A

saddlebag of these plus the rider would be too much for the

horse, or a human, to carry. Since most people don’t have

the opportunity to actually lift a gold bar, the myth is

perpetuated by Hollywood.

RELATED WEBSITES

For more information on precious metals, check out the

following websites:

Johnson Matthey (JM), www.matthey.com - The main

website of one of only two integrated PM producers in 

the world. JM mines, processes, sells, fabricates, engineers

and basically leads the efforts to apply and promote

precious metals.

Platinum Today, www.platinum.matthey.com - A

website by Johnson Matthey, this is an online magazine

that deals with all things PGM. This is not a technical

review, but rather a readable publication of what is current

in the PM world.

Platinum Metal Review, www.platinummetals

review.com - This is a quarterly online journal that

provides the latest research information on PGM advances

in all technical areas from metal extraction methods to

specific applications. It is a highly technical publication

that contains application information as well as the exact

science of the product or process described.

The PGM Database, www.platinummetalsreview.com/

jmpgm/index.jsp - This is the definitive materials

properties website with very extensive information on 

PGM properties in all of their alloy variations. It is a good

resource for the materials scientist and engineer. General

information is included here too, but it is amongst some

very technical data.

International Platinum Association, www.platinum

info.net - This is a nonprofit association of the leading

mining, production, and fabrication companies in the

global PGM industry.

NOTES AND REFERENCES

* In the PM world a different weight measurement system is used.

The standard unit is the troy ounce. The troy ounce (to) is different

than our common ounce, in that, the troy ounce has a mass of

31.1035 grams versus 28.350 grams for the standard (avoirdupois)

ounce (32.1507 troy ounces = 1 kilogram). Even when handling 

large amounts of precious metal, the quantity is still expressed 

in troy ounces.

† Hexagonal Close-Packed

‡ Face-Centered Cubic

§ Centerlessly grinding is a method of grinding where the workpiece,

which is supported by a workblade instead of a spindle, is placed

between a regulating wheel and a grinding wheel.

[1] “Precious Metal,” Wikipedia, http://en.wikipedia.org/

[2] Implats, www.implats.co.za

[3] The PGM Database (Platinum Metals Review), www.platinum

metalsreview.com/jmpgm/index.jsp

[4] A.R. Robertson, “Precious Metals,” Metals Handbook, Tenth 

Edition, Volume 2: Properties and Selection: Nonferrous Alloys and 

Special-Purpose Materials, ASM International, 1990, pp. 688-698.

[5] “The Online Materials Information Resource,” MatWeb,

http://www.matweb.com/

[6] Technical & Industrial Platinum, J. Bishop & Company Platinum

Works, 1931.

[7] “Periodic Table of Elements, Corrosion Source, www.corrosion

source.com/handbook/periodic/

[8] International Platinum Association, www.platinuminfo.net

14

techsolutions solutions 4

Mr. John C. Keefe is a Senior Engineer with Alion Science and Technology. He holds a BS in Industrial Engineering from Purdue 

University and an MS in Industrial Engineering from Lehigh University. Previously he worked as the Manager of Manufacturing 

Engineering at Johnson Matthey (Precious Metals Division) in West Chester, PA, where he supervised engineering and fabrication of 

a wide range of products made from precious metals and their alloys. His career focus has been on manufacturing processes, machine

tool selection and engineering education. He has been a college instructor for more than 20 years.
http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 15

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