Tungsten Metal

Pure tungsten metal and heavy metal tungsten alloy start with the same foundation, but they are very different with very different applications. Pure tungsten metal features the highest melting point and tensile strength of all metals, while heavy metal tungsten alloy has a high density comparable only to gold and platinum.

Pure tungsten metal has the highest melting point of all metals and, at temperatures greater than 1650°C, the highest tensile strength. Its thermal expansion rate is like that of borosilicate glass and silicon.

Tungsten’s good thermal and electrical conductivity make it an excellent choice for microprocessor applications. It is also used in electron emitters, heater coils, cathode ray tubes, electrical contacts, and a variety of high-heat applications such as vacuum furnaces and fusion reactor chambers.

Pure tungsten metal (99.95%) is available in all product formats including foil, coil, sheet, and plate. The exotic material can be machined, formed, and ground with care due to the relatively brittle nature prone to edge chipping and abrasive properties of the material on tooling. All pure tungsten products start with pressed and sintered powder, which is then processed further using conventional mill techniques to final format.

1. Tungsten metal foil (less than 0.005”), sheet (from 0.005” to 0.187”), and plate are produced to ASTM B760, latest revision.
2. Material can be provided in the hot or cold-rolled condition with stress-relieved condition as an option. Most foil and sheets are provided in the cold-rolled, stress-relieved condition.
3. Thickness and flatness tolerances are per ASTM B760. Tolerances for foil are to be agreed upon as these are not specified in ASTM B760.
4. Machined and fabricated parts made from pure tungsten metal can be provided with supplied drawings.

Heavy metal alloys are pseudo-alloys of tungsten with a nickel-iron or nickel-copper matrix. The matrix is determined by the final specification properties. They are produced by powder metal pressing and sintering processes. Heavy tungsten alloys have a high density of 17-19 g/cm³. Comparable densities are only reached by gold or platinum.

These tungsten alloys are used as mass balancing weights and attenuators in aircraft construction, in motors and power trains, as oscillating weights and centrifugal weights in machines and equipment construction, and in medical technology for both protection from and focusing of ionizing radiation in x-ray cancer therapy machines and gamma radiation measuring devices.

Typically, there is no further processing after sintering before machining unless special mechanical properties are required. Depending on required dimensional tolerances, blanks/rods are produced slightly oversized to ensure cleanup after machining. Bars/rods are usually provided with a “ROTF” (roughly oversize to finish) dimension – about 0.060” extra stock or can be provided with a ground surface to -0/+.005” tolerance.

1. Heavy metal tungsten alloy materials are produced per ASTM B777 or AMS 7725.
2. This material is supplied in four different classes depending on the required density. Although a “Nominal” tungsten content is mentioned, there are no actual chemical composition requirements in these specifications. For special applications where non-magnetic properties are needed, the customer should specify that the material needs to be free from magnetic response and order a “non-magnetic” version (not available in class 4). The “non-magnetic” versions are blended to be free of Iron. If a specific chemistry is required, then this must be agreed upon prior to fabrication.
   

   Class	Nominal Tungsten Weight %	Density (g/cc)
   1	90	16.85-17.30
   2	92.5	17.15-17.85
   3	95	17.75-18.35
   4	97	18.25-18.85

    

   • If no class is specified, class 1 material is typically produced.
   • We can provide materials meeting all DFARS (Defense Federal Acquisition Regulation Supplement) requirements for domestic tungsten alloy production when required.
   • Leading Edge can provide machined and fabricated finished parts with supplied drawings.