Introduction of Products


Heavy Alloy is a tungsten-group sintered alloy consisting of tungsten and a binder phase with nickel, copper, iron, etc. It is used broadly as various kinds of weight because of its high density originated from main component tungsten and its superior machinability to pure tungsten.

Heavy Alloy is also used as radiation shielding material because of its excellent radiation shielding effect realized by its high density. Recently, due to environmental requirements, Heavy Alloy has attracted attention as replacement for lead which has been used for this application.

Heavy Alloy has other applications as appropriate material for die-cast mold parts, semiconductor parts, machine parts, various kinds of electrodes, weight, barrel of dart shaft, and shielding material. All values are central value.

* HAC2 is highly recommended as standard material.


Nippon Tungsten introduces a high-density tungsten alloy "Heavy Alloy" commercialized based on our powder metallurgical technology.
Tungsten has the highest fusing point 3380C in all metals, and considerably higher density 19.3g/cm3; used broadly as a filament of various lamps and electron tubes, heater element, charging and discharging electrode material, and so on. On the other hand, it has difficulties to machine and is also very liable to oxidize. Heavy Alloy overcomes those difficulties with keeping the characteristics of tungsten; expanding its applications to various fields.

2.What is Heavy Alloy?

Heavy Alloy is a tungsten-group sintered alloy consisting tungsten and binder phase with nickel, copper, iron, etc. Its material characteristics are shown in Table-1, and its internal texture, Photo-2.
Typical material characteristics of Heavy Alloy are following.
▪ High density
▪ Excellent radiation shielding effect
▪ Superior machinability to tungsten
▪ High mechanical strength
▪ Low thermal expansion and high thermal conductance
▪ Excellent oxidation resistance (HAX1)
Table 1 Material Characteristic of Heavy Alloy Products
Electric Conductivity(IACS%)2319---
Deflective Strength(MPa)15001300200017001800
Tensile Strength(MPa)550600700750750
Young's Modulus(GPa)320300380350370
Coefficient of Linear Expansion(x10-6)
Thermal Conductivity(W/m•K)125120959095
Magnetism NonNonLittle MagneticLittle Magnetic-
Magnetic Susceptibility(cgs)0.00010.00010.5631.34-
Magnetic Permeability(cgs)--1.562.34-

Product Application

Thanks to the above characteristics, Heavy Alloy is used in various fields. For example, because of high density and good machinability, it is used broadly as the raw material for weight. Because of high density, it has excellent radiation shielding effect and used as shielding material in X-ray equipment for medical and industrial use. In the application as weight or shielding material, Heavy Alloy has gotten attention as a substitute for lead, which has been used till present but has become a controversial issue in recent years for environmental problems.
Moreover, thanks to its low thermal expansion, excellent mechanical property at high temperature and oxidation resistance, Heavy Alloy is used as the raw material for die-cast mold parts for casting aluminum and copper alloys, and semiconductor parts. As electrode material, it is used for a wire chuck electrode for welding solder-plated copper wire, realizing a much longer life than that of conventional copper alloy electrode.

Radiation Shielding Effect

On the radiation shielding effect of Heavy Alloy, we examined a comparative evaluation with lead. Fig.1 shows the attenuation rate of γ-ray (Co60) against the change in thickness of Heavy Alloy and lead. The γ-ray (Co60) used for the evaluation this time is that eradiated from relatively a high energy zone, which becomes an issue in the case of nuclear power station.
This evaluation proves that Heavy Alloy of about 3mm or 7mm thickness has the radiation shielding effect equivalent to lead of about 4.5mm or 10mm thickness respectively. Consequently, Heavy Alloy, compared with lead, has 1.5 times shielding effect against γ-ray (Co60).

Oxidation Resistance

Tungsten is fundamentally a very oxidizable metal. It generates a very thin oxide layer on its surface even at a room temperature and starts oxidizing at about 400C. Heavy Alloy, though consisting mainly of tungsten, has some degree of oxidation resistance and, among Heavy Alloy series, HAX1 (W-Ni-Fe-α) has excellent resistance to oxidation. Fig.2 is the comparison of oxidation increment of HAC1, HAF1 and HAX1 under oxidizing condition (700C x 3hr in air), showing that HAX1 has excellent oxidation resistance. Thanks to this oxidation resistance, Heavy Alloy has been achieving satisfactory results in application to die-cast mold parts and semiconductor parts, which are used under high temperature.


Tungsten is a material having difficulty in machining, especially cutting, so its machining is limited to grinding by use of a diamond wheel, etc. or electro-discharge machining. Although Heavy Alloy mainly consists of tungsten, one of the hardest materials, it can be machined with a cemented carbide tool. According to the application, Heavy Alloy can be machined into various shapes by milling, end-milling, tapping, etc. as shown in Photos 3 and 4.

Possible Product Size of Heavy Alloy

Product's NameShapePossible Maximum Size
Actual Maximum Size(mm)
Heavy Alloymajor diameter:Φ400
thickness:maximum weight
major diameter:250
diagonal length:400
thickness:maximum weight
diagonal length:280
Heavy Alloy Sleevemajor diameter:Φ400
(wall thickness 5mm over)
length:maximum weight50kg/piece
Possible Maximum Size depends on material and shape. If you need our Heavy Alloy products, please contact us.


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Nippon Tungsten Co., Ltd.
2-8, Minoshima 1-chome, Hakata-ku, Fukuoka, 812-8538 Japan
Phone TEL +81-942-50-0053 / FAX +81-942-50-0054
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