Tungsten is a heavy metal that can be classified as a refractory metal, i.e., one with a high melting point. Refractory metals can be useful for their strength at high temperatures and their resistance to corrosion. Tungsten is difficult to melt, so commercial non-alloyed tungsten is produced by powder-metallurgy methods.Alloys containing about 85 to 95 percent tungsten by weight can be produced by liquid-phase sintering compacts of tungsten powder with nickel-copper, iron-nickel, iron-copper, or nickel-cobalt-molybdenum binders. In compact forms, these tungsten alloys can be machined by turning, drilling, boring, milling, and shaping; however, they cannot be wrought at any temperature and therefore are not available in mill forms. Heavy tungsten alloys can be used in aircraft applications, by the military in its weapons, in X-ray shielding, and even some consumer goods applications.Light bulb filaments are usually made of unalloyed tungsten. Cutting tools are often made of tungsten carbide. Finally, tungsten is also an element of some of the modern super alloys.
