Tungsten (W) (Wolframium) is a chemical element of group VI of the periodic system, atomic number 74, atomic mass 183.85. . Light gray metal, the most refractory of metals. It resembles steel. Due to the possession of rather unique properties,
sufficiently high density, which is equivalent to 19.3 g / cm3;
high melting point, component 34220С;
sufficient electrical resistance - 5.5 μOhm * cm;
a normal indicator of the coefficient of the linear expansion parameter, equal to 4.32;
the highest among all metals boiling temperature equal to 55550С;
low evaporation rate, even despite temperatures exceeding 2000C;
relatively low electrical conductivity. However, this does not prevent tungsten from remaining a good conductor.
All this makes tungsten a very strong metal, which is not amenable to mechanical damage. But the presence of such unique properties does not exclude the presence of disadvantages that tungsten also has. These include:
high fragility when exposed to very low temperatures;
high density, which complicates the process of its processing;
low acid resistance at low temperatures.
Tungsten - the basis of hard alloys and many heat-resistant alloys, is part of wear-resistant alloys and tool steels. From it and alloys are made: parts of aircraft engines, incandescent filaments and parts in electric vacuum devices. Also, due to its high density, this metal is used for counterweights, artillery shells, bullets and ultra-high-speed gyro rotors to stabilize the flight of ballistic missiles (up to 180 thousand rpm).
A wide range of applications are compounds of this metal. For example, hard alloys and composite materials based on WC tungsten carbide are used for the mechanical processing of metals and nonmetallic structural materials in mechanical engineering (turning, milling, planing, chiselling), drilling, and mining. Tungsten sulfide WS2 is used as a high-temperature (up to 500 ° C) lubricant. In the production of solid electrolyte for high-temperature fuel cells, tungsten trioxide WO3 is used. Compounds of this metal are also used in the paint and varnish, textile industry and as a catalyst and pigment in organic synthesis.
The industry produces a wide variety of products from this refractory material. The most common are tungsten electrodes, wire, tungsten powder, stick, sheet.