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(W), also called WOLFRAM, chemical element, a really strong
refractory metal of Group Vib of the periodic table, used in steels
to increase hardness and strength and in lamp filaments.
Tungsten metal was first founded (1783) by the Spanish
chemists and mineralogists Juan Jose and Fausto Elhuyar by
charcoal reduction of the oxide derived from the mineral
wolframite. Earlier (1781) the Swedish chemist Carl Wilhelm
Scheele had discovered tungsten acid in a mineral now known as
scheelite, and his country-man Torbern Bergman had concluded
that a new metal could be prepared from the acid. The name
tungsten and wolfram have been used for the metal since its
discovery, though everywhere ]on Jacob Berzelius' symbol W
prevails. In British and American usage tungsten is preferred; in
Germany and a number of other European countries wolfram is
accepted. |
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Among metals it has the highest melting point, the highest tensile strength at temperatures of more than 1,6500 C (310020 F), and the lowest coefficient of linear thermal expansion (4.43 10-6 per OC at 200 C). Tungsten is ordinarily brittle at room temperature. Pure tungsten can, however, be made ductile by mechanical working at high temperatures and can then be drawn into very fine wire. Tungsten was first commercially employed as a lamp filament material and thereafter used in many electrical and electronic applications. It is used in the form of for very hard and tough dies, tools, gauges, and bits. Much tungsten goes into the production of tungsten steels, and some has been used in the aerospace industry to fabricate rocket-engine nozzle throats and leading-edge reentry surfaces.
