Industrially tungsten is a very important metal having wide applications. This is due to many outstanding physical properties. Among all the metals, tungsten has the highest melting point and the lowest vapor pressure. Also at high temperatures it has the highest tensile strength. The metal has an excellent resistance to corrosion and attack by mineral acids. Also it has a thermal expansion comparable to that of borosilicate glass.

Industrial Applications and Uses

Since 1923, cemented carbides and hardmetal have represented the major use of tungsten (60%). They are prepared by melting together graphite and tungsten metal in an electric-arc furnace. The reaction leads to the formation of a eutectic mixture of WC and W2C. Owing to its brittleness, the cooled material is ground into fine particles and added to molten-cobalt bath. Tungsten is useful for glass-to-metal seals because the linear thermal expansion of the metal is about the same as that of borosilicate glass.

Tungsten and its alloys are used extensively for filaments for electric lamps and electron and television tubes (CRTV) and in metal evaporation work. Other applications include electrical contact points for car distributors, X-ray targets, windings and heating elements for electrical furnaces, missile and hightemperature applications, as alloying element in high-speed-tool steels (10%), and many other alloys. The two carbides (i.e., WC and W2C) are important to the metal-working, mining, and petroleum industries.

Calcium and magnesium tungstates are widely used in fluorescent lighting. Tungsten salts are used in the chemical and tanning industries (10%). Tungsten chalcogenide WS2 such as MoS2 is a dry, high-temperature lubricant, stable up to 500°C. Tungsten bronzes (NaWO3) and other tungsten compounds are used in paints.