Tungsten

Tungsten Facts

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Discovered by J.J. and F. El’huijar in Vergara, Spain in 1783. Tungsten exists in nature as wolframite.

 

(FeMn)WO4 and scheelite (CaWO4). The ore concentrations are fused with NaOH and after water extraction, WO3 is then precipitated with acid and reduced to the metal with H2.

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The metal is still commonly called wolfram and it is from this that the chemical symbol is derived. The ores are generally found in association with those of other refractory metals, such as molybdenum and also tin ores.

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The metals structure is bcc. The bulk metal is lustrous and silvery white and resists attack by oxygen, acids and alkalis – however it does oxidise at high temperatures. It is only attacked slowly by HNO3 & HF. The metal is used extensively in steel alloys in electric lamp and heating filaments and in electric carbides. Tungsten carbides are very hard and are used in cutting tools.

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The tensile strength varies from 150 N/mm2 in the fully annealed condition to over 4500 N/mm2 for fine wire finally cold drawn using diamond dies.

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The most important alloys are the tungsten steels which contain up to 18% of tungsten. Tungsten alloys, which contain chromium and copper are for high speed cutting tools. Electric contacts for switch gears are made from Cu and Ag-W alloys.