Tungstène

 Tungsten is a chemical element of the periodic table with symbol W (from German Wolfram) and atomic number 74. Tungsten is a steel gray to white, hard metal that has the highest melting point of all metals. It does not react with oxygen, nor with acids and bases. Tungsten is found in many minerals such as wolframite and scheelite. In its pure form, it is mainly used in electrical applications, but in the form of compounds or alloys it has many applications, such as, for example, the production of tools requiring great hardness (drills, abrasive powders, etc.). Tungsten is found in wolframite which is an iron manganese tungstate (FeWO4 / MnWO4), scheelite (calcium tungstate, CaWO4), ferberite and hübnerite. Important deposits of these minerals are found in Bolivia, California, China, Colorado US, Portugal, Russia, and South Korea. China produces 75% of the world's supply. The metal is produced commercially by reduction of tungsten oxide with hydrogen or carbon.

Notable features

Pure tungsten is a hard metal ranging in color from steel gray to pewter white. It can be cut with a hacksaw when it is very pure, but it is brittle and difficult to work when it is impure, and it is normally worked by forging, extruding, or stretching. This element has the highest melting point (3422 ° C) of all metals, the lowest vapor pressure and the greatest tensile strength of all metals at a temperature above 1650 ° C. Its corrosion resistance is excellent and it can only be slightly attacked by mineral acids. Metallic tungsten forms a protective oxide layer when exposed to air. When added in small quantities to steel alloys, it increases the hardness thereof.

Applications

Tungsten has a large number of uses, the most common being in the form of tungsten carbide (W2C, WC), which is used in the manufacture of wearing parts in metallurgy, mining and petroleum industries. Tungsten is used in the manufacture of filaments for light bulbs and television sets, as well as in that of electrodes, the very fine filaments that can be produced with this metal having a very high melting point.

Other uses:

See Ferrite
See Inconel
See Molybdenum
See Nickel and nickel alloys
See Nimonic
Cutting and machining of Tungsten by waterjet cutting