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.
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.
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.
- Its very high melting point makes it particularly suitable for space applications and those requiring the use of very high temperatures.
- The hardness and density of this metal make it ideal for making alloys of metals used in weaponry, heat sinks, as well as as a weight and counterweight.
- It was used, for example, by the Israeli army in the Gaza Strip in the fall of 2006 .
- Wear parts used, for example in high speed tools, often use alloys of tungsten and steel up to 18% tungsten.
- Tungsten compounds are used as catalyst, inorganic pigment.
- Tungsten disulfide is used as a stable lubricant above 500 ° C.
- Sodium tungstate (CAS: [10213-10-2]) is part of Folin Denis' reagent.
- Since its coefficient of expansion is equivalent to that of borosilicate glass, it is used to make glass-to-metal bonds.
- Superalloys containing tungsten are used to make turbine blades, steel tools, as well as plating.
- It is used as a refractory electrode in TIG welding.
- The arcing contacts of high voltage circuit breakers are also partially made of tungsten in order to withstand the high temperature of an electric arc. DIME (Dense Inert Metal Explosive), a new very powerful weaponry to destroy a human target while causing damage in a very limited radius of a few meters.