Tungsten

From Wikipedia

Tungsten ( /ˈtʌŋstən/), also known as wolfram ( /ˈwʊlfrəm/ WOOL-frəm), is a chemical element with the chemical symbol W and atomic number 74.

A steel-gray metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Also remarkable is its high density of 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead. Tungsten with minor amounts of impurities is often brittle and hard, making it difficult to work. However, very pure tungsten is more ductile, and can be cut with a hacksaw.

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), and superalloys. Tungsten's hardness and high density give it military applications in penetrating projectiles. Tungsten compounds are most often used industrially as catalysts.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules, where it is used in a few species of bacteria. It is the heaviest element known to be used by any living organism. However, tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life.

Applications
Approximately half of the tungsten is consumed for the production of hard materials (tungsten carbide), with the remaining major use being its use in alloys and steels. Less than 10% is used in chemical compounds.

Hard materials
Tungsten is mainly used in the production of hard materials based on tungsten carbide, one of the hardest carbides, with a melting point of 2770 °C. WC is an efficient electrical conductor, but W2C is less so. WC is used to make wear-resistant abrasives and cutters and knives for drills, circular saws, milling and turning tools used by the metalworking, woodworking, mining, petroleum and construction industries and accounts for about 60% of current tungsten consumption.

Alloys
The hardness and density of tungsten are applied in obtaining heavy metal alloys. A good example is high speed steel, which can contain as much as 18% tungsten. Tungsten's high melting point makes tungsten a good material for applications like rocket nozzles, for example in the UGM-27 Polaris Submarine-launched ballistic missile. Superalloys containing tungsten, such as Hastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings.

Armaments
Tungsten, usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium, in applications where uranium's additional pyrophoric properties are not required (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in cannon shells, grenades and missiles, to create supersonic shrapnel. Tungsten has also been used in Dense Inert Metal Explosives, which use it as dense powder to reduce collateral damage while increasing the lethality of explosives within a small radius.