What on earth is Tungsten?
Name: Tungsten
Symbol: W
Atomic number: 74
Atomic weight: 183.84 (1)
Standard state: solid at 298 K
CAS Registry ID: 7440-33-7
Group in periodic table: 6
Group name: (none)
Period in periodic table: 6
Block in periodic table: d-block
Colour: greyish white, lustrous
Classification: Metallic
Properties:
Tungsten, also known as wolfram, is a chemical element with the chemical symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten directly translatable to heavy stone, though the name is volfram in Swedish to distinguish it from Scheelite, in Swedish alternatively named tungsten.
A hard, rare 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 elements. 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, though still hard, is more ductile, and can be cut with a hard-steel hacksaw.
Tungsten's many alloys have numerous applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), electrodes in TIG welding, 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 and archaea. It is the heaviest element known to be used by any living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life
PRIMARY USES OF TUNGSTEN
Cemented carbides, also called hardmetals, are the most important usage of tungsten today. The main constituent is tungsten monocarbide (WC), which has hardness close to diamond. Hardmetal tools are the workhorses for the shaping of metals, alloys, wood, composites, plastics and ceramics, as well as for the mining and construction industries.
Tungsten remains an important partner for tool steels, high speed steels, stellites and creep-resistant steels and alloys.
Tungsten mill products are either tungsten metal products, such as lighting filaments, electrodes, electrical and electronic contacts, wires, sheets, rods etc or tungsten alloys.
Other applications include a widespread variety of chemical uses.
The extraction process
Powdered tungsten(VI) oxide is heated to temperatures in the range 550 - 850°C in a stream of hydrogen.
An excess of hydrogen is used, and this carries away the steam produced during the reaction. The hydrogen is dried and recycled.
Great care obviously has to be taken to keep the whole system free of air to avoid explosion risks with the hydrogen at these high temperatures.