Tungsten as a refractory metal

Wolfram (W) (aka tungsten) (Wolframium) - a chemical element of the VI group of the periodic system, atomic number - 74, atomic weight - 183.85. The name derives from “Wolf” (German for “wolf”) and “Rahm” (German for “whipped cream”)(“wolfish foam”). It is a light-grey metal with the highest refractoriness. It is stable outside under standard temperatures. The main minerals are wolframite and scheelite. Wolfram is a component of heatproof extra-hard steels (instrumental, high-speed and alloys (pobedit, stellite etc.); pure wolfram is used in electrical engineering (filament lamps) and electronic engineering (cathodes and anodes of electronic devices).

Wolfram was discovered by Carl Scheele - famous Swedish chemist. He was a druggist and performed many wonderful studies at his mini-lab. He had discovered oxygen, chlorine, barium and manganese. Not long before his death in 1781 Scheele who by that time had become a member of Swedish Academy of Sciences found that tungsten mineral (that was later called “scheelite”) is a salt of an unknown acid. Two years later brothers Elhuyar, Spanish chemists who were working under Scheele’s management, extracted a new element from this mineral called “wolfram”. A century later it made an industrial revolution.

Among the most common industrial grades WCh, WA, WM, WT, WI, WL, WR should be mentioned. There is pure wolfram, wolfram with additives and alloys of wolfram with other metals.

• WCh - pure wolfram without additives.
• WА - contains a silica alkaline and aluminium additives.
• WМ - contains silica alkaline and thorium additive.
• WТ - contains thorium oxide.
• WI - contains yttrium oxide.
• WL - contains lanthanum oxide.
• WR - alloy of wolfram and rhenium.

Wolfram is the basis of hard alloys and many heat-proof alloys. It is included into wear-resistant alloys and instrument steels. Tungsten and its alloys are used for making air engines components, filaments and components of vacuum-tube devices. Also due to high density this metal is used for making counterweights, shells, bullets and superspeed gyrorotors for stabilizing the flight of ballistic missile (up to 180,000 rpm).

Wolframate monocrystals are used as scintillation detectors of X-ray radiation and other ionizing radiation in nuclear physics and nuclear medicine. Wolfram ditelluride WTe₂ is applied for transforming heat energy into electrical (thermo-emf - about 57 mkW/К). It should be mentioned that wolfram electrodes are used for argon-arc welding.

The compounds of this metal have a wide range of applications. E.g., wolfram carbide-based hard alloys and composites are used for mechanical processing of metals and non-metallic construction materials in machine engineering (turning, milling, shaping, chiseling), well drilling and in mine-extraction industry. Wolfram sulphide WS₂ is applied as high-temperature (up to 500 °C) lubricant. Tungsten trioxide WO₃ is used for producing solid electrolyte for high-temperature heating elements. Also the compounds of this metal are used in paint and coatings industry and textile industry so as a catalyst and pigment for organic synthesis.

There is wide range of industrial products made of this refractory materials. Wolfram electrode, wire, wolfram powder, billet, sheet are the most widely used ones.

Electrodes are nonconsumable and are used for welding non-ferrous metals, high-alloy steels and materials with different chemical composition. They provide high weld durability. Heatersand filament lamps coils are made of wolfram wire. Thermocouple wire made of W-Re alloy are used for producing thermocouples used for measuring high temperatures. Wolfram powder serves as the basis of many heatproof steels and alloys so as hard alloys. E.g., WC8 hard alloy is based on this powder.