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The Swedish tungsten of tungsten is the meaning of tung stone (sten). A new element discovered by the Swedish chemist CWscheele from scheelite in 1781. The German Wolfram of tungsten is a compound of wolf and rahm. Because the tin ore containing tungsten, tungsten smelting process into the slag, reducing the yield of tin, as seems to be the wolf swallowed. From 1738 to 1927, successively by Spain, France, the United States, the German scientist preparing tungsten oxide, tungsten steel, tungsten and tungsten carbide hard alloy. Since the beginning of the 20th century, China has been mining tungsten ore. Since the founding of New China, the smelting and processing industry of tungsten has been greatly developed.
Tungsten properties
The melting point of tungsten is high, and the vapor pressure is still very high at a high temperature of 2000-2500 °C. Tungsten has high hardness, high density and good high temperature strength. At room temperature, tungsten is stable in air, and it begins to lose its luster at 400 ° C. The surface forms a blue-black dense tungsten oxide protective film. At 740 ° C, tungsten trioxide is converted from a triclinic system to a tetragonal system, and the protective film is destroyed. Tungsten is oxidized to tungsten dioxide in water vapor above 600 °C. Tungsten is not easily eroded by acid, alkali solution and aqua regia at normal temperature, but is dissolved in a mixed acid of concentrated nitric acid and hydrofluoric acid. Tungsten can be rapidly corroded by oxidizing molten salts such as sodium nitrate. Tungsten reacts with fluorine at room temperature, and tungsten reacts with chlorine, bromine , iodine , carbon monoxide, carbon dioxide, and sulfur at high temperatures, but does not react with hydrogen.
Tungsten resources
At present, there are more than 20 kinds of tungsten minerals and tungsten-containing minerals. Among them, minerals with industrial value include: wolframite and scheelite. The reserves of tungsten in China were 5.298 million tons in 1993, and the output of tungsten concentrate was 44,400 tons. China's tungsten reserves account for more than half of the world's total reserves, mainly in Hunan, Jiangxi, Guangdong and Fujian provinces.
Preparation of tungsten
The smelting process of tungsten includes steps such as decomposition of concentrate, purification of tungsten compound, preparation of tungsten powder and compact tungsten.
Use of tungsten
Most of tungsten is used to produce cemented carbide and tungsten iron . The heat-resistant and wear-resistant alloy composed of tungsten and chromium , molybdenum and cobalt is used for making tools, metal surface hardening materials, gas turbine blades and combustion tubes. Tungsten with tantalum, niobium, molybdenum and other refractory alloy composition. Tungsten copper and tungsten silver alloys are used as electrical contact materials. A high-density tungsten- nickel- copper alloy is used as a radiation protection shield. Wires, rods, sheets, etc. of metal tungsten are used to make electric bulbs, components of the tubes, and electrodes for arc welding. Tungsten powder can be sintered into filters of various porosity. Some compounds of tungsten can be used as fluorescent agents, pigments, dyes, and used in tanning and making fireproof fabrics.