Tungsten carbide powder is the main raw material of producing cemented carbide. Its chemical formula is WC, called as Wolfram Carbide. It is black hexagonal crystals, with metallic luster, the hardness is similar to diamond, is a good conductor of electricity and heat.
Tungsten carbide does not dissolve in water, hydrochloric acid and sulfuric acid, soluble in nitric acid and hydrofluoric acid mixture. Pure tungsten carbide is fragile, if mixed with a small amount of titanium, cobalt and other metals can be reduced brittleness.
Tungsten carbide is largely used for high-speed cutting tools, furnace structural materials, jet engine parts, metal ceramic materials, resistance heating elements and so on. For the manufacture of cutting tools, wear parts, copper, cobalt, bismuth and other metal melting crucible, wear-resisting semiconductor thin film. As superhard cutting tool materials, wear-resistant materials, it can form a solid solution with various carbides. It also can be used as additives of NbC-C and TaC-C ternary carbides, not only reduced the sintering temperature, but also maintaining excellent performance, can be used as aerospace materials.
From metal powder supplier we known that tungsten carbide was produced in two ways, one is used tungsten metal powder and charcoal as raw material, dry mixed the average particle diameter of 3 ~ 5¼m tungsten powder and the same amount of substance carbon black with a ball mill, after thorough mixing, compression molding and put into a graphite plate, then heated to 1400 ~ 1700 in a graphite resistance furnace or induction furnace, controlled at 1550 ~ 1650 is best. In a hydrogen stream, originally generated W2C, continuing react at a high temperature to generate WC. Or first thermal decomposition W(CO)6 in 650 ~ 1000, CO atmosphere to obtain tungsten powder, then react with carbon monoxide at 1150 to get WC, above this temperature can be generated W2C.
Another is WO3 hydrogenation obtained tungsten powder (average particle size is 3 ~ 5¼m). Then pressure molding the tungsten powder and carbon black at the equimolar mixture (dry mixing in a ball mill for 10h) under a pressure of about 1t/cm2. Put the press molding material into the graphite disk or block crucible, heated with the graphite resistance furnace or induction furnace in a hydrogen gas stream to 1400 ~ 1700 (preferably 1550 ~ 1650), make it carburized and generated WC. The reaction was started from the tungsten grains around, because at the beginning of the reaction will generate W2C, since the reaction is not complete, in addition to WC, it still remaining unreacted W and intermediates W2C, so it must be heated to the high temperatures.
Tungsten dust can cause peribronchitis, peribronchiolar, blocking bronchiolitis and atrophic emphysema. Tungsten carbide may cause lung lymphoid tissue cell proliferative response, and gradually emergence sclerosis. Vascular wall was thickening and homogenization. People exposure to tungsten carbide dust in work will cause gastrointestinal disorders, kidney suffered irritation, upper respiratory tract appeared catarrhal inflammation. The maximum allowable concentration of tungsten carbide is 6mg/m3.
Staff should use the satisfactory gas mask, dust-proof clothing, gloves, glasses. Prevent dust leakage in all stages of production. Workers should do pre-employment physical examination, periodic inspection once every year. When the upper respiratory tract appears obvious symptoms must temporarily transfer work, do not contact with tungsten. If show up lung hardening or respiratory function disorders should be removed from the work. Tungsten carbide should be stored in a cool, dry depot, pay attention to check whether the packaging containers in good condition during transport, prevent rain and sunlight exposure.
Article Source:http://www.mhcmp.com
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