In 1923, cemented carbide was invented by German Krupp company, named widia, which means it is as hard as diamond. Cemented carbide was the hardest man-made material known at that time. Its invention marked the second revolution of metal cutting tools. The main component of cemented carbide is WC + CO (tungsten carbide + cobalt), in which the content of WC is about 88% - 94%, which is the hard phase, and co accounts for 6% - 12%, which is the bonding phase. According to different grades, cemented carbide also adds rare metal elements such as titanium, Ti, niobium, Nb, tantalum and TA. Carbides composed of these elements, such as tic, can significantly improve the hardness of cemented carbide; NBC and TAC can significantly improve their toughness and high temperature resistance.
Tungsten, the main raw material of cemented carbide, is known as "industrial teeth". Tungsten can withstand high temperature, so tungsten alloy is widely used in machinery and military industry. For example, tungsten alloy will be used in the firing tube of gun and gun. The projectiles of armor piercing projectiles are made of high-density alloy steel, tungsten carbide and other materials much harder than tank armor. Tungsten alloy has no radioactivity and its chemical properties are very stable. It will not oxidize even at a high temperature above 1000 ℃, and its hardness will not decrease significantly. This is very beneficial to the high-temperature metal of armor piercing projectile. If a country does not have tungsten, there will be a great lack of metal processing capacity under the current technical conditions, which will directly lead to the paralysis of the machinery industry. Tungsten is widely used in national defense industry, aerospace and information industry. It is called strategic metal.
Tungsten is a rare and non renewable metal in the world. It is only distributed in a few countries such as China, Canada, Russia, the United States and Vietnam. Among them, China has the largest reserves, mainly distributed in Jiangxi, Hunan and other provinces. In recent years, China has accounted for 85% of the global supply. According to written records, in the 1980s, China's reserves accounted for about 70% of the world's reserves, and after nearly 30 years of mining and development, this figure has changed to 35%.
