Refining Coarse Grained Tungsten Carbide with Tungsten Iron

Coarse-grained tungsten carbide is widely used in mining tools, stamping dies, oil drilling and production, hard surface materials and other fields because of its advantages of less structural defects, high microhardness and small micro-stress. At present, the main method of producing coarse-grained tungsten carbide is to obtain coarse-grained tungsten powder first, and then to obtain coarse-grained tungsten carbide powder by further high-temperature carbonization.

In order to solve the problem of expansion of solid-solid reaction volume and slow diffusion of carbon in solid phase leading to particle bursting, a method of preparing coarse-grained tungsten carbide from ferrotungsten has been reported.

The tungsten iron, iron and carbon are mixed in a crucible according to the above proportion and heated in a reaction furnace. The temperature is controlled at 1550-1700 ℃ for more than 20 minutes, and then cooled to room temperature within 2-24 hours to obtain the alloy block. Tungsten carbide is further grown; coarse-grained tungsten carbide (single crystal tungsten carbide particles) is obtained by taking out alloy blocks (metal phase), crushing, acid leaching, rinsing with water, removing impurities and drying.

As a kind of alloy agent for steelmaking, tungsten iron has been relatively mature. At present, the pyrometallurgical process of ferrotungsten is adopted to treat tungsten ore, which mainly uses tungsten concentrate as raw material and electric furnace as the main production equipment. There are three production methods: agglomeration, iron extraction and aluminothermic process. The main components of the product are tungsten and iron, in which the tungsten content is 70-80%, and a small amount of manganese, silicon, carbon, phosphorus, sulfur and other impurities.

The melting point of ferrotungsten can be reduced by using molten iron as the dissolving agent. During the process of melting at 1550-1700 ℃, tungsten and carbon form tungsten carbide grains, small grains dissolve and large grains grow up continuously. Finally, large single crystal tungsten carbide can be obtained by crushing and pickling to remove impurities. The tungsten carbide powder with different particle size distribution can be directly applied to the production of coarse grained cemented carbide. The tungsten carbide powder is characterized by high purity, complete carbonization and coarse and complete grain.

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