Synthesis of Homogeneous Coarse Grain Tungsten Carbide

Coarse grained tungsten carbide has many advantages, such as good crystalline property, few structural defects, large subgrain size, high microhardness, small strain and plasticity. It can meet the needs of cemented carbide for mining, petroleum and heavy machinery industries. The key point of preparing high performance coarse grained cemented carbide is coarse-grained, homogeneous and well crystallized tungsten carbide powder.

Some scholars invented a new carbonization method which is different from the traditional one. Its main technical content is to increase the particle size of tungsten powder artificially by controlling the gas flow in the process of tungsten hydrogen reduction. The main steps are as follows:

The blue tungsten oxide powder with a Fsss size of 20 micron m is used as raw material, and the raw material is about 6Kg per boat. The temperature of the reduction furnace was raised to 1000 C, and the steam and hydrogen were sent into the furnace. The PH₂O in the furnace was controlled to 0.45. Then it is pushed into the canoe to reduce about 15h, and the coarse grain tungsten powder is obtained by screening the oxide skin after the material is out. The grain size of Fsss is about 21 um. The grain of the coarse grain tungsten powder is very coarse, it is more uniform, the fine powder is very few, and the crystal of the particle is good.

The obtained coarse grained tungsten powder is carbonized according to a known method, with a carbon content of 6.15%, and then carbonized into a carbonization furnace at a temperature of 2300 ℃ for a carbonization time of about 2 hours. The carbonized atmosphere is hydrogen. When the temperature of the furnace is reduced to the discharging temperature, the coarse grain tungsten carbide mass is broken at 1: 1, and the coarse grain tungsten carbide powder is obtained after sieving. The grain size of the coarse grain tungsten carbide powder is about 23.2 m, and the tungsten carbide powder particles are dense, smooth and well crystallized.

The preparation method of coarse grain tungsten carbide powder with coarse grain, high purity, good crystallinity, less structural defects, the subgrain size thick, high hardness, low micro strain until a series of advantages, the coarse grain tungsten carbide cobalt metal and 9.5% in wet grinding mill powder after 15 hours (material: ball = 1: 2), the weight ratio of 1450 ℃ to obtain vacuum sintering, the hardness of alloy HRA is 86, the porosity in ISO 4505 is A02B00, a standard coarse grained cemented carbide.

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