Liquid Form Synthesis of Tungsten Carbide

Tungsten carbide is the main raw material for the production of hard alloy. The process of producing alloy powder in the tungsten production and processing enterprises is basically the combination of tungsten carbide powder and cobalt powder through mechanical mixing, and the uniformity of the alloy powder is not ideal. It has a great influence on the pressing of the subsequent cemented carbide. Some scholars have tried to pre - configure the alloy powder in the liquid state and then reduce the alloy powder.

(1)Preparing 270-330g / L ammonium tungstate solution, 800-850g / L cobalt nitrate solution and 100-130g / L chromium nitrate solution in advance;

(2)Ammonium tungstate solution preset ammonia content, control ammonium tungstate solution ammonia concentration between 50 ~ 70g / L, ammonia ammonium tungstate solution will be added to the hot reaction kettle, while stirring slowly added to the prepared cobalt nitrate solution, concentrated by heating evaporation, volatile ammonia until the pH value dropped to between 8.5 to 9.0, then add the prepared chromium nitrate solution, continue heating until the pH dropped to between 7.0 and 7.5, stop heating.

(3)The co-precipitated crystals are prepared by vacuum solid-liquid separation of the mixed solution after cooling, and the co-precipitated crystals are dried in an infrared oven and then placed in a calciner at a temperature of 700-750 ℃, namely tungsten cobalt chromium compound metal oxide;

(4)With a flow rate of 80 m³ / h and the dew point less than -80 ℃ hydrogen as the reducing agent, the tungsten cobalt chromium complex metal oxide at 710~840 ℃ temperature range of low temperature reduction, the reduction time is 4~5 hours, reduction of tungsten cobalt chromium element fully mixed tungsten cobalt chromium metal powder;

(5)Reduction of tungsten cobalt chromium metal powder after reduction of air with carbon dioxide gas, cryogenic cooling for 7~9 hours at a temperature of 20~24 ℃, the cooling process of tungsten cobalt chromium metal powder reduction will ensure that surface passivation, tungsten cobalt chromium metal reduction powder is oxidized in the carbon transfer and process; Then the required carbon was added to the tungsten cobalt chromium metal reduction powder after cooling, and then milled and milled for 3~5 hours to make the tungsten cobalt chromium metal reduction powder fully mixed with carbon. Then the required carbon was added to the tungsten cobalt chromium metal reduction powder after cooling, and then milled and milled for 3~5 hours to make the tungsten cobalt chromium metal reduction powder fully mixed with carbon.

(6)The tungsten cobalt chromium metal reduction powder after carbon distribution is placed on high temperature continuous molybdenum wire furnace and carbonized for 3~4 hours at 1100~1150 degree furnace temperature. Tungsten carbide cobalt chromium metal composite powder is obtained, that is, the mixture of tungsten carbide, cobalt carbide and chromium carbide.

(7)The carbonized composite powder after ball milling sieve 80 mesh, then the airflow again broken sieve 40 mesh, the finished product is prepared; the steps for the removal of coarse particles in the composite powder and agglomerate, the final product has high purity, combined carbon content is high, uniform distribution of particle size was complete.

With the conventional alloy powder production compared to the production methods and technology ideas have different requirements, the prepared tungsten carbide cobalt chromium metal composite powder, the combination of high purity, high carbon content, good uniformity and normal distribution of particle size, complete development, the main content of chemical components of good uniformity, excellent performance.

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