Sodium Doped Yellow Tungsten Oxide Producing Method

Coarse tungsten carbide has good resilience, high hardness, high thermal conductivity, is widely used as mining tools, punching mould, gasoline exploration and hard face material.

At present, main producing method for coarse tungsten carbide is adding alkali metal into APT or yellow tungsten oxide, which is mechanical mixing method. Add certain amount of sodium salt into APT or yellow tungsten oxide. Since adding quantity of sodium salt is very little, uniformity of powder can not be guaranteed. During producing process of tungsten powder there is still problems like uneven grain size, incomplete crystalline which will affect property of tungsten carbide products.

For the present sodium salt doping process, uneven spread of sodium will result in uneven grain size. Researches have been done to produce sodium doped yellow tungsten oxide to improve tungsten powder property. Steps are as follows:

1. Use alkali decomposed tungsten concentrate by ion exchange and molybdenum removing process to produce ammonium tungstate liquid as raw material, ammonium tungstate concentrate is 200~300g/L, Na+ concentrate is 10~40ppm.

2. Add sodium salt before evaporating crystalline, then according to subsequent product requirement, doping amount of sodium compound based on Na/WO3 ratio weight is controlled at 0.05%~0.25%.

3. Evaporating the above mixing liquid, temperature is 80~100℃, stirring speed is 50~200 r/min, pH value is 6.4~7.0.

4. After crystallization process is finished, stop heating and cooling down to 20~50℃. Use vacuum filtration method to filter liquid and dry it. APT doesn’t need to be cleaned. Dry APT we can obtain APT with even sodium content. Or put wet APT in calcinating furnace to calcinate under 680~740℃ to obtain sodium doped yellow tungsten oxide.

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