Yellow tungsten oxide producing tungsten powder is its main application. The common used metods in industry are hydrogen reduction method, carbon reduction method and aluminothermic reducing method. Use hydrogen reducing yellow tungsten oxide is mainly the process of solid-vapor multi phase reaction, equation is: WO3+3H2=W+3H2O
Carbon reducing method and aluminothermic reducing method are solid-solid multi phase reaction, equation is:
2WO3+3C=2W+3CO2 or WO3+3C=W+3CO
Aluminothermic reducing method is using reducing property of aluminum to gain high melting point metal single substance, aluminothermic reaction usually applied to metallurgy high melting point metal, it uses magnesium rod as ignition agent, potassium chloric acid as combustion. Magnesium rod can be burnt in the air, oxygen is used as oxidant agent.
Yellow tungsten oxide reducing is processed in the material boat of the fixed bed furnace with a certain thickness. The diffusion of product vapor through powder layer to the surface of the material layer and the reverse diffusion of the water vapor play an important role in the reduction reaction.
The reduction of the yellow tungsten oxide is mostly carried out in the material boat of the fixed bed furnace with a certain thickness. The reduced water vapor spreads to surface of material layer and its reverse spread play an important role in the reduction reaction rate and its physical properties.
Yellow tungsten oxide grain size and its property has big effect on tungsten powder grain size. Usually calcinating tungstic acid under 700℃, the lower the temperature is, the finer the grain size of yellow tungsten oxide. The obtained tungsten powder grain size is in accordance with YTO.