Ultrafine tungsten powder is superior to common coarse grain material in mechanical, therefore, the mechanical properties, physical properties and chemical properties are better than those of ordinary coarse-grained materials.
However, the preparation of ultrafine tungsten powder is more stringent than ordinary tungsten powder, not only have better quality raw materials, but also more suitable methods and equipment are required.
Since 1950s, a great deal of research work has been done on tungsten smelting industry both at home and abroad, and many years of systematic research have been carried out on the preparation of ultrafine tungsten powder, and some effective methods have been developed. Hydrogen reduction is the main method of preparing ultrafine tungsten powder. It is simple, advanced, reasonable, stable and reliable, low cost and so on.
With the development of tungsten powder manufacturing, great progress has been made in the selection of tungsten oxide raw materials, from the early tungstic acid and yellow tungsten into blue tungsten and purple tungsten as the main material. The structure, composition and physicochemical properties of the raw material have great influence on the particle size and uniformity of tungsten powder.
The hydrogen reduction process of tungsten oxide is a rather complicated physical and chemical process, including chemical transformation, phase change process, solid phase diffusion and chemical vapor migration.
Tungsten trioxide hydrogen reduction reaction can be described as the following equation:
The equation may seem simple, but the actual operation is a complex process, the process parameters of each link, such as reduction temperature, material thickness, hydrogen flow and ventilation direction are connected, the interaction of different parameters will lead to different results, a little deviation could affect the particle size of tungsten powder.
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