Tungsten Oxide

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 mater

Hydrogen reduction is the main method for preparing ultrafine tungsten powder. It is a rather complicated physical and chemical process, including chemical transformation, phase change process, solid phase diffusion and chemical vapor transfer. In W-O-H there are 6 solidification phase, which are: tungsten trioxide (WO 3 ), beta tungsten oxide (WO 2.9 , W 20 O 58 , blue tungsten) gamma tungsten oxide (WO 2.72 , W 18 O 49 , Purple Tungsten) two tungsten oxide (WO 2 ), -W alpha and beta -W. Therefore, the process of hydrogen reduction reaction of tungsten oxide is complex, and different reduction processes will occur with the change of temperature and humidity: In a high temperature and a humid reducing atmosphere, the reduction proceeds in distinct stages ( WO 3  → WO 2.9  → WO 2.72  → WO 2 → W ); In low temperature and dry hydrogen, it is possible to reduce tungsten oxide to tungsten powder directly from high valence tungsten oxide ( WO 2.9  → W，WO 2.72  → W ), the process is

The hydrogen reduction process of tungsten oxide, is a very complex physical and chemical processes, including chemical conversion, phase transformation, solid diffusion and so on. The process generally is: tungsten oxide, hydrogen reduction, sifting, blending, tungsten powder. Different tungsten oxide reduction process of reaction pathways, the reaction speed is different, in general, the reduction reaction pathway and to avoid the simple single reaction generated in the process of WO 2  is beneficial to preparing fine tungsten powder uniformly. That is to say, the tungsten powder obtained by route WO 2.9  → W or WO 2.72  → W would be more satisfactory. Hydrogen reduction of tungsten oxide is usually carried out in a multiple tube furnace or a rotary furnace. Multiple tube reduction furnace has 3 to 5 containers used for loading, use artificial way in accordance with the order of loading and unloading material, excessive hydrogen or against the tungsten material movemen

Tungsten oxide hydrogen reduction process is generally carried out in a multiple tube furnace, in the tubular reduction furnace, the most used in China are the thirteen tube reduction furnace and the four tube reduction furnace. Four tube reduction furnace is commonly used as a tungsten oxide hydrogen reduction unit, the furnace shell is welded by ordinary steel plates, and the four tubes are placed at the same level on the same hearth. Compared with the old four tube muffle furnace up and down the structure, the temperature uniformity is much better. The automation level of the four tube reduction furnace is higher than the thirteen tube reduction furnace, and it is easier to realize mechanization and electrification, in addition, the capacity of the four tube reduction furnace is large, but the unit energy consumption is lower than the thirteen tube reduction furnace. The furnace temperature of the four tube reduction furnace is between 600 °C and 1000 °C centigrade,