Sintering Tungsten Boat

Sintering wolfram boat is to firing anhydrous wolframic acid to produce tungsten powder, which is an important carrier for making it. Or loading ammonium paratungstate (APT) in firing W-boat to make wolfram powder, the APT is white crystal, which include schistose and acicular, it is applied in the manufacturing process of tungsten metal powder by anhydrous wolframic acid or blue tungsten oxide.

Sintering tungsten boat is mainly used in the production of tungsten powder. Burning ammonium paratungstate into yellow tungsten oxide or blue tungsten oxide, and then make wolfram powder in hydrogen. During the manufacturing process, tungsten oxide should be placed in a W-boat and then put in the reduction furnace. After recycling the hydrogen, remove the carrier. Fritting is divided into three stages, namely the low temperature burn-in step, the medium temperature firing step and keeping warm in a high temperature. In the low-temperature burn-in step is mainly to volatilize the gas and moisture content which is adsorbed in wolfram boat. Anhydrous wolframic acid is a raw material of wolfram powder.

Process for preparing tungsten powder can be divided into two stages. The first procedure is that the  anhydrous wolframic acid is reduced to tungsten dioxide at a temperature of 500 ℃ -700 ℃. The second procedure is that tungsten dioxide is reverted to the wolfram powder under the temperature of 700 ℃ -900 ℃. Purity, particle size, size distribution and other properties of the reduction of W-powder, which primarily rely on the reduction process. When you restore a wolfram powder in a tube furnace, temperature of reduction, charging capacity of tungsten oxide of W-boat, moving speed of W-boat, the flow rate of hydrogen and moisture content of hydrogen content are the main factors to influence the speed of reduction. Particle size of wolfram powder will become thicken as the temperature rises.

While firing, sintering tungsten boat can remove a portion of the harmful impurities, such as sulfur, potassium, sodium and others. This type of W-boat reduces the adverse effects of harmful ingredients (water, oxygen, nitrogen) of the product under vacuum fritting. It is in favor of eliminating the adsorbed gas and the residual gas of the pores which can promote post- fritting shrinkage. However, due to the high temperature, fritting stove would emit large amounts of waste heat.

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