Cyclic Oxidation Method Helps Tungsten Powder Particle Size Rebalance
Tungsten powder is the basic raw material for making cemented carbide.
Most of the cemented carbides in the market do not have much demand for the size of tungsten powder, but they have strict requirements for the particle size uniformity of tungsten powder.
A new method of ammonium tungstate cyclic oxidation reduction method proposed in recent years for producing submicron tungsten powder, it is mainly through a number of ammonium tungstate - tungsten oxide circulation change, submicron tungsten powder and ultimately the average particle size. Therefore, we can also try to use circulating oxidation reduction method to help the common tungsten powder to achieve particle size rebalancing.
It is necessary to prepare blue tungsten for reduction of tungsten powder because of the preparation of ordinary particle grade tungsten powder. The general process of ammonium tungstate cycle oxidation reduction method is: the special pure ammonium paratungstate in argon to slowly raise the temperature rise to 600 °C, holding 10 min, to obtain blue tungsten → with the resulting purple tungsten in the first reduction of hydrogen, preparation of tungsten powder → tungsten powder in the air slowly heated to 500 °C for the first oxidation, when the temperature reached 500 °C for 10 min, to obtain tungsten trioxide → tungsten oxide in hydrogen for the second time to prepare Tungsten powder, end the process, get tungsten powder.
The tungsten powder was tested with tungsten powder with a particle size of 3~10 and a specific particle size of 0.180 m2/g and a specific surface area of 83.86% m, the main reason is that the composition of blue tungsten is not a single phase, according to the oxidation - reduction deposition mechanism can be seen, blue tungsten in the reduction process is not synchronized to carry out, therefore, the tungsten particle size distribution is very uneven after the first reduction of blue tungsten. When the first reduction of blue tungsten tungsten powder is oxidized into WO3, and then restore, because the tungsten oxide particle size distribution is uniform, then the reduction process of tungsten trioxide is almost simultaneous, therefore, the particle size distribution of tungsten powder tends to be homogenized. In short, the first reduction process and can not draw tungsten powder with uniform particle size, this should not be too tangled, directly and then melted down a consolidation reduction effect on it.
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