Ultracoarse Tungsten Powder Prepared from Ammonium Paratungstate

The special properties of tungsten determine particle generated from tungsten oxide or ammonium paratungstate by reduction size range generally on the 2~5μm, and difficult to obtain ultracoarse tungsten powder. In this paper, the preparation technology of super coarse tungsten powder with low energy consumption, low hydrogen consumption and short reduction time was put forward using ammonium paratungstate and ammonium paratungstate as raw materials. A method that using ammonium paratungstate made from sodium tungstate and tungstate as precursor to generate ultracoarse tungsten powder with low energy and hydrogen consumption, short reduction time is proposed.

Steps are as follows:
1. Mixing solution of sodium tungstate and tungstate according to molar ratio of 1:40;
2. Heated the solution obtained in step 1 to boiling, and stop when the volume remaining 10% ~ 20%, sent to far-infrared oven for drying at 150℃ for 2 hours, then generate the precursor mixing with ammonium paratungstate and sodium tungstate crystal;
3. Sieving precursor, made the particle at 80 meshes, and then adding fine tungstate powder which take 20% of the precursor, mixed with V type mixer for 2 hours;
4. Restored in a tube reduction furnace in hydrogen; two sets of ultrasonic generator and three air hammer with uniform center spacing are set on the outer side of the furnace tube;  hydrogen section flow for 0.005L/min.cm² and the frequency of ultrasonic generator set for 25-26kHz, pneumatic hammer percussive frequency is 60 times/min, and pneumatic hammers are percussion not at the same time, time for 30min, temperature for 900℃, ultracoarse tungsten powder generated;
5. Ultracoarse tungsten powder cleaning in ultrasonic tank with deionized water, and then filtering, dehydration with industrial alcohol, drying in a vacuum drying oven in 80℃ for I~2 hours, screening, the sieved fine tungsten powder can recycling  as raw material.

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