Ultra Coarse Tungsten Powder Preparation Process

Tungsten powder can only be produced by powder metallurgy because of its high melting point, that is, tungsten powder can be obtained by reducing tungsten oxide or ammonium paratungstate (APT), and then tungsten and tungsten alloy products can be made. Due to the nature of tungsten itself, the particle size range of tungsten powder obtained by reducing tungsten oxide or ammonium paratungstate is generally 2-5 micron, so it is difficult to obtain ultra coarse tungsten powder.

The traditional method of preparing super-coarse tungsten powder is to reduce tungsten oxide powder by hydrogen in a secondary molybdenum wire furnace at about 1200 ℃. The particle size of tungsten powder can only reach 7-15 micron. The principle of this method is to accelerate the volatile deposition of tungsten oxide by the action of water and tungsten oxide, and obtain coarse tungsten powder. With the progress of technology, people think of using doping to improve the particle size of tungsten powder. For example, some scholars have proposed a method to prepare ultra-coarse tungsten powder, which solves the defects of traditional ultra-coarse tungsten powder preparation process, such as long reduction time, difficult process control, high energy consumption and high cost.

1.The mixed solution of sodium tungstate and ammonium tungstate is prepared according to a certain proportion. The molar ratio of sodium tungstate and ammonium tungstate is between 1:100 and 1:40.

2.The prepared solution is heated to boiling. When the volume evaporates 80%-90%, it stops heating and is sent to far-infrared oven for drying at 120-150 ℃ for 2-10 h. The precursors of ammonium partrungstate and sodium tungstate crystalline mixture are obtained.

3.The precursor was wiped and sifted to make 80 mesh powder, and then the fine tungsten powder, which accounted for 10%-20% of the precursor mass, was added to the powder and mixed for 2 hours with V-type mixer.

4. The super-coarse tungsten powder was obtained by hydrogen reduction in a tubular reduction furnace. The particle size of the super-coarse tungsten powder was 60-150 micron, the reduction temperature was 800-1000 ℃, the reduction time was 1-2 h, and the cross-section flow rate of hydrogen was 0.01-0.1L/min cm².

4.The reduced super-coarse tungsten powder is cleaned with deionized water in ultrasonic tank, filtered, dehydrated with industrial alcohol, then dried in a vacuum drying box at 80 ℃ for 1-2 h, screened and the fine tungsten powder is returned to the raw material for recycling.

The results show that the tungsten powders prepared by the new process are approximately spherical, with good surface gloss, good formability, high purity and coarse particle size. The maximum particle size can reach 150 micron. The production cost is low and the market prospect is broad.

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