Preparation of High Quality Submicron Tungsten Powder

Tungsten powder is the main raw material for preparing cemented carbide and many industrial products. Under normal circumstances, tungsten powder can be classified into coarse grain, fine grain, submicron and nano size according to its particle size. Each particle size of tungsten carbide powder has its specific market application.

The key technical specifications of finely grained, submicron, ultrafine or nanocrystalline cemented carbide WC powders are summarized through production practice. The key specifications are purity, granularity and particle size distribution uniformity, and it is clearly stipulated that WC powder is not permitted to have class III.

(1)The preparation of solution: using APT-0 as raw materials at 270~350 ℃ in a muffle furnace rotary furnace in static or dynamic pyrolysis 1~3h, get amorphous dissimilatory ammonium paratungstate (AMT) -based material, the weight loss rate controlled at 7 ~ 8%; with 7mol / L ammonia solution or deionized water was stirred and dissolved 2 ~ 4h, allowed to stand for 30min and filtered, an ammonium tungstate solution was obtained.

(2)Dispersion: add dispersant solution and dispersant in ammonium tungstate solution and stir for 10 ~ 30min; Dispersant is an aqueous solution of low molecular weight ammonium polyacrylate (PAANH₄) in an aqueous system and the dispersant solution is an aqueous solution with a dispersant content of 5 to 10% by weight; Dispersion strengthening agent is methanol, adding dispersant solution is 1 ~ 10% by volume of ammonium tungstate solution, dispersion strengthening agent is added in an amount of 5.0% by volume of ammonium tungstate solution.

(3)Spray drying: The above mentioned dispersion treated ammonium tungstate solution is rapidly crystallized and dried with a spray drying equipment to obtain fine-grained hollow thin spherical spherical ammonium tungstate crystals; The spray drying equipment is a high-speed centrifugal spray equipment. The lining of the spray tower is lined with titanium or lined with polytetrafluoroethylene, the inlet temperature is 250~350 ℃, the outlet temperature is 80~150 ℃, the centrifugal speed is 10000~25000 rev /min.

(4)Pyrolysis: The above ammonium tungstate crystals are pyrolyzed in air or nitrogen in a muffle furnace or in a rotary kiln at 500-600 ℃ for 1-3h to obtain a yellow tungsten oxide precursor; In a nitrogen-hydrogen mixture or hydrogen atmosphere in a muffle furnace static or rotary furnace dynamic 600 ~ 700 ℃ pyrolysis and mild reduction 1 ~ 3h, get blue or purple tungsten oxide precursor.

(5)hydrogen reduction: double boat loading, loading capacity 500~1000 grams / boat, feed in the direction of hydrogen, hydrogen flow rate of 40~45m³/h, hydrogen dew point less than 60 ℃, pushing the boat speed 8 to 12 minutes / boat, by 600 ~ 900 ℃ five hydrogen reduction to sub-micron, narrow particle size distribution of tungsten powder.

The submicron and narrow particle size distribution tungsten powder produced by the above process is uniform in size and fine in structure. It is a powerful guarantee for high quality products, and can be used to produce tungsten products with high performance cemented carbide, tungsten electronic cathode substrate and high homogeneous fine grain tungsten target.

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