Advanced Nano Tungsten Powder Manufacturing Scheme

China is a large tungsten-producing country, with more than 20,000 tons of crude tungsten products exported every year. 50% of the tungsten used by the world's major industrial countries is supplied by China. The output of pure tungsten metal products in China is about 1,000-1,200 tons, and the output is also in the forefront of the world. However, in terms of production technology and intellectual property rights of high-quality tungsten materials, China's quantity is rare.

With the development of new and high technology, the requirement for pure tungsten and its alloy materials is getting higher and higher. Whether tungsten wire, plate, foil or other alloy materials based on tungsten (such as tungsten-copper electrical alloy, Tungsten-Nickel-Iron high specific gravity alloy, etc.) are required to have uniform structure, fine grain size and good plasticity. In application, the fineness of high-grade nano tungsten powder determines the powder metallurgy process and material properties of tungsten products, and nano-scale super-fine tungsten powder is becoming popular.

The preparation of 1kg advanced nano tungsten powder should complete the following steps:
1.A high concentration of ammonium tungstate solution of 3.6 litres was obtained. The WO₃ content of the solution was 350g/ liter. At the air jet pressure 2.5MPa, the jet speed was 650m s-1, the hot air temperature was 250 degrees, the countercurrent hot air was dried, the supersonic spray heat conversion method was first made into nanometer grade WO₃ powder. 1.26kg nanometer WO₃ powders were prepared by spraying angle of nozzle a=45 degrees and focal length F=13mm at 280ml/flow rate. The average particle size of WO₃ powders was less than 50nm.

2. Preparation of loosely porous blue tungsten powder by reduction with H₂
A loosely porous blue tungsten powder with an average particle size of less than 40 nm was prepared by reduction in a stainless steel tube reduction furnace at 420 ℃, with a flow rate of 20 ml/cm².min in H₂ gas cross section, holding for 80 minutes.

3. Crushing Blue Tungsten Particles by Ultra-high Speed Interlayer Shear Crusher
After initial mixing according to the ratio of blue tungsten to industrial alcohol to phenolic resin=100:500:3, the mixture is put into the ultra-high speed interlaminar shear crusher and sheared at 20 000 rpm and 40 rpm/kg. During the shearing process, the slurry is introduced into the high-speed 6000 rpm/cyclone classifier to separate the large particles continuously and return to the shearing machine for further shearing. The time is still 40 minutes/kg as originally set by the shearing machine, no longer increasing. The sheared nano blue tungsten slurry is transferred to the next process.

4. Continuous High Speed Centrifugal Separation
The nano-blue-tungsten suspension slurry after shear crushing and cyclone grading is introduced into a continuous high-speed centrifugal separator from the pipeline. The nano blue tungsten powder is separated from industrial alcohol by continuous centrifugation. The separated industrial alcohol is clear and transparent, but contains phenolic resin, which can be reused. Blue-tungsten powder block is taken out and natural wind is used. After drying, turn to the low temperature H2 reduction process of exhaust and drainage.

5. Preparation of nano-tungsten powder by low-temperature H₂ reduction of exhaust and drainage:
In the stainless steel single tube reduction furnace with two ends feeding into the H2 mid-section air extraction and drainage, the flow rate of H2 section is 30ml/cm².min at 700 ℃, holding for 90 minutes. The dew point at the inlet of H₂ gas is -40 C. After reduction, 1 kg nano-tungsten powder was immediately sifted through 15 micron screen with power frequency N₂ gas flow vibration screen. After sieving, a small amount of acetone-oleic acid solution was injected into tungsten powder to prevent spontaneous combustion. The average particle size of tungsten powder is less than 80 nm.

6. Processing procedure before leaving factory
If as the first product, it needs to be processed before leaving the factory, that is to say, industrial alcohol is added according to the quality ratio of nano-tungsten powder to industrial alcohol = 1:5. Bridged aggregates are broken in high-speed interlaminar shearing machine, and large particles are separated and returned by high-speed hydrocyclone fine classifier to continue shearing. Fine nano-tungsten powder suspension slurry was centrifuged by continuous high-speed centrifuge, ethanol was recovered, nano-tungsten powder was taken out, dried, and screened by power frequency N₂ air-flow vibration screen at 15 micron to obtain 10 kg nano-tungsten powder. Attention should be paid to the timely injection of a small amount of pyruvate-oleic acid solution into tungsten powder to prevent the spontaneous combustion of tungsten powder.

7. Performance testing
BET fineness, XRD phase composition detection and X-ray small angle fineness analysis were carried out. The nano-tungsten powder with an average particle size of less than 80 nm was prepared by the above process.

8.Vacuum packaging. After qualified products are vacuum packaged.

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