Advanced Nano Tungsten Powder Manufacturing Scheme

With the development of high technology, the requirement for pure tungsten and its alloy materials is 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. It also promotes the quality requirement of original tungsten powder. In the application, the particle size of advanced nano tungsten powder determines the powder metallurgy process and material properties of tungsten products. Nano-scale ultra-fine tungsten powder is becoming popular.

The preparation of 1kg 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, and 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 C, 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 mass 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. In the shearing process, the slurry is introduced into the high speed 6000 rpm/cyclone classifier to separate large particles continuously, and then returns to the shearing machine to continue 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 low-temperature H₂ reduction process of exhaust and drainage type.

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 ℃. 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, the industrial alcohol is added according to the mass 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 particle size 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. Ten kg nano tungsten powder was obtained. Attention should be paid to timely injecting a small amount of pyruvate-oleic acid solution into tungsten powder to prevent the spontaneous combustion of tungsten powder.

7. Performance testing
BET particle size, XRD phase composition detection and X-ray small angle particle size 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.

• < Prev
• Next >