Spherical Tungsten Powder Production Methods - 2/2

Many spherical tungsten powder manufacture methods have been researched and developed by  advanced technologies to comply with the more strictly usage requirements in different industries. Below are another two tungsten-hydrogen halide reduction methods.

Tungsten powder secondary oxidation and reduction method

Domestic scientists use the secondary oxidation and reduction technology of tungsten powder method. By strictly controlling the reoxidation temperature and oxidation time parameters of the polygonal tungsten powder, the angular and rough parts of the polygonal tungsten powder particles are more active. The preferential partial oxidation is followed by hydrogen reduction, so that the surface of the tungsten powder particles is more round and becomes spherical or quasi-spherical particles. Through fluidized-dynamic suspension sedimentation dry classification method to classify into spherical or quasi-spherical tungsten powder which can satisfy the characteristics of the tantalum tungsten cathode material.

This process can get spherical or quasi-spherical tungsten powder with low cost, while the rate of insufficient spheroidization and low spheroidization is high.

Plasma method

Because the plasma has the characteristics of high temperature, high enthalpy, high chemical reaction activity, reaction atmosphere and controllable reaction temperature, it is very suitable for preparing spherical powder with high purity, small particle size and uniform particle size distribution. In recent years, research on this aspect has seen new progress. For example, MORIYSOHI of Hosei University in Japan conducted research on the production of ultrafine spherical tungsten powder by mixed plasma composed of high-frequency plasma and direct current plasma, and produced spherical tungsten powder having an average particle diameter of 10 nm. In domestic has carried out research on plasma spheroidized tungsten powder, and the spheroidization rate can be almost 100% by controlling the process conditions. 

The advantage of plasma spheroidized tungsten powder is the energy is highly concentrated and the temperature gradient is large. The energy input can be precisely controlled by process parameters, the thermal energy utilization rate is up to 75%. After plasma spheroidization, the fluidity of the tungsten powder is improved, and the bulk density and tap density of the tungsten powder are also improved.

The Institute of Process Engineering of the Chinese Academy of Sciences has a high-frequency thermal plasma device with a power of 30 kW. The device has been used to research spheroidization of a series of powders to obtain spherical powder such as spherical silica, spherical alumina, spherical nickel powder. In addition, the device is used for spheroidizing tungsten powder. In the plasma, the irregular tungsten powder particles are spheroidized by surface melting, and a dense and smooth spherical tungsten powder is obtained.

With the rapid development of 3D printing technology, porous materials, high-density powder coating and injection molding, the demand for high-quality spherical tungsten powder is increasing. The high-quality spherical tungsten powder not only has good fluidity, good sphericity, high bulk density and tap density, but also low oxygen content. In recent years, China's powder metallurgy technology has continued to improve, but there is still a big gap compared with foreign advanced technology. The production technology of high-quality spherical tungsten powder in foreign countries are relatively complete. Domestic technology and process for preparing spherical tungsten powder are on the way of more research and development.

Spherical Tungsten Powder Production Methods - 1/2

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