The research of refractory materials in the world has developed from the traditional "high purity, super fine, uniform" to "nano, composite design and integrated manufacturing". Through these advanced technologies, tungsten molybdenum alloy and refractory tungsten alloy materials can not only retain their excellent properties such as high melting point and corrosion resistance, but also greatly improve their comprehensive mechanical properties. The research and application of tungsten, molybdenum and refractory metals lag far behind other metal materials. Therefore, it is our current important task to further optimize and perfect the processing technology of various tungsten alloy materials through technical transformation and according to the requirements of different application fields.
Tungsten alloy has been widely used in aviation/aerospace, military equipment, electronics, medical, chemical, automotive, welding and many other fields due to its comprehensive performance of high density, high strength, low thermal expansion coefficient, corrosion resistance and good machinability.
Its main uses include :(1) cutting, welding tungsten electrodes and coating carbides, such as tungsten carbide. (2) A large number of filament and cathode for electron tubes in the electronics industry, heating elements for high temperature resistance furnaces, such as impact-resistant tungsten wire and composite rare-earth tungsten electrode. (3) armor-piercing bullets, lining plates, etc. It's used in the heat field, even the military.
Improving the plasticity of tungsten and tungsten alloy materials, reducing their plastic-brittle transition temperature, and further improving their high temperature thermal strength have been the focus of research in the field of tungsten alloys. Therefore, the main contents of tungsten research and development are its plastic-brittle transition behavior, high temperature strength characteristics, tungsten electrode welding and composite, and manufacturing process optimization. Technologies developed around these include purification, refinement, toughening, and recombination.
The purification of tungsten begins with the purification of oxides, and the chemical purity of APT is improved by solvent extraction, ion exchange and multiple recrystallization processes. At present, APT with purity above 99.95% and total impurity content less than 100mg/kg can be produced. The purity of tungsten powder is above 99.99%.
The study of tungsten composites mainly includes structure composite, strengthening mechanism composite and microstructure composite (gradient composite). At present, the main research of tungsten copper composite used as tungsten electrode, contact material, welding material and semiconductor components. The molding method of this material is mainly isostatic pressing (CIP). The new and improved process methods include :(1) fiber reinforced method; (2) specific structure method; (3) arc melting method; (4) metal injection molding; (5) Rapid directional solidification method.
