Basic process of powder metallurgy
1. Preparation of raw material powder. Existing milling methods can be broadly classified into two categories: mechanical methods and physical chemical methods. The mechanical method can be divided into: mechanical pulverization and atomization method; physical chemistry method is further divided into: electrochemical corrosion method, reduction method, chemical law, reduction-chemical law, vapor deposition method, liquid phase deposition method and electrolysis method. Among them, the most widely used methods are reduction, atomization and electrolysis.
2. The powder is formed into a compact of the desired shape. The purpose of the forming is to produce a compact of a certain shape and size and to have a certain density and strength. The molding method is basically divided into press molding and pressureless molding. The most widely used in press molding is compression molding. In addition, 3D printing technology can also be used for the production of embryo fragments.
3. Sintering of the compact. Sintering is a key process in powder metallurgy processes. The formed green compact is sintered to obtain the desired final physical and mechanical properties. Sintering is further divided into unit system sintering and multi-component sintering. For solid phase sintering of unit and multicomponent systems, the sintering temperature is lower than the melting point of the metals and alloys used; for multiphase liquid phase sintering, the sintering temperature is generally lower than the melting point of the refractory component, and higher than the fusible component. Melting point. In addition to ordinary sintering, there are special sintering processes such as loose sintering, melt immersion, and hot pressing.
4, the subsequent processing of the product. The post-sintering treatment can be carried out in various ways depending on the requirements of the product. Such as finishing, oil immersion, machining, heat treatment and plating. In addition, in recent years, some new processes such as rolling and forging have also been applied to the processing of powder metallurgy materials after sintering, and have achieved satisfactory results.