Powder metallurgy(PM) is a kind of metal processing method，uses metal powder as raw material, by pressing and sintering to manufacture various kinds of products.Powder metallurgy technology consists of three main steps: first, the main composition material is made into fine particles of powder; Then fill the powder in the mold, press the mold with a certain pressure to form the required shape and size of green body parts (green body). Finally sinter the green body at a high temperature.
The basic process of powder metallurgy technology
1. The preparation of raw material powder.
The existing milling method can be divided into two categories: mechanical and physical chemistry method. And mechanical method can be divided into: mechanical crushing and atomization method; The physical and chemical method is divided into: the electrochemical corrosion method, reduction method, chemical combination method, vapor deposition method, liquid phase deposition method and electrolysis method.
2. Powder form into the green body as required.The purpose of forming is to get the compact body with a certain shape and size , and make it has a certain density and strength. Forming method is basically divided into extrusion forming and non-pressure moulding. Compression molding is mostly used in extrusion forming.
3. Sintering of the green body.
Sintering is the key step is powder metallurgy. The green body, through sintering has the required final physical and mechanical properties. Sintering is divided into unit system sintering and multicomponent system sintering. For the solid phase sintering of unit system and multiple system, the sintering temperature is lower than the melting point of metal and alloy. For multicomponent system of liquid phase sintering, the sintering temperature is generally lower than the melting point of the refractory compounds, and higher than the melting point of fusible components. In addition to the ordinary sintering, there are apparent sintering, infiltration method, hot pressing method and so on special sintering process.
4. Products post processing.
Processing after sintering, can adopt different ways according to product requirements. Such as finishing, oiled, achining,heat treatment and plating. In addition, in recent years, some new technology such as rolling, forging is used in powder metallurgy post processing and get good results.
