Powder Metallurgy of Material Processes

Powder metallurgy is a process technology that uses metal or metal powder (or a mixture of metal powder and non-metal powder) as raw materials to produce metal materials, composite materials and various types of products by forming and sintering. The powder metallurgy products industry in a broad sense includes iron and stone tools, cemented carbide, magnetic materials and powder metallurgy products. The powder metallurgy products industry in the narrow sense only refers to powder metallurgy products, including powder metallurgy parts (take up a large portion), oil-retaining bearings and metal injection molding products.

Process characteristics of powder metallurgy

1. The density of products is controllable, such as porous materials, high-density materials, etc.;

2. The grains are fine, the microstructure is uniform, and there is no component segregation;

3. It can be near-shaped, and the raw material utilization rate is greater than 95%;

4. There is little cutting, and the cutting process only accounts for40~50%;

5. The material components are controllable, which is conducive to the preparation of composite materials;

6. Preparation of insoluble metals, ceramic materials and nuclear materials.

Basic process flow of powder metallurgy

1. Powdering

Powdering is the process of making raw materials into powder. Commonly used methods of milling are oxide reduction and mechanical methods.

2. Mixing

Mixing is the process of mixing various required powders in a certain proportion and making them uniformly mixed to form the body refuse. There are three types of mixing methods: dry type, semi-dry type and wet type, which are used for different requirements.

3. Forming

Forming is the process of putting a uniformly mixed mixture into a press mold and pressing it into a parison with a certain shape, size and density. The forming method is basically divided into pressure forming and pressureless forming. Compression forming is most widely used in pressure forming.

4. Sintering

Sintering is the key process in the powder metallurgy process. The formed parison is sintered to obtain the required final physical and mechanical properties. Sintering is divided into unary system sintering and polynary system sintering. In addition to ordinary sintering, there are also special sintering processes such as loose sintering, immersion method, and hot pressing method.

5. Post-processing

After sintering, various treatment methods can be adopted according to different product requirements, such as finishing, oil immersion, machining, heat treatment and electroplating. 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 ideal results.

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