The process of metal powder injection molding (MIM) products

The process of metal powder injection molding (MIM) products

Powder+binder → mixing → granulation → injection molding → degreasing (MIM degreasing furnace) → sintering (MIM sintering furnace) → subsequent treatment → forming products. In the process of producing MIM hard alloy parts, improper material selection and operation control at any stage may cause defects in the hard alloy parts. So how to avoid such defects?

1. Powder selection process. In addition to meeting the basic requirements such as particle size distribution and particle size, MIM cemented carbide powder metallurgy also requires high purity of the powder, which cannot be mixed with impurities. If the powder is mixed with sulfur, phosphorus, silicon and other elements, these substances will form pores in the sintering process, causing product defects.

2. The production process of feeding. When mixing hard alloy powder, appropriate binders are required. When mixing, the hard alloy powder should be thoroughly mixed with the binder. The mixing process must strictly control the temperature to avoid the volatilization and uneven distribution of the binder, so that the mixture has good rheological properties and viscosity values after being fed, and to avoid defects in the future.

3. The process of forming green billets. This is also a key link in the production of hard alloy parts. To avoid product defects, it is necessary to pay attention to the reasonable control of mold temperature, feeding amount, injection pressure, holding pressure, holding time, injection speed, etc. during the injection process, which can effectively avoid the occurrence of defects in the injection green.

4. Degreasing process. During the degreasing process of hard alloy billets, if the temperature rise rate of the degreasing furnace is too fast, it will cause cracks and defects in hard alloy parts. The method of gradually increasing temperature can be used for degreasing.

5. Sintering process. The density of hard alloys is high, and during liquid phase sintering, products are prone to deformation due to their own gravity. Appropriate support devices can be used, and materials with similar shrinkage rates can be selected as support plates for larger products. Additionally, the time for liquid phase sintering should be minimized as much as possible.