Metal powder injection molding is a technology that uses metal powder (or the mixture of metal powder and non-metallic powder) as raw material to produce metal materials, composites and various products after molding and sintering. Metal powder injection molding is similar to ceramic production, so a series of new metal powder injection molding technologies can also be used to prepare ceramic materials. Due to the advantages of metal powder injection molding technology, it has become the key to solve the problem of new materials and plays an important role in the development of new materials.
In metal injection molding factory, there are many factors that affect the properties of sintered body in metal injection molding, namely powder characteristics, molding and sintering conditions. The elements of sintering conditions include heating rate, sintering temperature and time, cooling speed, sintering atmosphere and pressure conditions.
Sintering temperature and time will affect the porosity, density, strength and hardness of sintered body. High sintering temperature and long heating time will reduce product performance and even lead to product scorching defects. At the same time, low sintering temperature or long heating time may reduce the performance due to the metal sintering process.
The sintering atmosphere usually used for metal powder injection molding is to reduce atmosphere, vacuum, hydrogen and so on. Sintering atmosphere directly affects the properties of sintered body. Sintering in a reducing atmosphere can prevent block burning and allow the reduction of surface oxides. For example, iron and copper-based products are usually decomposed with gas or ammonia, while cemented carbide and stainless steel are usually decomposed with pure hydrogen. Active metal or refractory metal, cemented carbide containing Tic alloy and stainless steel can be used for vacuum sintering. Vacuum sintering can avoid harmful components. Metal powder injection molding sintering method liquid phase sintering when there are more than two components in the powder block, it may be sintered at the melting point of the components, and a small amount of liquid phase will be produced in the powder block.
In the sintering process, pressure sintering exerts pressure on the powder to promote the densification process. Sometimes sintering and heat pressing are synonymous, but heat pressing refers to the process of directly obtaining products after powder forming and sintering. At the same time, while improving the properties of sintered body, some physical or chemical measures are adopted to significantly reduce the sintering temperature and time.
When the powder is introduced into the compaction process, spark sintering generates electric arc between the powder particles through constant current and pulse power, then start the sintering process. During the sintering process, metal injection molding gradually increases the pressure on the workpiece, so as to combine the molding and sintering of the two technologies.
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