MIM Sintering Principle And Process

Since it has been more than 1000 years ago, sintering technology has been applied to many industries, from the well-known ceramic industry to the powder injection molding industry.

The degreased part is placed in a high-temperature, high-pressure controlled furnace. The part is slowly heated under the protection of a gas to remove any residual binder.

Once the binder has been completely removed, the part is heated to such a high temperature that the gaps between the particles disappear due to the fusion of the particles.

The part shrinks directionally to its design size and transforms into a dense solid. For most materials, typical sintering densities are theoretically greater than 97%. The high sintering density makes the product properties similar to those of wrought materials.

The sintering process is mainly divided into three stages: Initial stage, intermediate stage and final stage

After acid debinding, most of the binder (POM) is removed from the raw embryo injected by the injection machine, and a small amount of high-temperature binder is still retained to maintain the shape of the product. These residual high-temperature binders are removed by heating them to 600 degrees in the sintering furnace for decomposition reaction. This stage is different from acid degreasing, which is called thermal degreasing stage, also known as pre-sintering.

Initial stage: the metal powder particles in the completely degreased embryo form a sintering neck from the contact point and grow up

Intermediate stage: the sintering neck grows, and the gap between metal powder particles gradually decreases, forming a pore network connected with grain boundaries

Final stage: pores between particles eventually become closed and independent pores, and products are formed

After the sintering stage, the gap between particles is greatly reduced, so the product volume shrinks and the strength is improved. The advantages of powder injection molding are reflected in this: because the product's embryo is formed by injection molding after the metal powder and binder are uniformly mixed in a certain proportion, the components of each part of the embryo are relatively uniform, so that during sintering, the product can be guaranteed to contract in all directions, and the shape and dimensional accuracy of the product are well guaranteed, which is also a feature of MIM.

With the innovation and progress of technology and technology, the material processing technology is developing in the direction of high performance, low cost, short process and near final molding. There are many new preparation technologies that integrate design, preparation and processing, such as metal powder injection molding technology.