Effects of Metal Powders and Manufacturing Methods on MIM

MIM is a new metal forming technology combining traditional powder metallurgy and modern plastic injection molding technology. MIM process has strict standards on the choice of metal powder. This is because the shape of powder particles decide the quality of products.

Good metal feed can form a good product, and good powder will be a good metal feed, which means that the metal powder affects the performance of MIM products. So what is a good metal powder?

After years of production practice and industry experts, the theoretical study found that the more granular, uniform particles, close to the spherical powder particles more suitable for the manufacture of feed. The feed made of such powder is good for process liquidity and conducive to the successful completion of the entire MIM process. What is more, it is easy to debonding, during which the blank in the sintering process of shrink uniformly with small degree.

But in the actual production, due to cost, technology and other factors,metal powder raw materials which used to produce the feed are not in “perfect state". Even the impeccable powdery raw materials that we consider perfect will inevitably affect the effect of the MIM forming process because the shape of the parts is not easily maintained. For example, the steel metal powder which be used in MIM process although is spherical,and particle size meet the technical requirements, because of the small bite force between the particles, the product shape is difficult to maintain.

So if we want to get stable performance and shape of the products, we need to think about other ways. The current metal powder used in manufacture of metal feed is generally divided into two types: aerosolized powder and water atomized powder. These two kinds of powder shape properties are different, with only one of which cannot get a good feed.

Adding water atomized powder to aerosolized powder can improve the shape maintaining ability and decrease the anisotropy shrinkage of the injection molding. If the natural slope angle of the mixed powder is small, the interaction between the particles is small, and the anisotropy shrinkage of the component after sintering is large. Samples with more aerosolized powder are easy to collapse after debonding. Using water atomized powder can maintain the shape without damaging its mechanical properties. The irregular shape of the particles affects the sinterability of the mixed powder, and the use of a large proportion of the water atomized powder promotes densification.

In summary, the impact of metal powder particle shape in the MIM process is rooted. To choose the metal feed made of appropriate metal powder is essential to the formation of high-quality MIM products.