Metal powder particle and manufacturing methods influencing on MIM technology

The MIM is a new metal forming process combining traditional powder metallurgy and the modern plastic injection forming technology. Metal injection molding process has strict standards for the selection of the metal powder, this is because the shape of the powder particles can control the quality of products.

Good metal feed can form good product, and good metal powder can make good metal feeding. This means that the stand or fall of metal powder affects the performance of MIM products. Then what makes a good metal powder? Industry after many years of production practice and the study of the theory of the industry experts found that the particle size smaller, uniform particles, near spherical powder particles, the more suitable for feeding. Such powder feeding has good liquidity in subsequent products in the process of forming, is conducive to the smooth completion of the MIM process, as well as easy debinding, after debinding blank in the process of sintering has uniform shrinkage smaller level.

But in actual production, because of the influence of various factors such as cost, technology, used to produce metal powder feeding raw materials are not "perfect". Even the powder materials we think impeccable are inevitable because the shape of the forming parts is not easy to maintain and affect the effect of the forming process of MIM. Such as metal injection molding process used steel powder, although it is spherical, particle size also conform to the requirements of the process, but because the interparticle bite force is small, product shape is very difficult to maintain.

So people thought, will it be a little bit better for changing the spherical powder into irregular shape? Facts have proven that this change although increased bite force between particles, but can not make metal feed still maintain good liquidity under heating condition, abate the uniformity of the products, seriously influenced the MIM parts debonding and sintering process, so that influence the final performance and rate of finish products.

Obviously, to obtain products with stable performance and shape still need to seek better measures. the current use of metal powder is generally divided into two kinds: Aerosol powder and water atomized powder. These two kinds of powder properties are widely different, with either alone can't get a good feed.

Aerosol powder add water atomized powder can maintain ability to improve the shape of the injection molding parts, reduce the anisotropic shrinkage. If mixed powder natural slope Angle is small, the description of the interaction between particles is small, the parts made by anisotropic shrinkage is larger after sintering. Aerosol powder contains large sample, and is easy to collapse after debonding. Use water atomized powder, can keep the shape and not damage its mechanical properties. Irregular shape particles affect the mixed powder sintering, using larger proportion of water atomized powder can promote the densification.

To sum up, the influence of the metal powder particle shape on the MIM technology is root and eventually, choose the appropriate metal powder suitable metal feed is important for forming quality of MIM products.