What specific problems should be paid attention to in the metal powder injection molding process

What specific problems should be paid attention to in the metal powder injection molding process

In the process of processing many parts, even after several years in this industry, we may not be able to understand all the processes. Here we share with you some specific problems of this technology, mainly including:

1. How to choose metal powder

Metal powder injection molding process: for the sintering density of pf-3f, pf - 5th floor, pf-10f and pf-15f at different sintering temperatures. It can be seen that within a certain temperature range, the higher the sintering temperature, the greater the sintering density, the less the change, with the sintering temperature. In a certain range, the larger the size of the powder, the larger the sintering density. Spherical powder is beneficial to improve the vibration density, bearing capacity and sintering density.

2. Ratio of metal powder to binder

The viscosity increases with the increase of solid content. When the solid content reaches 62%, the viscosity increases sharply after injection, making the solid content limit (^ 62% higher). When the binder is not enough, there is a gap between the two will affect the powder product. The mechanical strength of the binder is too high, and the solid content is too low, which will affect the degreasing and sintering shrinkage.

3. How to choose the design of gate and overflow hole

The door should be at a higher position in space, thus reducing the possibility of friction feeding of melt in the mold, reducing the injection pressure and reducing the deformation of the product. In addition, the design of flash point is also very important. The flash point is used for loading in the process of cold injection molding to ensure product consistency.

4. C, N and O sintered 316L

C In the sintering process, N and O will have a bad effect on the sintered 316L. Carbon chromium has a strong affinity. It replaces Cr23C6 and reduces the content of solid solution chromium at the grain boundary. The formation of chromium-poor zone is in the form of nitrogen in supersaturated solid solution stainless steel, and it is cooled in the form of Cr2N at the grain boundary, thus reducing the MIM corrosion resistance of the product; The Cr2O3 oxide film formed by oxygen and chromium has poor wettability with liquid, and the effect of liquid flow hinders the densification process.

5. How to select sintering atmosphere

This is because in Ar atmosphere, the low dew point protects the surface of the powder from oxidation, and the removal of C and O powder exceeds 900 ℃. In vacuum environment, the gas gap is easier to be eliminated, which promotes the densification process; In nitrogen atmosphere, the dew point temperature is not low enough, resulting in the formation of oxide film powder, which is not conducive to the formation of sintered parts, and hinders the diffusion of atoms.