Analysis of process of metal injection molding of stainless steel powder using a permeable die

In order to obtain sound green compacts, which are necessary for producing quality sintered products by metal injection molding (MIM), it is important to control the filling behavior of the slurry in the mold cavity. Pressurized air, which exists near the final filled-up area, exerts a large effect on both the now dynamics of the slurry and the properties of the green compact. A permeable die has a lot of microscopic pore channels in the mold cavity. Use of a permeable die is a useful technique to enhance the slurry flowability. In this study, the now behavior and the properties of green and sintered compacts of stainless steel were investigated in several injection experiments using both ordinary and permeable dies. A numerical simulation was also conducted. The results showed that the molding speed and the quality of the green and sintered compacts are better when the permeable die is employed rather than the ordinary die. Furthermore, the backpressure of the air and the volume of the exhausted air were calculated by the FAN method combined with backpressure analysis. The results of these analyses will serve as useful information for designing compacts of uniform quality with no defects.