Abstract
In the metal injection molding process, fluidity of the compound with metal powder and binder is very important factor for molding without defects. In this paper, the effects of molding condisions (injection temperature and rate) on the moldability and the mechanical properties of compacts have been investigated by means of flow test and tensile test. The compound consisted of a carbonyl iron powder and a multi-component wax-polymer binder. Two different types of the binder were used for this study, one was APP-binder (consisted of 20% Atactic polypropylene) and the other was IPP-binder (20% Isotactic polypropylene). The results were summarized as follows:
1) The compound with APP-binder gave the good moldability, because its fluidity showed gradual change in the relation between temperature and viscosity.
2) When the low injection rate was adopted at low barrel temperature which the compound showed high viscosity, flowmark type of the defect appeared on the surface of green compacts. On the other hand, when the high injection rate was adopted at high barrel temperature which the compound showed low viscosity, segregation of the binder was observed in the green compacts. Such molding conditions were detrimental to the mechanical properties of sintered compacts.
3) The combination process with thermal and solvent debinding produced a shortening the binder removal time and preventing the distortion.
