48 巻 (2001) 10 号 p. 907-914
The present paper describes a new evaluation for ejection behavior in iron powder compacting process and optimum die-wall lubrication conditions. In the new method, ejection force is broken down to static friction force and kinetic friction force, which make it possible to explain ejection behavior more clearly. The incremental rate of kinetic ejection force is more important for surface quality of compacts than the value of static ejection force. Among three lubricants used, zinc stearate showed the highest static ejection force but the lowest incremental rate of kinetic ejection force. It also showed an excellent surface quality of the compacts. Characteristic crystalline structure gave a low shear strength, which contributed to decrease the kinetic friction. In the die-wall lubrication method, the projected area rate of lubricant particles should be 90% or more, therefore, the multiple coating method which is repetition of short time shot is requested.