Development of a high flowable segregation-free iron based powder mix with wax lubricant

Adhesive forces of the segregation-free iron based powder mixes, which consist of liquid bridge force, electrostatic force and van der Waals force were calculated and the absorption isotherm of water vapor on the segregation-free iron based powder mixes, were measured. The result indicated that the van der Waals force between binder on iron particles and lubricant particles and that between lubricant particles were main forces that determine the flowability of segregation-free iron based powder mix in the relative humidity atmosphere less than 91%. A new high flowable segregation-free iron-based powder mix with wax lubricant, CLEAN MIX (KWAX-B) has been developed by means of developing a new lubricant system to decrease the van der Waals forces related to lubricant powders. It showed a better flowability than that of a conventional one. Furthermore lubricant was hardly adhered to inner parts of screw conveyer during transportation. The powder characteristics, such as compressibility, rattler value and ejection force of CLEAN MIX (KWAX-B), and the mechanical properties, such as tensile strength, Charpy impact value and dimensional change during sinering the compact were almost the equal to those of the conventional segregation-free iron based powder mix with wax lubricant.