Influence of Compacting Pressure Conditions on Reduction in Coercive Force of Hard-Ferrite Powders

摘要

It is known that decrease in coercive force of hard-ferrite powders occurs during its milling and compacting processes. The purpose of this study is to elucidate the mechanism of this phenomenon. Strontium (Sr) ferrite powders were compacted by cold closed-die compaction or cold isostatic pressing process (CIP). In addition, Sr-ferrite powder with induced larger shear stress and strain by a mechanofusion (MF) mill was treated by wet-type CIP. The magnetic properties of the formed powders were measured as a function of the compacting pressure. The experimental result suggests that the decrease of coercive force in Sr-ferrite powder is due to surface damage caused by mutual contacts of the powder particles in the forming process.