Influence of Compacting Pressure Conditions on Reduction in Coercive Force of Hard-Ferrite Powder in the Compacting Processes

It is well known fact that decrease in the coercive force of hard-ferrite powder occurs during its pulverizing and compacting processes. This study aims to elucidate the mechanism of this phenomenon. For this purpose, a strontium ferrite powder was compacted by a dry die compaction or a dry cold isostatic pressing (CIP) process. In addition, a wet CIP compaction was conducted for the powder preliminarily pulverized in a mechanofusion (MF) mill, which could introduce immediately larger shear stresses and strains into the particles of the powder. The magnetic properties of these compacted powders were measured as a function of the compacting pressure.The experiments result suggests that decrease in the coercive force of the powder is caused by the internal strain in its particles due to solid contacts between them in the compacting process and the degree of the decrease is hardly affected by the utilized compacting process, namely, the dry die compaction, or the dry CIP compaction.