Magnetic properties of Nd-Fe-B magnets sintered using granulated powders by spray drying method

摘要

In recent years the demand for smaller and thinner Nd-Fe-B permanent magnets has increasedsignificantly. The poor flowability of the alloy powder when feeding and compacting has howeverbeen an obstacle to their fabrication. In order to improve the powder characteristics, Nd-Fe-B alloypowder was granulated by a spray drying method using a polyvinyl-alcohol (PVA) binder (0.1-0.5wt-%). The granulated powder exhibited higher flowability with increased PVA content. The greenbodies compacted under a magnetic field of 0.88 MA m{sup}-1 were debindered by heating inH{sub}2 and then sintered in a vacuum. The magnetic properties of a sintered anisotropic magnetprepared by adding 0.20 wt-%PVA are close to those obtained if the spray drying process is not used.The conditions required for the spray drying of Nd-Fe-B alloy powder have been investigated.