Method of preparing raw material powder for permanent magnets superior in moldability

摘要

The present invention is directed to provide a method of preparing a raw material powder for permanent magnets superior in moldability, especially in moldability and productivity of bonded magnets. The method comprises subjecting an acicular iron powder having an aspect ratio of not smaller than 5:1 to heating at 800 DEG -900 DEG C. in fluidized state with a gas stream containing no oxygen until the acicular iron powder is transformed into a columnar shape iron powder having an aspect ratio of not larger than 3:1, a die-like shape iron powder or a spherical shape iron powder. The acicular iron powder may contain or may be attached by such a component effective for improving magnetic properties as a rare earth element metal, a rare earth element metal oxide, boron, cobalt and nickel.