Importance

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Abstract

A powder for forming a R--Fe--B bonded magnet, wherein an R compound, such as an R oxide, an R carbide, an R nitride or an R hydride, which is contained in a raw material powder such as a super rapidly cooled powder or a hydrogen treated powder (HDDR powder) and reacts with water vapor to change into R(OH).sub.3, has been converted to a R hydroxide R(OH).sub.3 being stable in the air by subjecting the raw material powder to a heat treatment in an atmosphere of a pressured water vapor. The powder for forming an R--Fe--B bonded magnet is free from the generation of a white powder in the surface of or inside a bonded magnet formed from the powder and accordingly, is free from the occurrence or cracking, chipping, swelling or the like in the bonded magnet caused by volume expansion of a white powder. Thus, the above powder can be used for preparing an R--Fe--B bonded magnet which is free from the white powder which has been observed in a conventional R--Fe--B bonded magnet in the use for a long period of time and is reduced in the occurrence of defects such as cracking, chipping, swelling and the like.

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First Claim