Toda Kogyo Corporation

Nobuhiro Katayama

Koichiro Morimoto

Hirofumi Kawasaki

Kuniyoshi Shigeoka

Shohei Kaneko

A process for producing R-T-B-based rare earth magnet powder having excellent coercive force and high remanent flux density. A process for producing R-T-B-based rare earth magnet powder by HDDR treatment, in which a raw material alloy for the R-T-B-based rare earth magnet powder includes R (wherein R represents at least one rare earth element including Y), T (wherein T represents Fe, or Fe and Co) and B (wherein B represents boron), and has a composition including R in an amount of between 12.0 atom % and 17.0 atom %, and B in an amount of between 4.5 atom % and 7.5 atom %; the HDDR treatment includes a DR step including a preliminary evacuation step and a complete evacuation step; and a rate of pressure reduction caused by evacuation in the preliminary evacuation step is not less than 1 kPa/min and not more than 30 kPa/min.

Process for producing R-T-B-based rare earth magnet particles, R-T-B-based rare earth magnet particles, and bonded magnet

An object of the present invention is to enhance a coercive force of magnetic particles by promoting formation of a continuous R-rich grain boundary phase in a crystal grain boundary of a magnetic phase of the particles, and to thereby obtain R-T-B-based rare earth magnet particles further having a high residual magnetic flux density. The present invention relates to production of R-T-B-based rare earth magnet particles capable of exhibiting a high coercive force even when a content of Al therein is reduced, and a high residual magnetic flux density, in which formation of an R-rich grain boundary phase therein can be promoted by heat-treating Al-containing R-T-B-based rare earth magnet particles obtained by HDDR treatment in vacuum or in an Ar atmosphere at a temperature of not lower than 670&#xb0; C. and not higher than 820&#xb0; C. for a period of not less than 30 min and not more than 300 min.

R-T-B-based rare earth magnet particles, and bonded magnets containing R-T-B-based rare earth magnet particles

The present invention relates to surface-treated rare earth-based magnetic particles comprising rare-earth-based magnetic particles, a first coating layer comprising a phosphoric acid compound which is formed on a surface of the respective magnetic particles and a second coating layer in the form of a composite coating film comprising a silicon compound and a phosphoric acid compound which is formed on a surface of the first coating layer, wherein an amount of Fe eluted from the rare earth-based magnetic particles is not more than 10 mg/L; a resin composition for bonded magnets comprising the above surface-treated rare earth-based magnetic particles and a resin; and a bonded magnet comprising the above surface-treated rare earth-based magnetic particles.

Surface-treated rare earth-based magnetic particles, resin composition for bonded magnets comprising the earth-based magnetic particles and bonded magnet comprising the earth-based magnetic particles

R-T-B-based rare earth magnet particles are produced by an HDDR treatment which comprises a first stage HD step of heating particles of a raw material alloy having a composition of R, B and Co in an inert atmosphere or in a vacuum atmosphere and then replacing the atmosphere with a hydrogen-containing gas atmosphere in which the raw material alloy particles are held in the same temperature range and a second stage HD step of heating a material obtained in the first stage HD step in which the material is held in the hydrogen-containing gas atmosphere.

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Otake, Japan

Nobuhiro Katayama