Sumitomo Special Metals Co., Ltd.

Neomax Co., Ltd.

Junichiro Baba

Yuji Kaneko

Katsuya Taniguchi

Shizuo Mori

Kazuo Tanaka

A method of making an alloy powder for an R&#x2014;Fe&#x2014;B-type rare earth magnet includes the steps of preparing a material alloy that is to be used for forming the R&#x2014;Fe&#x2014;B-type rare earth magnet and that has a chilled structure that constitutes about 2 volume percent to about 20 volume percent of the material alloy, coarsely pulverizing the material alloy for the R&#x2014;Fe&#x2014;B-type rare earth magnet by utilizing a hydrogen occlusion phenomenon to obtain a coarsely pulverized powder, finely pulverizing the coarsely pulverized powder and removing at least some of fine powder particles having particle sizes of about 1.0 &#x3bc;m or less from the finely pulverized powder, thereby reducing the volume fraction of the fine powder particles with the particle sizes of about 1.0 &#x3bc;m or less, and covering the surface of remaining ones of the powder particles with a lubricant after the step of removing has been performed.

Rare earth magnet and method for producing the magnet

A method of making an alloy powder for an R&mdash;Fe&mdash;B-type rare earth magnet includes the steps of preparing a material alloy that is to be used for forming the R&mdash;Fe&mdash;B-type rare earth magnet and that has a chilled structure that constitutes about 2 volume percent to about 20 volume percent of the material alloy, coarsely pulverizing the material alloy for the R&mdash;Fe&mdash;B-type rare earth magnet by utilizing a hydrogen occlusion phenomenon to obtain a coarsely pulverized powder, finely pulverizing the coarsely pulverized powder and removing at least some of fine powder particles having particle sizes of about 1.0 &mgr;m or less from the finely pulverized powder, thereby reducing the volume fraction of the fine powder particles with the particle sizes of about 1.0 &mgr;m or less, and covering the surface of remaining ones of the powder particles with a lubricant after the step of removing has been performed.

The method of producing an R&mdash;Fe&mdash;B magnet of the present invention is characterized in that R&mdash;Fe&mdash;B alloy fine powder is molded in a magnetic field and sintered using a lubricant for molding magnets containing specific components, individually or as a mixture, of specific amounts of methyl caproate and/or methyl caprylate, which provide high crystal orientation, and lubricant comprising depolymerized polymer for improving molded article strength, or a lubricant for molding magnets wherein Ti coupling agent that improves crystal orientation is added to this lubricant for molding magnets. Each particle of the fine powder has a high degree of crystal orientation in the direction of the magnetic field, and molded article strength is markedly improved, leading to improved mass-productivity and yield. Moreover, the above-mentioned lubricants do not react with this magnet powder during sintering and are emitted as a gas. Therefore, binder removal performance is excellent and as a result, an increase in the amount of C remaining in the sintered compact is inhibited, to obtain an R&mdash;Fe&mdash;B permanent magnet with high Br and iHc properties.

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Osaka, Japan

Junichiro Baba