Method for producing R-T-B sintered magnet

Patent metadata

Field	Value
Publication number	US-9478332-B2
Application number	US-201314372543-A
Country	US
Kind code	B2
Filing date	Jan 17, 2013
Priority date	Jan 19, 2012
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A method for producing a sintered R-T-B based magnet includes providing a sintered R-T-B based magnet body, of which the rare-earth-element mole fraction falls within the range of 31 mass % to 37 mass %; providing an RH diffusion source including a heavy rare-earth element RH (which is at least one of Dy and Tb) and 30 mass % to 80 mass % of Fe; loading the sintered magnet body and the RH diffusion source into a processing chamber so that the magnet body and the diffusion source are movable relative to each other and readily brought close to, or in contact with, each other; and performing an RH diffusion process by conducting a heat treatment on the sintered magnet body and the RH diffusion source at a process temperature of 700° C. to 1000° C. while moving the sintered magnet body and the RH diffusion source either continuously or discontinuously.

First claim

The invention claimed is:

1. A method for producing a sintered magnet, the method comprising the steps of:
providing a sintered R-T-B based magnet body, of which the R mole fraction that is defined by the content of a rare-earth element falls within the range of 31 mass % to 37 mass %;
providing an RH diffusion source including a heavy rare-earth element RH, which is at least one of Dy and Tb, and including a volume percentage of an RHFe 2 compound and/or an RHFe 3 compound of 90% or more;
loading the sintered magnet body and the RH diffusion source into a processing chamber so that the magnet body and the diffusion source are movable relative to each other and readily brought close to, or in contact with, each other; and
performing an RH diffusion process by conducting a heat treatment on the sintered magnet body and the RH diffusion source at a process temperature of 870° C. to 970° C. and at an internal processing pressure of 10 −2 Pa to atmospheric pressure while rotating the processing chamber at a peripheral velocity of 0.01 m/s or more to continuously or discontinuously move the sintered magnet body and the RH diffusion source in the processing chamber; wherein
the sintered magnet body has an effective rare-earth content of 28 mass % to 35 mass %, in which the effective rare-earth content is defined by the following equation:
the effective rare-earth content=the R mole fraction−(6×O mole fraction+8×C mole fraction+10×N mole fraction),

where the O mole fraction is an oxygen content of the sintered magnet body, the C mole fraction is a carbon content of the sintered magnet body, and the N mole fraction is a nitrogen content of the sintered magnet body.

Assignees

• Hitachi Metals Ltd

Inventors

• Kuniyoshi Futoshi
• Ishii Rintaro
• YAMAGATA Ryouichi

Classifications

• C22C28/00 Primary

  Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00 · CPC title

• B22F2207/01

  Composition gradients · CPC title

• C22C38/16

  containing copper · CPC title

• B22F3/26

  Impregnating {(making ferrous alloys by impregnation C22C33/0242)} · CPC title

• C22C38/10

  containing cobalt · CPC title