RH diffusion source, and method for producing R-T-B-based sintered magnet using same

Patent metadata

Field	Value
Publication number	US-9613748-B2
Application number	US-201214127174-A
Country	US
Kind code	B2
Filing date	Jun 25, 2012
Priority date	Jun 27, 2011
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A method for producing a sintered R-T-B based magnet includes providing a sintered R-T-B based magnet body, where T is mostly Fe; providing an RH diffusion source that includes 0.2 mass % to 18 mass % of a light rare-earth element RL; 40 mass % to 70 mass % of Fe; and a heavy rare-earth element RH as the balance; and performing an RH diffusion process by loading the sintered R-T-B based magnet body, a stirring aid member, and the RH diffusion source into a chamber, and by heating the sintered R-T-B based magnet body, the stirring aid member, and the RH diffusion source to a temperature of 700° C. to 1000° C. while rotating or rocking the chamber. The Fe/RH ratio is within a range from two to seven and is defined by a mass fraction of Fe when a mass fraction of the heavy rare-earth element RH in the RH diffusion sources is three.

First claim

The invention claimed is:

1. A method for producing a sintered R-T-B based magnet, the method comprising the steps of:
providing a sintered R-T-B based magnet body, where R is a rare-earth element, and T is a transition metal element which is mostly comprised of Fe, and B is boron;
providing an RH diffusion source which is an alloy comprising: 0.2 mass % to 18 mass % of light rare-earth element RL, which is at least one of Nd and Pr; 40 mass % to 70 mass % of Fe; and a heavy rare-earth element RH, which is at least one of Dy and Tb, as the balance, wherein Fe/RH ratio is within a range from two to seven, the Fe/RH ratio being defined by a mass fraction of Fe when a mass fraction of the heavy rare-earth element RH included in the RH diffusion sources is three; and
performing an RH diffusion process by loading the sintered R-T-B based magnet body, a stirring aid member, and the RH diffusion source into a processing chamber so that the sintered R-T-B based magnet body, the stirring aid member, and the RH diffusion source are movable relative to each other, and by heating the sintered R-T-B based magnet body, the stirring aid member, and the RH diffusion source to a processing temperature of 700° C. to 1000° C. while moving the sintered R-T-B based magnet body and the RH diffusion source in the processing chamber either continuously or discontinuously by rotating or rocking the processing chamber.

2. The method of claim 1 , wherein the stirring aid member is made of zirconia, silicon nitride, silicon carbide, boron nitride, or any combination thereof.

Assignees

• Kuniyoshi Futoshi
• Hitachi Metals Ltd

Inventors

• Kuniyoshi Futoshi

Classifications

• H01F41/0293

  diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets · CPC title

• C22C2202/02

  Magnetic · CPC title

• C22C28/00 Primary

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

• H01F41/005 Primary

  Impregnating or encapsulating (insulating of windings H01F41/12) · CPC title

• C22C33/02

  by powder metallurgy · CPC title