PROCESS FOR PRODUCTION OF R-T-B BASED SINTERED MAGNETS AND R-T-B BASED SINTERED MAGNETS

• US 20120112863A1
• Filed: 07/12/2010
• Published: 05/10/2012
• Est. Priority Date: 07/15/2009
• Status: Active Grant

• Current Assignee: Proterial Ltd.
• Original Assignee: Hitachi Metals Limited (Hitachi Metals (Thailand) Ltd.)
• Inventors: Kuniyoshi, Futoshi
• Granted Patent: US 9,415,444 B2
• Time in Patent Office: Days
• US Class Current: 335/302
• CPC Class Codes: B22F 2003/241 Chemical after-treatment on the surface
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: C22C 19/07 based on cobalt
• CPC Class Codes: C22C 2202/02 Magnetic
• CPC Class Codes: C22C 28/00 Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
• CPC Class Codes: C22C 33/0278 with at least one alloying element having a minimum content above 5%
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22F 1/10 of nickel or cobalt or alloys based thereon
• CPC Class Codes: C22F 1/16 of other metals or alloys based thereon
• CPC Class Codes: H01F 1/0577 sintered
• CPC Class Codes: H01F 41/0293 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets

Abstract

A method for producing a sintered R-T-B based magnet includes the steps of: providing a sintered R-T-B based magnet body 1; providing an RH diffusion source 2 including a metal or an alloy of a heavy rare-earth element RH (which is at least one of Dy an Tb); loading the sintered magnet body 1 and the RH diffusion source 2 into a processing chamber 3 so that the magnet body 1 and the diffusion source 2 are movable relative to each other and brought close to, or in contact with, each other; and performing an RH diffusion process by conducting a heat treatment on the sintered R-T-B based magnet body 1 and the RH diffusion source 2 at a temperature of 500° C. to 850° C. for at least 10 minutes while moving the magnet body 1 and the diffusion source 2 either continuously or discontinuously in the processing chamber 3.

Claims

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;

providing an RH diffusion source including a metal or an alloy of a heavy rare-earth element RH (which is at least one of Dy an Tb);

loading the sintered R-T-B based 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 brought close to, or in contact with, each other; and

performing an RH diffusion process by conducting a heat treatment on the sintered R-T-B based magnet body and the RH diffusion source at a temperature of 500°

C. to 850°

C. for at least 10 minutes while moving the magnet body and the diffusion source either continuously or discontinuously in the processing chamber.

2. The method of claim 1, wherein the RH diffusion process includes rotating the processing chamber.

3. The method of claim 2, wherein the RH diffusion process includes rotating the processing chamber at a surface velocity of at least 0.01 m/s.

4. The method of claim 1, wherein in the RH diffusion process, the heat treatment is carried out with the internal pressure of the processing chamber adjusted to 100 kPa or less.

5. The method of claim 1, wherein in the RH diffusion process, the heat treatment is carried out by heating the processing chamber so that both the sintered R-T-B based magnet body and the RH diffusion source are heated.

6. The method of claim 1, comprising the step of introducing a stirring aid member into the processing chamber before or during the RH diffusion process.

7. A sintered R-T-B based magnet produced by the method of claim 1.