RFeB SYSTEM MAGNET AND METHOD FOR PRODUCING RFeB SYSTEM MAGNET

Patent metadata

Field	Value
Publication number	US-2017194094-A1
Application number	US-201515315214-A
Country	US
Kind code	A1
Filing date	May 25, 2015
Priority date	Jun 2, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

An RFeB system sintered magnet wherein heavy rare-earth element RH which is at least one kind of rare-earth element selected from Dy, Tb and Ho is diffused into base material through the grain boundaries of base material made of a sintered compact of an RFeB system magnet containing RL, Fe and B, where RL represents a light rare-earth element which is at least one kind of rare-earth element selected from Nd and Pr, wherein: size of the RFeB system sintered magnet at smallest-size portion is greater than 3 mm; the amount of heavy rare-earth element RH contained in RFeB system sintered magnet divided by volume of RFeB system sintered magnet is ≧25 mg/cm3; and the difference between local coercivity at the surface of the smallest-size portion and in the central region of the smallest-size portion is equal to or less than 15% of local coercivity at the surface.

First claim

1 . An RFeB system sintered magnet in which a heavy rare-earth element R H which is at least one kind of rare-earth element selected from a group of Dy, Tb and Ho is diffused into a base material through grain boundaries of the same base material made of a sintered compact of an RFeB system magnet containing R L , Fe and B, where R L represents a light rare-earth element which is at least one kind of rare-earth element selected from a group of Nd and Pr, wherein:
a size of the RFeB system sintered magnet at a smallest-size portion is greater than 3 mm; an amount of heavy rare-earth element R H contained in the RFeB system sintered magnet divided by a volume of the RFeB system sintered magnet is equal to or greater than 25 mg/cm 3 ; and a difference between a local coercivity at a surface of the smallest-size portion and a local coercivity in a central region of the smallest-size portion is equal to or less than 15% of the local coercivity at the surface.

2 . The RFeB system sintered magnet according to claim 1 , wherein a carbon content is equal to or lower than 1000 ppm.

3 . An RFeB system sintered magnet production method, comprising:
a) a base material creation process in which a base material made of a sintered compact of an RFeB system magnet containing R L , Fe and B is created, where R L represents a light rare-earth element which is at least one kind of rare-earth element selected from a group of Nd and Pr, and a size of the sintered compact at a smallest-size portion is greater than 3 mm; and b) a grain boundary diffusion process in which a grain boundary diffusion treatment is performed including a step of adhering, to a surface of the base material, an adhesion material containing a heavy rare-earth element R H which is at least one kind of rare-earth element selected from a group of Dy, Tb and Ho, and a step of heating the adhesion material, where an amount of heavy rare-earth element R H contained in the adhesion material is controlled so that an amount of heavy rare-earth element R H contained in the RFeB system sintered magnet divided by a volume of the same RFeB system sintered magnet after the grain boundary diffusion treatment becomes equal to or greater than 25 mg/cm 3 .

4 . The RFeB system sintered magnet production method according to claim 3 , wherein a content of carbon in the base material is equal to or lower than 1000 ppm.

5 . The RFeB system sintered magnet production method according claim 3 , wherein the base material is created by filling a mold with an alloy powder containing the light rare-earth element R L , Fe and B as a raw material, orienting the alloy powder by applying a magnetic field without applying mechanical pressure for shaping, and sintering the alloy powder by heating the same powder as contained in the mold without applying mechanical pressure for shaping.

6 . The RFeB system sintered magnet production method according to claim 4 , wherein the base material is created by filling a mold with an alloy powder containing the light rare-earth element R L , Fe and B as a raw material, orienting the alloy powder by applying a magnetic field without applying mechanical pressure for shaping, and sintering the alloy powder by heating the same powder as contained in the mold without applying mechanical pressure for shaping.

Assignees

• Intermetallics Co Ltd
• Daido Steel Co Ltd

Inventors

• Mizoguchi Tetsuhiko
• Sagawa Masato

Classifications

• H01F41/0293 Primary

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

• C22C38/10

  containing cobalt · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C22C28/00

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