Method for producing R-T-B sintered magnet

Patent metadata

Field	Value
Publication number	US-10563295-B2
Application number	US-201515304886-A
Country	US
Kind code	B2
Filing date	Apr 23, 2015
Priority date	Apr 25, 2014
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

A step is provided which performs a heat treatment at the sintering temperature of a sintered R-T-B based magnet or lower, while a powder of an RLM alloy (where RL is Nd and/or Pr; M is one or more selected from among Cu, Fe, Ga, Co and Ni) and a powder of an RH fluoride (where RH is Dy and/or Tb) are present on a surface of the sintered R-T-B based magnet. The RLM alloy contains RL in an amount of 50 at % or more, and a melting point of the RLM alloy is equal to or less than a temperature of the heat treatment. The heat treatment is performed while the RLM alloy powder and the RH fluoride powder are present on the surface of the sintered R-T-B based magnet at a mass ratio of RLM alloy:RH fluoride=96:4 to 5:5.

First claim

The invention claimed is:

1. A method for producing a sintered R-T-B based magnet, comprising:
a step of providing a sintered R-T-B based magnet, where R is one or more rare-earth elements, T is one or more transition metal elements, and B is boron or is boron and carbon; and
a step of performing a heat treatment at a sintering temperature of the sintered R-T-B based magnet or lower, while a powder of an Nd—Cu alloy consisting of Nd and Cu and a powder of an RH fluoride (where RH is Dy and/or Tb) are present on a surface of the sintered R-T-B based magnet, wherein,
an Nd content in the Nd—Cu alloy is 50 at % or more, and a melting point of the Nd—Cu alloy is equal to or less than a temperature of the heat treatment; and
the heat treatment is performed while the Nd—Cu alloy powder and the RH fluoride powder are present on the surface of the sintered R-T-B based magnet at a mass ratio of Nd—Cu alloy:RH fluoride=96:4 to 5:5, so that the RH fluoride powder is reduced by the Nd—Cu alloy powder to diffuse an RH element that is contained in the RH fluoride powder into the sintered R-T-B based magnet.

2. The method for producing a sintered R-T-B based magnet of claim 1 , wherein, on the surface of the sintered R-T-B based magnet, the RH element that is contained in the powder of the RH fluoride has a mass of 0.03 to 0.35 mg per 1 mm 2 of the surface.

3. The method for producing a sintered R-T-B based magnet of claim 1 , wherein the Nd—Cu alloy powder and the RH fluoride powder are in a mixed state on the surface of the sintered R-T-B based magnet.

4. The method for producing a sintered R-T-B based magnet of claim 1 , wherein substantially no powder of any RH oxide is present on the surface of the sintered R-T-B based magnet.

5. The method for producing a sintered R-T-B based magnet of claim 1 , wherein a part of the RH fluoride is an RH oxyfluoride.

Assignees

• Hitachi Metals Ltd

Inventors

• Mino Shuji

Classifications

• C22C33/02

  by powder metallurgy · CPC title

• C22C38/16

  containing copper · CPC title

• H01F41/0266

  Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11) · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/10

  containing cobalt · CPC title