Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-2023139716-A1
Application number	US-202217978688-A
Country	US
Kind code	A1
Filing date	Nov 1, 2022
Priority date	Nov 1, 2021
Publication date	May 4, 2023
Grant date	—

Abstract

The present invention is a method for producing a rare earth magnet, including preparing a magnetic powder and a modifier powder, mixing them to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, and pressure-sintering the magnetic-field molded body to obtain a sintered body, wherein the magnetic powder includes a first particle group and a second particle group, the D 50 values of the first particle group and the second particle group are denoted by d 1 μm and d 2 μm, respectively, d 1 and d 2 satisfy the relationship of 0.350≤d 2 /d 1 ≤0.500, and the ratio between the total volume of the first particle group and the total volume of the second particle group is from 9:1 to 4:1; and a rare earth magnet obtained by the production method.

First claim

1 . A method for producing a rare earth magnet, comprising:
preparing a magnetic powder having a magnetic phase which contains Sm, Fe and N and at least partially has a crystal structure of either Th 2 Zn 17 type or Th 2 Ni 17 type, preparing a modifier powder containing at least either a metallic zinc or a zinc alloy, mixing the magnetic powder and the modifier powder to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, and pressure-sintering the magnetic-field molded body to obtain a sintered body, wherein the magnetic powder includes a first particle group and a second particle group, the particle size distribution D 50 of the first particle group and the particle size distribution D 50 of the second particle group are denoted by d 1 μm and d 2 μm, respectively, d 1 and d 2 satisfy the relationship of 0.350≤d 2 /d 1 ≤0.500, and the ratio between the total volume of the first particle group and the total volume of the second particle group, which is total volume of first particle group:total volume of second particle group, is from 9:1 to 4:1.

2 . The production method of a rare earth magnet according to claim 1 , wherein d 1 is from 3.0 to 3.7 μm and d 2 is from 1.4 to 1.8 μm.

3 . The production method of a rare earth magnet according to claim 1 , wherein D 50 of the modifier powder is from 0.1 to 12.0 μm and the content ratio of the zinc component in the modifier powder is from 1 to 30 mass % relative to the mixed powder.

4 . The production method of a rare earth magnet according to claim 1 , wherein the mixed powder is compression-molded at a pressure of 10 to 1,500 MPa.

5 . The production method of a rare earth magnet according to claim 1 , wherein the magnetic-field molded body is pressure-sintered at a pressure of 100 to 2,000 MPa and a temperature of 300 to 430° C. over 1 to 30 minutes.

6 . The production method of a rare earth magnet according to claim 1 , further comprising,
before the pressure-sintering, previously forming a modification-inhibiting coating on the particle surface of the second particle group, and heat-treating the sintered body to allow the progress of modification of the particle surface of the first particle group.

7 . The production method of a rare earth magnet according to claim 6 , wherein the modification-inhibiting coating contains phosphoric acid.

8 . The production method of a rare earth magnet according to claim 6 , wherein the sintered body is heat-treated at 350 to 410° C.

9 . A rare earth magnet that is a sintered body comprising:
a magnetic powder having a magnetic phase which contains Sm, Fe and N and at least partially has a crystal structure of either Th 2 Zn 17 type or Th 2 Ni 17 type, and a zinc component, wherein the magnetic powder includes a first particle group and a second particle group, the particle size distribution D 50 of the first particle group and the particle size distribution D 50 of the second particle group are denoted by d 1 μm and d 2 μm, respectively, d 1 and d 2 satisfy the relationship of 0.350≤d 2 /d 1 ≤50.500, and the ratio between the total volume of the first particle group and the total volume of the second particle group, which is total volume of first particle group:total volume of second particle group, is from 9:1 to 4:1.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

• Ito Masaaki
• Hiraoka Motoki
• Tabuchi Reimi
• Maehara Hisashi
• Okanan Masanori

Classifications

• C22C38/16

  containing copper · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/00

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

• C22C38/002

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

• C22C38/005 Primary

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title