Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-11990260-B2
Application number	US-202217978688-A
Country	US
Kind code	B2
Filing date	Nov 1, 2022
Priority date	Nov 1, 2021
Publication date	May 21, 2024
Grant date	May 21, 2024

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

The invention claimed is:

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 either a Th 2 Zn 17 or Th 2 Ni 17 crystal structure,
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,
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, and
d 1 is from 3.0 to 3.7 μm and d 2 is from 1.4 to 1.8 μm.

2. 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.

3. 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.

4. 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.

5. The production method of a rare earth magnet according to claim 1 , further comprising,
before the pressure-sintering, previously forming a phosphoric acid 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.

6. The production method of a rare earth magnet according to claim 5 , wherein the sintered body is heat-treated at 350 to 410° C.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

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

Classifications

• H01F1/059 Primary

  and Va elements, e.g. Sm2Fe17N2 · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/005 Primary

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

• C22C2202/02

  Magnetic · CPC title

• H01F41/0266 Primary

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