Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-12322542-B2
Application number	US-202217986179-A
Country	US
Kind code	B2
Filing date	Nov 14, 2022
Priority date	Nov 24, 2021
Publication date	Jun 3, 2025
Grant date	Jun 3, 2025

Abstract

A Sm—Fe—N-based rare earth magnet more resistant to demagnetization than ever before, particularly at high temperatures, and a production method thereof are provided.
The present disclosure presents a production method of a rare earth magnet, including mixing a SmFeN magnetic powder and a modifier powder to obtain a mixed powder, compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, pressure-sintering the magnetic-field molded body to obtain a sintered body, and heat-treating the sintered body, and a rare earth magnet obtained by the method. D 50 of the magnetic powder is 1.50 μm or more and 3.00 μm or less, the content ratio of the zinc component in the modifier powder is 6 mass % or more and 30 mass % or less, and the heat treatment temperature is 350° C. or more and 410° C. or less.

First claim

The invention claimed is:

1. A production method of 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,
pressure-sintering the magnetic-field molded body to obtain a sintered body, and
heat-treating the sintered body, wherein
D 50 of the magnetic powder is 1.50 μm or more and 3.00 μm or less,
the content ratio of the zinc component in the modifier powder is 6 mass % or more and 30 mass % or less relative to the mixed powder, and
the heat treatment is performed at 350° C. or more and 410° C. or less.

2. The production method of a rare earth magnet according to claim 1 , wherein in the magnetic powder, the proportion of magnetic powder particles having a particle diameter of 1.00 μm or less to the total number of magnetic powder particles of the magnetic powder is 1.50% or less and the content ratio of the zinc component in the modifier powder is 6 mass % or more and 10 mass % or less relative to the mixed powder.

3. The production method of a rare earth magnet according to claim 1 , wherein the sintered body is heat-treated until a Fe—Zn alloy phase is formed on 90% or more of the particle surface of the magnetic powder in the sintered body.

4. The production method of a rare earth magnet according to claim 1 , wherein the heat treatment is performed at 350° C. or more and 400° C. or less.

5. The production method of a rare earth magnet according to claim 1 , wherein the heat treatment is performed over 3 hours or more and 40 hours or less.

6. 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 200 MPa or more and 1,500 MPa or less and a temperature of 300° C. or more and 400° C. or less over 1 minute or more and 30 minutes or less.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

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

Classifications

• H01F1/0596

  of rhombic or rhombohedral Th2Zn17 structure or hexagonal Th2Ni17 structure · CPC title

• H01F41/0273

  Imparting anisotropy (methods and devices for magnetising permanent magnets H01F13/003) · CPC title

• H01F41/0253 Primary

  for manufacturing permanent magnets · CPC title

• C22C38/001

  containing N · CPC title

• C22C2202/02

  Magnetic · CPC title