Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-2023162913-A1
Application number	US-202217986179-A
Country	US
Kind code	A1
Filing date	Nov 14, 2022
Priority date	Nov 24, 2021
Publication date	May 25, 2023
Grant date	—

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. D50 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

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.

7 . A rare earth magnet comprising a magnetic powder that is sintered together with a modifier powder containing at least either a metallic zinc or a zinc alloy, wherein
the magnetic powder contains Sm, Fe and N, the magnetic powder at least partially has a crystal structure of either Th 2 Zn 17 type or Th 2 Ni 17 type, the rare earth magnet contains 6 mass % or more and 30 mass % or less of a zinc component, D 50 of the magnetic powder is 1.50 μm or more and 3.00 μm or less, and a Fe—Zn alloy phase is formed on 90% or more of the surface of the magnetic powder.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

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

Classifications

• C22C38/00

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

• C22C38/06

  containing aluminium · CPC title

• C22C38/16

  containing copper · CPC title

• C22C38/005 Primary

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

• C22C38/002

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