Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-2023162898-A1
Application number	US-202217986366-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 in an environment where an external magnetic field is applied, particularly at high temperatures, and a production method thereof are provided.The present disclosure presents a production method of a rare earth magnet, including preparing a coated magnetic powder, compression-molding the coated magnetic 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 in the coated magnetic powder is 1.50 μm or more and 3.00 μm or less, the content ratio of the zinc component in the coated magnetic powder is 3 mass % or more and 15 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:
forming a zinc-containing coating on the particle surface of 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, to obtain a coated magnetic powder, compression-molding the coated magnetic 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 coated magnetic powder is 3 mass % or more and 15 mass % or less relative to the coated magnetic 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 coated magnetic powder is 3 mass % or more and 10 mass % or less relative to the coated magnetic 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 surface of the magnetic powder particle 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 obtained by sintering a coated magnetic powder including a magnetic powder particle having formed on the surface thereof a zinc-containing coating, wherein
the magnetic powder contains Sm, Fe and N, the magnetic powder at least partially has a magnetic phase having a crystal structure of either Th 2 Zn 17 type or Th 2 Ni 17 type, the rare earth magnet contains 3 mass % or more and 15 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 particle.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

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

Classifications

• B22F2303/01

  Main component · CPC title

• B22F1/142

  Thermal or thermo-mechanical treatment · CPC title

• B22F1/05

  Metallic powder characterised by the size or surface area of the particles · CPC title

• H01F41/0273 Primary

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

• B22F2203/11

  temperature, temperature profile · CPC title