Rare earth magnet and production method thereof

Patent metadata

Field	Value
Publication number	US-12191059-B2
Application number	US-202217986366-A
Country	US
Kind code	B2
Filing date	Nov 14, 2022
Priority date	Nov 24, 2021
Publication date	Jan 7, 2025
Grant date	Jan 7, 2025

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. D 50 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

The invention claimed is:

1. A production method of a rare earth magnet, comprising:
forming a zinc-containing coating on a 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 a mixture of a plurality of the coated magnetic powders 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 2.00 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 rare earth magnet, a proportion of magnetic powder having a particle diameter of 1.00 μm or less to a total number of magnetic powder is 1.50% or less, and a content ratio of the zinc component in the coated magnetic powder is from 3 mass % to 10 mass % 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 an outer surface of each of the coated magnetic powders 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 from 200 MPa to 1,500 MPa and a temperature of from 300° C. to 400° C. from 1 minute to 30 minutes.

7. The production method of a rare earth magnet according to claim 1 , wherein the heat treatment is performed under vacuum.

8. The production method of a rare earth magnet according to claim 1 , wherein the compression molding is performed with a pressure of from 50 MPa to 1,500 MPa.

Assignees

• Toyota Motor Co Ltd
• Nichia Corp

Inventors

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

Classifications

• B22F2304/10

  Micron size particles, i.e. above 1 micrometer up to 500 micrometer · CPC title

• B22F2303/30

  Coating alloy · CPC title

• B22F2303/01

  Main component · CPC title

• B22F2302/20

  Nitride · CPC title

• B22F2301/35

  Iron · CPC title