# US 12,217,907 B2 · Rare-earth magnet and method of manufacturing the same

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- Number: US 12,217,907 B2
- Document ID: US12217907B2
- Status: Granted
- Kind: B2
- Application number: 17/539,491
- Filed: 2021-12-01
- Published: 2022-06-23
- Granted: 2025-02-04
- Earliest claimed: 2020-12-17
- Assignees: Toyota Jidosha Kabushiki Kaisha; Nichia Corporation
- Applicants: Toyota Jidosha Kabushiki Kaisha; Nichia Corporation
- Inventors: Masaaki Ito; Daisuke Ichigozaki; Noritsugu Sakuma; Akihito Kinoshita; Michiya Kume; Hisashi Maehara
- Web page: https://patentgrep.com/patent/US12217907B2

## CPC

- B22F 1/12: Metallic powder containing non-metallic particles (containing lubricating or binding agents or organic material B22F1/10)
- H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)}
- B22F 3/16: in successive or repeated steps
- B22F 3/24: After-treatment of workpieces or articles {(B22F3/1146 takes precedence)}
- H01F 1/059: and Va elements, e.g. Sm2Fe17N2
- H01F 1/0596: {of rhombic or rhombohedral Th2Zn17 structure or hexagonal Th2Ni17 structure}
- H01F 41/0273: {Imparting anisotropy (methods and devices for magnetising permanent magnets H01F13/003)}
- B22F 2003/248: {Thermal after-treatment}
- B22F 2202/05: Use of magnetic field
- B22F 2301/30: Low melting point metals, i.e. Zn, Pb, Sn, Cd, In, Ga
- B22F 2301/355: Rare Earth - Fe intermetallic alloys
- B22F 2998/10: Processes characterised by the sequence of their steps
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- C22C 2202/02: Magnetic
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A rare-earth magnet and a method of manufacturing the same are provided. The method includes: preparing Sm—Fe—N magnetic powder; preparing reforming material powder containing metallic zinc; mixing the magnetic powder and the reforming material powder to obtain mixed powder; subjecting the mixed powder to compression molding in a magnetic field to obtain a magnetic-field molded body; subjecting the magnetic-field molded body to pressure sintering to obtain a sintered body; and subjecting the sintered body to heat treatment. A content proportion of the metallic zinc in the reforming material powder is 10 to 30% by mass with respect to the mixed powder. When a temperature and time in conditions for the heat treatment are defined as x° C. and y hours, respectively, the formulas y≥−0.32x+136 and 350≤x≤410 are met.

## Claims

### Claim 1

A method of manufacturing a rare-earth magnet, comprising:
preparing magnetic powder including magnetic phases containing Sm, Fe, and N, at least a part of the magnetic phases having a crystal structure of one of a Th2Zn17 type and a Th2Ni17 type;
preparing reforming material powder containing metallic zinc;
mixing the magnetic powder and the reforming material powder to obtain mixed powder;
subjecting the mixed powder to compression molding in a magnetic field to obtain a magnetic-field molded body;
subjecting the magnetic-field molded body to pressure sintering to obtain a sintered body; and
subjecting the sintered body to heat treatment, wherein:
a content proportion of the metallic zinc in the reforming material powder is greater than 20% by mass and is equal to or less than 30% by mass with respect to the mixed powder; and
when a temperature and time in conditions for the heat treatment are defined as x° C. and y hours, respectively, the following formulas are met:
y≥−0.32x+136
350≤x≤410, and
y≥14.4.

### Claim 2 (depends on 1)

The method according to claim 1, wherein x meets 350≤x≤400.

### Claim 3 (depends on 1)

The method according to claim 1, wherein y meets y≤40.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the magnetic-field molded body is subjected to pressure sintering for one to 30 minutes at pressures of 1000 to 1500 MPa and at temperatures of 300 to 400° C.

### Claim 5 (depends on 1)

The method according to claim 1, wherein a proportion of magnetic particles having particle diameters of 1.0 μm or less in the magnetic powder is 1 to 20% with respect to all the magnetic particles in the magnetic powder.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the rare-earth magnet has an orientation degree of 0.92 or higher and a magnetization in an external magnetic field of −1600 kA/m of no lower than 0.47.

### Claim 7 (depends on 1)

The method according to claim 1, wherein a proportion of magnetic phases having particle diameters of 1.0 μm or less in the sintered body after heat treatment is 9.56% or less.

### Claim 8

A method of manufacturing a rare-earth magnet, comprising:
preparing magnetic powder including magnetic phases containing Sm, Fe, and N, at least a part of the magnetic phases having a crystal structure of one of a Th2Zn17 type and a Th2Ni17 type;
preparing reforming material powder containing metallic zinc;
mixing the magnetic powder and the reforming material powder to obtain mixed powder;
subjecting the mixed powder to compression molding in a magnetic field to obtain a magnetic-field molded body;
subjecting the magnetic-field molded body to pressure sintering to obtain a sintered body; and
subjecting the sintered body to heat treatment, wherein:
a content proportion of the metallic zinc in the reforming material powder is greater than 20% by mass and is equal to or less than 30% by mass with respect to the mixed powder; and
when a temperature and time in conditions for the heat treatment are defined as x° C. and y hours, respectively, the following formulas are met:
y≥−0.32x+136
350≤x≤410, and
y≥14.4,
wherein the rare-earth magnet has an orientation degree of 0.92 or higher and a magnetization in an external magnetic field of −1600 kA/m of no lower than 0.47.