# US 9,039,920 B2 · Permanent magnet and manufacturing method thereof

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 9,039,920 B2
- Document ID: US9039920B2
- Status: Granted
- Kind: B2
- Application number: 13/499,616
- Filed: 2011-03-28
- Published: 2012-07-26
- Granted: 2015-05-26
- Earliest claimed: 2010-03-31
- Assignees: Nitto Denko Corporation
- Applicants: Izumi Ozeki; Katsuya Kume; Keisuke Hirano; Tomohiro Omure; Keisuke Taihaku; Takashi Ozaki
- Inventors: Izumi Ozeki; Katsuya Kume; Keisuke Hirano; Tomohiro Omure; Keisuke Taihaku; Takashi Ozaki
- Web page: https://patentgrep.com/patent/US9039920B2

## CPC

- H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides}
- H01F 1/0572: {with a protective layer}
- H01F 1/086: {sintered}
- B22F 2998/00: Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- C22C 2202/02: Magnetic
- H01F 1/0577: {sintered}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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

## Abstract

There are provided a permanent magnet and a manufacturing method thereof enabling carbon content contained in magnet particles to be reduced in advance before sintering even when wet milling is employed. Coarsely-milled magnet powder is further milled by a bead mill in a solvent together with an organometallic compound expressed with a structural formula of M-(OR)X (M represents V, Mo, Zr, Ta Ti W or Nb, R represents a substituent group consisting of a straight-chain or branched-chain hydrocarbon, X represents an arbitrary integer) so as to uniformly adhere the organometallic compound to particle surfaces of the magnet powder. Thereafter, a compact body of compacted magnet powder is held for several hours in hydrogen atmosphere at 200 through 900 degrees Celsius to perform hydrogen calcination process. Thereafter, through sintering process, a permanent magnet 1 is formed.

## Claims

### Claim 1

A manufacturing method of a Nd—Fe—B based permanent magnet comprising steps of
wet-milling magnet material in an organic solvent together with an organometallic compound expressed with a structural formula of
M-(OR)X
(M representing V, Mo, Zr, Ta, Ti, W or Nb, R representing a substituent group consisting of a straight-chain or branched-chain hydrocarbon, and X is an integer corresponding to the valence of M) to obtain magnet powder of the magnet material currently milled and to have the organometallic compound adhered to particle surfaces of the magnet powder;
compacting the magnet powder having the organometallic compound adhered to particle surfaces thereof so as to form a compact body;
calcining the compact body in hydrogen atmosphere so as to obtain a calcined body; and
sintering the calcined body.

### Claim 2

A manufacturing method of a Nd—Fe—B based permanent magnet comprising steps of
wet-milling magnet material in an organic solvent together with an organometallic compound expressed with a structural formula of
M-(OR)X
(M representing V, Mo, Zr, Ta, Ti, W or Nb, R representing a substituent group consisting of a straight-chain or branched-chain hydrocarbon, and X is an integer corresponding to the valence of M) to obtain magnet powder of the magnet material currently milled and to have the organometallic compound adhered to particle surfaces of the magnet powder;
calcining the magnet powder having the organometallic compound adhered to particle surfaces thereof in hydrogen atmosphere so as to form a calcined body;
compacting the calcined body so as to obtain a compact body; and
sintering the compact body.

### Claim 3 (depends on 1)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 1, wherein R in the structural formula is an alkyl group.

### Claim 4 (depends on 3)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 3, wherein R in the structural formula is an alkyl group of which carbon number is any one of integer numbers 2 through 6.

### Claim 5 (depends on 1)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 1, wherein, in the step of wet-milling the magnet material, the magnet material is milled by a bead mill into the magnet powder including single-domain particles.

### Claim 6 (depends on 2)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 2, wherein R in the structural formula is an alkyl group.

### Claim 7 (depends on 6)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 6, wherein R in the structural formula is an alkyl group of which carbon number is any one of integer numbers 2 through 6.

### Claim 8 (depends on 2)

The manufacturing method of a Nd—Fe—B based permanent magnet according to claim 2, wherein, in the step of wet-milling the magnet material, the magnet material is milled by a bead mill into the magnet powder including single-domain particles.