# US 2014/0191831 A1 · R-t-b rare earth sintered magnet, alloy for r-t-b rare earth sintered magnet, and method of manufacturing the same

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- Number: US 2014/0191831 A1
- Document ID: US20140191831A1
- Status: Published application
- Kind: A1
- Application number: 14/146,098
- Filed: 2014-01-02
- Published: 2014-07-10
- Earliest claimed: 2013-01-07
- Assignees: Showa Denko K.K.
- Applicants: Showa Denko K.K.
- Inventors: Takashi YAMAZAKI; Kenichiro NAKAJIMA
- Web page: https://patentgrep.com/patent/US20140191831A1

## CPC

- H01F 1/0577: {sintered}
- 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}
- C22C 38/06: containing aluminium
- C22C 38/16: containing copper
- H01F 1/0571: {in the form of particles, e.g. rapid quenched powders or ribbon flakes}
- H01F 1/40: of magnetic semiconductor materials, e.g. CdCr2S4 (devices using galvano-magnetic or similar effects H10N50/00)
- H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)}
- H01F 41/0273: {Imparting anisotropy (methods and devices for magnetising permanent magnets H01F13/003)}
- B22F 1/068: Flake-like particles
- 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
- H01F 41/0293: {diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets}
- 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

An R-T-B rare earth sintered magnet contains R which represents a rare earth element; T which represents a transition metal essentially containing Fe; a metal element M which represents Al and/or Ga; B; Cu; and inevitable impurities the R-T-B rare earth sintered magnet including 13.4 to 17 at % of R, 4.5 to 5.5 at % of B, and 0.1 to 2.0 at % of M, and T as the balance; in which the R-T-B rare earth sintered magnet is formed of a sintered body which includes a main phase composed of R2Fe14B and a grain boundary phase including a larger amount of R than the main phase; in which the magnetization direction of the main phase is a c-axis direction, in which crystal grains of the main phase have one of an elliptical shape and an oval shape extended in such a direction so as to cross the c-axis direction; and in which the grain boundary phase includes an R-rich phase in which the total atomic concentration of the rare earth elements is 70 at % or greater and a transition metal-rich phase in which the total atomic concentration of the rare earth elements is 25 to 35 at %.

## Claims

### Claim 1

An R-T-B rare earth sintered magnet comprising R which represents a rare earth element; T which represents a transition metal essentially containing Fe; a metal element M which represents Al and/or Ga; B; Cu; and inevitable impurities;
wherein the R-T-B rare earth sintered magnet contains 13.4 to 17 at % of R, 4.5 to 5.5 at % of B, and 0.1 to 2.0 at % of M and T as the balance;
wherein the R-T-B rare earth sintered magnet is formed of a sintered body which includes a main phase composed of R2Fe14B and a grain boundary phase including a larger amount of R than the main phase;
wherein a magnetization direction of the main phase is a c-axis direction;
wherein crystal grains of the main phase have one of an elliptical shape and an oval shape extended in such a direction so as to cross the c-axis direction; and
wherein the grain boundary phase includes an R-rich phase in which a total atomic concentration of the rare earth elements is 70 at % or greater, and a transition metal-rich phase in which a total atomic concentration of the rare earth elements is 25 to 35 at %.

### Claim 2 (depends on 1)

The R-T-B rare earth sintered magnet according to claim 1,
wherein 50% or more of the crystal grains of the main phase have an aspect ratio of 2 or greater.

### Claim 3 (depends on 1)

The R-T-B rare earth sintered magnet according to claim 1,
further comprising 0.05 to 1.0 at % of Zr.

### Claim 4

An alloy for an R-T-B rare earth sintered magnet comprising R which represents a rare earth element; T which represents a transition metal essentially containing Fe; a metal element M which represents Al and/or Ga; B; Cu; and inevitable impurities;
wherein the R-T-B rare earth sintered magnet contains 13.4 to 17 at % of R, 4.5 to 5.5 at % of B, 0.1 to 2.0 at % of M and T as the balance;
wherein a main phase composed of R2Fe14B and a grain boundary phase including a larger amount of R than the main phase are included; and
wherein a distance between adjacent grain boundary phases is 1.5 μm to 2.8 μm.

### Claim 5

A method of manufacturing an alloy for an R-T-B rare earth sintered magnet, comprising:
a casting step of producing a cast alloy using a strip cast method including supplying a molten alloy to a cooling roll and solidifying the molten alloy;
wherein the molten alloy contains R which represents a rare earth element, T which represents a transition metal essentially containing Fe, a metal element M which represents Al and/or Ga, B, Cu, and inevitable impurities;
wherein the molten alloy contains 13.4 to 17 at % of R, 4.5 to 5.5 at % of B, 0.1 to 2.0 at % of M, and T as the balance; and
wherein in the casting step, the cast alloy is removed from the cooling roll at 400° C. to 600° C. to obtain the cast alloy having an average thickness of 0.15 mm to 0.27 mm.

### Claim 6 (depends on 5)

The method of manufacturing an alloy for an R-T-B rare earth sintered magnet according to claim 5,
wherein an average cooling rate until the molten metal supplied to the cooling roll is removed as the cast alloy from the cooling roll is 800° C./s to 1000° C./s.