R-T-B-based sintered magnet and method for producing same

Patent metadata

Field	Value
Publication number	US-10923256-B2
Application number	US-201615739261-A
Country	US
Kind code	B2
Filing date	Jun 17, 2016
Priority date	Jun 25, 2015
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

To provide an R-T-B based sintered magnet including R: 27.5 to 34.0% by mass, RH: 2 to 10% by mass, B: 0.89 to 0.95% by mass, Ti: 0.1 to 0.2% by mass, Ga: 0.3 to 0.7% by mass, Cu: 0.07 to 0.50% by mass, Al: 0.05 to 0.50% by mass, M (M is Nb and/or Zr): 0 to 0.3% by mass, balance T, and inevitable impurities, the following inequality expressions (1), (2), and (3) being satisfied:

[T]−72.3([B]−0.45[Ti])>0  (1)

([T]−72.3([B]−0.45[Ti]))/55.85<13[Ga]/69.72  (2)

[Ga]≥[Cu]  (3).

First claim

The invention claimed is:

1. An R-T-B based sintered magnet comprising:
R (R is at least one of rare-earth elements, and indispensably contains Nd and a heavy rare-earth element RH (at least one of Dy, Tb, Gd, and Ho)): 27.5 to 34.0% by mass,
RH: 2 to 10% by mass,
B: 0.89 to 0.95% by mass,
Ti: 0.1 to 0.2% by mass,
Ga: 0.3 to 0.7% by mass,
Cu: 0.07 to 0.50% by mass,
Al: 0.05 to 0.50% by mass,
M (M is Nb and/or Zr): 0 to 0.3% by mass,
balance T (T is a transition metal element and indispensably contains Fe), and inevitable impurities, the following inequality expressions (1), (2), and (3) being satisfied:
[T]−72.3([B]−0.45[Ti])>0  (1)

([T]−72.3([B]−0.45[Ti]))/55.85<13[Ga]/69.72  (2)

[Ga]≥[Cu]  (3)

where [T] is the content of T expressed in terms of % by mass, [B] is the content of B expressed in terms of % by mass, [Ti] is the content of Ti expressed in terms of % by mass, [Ga] is the content of Ga expressed in terms of % by mass, and [Cu] is the content of Cu expressed in terms of % by mass.

2. The R-T-B based sintered magnet according to claim 1 , further comprising:
Ti: 0.1% by mass or more and less than 0.15% by mass.

3. A method for producing the RTB based sintered magnet according to claim 1 , the method comprising:
a step of preparing one or more kinds of main alloy powders and one or more kinds of additional alloy powders;
a step of mixing the one or more kinds of additional alloy powders with 0.5% by mass or more and 20% by mass or less among 100% by mass of a mixed alloy powder after mixing to obtain the mixed alloy powder of the one or more kinds of main alloy powders and the one or more kinds of additional alloy powders;
a molding step of molding the mixed alloy powder to obtain a molded body;
a sintering step of sintering the molded body to obtain a sintered body; and
a heat treatment step of subjecting the sintered body to a heat treatment;
wherein the one or more kinds of main alloy powders have the composition comprising:
R: 27.5 to 34.0% by mass,
RH: 2 to 10% by mass,
B: 0.89 to 0.97% by mass,
Ti: 0 to 0.2% by mass (excluding 0% by mass when Ti accounts for 0% by mass in the one or more kinds of additional alloy powders),
Ga: 0 to 0.4% by mass,
Cu: 0.07 to 0.50% by mass,
Al: 0.05 to 0.50% by mass,
balance T and inevitable impurities, and
the one or more kinds of additional alloy powders have the composition comprising:
R1 (R1 is at least one of rare-earth elements other than a heavy rare-earth element RH, and indispensably contains Nd): 32 to 66% by mass,
B: 0.3 to 0.9% by mass,
Ti: 0 to 4% by mass (excluding 0% by mass when Ti accounts for 0% by mass in the one or more kinds of main alloy powders),
Ga: 0.7 to 12% by mass,
Cu: 0 to 4% by mass,
Al: 0 to 10% by mass,
balance T and inevitable impurities, the composition satisfying the following inequality expression (4):
[T]≤72.4[B]  (4).

4. The method for producing an R-T-B based sintered magnet according to claim 3 , wherein the one or more kinds of main alloy powders are obtained by using a strip casting method.

5. A method for producing the R-T-B based sintered magnet according to claim 2 , the method comprising:
a step of preparing one or more kinds of main alloy powders and one or more kinds of additional alloy powders;
a step of mixing the one or more kinds of additional alloy powders with 0.5% by mass or more and 20% by mass or less among 100% by mass of a mixed alloy powder after mixing to obtain the mixed alloy powder of the one or more kinds of main alloy powders and the one or more kinds of additional alloy powders;
a molding step of molding the mixed alloy powder to obtain a molded body;
a sintering step of sintering the molded body to obtain a sintered body; and
a heat treatment step of subjecting the sintered body to a heat treatment;
wherein the one or more kinds of main alloy powders have the composition comprising:
R: 27.5 to 34.0% by mass,
RH: 2 to 10% by mass,
B: 0.89 to 0.97% by mass,
Ti: 0 to 0.2% by mass (excluding 0% by mass when Ti accounts for 0% by mass in the one or more kinds of additional alloy powders),
Ga: 0 to 0.4% by mass,
Cu: 0.07 to 0.50% by mass,
Al: 0.05 to 0.50% by mass,
balance T and inevitable impurities, and
the one or more kinds of additional alloy powders have the composition comprising:
R1 (R1 is at least one of rare-earth elements other than a heavy rare-earth element RH, and indispensably contains Nd): 32 to 66% by mass,
B: 0.3 to 0.9% by mass,
Ti: 0 to 4% by mass (excluding 0% by mass when Ti accounts for 0% by mass in the one or more kinds of main alloy powders),
Ga: 0.7 to 12% by mass,
Cu: 0 to 4% by mass,
Al: 0 to 10% by mass,
balance T and inevitable impurities, the composition satisfying the following inequality expression (4):
[T]≤72.4[B]  (4).

6. The method for producing an R-T-B based sintered magnet according to claim 5 , wherein the one or more kinds of main alloy powders are obtained by using a strip casting method.

7. The R-T-B based sintered magnet according to claim 1 , wherein R is present in a content of 30.67 to 34.0% by mass.

Assignees

• Hitachi Metals Ltd

Inventors

• Satoh Teppei
• Kuniyoshi Futoshi
• Ishii Rintaro
• Nishiuchi Takeshi
• Nozawa Noriyuki

Classifications

• H01F1/0577 Primary

  sintered · CPC title

• B22F10/64 Primary

  by thermal means (control of energy beam parameters for post heating B22F10/364) · CPC title

• B22F1/00

  Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties · CPC title

• B22F3/00

  Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor {; Presses and furnaces} · CPC title

• Y02P10/25

  Process efficiency · CPC title