R-t-b-based rare earth sintered magnet and method of manufacturing same

Patent metadata

Field	Value
Publication number	US-2016284452-A1
Application number	US-201615075757-A
Country	US
Kind code	A1
Filing date	Mar 21, 2016
Priority date	Mar 25, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

An R-T-B-based rare earth sintered magnet comprising: a rare earth element R, B, a metallic element M which includes one or more metals selected from Al, Ga and Cu, a transition metal T which includes Fe as a main component and inevitable impurities, wherein the sintered magnet includes: 13 to 15.5 atom % of R, 5.0 to 6.0 atom % of B, 0.1 to 2.4 atom % of M, and T and the inevitable impurities as a balance, and wherein the sintered magnet includes more than 0 atom % and 0.01 atom % or less of Tb as the rare earth element R.

First claim

What is claimed is:

1 . An R-T-B-based rare earth sintered magnet comprising:
a rare earth element R, B, a metallic element M which includes one or more metals selected from Al, Ga and Cu, a transition metal T which includes Fe as a main component and inevitable impurities, wherein the sintered magnet includes: 13 to 15.5 atom % of R, 5.0 to 6.0 atom % of B, 0.1 to 2.4 atom % of M, and T and the inevitable impurities as a balance,
and wherein
the sintered magnet includes more than 0 atom % and 0.01 atom % or less of Tb as the rare earth element R.

2 . The R-T-B-based rare earth sintered magnet according to claim 1 , comprising:
particles having a R 2 T 14 B crystal structure including Tb.

3 . The R-T-B-based rare earth sintered magnet according to claim 1 , wherein the sintered magnet satisfies the following formula (1):
0.32≦ B /TRE≦0.40  (1)
wherein, in the formula (1), B represents a concentration (atom %) of a boron element and TRE represents a concentration (atom %) of total rare earth elements.

4 . The R-T-B-based rare earth sintered magnet according to claim 1 ,
wherein the sintered magnet includes 0.015 atom % to 0.10 atom % of Zr as the transition metal T.

5 . The R-T-B-based rare earth sintered magnet according to claim 1 , comprising:
at least Ga as the metallic element M.

6 . A method of manufacturing an R-T-B-based rare earth sintered magnet comprising:
a sintering process of forming a sintered body using an alloy for an R-T-B-based magnet and an additive alloy, wherein
the alloy for an R-T-B-based magnet includes a rare earth element R, B, a metallic element M which includes one or more metals selected from Al, Ga and Cu, a transition metal T which includes Fe as a main component, and inevitable impurities, in which the alloy for an R-T-B-based magnet includes 13 atom % to 15.5 atom % of R, 5.0 atom % to 6.0 atom % of B, 0.1 atom % to 2.4 atom % of M, and T and the inevitable impurities as a balance, and wherein
the additive alloy includes a rare earth element R which essentially includes Tb, B, a metallic element M which includes one or more metals selected from Al, Ga and Cu, a transition metal T which includes Fe as a main component, and inevitable impurities, in which the additive alloy includes 13 atom % to 15.5 atom % of R, 5.0 atom % to 6.0 atom % of B, 0.1 atom % to 2.4 atom % of M, and T and the inevitable impurities as a balance; a first heat treatment process of putting the sintered body into a heat treatment furnace, carrying out a heat treatment in which the sintered body is held at a temperature in a range of 790° C. to 920° C. for 0.5 hours to 10 hours, and then cooling the sintered body at a cooling rate of 100° C./minute or higher; and a second heat treatment process of carrying out a heat treatment in which the sintered body that has undergone the first heat treatment is held at a temperature in a range of 480° C. to 620° C. for 0.05 hours to 10 hours, and then cooling the sintered body at a cooling rate of 100° C./minute or higher.

7 . The method of manufacturing an R-T-B-based rare earth sintered magnet according to claim 6 ,
wherein the additive alloy has an R 2 T 14 B crystal phase which includes Tb.

8 . The method of manufacturing an R-T-B-based rare earth sintered magnet according to claim 6 , wherein the sintered magnet satisfies the following formula (1):
0.32≦ B /TRE≦0.40  (1)
wherein, in the formula (1), B represents a concentration (atom %) of a boron element and TRE represents a concentration (atom %) of total rare earth elements.

9 . The method of manufacturing an R-T-B-based rare earth sintered magnet according to claim 6 ,
wherein the alloy for an R-T-B-based magnet does not include Tb.

10 . The method of manufacturing an R-T-B-based rare earth sintered magnet according to claim 6 ,
wherein the method further includes a sub process wherein the alloy for an R-T-B-based magnet and the additive alloy are mixed together in advance prior to the sintering process.

11 . The method of manufacturing an R-T-B-based rare earth sintered magnet according to claim 10 ,
wherein the amount of Tb in a mixture of the alloy for an R-T-B-based magnet and the additive alloy is set to more than 0 atom % and 0.01 atom % or less.

Assignees

• Showa Denko Kk

Inventors

• Horikita Masaki
• Nakajima Kenichiro
• Muraoka Akifumi

Classifications

• H01F1/0577

  sintered · CPC title

• C21D9/00

  Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor · CPC title

• C22C38/10

  containing cobalt · CPC title

• C22C38/005 Primary

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title

• H01F41/0253

  for manufacturing permanent magnets · CPC title