	US 12,217,907 B2
	Rare-earth magnet and method of manufacturing the same
Masaaki Ito, Anjo (JP); Daisuke Ichigozaki, Toyota (JP); Noritsugu Sakuma, Mishima (JP); Akihito Kinoshita, Mishima (JP); Michiya Kume, Anan (JP); and Hisashi Maehara, Itano-gun (JP)
Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA, Toyota (JP); and NICHIA CORPORATION, Anan (JP)
Filed by TOYOTA JIDOSHA KABUSHIKI KAISHA, Toyota (JP); and NICHIA CORPORATION, Anan (JP)
Filed on Dec. 1, 2021, as Appl. No. 17/539,491.
Claims priority of application No. 2020-209452 (JP), filed on Dec. 17, 2020.
Prior Publication US 2022/0199321 A1, Jun. 23, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. H01F 41/02 (2006.01); B22F 3/16 (2006.01); B22F 3/24 (2006.01); H01F 1/059 (2006.01)

CPC H01F 41/0266 (2013.01) [B22F 3/16 (2013.01); B22F 3/24 (2013.01); H01F 1/059 (2013.01); H01F 1/0596 (2013.01); B22F 2003/248 (2013.01); B22F 2202/05 (2013.01); B22F 2301/30 (2013.01); B22F 2301/355 (2013.01)]

8 Claims

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 Th₂Zn₁₇type and a Th₂Ni₁₇type;

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.