US 11,990,260 B2
Rare earth magnet and production method thereof
Masaaki Ito, Anjo (JP); Motoki Hiraoka, Toyota (JP); Reimi Tabuchi, Nisshin (JP); Hisashi Maehara, Itano-gun (JP); and Masanori Okanan, Anan (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 Nov. 1, 2022, as Appl. No. 17/978,688.
Claims priority of application No. 2021-178979 (JP), filed on Nov. 1, 2021; and application No. 2022-030024 (JP), filed on Feb. 28, 2022.
Prior Publication US 2023/0139716 A1, May 4, 2023
Int. Cl. H01F 1/059 (2006.01); C22C 38/00 (2006.01)
CPC H01F 1/059 (2013.01) [C22C 38/001 (2013.01); C22C 38/005 (2013.01); C22C 2202/02 (2013.01)] 6 Claims
OG exemplary drawing
 
1. A method for producing a rare earth magnet, comprising:
preparing a magnetic powder having a magnetic phase which contains Sm, Fe and N and at least partially has either a Th2Zn17 or Th2Ni17 crystal structure,
preparing a modifier powder containing at least either a metallic zinc or a zinc alloy,
mixing the magnetic powder and the modifier powder to obtain a mixed powder,
compression-molding the mixed powder in a magnetic field to obtain a magnetic-field molded body, and
pressure-sintering the magnetic-field molded body to obtain a sintered body, wherein
the magnetic powder includes a first particle group and a second particle group,
the particle size distribution D50 of the first particle group and the particle size distribution D50 of the second particle group are denoted by d1 μm and d2 μm, respectively,
d1 and d2 satisfy the relationship of 0.350≤d2/d1≤0.500,
the ratio between the total volume of the first particle group and the total volume of the second particle group, which is total volume of first particle group: total volume of second particle group, is from 9:1 to 4:1, and
d1 is from 3.0 to 3.7 μm and d2 is from 1.4 to 1.8 μm.