	US 11,791,093 B2
	Rare earth permanent magnets and their preparation
Hiroaki Nagata, Echizen (JP); Tadao Nomura, Echizen (JP); and Takehisa Minowa, Echizen (JP)
Assigned to SHIN-ETSU CHEMICAL CO., LTD., Tokyo (JP)
Filed by SHIN-ETSU CHEMICAL CO., LTD., Tokyo (JP)
Filed on Feb. 26, 2020, as Appl. No. 16/801,828.
Application 16/801,828 is a division of application No. 15/454,433, filed on Mar. 9, 2017, granted, now 10,614,952.
Application 15/454,433 is a division of application No. 13/461,043, filed on May 1, 2012, abandoned.
Claims priority of application No. 2011-102787 (JP), filed on May 2, 2011; and application No. 2011-102789 (JP), filed on May 2, 2011.
Prior Publication US 2020/0194171 A1, Jun. 18, 2020
Int. Cl. H01F 1/057 (2006.01); H01F 41/02 (2006.01); B22F 3/24 (2006.01); C22C 38/00 (2006.01); C22C 38/06 (2006.01); C22C 38/10 (2006.01); C22C 38/16 (2006.01); C22C 33/02 (2006.01); B22F 1/17 (2022.01); B22F 3/12 (2006.01); B22F 9/04 (2006.01); B32B 15/01 (2006.01); C22C 19/07 (2006.01); H01F 1/055 (2006.01)

CPC H01F 41/0293 (2013.01) [B22F 1/17 (2022.01); B22F 3/12 (2013.01); B22F 3/24 (2013.01); B22F 9/04 (2013.01); B32B 15/01 (2013.01); C22C 19/07 (2013.01); C22C 33/0278 (2013.01); C22C 38/002 (2013.01); C22C 38/005 (2013.01); C22C 38/06 (2013.01); C22C 38/10 (2013.01); C22C 38/16 (2013.01); H01F 1/0557 (2013.01); B22F 2003/248 (2013.01); B22F 2009/041 (2013.01); B22F 2009/042 (2013.01); B22F 2009/044 (2013.01); B22F 2301/155 (2013.01); B22F 2301/355 (2013.01); B22F 2998/10 (2013.01); H01F 1/0577 (2013.01)]

16 Claims

1. A method for preparing a rare earth permanent magnet, comprising the steps of:

disposing a powder mixture on a surface of a sintered magnet body having the composition R_aT¹_bM_cB_dwherein R is at least one element selected from rare earth elements inclusive of Y and Sc, T¹is one or both of Fe and Co, M is at least one element selected from the group consisting of Al, Si, C, P, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pb, and Bi, B is boron, “a,” “b,” “c” and “d” indicative of atomic percent are in the range: 12≤a≤20, 0≤c≤10, 4.0≤d≤7.0, the balance of b, and a+b+c+d=100, the powder mixture comprising an M₁powder wherein M¹is one element selected from the group consisting of P, V, Cr, Ge, Zr, Nb, Mo, In, Sn, Sb, Hf, Ta, W, Pb, and Bi, having an average particle size of up to 500 μm, and at least 10% by weight of an R²oxide wherein R²is at least one element selected from rare earth elements inclusive of Y and Sc, having an average particle size of up to 100 μm, and

heat treating the sintered magnet body having the powder mixture disposed on its surface at a temperature lower than or equal to the sintering temperature of the sintered magnet body in vacuum or in an inert gas, for causing the elements R²and M¹in the powder mixture to diffuse to grain boundaries in the interior of the sintered magnet body and/or near grain boundaries within the sintered magnet body primary phase grains.