CPC B22F 3/00 (2013.01) [B22F 1/00 (2013.01); B22F 1/05 (2022.01); B22F 3/24 (2013.01); B22F 7/02 (2013.01); C21D 6/00 (2013.01); C22C 28/00 (2013.01); C22C 30/00 (2013.01); C22C 38/00 (2013.01); H01F 1/057 (2013.01); H01F 1/0577 (2013.01); H01F 41/02 (2013.01); H01F 41/0253 (2013.01); B22F 2003/248 (2013.01); B22F 2201/10 (2013.01); B22F 2201/20 (2013.01); B22F 2301/355 (2013.01); B22F 2301/45 (2013.01); B22F 2304/10 (2013.01); B22F 2998/10 (2013.01)] | 11 Claims |
1. A method for producing a sintered R-T-B based magnet, comprising:
a step of providing a sintered R-T-B based magnet, where R is a rare-earth element; and T is Fe, or Fe and Co;
a step of providing a particle size-adjusted powder that consists essentially of a powder of a Pr—Ga alloy, Pr accounts for 65 to 97 mass % of the entire Pr—Ga alloy; 20 mass % or less of Pr is replaceable with Nd; 30 mass % or less of Pr is replaceable with Dy and/or Tb; Ga accounts for 3 mass % to 35 mass % of the entire Pr—Ga alloy; and 50 mass % or less of Ga is replaceable with Cu; inevitable impurities may be contained;
an application step of applying an adhesive agent to an application area of a surface of the sintered R-T-B based magnet by spraying, by immersion, or by using a dispenser to form an adhesive layer;
an adhesion step of allowing the particle size-adjusted powder to adhere to the application area of the surface of the sintered R-T-B based magnet having the adhesive layer, wherein a fluidized-bed coating method is conducted to allow the sintered R-T-B based magnet having the adhesive layer to pass through the powder of the Pr—Ga alloy which is flowing inside a chamber; and
a heat treatment step of heating the sintered R-T-B based magnet having the particle size-adjusted powder adhering thereto at a temperature which is equal to or lower than a sintering temperature of the sintered R-T-B based magnet, wherein
the adhesion step is a step of allowing the particle size-adjusted powder to adhere in not less than one layer and not more than three layers to the surface of the sintered R-T-B based magnet, such that the amount of Ga contained in the particle size-adjusted powder adhering to the surface of the sintered R-T-B based magnet is in a range from 0.10 to 1.0% with respect to the sintered R-T-B based magnet by mass ratio.
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