Rare-earth iron-based ring magnet and method for manufacturing same
AssigneeMINEBEA MITSUMI Inc.
InventorsKentaro Hanashima, Haruhiro Komura
Life of this patent
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Abstract
A method for manufacturing a rare-earth iron-based ring magnet includes: (a) obtaining a rare-earth iron-based magnet powder; (b) preparing a compound; (c) forming a green body; (d) inserting the green body into a composite mold, setting the composite mold in a spark plasma sintering (SPS) apparatus, and degreasing the green body by energization at a predetermined current density while applying a pressure to the green body under reduced pressure to obtain a degreased body; and (e) sintering the degreased body by energization at a current density while applying a pressure to the degreased body to obtain a rare-earth iron-based ring magnet.
Claims7
A rare-earth iron-based ring magnet obtained by spark plasma sintering of a rare-earth iron-based magnet powder, wherein
- the rare-earth iron-based magnet powder is a magnetically isotropic rapidly quenched powder, includes a rare-earth element in an amount of 13 at % or more and 19 at % or less, and has a coercive force of 1500 kA/m or more,
- the rare-earth iron-based ring magnet has a radial crushing strength of 100 MPa or more and an initial demagnetization rate of less than 10%, and
- the rare-earth iron-based ring magnet has a carbon content of 2000 ppm or less and an average crystal grain size of less than 200 nm.
A method for manufacturing a rare-earth iron-based ring magnet, the method comprising:
- (a) pulverizing a magnetically isotropic rare-earth iron-based magnet ribbon produced by a rapid quenching method to obtain a rare-earth iron-based magnet powder;
- (b) mixing the rare-earth iron-based magnet powder and polystyrene to prepare a compound, and classifying the compound into a range of 20 μm or more and 125 μm or less;
- (c) filling a mold with the compound and pressurizing the mixture to form a green body;
- (d) inserting the green body into a composite mold, setting the composite mold in a spark plasma sintering (SPS) apparatus, and degreasing the green body by heating the green body under reduced pressure by energization at a current density of 250 A/cm2 or more and less than 550 A/cm2 while applying a pressure of 5 MPa or more and 15 MPa or less to the green body to obtain a degreased body;
- and
- (e) sintering the degreased body by heating the degreased body under reduced pressure by energization at a current density of 550 A/cm2 or more and 1050 A/cm2 or less while applying a pressure of 15 MPa or more and 200 MPa or less to the degreased body to obtain a rare-earth iron-based ring magnet, wherein
- the rare-earth iron-based magnet powder includes a rare-earth element in an amount of 13 at % or more and 19 at % or less.
Dependencies are inferred from the claim text.