公开(公告)号：US10943717B2

公开(公告)日：2021-03-09

申请号：US15440755

申请日：2017-02-23

Applicant: TDK CORPORATION

Inventor： Masashi Miwa ,  Takurou Iwasa

IPC: H01F1/057 ,  B22F9/04 ,  B22F3/16 ,  C22C33/02 ,  B22D11/00 ,  B22F5/00 ,  C21D3/06 ,  C22C38/00 ,  C22C38/06 ,  C22C38/10 ,  C22C38/14 ,  C22C38/16 ,  H01F1/058

Abstract: An R-T-B based permanent magnet includes main phase grains composed of R2T14B type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. An average grain size of the main phase grains is 0.8 μm or more and 2.8 μm or less. The R-T-B based permanent magnet contains at least C and Zr in addition to R, T, and B. B is contained at 0.75 mass % or more and 0.88 mass % or less. Zr is contained at 0.65 mass % or more and 5.00 mass % or less. A formula (1) of 5.0≤[B]+[C]−[Zr]≤5.6 is satisfied, where [B] is a B content represented by atom %, [C] is a C content represented by atom %, and [Zr] is a Zr content represented by atom %.

公开(公告)号：US11081265B2

公开(公告)日：2021-08-03

申请号：US16465402

申请日：2017-11-30

Applicant: TDK CORPORATION

Inventor： Takurou Iwasa ,  Ryuji Hashimoto ,  Masashi Ito

IPC: H01F1/055 ,  C22C33/02 ,  C22C38/00 ,  C22C38/10 ,  H01F1/053

Abstract: A rare-earth sintered magnet contains main phase crystal grains having an Nd5Fe17-type crystal structure, includes R and T (where R represents one or more rare-earth elements that essentially include Sm and T represents Fe or one or more transition metal elements that essentially include Fe and Co), and wherein the compositional ratio of R is 20-40 at % and the remaining portion is substantially T; the remaining portion other than R is substantially only T or only T and C; and when the main phase crystal grains' average grain size in one cross-sectional surface of the rare-earth sintered magnet is defined as Dv, while grain size of individual main phase crystal grains is defined as Di, Dv is at least 1.0 μm, and the main phase crystal grains' area ratio that satisfy 0.7Dv≤Di≤2.0Dv is at least 80% with respect to the area of a cross-sectional surface of the rare-earth sintered magnet.

公开(公告)号：US10522276B2

公开(公告)日：2019-12-31

申请号：US15015800

申请日：2016-02-04

Applicant: TDK CORPORATION

Inventor： Masashi Miwa ,  Takurou Iwasa

IPC: B22F3/10 ,  H01F7/02 ,  H01F1/057

Abstract: An R-T-B based sintered magnet has a high coercivity even if the carbon content becomes high accompanying the micronization of the finely pulverized particles of the raw material. The R-T-B based sintered magnet includes an R-T-B based compound as main phase grains, wherein, the R-T-B based sintered magnet contains 0.1 mass % to 0.3 mass % of C, and an R—Ga—C concentrated part exists in the grain boundary formed between or among two or more adjacent main phase grains, and the concentrations of R, Ga and C in the R—Ga—C concentrated part are higher than those in the main phase grains respectively.

公开(公告)号：US10388443B2

公开(公告)日：2019-08-20

申请号：US15015462

申请日：2016-02-04

Applicant: TDK CORPORATION

Inventor： Masashi Miwa ,  Takurou Iwasa ,  Haruna Nakajima

IPC: H01F1/153 ,  H01F1/053 ,  H01F1/08 ,  H01F1/057

Abstract: The present invention provides an R-T-B based sintered magnet having an R-T-B based compound as main phase grains, wherein, the content of Zr contained in the R-T-B based sintered magnet is 0.3 mass % to 2.0 mass %, the main phase grains have Zr, and the R-T-B based sintered magnet have main phase grains with the mass concentration of Zr at the edge portion of the main phase grain being 70% or less of that at the central portion of the main phase grain at the cross-section of the main phase grain.

公开(公告)号：US10672546B2

公开(公告)日：2020-06-02

申请号：US15440660

申请日：2017-02-23

Applicant: TDK CORPORATION

Inventor： Masashi Miwa ,  Takurou Iwasa ,  Tamotsu Ishiyama

IPC: H01F1/057 ,  B22F9/04 ,  B22F3/16 ,  B22F3/24 ,  C22C33/02 ,  C22C33/04 ,  C22C38/00 ,  C22C38/06 ,  C22C38/10 ,  C22C38/14

Abstract: An R-T-B based permanent magnet includes main phase grains composed of R2T14B type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. The magnet contains at least C, Ga, and M selected from Zr, Ti, and Nb in addition to R, T, and B. B is contained at 0.71 mass % to 0.88 mass %. C is contained at 0.15 mass % to 0.34 mass %. Ga is contained at 0.40 mass % to 1.40 mass %. M is contained at 0.25 mass % to 2.50 mass %. A formula (1) of 0.14≤[C]/([B]+[C])≤0.30 and a formula (2) of 5.0≤[B]+[C]−[M]≤5.6 are satisfied, where [B], [C], and [M] are respectively a content of B, C, and M by atom %.

公开(公告)号：US10529473B2

公开(公告)日：2020-01-07

申请号：US15440667

申请日：2017-02-23

Applicant: TDK CORPORATION

Inventor： Takurou Iwasa ,  Masashi Miwa

IPC: H01F1/053 ,  B22F9/04 ,  B22F3/12 ,  B22F5/00 ,  C21D3/06 ,  C22C38/00 ,  C22C38/06 ,  C22C38/10 ,  C22C38/14 ,  C22C38/16 ,  H01F1/06

Abstract: An R-T-B based permanent magnet includes R-T-B based compounds as main-phase crystal grains. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. A two-grain boundary is contained between the two adjacent main-phase crystal grains. An average grain size of the main-phase crystal grains is 0.9 μm or more and 2.8 μm or less. A thickness of the two-grain boundary is 5 nm or more and 200 nm or less.