R-t-b-based alloy powder and method for producing same, and r-t-b-based sintered magnet and method for producing same

Patent metadata

Field	Value
Publication number	US-2017098497-A1
Application number	US-201515128137-A
Country	US
Kind code	A1
Filing date	Mar 23, 2015
Priority date	Mar 27, 2014
Publication date	Apr 6, 2017
Grant date	—

Abstract

An R-T-B based alloy powder which is composed of not less than 27.5 mass % and not more than 36.0 mass % of R (where R is at least one among the rare-earth elements and always includes either Nd or Pr), not less than 0.85 mass % and not more than 1.05 mass % of B (boron), not less than 0.1 mass % and not more than 2.5 mass % of element M (where M is at least one selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb and Bi), and a balance T (where T is: Fe; or Fe and Co), and in which powder satisfying the condition L/d≦5.39−1.07(a/b) accounts for 20% or more, given a ratio a/b between a longer diameter a and a shorter diameter b and a ratio L/d between a circumferential length L and an equivalent circular diameter d (i.e., a diameter of a circle of an identical area) of contour shapes resulting from two-dimensional projection of particles.

First claim

1 . An R-T-B based alloy powder which comprises:
not less than 27.5 mass % and not more than 36.0 mass % of R, where R is at least one among the rare-earth elements and always includes at least one of Nd and Pr); not less than 0.85 mass % and not more than 1.05 mass % of B (boron); not less than 0.1 mass % and not more than 2.5 mass % of element M, where M is at least one selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb and Bi); and a balance T (where T is: Fe; or Fe and Co), and in which powder satisfying the condition L/d≦5.39−1.07(a/b) accounts for 20% or more by number ratio, given a ratio a/b between a longer diameter a and a shorter diameter b and a ratio L/d between a circumferential length L and an equivalent circular diameter d, which is a diameter of a circle of an identical area, of contour shapes resulting from two-dimensional projection of particles.

2 . The R-T-B based alloy powder of claim 1 , wherein the powder satisfying the condition L/d≦5.39−1.07(a/b) accounts for 40% or more by number ratio.

3 . A sintered R-T-B based magnet which is obtained by aligning the R-T-B based alloy powder of claim 1 with an external magnetic field, and sintering the R-T-B based alloy powder.

4 . A production method of an R-T-B based alloy powder comprising:
a step of providing an alloy powder containing not less than 27.5 mass % and not more than 36.0 mass % of R (where R is at least one among the rare-earth elements and always includes at least one of Nd and Pr), not less than 0.85 mass % and not more than 1.05 mass % of B (boron), not less than 0.1 mass % and not more than 2.5 mass % of element M (where M is at least one selected from the group consisting of Al, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, Pb and Bi), and a balance T (where T is: Fe; or Fe and Co); and a step of pulverizing the alloy powder by introducing the alloy powder and a pulverization gas in a pulverization chamber, wherein the pulverization comprises attrition while circulating the alloy powder with a flow of the pulverization gas in the pulverization chamber, the pulverization step being performed so as to satisfy the condition that the pulverization gas to be introduced in the pulverization chamber has a gauge pressure of 0.65 MPa or more and that a residence time of the alloy powder in the pulverization chamber is 8 minutes or more, or satisfy the condition that the pulverization gas has a gauge pressure of 0.75 MPa or more and that the residence time is 5 minutes or more.

5 . The production method of claim 4 , wherein the pulverization step is performed so as to satisfy the condition that the pulverization gas has a gauge pressure of 0.75 MPa or more and that the residence time is 5 minutes or more.

6 . A production method of a sintered R-T-B based magnet comprising:
a step of obtaining an R-T-B based alloy powder by the method of claim 4 ; and a step of aligning the R-T-B based alloy powder with an external magnetic field and sintering the R-T-B based alloy powder.

7 . The R-T-B based alloy powder of claim 1 , wherein a D50 particle size of the powder is not less than 1.0 μm and not more than 5.5 μm.

8 . The R-T-B based alloy powder of claim 1 , wherein a D50 particle size of the powder is not less than 2.5 μm and not more than 5.0 μm.

9 . The R-T-B based alloy powder of claim 1 , wherein a D50 particle size of the powder is not less than 2.51 μm and not more than 4.63 μm.

Assignees

• Hitachi Metals Ltd

Inventors

• Ishii Rintaro

Classifications

• B22F1/06

  Metallic powder characterised by the shape of the particles (nanosized particles B22F1/054) · CPC title

• B22F1/14

  Treatment of metallic powder (mixing with lubricating or binding agents or with organic material B22F1/10) · CPC title

• B22F1/00

  Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties · CPC title

• B22F1/05

  Metallic powder characterised by the size or surface area of the particles · CPC title

• B22F1/0011

  Operations & Transport · mapped topic