R-T-B based alloy strip, and R-T-B based sintered magnet and method for producing same

Patent metadata

Field	Value
Publication number	US-9620268-B2
Application number	US-201214350438-A
Country	US
Kind code	B2
Filing date	Oct 11, 2012
Priority date	Oct 13, 2011
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

An R-T-B based alloy strip including columnar crystals of an R 2 T 14 B phase, wherein in a cross-section along the thickness direction, columnar crystals extend out in a radial fashion from the crystal nuclei, the R-T-B based alloy strip satisfying the following inequality (1), where D 1 and D 2 are, respectively, the average value for the lengths of the columnar crystals on one side and the average value for the lengths on the other side that is opposite the one side, in the direction perpendicular to the thickness direction of the cross-section.

0.9/1.1≦ D 2 /D 1 ≦1.1/0.9  (1)

First claim

The invention claimed is:

1. An R-T-B based alloy strip comprising columnar crystals of an R 2 T 14 B phase, wherein R represents at least one element selected from the group consisting of rare earth elements, T represents at least one of iron and cobalt, and B represents boron,
wherein in a cross-section along the thickness direction,
columnar crystals extend out in a radial fashion from the crystal nuclei,
the R-T-B based alloy strip satisfying the following inequality (1), where D 1 and D 2 are, respectively, the average value for the lengths of the columnar crystals on one side and the average value for the lengths on the other side that is opposite the one side, in the direction perpendicular to the thickness direction of the cross-section,
1 ≦D 2 /D 1 ≦1.1  (1).

2. The R-T-B based alloy strip according to claim 1 , satisfying the following inequalities (2) and (3), where D AVE and D MAX are, respectively, the average value and the maximum value for the lengths of the columnar crystals in the direction perpendicular to the thickness direction in the cross-section
1.0 μm≦ D AVE ≦3.0 μm  (2)

1.5 μm≦ D MAX ≦4.5 μm  (3).

3. The R-T-B based alloy strip according to claim 1 ,
containing an R-rich phase in which the R content is higher than the R 2 T 14 B phase based on mass,
the percentage of the number of R-rich phases with lengths of no greater than 1.5 μm in the direction perpendicular to the thickness direction, with respect to the total number of R-rich phases, in the cross-section, being 90% or greater.

4. An R-T-B based sintered magnet obtained by molding and firing alloy powder obtained by grinding the R-T-B based alloy strip according to claim 1 .

5. A method for producing an R-T-B based sintered magnet, the method comprising the steps of:
grinding the R-T-B based alloy strip according to claim 1 to prepare an alloy powder, and
molding and firing the alloy powder to produce the R-T-B based sintered magnet.

6. A method for producing an R-T-B based sintered magnet, the method comprising the steps of:
grinding the R-T-B based alloy strip according to claim 2 to prepare an alloy powder, and
molding and firing the alloy powder to produce the R-T-B based sintered magnet.

Assignees

• Tdk Corp

Inventors

• Tsubokura Taeko
• Kato Eiji
• Ishiyama Tamotsu
• Jingu Nobuhiro
• Ishizaka Chikara

Classifications

• C22C2202/02

  Magnetic · CPC title

• C22C38/16

  containing copper · CPC title

• H01F41/0266

  Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11) · CPC title

• C22C38/06

  containing aluminium · CPC title

• H01F1/086

  sintered · CPC title