Rare earth magnet and method for making same

• US 6,527,874 B2
• Filed: 07/10/2001
• Issued: 03/04/2003
• Est. Priority Date: 07/10/2000
• Status: Expired due to Term

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Sumitomo Seika Chemicals Company Limited
• Inventors: Li, Gang
• Primary Examiner(s): SHEEHAN, JOHN P
• Application Number:
  US09/901,104
• Publication Number:
  US 20020017338A1
• Time in Patent Office: 602 Days
• Field of Search: 148/301, 148/302, 148/101, 148/102, 148/103
• US Class Current: 148/301
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: H01F 1/0573 obtained by reduction or by hydrogen decrepitation or embrittlement
• CPC Class Codes: H01F 1/0577 sintered
• CPC Class Codes: H01F 1/0579 with exchange spin coupling between hard and soft nanophases, e.g. nanocomposite spring magnets
• CPC Class Codes: H01F 1/058 and IVa elements, e.g. Gd2Fe14C

Abstract

A rapidly solidified alloy is produced by quenching and solidifying a melt of an alloy having a general formula represented by (Fe_1-mT_m)_100-x-y-zQ_xR_yM_z where T denotes at least one kind of element selected from the group consisting of Co and Ni, Q denotes at least one kind of element selected from the group consisting of B and C, R denotes at least one kind of rare earth element, and M denotes at least one kind of element selected from the group consisting of Nb and Mo, and the mole fractions x, y, z, and m respectively satisfy 2≦x≦28 (atom %), 8≦y≦30 (atom %), 0.1 ≦z<1.0 (atom %), and 0≦m≦0.5 (atom %). The rapidly solidified alloy is then pulverized and sintered to manufacture a rare earth permanent magnet. The cooling rate is controlled to be in the range of 10² K/sec to 10⁴ K/sec, so that the alloy structure is uniformly fine and the added element M is uniformly dispersed.

Claims

1. A rapidly solidified alloy sintered magnet having a general formula represented by (Fe_1-mT_m)_100-x-y-zQ_xR_yM_z where T denotes at least one element selected from the group consisting of Co and Ni, Q denotes at least one element selected from the group consisting of B and C, R denotes at least one rare earth element, and M denotes Nb, and the mole fractions x, y, z, and m respectively satisfy 2≦

x≦

28 (atom %), 8≦

y≦

30 (atom %), 0.1≦

z<

1.0 (atom %), and 0≦

m≦

0.5 (atom %).

2. The rapidly solidified alloy sintered magnet of claim 1, wherein the cooling rate at which a melt of a material rare earth alloy is quenched to produce the rapidly solidified alloy is in a range of 10² K/sec to 10⁴ K/sec.

3. The rapidly solidified alloy sintered magnet of claim 1, wherein the alloy includes:

R₂F₁₄B compound crystal grains having a minor-axis size in a range between 0.1 μ

m and 10 μ

m and a major-axis size in a range between 5 μ

m and 500 μ

m; and

a R-rich phase exists uniformly at the grain boundaries of the crystal grains, the alloy having a thickness in a range between 0.03 mm and 10 mm.

4. A method for manufacturing a rare earth sintered magnet, comprising the steps of:

producing a rapidly solidified alloy by quenching and solidifying a melt of an alloy having a general formula represented by (Fe_1-mT_m)_100-x-y-zQ_xR_yM_z where T denotes at least one element selected from the group consisting of Co and Ni, Q denotes at least one element selected from the group consisting of B and C, R denotes at least one rare earth element, and M denotes Nb, and the mole fractions x, y, z, and m respectively satisfy 2≦

x≦

28 (atom %), 8≦

y≦

30 (atom %), 0.1≦

z<

1.0 (atom %), and 0≦

m≦

0.5 (atom %);

producing a powder of the rapidly solidified alloy, and

manufacturing a permanent magnet by sintering the powder of the rapidly solidified alloy.

5. The method of claim 4, wherein in the step of producing a rapidly solidified alloy the cooling rate is from 10² K/sec to 10⁴ K/sec.

6. The method of claim 5, wherein in the step of producing a rapidly solidified alloy the melt of the alloy is quenched by strip casting.

7. The method of any one of claims 4 to 6, further comprising the step of embrittling the rapidly solidified alloy by allowing the rapidly solidified alloy to occlude hydrogen and then release the hydrogen.

8. The method of claim 4, further comprising the step of grinding the permanent magnet.