Method for producing sintered rare-earth magnet, sintered rare-earth magnet, and material for same

Patent metadata

Field	Value
Publication number	US-9640305-B2
Application number	US-201013511465-A
Country	US
Kind code	B2
Filing date	Nov 18, 2010
Priority date	Nov 26, 2009
Publication date	May 2, 2017
Grant date	May 2, 2017

Abstract

A method for producing a sintered rare-earth magnet characterized by sintering a raw material that includes a ribbon-shaped polycrystalline phase with an average grain size of 10 to 200 nm fabricated by rapid solidification of an alloy melt having a rare-earth magnet composition, and a low-melting point phase formed on the surface of the polycrystalline phase and having a melting point lower than the polycrystalline phase.

First claim

What is claimed is:

1. A method for producing a sintered rare-earth magnet comprising:
preparing a ribbon comprising a polycrystalline phase including crystal grains with an average grain size of 10 to 200 nm by rapidly solidifying an alloy melt having a rare-earth magnet composition;
forming a low-melting point phase having a melting point lower than the polycrystalline phase on a surface of the ribbon; and
sintering a raw material comprising the ribbon and the low-melting point phase,
wherein the rapidly solidifying the alloy melt is performed by a single-roll process in which a single roll is used, and the surface of the ribbon on which the low-melting point phase is formed is opposite to a surface in contact with the single roll,
the low-melting point phase is not more than 3% by volume fraction of the polycrystalline phase, and
a thickness of the low-melting point phase is 50 nm to 1000 nm.

2. The method according to claim 1 , wherein the average grain size of the crystal grains contained in the polycrystalline phase is 10 to 50 nm.

3. The method according to claim 1 , wherein the sintering of the raw material includes pulverizing the raw material to obtain a powder, and sintering the powder.

4. The method according to claim 1 , wherein, immediately after the alloy melt comes in contact with an outer circumferential surface of the single roll, a main crystalline phase begins to nucleate within the alloy melt and the crystalline phase gradually grows in stages; then a grain boundary phase forms to form a polycrystalline phase, and a melt portion remains only on the side of the free surface; and finally the melt portion on the side of the free surface solidifies to become the low-melting point phase.

5. The method according to claim 1 , wherein the low-melting point phase is a final solidification phase.

6. A raw material for a sintered rare-earth magnet comprising:
a ribbon comprising a polycrystalline phase including crystal grains with an average grain size of 10 to 200 nm; and
a low-melting point phase formed on a surface of the ribbon and having a melting point lower than the polycrystalline phase,
wherein the ribbon is prepared by rapidly solidifying an alloy melt having a rare earth magnet composition by a single-roll process in which a single roll is used, and the surface of the ribbon on which the low-melting point phase is formed is opposite to a surface in contact with the single roll,
the low-melting point phase is not more than 3% by volume fraction of the polycrystalline phase, and
a thickness of the low-melting point phase is 50 nm to 1000 nm.

7. The raw material according to claim 6 , wherein the average grain size of the crystal grains contained in the polycrystalline phase is 10 to 50 nm.

Assignees

• Shoji Tetsuya
• Sakuma Noritsugu
• Kishimoto Hidefumi
• Toyota Motor Co Ltd

Inventors

• Shoji Tetsuya
• Sakuma Noritsugu
• Kishimoto Hidefumi

Classifications

• H01F1/086

  sintered · CPC title

• H01F1/0572 Primary

  with a protective layer · CPC title

• Y10S977/838

  Magnetic property of nanomaterial · CPC title

• H01F41/0266

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

• H01F1/061

  with a protective layer · CPC title