Rare earth permanent magnet and method for producing rare earth permanent magnet

Patent metadata

Field	Value
Publication number	US-2017169922-A1
Application number	US-201415118117-A
Country	US
Kind code	A1
Filing date	Feb 12, 2014
Priority date	Feb 12, 2014
Publication date	Jun 15, 2017
Grant date	—

Abstract

Provided are a rare earth permanent magnet whose permanent magnetic properties are improved by making density of the magnet very high and a method for manufacturing a rare earth permanent magnet. Thus, magnet raw material is milled into magnet powder, and then a compound is formed by mixing the magnet powder thus milled with a binder. Next, the compound thus formed is subjected to hot-melt molding onto a supporting substrate so as to form a green sheet molded to a sheet-like shape. Thereafter, while the green sheet thus molded is softened by heating, magnetic field orientation is carried out by applying a magnetic field to the green sheet thus heated; and further, the green sheet having been subjected to the magnetic field orientation is calcined in non-oxidizing atmosphere, and then, sintering thereof is carried out at a sintering temperature to produce a permanent magnet having density of 95% or more.

First claim

1 . A rare-earth permanent magnet, wherein the rare-earth permanent magnet has a density of 95% or higher and is manufactured by a method comprising:
milling a magnet raw material into magnet powder; preparing a mixture of the magnet powder thus milled with a binder; carrying out magnetic field orientation to the mixture thus formed by applying a magnetic field; calcining under a non-oxidizing atmosphere the mixture thus orientated in a magnetic field; and sintering the mixture thus calcined by keeping the mixture at a sintering temperature.

2 . The rare-earth permanent magnet according to claim 1 , wherein in the calcining process of the mixture, after a temperature of the mixture is raised to a predetermined temperature at a prescribed temperature rising rate under a non-oxidizing atmosphere, the mixture is kept at the predetermined temperature for a certain period of time to remove the binder scatteringly.

3 . The rare-earth permanent magnet according to claim 2 , wherein the predetermined temperature is a decomposition temperature of the binder.

4 . The rare-earth permanent magnet according to claim 2 , wherein the temperature rising rate is 2° C./minute or less.

5 . The rare-earth permanent magnet according to claim 1 , wherein in the magnetic field orientation process, after the mixture is molded to a sheet-like shape, the magnetic field orientation is carried out to the mixture in the sheet-like shape.

6 . The rare-earth permanent magnet according to claim 5 , wherein in the case that the mixture is molded to a sheet-like shape, the mixture is molded to the sheet-like shape with melting the mixture by heating.

7 . The rare-earth permanent magnet according to claim 6 , wherein in the magnetic field orientation process, while heating the mixture which is molded to the sheet-like shape, a magnetic field is applied to the mixture thus heated to carry out the magnetic field orientation.

8 . The rare-earth permanent magnet according to claim 5 , wherein
the mixture is molded to a long sheet-like shape, and in the magnetic field orientation process, the magnetic field is applied in an in-plane and machine direction of the mixture which is molded to the long sheet-like shape, or in an in-plane and transverse direction thereof, or in a perpendicular direction to surface of the sheet.

9 . A method for manufacturing a rare-earth permanent magnet, the method comprising:
milling a magnet raw material into magnet powder; preparing a mixture of the magnet powder thus milled with a binder; carrying out magnetic field orientation to the mixture thus formed by applying a magnetic field; calcining under a non-oxidizing atmosphere the mixture thus orientated in a magnetic field; and producing the rare-earth permanent magnet having a density of 95% or higher by sintering the mixture thus calcined by keeping the mixture at a sintering temperature.

10 . The method for manufacturing a rare-earth permanent magnet according to claim 9 , wherein in the calcining process of the mixture, after a temperature of the mixture is raised to a predetermined temperature at a prescribed temperature rising rate under a non- oxidizing atmosphere, the mixture is kept at the predetermined temperature for a certain period of time to remove the binder scatteringly.

11 . The method for manufacturing a rare-earth permanent magnet according to claim 9 , wherein the predetermined temperature is a decomposition temperature of the binder.

12 . The method for manufacturing a rare-earth permanent magnet according to claim 10 , wherein the temperature rising rate is 2° C./minute or less.

13 . The method for manufacturing a rare-earth permanent magnet according to claim 9 , wherein in the magnetic field orientation process, after the mixture is molded to a sheet-like shape, the magnetic field orientation is carried out to the mixture in the sheet-like shape.

14 . The method for manufacturing a rare-earth permanent magnet according to claim 13 , wherein in the case that the mixture is molded to the sheet-like shape, the mixture is molded to the sheet-like shape with melting the mixture by heating.

15 . The method for manufacturing a rare-earth permanent magnet according to claim 14 , wherein in the magnetic field orientation process, while heating the mixture which is molded to the sheet-like shape, a magnetic field is applied to the mixture thus heated to carry out the magnetic field orientation.

16 . The method for manufacturing a rare-earth permanent magnet according to claim 13 , wherein
the mixture is molded to a long sheet-like shape, and in the magnetic field orientation process, the magnetic field is applied in an in-plane and machine direction of the mixture which is molded to the long sheet-like shape, or in an in-plane and transverse direction thereof, or in a perpendicular direction to surface of the sheet.

Assignees

• Nitto Denko Corp

Inventors

• Ozaki Takashi
• Kume Katsuya
• Okuno Toshiaki
• Ozeki Izumi
• Omure Tomohiro
• Taihaku Keisuke
• Yamamoto Takashi

Classifications

• C22C33/0278

  with at least one alloying element having a minimum content above 5% · CPC title

• B22F3/22

  for producing castings from a slip · CPC title

• H01F41/0253

  for manufacturing permanent magnets · CPC title

• H01F7/02

  Permanent magnets {[PM]} · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title