# US 2014/0152408 A1 · Rare-earth permanent magnet and method for manufacturing rare-earth permanent magnet > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152408 A1 - Document ID: US20140152408A1 - Status: Published application - Kind: A1 - Application number: 14/234,538 - Filed: 2013-03-08 - Published: 2014-06-05 - Earliest claimed: 2012-03-12 - Assignees: Nitto Denko Corporation - Applicants: Nitto Denko Corporation - Inventors: Tomohiro Omure; Katsuya kume; Toshiaki Okuno; Izumi Ozeki; Takashi Ozaki; Keisuke Taihaku; Takashi Yamamoto - Web page: https://patentgrep.com/patent/US20140152408A1 ## CPC - H01F 41/0266: {Moulding; Pressing (H01F41/0273 takes precedence; hard magnetic particles H01F1/06, H01F1/11)} - B22F 1/10: Metallic powder containing lubricating or binding agents; Metallic powder containing organic material - B22F 3/18: by using pressure rollers - B22F 7/04: with one or more layers not made from powder, e.g. made from solid metal - C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60} - C22C 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides} - H01F 1/0577: {sintered} - H01F 7/021: {Construction of PM (H01F7/0278 takes precedence; PM compositions H01F1/032)} - B22F 2003/185: {by hot rolling, below sintering temperature} - B22F 2301/355: Rare Earth - Fe intermetallic alloys - B22F 2998/10: Processes characterised by the sequence of their steps - B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract There are provided a rare-earth permanent magnet and a manufacturing method of a rare-earth permanent magnet capable of improving magnetic properties with drastically enhanced manufacturing efficiency. In the method, magnet material is milled into magnet powder. Next, the magnet powder and a binder are mixed to obtain a mixture 12. Next, the thus prepared mixture 12 is formed into a long-sheet-like shape on a supporting base 13 by hot-melt molding so as to obtain a green sheet 14. The thus formed green sheet 14 is heated to soften and a magnetic field is applied to multiple layers of the heated green sheet 14 for magnetic field orientation. The green sheet 14 subjected to the magnetic field orientation is sintered and thereby a permanent magnet 1 is obtained. ## Claims ### Claim 1 A manufacturing method of a rare-earth permanent magnet comprising steps of: milling magnet material into magnet powder; preparing a mixture of the magnet powder and a binder; obtaining a green sheet through thermally melting and forming the mixture into a sheet-like shape; heating the green sheet and simultaneously/subsequently applying a magnetic field to multiple layers of the heated green sheet, for magnetic field orientation; and sintering the green sheet subjected to the magnetic field orientation. ### Claim 2 (depends on 1) The manufacturing method of a rare-earth permanent magnet according to claim 1, wherein, in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, multiple layers of the green sheet are heated. ### Claim 3 (depends on 1) The manufacturing method of a rare-earth permanent magnet according to claim 1, wherein, in the step of obtaining a green sheet, a base that is continuously conveyed is coated with the mixture, so as to form the green sheet on the base, and in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, the green sheet is continuously conveyed together with the base. ### Claim 4 (depends on 3) The manufacturing method of a rare-earth permanent magnet according to claim 3 further comprising steps of: after the step of obtaining a green sheet, rolling up the green sheet around each of a plurality of first rolls, and drawing out the green sheet from each of the plurality of first rolls, and stacking up the drawn-out green sheet to form the multiple layers of the green sheet, so that the magnetic field is simultaneously applied to the multiple layers of the green sheet; and separating the multiple layers of the green sheet subjected to the magnetic field orientation back into each single layer of the green sheet, and rolling up the single layer of the green sheet around each of a plurality of second rolls. ### Claim 5 (depends on 3) The manufacturing method of a rare-earth permanent magnet according to claim 3, wherein, in the step of obtaining a green sheet, each of a plurality of bases drawn out from a plurality of third rolls is coated with the mixture, so as to form the green sheet on each of the plurality of bases, and in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, the green sheet on each of the plurality of bases is stacked to form multiple layers of the green sheet and the magnetic field is simultaneously applied to the multiple layers of the green sheet, and wherein the manufacturing method further comprises a step of: separating the multiple layers of the green sheet subjected to the magnetic field orientation back into each single layer of the green sheet, and rolling up the single layer of the green sheet around each of a plurality of fourth rolls. ### Claim 6 (depends on 3) The manufacturing method of a rare-earth permanent magnet according to claim 3, wherein, in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, the green sheet conveyed together with the base is made to pass through a solenoid charged with electric current. ### Claim 7 (depends on 1) The manufacturing method of a rare-earth permanent magnet according to claim 1, wherein, the binder is any one of thermoplastic resin, a long-chain hydrocarbon and a fatty acid methyl ester, or any mixture thereof, and in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, the green sheet is heated to a temperature equal to or higher than a glass-transition point or melting point of the binder. ### Claim 8 (depends on 1) The manufacturing method of a rare-earth permanent magnet according to claim 1, wherein, before the step of sintering the green sheet, the binder is decomposed and removed from the green sheet by holding the green sheet for a predetermined length of time at binder decomposition temperature in a non-oxidizing atmosphere. ### Claim 9 A rare-earth permanent magnet manufactured through steps of: milling magnet material into magnet powder; preparing a mixture of the magnet powder and a binder; obtaining a green sheet through thermally melting and forming the mixture into a sheet-like shape; heating the green sheet and simultaneously/subsequently applying a magnetic field to multiple layers of the heated green sheet, for magnetic field orientation; and sintering the green sheet subjected to the magnetic field orientation. ### Claim 10 (depends on 2) The manufacturing method of a rare-earth permanent magnet according to claim 2, wherein, in the step of obtaining a green sheet, a base that is continuously conveyed is coated with the mixture, so as to form the green sheet on the base, and in the step of heating the green sheet and simultaneously/subsequently applying a magnetic field, the green sheet is continuously conveyed together with the base.