Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1992-10-16
1994-10-04
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148120, 148121, H01F 100
Patent
active
053523024
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a method of producing a rare-earth permanent magnet and, more particularly, to such method for producing a R--Fe--B rare-earth permanent magnet, that makes a cast alloy magnetically anisotropic by hot plastic working.
2. Background Art
Typical permanent magnets used currently include a cast Alnico magnet, a Ferrite magnet and a rare-earth-transition metal magnet. Considerable work has been done especially on the R--Fe--B permanent magnet since it is a permanent magnet having very high coersive force and energy product.
Conventional methods for producing these rare-earth-iron (transition metal) permanent magnets of high performance include those given below.
(1) The publication of Japanese Patent Laid-Open Publication No.59-46008, and M. Sagawa, S. Fujimura, N. Togawa, H. Yamamoto and Y. Matsuura; J. Appl. Phys. Vol. 55(6), 15 March 1984, P2083, etc. disclose a permanent magnet which is featured by being an anisotropic sintered body comprising 8-30 atomic % of R (here R is at least one of rare-earth elements including Y), 2-28% of B, and the rest of Fe, and its production method by sintering process which is based on powder metallurgy. In the sintering process, an alloy ingot prepared by melting and casting, is crushed into a magnetic powder of an appropriate particle size (several .mu.m). The magnetic powder is kneaded with an organic binder which is a molding aid, and molded by compaction molding under a magnetic field. The green body is sintered in an argon at a temperature around 1100.degree. C. for 1 hour, then quickly cooled to room temperature. The coersive force is enhanced by carrying out a heat treatment at a temperature around 600.degree. C. after the sintering. As for the heat treatment of the sintered magnet, effects of step heat treatment are disclosed in the publication of Japanese Patent Laid-Open Publication No. 61-217540, and in the publication of Japanese Patent Laid-Open Publication No. 62-165305 etc.
(2) The publication of Japanese Patent Laid-Open Publication No. 59-211549 and R. W. Lee; Appl. Phys. Lett. Vol. 46(8), 15 April 1985, P 790 discloses that a rare-earth iron magnet is produced by making a rapidly-quenched ribbon having a thickness of around 30 .mu.m by melt spinning process using a melt-spinning apparatus which is generally used for producing an amorphous alloy, and by bonding the obtained thin ribbon with resin.
(3) Furthermore, the publication of Japanese Patent Laid-Open Publication No. 60-100402 and the above-mentioned paper of R. W. Lee disclose a production method of an anisotropic permanent magnet by high-temperature working, wherein the permanent magnet is an iron-rare-earth metal alloy, and the production process comprises high-temperature working of an amorphous or a fine crystalline solid material containing iron, neodymium and/or praseodymium and boron, production of a plastically deformed body, cooling the obtained body, and making the resulted body show magnetic anisotropy and permanent magnetic properties.
In this method of producing the magnets, the rapidly quenched ribbon or thin ribbon fragment described in the paragraph (2) is densified by hot presssing at around 700.degree. C. in vacuum or in an innert gas atmosphere, then upsetting (die upset) is carried out until the thickness becomes 1/2 of the original thickness, so that the axis of easy magnetization is aligned along with the pressing direction and anisotropy is rendered. The publication of Japanese Patent Laid-Open Publication No. 2-308512 discloses a method in which a R--Fe--B alloy powder produced by rapidly quenching process is consolidated and warm plastic deformation is carried out to render anisotropy, and molded into an arc shape again under warm condition.
(4) The publication of Japanese Patent Laid-Open Publication No. 62-276803 discloses a method of producing a rare-earth iron permanent magnet which is featured by melting and casting an alloy made of 8-30 atomic % of R (here R is at least one of rare-earth elements including Y), 2-
REFERENCES:
patent: 4710239 (1987-12-01), Lee et al.
patent: 4780226 (1988-10-01), Sheets et al.
patent: 4921551 (1990-05-01), Uernia et al.
patent: 5125988 (1992-06-01), Akioka et al.
Akioka Koji
Arai Akira
Ihara Seiji
Kobayashi Osamu
Takagi Fumio
Seiko Epson Corporation
Sheehan John P.
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