# US 4,396,441 A · Permanent magnet having ultra-high coercive force and large maximum energy product and method of producing the same

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- Number: US 4,396,441 A
- Document ID: US4396441A
- Status: Granted
- Kind: A
- Application number: 06/318,402
- Filed: 1981-11-05
- Granted: 1983-08-02
- Earliest claimed: 1981-04-27
- Assignees: The Foundation: The Research Institute of Electric and Magnetic Alloys
- Inventors: Hakaru Masumoto; Kiyoshi Watanabe
- Web page: https://patentgrep.com/patent/US4396441A

## CPC

- H01F 7/02: Permanent magnets {[PM]}
- H01F 1/04: metals or alloys
- H01F 1/047: Alloys characterised by their composition
- H01F 41/0253: {for manufacturing permanent magnets}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES

## Abstract

The disclosed permanent magnet has a coercive force of 500 Oe or more, a idual magnetic flux density of 5 kG or more, and a maximum energy product of 2 MG. Oe or more. The magnet alloy consists essentially of platinum and iron, and has an initial state of homogeneous dispersion of .gamma..sub.1 phase of face-centered tetragonal type in a .gamma. phase matrix of face-centered cubic type. To produce the magnet, the alloy is heated at 900.degree. to 1,400.degree. C. for 1 minute to 100 hours for homogenizing solid solution treatment, and quenched in water or in air at a rate of 30.degree. C./minute to 2,000.degree. C./second.

## Claims

### Claim 1

A permanent magnet, said permanent magnet having a coercive force of not less than 500 Oe, a residual magnetic flux density of not less than 5 kG, and a maximum energy product of not less than 2 MG.Oe, said permanent magnet consisting of 33.5 to 47.5 atomic % (63.76 to 75.96 weight %) of platinum and the remainder of iron with less than 0.5% of impurities, said permanent magnet having a structure of homogeneous dispersion of .gamma..sub.1 phase of face-centered tetragonal type in a .gamma. phase matrix of face-centered cubic type.

### Claim 2

A method of producing a permanent magnet having an ultra-high coercive force and a large maximum energy product, comprising steps of heating an alloy at 900.degree. to 1,400.degree. C. for one minute to 100 hours so as to effect homogenizing solid solution treatment, which alloy consists of 33.5 to 47.5 atomic % of platinum and the remainder of iron with a small amount of impurities, and quenching said alloy in water or in air at a rate of 30.degree. C./minute to 2,000.degree. C./second.

### Claim 3

A method of producing a permanent magnet having an ultra-high coercive force and a large maximum energy product, comprising steps of heating an alloy at 900 to 1,400.degree. C. for one minute to 100 hours so as to effect homogenizing solid solution treatment, which alloy consists of 33.5 to 47.5 atomic % of platinum and the remainder of iron with a small amount of impurities, quenching said alloy, reheating said quenched alloy at 400.degree. to 700.degree. C. for one minute to 100 hours, and cooling the reheated alloy.

### Claim 4

A method of producing a permanent magnet having an ultra-high coercive force and a large maximum energy product, comprising steps of heating an alloy at 900.degree. to 1,400.degree. C. for one minute to 100 hours so as to effect homogenizing solid solution treatment, which alloy consists of 33.5 to 47.5 atomic % of platinum and the remainder of iron with a small amount of impurities, quenching said alloy in water or in air at a rate of 30.degree. C./minute to 2,000.degree. C./second, applying plastic working of not less than 90% to the thus quenched alloy by drawing into wire or rolling, reheating the worked alloy at 400.degree. to 700.degree. C. for one minute to 300 hours, and cooling the reheated alloy.