| 摘要 |
An alloy is proposed for use in making permanent magnets. The alloy has the following composition by weight: -Chromium 22.5 to 25.5% -Cobalt 15.0 to 17.5% -Molybdenum 2.0 to 4.0% -Silicon 0.1 to 0.8% - Oxygen less than 0.10% -Effective carbon less than 0.06% - Remainder iron and unavoidable impurities, - where effective carbon is defined as carbon content plus 0.86 times nitrogen content. In a method of manufacturing permanent magnets, a workpiece is made of the alloy, for example by suction or extrusion casting, and the workpiece is subjected to a heat treatment comprising: (a) a homogenizing annealing for 15 minutes to 3 hours at 1230 DEG C. to 1280 DEG C., followed by quenching in water or oil; and (b) a thermo-magnetic treatment for 10 to 30 minutes at 720 DEG C. to 740 DEG C., followed by the application for 10 to 120 minutes in a preferred axial direction of a magnetic field of 80 to 240 kA/m at a temperature of 630 DEG C. to 650 DEG C., followed by cooling in air. The workpiece is then optionally age-hardened in the following three stages: i maintaining the workpiece at 590 DEG C. to 625 DEG C. for 0.25 to 10 hours ii maintaining the workpiece at 555 DEG C. to 585 DEG C. for 0.5 to 30 hours, and iii maintaining the workpiece at 500 DEG C. to 540 DEG C. for 0 to 50 hours.
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