GB496730A - Improvements in or relating to the production of alloys for permanent magnets - Google Patents

Abstract

The magnetic properties of copper-nickel-iron alloys containing more than 50 per cent of copper nickel for use as permanent magnets are improved by cold rolling the alloys to a degree which reduces their cross-section by more than 40 per cent, and preferably more than 70 per cent, and then heat-treating the rolled alloys at 500-750 DEG C. The alloys may be subjected to a preliminary shaping with or without an incandescent heating and quenching prior to the cold rolling. The alloys may be annealed at 500-700 DEG C. preferably after the quenching and before the cold rolling and may contain also up to 5 per cent of cobalt and up to 2 per cent of beryllium. As applied to an alloy containing 15-25 per cent of nickel, 10-25 of iron and 50-75 of copper, the alloy is subjected to an incandescent heating above 1000 DEG C., quenched, annealed at 500-700 DEG C., cold rolled and finally annealed at 500-700 DEG C. In a particular example an alloy containing 20 per cent of nickel, 20 of iron and 60 of copper was cast in bars 43 mm. thick and then rolled down to 23 mm. diameter. The bars were then heated at 1050 DEG C. for 10 hours, rolled down to a diameter of 10,7 mm., annealed for one hour at 600 DEG C. and cooled in air.