GB583411A - Improvements in or relating to the manufacture of permanent magnets - Google Patents

Abstract

In the manufacture of an anisotropic permanent magnet, an iron alloy containing 6-11 per cent. of aluminium, more than 20 and up to 30 of nickel, and 14-28 of cobalt is subjected to the action of a magnetic field while it is cooling from 1,200-1,280 DEG C. down to 700-600 DEG C. and then to a precipilation or ageing treatment, e.g. by heating it to 450-700 DEG C. and holding it there for the necessary time to obtain the desired magnetic properties, before it is finally magnetised. The alloy may also contain up to 5 per cent. of copper, up to 5 of titanium, up to 5 of silicon or up to 1 of zirconium or a total of two or more of such elements up to 10 per cent. The cooling may be effected at an average rate of 1/2 DEG -15 DEG C. per second as for e.g., the maximum cooling rate for an aluminium cobalt nickel alloy containing 21 per cent. of nickel is 10 DEG C. per second, for an alloy containing silicon at less than 10 DEG C. per second and for an alloy containing zirconium less than 1 DEG C. per second. The copper and cobalt may be introduced into the alloy as described in Specification 450,431. The ageing may be carried out in stages, the first in the upper region of the range, e.g., 5-8 hours at a temperature above 600 DEG C., e.g., 650 DEG C. and the second at a lower temperature, below 600 DEG C., e.g., 550 DEG C. for 10-20 hours. Specifications 478,127, 522,731, 569,654 and 581,402 also are referred to.