GB974494A - Improvements in methods of manufacturing magnetically anisotropic permanent magnets having crystalline structures - Google Patents

Abstract

<PICT:0974494/C6-C7/1> A magnetically anisotropic permanent magnet is manufactured from a permanent magnet alloy casting by inserting the casting 1, enclosed in a sheath of non-magnetic heat resistant material, into the turns of a high frequency magnetic induction coil 2, e.g. of water-cooled copper pipe, moving the casting relative to the coil, such as by lowering from a cord 4 at a rate of 2 mm./sec., so as to locally remelt one zone after another, e.g. to 1450 DEG C., thus destroying the original crystal structure and subsequently quenching each zone, e.g. at a distance h of 10 mm. from the re-molten zone, by contact with a cooling fluid such as air or water in a tank 3 so as to recrystallize the structure of the casting in the direction parallel with the magnetic lines of force induced by the coil. Several pieces of permanent magnetic material enclosed in the sheath may be subjected to the above successive heating and quenching treatment to obtain a single bar magnet which may be cut into several pieces. A suitable alloy consists of 13-40% Co, 10-20% Ni, 6-13% Al, 0-9% Cu, 0-8% Ti, 0-3% Si and balance Fe.