GB572409A - Improvements in or relating to the manufacture of ferro-magnetic material - Google Patents

Abstract

572,409. Magnetizing apparatus. OLIVER, D. A., and JESSOP & SONS, Ltd., W. Sept. 21, 1940, No. 14436. [Class 35] [Also in Group II] An isotropic permanent magnet material in which the magnet characteristics are enhanced in different directions in parallel planar zones is produced by subjecting the material during cooling from a temperature above to one below the Curie point in a magnetic field and by maintaining relative rotation between the material and the field, during cooling past the Curie point, about an axis at right angles to the planar zones in which the multi-directional characteristics of augmented value are to be produced. The material may be an iron-base alloy containing 13-30 per cent of cobalt, 8-20 of nickel and 5-10 of aluminium with or without up to 6 of copper, up to 6 and up to 4 of titanium. When the material is rotated in the field, the material in the form of a disc 18 is supported in a cage-like carrier consisting of spiders 22, 23 connected by rods 24 which are in two portions connected by spigot and socket joints 25. The spider 22 is provided with a flat trunnion 26' carried in bearings 20 in an end plate 12 and the spider 23 with a spindle 27 carried in bearings 20 in an end plate 16 and provided with a pulley 28. The carrier is mounted between polepieces 10, 11 which are enclosed by plates of non-magnetic material, the plate 12 and the side plates being secured by screws to the poles, the other plate 16 being detachably secured in place by dowels 17. The poles are comprised in a bipolar system which may be energized by continuous or alternating current passing through two coils, one on each side of the apparatus referred to above or by a permanent magnet. In a modification, Fig. 3, the disc 31 may be provided with a square hole 32, the corners of which are engaged by heat resistant supports 34 which project from a central portion of a mandrel 33 which is mounted in the bearings 20, 21, Fig. 1. In a further modification, discs of the material to be treated are mounted with intervening insulating washers, on the enlarged central portion of a mandrel and are held in position by screws fitting a screwed part of the central portion. In another modification, the magnetic field rotates round a stationary cylinder or ring 44, Fig. 8, of the magnet material, and the apparatus used comprises a circular yoke 45 with three polepieces 46 provided with windings 47 energized by a three-phase alternating current system. In an example, a disc consists of an iron base alloy containing 24.9 per cent of cobalt, 11.1 of nickel, 6.8 of aluminium, 2.3 of copper, 0.3 of carbon, and 2.1 of titanium, was heated to 1200‹ C., placed in the apparatus shown in Fig. 1 and rotated at a speed of 600 revolutions per minute in a magnetic field strength of 5000 oersteds until cooled to about 600‹ C.