GB466048A - A process for making magnetic powder - Google Patents

Abstract

Magnetic powder is produced by forming an alloy in non-powdered form, containing not less than 82 per cent of iron and more than 4 per cent of silicon or aluminium, which increases the electric resistance and brittleness of the material, and then mechanically disintegrating the alloy to a size less than 50 microns. Up to 5 per cent of other materials such as carbon, phosphorus, sulphur, antimony, manganese, titanium, and arsenic may be present, of which up to 3 per cent may be mechanical admixtures, and the rest chemically bound in the alloy. Silicon or aluminium may be present in various amounts up to 15 per cent. The size of the particles may vary down to 0,2 microns. The disintegration is effected by ball, roller, or plate mills, or by mills of the type employing a pair of propellers between which the particles are disintegrated. Non-oxidizing, reducing, or catalytic substances may be present, such as acetone, amylacetate, carbon tetrachloride, hydrogen, nitrogen, carbon dioxide, or lighting gas, or 3 to 12 per cent of artificial resins in organic solvents may be employed. Graphite may be blown or floated off, and the current of gas through the mill may first remove the graphite, and then be increased to remove the iron, or separation may take place as they are carried out together. The application of the process to alloys containing respectively 90 per cent of iron and 10 per cent of silicon, 91 per cent of iron, 8 per cent of silicon, and 1 per cent of phosphorus (which may be prepared by heating ferro-silicon, iron phosphide, and spongy iron under borax at 1400 to 1600 DEG C.) 89,5 per cent of iron, 5 per cent of aluminium, 5 per cent of silicon, and 0,5 per cent of sulphur, (which may be ground at 300 to 400 DEG C.), and commercial silicon iron containing specified quantities of iron, carbon, silicon, manganese, phosphorus, sulphur, aluminium, and titanium, is described. The powder may be mixed with a binder in the manufacture of cores for high frequency coils.ALSO:Magnetic powder is formed by disintegrating an alloy containing not less than 82 per cent of iron and more than 4 per cent of silicon or aluminium to a size varying from 50 microns down to 0,2 microns, the powder being mixed with a thermoplastic insulating binder such as polystyrol, acetyl cellulose, nitrocellulose, or a phenolic resin for use as cores for high frequency coils. The binder occupies more than 30 per cent of the finished core. Iron alloys containing alloying ingredients in addition to silicon or aluminium are described.