GB350603A - Improvements in the manufacture of ferro-nickel magnetic alloys - Google Patents

Abstract

Magnetic alloys consisting mainly of iron and nickel have their permeability increased and electrical resistance decreased by melting the constituent metals of high purity in contact with an amount of carbon sufficient to prevent oxidation and insufficient to raise the carbon content above 0,05 per cent. The alloys may contain 35-95 per cent of nickel, preferably 45-55 or 70-80 per cent, and may contain also about 1 per cent of manganese and in some cases up to 10 per cent of copper, with the balance mainly iron. The total of the usual impurities such as carbon, silicon, sulphur, phosphorus should not exceed 0,50 per cent. In making the alloys, good grades of iron and nickel are melted with enough charcoal to produce 0,02-0,03 per cent of carbon in the molten metal. On melting the metal is covered with a slightly reducing slag consisting preferably of lime, fluorspar, and tarcoke, the coke being graded or regulated so as not to carburize the metal, and about 0,25 per cent of manganese is added under the slag to assist in desulphurizing and dephosphorizing the melt. The temperature is raised and an alloy of silicon with an alkaline-earth metal or with a heavy metal such as zirconium, tungsten, or uranium, or with magnesium, is added to deoxidize. A calcium or zirconium alloy may be used for the 45-55 per cent nickel alloys and a magnesium alloy for the 70-80 per cent nickel alloys. The magnesium alloy is conveniently added in alloy with a heavy metal, as for example a nickel alloy containing 25 per cent of silicon and 5 per cent of magnesium.