GB454094A - Improvements in or relating to iron-chromium-aluminium alloys and methods of making the same - Google Patents

Abstract

An iron-chromium-aluminium alloy suitable for electric heating elements contains chromium in excess of 35,25 per cent, aluminium in excess of 5 per cent, the balance being substantially all iron; a preferred composition being 37 per cent chromium and 7 per cent aluminium. 0,5 per cent titanium acts as a grain refiner and 0,6 per cent silicon and 0,24 per cent manganese may be present. Iron or mild steel is melted in a high-frequency induction furnace, and is deoxidized by calcium silicide, and the required amount of chromium is added in the form of ferro-chromium, after which further deoxidation takes place. The bath is then covered with a slag free from boron or its compounds, and preferably consisting of equal parts of alumina and lime which is preheated to about 1500 DEG F. before use, and remains under the slag until the latter takes up the calcium or other oxides present. Aluminium chips, and, if required, a small amount of magnesium is added to deoxidize the slag, and return to the bath any iron or chromium oxides it may contain. The slag is then removed and the required amount of aluminium added. This may be done by pushing in an aluminium rod or wire which is melted below the surface of the bath. A second slag addition is then placed over the bath, and further additions of alloys may be made before the slag is removed, and the melt poured, a pouring temperature of about 2900 DEG F. being suitable for obtaining an alloy for use in heating elements. Specification 454,127 is referred to.