GB832579A - Improved ferrous alloys - Google Patents

Abstract

A cast iron containing Al 1.0-5.0%, Mn 1.5-15.0% and Ni 0 to less than 2.0% has a structure in the "as-cast" condition comprising free graphite in a matrix of austenite and/or an acicular transformation constituent thereof, e.g. a matrix of austenite and bainite. The relative contents of Al and Mn may be adjusted to produce either a white or a gray cast iron. Any of the common alloying elements used in cast irons may be included, e.g. Cr, V, Mo, Cu, Ni, Co. Other elements such as Ca, Cl, Mg, Li, Na, K, Bi, Ti may also be present, e.g. Mg may be added to render the graphite carbon in spheroidal form. The cast iron may be heat treated. Thus an "as-cast" bainite structure may be converted to austenite by quenching from 1600-1900 DEG F. or even lower depending on the composition. An austenitic product may be precipitation hardened at 900-1200 DEG F. The alloy may be produced by introducing Al as a ladle addition, in the form of ingot or shot or as an alloy, e.g. with manganese, to high manganese metal melted in an electric furnace or acid lined cupola. Alternatively Al may be added as chunks mixed with Al powder and a metallic oxide. These constituents act as an exothermic mixture to assist alloying and to improve the fluidity of the melt. Specification 281,051 is referred to.