GB985874A - An alloy cast iron - Google Patents

Abstract

An austenitic cast iron, which has been heat treated from the austenitic as-cast state to form a bainite or martensite structure, contains: .C.2.5-4%, .Ni.10-15%, .Mn.up to 1% as an incidental constituent, .Fe.and impurities and other incidental ..constituents, the remainder Provided that at least 7% of Ni is present the remainder of the nickel proportion may be provided by an amount of another element equivalent in austenitizing effect, such as copper or manganese; the copper not exceeding half the amount of nickel remaining and any manganese so added being in addition to the incidental amounts of this element. An example of a cast iron contains: .C.3.06%, .Si.1.37%, .P.0.03%, .S.0.019%, .Mn.0.97%, .Cr.0.83%, .Ni.12.8%, .and the balance Fe and impurities.. To effect transformation the cast iron may be held for a period at each of a successively decreasing series of temperatures with slow cooling in between each, e.g. it may be held at 850-600 DEG C. for 4 hours, then at 750 DEG C. and then at 650 DEG C. or 600 DEG C. Alternatively it may be held at a single elevated temperature for a period, e.g. at 600 DEG C. for 90 hours or 500 hours.