MALLEABLE IRON CONTAINING GRAPHITE NODULES

摘要

The invention is a malleable iron comprising about 250 to 400 nodules of graphite per square millimeter as observed in a photomicrograph at 100x, and a Brinell hardness of about 195 to 550 BHN. Preferably, the malleable iron further comprises sulfur and manganese wherein the manganese is present in an excess amount of at least 2 times the amount of sulfur plus 0,15 % and is formed by two separate quenching steps. The invention further comprises a method of preparing a malleable iron having a high nodule count comprising the steps of prenucleating a malleable iron casting at a temperature of about 600 to 900 DEG F for about 3 to 6 hours; austenitizing the prenucleated casting at about 1680 to 1740 DEG F for about 3 to 9 hours to form graphite nodules such that the malleable iron has about 250 to 400 nodules per mm<2>; and quenching the casting to form pearlite and a malleable iron made by this process.