Importance

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Abstract

An additive for increasing the toughness of thin-wall iron castings is provided. The additive includes amounts of a non-ferrous metal oxide and a metal sulfide in which the non-ferrous metal has an affinity for oxygen less than that of iron, and the metal has an affinity for sulfur less than that of magnesium. The metals contained in the oxides and sulfides are also not alkali, alkali earth or rare earth metals to reduce the incidence of defect formation in the castings. The metal oxide and metal sulfide, when added to a cast iron melt react with magnesium added to the melt as a spheroidizing graphite element to form nucleation sites having a core of magnesium oxide surrounded by magnesium sulfide. These nucleation sites allow for increased nucleation of graphite, whether in vermicular or spheroidal form, such that the cross-section of the thin-wall iron casting is more uniform, thereby decreasing the amount of carbide formed in the casting and increasing the toughness of the casting.

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First Claim