Effects of Manganese and Copper on Microstructure and Mechanical Properties of As-cast Spheroidal Graphite Cast Iron Containing Rare Earth Elements

摘要

In this study, the effects of various amounts of manganese (Mn) and copper (Cu) addition on the microstructure and mechanical properties of spheroidal graphite cast irons containing 0.05mass% sulfur (S) and 0.2mass% rare earth elements (RE) were investigated. As a result, tensile strength and Brinell hardness increased and elongation decreased with increasing Mn and Cu addition. Especially, high tensile strength of 900MPa or more was obtained by 1.5mass% to 3.0mass%Cu addition. As for microstructure of 3mm thickness specimens, the chill structure did not appear at 1.5mass%Mn and 2.0mass%Cu addition. However, the chill structure appeared, when the amounts of Mn and Cu addition reached to 2.0mass% and 3.0mass%, respectively. EPMA analysis showed that complex sulfide of RE and magnesium (RE,Mg)S as a nucleus for graphite nucleation formed in a graphite spheroid.