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

摘要

This study investigated the effects of various amounts of manganese (Mn) and copper (Cu) addition on the microstructure and mechanical properies of spheroidal graphite cast irons containing 0.05 mass percent sulfur (S) and 0.2 mass percent rare earth elements (RE). Tensile strength and Brinell hardness increased and elongation decreased with increasing Mn and Cu addition. Especially, high tensile strength of 900 MPa and above was obtained in specimens addded with 1.5 mass percent to 3.0 mass percent Cu. For 3 mm thick microstructure specimens, the chill structure disappeared at the addition of 1.5 mass percent Mn and 2.0 mass percent Cu. However, the chill structure appeared when the amount of Mn and Cu added reached 2.0 mass percent and 3.0 mass percent respectively. EPMA analysis showed that complex sulfide of RE and magnesium (RE, Mg) S as a nucleus for graphite nucleation formed in a graphite spheroids.