Abstract
Recently, automobile manufacturers are using high tensile steel for ensuring safety and lightening the car body. The manganese (Mn) content in steel scrap increases with the increase in the adoption rate of high tensile steel plate for the car body. Mn is an element that especially decreases the elongation of spheroidal graphite cast iron, and in the future, production of high ductility cast iron on as cast condition will become extremely difficult due to Mn increase. In this study, the method of manufacturing spheroidal graphite cast iron was examined without removal of Mn from high Mn steel scrap. Spheroidal graphite cast iron complying with JIS standard by the addition of rare earth element (RE) was producible. It was clarified that the recycling of high Mn steel scrap was possible. However, the elongation of spheroidal graphite cast iron decreased as the phosphorus (P) content increased. In particular, it should be noted that the compounding action with the minute amount of impurities contained in the high Mn steel scrap is large. The elongation of the spheroidal graphite cast iron could be increased by the addition of rare earth element before spheroidizing treatment.
