Nodulization of graphite in cast iron by addition of plastic resin

Abstract

An addition of active metals such as magnesium and cerium to molten cast iron gives rise to solidified spheroidal graphite. Such alloys are called nodular cast iron, spheroidal graphite cast iron or ductile cast iron. However, the manufacturing of nodular cast iron has some issues including a difficulty in process control, a hazardous working environment and the unstable price of rare earth metals. To build an alternative way to produce nodular cast iron, this study examined the feasibility of nodulizing graphite by using plastic resin instead of active metals. It is presumed that the contact of plastic resin with molten cast iron results in its thermal decomposition, generating gas and carbon clusters that act as nuclei for precipitation of nodular graphite. Laboratory tests demonstrated a partial nodulization of graphite precipitating into cast iron that came in contact with a polyethylene sheet during the process of solidification. This result suggests an application potency of waste plastics for controlling microstructure of ferrous alloys, contributing to promotion of their recycling.