Effect of rare earth elements and sulfur on microstructure and chilling tendency in flake graphite cast iron

Abstract

A flake graphite cast iron was produced to determine the effect of rare earth (RE) additions on the microstructure and chilling tendency of low (0.01–0.03%S) and high (0.03–0.1%S) sulfur level content. Cooling curves and microstructures of base iron and RE-added flake graphite cast iron were also investigated. In this study, various ratios of RE/S were used to find stoichiometric balance of RE/S for optimum condition of type A graphite forming range and maximum chill reduction. To clearly identify the chilling tendencies, high quality pig iron was used. All experiments were conducted without post inoculation in order to clarify the effects of rare earth in the cast iron. It is clear that RE/S ratio about 2.5 showed type A graphite and chill depth at minimum level. It is considered that this RE/S favors the formation of RE-sulfides which act as substrates for graphite nucleation and thus decrease chilling tendency.

Keywords:

• rare earth
• cast iroa graphite morphology
• chilling tendency