Growth of Eutectic Austenite in Free Graphite Cast Irons

Abstract

The present work investigates the growth of the eutectic austenite of hypereutectic free graphite cast irons of different graphite morphology. The study was based on the analysis of several samples obtained from a highly hypereutectic cast iron melt. A hypereutectic melt was used in order to ensure the absence of proeutectic austenite. With the aim of obtaining samples of different graphite morphology but nearly identical chemical composition, the melt was nodularized by using a standard procedure, and different samples were cast after various fading periods. Through this procedure, spheroidal, vermicular and flake graphite samples were obtained The results show that the eutectic austenite grows dendritically in all samples investigated. Nevertheless, significant differences were found in the size of the solidification units (grains) and in the microsegregation patterns as the graphite morphology changes from spheroidal to flake.