The Investigation of Cast Iron (4th Report) On the Freezing Process of Rapid Cooled Cast Iron

To study the process of freezing of cast iron, Fe-C alloys were melted and freezed rapidly, then examined their microstructures. When hypo-eutectic Fe-C alloys were freezed rapidly, there appeared in their microstructures austenite as primary, cementite as secondary, and then ledeburite. In the case of hyper-eutectic Fe-C alloys, cementite appeared as primary, in their microstructures but austenite was never found. But in hyper-eutectic cast iron, which contained sufficient quantity of Si or which was cooled slowly in proper manner dendritic austenite appeared among austenite-graphite eutectic. To study these peculiar structures, eleven binary eutectic alloy systems were examined. In the four systems of Al-Si,Al-Fe, Sn-Bi, and Cd-Bi, the same peculiar structures were obtained by rapid freezing. To explain such peculiar structures, the velocity of crystallization of each component was discussed, and the solubility of Fe in cementite was also discussed.