The Effect of Silicon on the Formation of CO Blowholes during Solidification of Iron

Abstract

In order to clarify the effect of silicon addition on the formation of CO blowholes, an experimental study has been made of uni-directional solidification of iron at a solidification rate of about 5mm/min. The composition range explored was: C 0.1%, O 0.006-0.011% and Si 0.01-0.04%. The critical concentration of silicon for the formation of macroblowholes has been determined to be 0.022 to 0.025%. The influence of oxygen on the critical concentration of silicon was small. The effect of silicon on the formation of macroblowholes could be explained by postulating chemical equilibrium in Fe-C-Si-O melt in the interdendritic region. It is presumed that macroblowholes are formed with the similar mechanism as that in the case of no addition of silicon.