Effect of high rate heat transfer during solidification of alloyed cast iron using water-cooled and sub-zero chills on mechanical behavior

Abstract

Hypoeutectic cast iron specimens cast using chills that are water-cooled and liquid-nitrogen cooled (cryogenic chilling) were compared with specimens of the same chemical composition which were sand cast without any chill. The solidification behavior, number of eutectic cell, grain size and the effects of these on mechanical properties like strength and fracture toughness were recorded and analyzed in this paper. It is revealed from the above investigation that sub-zero and water cool chilled cast irons exhibit severe under-cooling compared to normal sand cast iron. Thus, it is concluded from the investigation that nucleation conditions are completely altered during solidification but growth conditions prevail as usual. Therefore, under-cooling during solidification is considered to be responsible for the variation in eutectic cell size, grain size, microstructure and hence, the mechanical properties of the cast iron.