63 - Achieving Higher Strength and Toughness in Heavy-Section Ductile Iron Castings

Abstract:

Experimental heat treatments involving interrupted quenching from an intercritical (IC) temperature showed that discrete lenticular austenite grains nucleate at the ferrite grain boundaries and grow into the proeutectoid ferrite grains, resulting in the formation of a unique “lamellar” austenite in ferrite. Upon aircooling, the austenite transforms to pearlite, producing acicular pearlite in ferrite. In light section castings, the fine-grained pearlite-ferrite structure has displayed substantially higher mechanical properties than those of as-cast structures. A study was conducted to determine whether intercritical heat treatment could be applied to heavy-section ductile iron components.