METHOD OF PRODUCING LARGE COMPONENT FROM AUSTEMPERED DUCTILE IRON ALLOY

摘要

PROBLEM TO BE SOLVED: To provide a method by which properties of a component formed of a ductile iron alloy and having thick sections can be promoted with an austempering process.;SOLUTION: In the method, when casting the ductile iron alloy 24 containing Fe, C, Si and alloying constituents, the casting is solidified at a rate that inhibits segregation of the alloying 24 constituents to grain boundaries of the casting, and so that the casting contains graphite nodules having a count of greater than 100 nodules per mm². The casting is then austempered by heating to an austenitization temperature to yield a microstructure having a single-phase matrix of austenite that contains carbon, and then quenching the casting to an austempering temperature. The casting is held at the austempering temperature for a duration sufficient to yield a microstructure whose matrix is mostly ausferrite and essentially free of martensite and pearlite.;COPYRIGHT: (C)2012,JPO&INPIT