Part Ⅰ of the paper describes the conversion of cast steel wheels for heavy-duty trucks to as-cast ferritic ductile iron wheels. Electric arc furnaces for melting steel were used to produce base iron for ductile treatment. The ductile wheels were produced using then existing steel foundry facilities. The steel wheels were gradually converted to ductile iron (DI) wheels. Initially, the ductile production was started with the sandwich treatment. The 25-minute short-cycle cooling system was innovated for ductile production on the Herman, mold line with modified shakeout system. Within a year, the preplanned extension of SPO mold line in the gray iron foundry was completed. The extension was needed to provide longer cooling time for ductile castings prior to shakeout. A 60-ton induction holder was installed to hold the base iron. The molds for ductile castings were made at the SPO mold line. The electric arc furnaces continued to produce base iron, but the iron was held in a 60-ton holder prior to treatment. The sandwich treatment was replaced by the tundish treatment. An alloy station was also installed. The Herman molding unit in the steel foundry was shut down after all the steel wheels were converted into DI wheels. Part Ⅱ of the paper describes the conversion of gray iron into ductile iron. Cupola-melted gray iron was converted into the base iron by changing the cupola charge. Ductile treatment was done by feeding 13 mm diameter cored wire containing 25% magnesium and 75% ferrosilicon. The tundish ladles were modified to hold the base iron for the wire treatment. A portable alloy addition system was fabricated. The electric arc furnaces and the 60-ton induction holder were shut down. Currently, gray and ductile iron foundries are operated with the same single SPO molding unit and the cupola-melted iron.
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