Use of Multiple Nodularizing Elements in Making Ductile Iron Pipe.

Results are presented of an intensive study of the nodularizing processes used for the centrifugal casting of ductile iron pipe by the metal-mold (de Lavaud) process. The primary objectives were to reduce the cost of the nodularizing treatment, and to reduce the amount of smoke and flare produced in the nodularizing treatment. The experimental work involved comparison of the nodularizing effectiveness of magnesium, cerium, lanthanum, neodymium, praseodymium, and yttrium; comparison of the rate of fading of additions of single nodularizing elements with multiple nodularizing elements; and evaluation of the reactivity of silicon-base alloys containing up to five nodularizing agents in relatively low concentrations. Results indicate that it is possible to produce ductile iron pipe from low-sulfur cast iron by additions of two or more nodularizing elements in relatively low concentrations so that the total concentration of elements in the iron is sufficient to produce ductile iron, but the concentration of any one element, of itself, is insufficient to produce good spheroidal graphite.