The purposes of this research are to study the effects of minorelements, i.e., bismuth and antimony, on the microstructure ofductile cast irons having different solidification times, and todetermine the amount of rare earths (cerium) required to neu- tralizethe subversive effects of Bi and Sb. Various types of degenerategraphite, including chunky, compacted, irregular, etc., tend to formin the microstructure of heavy-section ductile cast irons. Theaddition of up to 0.0030/100 Bi results in increased nodule count andimproved nodularity. However, the beneficial effect of Bi ceases, ifthe addition amount of Bi exceeds 0.0045/100. The deleterious effectof Bi causes the formation o. f irregular graphite in the castings.
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