Alloys of Fe-C-Si prepared from high purity metals were solidified in crucibles and by directional freezing techniques. It was found that the formation of graphite nodules required cooling rates in the 100 to 200°C/min range. At very high rates no graphite formed and at low rates coral graphite formed. The use of very high purity Battelle Iron eliminated nodule forma¬tion unless an inoculant was used. Extensive chemical analyses were not able to detect the elements effective as nucleating agents, except to show that if an individual element were responsible it was effective at concen¬trations in the low ppm range. Possible mechanisms are proposed to account for the observed results.
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