Abstract
Extensive trials were carried out to verify the hypothesis of the formation of nodular graphite inside gas bubbles and to establish it as a gas bubble theory of nodularization of graphite. It was found that graphite nodules can be obtained by four methods: addition of deleterious elements such as S, Se, Te, Pb, and Bi; or of Ce, La, Y, Ti, and Zr which have absorbed a large amount of hydrogen; direct injection of gases into the melts; and precipitation of nitrogen from super-saturated molten cast iron. The formation of gas cavities and hollow graphite nodules was observed and attributed to the dearth of graphite in bubbles or to its absence. Some characteristics of graphite nodules could be best explained by the proposed gas-bubble theory.
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