Abstract
Various theories, hypotheses or ideas have hitherto been proposed on globular graphite formation in cast iron. The author classified them into the following 5 groups, and discussed concluding that all of them are untenable from points of views of crystallography, physics and science of metals. 1) Surface Tension Theory 2) Theory Assuming the Disappearance of Directional Differences of Growth Rates due to Supercooling 3) Super-saturation Theory 4) Theory Assuming Spherical Nucrei 5) Theory Assuming that Globular Graphite is Formed in Solid Phase The author added also briefly his own theory proposed in the “Report of the Castings Research Laboratory,” Waseda University, Tokyo in 1950 and 1953. This theory is based on the following ideas and has fairly been proved by experiment. Graphite particles separating from melt adsorb magnesium vapour, which is also separating due to the decrease of solubility on austenite solidifying, and become extremely flexible and inelastic. These extremely flexible and inelastic particles of graphite, suspending and incessantly moving in the melt, are pressed equally by the force on all sides and necessarily globularize in a plastic way.
