Abstract
This report is one of the series of fundamental studies on ferritic cast iron. The purpose of this investigation is to produce ferritic cast iron in the as cast state without heat treatment. In this study, the cooling rate after freezing in shell mold was measured, and the relation between the cooling rate, the carbon content and the quantity of ferrite in the matrix structure was examined.
The ferrite area ratio in the matrix structure (F) decreased with the increase of cooling rate (V) after freezing, and a following relation was established ; F=−a√V+b, where a and b are constants. The influence of cooling rate on the ferrite area ratio in matrix structure decreased with the increase of Scvalues. Between Laplanche’s coefficient of graphitization (K) and the maximum cooling rate (Vm) to obtain a perfect ferritic matrix, a relation of log K=p(−logVm)+q was established, where p and q are constants.
The ferrite area ratio in the matrix structure increased with the increase of eutectic reaction time and eutectoid transformation time. It was known that the influence of cooling rate on the ferrite area ratio in the matrix structure is highest in the neighborhood of eutectoid transformation temperature.
