抄録
It seems that the ductile-brittle transition of ferritic nodular cast iron depends not only on chemical compositions but also on many microstructural variables. In this study, ferritic grain diameter and mean free path between graphite nodules were adopted as the microstructural variables and the effects of these variables on the toughness were examined mainly by carrying out instrumented Charpy impact test. Both finer ferrite grains and smaller mean free pathes showed the tendency to lower the transition temperature. On the other hand, ferrite grain refinement and larger graphite nodules tended to improve the upper shelf energy level. Equations to predict lower yield load and the maximum load transition temperature in the ferritic nodular cast iron were derived by applying the well-known relation in the case of the steel with dispersed spheroidal carbides.
