Nucleation and Growth of Graphite in Eutectic Spheroidal Cast Iron: Modeling and Testing

Abstract

A new model of graphite growth during the continuous cooling of eutectic spheroidal cast ironis presented in this paper. The model considers the nucleation and growth of graphite frompouring to room temperature. The microstructural model of solidification accounts for theeutectic as divorced and graphite growth rate as a function of carbon gradient at the liquid incontact with the graphite. In the solid state, the microstructural model takes into account threestages for graphite growth, namely (1) from the end of solidification to the upper bound ofintercritical stable eutectoid, (2) during the intercritical stable eutectoid, and (3) from the lowerbound of intercritical stable eutectoid to room temperature. The micro- and macrostructuralmodels are coupled using a sequential multiscale approach. Numerical results for graphitefraction and size distribution are compared with experimental results obtained from acylindrical cup, in which the graphite volumetric fraction and size distribution were obtainedusing the Schwartz–Saltykov approach. The agreements between the experimental andnumerical results for the fraction of graphite and the size distribution of spheroids reveal theimportance of numerical models in the prediction of the main aspects of graphite in spheroidalcast iron.