SIMULATING SOLIDIFICATION OF SPHEROIDAL GRAPHITE CAST-IRON OF FE-C-SISYSTEM

A model to predict the solidification of spheroidal graphite (SG) cast iron during cooling process was developed. The model treated the prob lem of the ternary Fe-C-Si system and aimed at simulating the evolutio n of the solidifying microstructure. When the eutectic temperature is reached, eutectic grains are formed. The rate of nucleation depends on the melt characteristics and supercooling. The nucleation rate was as sumed to be presented by power law function of undercooling. The growt h of the austenite grain was controlled by carbon diffusion through au stenite. Carbon and silicon concentrations at different interfaces are calculated from the Fe-C-Si equilibrium ternary phase diagram and She ll equation was applied to calculate the silicon content in the bulk l iquid and the concentration of carbon in the liquid was determined to keep the eutectic reaction. The model was applied to a four-step cylin drical sand casting which has a different diameter. The simulated resu lts were compared with the experimental ones using a post processing p rogram which was also developed to simulate the microstructural evolut ion graphically. The results showed relatively good agreement and the usefulness of the proposed model was confirmed.