NUMERICAL-SIMULATION AND FOURIER THERMAL-ANALYSIS OF SOLIDIFICATION KINETICS IN HIGH-CARBON FE-C ALLOYS

The aim of this work was to carry out both experimental and numerical simulations of cast iron solidification under various conditions. The experimental work was based on a novel technique of thermal analysis k nown as the Fourier method, whereas solidification modeling was possib le by solving the Fourier equation with a heat source. Moreover, a com parison between the Fourier and the Newtonian method indicated that th eir predictions are appreciably different. The Newtonian method is rat her insensitive to the actual thermal gradients and predicts a clear m aximum in heat generation at the onset of solidification. In contrast, the Fourier method incorporates the effect of actual thermal gradient s and predicts two successive heat generation peaks of increasing magn itude as solidification proceeds. In particular, it was found that the experimental outcome of solidified volume fractions agrees closely wi th the predictions of the Fourier method. In this case, both experimen tal and computer simulations on 30- and 40-mm-diameter cylindrical spe cimens indicated that the solidified fraction followed a sinusoidal tr end. Moreover, it was found that under normal solidification condition s, secondary nucleation of fine grains can occur near the center of a cylindrical cast iron specimen. Secondary grain nucleation is attribut ed to the development of a second undercooling maximum which easily ex ceeds the initial one. Finally, the effects of inoculation were invest igated in plain cast iron and as a function of the inoculation time. A ccordingly, in all cases, the computer simulations were in close agree ment with the experimental outcome.