Fading investigation in ductile cast iron aided by cooling curve analysis

In the present research, the relationships were studied between the fading phenomenon, graphite morphologies and characteristic points on cooling curves such as the temperature of eutectic nucleation, undercooling and the temperature of the end of eutectic solidification in ductile cast iron. Cooling curves and image analysis were used to characterise the influence of holding for 0, 5, 10, 15 and 20 min on samples prepared from the melt treated with 2·5 wt-% nodulariser and 0·4 wt-% inoculant and kept at 1320°C under a nitrogen atmosphere. Different combinations of five types of inoculants and four types of nodularisers, with different fading resistances, were employed. The temperature of eutectic nucleation, temperature of eutectic under-cooling, temperature of eutectic ending, magnitude of undercooling and duration of eutectic transformation variations are closely interrelated with the morphology of the graphite.