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The assessment of the microstructural features of ductile iron by using thermal analysis

The effect of parameters which are identified and measured by thermal analysis on the microstructural features of ductile iron was analyzed in this paper. It was found that the nodule count and nodularity increase with increasing the temperature of eutectic undercooling (TEP) and graphite factor 1 (GRF 1) and decreasing recalescence (TR), graphite factor 2 (GRF2) and value of the first derivative of the cooling curve at TS (d/dt TS). The obtained results show that the ferrite content increases with increasing the temperature of eutectic undercooling (TEP), graphite factor 1 (GRF 1) and temperature of eutectoid transformation (A1) and decreases with increasing the recalescence (TR), graphite factor 2 (GRF 2) and value of the first derivative of the cooling curve at TS (d/dt TS).The processing of obtained results was performed by multiple regression analysis. Based on the measured thermal parameters, the models for estimation of microstructural features (nodule count, graphite nodularity and ferrite content) were established. High correlation coefficients between the measured and the estimated values of microstructural features confirm that there is a tight correlation between the thermal parameters of ductile iron melt and microstructural features of ductile iron castings.

ductile iron ; microstructure ; thermal analysis

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