Dendritic segregation in microalloyed cast steels

Dendritic segregation in cast low-carbon steels microalloyed with niobium, titanium and vanadium was experimentally investigated both on quickly solidified and cooled small laboratory heats and on pilot plant heats, which were solidified and cooled slowly and moreover annealed for homogenization. Evaluation of the dendritic segregation was based on the model of ideal dendrite representing all the dendritic population of the casting. According to the values of effective partition coefficients and values of heterogeneity index of chemical elements, these were classified into groups of high (S, P, N), middle (C, Nb, Ti) and low (Mn, Si, V) degree of dendritic segregation. A close correlation between the effective partition coefficients and heterogeneity index was confirmed with negligibly different parameters for laboratory or pilot plant heats. The applied method for assessment of dendritic segregation respects not only the solidification process but also all the following treatments what rationalized the higher values of effective partition coefficients as compared to corresponding values of equilibrium partition coefficients of alloying or impurity elements.