Numerical simulation of the evolution of primary and secondary Nb(CN), Ti(CN) and AlN in Nb-microalloyed steel during continuous casting

Abstract

Abstract The precipitation of carbides and nitrides in Nb-microalloyed steel is investigated experimentally and theoretically using light optical, scanning and transmission electron microscopy, and the thermokinetic software MatCalc. The simulations are based on a recently developed two-step methodology for precipitation simulation in primary solidification microstructures, where the compositional inhomogeneities from microsegregation are taken into account. The computed segregation is clearly evidenced in electron probe microanalyses of the as-cast microstructure. Based on the results of a Scheil–Gulliver simulation, precipitation kinetics simulations are performed with the chemical compositions corresponding either to the solute-rich interdendritic zone or the solute-depleted dendrite core zone. The predicted phase fractions, mean radii, number densities, and compositions of the precipitates are in good agreement with the experimental investigations.