Applicability of heat transfer and solidification simulations in investigating microstructural banding in continuously cast steel

Abstract Microstructural banding is observed as alternating microstructures in cast steel products, parallel to cast/rolling direction. Banding, causing hardenability issues and anisotropy of mechanical properties, is considered to originate from the interdenritic segregation during the solidification of steel. In this study, a three-dimensional heat transfer model (3DHTM) was used to simulate the steady-state local temperatures in a casting strand of 0.34C low alloy carbon steel, taking into account both primary and secondary cooling as well as other casting parameters. The calculated temperature profiles for a set of selected locations along the strand were used as input data for a solidification and microstructure model (SMM) for the continuous casting of steel. To assess the microstructure of the cast bloom, the prior austenite grain size, dendrite arm spacing, and the magnitude of elemental microsegregation between the dendrites were calculated with the selected temperature profiles for the steel grade. For validation purposes, bloom and bar samples were prepared from industrial trials. The calculated results are compared to the microstructural characterization of austenite grain size, and local elemental concentrations obtained with electron probe microanalyzer (EPMA). Based on the results, elemental microsegregation and microstructural banding is assessed, affected by casting parameters and the total composition of steel. Additionally, a brief discussion of the segregation between the bloom and bar samples is presented