Numerical Modeling and Experimental Verification of Macrosegregation and CET Predictions in Large Steel Roll Ingots

A multi-component Computational Fluid Dynamics (CFD) model developed to study macrosegregation phenomena in 65-tons 2.5 m diameter round-sided steel ingots has been verified through advanced microstructural characterization, chemical analysis and non-destructive testing. Radial and central bars machined out from the full-scale as-cast ingot were compared against the model predictions in terms of columnar-to-equiaxed transition (CET), channel segregation as well as centerline segregation within the central zone of the ingot, which are inherent in the production of industrial scale alloy ingots. The CFD model solves for volume fraction of phases, time-dependent temperature distribution, mass and species transfer to predict segregation patterns in the solidifying ingot. It addresses the influence of various process parameters and mold design aspects on solidification behavior, such as: mold system, pouring rate, superheat, hence, resulted cooling rates, thermal gradients and chemical composition variations. The numerical and experimental results were compared and discussed.