Simulation of shrinkage and stress in solidifying steel shells of different grades

Thermal-mechanical behavior of the solidifying shell is important for design of taper and understanding crack formation and other defects during continuous casting of steel. A transient finite-element model, CON2D, has been developed to simulate the evolution of temperature, stress and strain in the solidifying shell during this process. The model features unified elastic-viscoplastic constitutive models for austenite, ferrite, mushy, and liquid steel. The model was validated by simulating an SSCT experiment similar to that of Kurz. CON2D was then applied to investigate the effect of steel grade on thermo-mechanical behavior of a slice domain under realistic heat flux conditions. The shrinkage predicted by CON2D was compared with simpler methods, such as that of Dippenaar. This simple method is found to over-estimate the shrinkage of low carbon steels, where a substantial fraction of soft delta-ferrite exists, but matches reasonably for high carbon steel, containing strong austenite. Implications of the stress and strain profiles in the solidifying steel and practical applications are also discussed.