Thermo-mechanical finite element model of shell behavior in continuous casting of steel

A finite-element model, CON2D, has been developed to simulate temperature, shape, stress, and hot-tear crack development during the continuous casting of steel, both in and below the mold. The stress model features an elastic-viscoplastic creep constitutive equation that accounts for the different responses of the liquid, semi-solid, delta-ferrite, and austenite phases. Temperature and composition-dependent functions are also employed for properties such as thermal linear expansion. A contact algorithm prevents penetration of the shell into the mold wall due to the internal liquid ferrostatic pressure. An efficient two-step algorithm has been developed to integrate these highly non-linear equations. An inelastic strain-based criterion is developed to predict damage leading to hot-tear crack formation, which includes the contribution of liquid flow during feeding of the mushy zone. The model is validated with an analytical solution for temperature and stress in a solidifying plate. It is then applied to predict the maximum casting speed to avoid crack formation due to bulging below the mold during casting of square steel billets.