Coupled thermal and stress-strain models for the continuous casting of steels

During the continuous casting of steel thermo-mechanical loadings may cause defects of the strand shell when exceeding the temperature-dependent material strength. Primary cause is the interplay of temperature level, and temperature gradients within the strand shell, the change of material properties, and further mechanical loadings of the strand shell like compression and friction forces or the ferrostatic pressure of the liquid. A model system has been developed to calculate the temperature distribution during continuous casting of steel and the resulting probability of hot crack formation, due to the thermo-mechanical loadings. First part is a thermal model to calculate the three-dimensional transient temperature field. In a reduced form this model can describe two-dimensional transient and, with less effort, two-dimensional steady-state problems. For the calculation of stresses and displacements a model based on a simple plane strain formulation, and a model using the fully three-dimensional stress-formulation are shown. Because material behaviour and temperature field are interdependent, thermal and mechanical models have to be coupled depending on the problems to be solved. Strategies for a problem-specific model coupling are discussed. Finally, the applicability of the model system is shown by some example problems from operational practice.