INTEGRATED FINITE ELEMENT MODEL FOR TRANSIENT FLUID FLOW AND THERMAL STRESSES DURING CONTINUOUS CASTING

A finite element computational methodology is presented for predicting the temperature distribution, fluid flow, and thermal stresses evolving in a solidifying ingot, which itself is growing in length, during the start-up phase of a continuous casting process, with a particular reference to aluminum casting. The approach is based on the coupling of a thermal and flow model with a stress model, The thermal flow model is developed using a deforming finite element method with an Eulerian-Lagrangian transformation to account for the fact that the ingot itself is also growing at a prescribed casting speed. The stress model is developed also by the finite element method, with mechanical deformations in the solidifying materials described by a hypoelastic-viscoplastic constitutive relation. The integrated model has been applied to study the dynamic development of temperature, flow, and stresses in the solidifying ingot during the start-up phase for continuous casting of aluminum. The results show that the fluid flow and temperature distribution experience a rapid change at the initial stage but that the change slows down later in the process as it approaches to the steady state. Computed results compare reasonably well with experimental measurements for temperature distributions in the ingot. It is found that the thermal stresses in general evolve from small to big in magnitude and from compressive to tensile in the solidifying ingot. The hoop stress is larger than other stress components, in particular in the outer surface region. The air gap formed between the ingot and the bottom block increases initially and decreases afterward as a result of stress relaxation.