Modeling of ingot distortions during direct chill casting of aluminum alloys

A comprehensive three-dimensional mathematical model based upon the Abaqus software has been developed for the computation of the thermomechanical state of the solidifying strand during direct chill (DC) casting of rolling sheet ingots and during subsequent cooling. Based upon a finite element formulation, the model determines the temperature distribution, the stresses and the associated deformations in the metal. For that purpose, the thermomechanical properties of the alloy have been measured up to the coherency temperature using creep and indentation tests. The thermophysical properties as well as the boundary conditions associated with the lateral water spray have been determined using inverse modeling. The predicted ingot distortions, mainly butt curl, butt swell and lateral faces pull-in are compared with experimental measurements performed during solidification and after complete cooling of the ingot. Particular emphasis is placed on the non-uniform contraction of the lateral faces. The influence of the mold shape and the contributions to this contraction are assessed as a function of the casting conditions.