Strömung von Flüssigstahl und Transport von Einschlüssen in einer Stahl-Stranggussanlage

The three-dimensional, turbulent flow of the liquid steel in the tundish and in the strand of a continuous casting plant with vertical mold and bended strand is computed with numerical models. Measurements of the velocity fields in water models of tundish and strand with the PIV method are compared with corresponden transient numerical simulations. Non-metallic inclusions are modelled in the numerical simulations as discrete secondary phase with an Eulerian method. Transport, separation and solidification of the inclusions are computed. Beside the numeric simulations also analytical models are provided, in order to better understand the separation of the inclusions. Both models are used to examine the possibilities for the evaluation of the separation in the tundish, in particular residence time distributon curves, and to optimize the tundish geometry. In the strand, the formation of the inclusion band - an accumulation of the inclusions within the upper range of the strand cross section because of to the strand curvature - can be reproduced with both models. The distribution of the inclusions over the strand width depends thereby on the flow profile of the molten steel at the beginning of the bending zone. The distribution of the inclusions over the strand length with a temporary increase of the inclusion density during a ladle change is computed and compared with plant measurements.