Controlled solid-liquid transition during twin-roll casting

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In forming processes, the tool has a highly non-linear effect on the workpiece, distributed over time and space. Existing control models and equations cannot take into account the variations due to the forming process, such as alloy composition, forming speed variations, temperature, etc. As an exemplary forming process, the twin-roll casting of magnesium alloys is used, in which an primary forming process takes place in the process zone prior to forming. Due to the free surfaces between nozzle and rolls as well as the a priori unknown position and shape of the solidification area, twin-roll casting is a free boundary value problem and metastable. In terms of process control and, due to the lack of resilient measurement data, twin-roll casting in connection with the resulting material properties is only partially understood or evaluated. Measurement and model uncertainties are given by the lack of measurement data, especially for the position and shape of the solidification range during casting. In the present project, these uncertainties are to be eliminated by a newly developed sensor system integrated in the roll. The microstructure and the final strip properties can currently not be detected at any time during forming in the entire material. Thus, not all disturbing factors can be considered in the model. The uncertainties that stand in the way of a robust, property-based control of the casting-rolling process are now to be eliminated by quantitative measurements of the stress state as well as temperature and heat flow in the casting-rolling gap. Robust measuring systems and soft sensors have to be developed which allow the microstructural condition to be reliably estimated from measurable quantities during dynamic measurements. The cooperation is expected to lead to a fundamental increase in knowledge about the design of resilient, microstructure- and property-controlled forming processes.