Thermomechanical ring rolling with predictive property control

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Thermomechanical tangential ring rolling (TMR) is a process for the production of near-net-shape ring geometries with simultaneous targeted influencing of the microstructure and hardness by closed loop control of the forming speed and temperature. For this, a combined approach of PID and predictive models is used, in order to use the full existing process window in such a way that the target values for final geometry, microstructure and hardness can be achieved simultaneously. In FÖP I and II, the development of the system architecture, the required soft sensors and associated models, as well as the implementation of a real-time capable measurement data acquisition system were carried out in order to realize a closed control loop on the ring rolling machine. Cascaded control loops were used to control the forming speed and air flow and, as a result, the cooling rate and the resulting microstructure. In experimental tests, the process and disturbance variables were analysed and their influence characterized, and the effectiveness of the implemented temperature control loop was demonstrated in the course of FÖP II. The soft sensor for microstructure development combines temperature sensors and an eddy current sensor developed in the project to record the microstructure on the surface with fast temperature, material and forming models to predict the ring properties inside the ring. The optimal input parameters are continuously adjusted based on the measured data and a prediction model. The findings from FÖP II led to a concept for the control of the ring rolling machine and the identification of associated process windows, which will be taken up in the third funding period. The goal in FÖP III is to complete the implementation of the controller under near-production conditions. This will serve to identify and quantify the influence of the control loops on process performance in different configurations. Furthermore, the identification of the process limits ensures the transferability of the developed methodology, e.g., to different ring geometries or materials. For this purpose, the existing digital twin is extended to allow a simulation of the process, including the closed loop control. After validation on the real machine, it will be possible to transfer the control strategy for geometries and configurations to cases that are not feasible on the existing rolling mill. An analysis of the process and system performance will allow the derivation of design principles and rules in terms of system architecture (actuators, sensors, modelling and control) for the implementation of thermomechanically-controlled ring rolling.