A tension assessment model for digital twins of continuous rolling processes

Abstract

The paper deals with the calculation of interstand tensions in continuous rolling mills for flat and long products. A fast calculation method for the interstand tensions from measurable process quantities is a mcritical point to enable the construction of digital twins for the rolling process, which must be adjusted to the real-world tension behaviour of the production system. It is straightforward to calculate the effects of the tensions on roll forces, torques and the strip or bar velocity. However, the inverse problem of calculating the acting interstand tensions including their effects from the process parameters is of much greater interest but also of a higher complexity, because the interactions between all of the stands in the continuous rolling mill must be taken into account. The paper presents a mathematical model to solve the inverse problem by subsequent linearization of the tensions influences in the rolling mill. Extra nonlinearities are taken into account by modeling the tension-dependent spread by an empirical model. The overall model is solved by an iteration method to yield a fully compatible solution for the constant volume flux as well as the force and torque equilibria in the roll gaps. Results are shown for the tension distributions in strip and rod mills. The results indicate that the present friction conditions and the spreading behaviour of the rolled material have a high impact on the tension distributions.