Advanced modelling of lateral flow and residual stresses during flat rolling

This project has focused on the use of advanced modelling techniques to increase the knowledge about lateral flow and residual stresses during flat rolling. Hybrid models, combining existing mathematical models with data based models, have been developed for presetting and controlling the strip width in a hot strip mill. Self-organising maps and multivariate adaptive techniques have been used to select relevant data. Models have been made both for the roughing and the finishing mill and are working on-line. A finite element model for a finishing mill stand has been developed and used for studies of the effect of the looper stresses and the friction on the lateral spread and the stress state along the contact arc. Torsion and plane compression tests were performed to accurately introduce the material behaviour in hot working conditions. Finite element modelling has also been used to simulate cold rolling of thin and wide strips in order to investigate changes in strip thickness profile, lateral flow and residual stresses. The results were analysed with statistical tools and used to improve the flatness calculations in an existing physically based model. A model based on the upper-bound theory has been developed for analysing the plastic flow in hot rolling. Hot rolling tests have been done in a laboratory mill and used to improve the upper-bound calculations of nominal spread and side surface convexity. Roughing test campaigns have been performed in a production mill and used to derive approximation formulas describing spread. The formulas have been compared with the upper-bound model and with measured data.