TM-rolling of heavy plate and roll wear

Abstract: The heavy plate rolling process needs accurate predictions of the process parameters. The plate thickness, flatness and rolling stability are of this direct influenced as well as the productivity. Therefore, careful calculation of the process parameters and pass schedules is necessary. The thesis is concerned with two aspects of controlling rolling; the choice of optimal pass schedules and roll wear. A software has been developed in Paper A to determine optimal pass schedules for thermomechanical rolling in order to obtain a fine microstructure. It includes models of the effect of strain, precipitates, static and dynamic recrystallization and austenite grain size on the final grain size. The predicted grain sizes for four different cases were compared with experimental results. It was also used to study the effect of different delay times during the pass schedule of rolling thermomechanical plate. The results shows that an increase in delay times results in finer ferrite grains are received. The refinement is however small for long delay times. Long delay times also affect the productivity negatively. A method for modeling of the work roll contour in a four high mill is presented in Paper B. The active parameters were found to be the plate length and the variations of the pressure from the plate and the back-up roll on the work roll along the work roll barrel. The method is build up with statistical methods. The bases for the statistics are simulations of different rolling cases and measurements from the production of heavy plates in Oxelösund. The proposed wear contour model was found to be in good agreement with the measurements from the production.