(STSI-73)Deflection and Bending Model of a Four-High Mill Stand for Heavy Plate Rolling

摘要

In heavy plate mills, the quality demands on thematerial properties, the thickness and the flatness ofthe final products are steadily increasing. The thicknessand the flatness are significantly influenced bythe elastic deformation of the mill, which cannot bedirectly measured. Hence, there is a need for precisemathematical models of the deformation of the mill.The deformation of the mill consists of the complianceof the mill housing including the bearings of the rollsand the hydraulic cylinders as well as the bending andthe flattening of the rolls. The overall deformation iscommonly calculated by means of characteristiccurves obtained from measurements or FEMsimulations.This paper presents results of a physics-based modelof a four-high finishing mill stand describing thecompliance of the mill housing as well as the flatteningand the bending of the rolls. The model of the rolls isbased on Timoshenko’s beam theory and the Hertziancontact theory. The four rolls are represented byTimoshenko beams and are coupled by the localrolling force between the two work rolls and thecontact pressure between the backup- and the workrolls.Since the model facilitates a detailed physicalinterpretation of all model parameters, measurementdata can be worked in wherever applicable – bothoffline and online. The model may therefore be usedfor model-based control as well as for roll passscheduling. As the model not only calculates thecentral thickness of the plate but also the thicknessprofile over the plate width and length, it mayadditionally be utilized for improving the productflatness, e.g., by adapting the roll bending forces. Theresults of the model are verified by means ofmeasurement data from actual rolling processes.