Prediction of steel strip flatness based on the difference in drawing coefficients along its width during steel strip rolling

The paper presents a brief overview of approaches to calculating flat strip shape defects. It is shown that the most important technological factors in forming a flat sheet are the difference in draw bars across the strip width and the inter-roll gap profile, which depends mainly on elastic deformations that are uneven along the barrel length. The elastic deformations of the working roll surface were simulated, which, together with its thermal profile and wear, made it possible to estimate the transverse profile of the rolled product. The process of deformation of a set of rolls in a quarto stand was studied in the ANSYS Mechanic program using the Static Structure module. The results of calculating the elastic deformations of the roll surface in contact with the deformed strip with varying parameters over a wide range of values made it possible to obtain a statistically reliable equation for estimating the roll barrel profile in the deformation zone and the transverse profile of the rolled product. The obtained roll profile was used to study the formation of the flatness defect “waviness” using the DEFORM-3D program. It was carried out by simulating the rolling of a steel strip with a given transverse profile in profiled roll barrels. On the finished strip, the amplitude of the flat shape defect was estimated by comparing the vertical displacements of the strip section at its edge and in its middle at the exit from the rolls. Using a well-known technique, the amplitude of the “wave” and “box” was also calculated. The assessment was carried out on the basis of the difference in the elongation coefficients across the strip width. The results of the assessment and modeling of the rolling process showed very close results, which confirms the possibility of calculating the flatness parameters by the difference in the strip elongations across its width using a well-known formula.