Method for presetting CVC and WRB parameters of a multi-stand tandem cold rolling mill to ensure IF steel strip flatness

This study presents a formalized method for the initial parameter setting of the CVC (Continuously Variable Crown) roll shifting and WRB (Work Roll Bending) systems in a tandem cold rolling mill. The method is designed to achieve high flatness in strips produced from highly ductile IF (Interstitial-Free) steels. The need for this solution arises from flatness defects like buckling and waviness, which occur due to non-optimal roll gap profile control. This is particularly critical in the final stand, where deformation resistance peaks while reduction is minimal. Current automatic control systems are ineffective at compensating for the inherent geometric imperfections of the hot-rolled feedstock. The proposed method is based on calculating a composite quality index (X) for the hot-rolled strip. This index incorporates its critical geometric parameters: maximum crown shift, minimum left and right wedge, strip width, along with the finishing and coiling temperatures. Using regression models derived from this data, the method calculates optimal pre-set values for the roll shift in the second-to-last and last stands, and the roll bending force in the last stand, prior to rolling each coil.Industrial testing at the 4-stand 2100 mill confirmed the effectiveness of the developed method: for strips with a width of 1400-1640 mm, stable rolling quality without defects was guaranteed, while the baseline technology led to rejects. The implementation of the method allows for the integration of optimal settings into the technological process, significantly reduces the volume of non-conforming products, and provides an annual economic effect exceeding 4 million rubles.