Generation mechanism of high-order waves in wide titanium strip under the control of the first intermediate taper roll of a 20-high mill

One of the difficulties in high-precision flatness control of a 20-high mill is the high-order waves that are prone to occur when adjusting the edge thickness process with the first intermediate taper rolls. To explore the mechanism of high-order wave generation, based on FEM software, the crown adjustment of backup rolls (ASU adjustment) was achieved using the connector function, and an integrated coupling rolling model of the roll system and titanium strip was established. The accuracy of the model was verified using on-site measured data. The evolution law of the flatness during the process of controlling the thickness of the titanium strip edge by the taper and coning amount was analyzed. The results showed that as the taper and coning amount increased, the deflection deformation of the work roll edge gradually weakens, and the thickness of the titanium strip edge gradually increases, resulting in a gradual decrease in longitudinal strain. When the taper is 0.7% and the coning amount exceeds 50 mm, high-order deflection deformation will occur in the area 75–350 mm away from the titanium strip edge, leading to a significant increase in longitudinal strain here, thus greatly increasing the risk of the high-order wave. Finally, through industrial tests of single taper section and double taper section rolls, it has been confirmed that the high-order deflection deformation of the work roll axis caused by the first intermediate taper roll is the fundamental reason for the generation of the high order-waves.