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A hot rolling schedule of non-oriented electrical steel of the same strip width suffers from severe uneven roll wear, which leads to high spots and excessive edge drop. To eliminate these shape defects, a 'keep-smooth' shifting strategy of the taper roll was proposed: the strategy aimed at a smooth roll wear contour and was achieved by a varying-rate shifting mode. A roll wear model was developed to predict the evolution of the wear contour under different shifting parameters, and the optimal parameters were obtained by the adaptive particle swarm optimisation algorithm. The effect of the new shifting strategy on the strip profile was studied based on a 3D finite element rolling model. The industrial application verified the new taper roll shifting strategy, as both the edge drop and high spots were alleviated and the rolling length of a schedule was extended by about 10 km.

Elastic recovery and viscoplastic stress relaxation occur in the interstand of hot rolling, impacting the evolutions of strip profile and residual stress, which are major concerns for obtaining high-quality flat products. A better understanding of the evolutionary mechanisms would help develop shape control strategies. Therefore, a quasi-3D steady-state elasto-viscoplastic rolling model is developed based on the finite difference method. Predictions of spread, profile, and residual stress are validated through comparisons with a two-stand finite element model. The new model is also complemented with a roll stack model and with a viscoplastic constitutive model calibrated by hot compression tests to simulate a seven-stand hot rolling industrial experiment with low carbon steel. Comparisons between the predicted and measured profiles show a satisfactory accuracy. The simulation costs approximately a minute of CPU time, enabling the new model to run massive parametric campaigns for process optimization. It is found that during the interstand elastic recovery, the transverse compressive stress releases and the strip velocity tends to be uniform, revealing residual stress after a significant change of stress pattern. The stress relaxation mainly occurs at the edge near the roll bite and therefore increases the edge drop of the profile; it also decreases the center crown by changing the distribution of the rolling pressure in the roll bite.

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