Formation mechanism and control strategy of M-shaped and W-shaped profile defects in hot rolling of aluminum plate

Abstract

Good profile is one of the important control objectives in hot rolling of aluminum plate. However, M-shaped profile defect often appears for wide aluminum plate and W-shaped profile defect often appears for narrow aluminum plate. In order to reveal the formation mechanism of the two typical profile defects, the evaluation indexes of the M-shaped profile defect and W-shaped profile defect are proposed, and the roll-plate coupling deformation model and the roll thermal expansion model are established. The effects of rolling force, bending force and work roll thermal expansion on the profile are analyzed using these models. The results show that the rolling force and bending force has little effect on M-shaped profile defect, and the main reason for this problem is the uneven thermal expansion of work roll. Meanwhile, the W-shaped profile defect is produced under the combined action of the roll thermal expansion and large roll deflection, and the roll thermal expansion is the necessary condition for the formation of W-shaped profile defect. The greater the thermal crown of the roll, the smaller the rolling force and the greater the bending force, the more obvious the W-shaped profile defect. Based on the above conclusions, industrial tests were carried out. By increasing the cooling flow in the middle of the roll, the frequency of M-shaped profile defect decreases from 29.4% to 9.0%. Meanwhile, by increasing the positive shifting of CVC rolls, reducing the bending force, and decreasing the cooling flow of work roll at the edge of the plate, the frequency of W-shaped profile defect decreases from 42.1% to 14.1%. The profiles of the hot rolled aluminum plates are effectively improved by the developed control strategies.