Longitudinal residual warpage of strip in continuous annealing line

After the heat treatment in continuous annealing line (CAL), the strip always exhibits phenomenon of residual warpage during punching process. This geometric defect is mainly attributed to the residual stress induced in the line and has a close relation with the temperature history of the strip. It becomes more serious for the wider strip and may significantly degrade the quality of the products. The contents of this study are mainly composed of establishing the energy model of the strip and roll to estimate the temperature distributions of the strip and the surface temperature of the roll, estimating the emissivity and equivalent heat transfer coefficient of the strip in each section of CAL, and establishing mechanical model of the strip to evaluate the distributions of contact pressure and residual stress of the strip especially along the width direction. Finally, the longitudinal residual warpage was calculated accordingly by virtual layers method (VLM). It was found that the residual warpage at both sides is larger than the central region. Moreover, the numerical results of strip warpage are well consistent with the experimental data which demonstrates the accuracy and reliability of the proposed method.