The effect of the strip shape defects is due to the fact that the strips have different internal stresses in the width direction, resulting in a small length difference in length along the longitudinal fibers adjacent to each other in the width direction. In order to obtain a flat plate strip, it is only necessary to apply a stress exceeding the yield limit to the length direction of the strip, so that the long and short fibers simultaneously produce a certain plastic deformation. After the stress relaxation, the elongated and long fibers remain, thereby making the strip The length and internal stress of the longitudinal fibers in the material tend to be the same, and the direction is consistent to achieve the purpose of leveling.