However, in the actual production process, due to the action of the jaws and to ensure the clenching of the strip and the action of the coiling tension, the strip has been partially plastically bent at the jaws. At this time, the bending radius of the strip is no longer the same as the coil. barrel radius R, but r. An obvious high point is formed at the jaw. When the second and third circles of strip steel pass through, plastic bending will inevitably occur under the small curvature radius r, so that the surface of the steel strip will form an irreversible transverse deformation along the strip after uncoiling. With the continuous coiling of the steel coil, its r continues to increase. When the formula 1 is satisfied, the stainless steel coil will no longer be plastically bent. Therefore, generally, the coiling creasing of the outer ring of the steel coil becomes lighter or no longer occurs. Similarly, as the thickness of the strip becomes thicker, it can be seen from formula 1 that the minimum required radius of curvature without plastic bending also increases accordingly. Under the same equipment conditions, the coiling and folding defects of the thick steel strip will also increase many.

Therefore, the reasons for the formation of coiling and folding defects can be attributed to:

a) There is a warping of the lead at the coiling place of the jaws, forming a bulge;

b) After the reel is expanded, it is a true circle, while the steel strip is a helix when it is wound;

c) The thickness of the strip is different, and the winding pitch is also different, resulting in different degrees of coiling and printing of the cold-rolled strip with different thicknesses.