Curling of hot-rolled steel sheet caused by surface oxide scale

Rolled sheets may turn up or down after passing the roll gap. The curling occurs under asymmetric conditions, e.g., different roll speeds, diameters, frictions, etc. Even under apparently symmetric conditions, the curling incidentally occurs in hot rolling. In this study, low carbon sheets with controlled upper and lower oxide scale were hot-rolled with 15% reduction in thickness. The rolled sheets always curled toward the side with thin oxide scale and that severe curling occurred when upper and lower oxide scales deformed differently. It is concluded that surface oxide scale is a hidden factor to cause curling in hot steel rolling.