Principles of Continuous Gauge Control in Sheet and Strip Rolling

The problem of longitudinal gauge variations in hot- and cold-rolled sheet and strip metal is considered. It is suggested that they are caused mainly by elastic distortions of the mill in response to variations in the separating force between the rolls. A unique relation is shown to exist between the roll force and the thickness of the strip leaving the rolls, and this forms the basis of two new methods of continuous automatic control of gauge. These methods are independent of direct measurement of the thickness of the sheet or strip during rolling. They employ an electrical roll-force measuring element the output of which, after suitable modification, continuously adjusts either the position of the rolls or the tension applied to the strip, so that a substantially constant thickness is maintained in the rolled material. Some preliminary experiments on a 10 inches by 10 inches two-high mill have demonstrated that these methods of control are correct in principle.