METHOD FOR CONTROLLING PLATE THICKNESS IN UNSTEADY ROLLING AREA IN TANDEM COLD ROLLING

PURPOSE:To minimize the off gate quantity of every rolled coil and to improve the yield and quality by controlling the mass flow on the inlet side of a last stand and controlling the plate thickness on the outlet side of the last stand to a target set value. CONSTITUTION:The tension between a last stand k of a tandem cold rolling mill and a stand k-1 directly before the last stand is monitored by a tension meter installed on occasion between the stands, a deviation is detected from a certain reference set value and a control output is obtained from a series of operation. Then, the speed of the roll of the stand k-1 directly before the last stand is modified and the mass flow on the inlet side of the last stand is controlled to control the plate thickness of a formed product on the outlet side. Especially, since a tuning parameter is provided as one element in this control loop and a certain suitable dependency is given, the effect to the accuracy of the plate thickness of a formed product accompanied by factors deteriorating accuracy of various plate thickness is removed in time of an unsteady rolling state composed of an acceleration and deceleration part and a lower speed part.