GB999761A - Control systems for rolling mills - Google Patents

Abstract

999, 761. Automatic control of rolling mills. DAVY & UNITED INSTRUMENTS Ltd. April 12, 1962 [April 13,1961],No. 13318/61. Heading G3R. In an automatic control system for a tandem rolling mill, errors in thickness of the rolled material at one stand, detected by means responsive to the rolling load at that stand, control roll separation at that stand by adjusting means which also determine proportional adjustment of roll separation at a preceding stand. As shown, in a six-stand hot strip finishing mill the strip moves from left to right and signals dependent on the rolling load and screw-down position at stand F3, derived from pick-offs 12 and 15 respectively, are compared with a signal, representing desired thickness, from a device 16 and the resultant signal, representing thickness error, applied through an amplifier 18 to control a follow-up servomotor 20 adjusting an A.C. signal generator 22 to a corresponding position. The output of signal generator 22 is applied to a gating circuit 25 so that when the error exceeds a value determined by the setting of a device 26, a signal is applied through a gating circuit 27 to actuate a screw-down motor 13 of stand F3 to partially correct the error which is further corrected by the proportional adjustment, through a synchro 28, of screw down motors associated with preceding stands F 1 , F 2 . Operation of the screw-down motor is prevented if the rolling load becomes excessive by a signal applied from load pick-off 12 to gating device 25 through a limiting device 36. By changing over a switch 37 temporarily at the start of rolling a servomotor 39 sets device 16 to correspond with the thickness of the strip which is thereafter maintained at that value. Tension detectors L1-2 to L5- 6 between each pair of stands respectively control the speeds of the rolls of adjacent stands to maintain constant tensions. A further control system responsive to the thickness of the strip at stand F5 which controls the speed of the rolls of stand F6 for small errors and the screw-down motors of stands F4 and F5 for large errors may be provided.