GB898613A - Automatic control system for continuous strip mill - Google Patents

Abstract

898,613. Automatic control systems for rolling mills. UNITED STATES STEEL CORPORATION. Feb. 11, 1959 [Feb. 6, 1958], No. 4824/59. Drawings to Specification. Class 38 (4). [Also in Group XXXVIII] In a multi-stand continuous hot-rolled metal strip mill a signal corresponding to the thickness of the strip at the first stand is compared with a reference signal developed by the same measuring device when the leading edge of the strip leaves the first stand, any error serving to adjust the setting of the rolls of the second stand to obtain constant strip thickness. As'described, the mill comprises six stands each of which has one D.C. motor driving the rolls and another for adjusting their spacing. The roll driving motors are associated with tachometer generators which, through a system involving a magnetic amplifier and amplidyne generator, maintain the speeds of the rolls at values determined by the settings of manual potentiometers and the magnitudes of control signals referred to below. The motors adjusting roll spacing are associated with selsyn generators which ensure that the spacings correspond with the settings of manual or programmed potentiometers and the magnitudes of further control signals referred to below. A voltage corresponding to the thickness of the material leaving the mill is produced by an X-ray gauge to control the speeds of the rolls of the last three stands. If this voltage exceeds predetermined limits the spacing of all or some of the rolls is also controlled. A motor-driven potentiometer is operated automatically so that the voltage from it balances that from a transducer responsive to the temperature of the bar entering the mill. After a predetermined time, when the trailing edge of the bar leaves the first stand this circuit is re-arranged so that a voltage corresponding to the difference in temperature of the next bar serves to modify the roll spacing of the first stand. The roll spacings of the other stands are also modified in a similar manner as the trailing edge passes them. A further motordriven potentiometer is operated automatically so that the voltage from it balances that from a transducer responsive to the force between the rolls of the first stand as the bar enters. After a predetermined time this circuit is rearranged so that a voltage corresponding to changes in the thickness of the bar serves to modify the roll spacing of the second stand and the speeds of the rolls of the first two stands. A still further motor-driven potentiometer is operated automatically so that the voltage from it balances that from a transducer responsive to the force between the rolls of the fourth or fifth stand when the bar enters. When the bar passes the sixth stand this circuit is rearranged so that a voltage corresponding to change in the bar thickness serves to modify the speeds of the rolls of the last three stands. A modification in which the speeds of the rolls of the first three stands are also modified in accordance with the change in force between the rolls of the first stand is referred to.