Feed forward automatic thickness controlling method

Abstract

In a steel rolling mill, (a) a calibration of a thickness in the output side which is calculated from a rolling force at a lock-on position in the present pass is performed depending upon a fluctuation from a predetermined thickness at the lock-on in the last pass, a deformation resistance of a slab and a mill constant; and (b) a constant lock-on level is given to be a predetermined thickness in the present pass as the same with a thickness in the output side given by a plastic characteristic curve of the rolled slab on the predetermined thickness at the lock-on in the last pass and an elastic characteristic curve of a rolling mill on a screw position in the present pass; and then, (c) an adjusting degree of a screw gap of the press-down screw is obtained depending upon the thickness fluctuation from the predetermined thickness in the last pass, the mill constant and a differential coefficient in a rolling load function from the predetermined thickness in the present pass; and (d) the press-down screw position is controlled depending upon the adjusting degree. The press-down screw position is controlled at the position corresponding to the position of the rolled slab in the last pass (a) depending upon the adjusting degree by gaining for a time delay of the screw gap adjusting system comprising the press-down screw from the position corresponding to the position of the rolled slab in the last pass or (b) depending upon the adjusting degree at the position corresponding to the position of the rolled slab in the last pass by providing a phase gain compensation to the time constant in the screw gap adjusting system.