Method of flattening steel strip in rolling mill

Abstract

A steel strip is first passed longitudinally in a predetermined travel direction through a nip between a pair of parallel rolls, and then passed downstream in the direction from the rolls over a sensor that engages the strip at a plurality of zones spaced apart on the strip transverse to the direction. The sensor generates respective output signals corresponding to the deviations from planarity of the strip at the zones. A treatment liquid is sprayed uniformly and at a relatively high temperature on the rolls while respective streams of a coolant liquid at a relatively low temperature are directed at regions of the rolls corresponding to the zones. The heat exchange between the streams and the rolls is varied in accordance with the respective output signals to thermally change the diameters of the rolls in the respective regions and thereby eliminate the deviations in planarity detected by the sensor. Thus the treatment liquid can be applied to the rolls at the ideal temperature and rate of flow for best treatment--mainly lubrication and cleaning--of the working rolls. The coolant liquid, which may be the same or a more diluted version of the same liquid, is applied at a much lower temperature and at a rate of flow calculated exclusively to effect the desired heat exchange and thermally change the roll diameter in the respective region to the extent necessary to roll out the deviations in planarity in the respective strip zones.