Plate Mill Stand Electric Drive Control in Asymmetrical Rolling Mode of the Strip Plate Head

Abstract

An urgent problem that arises in rolling flat steel and plates is to form the preset strip plate head skid-shaped curvature. This is implemented by adjusting the ratio (mismatch) between the top and bottom rolls in the rolling mill horizontal stands. The factors influencing the strip plate head curvature at the stand exit are listed. With reference to the 5000 plate mill of PJSC Magnitogorsk Iron and Steel Works, the article analyzes the top and bottom roll speeds in the “skid” formation mode. The main drawback of the existing electric drive control system is that it controls the speeds as a function of the difference between their current (actual) values. This results in that the drive of one roll reaches a limitation with loss of motor controllability and uncontrolled strip plate curvature. To eliminate this drawback, a new control method was developed, according to which the electric drive speeds are adjusted as a function of the difference between the speed setpoint signals at the inputs of speed controllers. The control system structure implementing this method is considered. The results of simulating the gripping modes with the simultaneous “skid” formation are presented, and the similar experimental oscillograms are considered. It is shown that with the new control algorithm, the electric drive speeds are closer to their setpoint values. This results in better curvature formation accuracy at lower preset “skid” values. Recommendations for tuning the control system are given.