Constraining the dynamic torque of a rolling mill stand drive

We herein consider issues of limiting the dynamic loads in the electromechanical systems of horizontal rolls in the stand of a plate mill. It is shown that shock loads mainly occur during gripping due to gaps in spindle connections; the size of the gap depends on how worn-out those spindles are. We analyze a method of limiting such dynamic loads that consists in gripping workpieces while accelerating the electric drive. We also task ourselves to prove the feasibility of implementing this method at the 5000 rolling mill employed by PJSC Magnitogorsk Iron and Steel Works (MMK). We present the oscillograms of workpiece gripping in accelerated and decelerated modes; those oscillograms prove how efficient pre-setting the gap size is. The paper contains a control chart that ensures electric drive acceleration before gripping. We have developed a mathematical model of the dual-mass electromechanical roll system for reversing stands and present herein the parameters of the simulated object. The proposed dynamic load limitation has been simulated. We herein specify a minimum timeframe between the onset of pre-acceleration and the load application moment, which timeframe is necessary for angular gaps to be fully closed. The timeframe value is explained. We have also implemented the developed speed control algorithms in the APCS of the 5000 rolling mill stand. The paper presents the torque and speed oscillograms for the workpiece gripping. It is proved that the torque overshoots in the upper- and lower-roll electric drives is reduced to acceptable levels by this method. We also analyze the oscillograms of the lower-roll drive parameters obtained over nine reversing-rolling passes. It is confirmed that the dynamic torque of grip does not exceed 25% of the steady-state torque. We thus conclude that this speed control method has proven efficient for the stand electric drives of the 5000 mill. Expanded implementation of this method in the existing hot-rolling mills is noted as practical.