Improvement in Strip Shape by Modified Roll Bending System

摘要

The Tandem Cold Mill(TCM) and Skinpass Mill(SPM) of Bokaro Steel Plant are not equipped with latest gadgets for correcting the roll gap profile like Roll shifting, Roll crossing, Roll bending and Differential roll cooling for controlling symmetrical/ asymmetrical shape defects. The mill is provided with electro-mechanical screw-down system for the purpose of adjusting the roll gaps. The hydraulic roll bending system is operating at a hydraulic pressure either 0 bar or 100 bar to control the shape deformities with the help of hydraulic roll force cylinders placed on the bottom work roll chocks. With the actuation of these cylinders facilitates the roll separating in two points (no separation at Obar and maximum separation at lOObar. There is no provision for variation of the roll separating force in between (Obar to lOObar) by the operator. In order to meet the customer's requirement and improve the strip shape of CR strip, the step-less control of work roll balancing system has been carried out to correct the strip shape as far as possible by manually. The modified roll bending system with variable roll separating force has been commissioned at the last stand of TCM-I and SPM-I, to correct the shape defects as far as possible. The variable hydraulic pressure is being controlled by voltage regulation, which regulates the port openings of the proportionate pressure re-lieving-reducing relief valve. The modified work roll bending system has resulted in improved strip flatness and helped to correct the edge waviness and centre buckles on the strip.