The Research Application Of Hydraulic Looper In Meishan Hot Strip Mill

In current hot strip mill, Looper is a very important system. Its performance has directly effect on the product quality. It has gone through the stages of pneumatic, electric and hydraulic. The method of looper control has developed from open-loop control and close-loop control to Total Digit Variable control, which is to improve the product quality.After the modification in 2002, Meishan Hot Strip Mill used advanced hydraulic looper devices and the Total Digit Variable control system. In order to master this new technique and raise product quality better, By analyses of the looper control theory, mathematics model of loop and tension are obtained, and the advanced experience in the application is summarized.Hot strip rolling technique is developed based on the "mass flow balance"theory. During the rolling, the influence of slab size and temperature always leads to unbalance mass flow. So certain measures should be taken to control the balance of mass flow in every mill stand. On one side, the looper's invariable tension guarantees tensity and stability of the strip. On the other side, the loop control will correct stand speed to make the flow balanced. The mathematics models of loop and torque show that in every mill stand, the variable loop "ΔL" has the relation of direct proportion with square of the angle when the looper rotated from pass line. So "θ", the angle the looper rotated is the embodiment of looper height. The loop control also means control of the angle that looper rotated. Meanwhile the torque control supplies not only the invariable tension, but also gravity compensation of looper and so on. The total torque is a function of angleθ. During application, the looper height is coupled with tension control, which needs special attention.