Interstand tension control method and apparatus for tandem rolling mills

Abstract

In a tandem rolling mill consisting of at least a first rolling stand and a second rolling stand, the interstand tension is controlled by the steps of detecting the rolling force P.sub.10 and rolling torque G.sub.10 at the first rolling stand after a workpiece is fed into the nip between the rolls of the first rolling stand but before the workpiece is fed into the nip between the rolls of the second rolling stand, storing in a memory the ratio G.sub.10 /P.sub.10 representative of the reference torque arm value for the first rolling stand in a tension-free state, detecting the rolling forces P.sub.1B, P.sub.2B and rolling torques G.sub.1B, G.sub.2B at the respective rolling stands immediately after the workpiece is fed into the nip between the rolls of the second rolling stand, computing the reference torque arm value G.sub.20 /P.sub.20 for the second rolling stand in a tension-free state on the basis of these detected values, and controlling the rolling speed of the first or second rolling stand so that (G.sub.10 /P.sub.10) - (G.sub.1 /P.sub.1) representing the deviation of the torque arm value detected at the first rolling stand in rolling operation from the reference torque arm value G.sub.10 /P.sub.10 stored in the memory is equal to (G.sub.20 /P.sub.20) - (G.sub.2 /P.sub.2) representing the deviation of the torque arm value detected at the second rolling stand in rolling operation from the reference torque arm value G.sub.20 /P.sub.20, whereby the workpiece can be rolled tension-free.