JPH05237532

PURPOSE:To control the thickness in the stretch reducing operation with high accuracy. CONSTITUTION:When the stretch reduction of a tube stoch 122 is executed by a continuous multiple reducer, the physically applicable maximums tensile factor is obtained for the respective stands based on the outer diameter and the thickness of the tube before' and after the stretch reduction in the respective stands and the target outer diameter and the target thickness of the finished tube. The actual tensile factor is obtained which is practically applied based on the outer diameter and the thickness of the tube before and after the stretch reduction for the respective stands when the first tube is stretch-reduced, the roll speed, and the actual outer diameter and the actual thickness of the finished tube. For the stands where the actual tensile factor exceeds the maximum tensile factor, the actual tensile factor is corrected so as not to exceed the maximum tensile factor, and the actual tensile factor for other respective stands are obtained and set so as to obtain the finished tube of the target thickness based on the corrected actual tensile factor.