Design for Improvement of Finished Tube Pass for Stretch Reducing Mill of Φ89 mm MPM Plant

Addressing the shortcomings of the conventional design method for the finished tube pass of the stretch reducing mill,a new design method is proposed. The method involves an oval pass for finished tube-rolling instead of the original round one. The pass ovality is bigger than 1 (1.007 ~ 1.010),and the short semi-axis is equal to that of the pass just before the finished tube pass. The pass before the finished tube pass is also oval,but the ovality is properly reduced. Relevant operation practice shows that thanks to this new design method,outside diameter ovality of the pipe can be effectively controlled so as to tighten the O.D. tolerance,increase the life span of the finished tube pass by 1/3,and minimize the occurrence of linear rolling mark of the finished tube.