PREVENTING METHOD FOR RUPTURE OF WELD ZONE OF STEEL STRIP IN FORGE-WELDED TUBE FORMING MILL

摘要

PURPOSE:To prevent rupture of a weld zone in a forge-welded tube forming mill, and to improve the yield, by continuously detecting the thickness of a steel strip in order to discriminate the weld zone, and by tracking this weld zone as far as the inlet of the pipe forming mill, and by controlling the tension between each rolling stand. CONSTITUTION:The thickness of the steel strip 7 is continuously measured by the detector 5 on the inlet side of the preheating furnace 8; the detected thickness is inputted to the weld zone detector 1 which thereupon detects the weld zone from the variation in the detected thickness. Thus detected weld zone is tracked by the tracking device 2 receiving a signal from the strip speed detector 6; this tracking signal is sent to the pipe forming mill 13. Thereupon the rotary gradient operator 3 stores this tracking signal and operates the number of rotation of each roll on the basis of the interstand tension effected when the weld zone passes over each stand. The result of this operation is inputted to the controller 4 which thereupon gives a command signal Ri for the number of rotation to each rolling stand. Besides, the controller 4 receives the actually measured number of rotation Si of each rolling stand and controls it to the aimed number of rotation. By the present method, the rupture of weld zones in the rolling stand is entriely eliminated.