METHOD FOR CONTROLLING WALL-THICKNESS OF SEAMLESS STEEL TUBE

摘要

PROBLEM TO BE SOLVED: To provide a method for controlling the wall-thickness at tube ends by which thickening in both tube end parts is suppressed while minimizing the deterioration of thickness deviation in the peripheral direction. SOLUTION: By changing the screw-down locations of grooved rolling rolls when biting a tube and tailing off the tube at rolling with an elongating mill and increasing and decreasing the speed of revolution of the grooved rolling rolls when biting the tube and tailing off the tube at rolling with a sizing mill, the thickening of the wall-thickness in the tube end parts that is generated at the rolling with the sizing mill is suppressed.