METHOD OF MANUFACTURING MEDIUM-DIAMETER SEAMLESS STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a method of manufacturing a medium-diameter seamless steel pipe by which occurrence of eccentric uneven-thickness defect is detected on the spot during the piercer rolling of the same pipe-making lot in which the thickness of a hollow material on the outlet side of a piercer is 60 mm and the eccentric uneven-thickness of a material to be rolled following the detected material to be rolled is reduced.;SOLUTION: In the method of manufacturing the medium-diameter seamless steel pipe including piercer rolling by which inclined rotation piercing rolling is performed with upper and lower rolls 31, 32 and a plug 11 between the rolls while guiding the material 9 to be rolled with right and left shoes 33, 34, the shoe load during the piercer rolling is monitored and, when monitored values are ≥1 ton in both the right and the left shoes and the difference between the right and the left shoes exceeds a prescribed tolerance, before starting the rolling of the next order of the rolling order exceeding the tolerance, the shoe position is changed so that the shoe on the side of small shoe load is kept away from the pass center line to a position where the shoe load becomes 1 ton and the shoe on the opposite side is brought close to the pass center line in the range where the outside diameter of the hollow material on the outlet side of the piercer is not less than the target.;COPYRIGHT: (C)2008,JPO&INPIT