| 摘要 |
PROBLEM TO BE SOLVED: To achieve the reduction of cold pipe straightening man-hours after pipe expanding and an improvement in a product yield by solving the problem that push crack marks are generated in a direction perpendicular to the longitudinal direction of the steel pipe on the side faces of the steel pipe after the pipe expanding in the stage of expanding the pipe end in the final after starting the pipe expanding from the central part in the longitudinal direction of the steel pipe. SOLUTION: The pipe expanding method of the UOE steel pipe is characterized by forming a tapered part satisfying the conditions of formula A≥Dx0.009 and formula B≤5.5% on the pipe end side of the pipe expanding part formed by a pipe expanding pass. In the formulas, D is an inner diameter of the material to be expanded; A is a level difference of the tapered part, and B is an amount of taper. COPYRIGHT: (C)2008,JPO&INPIT |
