| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing an electric resistance welded tube excellent in buckling resistant performance, which is hard to be affected by buckling due to an earthquake or a frozen soil after laid as a line pipe. SOLUTION: The method for manufacturing an electric resistance welded tube includes roll-forming a strip 20 and conducting electric resistance welding of the strip while butting the width ends thereof to each other. At a first stand of breakdown rolls in an initial stage of roll forming, a flattened part 13 having an axial width of 5-25% of the width of the strip is formed on the middle part of the roll barrel of a convex roll 11. Thereby, the roll forming is conducted in such a way that the middle part of the width of the strip is not reduced. COPYRIGHT: (C)2009,JPO&INPIT
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