| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-strength welded steel tube, which, when manufacturing a welded steel tube using a UOE process, prevents buckling, does not generate a crack from a weld part, such as a toe crack and an expanding crack, and does not cause tack-welding failure of the weld part. SOLUTION: In manufacturing a welded steel tube, the end parts of a steel plate is bent with a pressing force w(N/mm) of an upper die, which is determined by A≤w≤B or A×C≤w≤B/D, while satisfying the following formulae 0.15≤R<SB>1</SB>/D≤0.25 and 135≤u≤160, wherein, R<SB>1</SB>(mm) is the radius of curvature of the working face of an upper die, u(mm) is the distance in the horizontal direction from the center of curvature of the upper die to the end part of the steel plate, s(MPa) is the tensile strength of the steel plate, D(mm) is the outer diameter of the welded tube to be manufactured, A and B are the values determined by s, and C and D are the values determined by s and u. COPYRIGHT: (C)2008,JPO&INPIT
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