Circumferential welded joint of line pipe, method of forming circumferential welded joint of line pipe, and line pipe
Abstract:
A circumferential welded joint of a line pipe is formed by butting against each other end portions of steel pipes having a yield strength according to 5L Specification of API Standards not smaller than 555 N/mm2 and welding the butted portions in a circumferential direction. A joint strength ratio σmatch=(TS-w/TS-b)·(YS-w/YS-b) represented by a product of a ratio between a tensile strength TS-w of a weld metal and a tensile strength TS-b of a base material and a ratio between a yield strength YS-w of the weld metal and a yield strength YS-b of the base material, and a critical equivalent plastic strain εp-cri [%] for ductile crack generation in a base material heat affected zone satisfy Equation (1), and the yield strengths YS-w, YS-b of the weld metal and base material satisfy Equation (2). σmatch>4.85εp-cri−0.31  (1) YS-w/YS-b≧1.0  (2)
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