| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a circumferential weld joint of a high strength steel pipe for a pipeline suppressing deterioration of low cycle fatigue resistance, preventing a fatigue crack, and excellent in low cycle fatigue resistance. <P>SOLUTION: A weld metal part 21 of a circumferential weld part 20 includes a lower weld metal 21A positioned on a steel pipe inner surface side and an upper weld metal 21B positioned on a steel pipe outer surface side. The relationship among the Vickers hardness Hv (BM) of a base material, the Vickers hardness Hv (WM1) of the lower weld metal 21A, and the Vickers hardness Hv (WM2) of the upper weld metal 21B satisfies the following formula, äHv(WM1)≤0.8Hv(BM)}, or the following formula, äHv(WM2)≥Hv(BM)}. The relationship between a longitudinal cross sectional area S (WM1) of the lower weld metal 21A and a longitudinal cross sectional area S (WM1+WM2) of the whole of the weld metal part 21 satisfies the following formula, ä0.4≤S(WM1)/S(WM1+WM2)≤0.6}. <P>COPYRIGHT: (C)2012,JPO&INPIT |
