Corrosion fatigue experiments are carried out on butt welds of G20Mn5QT cast steel and Q345D hot rolled steel in simulated seawater. The cyclic stress versus number of cycles to failure (S‐N) curve was fitted. The mechanism of crack nucleation at different fracture locations and at different stress levels is analysed. The results show that compared with the S‐N curve of laboratory air, for the S‐N curve of simulated seawater, the number of fatigue failure cycles is significantly reduced when the maximum cyclic stress is less than 190 MPa. At higher stress levels, stress concentrations caused by internal defects near the surface of the weld zone and the heat‐affected zone of G20Mn5QT cast steel cause crack nucleation. At lower stress levels, the main reason for crack nucleation is the stress concentration caused by corrosion pitting. However, there are no obvious internal defects in the heat‐affected zone of the Q345D steel, and corrosion pitting is the main cause of crack nucleation. The stress concentrations caused by pitting lead to crack nucleation.

中文翻译：

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腐蚀对G20Mn5QT铸钢和Q345D热轧钢在3.5wt％NaCl溶液中对接焊缝疲劳行为的影响

在模拟海水中，对G20Mn5QT铸钢和Q345D热轧钢的对接焊缝进行了腐蚀疲劳实验。拟合了循环应力与失效循环数（SN）的曲线。分析了不同断裂位置和不同应力水平下的裂纹形核机理。结果表明，与实验室空气的SN曲线相比，SN当最大循环应力小于190 MPa时，模拟海水的曲线可以明显减少疲劳破坏循环的次数。在较高的应力水平下，由G20Mn5QT铸钢的焊接区表面和热影响区附近的内部缺陷引起的应力集中会导致裂纹形核。在较低的应力水平下，裂纹成核的主要原因是由腐蚀点蚀引起的应力集中。但是，Q345D钢的热影响区没有明显的内部缺陷，腐蚀点蚀是裂纹成核的主要原因。由点蚀引起的应力集中会导致裂纹成核。