High-Cycle Fatigue Performance of the Heat-Affected Zone of Q370qENH Weathering Bridge Steel

Q370qENH weathering steel is widely used in railway steel bridge construction in China. However, limited research has been conducted on the high-cycle fatigue damage of the welds in weathering steel railway bridges. In this study, we conducted experimental tests to investigate the high-cycle fatigue performance of the heat-affected zone (HAZ) of Q370qENH weathering steel. First, coarse-grain heat-affected zone (CGHAZ) specimens and fine-grain heat-affected zone (FGHAZ) specimens of Q370qENH were obtained using the welding thermal simulation (WTS) method. The accuracy of the WTS method was verified through metallographic structure analysis. Subsequently, high-cycle fatigue tests were conducted on the base material and HAZ specimens. Then, probabilistic stress-life (P-S-N) curves and the fatigue strength of the Q370qENH HAZ were obtained. Finally, the fatigue extension mechanism of the Q370qENH HAZ was examined. The results indicate that the WTS method effectively produced HAZ specimens matching the welded joint. The fatigue life of the FGHAZ and CGHAZ specimens was significantly lower than that of the Q370qENH base material. The fatigue strength of HAZ was approximately 80% of that of the base material, and the fatigue strength reference of the Q370qENH HAZ was 175 MPa. Furthermore, the CGHAZ specimens were more prone to slip and had a high stress concentration at the microscopic scale, leading to their inferior fatigue performance. This study provides a valuable reference for the design and fatigue assessment of weathering steel bridges.