高强度结构钢及其接头热影响区的疲劳及断裂性能分析

采用焊条电弧焊对48 mm厚高强度结构钢进行焊接，对焊接接头热影响区疲劳裂纹扩展门槛值ΔK_th、裂纹扩展速率da/dN和断裂韧度K_IC进行研究并与基体进行对比。结果表明，在室温下，焊接接头热影响区具有更好的疲劳和断裂性能；随着与熔合线距离的增大，热影响区的组织依次为粗大板条状贝氏体+奥氏体薄膜、细粒状贝氏体、回火索氏体+细粒状贝氏体，硬度逐渐下降；在室温下，焊接接头热影响区和基体冲击韧性均位于上平台。热影响区的残余奥氏体薄膜和硬度较高的贝氏体是影响其疲劳和断裂性能的重要因素。 

Analysis on Fatigue and Fracture Properties of High-strength Structural Steel and its Welded Joint Heat Affected Zone

Welded joint specimens of high-strength structural steel with thickness of 48 mm were prepared by the welding method of SMAW. The fatigue crack threshold ΔK_th, fatigue crack growth rate da/dN and fracture toughness K_IC of welded joint affected zone and base metal were researched and the performance contrast was analysed. The results showed that the welded joint heat affected zone had better performance on fatigue and fracture. With the increase of distance from fusion line, the microstructure of heat affected zone was coarse lath bainte and austenitic film, fine granular bainite, fine granular bainite and tempered sorbite, and the hardness dereased gradually. The impact energy of the two sets of specimens were on the upper platform at room temperature. The residual austenite film and bainite with higher hardness were the main factors that affected the performance of joint.