Song Yan, Chai Mengyu, Han Zelin
School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
Materials (Basel). 2021 Mar 1;14(5):1159. doi: 10.3390/ma14051159.
In this work, the fatigue crack growth (FCG) behavior and fatigue damage mechanism of the 2.25Cr1Mo0.25V steel welded joint used in hydrogenation reactors were investigated. The multi-pass welding was carried out to manufacture the welded joint using the combined shielded metal arc welding (SMAW) and submerged automatic arc welding (SAAW) processes. The FCG behavior of different zones in the welded joint, including the base metal (BM), the heat-affected zone (HAZ) and the weld metal (WM), were studied by compact tension tests. Moreover, the acoustic emission (AE) technique was used to monitor AE signals generated from FCG process for further understanding FCG behavior and fatigue mechanisms. Additionally, the microstructures and fracture surfaces of different specimens were observed by optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that the microstructure of BM is fine granular bainite, while the WM shows coarser bainite grains. The HAZ exhibits the most significant inhomogeneity with large dispersion of grain size. FCG results showed that the HAZ exhibits much higher fatigue crack growth rate (FCGR) at low Δ values, while the BM shows the most superior fatigue resistance. The AE technique is successful in monitoring and identifying damage evolutions during the FCG process. Moreover, an enhanced AE activity is observed in FCG of the WM specimen, which is attributed to the combined influence of the formation of numerous secondary cracks and coarse-grained microstructures.
在这项工作中，对用于加氢反应器的2.25Cr1Mo0.25V钢焊接接头的疲劳裂纹扩展（FCG）行为和疲劳损伤机制进行了研究。采用手工电弧焊（SMAW）和埋弧自动焊（SAAW）相结合的工艺进行多道焊接以制造焊接接头。通过紧凑拉伸试验研究了焊接接头不同区域（包括母材（BM）、热影响区（HAZ）和焊缝金属（WM））的FCG行为。此外，使用声发射（AE）技术监测FCG过程中产生的AE信号，以进一步了解FCG行为和疲劳机制。另外，通过光学显微镜（OM）和扫描电子显微镜（SEM）观察不同试样的微观结构和断口表面。结果表明，母材的微观结构为细粒状贝氏体，而焊缝金属显示出较粗大的贝氏体晶粒。热影响区表现出最显著的不均匀性，晶粒尺寸分散性大。FCG结果表明，在低Δ值时，热影响区表现出更高的疲劳裂纹扩展速率（FCGR），而母材表现出最优异的抗疲劳性能。AE技术成功地监测和识别了FCG过程中的损伤演变。此外，在焊缝金属试样的FCG过程中观察到增强的AE活动，这归因于大量二次裂纹的形成和粗晶微观结构的综合影响。
