Ultra-NGLW is an advanced welding technology for thick bainitic steel,which has the advantages of low heat input,low stress and deformation of welded joints.By conducting high-frequency tensile fatigue tests on Ultra-NGLW joints with different"filling-bottoming"ratios,S-N curves of 10 mm thick Ultra-NGLW joints with different wire filling depths were plotted,and by comparing and analyzing the S-N curve and fatigue fracture characteristics,the main factors affecting the fatigue performance of Ultra-NGLW joints were identified.The experimental results indicate that as the depth of laser wire filling increases,the fatigue performance of the joint gradually decreases.When the filling depth is 0 mm,the fatigue strength of the joint is 337.5 MPa,while the filling depth reaches 5 mm,the fatigue strength tends to stabilize at around 270 MPa.The fatigue source of Ultra-NGLW joints is mainly welding defects such as pores and inclusions in the coarse-grained and fusion zones of the weld.Under the action of high-frequency tensile fatigue cyclic loads,more cracks are formed in the martensitic brittle hard structure in the coarse-grained zone,causing the fatigue source cracks to rapidly expand and connect the cracks in the brittle hard structure until the joint fails.
关键词
超窄间隙激光填丝焊/疲劳强度/S-N曲线/疲劳断口/贝氏体高强钢
Key words
ultra-narrow gap laser welding/fatigue strength/S-N curve/fatigue fracture/bainite high-strength steel
维普
万方数据