焊缝余高及去应力退火对X80钢管焊接接头疲劳性能的影响

Effects of Weld Reinforcement and Stress Relief Annealing on Fatigue Properties of Welded Joint for X80 Steel Pipe

采用MTS Landmark 370型疲劳试验机研究了焊缝余高和去应力退火对X80大变形管线钢管焊接接头的拉-拉疲劳寿命的影响;采用显微硬度计和扫描电镜分析了焊接接头的硬度及疲劳断口形貌。结果表明:去除焊缝余高和去应力退火处理能够延长X80大变形管线钢管焊接接头的疲劳裂纹萌生寿命,提高其疲劳寿命;疲劳裂纹在内焊缝的焊趾处或者紧邻熔合线的热影响区萌生;焊缝余高引起的应力集中和热影响区软化是影响疲劳裂纹萌生的关键因素。

The effects of weld reinforcement and stress relief annealing on fatigue life of welded joints of X80 steel pipe were investigated by a MTS Landmark 370 servo-hydraulic universal testing machine.The hardness and fatigue fracture morphology of the welded joints were investigated performed on micro-hardness test and scan electronic microscope(SEM).The results show that the fatigue life and fatigue crack initiation life of the welded joints of X80 steel pipe increase after removing reinforcement and annealing.The fatigue crack initiation of the X80 welded joint specimens occurs at the inside weld toe or heat-affected zone(HAZ)near weld-fusion line.Stress concentration resulting by the weld reinforcement and HAZ softening are the key factors of affecting fatigue crack initiation.