30 mm厚TA1电子束焊接头疲劳断裂原因分析

Fatigue Fracture Analysis of TA1 Electron Beam Welded Joint with a Thickness of 30 mm

为探究30 mm板厚TA1电子束焊接头发生疲劳断裂的原因,针对接头开展疲劳试验,获得了接头S-N曲线及条件疲劳极限。针对TA1接头开展宏观、微观组织及力学性能检验,结合对典型低寿命接头的疲劳试样断口分析,获得了接头断裂特征。结果表明:电子束焊接过程使TA1焊缝及热影响区得到强化,整个接头无明显软化区。TA1电子束焊接头S-N曲线数据符合线性拟合规律,其拟合的疲劳极限值163 MPa,为接头抗拉强度的48.7%,接头疲劳强度符合金属材料结构件疲劳设计的一般规律。焊缝内部"微米级"焊接气孔的存在是导致接头发生疲劳断裂的主要原因,部分接头则是因焊接夹渣导致疲劳断裂。

In order to investigate the causes for fatigue fracture of the electron beam welding(EBW)joints,fatigue tests were conducted on joints welded by TA1 medium plates with 30 mm of thickness,and S-N curve and conditional fatigue limit were obtained.The macro and micro structures and mechanical properties of TA1 joints were investigated,and the fracture characteristics of the joints were obtained by combining fracture analysis of the fatigue specimens for the typical short-life joints.Test results show that electron beam welding(EBW)process can strengthen the weld seam and heat affected zone of TA1 joint,which makes the entire joint without obvious softening zone.The S-N curve data of TA1 electron beam welded joint conform the linear fitting law.The fitted fatigue limit value of 163 MPa is 48.7%of tensile strength of the joint,which conforms the general law of fatigue design of the metal structural parts.The main cause for the joint fracture is the existence of micron-sized welding pores,and the fatigue fracture for part of the joints is due to the existence of welding slag inclusion.