摘要
为探究激光-电弧复合焊接技术在转向架结构中应用的可能性,以 20 mm厚的Q345E钢T形接头为研究对象,开展了激光-电弧复合焊接试验,并采用单点法和升降法进行疲劳性能测试.结果表明,当指定循环次数为 5×106 时,复合焊接头的中值疲劳强度为 148.3 MPa,循环 2×106 时的条件疲劳强度为 181.5 MPa,比相应的电弧焊接头提高 39.6%,且焊接组织更细小,提高了裂纹萌生过程中所需的疲劳循环次数.疲劳裂纹形貌特征表明,T形接头的疲劳裂纹起源于封底焊缝焊趾处,瞬断区为韧性断裂模式,复合焊接头疲劳性能提高的原因在于其封底焊缝焊趾处具有较小的应力集中系数,且焊缝微观组织由更为细小的晶内铁素体组成,能够有效避免疲劳裂纹过早萌生,并阻碍疲劳裂纹扩展.
Abstract
To investigate the feasibility of laser-arc hybrid welding in bogie structures,the hybrid welding of 20mm-thick Q345E steel T-joints was carried out.The fatigue properties were assessed using both the single-point method and the staircase method.The findings reveal that,at the specified 5 million cycles,the median fatigue strength of the hybrid-welded T-joint stands at 148.3 MPa.Furthermore,the conditional fatigue strength at 2 million cycles is 181.5 MPa,representing a remarkable 39.6%increase compared to the corresponding arc-welded T-joint.Analysis of the fatigue crack morphology indicates that the fatigue crack originates at the root weld toe,with the instantaneous fracture region displaying a ductile fracture mode.The enhanced fatigue properties of the hybrid-welded T-joint can be attributed to the reduced stress concentration factor at the root weld toe and the finer weld microstructure composed of the intragranular ferrite.This prevents premature fatigue crack initiation and hinders fatigue crack propagation.
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