高速列车铝合金车体典型接头激光-MIG复合焊接特性研究

Study on Laser-MIG Hybrid Welding Characteristics of Typical Joints of Aluminum Alloy Carbody for High Speed Train

针对传统高速列车3 mm厚A6N01S-T5铝合金型材典型接头结构开展激光-MIG复合焊接试验,优化复合焊接工艺参数,分析接头组织性能,研究激光-MIG复合焊的工程适应性。结果表明,在最佳工艺参数下,焊缝成形良好、无气孔缺陷。焊缝中心为树枝状铸态组织,靠近熔合线焊缝为柱状晶组织,熔合区较窄但热影响区存在晶粒轻微粗大现象;焊缝区硬度低于母材区,硬度最小值位于熔合线附近的热影响区;最佳工艺参数下接头的平均抗拉强度为204.6 MPa,达到母材的83.5%;断裂发生在熔合线附近,断口形貌呈现典型的塑性断裂特征;接头的弯曲性能良好;组对间隙小于1.0 mm时,最佳工艺参数具有通用性,焊缝成形及接头抗拉强度良好;组对间隙增至1.5 mm时,优化工艺参数焊缝成形及接头抗拉强度依然良好。结果表明,激光-MIG复合焊对高速列车铝合金车体典型接头具有良好的焊接可行性和工程适应性。

In order to expand the application of laser-MIG hybrid welding in the manufacturing of aluminum alloy car body profiles for high-speed train, laser-MIG hybrid welding experiments were carried out to weld typical joint structure of traditional 3 mm thick A6N01S-T5 aluminum alloy for high speed train in this work. The welding parameters were optimized,structure and property of joints were analyzed. The adaptability of the laser-MIG hybrid welding was also studied. The experimental results show that the weld is well formed and no porosity defects with the optimal welding parameters. The microstructure in the weld center is dendritic as cast structure, and near the bond line is columnar crystal structure. The bond zone is narrow, but the grain is slightly coarse in the heat-affected zone. The hardness of weld metal zone is lower than that of the base metal zone, and the minimum hardness is located in the heat-affected zone near the bond line. The average tensile strength of the joints with the optimal welding parameters is 204.6 MPa, reaching 83.5% of the base metal. The tensile sample fractures near the bond line and the fracture morphology showes typical plastic fracture characteristics. And the joint has good bending performance. The optimal welding parameters has good commonality when the assembled gap less than1.0 mm, the weld formation and joint tensile strength are fine. The weld formation and joint tensile strength are still good with the optimized welding parameters when the assembled gap increases to 1.5 mm. The research results prove that the laser-MIG hybrid welding has good feasibility and adaptability in typical joints of aluminum alloy carbody for high speed train.