轨道客车铝合金厚壁构件激光-MIG复合焊接特性

Welding Characteristics of Laser-MIG Hybrid Welding of Aluminum Alloy Thick-Walled Components for Railway Vehicles

为实现轨道客车铝合金厚壁构件高质量焊接,针对20 mm厚6005A-T6铝合金开展激光-MIG复合焊接特性研究,优化坡口尺寸,分析接头组织特征、硬度分布及拉伸性能。结果表明,U形坡口钝边高度8 mm、组对间隙2 mm时,基于优化复合焊接工艺参数采用三层三道方法可以实现高质量焊接。焊缝中心和熔合线附近组织分别为等轴晶和柱状晶,相比填充焊缝区和盖面焊缝区,打底焊缝区的等轴晶尺寸较粗大且柱状晶区宽度最宽;焊缝区和热影响区硬度低于母材区硬度,熔合线附近硬度最低;接头的平均抗拉强度约为191 MPa,达母材抗拉强度的76%,试样断裂在熔合线附近,总体呈现韧脆混合断裂的特征。

This study investigates the laser-MIG hybrid welding of 20 mm thick 6005A-T6 aluminum alloy components for railway vehicles, aiming to optimize welding parameters and achieve high-quality joints. Through optimization of groove dimensions, the use of a U-shaped groove with a root face height of 8 mm and an assembling clearance of 2 mm, coupled with a three-layer and three-pass welding method, yielded optimal results. The microstructures in the weld center and near the fusion line were equiaxed crystal and columnar crystal respectively. Compared with the filling and covering weld zone, the equiaxed crystal size was coarsest and the columnar crystal zone was widest in the backing weld zone. The microhardness of the weld zone and heat affected zone was lower than that of the base metal, and the lowest microhardness was found near the fusion line. Despite this, the average tensile strength of the joints reached 191 MPa, representing 76% of the base metal strength. The samples fractured near the fusion line, and the fracture morphologies generally showed the ductile-brittle mixed fracture features.