Analysis Of Laser-MIG Hybrid Horizontal Welding Characteristics Of Aluminum Alloy

In the horizontal welding process, due to gravity, the molten metal has a tendencyto drip down; consequently weld is prone to having forming defects such as undercutand centerline deviation. For aluminum, due to its low viscosity and good fluidity, it’smore difficult to suppress its forming defects in the horizontal welding process. Forhorizontal welding, current research focuses on the steel materials, horizontal weldingfor aluminum has not been reported. In this paper, laser-MIG hybrid horizontal weldingcharacteristics of2219aluminum alloy were studied.Firstly, the welding process test of aluminum in laser-MIG hybrid horizontalwelding was carried out, using the optimized technology to suppress the forming defects.In the hybrid horizontal welding process of aluminum, the main forming defects includeconcave in back seam, undercut in front seam, and centerline deviation. Using a groovetype, which’s blunted edge is4mm, the groove angles are30°for upper plate and10°for lower plate, can be able to get a seam with good back formation in a suitable energyinput. In the process of cap welding, adoption a non-coplanar arrangement way of laserand wire (horizontal laser-arc distance is3mm, vertical laser-arc distance is2mm) cansuppress the centerline deviation.Secondly, the welding process was monitored to analysis the forming defects’generating mechanism and inhibiting mechanism, by CCD camera and high speed videosystem. The forming of concave is related to the tendency to drip down and internalflow to the pool, which the molten metal on the back weld have. On the other hand, asthe dynamic viscosity coefficient of aluminum is relatively small, so it contributed tothe trend to generating concave defects. The generating of undercut and centerlinedeviation on the front seam mainly due to gravity drip the liquid metal, consequentlythere is an accumulation of the molten metal on the lower areas of the pool, and concaveform on the upper areas of the pool. In addition, gravity will inhibit droplet transfer andmake the transition process instability, thus exacerbating the tendency to form defects.When using an appropriate non-coplanar arrangement way of laser and wire in thehybrid horizontal welding, can steady droplet transfer, change the droplet landingposition and reduce the liquid metal accumulation amount on the lower pool. Therefore,the undercut and centerline deviation will be suppressed.Lastly, microstructure, properties and fracture behavior of laser-MIG hybridhorizontal welding joint of2219aluminum were analyzed. The root layer is composedof fine equiaxed grain which is evenly distributed, but the cap weld is made up ofcolumnar crystal and coarse equiaxed grain. The HAZ can be divided into solid solutionregion and over aging region. Joint fracture occurred in the interface of cap weld and root layer near the upper plate, in these areas, many shrinkage cavities can be observed.In the hybrid horizontal welding joint, porosities are mainly distributed near the fusionline of the upper plate.