Welding Aluminum Alloy 6061 with Opposing Dual Torch Gtaw Process

Cracking is a major concern in welding aluminum alloys. Although weld solidification cracks can be eliminated through addition of filler alloy, the additives modify the alloy or base-metal constituents and may not always be desirable. High-energy beam processes, such as electron-beam welding, that result in minimal heat input reduce crack sensitivity, but their high cost limits their applications. In this study, the conventional gas tungsten arc welding process is modified by disconnecting the workpiece from the power supply and placing a second torch on the opposite side of the workpiece. Such a modification changes the direction of the current flow, improves the weld penetration, and reduces the heat input. Using this modified process, 6061-T651 alloy was welded without filler metals. Analysis suggested the reduced heat input, the changed direction of the current flow, and the symmetric heating were responsible for the observed reduction of the cracking sensitivity. INTRODUCTION Cracking is a major concern in welding aluminum alloys. This is due to the relatively high thermal expansion of aluminum, the large change in volume upon solidification, and the wide solidificationtemperature range [1]. High heat inputs, such as high currents and slow welding speeds, increase the thermal stress, solidification shrinkage, and partially melted region, thus contributing to both the weld solidification cracking and HAZ liquation cracking. Although weld solidification cracks can be