Optimization of an innovative hybrid welding process for structural fabrication

Abstract

A hybrid laser arc welding (HLAW) process was formed by combining the laser beam welding (LBW) process with the gas metal arc welding (GMAW) process. The three principle advantages offered by combination are deep weld penetration, low distortion and filler metal addition. Hybrid welding was applied for the fabrication o f tee-joints of 8-mm thick carbon steel alloys. Since the helium shielding gas usually employed with the CO2 laser welding process is incompatible with spray transfer gas -metal arc welding, one of the modern short-circuiting variants of the process was employed. It was found that this hybrid combination allowed spatter-free metal transfer with helium gas, while maximizing the penetration of the 5 kW laser beam. In order to optimize the welding process, designed experiments were employed to investigate the effect of key process variables including laser and arc process orientations and locations relative to each other and to the weld joint, process travel speed and material fixturing tolerance. A full - quadratic model was found to fit the experimental data acceptably well and the sensitivity of various process parameters was examined by calculating the slope of the response surface at the optimum settings in the direction of each parameter. The shape of the weld bead on the backside of the weld joint most strongly impacted by GMAW torch-seam horizontal offset and travel speed. The back-bead quality was moderately sensitive to fixturing accuracy (i.e. the tilt angle of the web plate). At optimum process conditions, it was found that the backside weld bead was acceptably smooth and defect-free.A hybrid laser arc welding (HLAW) process was formed by combining the laser beam welding (LBW) process with the gas metal arc welding (GMAW) process. The three principle advantages offered by combination are deep weld penetration, low distortion and filler metal addition. Hybrid welding was applied for the fabrication o f tee-joints of 8-mm thick carbon steel alloys. Since the helium shielding gas usually employed with the CO2 laser welding process is incompatible with spray transfer gas -metal arc welding, one of the modern short-circuiting variants of the process was employed. It was found that this hybrid combination allowed spatter-free metal transfer with helium gas, while maximizing the penetration of the 5 kW laser beam. In order to optimize the welding process, designed experiments were employed to investigate the effect of key process variables including laser and arc process orientations and locations relative to each other and to the weld joint, process travel speed and material fixturing toler...