Process optimization of Pinless Tool Friction Stir Spot Welding of Aluminium alloys

Abstract

Metal joining techniques have been of greater importance in the automobile, aerospace newlineand shipbuilding industries. Joining techniques like Tungsten inert gas welding (TIG), newlinemetal inert gas welding (MIG), Resistance spot welding (RSW) and Self-piercing rivets newline(SPR) were employed to join the structural applications of similar and dissimilar materials newlinein vehicular applications. However, problems like solidification-based defects like newlinecracks, voids and pores, electrode wear and weld distortion have made the industry look newlinefor alternative joining techniques. An alternate welding methods like Friction stir spot newlinewelding (FSSW) is getting rapid deployment to join automobile and aerospace structures newlinedue to its reduced welding time, energy consumption and enhanced weld properties. newlineFSSW is a solid-state metal joining technique, which uses thermo-mechanical newlineenergy to join the weldments. In this work, 1 mm thick Al 5754 and Al 6061 alloys newlineused in like doors, hoods, body in white (BIW) and skin structures of an automobile are newlinejoined by FSSW using pin-less tools. The pin-less tool FSSW, PTFSSW technique was newlineidentified as the best-suited technique to eliminate the exit-hole in conventional FSSW newlinejoints. The sheet position was observed to influence the mechanical strength of the PTFSSW newlinejoints. The welding parameters in PTFSSW of Al 6061 and Al 5754 with Al 6061 newlineon top were optimized using Response surface methodology, RSM with Box-Behnken newlineexperimental design. The welding parameters, shoulder diameter, shoulder piercing newlinedepth, dwell time, rotational speed and plunging rate were observed to influence the newlinemechanical strength and welding temperature in PTFSSW joints. The maximum tensile newlineshear force, Ts of 6.33 kN, was obtained at 700 RPM, 0.04 mm/s, 8 s, 0.5 mm and newline25 mm shoulder diameter. The temperature measured during the PTFSSW by infrared newlinethermal imaging increased with the increase in shoulder piercing depth.The maximum newlinetemperature during PTFSSW of 384 °C was observed at 0.75 mm shoulder piercing newlinedepth and the rotational speed of