Effect of torch position and angle on welding quality and welding process stability in Pulse on Pulse MIG welding-brazing of aluminum alloy to stainless steel

In this paper, Pulse on Pulse metal inert gas (MIG) welding-brazing of 6061 aluminum alloy to 304 stainless steel in a lap configuration was developed to investigate the effect of torch position and angle on the welding quality and welding process stability. Images of arc, electrical signals of welding current, and welding voltage were acquired in synchronous modes by a high-speed camera and electrical signal acquisition system, respectively. The obtained results demonstrate that arc shape, macrostructure, microstructure, and mechanical properties are sensitive to torch aiming position when torch travel angle is 20A degrees and work angle is 0A degrees. However, when travel angle is 20A degrees and work angle is 20A degrees, the effect of torch aiming position is insignificant. It is easier to strike arc and maintain it on the surface of aluminum alloy compared to stainless steel. High-strength joints, whose fracture occurred at heat-affected zones of Al alloys at 89 MPa up to 72 % of the tensile strength of Al alloys, have been obtained. Moreover, a comprehensive evaluation method for the welding process stability based on statistical techniques has been proposed. This method can be easily and quickly integrated in real-time control of the welding process, which provides a quantitative guidance in MIG welding-brazing of aluminum alloy to stainless steel.