Study on the arc behavior and mechanical properties of energy-efficient hybrid CMT-Pulsed gas metal arc narrow gap mild steel welds

Abstract The novel hybrid cold metal transfer (CMT) – Pulsed gas metal arc welding (P-GMAW) process was used to perform the narrow gap welding of mild steel plates. A systematic approach was followed to select the working values of numerous process parameters using high-speed images of the welding arc in synchronization with the welding current and voltage. Further, emphasis was given to understanding the influence of pulse frequency on the complex arc and metal transfer behavior in the narrow gap and its subsequent effect on the side wall fusion and mechanical properties of weld joints. The root pass was deposited using CMT process, while the filling and closing passes were deposited using P-GMAW process to minimize the incomplete fusion between the layers keeping the overall heat input lower. A decrease in the narrow gap distance and an increase in the arc oscillation amplitude and welding voltage resulted in severe arc climbing over the facing surface, an inadequate fusion between the layers, and incomplete side wall fusion. Simultaneously decreasing the number of passes and welding speed engendered the overhead flow of the molten pool and hindered the heat transfer from the arc to the already deposited layer resulting in the lack of fusion. Pulse current and duration directly affect the welding arc lengths, resulting in higher welding arc deflections to the side walls in the case of lower pulse frequencies. The controlled welding arc deflections, molten metal transfer, and inter-pulse cooling displayed a noticeable effect on the mechanical properties of the weld joint.