Optimization of shielding gas composition in narrow gap GMA welding based on response surface methodology

In gas metal arc (GMA) welding, metal melting behaviors and the weld geometry are affected by shielding gas composition. Helium has special properties, and it can provide a wider weld profile which is benefit for increasing sidewall penetration in narrow gap GMA welding. In this paper, helium was added to shielding gas for narrow gap GMA welding to ensure the sidewall penetration. The shielding gas includes argon, carbon dioxide, and helium. The statistical models for narrow gap GMAW weld bead sidewall penetration were developed using response surface methodology (RSM) based on central composite design (CCD). The developed models were checked for their adequacy and significance by analysis of variance (ANOVA), and the effects of shielding gas composition on sidewall penetration were studied. Finally, the optimal ternary shielding gas for tandem narrow gap GMA welding were obtained by numerical optimization using RSM. The largest sidewall penetration can be obtained under 79%Ar–10%CO2–11%He.