Comparative study on arc shape and droplet transfer under different shielding gas compositions of Ar/He/CO₂ in pulsed GMAW

In order to solve the problems of poor arc stiffness and unstable droplet transfer in pulsed GMAW with high-strength Cr-Ni austenitic stainless welding wire, the arc shape and droplet transfer under different shielding gas compositions of Ar/He/CO₂ were investigated by the high-speed camera for optimization of mixed gas composition in this paper. The results showed that in pure Ar, the metal transferred easily but with arc wandering and poor arc stiffness. The arc stiffness and arc energy density increased with the addition of He and CO₂. The droplet transfer was multiple drops per pulse type that one big drop was followed by several small drops. With the increase of the He volume fraction, the size of the first big drop increased. The CO₂ was good at overcoming the cathode spot drift, but the volume fraction can not exceed 5%. The ideal mixed shielding gas was 40%Ar+58%He+2%CO₂ for good arc stiffness and stable droplet transfer in this pulsed GMAW by using austenitic stainless welding wire.