The transfer modes in gas metal arc welding have important effects on welding quality. However, present study of metal transfer modes is not yet fully understood. In this study, welding arcs was visualised using the optical emission spectroscopy technique. The carbon steel wire electrode was used for welding with 80% Ar + 20% CO2 shielding gas. The results showed that the globular to spray transition current was 330–350 A. During globular to spray transition, argon,CO2 and Fe plasma tended to gradually change from localising near the arc axis to a two-layer structure having 11,000 K in high-temperature region away from the arc axis and around 7000 K in low-temperature region near the arc axis.
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