Abstract
Gas metal arc welding applying inert gas typically required a little oxidizing gas for arc discharge stabilization; thus, oxide precipitates potentially deteriorating fracture toughness of the weld metals are generated. Although several methods in order to reduce oxide gas in the MIG welding have been proposed for example applying a special nozzle which can add inert and active gas separately, it has not been applied for actual production yet, since weld flaws may occur due to arc destabilization especially in groove welding. Therefore, the aim of this research is to achieve the low oxidation defect free weld in narrow groove welding by applying a special nozzle we developed. The effect of the nozzle, influence of arc phenomenon such as pulsed arc and continuous current arc, and frequency of adding active gas were investigated by some experiences and simulations. As the results the nozzle is contributed arc stability and pulsed arc affects arc length and time for arcing and the active gas adding frequency of 30Hz provide maintaining higher CO2 molar fraction in arc. Extremely low oxygen in weld metals were achieved by those combined effects.
