GMA welding under pure Argon shielding gas atmosphere (pure Argon-GMA welding) is suitable to obtain a high-strength and high toughness welded joint. However, it is difficult that pure Argon-GMA welding is applied practically welding structure because of arc instability. In order to perform stable pure Argon-GMA welding, duplex current feeding GMA welding has been developed. The duplex current feeding GMA welding consists of primary GMA welding current and secondary current by constant-current power resource. The temperature of droplet by duplex current feeding GMA welding is higher than Normal GMA welding. This effect makes that weld penetration depth is deeper, weld bead shape is improved using duplex current feeding GMA welding.
