Patent ID: 8461471

Claim:
A method for tandem gas metal arc welding using a consumable leading electrode and a trailing electrode, the method comprising: (a) sending a first welding current to a wire supplying device of the consumable leading electrode; (b) sending a second welding current to a wire supplying device of the trailing electrode; (c) applying the first and second welding currents to respective welding wires of the leading and trailing electrodes; (d) supplying a shielding gas for the consumable leading electrode that is a two-component mixed gas containing argon and carbon dioxide, or a three-component mixed gas containing argon, carbon dioxide, and oxygen; and (e) supplying a shielding gas for the trailing electrode that is argon, a two-component mixed gas containing argon and carbon dioxide, a two-component mixed gas containing argon and oxygen, or a three-component mixed gas containing argon, carbon dioxide, and oxygen, wherein steps (d) and (e) are practiced such that the concentration of carbon dioxide in the shielding gas for the trailing electrode is lower than the concentration of carbon dioxide in the shielding gas for the leading electrode.