Tandem gas metal arc welding

A method for tandem gas metal arc welding using a consumable leading electrode and a trailing electrode, the method comprising:n(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.

A torch for tandem gas metal arc welding,nwherein the torch has a consumable leading electrode and a trailing electrode inside a nozzle, and a partition for preventing mixing of a shielding gas for the consumable leading electrode and a shielding gas for the trailing electrode,the shielding gas for the consumable leading electrode is a two-component mixed gas containing argon and carbon dioxide, or a three-component mixed gas containing argon, carbon dioxide, and oxygen,the shielding gas for the trailing electrode 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, anda concentration of carbon dioxide in the shielding gas for the trailing electrode is lower than a concentration of carbon dioxide in the shielding for the leading electrode.

A torch for tandem gas metal arc welding, comprising,na protection cover for shielding a molten pool which is fixed backward in a welding direction,the torch further has a consumable leading electrode and a trailing electrode inside a nozzle,a shielding gas for the consumable leading electrode is a two-component mixed gas containing argon and carbon dioxide, or a three-component mixed gas containing argon, carbon dioxide, and oxygen,a shielding gas for the trailing electrode 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, anda concentration of carbon dioxide in the shielding gas for the trailing electrode is lower than a concentration of carbon dioxide in the shielding gas for the leading electrode.

An apparatus for tandem gas metal arc welding comprising:na welding torch including a consumable leading electrode and a consumable trailing electrode;a shielding gas supplying source for supplying a shielding gas to each, of said leading and trailing electrodes, the shielding gas for the leading electrode is a two-component mixed gas containing argon and carbon dioxide, or a three-component mixed gas containing argon, carbon dioxide, and oxygen, and a shielding gas for the trailing electrode 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 a concentration of carbon dioxide in the shielding gas for the trailing electrode is lower than a concentration of carbon dioxide in the shielding gas for the leading electrode; anda switching device for switching between the shielding gas supplied to the leading electrode and the shielding gas supplied to the trailing electrode.