Patent ID: 7214899

Claim:
Process for continuous production of longitudinally welded metal tubes, said method comprising the steps of: drawing a metal strip from a strip supply; gradually shaping said metal strip into a slit tube in a shaping station; welding the slit tube in a welding system along edges of the strip; and extracting the welded tube by an extraction device, wherein the welding system is a protective gas arc welding system with several electrodes supplied by separate sources of welding current, and the electrodes are arranged in succession in the direction of production, wherein the welding system has two welding devices, whose electrode tips are directed at a common welding point; that only one of the welding devices is in operation at any given time, while the other welding device is in a standby position; that when an electrode change becomes necessary, an arc of the welding device in the standby position is first struck by means of an auxiliary arc; and that welding current intensity of the welding device presently in operation is then reduced, while the welding current intensity of the welding device in the standby position is simultaneously increased.