| 摘要 |
A process for the continuous production of longitudinally welded metal tubes where a metal strip ( 1 ) is drawn from a strip supply and gradually shaped into a slit tube in a shaping station ( 2 ). The slit tube is welded in a welding system ( 4 ) along the edges of the strip, and the welded tube ( 6 ) is extracted by an extraction device ( 5 ). The welding system ( 4 ) is a protective gas arc welding system with several electrodes supplied by separate sources ( 4 c , 4 d) of welding current. The electrodes are arranged in succession, in the direction of production. The welding system ( 4 ) has two welding devices (4a, 4b), whose electrode tips are directed at a common welding point. Only one of the welding devices ( 4 a , 4 b) is in operation at any given time, while the other welding device is in a standby position. When an electrode change becomes necessary, the arc of the welding device in the standby position is first struck by means of an auxiliary arc. The 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.
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