To provide a method for forming a long welded tube from a metal band without interruption of the welding process.
A metal band is gradually formed into a slit tube in a forming apparatus 2, the edges of the band are welded in welding equipment for the slit tube, and the welded tube 6 is pulled out by a pulling-out apparatus 5. The welding equipment is a protective gas-arc welding equipment comprising a plurality of electrodes supplied with electricity from individual welding sources 4c, 4d. The electrodes comprise two welding equipment 4a, 4b arranged just before or after to the production direction, and the tips of the electrodes in the welding equipment are turned to a common welding point. Only one welding equipment is driven, and the other welding equipment lies in a waiting position against the same. In the case the exchange of the electrodes is required, at first, an arc in the welding equipment lying in a waiting position is ignited with an auxiliary arc. Thereafter, the intensity of welding current for the welding equipment under the driving is reduced, and simultaneously, the intensity of welding current for the welding equipment lying in a waiting position is increased.
HOFFMANN ERNST
BRUENN RAINER
