Submerged-arc welding (SAW)
During the second process step, the shaped and continuously tack-welded pipes are transferred to one of the three down-stream computer-controlled internal and external SAW stands. There the submerged-arc spiral weld is completed first internally and then externally using a multi-wire technique.
A laser-controlled weld tracking system ensures that both the internal and external weld are correctly positioned with sufficient overlap. The tack weld produced during pipe forming serves as a backing to the weld and is fully remelted into it.