Hybrid laser/GMA welding of pipe joints

In order to improve the economic viability in pipeline construction, emphasis is placed on raising the productivity of the welding processes. The hybrid laser beam / GMA welding process constitutes a high potential here. In this respect, the technological approach is to use the deep welding effect typical of the laser for the manufacture of a high-quality free root pass. At SLV Halle GmbH, investigations relating to both appliance engineering and technology were conducted on this complex of subjects. Two different fibre laser systems with 4.5 kW and 10 kW were utilised as the laser beam sources. In order to produce a closed weld profile, the welding head was extended by an additional arc torch. Thus, it was possible to carry out not only the hybrid welding of the root but also the MAG welding of the cover pass in one revolution. Therefore, the complete fusion cross section of a pipe joining welding could be manufactured using two vertical-down welds. In the course of this test execution, important information was obtained about existing shortcomings of guiding systems which were not especially adapted to the hybrid welding process.

The specialised prototype which was put into effect on this basis, was available for advanced investigations and served to implement an orbital welding movement for hybrid laser beam / GMA welding had the following technical data: 

• Travel speeds: positioning - up to 6 m/min, welding - up to 3 m/min
• Processable pipe diameters: 500   700 mm
• Position-dependent alteration of the welding parameters
• Weld tracking and guiding

The presented work was supported by projects of the Federal Ministry of Economic Affairs and Technology. We would like to record our express thanks for this support.