Nowadays tube to tube-sheet joints are usually welded by TTG orbital welding process. This process is characterized by very high quality of the weld beads and good repeatability. These aspects are very important for the manufacturing of steam generators used in PWR nuclear power plants, where thousands of welds are required in each component. Due to this high number of welds, a reduction in the time needed for each welding operation would have an interesting impact on manufacturing costs and delays.
The aim of this work is to study the application of laser welding in tube to tube-sheet joints. The main advantage of laser welding is to allow higher welding speed and lower heat input than arc processes. Furthermore, by using laser welding, it would be possible to make online process control in order to detect weld defects.
Trials were performed using two seam location systems: an optical seam tracker and a seam location based on computer vision. For the welding process, different optical path configurations were tested in order to achieve circular seams: a scanner welding head with galvanometric optics and a welding head with fixed optics. Welding configurations were adjusted and tested in order to obtain optimal welds. Characterization was made by metallographic observations and non destructive testing to detect metallurgical defects and eccentricity problems, assuring an optimal weld penetration.