Safe laser hybrid welding of structural steel by robust systems (HYBRO) : final report

The project addressed the widening of the robustness of laser hybrid arc welding, LAHW, with fibre or disc lasers, for steel structures. The study particularly focused on applicability for two large scale demonstrators, namely an excavator part and a truck component. This involved challenging joint edge variations as well as load conditions for fatigue and toughness. Fifteen truck beams were welded and success of the six fatigue tested beams has qualified them for a company internal business case evaluation. Two excavator booms were hybrid welded, compared to one arc-welded boom, which enabled the identification of challenges in joint fit-up and robustness for large parts. Additionally, wider mapping of the process capabilities was carried out, including its limiting welded joint imperfections and the mechanisms behind them. Apart from modelling and testing, methods like scanning the fit-up and the weld topology as well as high speed imaging of the process supported the robustness analysis. This resulted in a systematic quality tracking procedure. The 1040 experimental welding results and condensed process guidelines are stored in the HYBRO e-Archive, accompanied by publications. Six new hybrid welding technique options were studied, by certain arc and laser beam shaping in space and time. Three of those promising techniques, namely remelting of undercuts, LAHW twin arc and double-sided LAHW already meet quality criteria in ISO 12932:2013 and are ready to be implemented. The findings are very promising to enable more robust hybrid welding of structural steel applications with fibre or disc lasers.