TY - JOUR A1 - Gook, Sergej A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Method for defect-free hybrid laser-arc welding of closed circumferential welds T2 - Welding and Cutting N2 - This paper presents investigation results of a process for defect-free hybrid laser arc welding (HLAW) of closed circumferential welds. The process aims to avoid weld imperfections in the overlap area of a HLAW circumferential weld. A process control strategy for closing the circumferential weld was developed to achieve a defect-free overlap region by controlling the solidification conditions at the end of the weld. The controlled heat flow is achieved by adjusting the parameters of both welding processes involved, the laser beam as well as gas metal arc welding (GMAW) process. Experimental investigations were carried out on 12 mm to 15 mm thick tube sections. The influence of process parameters such as the laser ramp time, the change in magnification scale and the defocusing of the laser beam on the solidifi-cation conditions at the end of the circumferential weld was investigated to find an optimum strategy for ramping out the process energy. Within the framework of the experimental studies, it was demonstrated that defocusing the laser beam in the range between 60 mm and 100 mm over a short run-out area of the weld of approximately 15 mm led to a significantly better weld formation in the overlap area. A favourable cup-shaped weld shape could be achieved without a tendency to crack. The laser optics with a motor-driven lens system made it possible to increase the laser beam diameter without changing the position of the GMAW arc relative to the component surface. PB - DVS Media KW - Weld defects KW - Hybrid welding KW - Laser beam welding KW - Pipe manufacturing KW - Gas shielded arc welding PY - 2021 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/54665 AN - OPUS4-54665 VL - 20 IS - 4 SP - 334 EP - 339 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany