TY - JOUR A1 - Üstündag, Ömer A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled pipe segments with optimization of the end crater T2 - Procedia CIRP N2 - The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2Gpositions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc. PB - Elsevier B.V. KW - Hybrid laser-arc welding KW - Circumferential weld KW - Thick-walled steel KW - Single-pass welding KW - End crater PY - 2020 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/51326 AN - OPUS4-51326 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513260 VL - 94 SP - 676 EP - 679 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany