Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Hybrid laser arc welding of thick high-strength pipeline steels of grade X120 with adapted heat input
    ( 2020)
    Üstündag, Ömer
    ;
    Gook, Sergej
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    The influence of heat input and welding speed on the microstructure and mechanical properties of single-pass hybrid laser arc welded 20 mm thick plates of high-strength pipeline steel X120 were presented. The heat input was varied in the range of 1.4 kJ mm-1 to 2.9 kJ mm-1, while the welding speed was changed between 0.5 m min-1 and 1.5 m min-1. A novel technique of bath support based on external oscillating electromagnetic field was used to compensate the hydrostatic pressure at low welding velocities. A major advantage of this technology is, that the welding speed and thus the cooling time t8/5 can be variated in a wide parameter window without issues regarding the weld root quality. The recommended welding thermal cycles for the pipeline steel X120 can be met by that way. All tested Charpy-V specimens meet the requirements of API 5 L regarding the impact energy. For higher heat inputs the average impact energy was 144 ± 37 J at a testing temperature of -40 °C. High heat input above 1.6 kJ mm-1 leads to softening in the weld metal and heat-affected-zone resulting in loss of strength. The minimum tensile strength of 915 MPa could be achieved at heat inputs between 1.4 kJ mm-1 and 1.6 kJ mm-1.
  • Publication
    Hybrid laser arc welding of thick plates X8Ni9 for LNG tank construction
    ( 2019)
    Gook, Sergej
    ;
    El-Batahgy, A-M.
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Results of experimental investigations of the relationship between laser-hybrid welding process parameters, type of the filler metal and the mechanical properties of the welds made from 9% nickel cryogenic steel X8Ni9 are discussed. The results contribute to the development and conversion in the industrial practice a new laser beam-based welding technology for the automated manufacturing of LNG tanks. The remarkable heterogeneity in the chemical composition of the weld metal as well as an insufficient impact toughness could be indicated by using austenitic filler wire. The most promising results were achieved by applying 11%Ni filler wire, which is similar to the base material. A correlation between impact toughness and wire feeding speed could be shown. The highest impact toughness was 134 J at -196C. The laser-hybrid welds passed the tensile test. The failure stress of 720 MPa with a fracture location in the base metal was achieved for all samples tested.