Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • 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.
  • Publication
    Comparison between GTA and laser beam welding of 9% Ni steel for critical cryogenic applications
    ( 2018)
    El-Batahgy, A-M.
    ;
    Gumenyuk, A.
    ;
    Gook, S.
    ;
    Rethmeier, M.
    In comparison with GTA welded joints, higher tensile strength comparable to that of the base metal was obtained for laser beam welded joints due to fine martensitic microstructure. Impact fracture toughness values with much lower mismatching were obtained for laser beam welded joints due to similarity in the microstructures of its weld metal and HAZ. In this case, the lower impact fracture toughness obtained (1.37 J/mm2) was much higher than that of the GTA welded joints (0.78 J/mm2), which was very close to the specified minimum value (>0.75 J/mm2). In contrast to other research works, the overall tensile and impact properties are influenced not only by the fusion zone microstructure but also by the size of its hardened area as well as the degree of its mechanical mismatching, as a function of the welding process. A better combination of tensile strength and impact toughness of the concerned steel welded joints is assured by autogenous laser beam welding process.