Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Influence of heat input and preheating on the cooling rate, microstructure and mechanical properties at the hybrid laser-arc welding of API 5L X80 steel
    ( 2018)
    Turichin, G.
    ;
    Kuznetsov, M.
    ;
    Pozdnyakov, A.
    ;
    Gook, S.
    ;
    Gumenyuk, A.
    ;
    Rethmeier, M.
    This study investigates the influence of hybrid laser-arc welding parameters: heat input and preheating on the cooling rates, microstructure and mechanical properties of the welding joint. Samples from API 5L X80 steel with root thickness 14 mm were welded using welding wire MF 940 M. Decreasing cooling rate of welds from 588 °C/sec up to 152 °C/sec, weld metal hardness from 343±12 HV up to 276±6 HV and ultimate tensile strength from 1019.5±14 MPa up to 828±10 MPa and increasing bainite phase term of the weld metal was detected at the increasing preheating temperature up to 180 °C and maximal heat input. The mathematical relations of the input and output parameters were created using linear regression equations. Preheating temperature 180 °C allows increasing maximal welding speed up to more than 3.0 m/min with acceptable welding joint quality.
  • 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.