Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Shielded metal arc welding of 9%Ni steel using matching ferritic filler metal
    ( 2021)
    El-Batahgy, A.
    ;
    Saiyah, A.
    ;
    Khafagi, S.
    ;
    Gumenyuk, A.
    ;
    Gook, S.
    ;
    Rethmeier, M.
    Motivated by the tensile strength loss of 9%Ni steel arc welded joints made using Ni-based austenitic filler metals, the feasibility of maintaining the tensile strength using matching ferritic filler metal has been demonstrated. In comparison with shielded metal arc welded joint made using Ni-based austenitic electrode ENiCrMo-6, higher tensile strength comparable to that of the base metal was obtained using matching ferritic electrode. Besides, sufficient impact toughness energies with much lower mismatch were obtained for weld metal and heat-affected zone. Welded joint with a lower mechanical mismatching is of considerable importance for achieving acceptable combination of tensile strength and impact toughness. A better combination of these mechanical properties is ensured by applying a post weld heat treatment.
  • Publication
    Notch impact toughness of laser beam welded thick sheets of cryogenic nickel alloyed steel X8Ni9
    ( 2020)
    Gook, S.
    ;
    Krieger, S.
    ;
    Gumenyuk, A.
    ;
    El-Batahgy, A.M.
    ;
    Rethmeier, M.
    The paper deals with the investigations of the impact toughness of laser beam welded 14.5 mm thick sheets made of cryogenic steel X8Ni9 as a function of preheating. This 9% nickel alloyed steel is widely used in the liquefied natural gas (LNG) industry. An application of highly efficient welding processes such as high-power laser beam welding (LBW) in LNG sector requires an understanding of the interactions between the LBW process parameters and weld properties, in particular the impact toughness. The results show that the original fine-grained martensitic microstructure of the base metal (BM) is significantly changed by melting and crystallization during the LBW, what can lead to a decrease in the impact toughness of the weld metal (WM) below the required level. An optimal preheating temperature range leads to the favorable thermal welding cycle and is of remarkable importance for maintaining the notch impact toughness of laser beam welded joints of these thick steel sheets. A parameter window was identified in which V-notch impact toughness comparable to that of the BM at -196 °C was achieved.
  • 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.