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.
  • Publication
    A study on shielded metal arc welding of 9%Ni steel using non-conventional ferritic welding electrode for LNG facilities
    ( 2018)
    Siayah, A.
    ;
    El-Batahgy, A-M.
    ;
    Khafagi, S.
    ;
    Gumenyuk, A.
    ;
    Gook, S.
    ;
    Rethmeier, M.
    The present research work aims at clarification of the effect of the welding electrode type on the mechanical properties of SMA welded joints of 9%Ni steel plates. Properties of produced SMA welded joints were evaluated using different non-destructive and destructive investigation methods. In comparison with the conventionally used Ni-based welding electrode ENiCrMo-3 (AWS A5.11), an experimentally produced non-conventional ferritic welding electrode with 11%Ni (ENi11-Company specification) has resulted in a better combination of the mechanical properties of SMA welded joints of this steel type for critical cryogenic applications. Besides, a positive economic impact for the experimentally produced non-conventional ferritic welding electrode, due to its lower cost, could be another attractive aspect.
  • Publication
    Effect of laser-beam and hybrid-laser-arc welding parameters and filler metal on microstructure and mechanical properties of thick heat-treated steel X8Ni9+QT640 for cryogenic service
    ( 2018)
    El-Batahgy, A-M.
    ;
    Gook, S.
    ;
    Gumenyuk, A.
    ;
    Rethmeier, M.
    The present research work encloses results of experimental investigations of the interaction between welding process parameters for laser-beam and hybrid-laser-arc as well as type of the filler metal and the achievable mechanical properties of the weld joints on steel grade X8Ni9+QT640 for cryogenic service containing 9% nickel. The results obtained contribute to the development and conversion in the industrial practice a new laser beam-based welding technology for the automated manufacturing of facilities for the liquefaction, storage and the transport of natural gases (LNG facilities). The results show, that the martensitic microstructure of the laser weld metal including low amount of retained austenite not exceeding 3.5% leads to the relatively low V-notch impact energy. The remarkable heterogeneity in the chemical composition of the weld metal through the weld thickness could be recognized in the case of hybrid-laser-arc welding with ERNiCrMo-3 austenitic filler metal, what also led to insufficient impact toughness of the weld metall. The most promising results could be achieved by using 11%Ni filler wire, which is similar to the base metal and provides a homogeneous microstructure with uniform distribution of Ni through the weld seam. It is remarkable, that a correlation between Charpy impact toughness and wire feeding speed and respectively process heat input exists. The highest toughness values were 134±58 J at -196 °C. The both laser as well as laser-hybrid welds passed the tensile test. The failure stress of 720±3 MPa with a fracture location in the base material was achieved for all samples tested.
  • 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
    Hybrid laser Arc Welding for The Production of Longitudinally Welded Pipes
    ( 2014)
    Gook, S.
    ;
    Gumenyuk, A.
    ;
    Rethmeier, M.
    The aim of the present work is to investigate the possibilities of the hybrid laser arc welding regarding the reliable and cost effective production of longitudinal welds on the high strength pipeline steels X80 and X120 and to evaluate the achievable mechanical properties of the laser hybrid welds. The study focused on the investigations of the weld seam toughness in the low temperature range (-60 °C and -40 °C). Suitable filler materials have been identified in the context of this task. It could be shown that the metal powder filler wires, micro alloyed with Ni and partly with Cr and Mo, guaranteed sufficient Charpy impact toughness at low temperature for the both investigated materials (average value 190 J for X80 at -60 °C and 53 J for X120 at -40 °C). The modern arc technologies such as modified pulsed spray arc have been used to promote the deeper penetration of the filler material in the narrow laser weld. The edge preparation with a root face of 14 mm has been proposed as optimum, because no penetration of the filler material could be detected over this depth limit and therefor any metallurgical influences on the properties of the weld metal through the welding wire are not possible.