Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Laser welding of Inconel 718 nickel-based alloy layer-by-layer products
    ( 2020)
    Voropaev, Alexander
    ;
    Stramko, Maxim
    ;
    Sorokin, Alexander
    ;
    Logachev, Ivan
    ;
    Kuznetsov, Mikhail
    ;
    Gook, Sergej
    This article describes the results of the study of optimal conditions for welding alloy products - Inconel 718, made with the method of layered laser growing (SLM). The results of the study of the influence of linear energy, rigid fixation of parts during welding and heat treatment on microhardness, welding deformation and the microstructure of the welded joint are presented.
  • 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.
  • 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
    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
    Laser and hybrid laser-arc welding of cryogenic 9%Ni steel for construction of LNG storage tanks
    ( 2015)
    Gook, Sergej
    ;
    Forquer, Matthew
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    ;
    El-Batahgy, Abdel-Monem
    Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size Liquefied Natural Gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes including shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW) and submerged arc welding (SAW) are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies are a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller weld zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding (HLAW) conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using Electron Probe Microanalysis (EPMA).