Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Improvement of filler wire dilution using external oscillating magnetic field at full penetration hybrid laser-arc welding of thick materials
    ( 2019)
    Üstündag, Ömer
    ;
    Avilov, Vjaceslav
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Hybrid laser-arc welding offers many advantages, such as deep penetration, good gap bridge-ability, and low distortion due to reduced heat input. The filler wire which is supplied to the process is used to influence the microstructure and mechanical properties of the weld seam. A typical problem in deep penetration high-power laser beam welding with filler wire and hybrid laser-arc welding is an insufficient mixing of filler material in the weld pool, leading to a non-uniform element distribution in the seam. In this study, oscillating magnetic fields were used to form a non-conservative component of the Lorentz force in the weld pool to improve the element distribution over the entire thickness of the material. Full penetration hybrid laser-arc welds were performed on 20-mm-thick S355J2 steel plates with a nickel-based wire for different arrangements of the oscillating magnetic field. The Energy-dispersive X-ray spectroscopy (EDS) data for the distribution of two tracing elements (Ni and Cr) were used to analyze the homogeneity of dilution of the filler wire. With a 30° turn of the magnetic field to the welding direction, a radical improvement in the filler material distribution was demonstrated. This would lead to an improvement of the mechanical properties with the use of a suitable filler wire.
  • Publication
    Full penetration hybrid laser arc welding of up to 28 mm thick S355 plates using electromagnetic weld pool support
    ( 2018)
    Üstündag, Ömer
    ;
    Avilov, Vjaceslav
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    The laser hybrid welding process offers many advantages regarding deep penetration, increased welding velocity and with the help of the supplied filler wire an improved bridgeability to gap and misalignment tolerances. High power laser systems with a power of approx. 30 kW are already available on the market. Nevertheless, multi-layer technology with an arc process is still used for welding of plates from a thickness from 20 mm. A potential cause is the process instability with increasing laser power. It is inevitable that gravity drop-out due to the high hydrostatic pressure at increasing wall thickness especially at welding in flat position and with a low welding speed. The surface tension decreases with increasing root width resulting from low welding velocities. To prevent such inadmissible defects of the seam a use of weld pool support is required. Usual weld pool support systems such as ceramic or powder supports require a mechanical detachment which is time-consuming. The electromagnetic weld pool support system described in this work shows an alternative weld pool support which works contactless. It is based on generating Lorentz forces in the weld pool due to oscillating magnetic field and induced eddy currents. This innovative technology offers single pass welds up to 28 mm in flat position and reduced welding velocity with a laser power of just 19 kW. It also leads to improved mechanical-technological properties of the seams because of the slow cooling rate. With usage of an electromagnetic weld pool support the limitation of the hybrid laser arc welding process in the thick sheet metal will be extend.
  • Publication
    Study of gap and misalignment tolerances at hybrid laser arc welding of thick-walled steel with electromagnetic weld pool support system
    ( 2018)
    Üstündag, Ömer
    ;
    Fritzsche, André
    ;
    Avilov, Vjaceslav
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    The hybrid laser arc welding (HLAW) process provides many advantages such as improved gap bridgeability, deep penetration and misalignment of edges, that is why the process is used increasingly in industrial applications e.g. shipbuilding, power plant industry and line-pipe manufacturing. The obvious encountered problem for single pass welding in flat position is the gravity drop-out at low welding velocities. With the usage of an electromagnetic weld pool support system, which is based on generating Lorentz forces within the weld pool, wide seams followed by reduced welding velocities could be achieved in this study leading to the realization of a gap bridgeability up to 1 mm, misalignment of edges up to 2 mm and a single pass weld up to 28 mm thickness with a 20-kW fibre laser. These developments expand the boundaries of the HLAW process for different industrial applications. As a result, less accurate preparation of the edges would be sufficient, which saves time for manufacturing.
  • Publication
    Hybrid laser arc welding of 25 mm thick materials using electromagnetic weld pool support
    ( 2018)
    Üstündag, Ömer
    ;
    Avilov, Vjaceslav
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    In addition to the many advantages of deep penetration, increased welding speed and a low sensitivity to manufacturing tolerances such as gap and edge offset, the hybrid laser arc welding process is used increasingly in industrial applications such as shipbuilding or pipeline manufacturing. Nonetheless, thick-walled sheets with a wall thickness of 20 mm or more are still multi-pass welded using the arc welding process, due to increased process instability by increasing laser power. Welding at reduced speed, especially in a flat position, leads to an irregular formation of the root part such as dropping. The hydrostatic pressure exceeds the surface tension, which decreases with increasing seam width. In order to prevent gravity drop-outs, the use of a melt pool support is necessary. Usual weld pool supports such as ceramic or powder supports require time-consuming mechanical detachment. The electromagnetic weld pool support system, which is described in this study, operates without contact and based on generating Lorentz forces in the weld pool. An externally applied oscillating magnetic field induces eddy currents and generates an upward directed Lorentz force, which counteracts the hydrostatic pressure. This allows single-pass welds up to 25 mm by hybrid laser arc welding process with a 20-kW fibre laser. Moreover, it is favoured by the diminished welding speed the cooling rate which leads to an improvement of the mechanical-technological properties of the seams - the lower formation of martensite in the microstructure enables better Charpy impact toughness. The electromagnetic weld pool support extends the limitation of the laser hybrid welding process in the thick sheet area. By adapting the electromagnetic weld pool support to the laser and laser hybrid welding process, the application potential of these technologies for industrial implementation can be drastically increased.