RESEARCH PAPER Hybrid laser-arc welding of thick-walled ferromagnetic steels with electromagnetic weld pool support Ömer Üstündağ 1 & André Fritzsche 2 & Vjaceslav Avilov 3 & Andrey Gumenyuk 1,2 & Michael Rethmeier 1,2 Received: 16 March 2018 /Accepted: 26 April 2018 # International Institute of Welding 2018 Abstract The hybrid laser-arc welding (HLAW) process provides many advantages over laser welding and arc welding alone, such as high welding speed, gap bridgeability, and deep penetration. The developments in hybrid laser-arc welding technology using modern high-power lasers allow single-pass welding of thick materials. This technology can be used for the heavy metal industries such as shipbuilding, power plant fabrication, and line-pipe manufacturing. The obvious problem for single-pass welding is the growth of the hydrostatic pressure with increasing thickness of materials leading to drop-out of molten metal. This phenomenon is aggravated at slow welding velocities because of increasing weld seam width followed by a decrease of Laplace pressure compensating the hydrostatic pressure. Therefore, weld pool support is necessary by welding of thick materials with slow welding velocities. The innovative electromagnetic weld pool support system is contactless and has been used successfully for laser beam welding of aluminum alloys and austenitic and ferromagnetic steels. The support system is based on generating Lorentz forces within the weld pool. These are produced by an oscillating magnetic field orientated perpendicular to the welding direction. The electromagnetic weld pool support facilitates a decrease in the welding speed without a sagging and drop-out of the melt thus eliminating the limitations of weldable material thickness. Keywords Hybrid laser-arcwelding . Thick-walledsteel . Electromagnetic weldpoolsupport . Ferromagnetic steels . High-power laser beam 1 Introduction Laser hybrid welding combines laser beam welding and arc welding in the same weld pool. This concept was presented in the 1970s as arc augmented laser welding [1]. The high- energy density of the laser beam can be used for the deep penetration while the energy from the arc welding process could be used to melt the filler metal which is supplied in liquid form to the process. Another advantage of the hybrid process is a greater tolerance to joint gaps than autogenous laser beam welding [2]. In general, hybrid laser-arc welding technology produces welds with low distortions and high re- producibility and efficiency and eliminates defects due to ad- dition of filler metal. To justify a stable HLAW process, many parameters apart of the conventional welding parameters typ- ical for laser and arc welding processes must be adjusted. The principal factors, which have an influence on the quality of the welds are distance between GMAW torch and laser beam a, torch angle β, laser focus position Δz f , and process orientation with respect to the welding direction. A schematic represen- tation of hybrid laser-arc welding and influence factors are shown in Fig. 1. Recommended for publication by Commission IV - Power Beam Processes * Ömer Üstündağ oemer.uestuendag@ipk.fraunhofer.de 1 Fraunhofer Institute for Production Systems and Design Technology, Pascalstraße 8-9, 10587 Berlin, Germany 2 Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany 3 Otto von Guericke University Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany Welding in the World https://doi.org/10.1007/s40194-018-0597-3