Description

For applications on steel constructions such as bridge, crane or shipbuilding, MAG or submerged arc welding processes have been established for many years. Currently, the use of high-power beam sources is not state of the art in that important field of industry. The reasons are high demands on weld seam preparation, manufacturing tolerances, clamping technology for positioning sheet metal semi-finished products, but also high investment costs. Furthermore, basic requirements for the use of joining processes in steel construction are the reliable bridging of approx. 2 mm gaps and plasma-cut edges.  

However, positive features such as high process performance, flexibility and cost advantages, especially when using laser beam sources, are already known from the automotive applications. The potential of low-heat laser beam welding processes for steel constructions to increase production efficiency and improve component quality (minimal welding distortion) is in fact enormous.

The laser multi-pass welding (Laser-MPNG) developed at the Fraunhofer IWS using a 10 kW high power diode laser is a welding technology adapted to the changed boundary conditions of steel structures. Compared to the laser hybrid welding used in steel construction, the focus on only one energy source supports the approach to make laser beam welding attractive for steel construction applications by low investment costs.

Using the example of a 4-meter-long box structure typical for a steel construction, it is shown that the laser MPNG-welding can be used to efficiently join both T-joints and butt joints in the sheet thickness range of 15-30 mm. The process was designed for a high welding speed (1 to 1.5 m/min) and a reduced number of weld seam passes, thus contributing to a drastic reduction of welding time compared to conventional MAG welding. Furthermore, this new process allows a significantly reduced opening angle <15° of the weld seam preparation compared to the MAG process, which, among other things, leads to a drastic reduction of filler material. In addition, the distortion of the overall construction is minimized significantly.

In the development project which has been carried out together with industrial partners, it was shown that the four meter long box structure of an indoor crane can be successfully welded under practical conditions. Supporting, a mobile laser protection enclosure, sensor-supported seam tracking and an extraction system integrated in the welding head were used.

Contributing Authors

  • Dirk Dittrich
    Fraunhofer Institute for Material and Beam Technology
  • Robert Strohbach
    Fraunhofer Institute for Material and Beam Technology
  • Axel Jahn
    Fraunhofer Institute for Material and Beam Technology
  • Frieder Zimmermann
    Fraunhofer Institute for Material and Beam Technology
  • Christoph Leyens
    Fraunhofer Institute for Material and Beam Technology | Technical University of Dresden
Dirk Dittrich
Fraunhofer Institute for Material and Beam Technology
Track: Laser Materials Macroprocessing
Session: Welding I
Day of Week: Monday
Date/Time:
Location:

Keywords

  • High Power Diode Laser
  • Hybrid Welding
  • Mild Steel Thick Walled Structures
  • Multi-Pass Narrow Gap
  • Steel Structures Cran, Shipbuilding