Pdf2

16BME0279

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Aritra Guha Ray

The process can be used to produce welds that meet the hardness requirements. This observation was also valid for the situation in which the root weld of a partially grooved V joint was made using a Nd: YAG-laser, and the upper part of the joint was filled later using GMAW. By using this procedure, test pieces up to 11 mm thick could be welded, in comparison with the 6 mm maximum limit of former processes. When considering welding speed and penetration, it was observed that the addition of the laser beam to the GMAW arc did not increase the penetration or welding speed although it has been reported in other studies. One reason for this is the incidence angle of the laser beam used, 50°. The angle should be perpendicular to the welding direction in order to increase the penetration and welding speed. The distortion, which was measured from the test pieces, was smaller than that produced by GMAW alone in material of similar thickness. The main reasons lay in the use of the I groove for the tests and the nature of the process. It was clearly seen that by combining GMAW and the laser beam, the groove tolerances decreased significantly, although maximum allowable air gaps were not studied. Despite the fact that guillotine shear cut was used in groove manufacture, only a few pores were found in the cross sections.

Fig4. Transverse sections of a GMA-weld and a laser-GMA-hybrid weld sheet thickness: 8 mm laser type: Nd:YAG laser power: ~ 4 kW welding speed: 2 m/min shielding gas: 82% Ar / 18% CO2

3. Applications: The first industrial application of the laser-GMA-hybrid welding process in a shipyard was realized with a CO2-laser. At the German shipyard “Kvaerner Warnow Werft” in Rostock (Fig. 5) a common welding gantry has been refitted with equipment for the Nd: YAG-laser-GMA-hybrid welding. During the above-mentioned regional research project, the problems regarding with such a refitting should are solved. The refitting was done after measuring the dynamical behaviour at the point, were the future hybrid working head shall be located. The results correlated well with the requirements regarding to. The first test welds made with the refitted conventional welding gantry also verified the suitability of the gantry for use with laser technique.