Abstract
The present work was done to evaluate laser hybrid welding, together with Vitec AS, for possible future production welding. All welding has been done at FORCE Technology in Denmark using a CO2 laser combined with MAG welding. The work has been focused on macro- and microstructure characterisation of the different welds received:1. Butt welding of 12 mm plate2. Butt welding of 16 mm plate3. Two-sided fillet welding of 12 mm stiffener to 16 mm plate4. One-sided fillet welding of 12 mm stiffener to 16 mm plateIt is evident from the impact testing that a wide scatter in toughness has been found, and that the weld metal impact properties may be very low. It is suggested that this scatter is linked to the solidification behaviour of the butt welds, i.e., a straight weld centreline which is the last area to solidify, where impurities are expected to segregate with potent low fracture toughness.Concerning the fusion line toughness, most welds had acceptable values. An exception was found for the plates 1 and 2. The welded 16 mm plate had the highest values, all close to 400 J. This is possibly caused by the fine ferrite with some fine upper bainite, which is in strong contrast to the weld metal microstructure in this plate (coarse upper bainite with low toughness).It is rationalised from the low toughness and large scatter observed that there is huge potential for improvements in hybrid laser welding of structural steels.
