Sammendrag
For many years, laser hybrid welding has been used in various industries to increase productivity and reduce costs. One example is the adaption of the hybrid process in shipbuilding. The next natural step is to further develop the process for the oil and gas industry, where the welded joint properties requirements are more severe, and the ability to handle tolerance deviations is more critical. As a first attempt to develop hybrid laser process for the use in offshore structures, the present investigation addresses preliminary welding trails carried out with 15 kW fibre laser with appropriate gas metal arc welding equipment, using double Y joint geometry and 20 mm thick 420 MPa steel plates. The subsequent weld testing included both Charpy V notch impact and CTOD fracture mechanical testing at -30°C. The results indicate that the heat affected zone (HAZ) of the examined steel appeared with satisfactory Charpy and CTOD toughness (> 200 J, > 0.2 mm) while the weld metal had insufficient toughness (20-40 J, < 0.2 mm). With a better welding wire, designed for low temperature applications, it is reasonable to suggest that laser hybrid arc welding can be used for applications even below a temperature of -30°C.