Product Code: ICAL08_1006

Study of Phenomenon of Fibre-Laser-Mig/Mag-Hybrid-Welding
Authors:
Heidi Piili, Lappeenranta University of Technology; Lappeenranta Finland
Antti Salminen, Lappeenranta University of Technology; Lappeenranta Finland
Petri Harkko, Cavitar Ltd; Tampere Finland
Janne Lehtinen, Cavitar Ltd; Tampere Finland
Presented at ICALEO 2008

The laser hybrid welding processes are widening the field of laser welding applications. They are gaining ever more interest in many sectors of metal industry. There is quite a few successful applications already in use for example in automotive, ship building and construction industry. The current development steps of high power fiber lasers has widened ever more the applicability of laser hybrid welding for thick section welding. Typically fiber hybrid welding is a combination of fiber laser welding and MIG/MAG welding process. The aim of this study was to study the process and phenomena of laser hybrid welding with fiber laser. The laser power used was 5 kW. The arc process used was MAG welding. Material used was mild steel S355 of thickness 6 mm and joint type was butt joint. Welding process is photographed with new type of photography arrangements. The photography system utilizes the use of active illumination with different view angels to the welding process. It seems obvious that the welding speed can be further increased in comparison to autogenous keyhole laser welding by using laser hybrid welding process. A small airgap in the butt joint makes it possible to use even higher welding speeds. The effect of geometrical welding parameters like process distance, focal point position and airgap have considerable effect on the welding process thus the quality produced. The clear limits for parameters giving acceptable weld quality can be defined. The new photographic system utilised gave good information about the process and material behaviour revealing new features of the process. The too wide an airgap in joint will cause need to increase heat input for melting the required volume. The speed must often be lowered also due to the capacity of arc source wire feeding capacity. The second limit for airgap width is the maximum bridgeable gap width. The new photographic system gives a lot further information about the keyhole and plasma formation and shape as function of other welding parameters. The combination of co-axial view and side view clarifies also the droplet movement and the effect of process distance to the process and mechanisms connected to formation of various weld flaws.