Study of phenomenon of fibre-laser-MIG/MAG-hybrid-welding

Abstract

The laser hybrid welding processes have quite a few successful applications already in use for example in automotive, ship building and construction industry. The current development steps of high power lasers using optical fiber for beam transportation are widened the applicability of laser hybrid welding ever more and also to thick section welding.The aim of this study was to study the process and phenomenon of laser hybrid welding with fiber laser. The laser power used was 5 kW. The arc process used was MIG/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.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 utilized gave good information about the process and material behavior revealing new features of the process.Too wide airgap in joint will cause need to increase heat input for melting to achieve required volume. The speed must often be decreased also due to wire feeding capacity of arc source. The second limit for airgap width is the maximum bridgeable gap width.The new photographic system gives further information about the keyhole, 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.The laser hybrid welding processes have quite a few successful applications already in use for example in automotive, ship building and construction industry. The current development steps of high power lasers using optical fiber for beam transportation are widened the applicability of laser hybrid welding ever more and also to thick section welding.The aim of this study was to study the process and phenomenon of laser hybrid welding with fiber laser. The laser power used was 5 kW. The arc process used was MIG/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.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 def...