Jan Karlsson

The effect of fit-up geometry on melt flow and weld quality in laser hybrid welding

Hybrid laser-arc welding has a good tolerance to poor fit up as compared to simple laser welding. For a butt joint, the joint fit-up variations can be reduced to two local properties: the gap width and the vertical edge mismatch. The impact of these two properties on the resulting weld quality has been studied systematically in this paper. The original edges as well as the resulting weld surface topography have been scanned in three dimensions in order to study trends. During hybrid welding, the melt flow and the electric arc were observed at the top surface by high speed imaging to analyze the complex fluid flow phenomena.

Fibre laser welding for lightweight design

Two different high strength steel grades have been welded by a fibre laser to create a fillet corner joint. The purpose of this experiment is to use thinner materials of higher strength as a weight reduction strategy. The sensitivity of the welding process to the beam inclination angle, the beam position and the focal plane position were studied. High-speed imaging, process emission monitoring, measurement of the weld surface topography, mechanical testing and FE-analysis have been used to analyse the process and the resulting weld. A combined study by these methods gives a more comprehensive picture for studying the weld quality. A Bifurcation Flow Chart (BFC) has been applied as a new method to standardise and generalise the findings.Two different high strength steel grades have been welded by a fibre laser to create a fillet corner joint. The purpose of this experiment is to use thinner materials of higher strength as a weight reduction strategy. The sensitivity of the welding process to the beam inclination angle, the beam position and the focal plane position were studied. High-speed imaging, process emission monitoring, measurement of the weld surface topography, mechanical testing and FE-analysis have been used to analyse the process and the resulting weld. A combined study by these methods gives a more comprehensive picture for studying the weld quality. A Bifurcation Flow Chart (BFC) has been applied as a new method to standardise and generalise the findings.

Comprehensive monitoring and control of laser hybrid arc welding in industrial production

Welding requires acceptable quality along the entire weld. In particular, the weld surface geometry has a vital role in ensuring an adequate fatigue life. This paper describes the results of a case study of laser hybrid arc welding of a structural vehicle component of complex geometry. By isolating the various weld geometries along with systematic experimental studies by using a scanner and high speed imaging, the whole chain of the welding process can be analyzed and controlled. The component is made of two types of 7 mm and 20 mm thick high strength steel, requiring butt joints and T-joints, with 7 mm penetration. Cold Metal Transfer is compared to the more common spray mode of the arc, as it offers reduced spatter, undercuts and distortion. The study demonstrates the suitability of this new systematic procedure for controlling the whole welding process under industrial production conditions.Welding requires acceptable quality along the entire weld. In particular, the weld surface geometry has a vital role in ensuring an adequate fatigue life. This paper describes the results of a case study of laser hybrid arc welding of a structural vehicle component of complex geometry. By isolating the various weld geometries along with systematic experimental studies by using a scanner and high speed imaging, the whole chain of the welding process can be analyzed and controlled. The component is made of two types of 7 mm and 20 mm thick high strength steel, requiring butt joints and T-joints, with 7 mm penetration. Cold Metal Transfer is compared to the more common spray mode of the arc, as it offers reduced spatter, undercuts and distortion. The study demonstrates the suitability of this new systematic procedure for controlling the whole welding process under industrial production conditions.