Effect of use of filler wire on requirements of laser welded butt joints

Abstract

The number of industrial applications of laser welding is growing steadily, due to the advantages provided over conventional welding processes. However, the manufacture of a sufficiently narrow and uniform air gap in the joint is a severe problem which must be overcome for industrialisation of the process. This study discusses the benefits provided by the use of filler wire in laser welding of a butt joint in plain carbon steel. Welding with a wire requires an increase in heat input, which is a function of air gap width, due to the larger melt volume produced. Feeding tolerances for the filler wire are less than 0.5 mm. When welding with the maximum laser power available, sustaining the highest production rate, the welding speed must be decreased and the wire feed rate increased when the air gap is increased. This decreasing trend is similar at all power levels and material thicknesses. The use of filler wire laser welding allows an air gap between the plates to be tolerated, in best cases up to 1.6 mm for a 3 mm plate thickness, and 2.5 mm for 8 mm thick plate. The limits of mismatch are determined by standards and not by the welding process. Filler wire laser welding allows the joint edge to be manufactured by machining, laser cutting and mechanical shearing. Welding of shear cut edges creates welds with some undercut due to joint manufacture, but the quality is still acceptable according to standard proposals. In practice filler wire addition increases the tolerances of a butt joint by about 10 times in comparison with autogenous laser welding.The number of industrial applications of laser welding is growing steadily, due to the advantages provided over conventional welding processes. However, the manufacture of a sufficiently narrow and uniform air gap in the joint is a severe problem which must be overcome for industrialisation of the process. This study discusses the benefits provided by the use of filler wire in laser welding of a butt joint in plain carbon steel. Welding with a wire requires an increase in heat input, which is a function of air gap width, due to the larger melt volume produced. Feeding tolerances for the filler wire are less than 0.5 mm. When welding with the maximum laser power available, sustaining the highest production rate, the welding speed must be decreased and the wire feed rate increased when the air gap is increased. This decreasing trend is similar at all power levels and material thicknesses. The use of filler wire laser welding allows an air gap between the plates to be tolerated, in best cases up to 1.6 mm fo...