Influence of wire addition direction in C0 2 laser welding of aluminum

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Laser beam welding of aluminum alloys is expected to offer both the technical and economical advantages. In most cases welding wire addition is necessary from the viewpoints to suppress hot cracks, improve mechanical properties of the weld as well as to reduce demands on the edge preparation, fit-up tolerance, and beam alignment. In practice, the filler wire could be added to the weld pool either in the leading or trailing direction. In this experimental work reported, the influence of the wire addition direction on the weld efficiency and process stability was investigated by using a 5kW CO2 laser to weld aluminum alloy 6009 with a plate thickness of 3mm. Beam-on-plate welds were made either in the autogeneous mode or with filler wire AISi12. Illuminated by a double frequency Nd:YAG laser, the weld pool dynamics and the wire melting process were observed applying a high speed camera. The experimental results demonstrate that welding with filler wire in the trailing direction is more efficient and stable than in the leading direction. High speed camera photographs show that the filler wire is mainly melted through weld pool heating and plasma heating in the former case and through direct laser irradiation and plasma heating in the later case. The weld pool is of vibration when welding in the autogeneous mode or with filler wire in the leading direction. However, the weld pool is much calmer when the wire is added in the trailing direction to the weld pool.