AUTOGENOUS LASER WELDING OF ETP COPPER USING FIBER LASER

Abstract

To overcome the problems associated with the high thermal conductivity and high reflectivity to laser welding of ETP copper, a fiber laser is used as an efficient tool, which helps to minimize the heat affected zone and deformation, facilitates and improves the manufacturing process and reduces the production costs. However, it is important to control the formation process of the weld seam to get the required joint design. For this reason it is necessary to get an extensive knowledge of the correlation between the laser parameters and the geometrical dimensions of the weld seam, which was the goal of this investigation. In this work, laser welding of ETP copper has been performed with a 2 kW fiber laser to a depth of at least 2 mm. The butt joint specimens have been examined regarding the influence of beam misalignment, welding speed, focal position, beam angle etc. on the joint geometry. It has been shown, that higher line energies make the weld seam wider and deeper: The direction of the laser beam influenced also the geometry of the weld seam visibly. The change from a thrusting to a dragging laser beam led to a deeper penetration as well as the change from a vertically to a horizontally guided beam. A small gap between the specimens facilitated the energy input and lead also to a deeper weld. One focal point of the investigations was the classification of the different top geometries. Six typical top geometry classes have been figured out and reasons for their formation were found. Thereby, high energy densities on the surface caused spatters and the formation of an undercut. A reduction of the energy density instead or a focal position under the surface of the work piece produced a reinforcement.