Laser Beam Welding of Overlapped Joints Copper - Stainless Steel

The paper deals with the production of overlapped welded joints in a continuous and pulsed laser welding process with different welding parameters in order to examine the influence of changing parameters such as: power, focus, speed and length of the welding pulse. Laser welding achieves a high energy density, so there are no special requirements for the cleanliness of the welding surface because all impurities are evaporated before the material is melted. The overlap joint is mainly used for joining thin sheets and pipes. The aim was to find suitable parameters of the proposed technology for welding overlapped joints created of austenitic steel AISI 304 and copper Cu - ETP. In the experimental part, the created overlapped joint with power of 2000 W, welding speed of 15 mm/s and beam focus of 0 mm, where the total power input was 133.33 J/mm met the required criteria based on macro and microanalysis. The weld was realised by continuous welding. Satisfactory welding parameters were used for test specimens, to perform tensile and shear tests. During the tensile strength test, the failure occurred in the heat-affected zone (TOO) of copper due to the softening of the copper by grain coarsening. The strength reached values from 230-240 MPa. The calculated shear strengths were ranged from 409 to 411 MPa. The strength value depends on the degree of mixing of the materials in the weld. Based on the results of the shear test, the proportion of copper and steel in the mixing area proved to be a significant factor in the strength of the welded joint.