Resistance spot welding of ultra high strength steel sheets with aluminum materials

This thesis aims to examine the joining of steel sheets with a yield strength of up to 1500MPa and aluminum materials by using resistance spot welding (RSW). Effect of electrode geometry and its combinations on the quality of the joint is investigated. Materials used are steel MS1500 and aluminum EN AW-6061-T6. Samples were produced, and iterations were observed on these samples to achieve the optimum combination in terms of mechanical strength by changing parameters such as current, time, and electrode type. The study was carried out on a scale between 11-14kA as current. The force was kept constant in all samples by taking 3kN. Welding times of 10 and 20 cycles were tested. Microstructure analysis, macrostructure analysis, and tensile-shear testing methods were applied to observe the results and achieve the goal of maximizing mechanical strength.. The macrostructure analysis examined the nugget diameter, melted zone geometry, joint geometry, and fracture type. Failure types were determined due to the tensile-shear test. Vickers hardness test was applied to specify the hardness of the joint.