The automotive industry is always trying to make the vehicles lighter. One of the solutions is to design them in a way, which requires the use of the materials that have good strength to weight ratio. With that comes the challenge of welding those materials. Therefore, we are commonly faced with riveting, resistance welding and other joining technologies regarding production. The most commonly used one is resistance spot welding, since it can be fully automatized, and we can monitor the energy consumption. Spot welding is much faster in comparison to riveting and therefore more cost efficient.
The bachelors thesis presents the basics of resistance spot welding and shows a special method of this type of welding. DP 500 steel sheets were welded with different parameters, which were then put on the tensile and shear test. From the test results and the parameters we could show how different welding parameters affect the tensile strength, shear force and ductility. The test samples were also visually inspected. The samples which were not ruptured from testing were then prepared for microscopic analysis. Through the analysis we could determine the grain size and direction, but also observe whether there are any cracks in the material. In the last test, hardness was measured with Vickers hardness test in the weld and the heat affected zone. It was found that at a welding current of 8 kA, a welding time of 200 ms, and a holding force of 2.45 kN, the maximum allowable welding parameters are obtained, since the shear strength of the weld exceeds the strength of the base material. In order to have a sufficiently high shear strength, at a force of 3.68 kN and a time of 300 ms, the welding current must exceed 9.2 kA.
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