Investigation of mechanical properties of electric spot resistance welded DP 980 steel sheets and stainless steel sheets

In this study, the effects of welding current and welding time on the spot resistance weldability of DP 980 steel, which is rapidly increasing in use in the automotive sector due to its superior mechanical properties, and stainless 304 grade steel, which is readily available in the market, were investigated. The welding process was carried out at constant electrode pressure of 0.5 N/mm2 at welding currents of 7 kA, 9 kA and 11 kA and welding times of 10-15-20-25 cycles (1 cycle=0.02 s). Copper tipped spherical electrode with a diameter of 16 mm was used as electrode. For this purpose, tensile-shear tests were applied to the specimens. The maximum value of tensile-compression strength was reached at 25 cycles welding time and 11 kA current strength. After welding, weld diameter and penetration depth measurements were analysed. The maximum weld diameter value and electrode penetration depth were obtained at 25 cycle welding time and 11 kA current strength. The importance of welding current and welding time were determined and their effect on the tensile-shear stress was shown. The effects of welding current and welding time on weld diameter and penetration depth are also shown. At the same time, the micro hardness of the weld specimens were analysed. In addition, the microstructures of the specimens at critical tensile-compression stress values were also analysed.