The effect of current on the resistance spot welding of dual phase steels

The effect of current on resistance spot welding joints on metallurgic and mechanical properties is investigated experimentally using galvanized unequal-thickness DP600 steel sheets. The specimens were chosen to be 1.5 and 1.8 mm thicknesses. The parameters of the welding process were preferred as an electrode force at 5 kN, welding currents at 7, 9, 11, 13 and 15 kA and welding times at 180, 240, 300, 360 and 420 ms. The welded joint specimens were subject to tensile-shear strength testing to determine the ultimate tensile strength. Optimal specimens were inspected using optical microscopes and scanning electron microscopy. The effect of spot welding variables on the ultimate tensile strength was determined and the lobe diagram, which shows optimal current-time values, was obtained. The optimal welding parameters were carried out on new sheet metals successfully. The experimental results show that the welding current plays an important role in the especially crash energy absorption and load-carrying capability.