Experimental and Numerical Study of Resistance Spot Welding of Galvanized High-Strength Low-Alloy Steel Sheets

This work studies the optimal parameters of resistance spot welding high-strength steels based on the minimum size of the welding button, no expulsion of molten material and the adhesion of the electrode on the work sheet. Experimental studies were conducted on steel sheets which had a thickness of 1.8 mm and zinc coating of 12 μm. Processing parameters included current from 15 to 16.6 kA, welding time of 13 cycles and holding time of 5 and 30 cycles. The weld quality was evaluated through metallography in the welding zone as well as tensile shear tests and hardness profiles of the welding spots. A finite element model was additionally developed to determine the thermo-mechanical response of resistance spot welding. The optimal welding conditions for the zinc coated steels were located at lower currents (15-15.5 kA). The microhardness results of the weld spots revealed a maximum hardness of 380 HV and a maximum load of 20.23 kN for the welding specimens produced with a current of 15.5 kA. The numerical results of the nugget size and shape were compared with experimental tests at 15.5 kA and the obtained nugget diameters show a close agreement.