Effect of the time intervals on the mechanical and metallurgical quality of AA-2219 resistance spot weld joints

The final quality of the consecutive resistance spot weld (RSW) joints depends on the parameters including the welding time, welding distance, etc. Welding interval defined as the off time between the welding process of the two adjacent weld spots influences the quality of the next joint due to the contributions of the heating and pre-heating processes caused by the current local temperature distribution of the sheet and electrodes. In this paper, the influence of the timing interval between the two weld spots has been analyzed on the AA-2219 RSW joints, while the metallurgical and mechanical behavior of the final joint are analyzed experimentally and numerically. Temperature history and distribution of the final spot has been obtained using the finite-element analysis results, while microstructure and tensile-shear strength of the final spot weld have been evaluated experimentally. Timing interval has been set as the main variable for two consecutive nuggets with 5 mm welding distance, with the value of 0.5, 1, and 1.5 s. The results demonstrated that the longer interval has led to slightly faster cooling rates, less tensile-shear strength (0.6%), more asymmetric HAZ spread (15%) due to shunting intensification, and slightly smaller nuggets (about 2.5%), while the shorter interval had the reverse effects together with minor pre-heating.