Fatigue and impact properties of single and double resistance spot welding for high-strength steel used in automotive applications

The resistance spot welding for high-strength low-alloy steel (HSLA DOCOL 500 LA) is examined in this study. Many parameters affect the quality of resistance spot welding such as welding current, welding time and electrode force. It is very necessary to optimize these parameters to increase the quality of welding and to save time and cost. The optimization process was achieved using the Taguchi method for single and double spots. The Taguchi design method, which reduces the number of experiments by arranging the tests into an orthogonal array and choosing the most effective parameters, is one of the best methods for the optimization process. Mechanical, microhardness and microstructure tests were performed. The fatigue test for welded samples with optimum parameters was achieved and measured the crack length using high-accuracy cameras. The impact behaviour for welded samples was also carried out using a high-speed servo-hydraulic jack. The fatigue test showed that double spot welding has an endurance limit at a maximum load 1500 N, while for single spot, the endurance limit was 1000 N. Double spot welding design was more resistant to spot welding failure and this led to an increase in the safety of passengers during the crash situations.