Journal of Welding Science

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Farbakhti M, Elmi Hosseini S R, Mousavi Mohammadi S A. The effect of current intensity on liquid metal embrittlement in resistance spot welding of QP1180 steel. JWSTI 2025; 11 (1) :139-148
URL: http://jwsti.iut.ac.ir/article-1-499-en.html

This study investigated the influence of resistance spot welding current intensity on the formation of liquid metal embrittlement (LME) cracks in galvanized advanced QP1180 steel. Galvanized steel sheets with a thickness of 1 mm were welded at currents of 6.5, 7, 7.5, and 8 kA. The results revealed that increasing the current significantly enlarged the weld nugget size, molten volume, electrode indentation, and the likelihood of LME crack formation. Microstructural analysis, elemental distribution, and crack characterization were conducted using optical and electron microscopy. The findings indicated that the weld zone microstructure primarily consisted of martensite, while the non-uniform distribution of zinc along grain boundaries facilitated the initiation and propagation of LME cracks. Cracks were predominantly observed at the periphery of the weld pool indentation and in the electrode-sheet contact area. This study demonstrates that controlling welding current intensity is a key factor in mitigating LME and improving the mechanical properties of joints in galvanized QP1180 steel. Optimizing welding parameters, particularly limiting current intensity, can prevent molten metal-induced cracking and enhance the durability and safety of automotive structures. Hardness profiling revealed peak hardness in the weld zone, followed by a gradual decrease toward the heat-affected zone (HAZ).