Effect of Zinc Aluminum Magnesium Coating on Spot-Welding Joint Properties of HC340LAD+ZM Steel

Zn-Al-Mg (zinc, aluminum and magnesium)-coated steel is gradually replacing traditional hot-dip galvanized steel due to its excellent corrosion resistance, self-healing properties and good surface hardness. However, the effect of Zn-Al-Mg coating on the resistance spot-welding joint properties of HC340LAD + ZM steel plates is not clear, and there are few systematic studies on it. In this paper, L16 (4(3)) orthogonal experiments were designed on Zn-Al-Mg-coated steel HC340LAD + ZM (thickness = 1 mm). In addition, taking the tensile shear force as the main evaluation standard, the optimal spot-welding process properties could be achieved when the welding current, the welding time and the electrode loading were 10 kA, 14 cycles and 2.6 kN, respectively. On this basis, the formation mechanism, microstructure and corrosion properties of two plates of steels, with or without zinc, aluminum and magnesium coating under different welding times, were studied. The presence of Zn-Al-Mg coating slightly affected the mechanical properties of welding joints. However, the corrosion current of the body material containing Zn-Al-Mg plating was 7.17 times that of the uncoated plate.