Effect of hold time on resistance spot weldability of aluminium to steel

The effects of welding hold time on weld quality of aluminium alloy to dual-phase steel resistance spot welds were studied. Results demonstrated that there existed an optimum range of hold time (350 similar to 500 ms), within which the largest weld nugget diameter (7.6 mm), thinnest intermetallic compound (IMC) layer (1 similar to 5 mu m) and maximum tensile shear peak load (4.7 kN) were obtained. Too short hold time led to shrinkage, small weld nugget and thick IMC layer due to reduced heat dissipation after removing electrodes, thus resulting in low tensile peak load and brittle fracture along the IMC layer. While too long hold time, i.e. 750 ms, produced a smaller weld nugget diameter due to more rapid heat dissipation.