Experimental investigation on resistance spot welding of galvannealed HSLA steel

Abstract

A systematic variation of the parameters involved in the spot welding by electrical resistance of galvannealed strips was carried out on samples from a 2 mm thickness galvannealed high strength low alloy steel strip used for automotive applications. The varied parameters in the present study were welding current, welding time, holding time after welding and number of welding pulses, while the dimensions and characteristics of the electrodes and the applied force during welding were kept constant. The wear of the electrodes is important, however it was not the aim of the present study, therefore it was not taken into account. The experimental results were analysed to evaluate the influence of the various parameters on diverse characteristics of the welded bead. It was possible to determine the optimal operational conditions for this particular type of material.

Failure mode of HSLA/DQSK dissimilar steel resistance spot welds

“…Generally, the RSW failure occurs in two modes: interfacial and pullout. [6][7][8] Figure 1 shows a typical fracture mode during mechanical testing of a spot weld. In the interfacial mode, failure occurs via crack propagation through FZ, while in the pullout mode, failure occurs via the nugget withdrawal from one sheet.…”

Microstructural characterization and mechanical properties of spot welded dissimilar advanced high strength steels

“…Nietol et a!. [26] investigated various parameters that are used to control the characteristics and properties of galvannealed HSLA steel sheets welded by means of electrical resistance, for further applications at high production speeds. They found that increasing the hold time from 5 to 30 cycles results in stamps free of oxide as shown in Figure 2.8, but care has to be taken, as the amount of ferrite present within the welded nugget is reduced, and the micro hardness of the material increases with increasing the hold time.…”

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

“…When the electrode force was too high, the weld nugget diameter was small and the tensile shear load was low [4]. For the effect of hold time, Nieto et al [8] concluded that the microhardness of HSLA galvanised steel RSWs increased with the increase of hold time. Pouranvari et al [9] found that hold time had no significant effect on weld nugget diameter, tensile shear strength and fracture mode of low carbon steel RSWs.…”

“…The main optimisation methods include adjusting welding parameters (welding current, welding time, electrode force, etc.) [3-9], using a cover plate on the aluminium alloy sheet [10, 11] and using interlayers [12, 13]. For the influence of welding parameters on the quality of RSWs, research results have shown that increasing welding current or welding time leads to thicker IMC layers, larger weld nugget diameter and more molten aluminium alloy expulsion [3-7].…”