Spot Weld Strength Modeling and Processing Maps for Hot-Stamping Steels

Abstract

This research focuses on developing a novel methodology for modeling the link between nugget size and strength, as well as resistance spot welding (RSW) parameters and expulsion, in commercial hot-stamping Usibor® 1500 and Ductibor® 500. The RSW process was simulated for more than 250 different sets of welding time, current, and electrode force, resulting in the creation of 3D processing maps for both materials. The predictions were evaluated by measurements, and 3D nonlinear regression methods were used to explain the variations in strength as the function of welding parameters. A substantial amount of effort was devoted to taking the effect of expulsion into the numerical models so that the shear-tension strength of the spot welds would be predictable based on the occurrence and extent of expulsion during RSW. The results indicated that the occurrence of expulsion may decrease the strength of the spot weld up to 10 kN (2248 lbf) in Usibor (45%) and leads to 4 kN (899 lbf) strength loss (23%) in Ductibor. The models can estimate the strength of the spot weld with ± 1 kN (224 lbf) error.

Shear band formation at the fusion boundary and failure behaviour of resistance spot welds in ultra-high-strength hot-stamped steel

“…Resistance spot welding was performed using a 144/180 kVA Medium-Frequency Direct Current (MFDC) machine with a pneumatic gun. The adopted welding procedures were optimised in a previous study [5]. Welds were made as single pulse welds using a 7 kA for 400 ms welding current and an electrode force of 3.5 kN.…”

“…Over the last several years, many studies have investigated how to optimise the resistance spot welding process for the latest generations of PHS [3, 4]. In previous work by the current authors [5], the destructive effect of uncontrolled expulsion on the mechanical properties of aluminium-silicon coated 22MnB5 welds was explained and numerically modelled. However, it is reported by Chen et al [6] that controlled expulsion helps in eliminating Al–Si coating around the notch which improves weld properties.…”

Effects of preheating and slow cooling stages in small-scale resistance spot welding of the Ti-2Al-1Mn alloy

“…In the RSW process, heat generation (and the quality of the joints as a result) can be stabilized only by strict control over both preparation of the welded parts and maintenance of deployed equipment. As some previous investigations have shown, current pro les should include the optimal main pulse (within a current-time weld lobe) [10,[12][13][14][15][18][19][20][21][22], as well as both preheating [3, 12-14, 16, 17, 23, 24] and post-weld [13,14,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] stages. In this case, the preheating one stabilizes initial RBE values and, respectively, heat generation in the weld zone according to Eq.…”

Spectroscopy Peculiarities of Electric Arc Discharge Plasma With Iron Vapours

“…In addition to the works mentioned, over the past couple of years, many more welding techniques [6][7][8], in the process of which the iron vapours take place, and new materials requiring special approaches [9,10] have been proposed.…”