Resistance Spot Welding of Three-Sheet High-Strength Steels by Experimental and Simulation

Three sheets Spot welding configuration has been introduced in automotive industry which is more challenging comparing to two sheets spot welding. The goal of this article was to investigate resistance spot welding of three complicated configuration of three sheet high strength steels. The combinations used were ((GA SGARC (0.7t) + Al-Coated HPF (1.2t) + DP590 (1.4t)) ,(GA SGARC(0.7t) + TRIP780(1.2t) + DP590(1.4t)) and (GA SGARC(0.7t)+Zn-coated HPF(1.2t)+ DP590(1.4t)). The weldable current range for each combination was determined. The dissimilarity of expulsion in each combination was investigated. The trip combinations were showing earlier expulsion comparing to other combinations. It was observed that for trip combination the nugget is higher in sheet direction. For HPF combination the expulsion was observed in electrode sheet interface. But in the case of Zn coated HPF the expulsion was occurred in sheet-sheet interface. The reason for different expulsion surface was also investigated. It was observed that for Al-coated HPF the heat generation was occurring in electrode sheet interface, For Zn-coated HPF combination the heat generation initiated in sheet-sheet interface. Which might means the Al coating is creating the resistance in the path of current in electrode sheet interface but Zn coating privileged conducting the current to the sheet-sheet interface. The coating layer behavior between Al-coated HPF and Zn-coated HPF combination also investigated. Having set the background of experimental results, the experimental results were compared with SORPAS simulation results. SORPAS available welding range and expulsion of each combination was compared with experimental results. The dissimilarity with experimental and simulation seems to be due the difference of experimental conditions.

 Key words: Three sheets weld; Weldability; Dissimilar combinations; expulsion; Simulation