Investigation on resistance spot welding of TWIP steel sheets
Russo, Spena P
De, Maddis M
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A widespread usage of new advanced high strength TWIP steels in the automotive industry is conditional on proper assembly operations by welding. Therefore, the effects of the main important process parameters on the mechanical and microstructural properties of resistance spot welded TWIP sheets are examined here. The welding parameters used were the welding current, clamping force, and welding time. An L-9(33) orthogonally array was used to design the experimental tests. The mechanical response of the welded joints was assessed by tensile shear tests and Vickers microhardness measurements. The effects of the welding parameters on the fracture mode of the tensile shear specimens were also investigated. Some combinations of the welding process parameters guarantee acceptable tensile shear strengths for the automotive industry. The tensile shear samples mainly failed by interfacial fracture mode, while partial thickness with pull out fractures were observed in the samples when a high welding current and clamping force were used. Improper clamping force and welding current promoted excessive metal expulsions and, in turn, the formation of welding defects in the weld spots.