Dissimilar arc welding of advanced high-strength car-body steel sheets
Russo, Spena P
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A widespread usage of new advanced TWIP steel grade for the fabrication of car-body parts is conditional on the deployment of appropriate welding methods, especially if dissimilar welding must be performed with other automotive steel grades. Therefore, the microstructural features and the mechanical response of dissimilar butt weld seams of TWIP and 22MnB5 steel sheets after metal active gas welding are examined. The microstructural and mechanical characterization of the welded joints was carried out by optical metallography, microhardness and tensile testing, and fractographic examination. The heat-affected zone on the TWIP side was fully austenitic and the only detectable effect was grain coarsening, while on the 22MnB5 side it exhibited newly formed martensite and tempered martensite. The welded tensile specimens exhibited a much larger deformation on the TWIP steel side than on the 22MnB5. The fracture generally occurred at the interface between the fusion zone and the heat affected zones, with the fractures surfaces being predominately ductile. The ultimate tensile strength of the butt joints was about 25% lower than that of the TWIP steel.