Dissimilar Metal Active Gas Welding of TWIP and DP Steel Sheets

Abstract

In the last years, TWIP steels have been proposed for the fabrication of car‐body components, due to their excellent combination of strength and toughness. However, a widespread usage of these steels for such applications is conditional on the employment of dissimilar welding with other automotive high‐strength steel grades. In this study, dissimilar butt weld seams of TWIP and Dual Phase steel sheets fabricated by metal active gas welding are examined. The microstructural and mechanical characterization of the welded joints were carried out by optical metallography, microhardness, tensile testing, and fractographic examination. The heat affected zone on the TWIP side was fully austenitic and the only detectable effect was grain coarsening; on the dual phase side new martensite formed close to the fusion zone, while ferrite, and tempered martensite occurred away from the fusion zone. The welded tensile specimens exhibit a plastic behavior influenced by the TWIP steel, even though with more limited tensile strengths and elongation at fractures. The tensile specimens predominantly broke within the weld seams, with the fractures surfaces being ductile.