Hybrid laser arc welding of dissimilar TWIP and DP high strength steel weld

Abstract

Abstract High manganese TWIP steels have a remarkable potential to produce impact resistant car body parts in the automotive industry. Hybrid laser arc welding (HLAW), i.e. simultaneous action of an arc and laser source, can be regarded as the most promising joining technique for such components due to, among other factors, the possibility to use filler metals to avoid improper microstructures and Mn chemical segregations in dissimilar welds of TWIP with other steel grades. In this regard, this work studies the influence of the main welding settings during HLAW of 1.4\u2009mm thick TWIP and Dual Phase (DP) steel sheets used in the automotive industry, which were joined with the use of an austenitic steel filler. Quality of TWIP-DP welds was investigated based on welding parameters, tensile and hardness properties, and microstructures. TWIP and DP steel sheets can be properly joined with a linear heat input in the 50–75\u2009kJ/m range. Welded samples exhibit an average tensile strength and elongation at fracture roughly of 650\u2009MPa and 13%, respectively. These values are similar to those of DP steel, but significantly lower than TWIP steel. The tensile welded samples failed within the heat affected zone of DP steel, being weldments and TWIP steel more resistant. This work confirms that HLAW can be considered a promising solution to join vehicle components made of TWIP and DP sheets when fillers are needed.