Study on microstructures and mechanical properties of laser–arc hybrid welded S355J2W+N steel

•Laser–MAG hybrid welding is conducted to 16 mm S355J2W+N plates by three passes.•Advantages of hybrid welding are illustrated by comparing with MAG welded joint.•The transition region could be vulnerable owing to the stress concentration.•“Opposite-growing structure” in laser zone tends to form a kind of weak interface.

The technology of laser–MAG hybrid welding was used on 16 mm thick plate of weathering steel S355J2W+N. Under the welding parameters used in the experiment, full penetration weld without flaws such as pores, cracks and lack of fusion was obtained by a three-layer and three-pass welding technique. In this study, the outstanding advantages of laser–arc hybrid welding were summarized by comparison with welded joint of traditional MAG welding. The microstructure of hybrid welded joint has also been detailed investigated. Besides, the mechanical property tests were performed according to corresponding European standards. Furthermore, the tensile and impact strength of laser–MAG hybrid welded joint turned out to be almost as good as base metal. Most of the hybrid welded joints had a good bending property, but for some sample, there was a micro-crack with the length of 0.9 mm emerging within the transition region where contraction stress would accumulate and remain, being one of the most vulnerable zones in weld metal. The results show that laser–MAG hybrid welding technology is appropriate for S355J2W+N thick plate welding, in favor of not only improving the product performance, but also lowering the production cost and improving the productivity.