Microstructure and Mechanical Properties of the Ternary Gas Shielded Narrow-Gap GMA Welded Joint of High-Strength Steel

An 80%Ar-10%CO2-10%He ternary gas mixture was used as the shielding during narrow-gap welding of thick Q690E high-strength steel plates. Complete and defect-free welded joints were obtained, microstructure mechanical properties joint investigated. The weld zone consists a solidification area interlayer zone, heat-affected coarse-grain (CG-HAZ) fine-grain (FG-HAZ). microstructures are mainly lath bainite (LB), acicular ferrite (AF), granular (GB). CG-HAZ is martensite (LM) FG-HAZ GB. Methods with different heat inputs to study their effects on joint. It found that better lower input. With tandem wire GMA welding, tensile strength declined from 795.3 718.3 MPa impact toughness at −40 °C resulted in weak position which 76~81 J 55~69 J, when speed reduced 350 250 mm/min. oscillating-arc achieved 853.4 around 69~87 J. results indicated that, under appropriate input, exceeds 770 low temperature 69 A 155 mm-thick obtained meets requirements offshore drilling platforms.