Influence Of Shielding Gas On The Structure And Properties Of MAG Welded Joints Of S355J2W+N Weathering Steel Plate

With the development of new welding technology and new materials,gas shielded welding is also constantly developing.Shielding gas is one of the important parameters in the welding process,but its importance is often underestimated.Due to external influences,most domestic companies choose 80%Ar+20%CO₂ as welding shielding gas.In many welding environments,80%Ar+20%CO₂ as a welding shielding gas is not the best shielding gas.To maximize the benefits,it is necessary to select the best shielding gas to meet the actual needs of welding.In this paper,different shielding gases are used for high-frequency pulse MAG welding of S355J2W+N weathering steel plate,and the process comparison test is carried out;through the study of the welding test plate thermal cycle temperature,residual stress,macroscopic morphology,metallographic microstructure and the law of changes in mechanical properties,And analyze the oxygen content and titanium content of the weld metal of the welding test plate,and finally obtain the optimal shielding gas,which provides theoretical guidance for the welding of S355J2W+N weathering steel in the bogie.1)The cladding metal and base metal of the butt joints of all gas shielded welding test panels are well fused with no defects such as cracks and pores.The back welding seam has realized"anti-melting",and all the butt joints of shielding gas welding test panels are realized on one side.Welding is formed on both sides.2)The tensile failure position of the butt joints of all shielding gas welding test panels is in the base material,and ductile fracture occurs;when the bending angle of the bending test panel reaches 180°,the bending tensile surface of the welding test panels of different shielding gases is not found Obvious cracks indicate that the welded joint has excellent plasticity.In the impact test,28%CO₂ binary argon-enriched gas（M31 type）is used as the shielding gas for the welding test plate.The butt joint is the impact energy of the weld or the heat-affected zone.Both are the biggest.3)Through comprehensive analysis of the thermal cycle temperature,residual stress,macroscopic morphology,microstructure,mechanical properties,oxygen content and titanium content of the butt joint of the welding test plate,28%CO₂ binary argon-rich mixed gas（M31type）The overall performance of the welding test board as a welding shielding gas is the best.