Study On Microstructure And Properties Of Welding Joint In Solid Cored Wire MIG Of 2205 Duplex Stainless Steel

With its excellent mechanical properties and corrosion resistance,2205 duplex stainless steel(DSS 2205)has been widely used in container manufacturing,petrochemical industry,marine shipping,desalinatio n and other industries in recent years.DSS 2205 is accompanied by the diffusion of Cr,Ni,Mo,N and other elements in the welding process,and it is easy to precipitate harmful phases.Therefore,it is necessary to select a welding process with high efficiency,low energy consumption and high welding quality in the actual large-scale production process.There are many kinds of welding processes in DSS 2205,among which MIG welding is the most widely used welding process at present.Although the process co ntrol of flux cored MIG welding is simple,its welding wire is not easy to preserve,its cost is high,and it is easy to cause slag inclusion in the welding process.Solid core welding can effectively overcome the above shortcomings and reduce the cost of welding production.Therefore,this paper focuses on the microstructure and properties of DSS2205 solid core MIG welding joint.First of all,this paper took DSS 2205 welding joint as the research object,and compared the microstructures and properties of different welding processes(flux cored MIG welding,manual argon arc welding,manual electrode arc welding and solid cored MIG welding).O n this basis,the effects of different shielding gases(100%Ar,98%Ar+2%N₂ and 98%Ar+2%O₂)and different stress relief methods(air shovel treatment,ultrasonic treatment,250?/24h)on the residual stress,corrosion resistance and mechanical properties of solid core MIG welding joints were studied,which provided data and theoretical basis for the improvement of so lid core MIG welding process.The results showed that the stress states of the four welding processes were different along the weld direction(X direction)and vertical weld direction(Y direction).With different welding processes,the tensile strength and fracture position of the welded joint were different,and would affect the fracture characteristics.Among the four welding processes,the best resistance to pitting corrosion was manual argon arc welding,and the worst was flux cored MIG welding.The intergranular corrosion did not occur in the four kinds of joint intergranular corrosion tests,but overall uniform corrosion.The stress states of X-direction and Y-direction near the weld of DSS 2205 solid core MIG welding joint welded under three kinds of shielding gases were the same,and the sizes were different.Under three kinds of shielding gas,the lowest strength of the welded joint was at the weld,the highest strength of the welded joint was at the heat affected zone,and the fracture of the tensile specimen was at the weld.The best resistance to spot corrosion,intergranular corrosion and electrochemical corrosion was under 98%Ar+2%N2 shielding gas,and the worst was under Ar shielding gas.Also it showed that the increase of 2%O₂ and N₂ in argon improved the corrosion performance of the welded joint,but the increase of 2%N2 had a better effect on the strength.In the three ways of stress removal,the residual stress along the weld and vertical weld after air shovel treatment and ultrasonic treatment changed from tensile stress to compressive stress;the residual stress redistributed along the weld and vertical weld after heat treatment at 250?for 24 hours,and the change of tensile stress in the two directions was not obvious.The dislocatio n density of austenite and ferrite phase in the weld was increased by the air shovel and ultrasonic treatment,and the strength of the weld and the heat affected zone was effectively improved;the heat treatment after 24hours at 250?was equivalent to the annealing treatment of the welded joint,the dislocation density of austenite and ferrite phase was reduced,and the strength of the weld and the heat affected zone was reduced to a certain extent.Three kinds of stress relief treatments had effectively improved the corrosion resistance(spot corrosion,intergranular corrosion and electrochemical corrosion)of DSS 2205 solid core MIG welding joint,the best of which were air shovel and ultrasonic treatment.