Effect Of Different Protective Atmosphere On Microstructure And Properties Of 06Cr19Ni10 Stainless Steel MAG Welding Joints

With the continuous upgrading of China’s railway transportation system,people pay more and more attention to the stainless steel vehicles.The domestic 06Cr19Ni10 austenitic stainless steel has the characteristics of light weight,low price,good corrosion resistance and excellent comprehensive mechanical properties.It has been widely used in the manufacturing field of railway wagons.Metal active-gas arc welding(MAG)is the main connection method for austenitic stainless steel.The cathode spot drift in TIG and MIG can be avoided to improve the weld forming significantly.The protection of gas type is an important factor affecting the mechanical properties and fatigue properties of welded joints.Austenitic stainless steel welding is still one of the research focuses in the railway locomotive manufacturing industry.By analyzing the microstructure,mechanical properties such as tensile,bending and hardness test,pulsating tensile fatigue test and corrosion resistance test,This paper studied microstructure,mechanical properties,fatigue performance and corrosion resistance of 4mm 06Cr19Ni 10 austenitic stainless steel welded joints with 97%Ar + 3%O2 and 95%Ar + 5%C02.The Research indicated:Under the optical microscope,Microstructure of two welding area is white austenite matrix and black skeletal δ ferrite,δ ferrite precipitates uniformly on the austenite matrix.The Heat-affected zone microstructure of both joints is massive austenite and chain ferrite.Heat-affected zone organization has no obvious growth;Tensile strength of both butt joints meets the standard requirements.The tensile strength and yield strength of 97%Ar+3%O2 joint are slightly higher than 95%Ar+5%CO2.The fracture locations of both joint tensile specimens are located in the heat affected zone.No cracks appear in the two sets of specimens in the bending test.Both joints have good bending plasticity;Weld zone hardness distribution of 97%Ar+3%O2 joint is basically the same as 95%Ar+5%CO2 joint.The weld zone of both joints is the area with the lowest hardness value.The average hardness values in the heat affected zone of two groups are basically similar,slightly lower than the base metal;Fatigue limit σ0.1 of joints of 97%Ar+3%O2 group is not much different from that of 95%Ar+5%CO2,Fatigue cracks started in the fusion zone,cracking is caused by inclusion of oxides;After intergranular corrosion,the corrosion rate of the 97%Ar+3%O2 sample was significantly lower than that of the 95%Ar+5%CO2 group.There are no obvious intergranular corrosion cracks on the surfaces of the two butt joints;electrochemical corrosion tests showed that the 97%Ar+3%O2 group had better electrochemical corrosion performance.The weld center of both joints is the area with the lowest pitting resistance.