The Research Of Weldability And Corrosion Resistance For Welded Joint Of Duplex Stainless Steel

Duplex stainless steel is composed of the ferrite and austenite phase, and in general, the less content should reach 30%. Duplex stainless steel,which is a typical representative of the emerging materials, is widely used in relatively harsh application environment field especially in the fields of aerospace industry,marine transportation and nuclear energy,and so on. The reason is that duplex stainless steel has excellent toughness and weldability that the austenitic stainless steel has and the high intensity and resistance to chloride stress corrosion that the ferritic stainless steel has,which make it overcome the problems of traditional single phase stainless steel. Such as,reducing the tendency of welding hot crack, evaluating the resistance of welded joints of intergranular corrosion,stress corrosion in the chloride solutions and the pitting corrosion.The microstructure and element composition of welded joints of SAF2205 duplex stainless steel by different technics were studied by SEM and EDS,the results show that the microstructures of welded joint of 2205 duplex stainless steel are ferrite and austenite. The percentage of austenite in weld metal is about 40%-60%, which is equivalent to that in base material. Element segregation has been found in the test specimens of welded joints. With the welding heat input increasing, the cooling rate decreases relatively in the weld. It also speeds segregation of alloying elements and secondary phase separation of weld metal at grain-boundary, which leads to the decrease of corrosion resistance of welded joints.2205 duplex stainless steel welding joint tensile and bending test results found that the tensile strength of welded joints is close to the base material and the fracture location is on the side of the base material. Charpy impact toughness value of the joint of submerged arc automatic welding process of X type groove is 180J/cm2,which is significantly higher than the other groups.The localized corrosion resistance of the joint of submerged arc automatic welding process of X type groove is the best of all the test specimens of welded joints.Meanwhile the pitting corrosion and intergranular corrosion resistance of welded joints were tested by cyclic anodic polarization curves、critical pitting temperature( CPT) and double loop electrochemical potentiokinetic reactivation(DL-EPR).The results show that.the localized corrosion resistance of the joint of submerged arc automatic welding process of X type groove is the best of all the test specimens of welded joints.