Gtaw Saf2507 Duplex Stainless Steel Welding Joint Organization And Performance Study

SAF2507duplex stainless steel with austenitic stainless steel and ferriticstainless steel features, its advantage is superior corrosion resistance, especiallythe resistance to local corrosion performance, then is equivalent to twice thestrength of austenite and good toughness, and to save the scarce resources ofnickel, this steel is widely used in the petrochemical industry, marine, coal,construction and other industries. On the other hand, SAF2507duplex stainlesssteel can be widely applied to the certain extent, which depends on theperformance of welded joints, and then how to meet the high corrosionresistance after welded is the largest core issues of SAF2507super duplexstainless steel welding, which have the three biggest impact aspects: the first isthe loss of nitrogen in welding process; the second is the heat affected zone andweld can remain a suitable ferrite and austenite; the third is to preventunreasonable of weld heat input, sigma phase and some carbon nitrides, whicheasy to precipitate in the welded joint. Therefore, the research of SAF2507welding technology is of great significance, which is the key to whetherSAF2507can be widely used.According to the welded characteristics of SAF2507duplex stainless steel,using gas tungsten arc welding, applying single factor test method, by two kindsof test schemes, which is to change the proportion of different nitrogenprotective gas and the temperature of solid solution treatment after weld totechnology test, and to determine the influence of two factors on the weldedjoints microstructure, mechanical properties and corrosion resistance, and thenanalyze its mechanism. In the research process, in order to obtain the bestwelded joints, which has the good double phase ratio and performance, thewelding experiments with different nitrogen protective gas, by analyzing theinfluence of nitrogen proportion on organization and properties of joints, to findout the optimized process parameters for offsetting the loss of nitrogen; Aboutsolid solution treatment after weld, in order to eliminate sigma phase and havethe best duplex ratio in the welded joints, the experiments researched different solid solution treatment temperature on the microstructure, mechanicalproperties and corrosion resistance of welded joints. Hope to solve the key to theproblem: the optimal process of offsetting the loss of nitrogen on the weldsurface and the optimization of solid solution treatment temperature afterwelding, making the welded joints of SAF2507has excellent mechanicalproperties, double phase ratio and corrosion resistance, so as to provide apowerful technical support for the application in practice.The results show that, with increasing the content of N₂in the shielding gas,the amount of austenite in weld metal increase, the pitting corrosion resistanceenhance, the use of Ar+2³%N₂welding parameters, the phase ratio, pittingcorrosion resistance and mechanical properties of welded joints are the best,when the content of N₂reach5%, the weld spatter is very big, arc instability andthere are porosity in weld; the welded joints of SAF2507duplex stainless steel isoptimal solid solution treatment at1050℃¹100℃water quench after1h, at thatmoment, the welded joint to eliminate the sigma phase and can keep good ratio,excellent mechanical and corrosion properties, solution treatment significantlyimprove the organization and performance of welded joints.