Investigation Of Residual Stresses Distribution In P92/SUS304 Dissimilar Metal Welded Joints

Dissimilar metal welds between Cr-Mo ferritic steel and austenitic stainless steel are used extensively in conventional as well as in nuclear power generating plants and petrochemical industries.However,premature creep failure is encountered in such dissimilar weld joints.The main reason for these failures are the mismatch between the coefficients of thermal expansion(CTE)between ferritic and austenitic steel and carbon migration from ferritic to austenitic steel.To help reduce the carbon diffusion from ferritic to austenitic side,nickel based fillers are used instead of austenitic filler metal.In this study,dissimilar welded plates between P92 martensitic steel and SUS304 austenitic stainless steel were fabricated using Alloy 82 nickel based filler metal.A thermal-metallurgical-mechanical finite element(FE)method based on Sysweld software was developed to investigate the features of welding residual stress field in P92/SUS304 dissimilar welded joints.The influence of solid-state phase transformation(SSPT),work hardening and annealing softening were carefully considered in the simulation approach.Meanwhile,the hole-drilling strain-gauge method were employed to measure the welding residual stress.The influence of groove type,heat input and filler materials on the distribution of welding residual stresses in P92/SUS304 dissimilar welded joints were discussed.In addition,using the proposed FE method,the residual stress of dissimilar welded pipe between SFVQ1 A low alloy steel and SUSF316 austenitic stainless steel was calculated.The influence of several processes including cladding,buttering,heat treatment,and welding were studied.The simulation results are generally in good agreement with the measurements.Both of the simulation results and experimental measurements show that the profile of longitudinal residual stress is relatively complex in the P92 side due to the influence of SSPT,while there are high tensile stresses in the weld metal and heat-affected zone in the SUS304 side because of working hardening.In P92 steel side,when the temperature raised by the final pass is higher than Ac3 temperature,the final stress is compressive;when the temperature is between Ac1 and Ac3,it is in a transition area;when the temperature is between yield temperature TY and Ac1,the final stress turns to tensile.The hoop stress in P92/SUS304 pipe joint is generally lower than the longitudinal stress in P92/SUS304 plate joint with similar welding condition.The distribution between hoop stress and longitudinal stress is similar.The axial residual stress is complex in the weld start/end area.Based on the simulation results of SFVQ1A/SUSF316 welded joints,it can be found that the influence of SSPT introduced by cladding and buttering is almost eliminated by the following heat treatment.In the simulation of heat treatment process,the influence of material softening,creep effect and the change of material properties on stress generation are important.The simulation results are in good agreement with the measurements.