Effect of Post-Weld Heat Treatment Conditions on Mechanical Properties, Microstructures and Nonductile Fracture Behavior of SA508 Gr.1a Thick Weldments

Abstract This study analyzes the effects of post-weld heat treatment (PWHT) on mechanical properties and microstructures SA-508 Gr.1a welds proposes a new PWHT exemption criterion based nonductile fracture evaluation considering welding residual stress. The coupons were prepared with submerged-arc welding, gas-tungsten arc shielded-metal using ferritic steel, Gr.1a. microstructure heat-affected zone (HAZ) was analyzed optical microscopy, electron-back-scatter diffraction Vickers hardness testing. evaluated by uniaxial tensile test, transverse side bend Charpy V-notch impact test test. Bainite ferrite structures formed mainly in HAZ, grain size became coarser proximity to surface fusion line. did not depend strongly PWHT, weldment thickness or techniques, they satisfied procedure qualification specified ASME Boiler & Pressure Vessel code. Welding stresses considered assessing structural integrity evaluation. A margin safety against stress calculated for Korean Standard Nuclear Power Plant steam-generator welds, its design parameters operating conditions, this is suggested as an acceptance from PWHT. Graphic abstract