Metals and Materials International ( IF 3.3 ) Pub Date : 2021-09-14 , DOI: 10.1007/s12540-021-01090-8 Junsang Lee 1 , Dongil Kwon 1 , Jong-hyoung Kim 1 , Jong Sung Kim 2 , Bongsang Lee 3 , Sungwoo Cho 4
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This study analyzes the effects of post-weld heat treatment (PWHT) on the mechanical properties and microstructures of SA-508 Gr.1a welds and proposes a new PWHT exemption criterion based on nonductile fracture evaluation considering welding residual stress. The welding coupons were prepared with submerged-arc welding, gas-tungsten arc welding, and shielded-metal arc welding, using ferritic steel, SA-508 Gr.1a. The microstructure of the heat-affected zone (HAZ) was analyzed using optical microscopy, electron-back-scatter diffraction and Vickers hardness testing. The mechanical properties of the welds were evaluated by uniaxial tensile test, transverse side bend test, Charpy V-notch impact test and side bend test. Bainite and ferrite structures formed mainly in the HAZ, and the grain size became coarser with proximity to the surface and fusion line. The mechanical properties did not depend strongly on PWHT, weldment thickness or welding techniques, and they satisfied the welding procedure qualification test specified in the ASME Boiler & Pressure Vessel code. Welding residual stresses were considered in assessing structural integrity using nonductile fracture evaluation. A margin of safety against nonductile fracture with residual stress was calculated for Korean Standard Nuclear Power Plant steam-generator welds, using its design parameters and operating conditions, and this safety margin is suggested as an acceptance criterion for residual stress for exemption from PWHT.
Graphic abstract
中文翻译：
焊后热处理条件对 SA508 Gr.1a 厚焊件力学性能、显微组织和非延性断裂行为的影响
本研究分析了焊后热处理 (PWHT) 对 SA-508 Gr.1a 焊缝力学性能和显微组织的影响，并基于考虑焊接残余应力的非延性断裂评估提出了一种新的 PWHT 豁免标准。焊接试样采用埋弧焊、钨极气体保护焊和保护金属电弧焊制备，使用铁素体钢 SA-508 Gr.1a。使用光学显微镜、电子背散射衍射和维氏硬度测试分析热影响区 (HAZ) 的微观结构。通过单轴拉伸试验、横向侧弯试验、夏比V型缺口冲击试验和侧弯试验对焊缝的力学性能进行评价。贝氏体和铁素体组织主要形成在热影响区，晶粒越靠近表面和熔合线越粗。机械性能并不强烈依赖于 PWHT、焊件厚度或焊接技术，它们满足 ASME 锅炉和压力容器规范中规定的焊接工艺鉴定测试。在使用非延性断裂评估来评估结构完整性时考虑了焊接残余应力。使用其设计参数和运行条件计算了韩国标准核电站蒸汽发生器焊缝的残余应力非延性断裂安全裕度，并建议将该安全裕度作为残余应力免除焊后热处理的验收标准。在使用非延性断裂评估来评估结构完整性时考虑了焊接残余应力。使用其设计参数和运行条件计算了韩国标准核电站蒸汽发生器焊缝的残余应力非延性断裂安全裕度，并建议将该安全裕度作为残余应力免除焊后热处理的验收标准。在使用非延性断裂评估来评估结构完整性时考虑了焊接残余应力。使用其设计参数和运行条件计算了韩国标准核电站蒸汽发生器焊缝的残余应力非延性断裂安全裕度，并建议将该安全裕度作为残余应力免除焊后热处理的验收标准。
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