The primary components in pressurised water reactors are manufactured by welding thick sections of either SA508 or SA533 pressure vessel steel using processes such as submerged arc welding (SAW) or gas-tungsten arc welding (GTAW). Narrow-groove (NG) variants of these processes have reduced welding times, but thick-section welds still require a large number of passes. In this work, the effects of a large number of welding thermal cycles on the through-thickness variability in microstructure and mechanical properties have been analysed for NG-GTAW and NG-SAW joints made in 78 mm thick SA533 steel. Microstructures were characterised using optical and scanning electron microscopy, while mechanical properties were captured in cross-weld tensile tests using digital image correlation and through tests on coupons extracted exclusively from the weld metal and from the heat-affected zone. Charpy impact testing was used to assess toughness. While the toughness was relatively consistent throughout the SAW joint, significant through-thickness variations in toughness were observed in the NG-GTAW joint, which can be attributed to the varying degree to which the weldment was tempered by subsequent welding thermal cycles.

压水堆的主要组件是通过使用埋弧焊（SAW）或钨极氩弧焊（GTAW）等工艺焊接SA508或SA533压力容器钢的较厚部分来制造的。这些工艺的窄槽（NG）变型减少了焊接时间，但是厚截面焊缝仍需要进行大量焊道。在这项工作中，对于由78毫米厚的SA533钢制成的NG-GTAW和NG-SAW接头，分析了大量焊接热循环对贯穿厚度变化的微观结构和力学性能的影响。使用光学和扫描电子显微镜对显微组织进行表征，而机械性能则通过使用数字图像相关性的交叉焊接拉伸测试以及通过对仅从焊缝金属和热影响区提取的试样进行测试而获得。夏比冲击试验用于评估韧性。尽管整个SAW接头的韧性相对一致，但在NG-GTAW接头中观察到了贯穿厚度的韧性显着变化，这可以归因于随后的焊接热循环对焊接件回火的不同程度。