With the rapid development of industry, narrow-groove welding has become the first choice for thick-plate welding in fields such as naval architecture, ocean engineering, the petrochemical industry, and heavy machinery. Narrowgroove welding offers the promise of a dramatically improved weld completion rate and significantly reduced heat input (Refs. 1, 2). According to different heat sources, it includes narrow-groove electron beam welding (EBW), narrow-groove laser beam welding (NG-LBW), and

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... rrowgroove arc welding technologies. Considerable efforts have been devoted to the development of EBW as an alternative fabrication technique for nuclear pressure vessel production (Refs. 3, 4) . The double-wall vacuum vessel inner components in advanced fusion reactors like keys, shells, and ribs are usually manufactured using EBW (Ref. 5). However, the high-priced equipment and vacuum environment requirement significantly limit its wide application. For laser beam welding, typical penetration depths are in the range of 1-2 mm/kW laser power (Ref. 6). Narrow-groove laser welding can weld materials with thicknesses that are well beyond the capabilities of single-pass autogenous laser welding (Ref. 7). Nilsen et al. (Ref. 8) proposed a dual-vision and spectroscopic sensing approach to trace narrow-groove butt joints during laser welding, which avoided detrimental incomplete sidewall fusion. However, the high-price equipment and high-cost maintenance significantly limit its industrial application. Generally, the heat input for high EBW is much lower than that for arc welding, as are the expected levels of residual stress and distortion. However, its costs are much higher than that of arc welding. Based on the advantages like low cost, easy accessibility, and easy operation, arc welding has been widely applied in various industrial fields. Narrowgroove arc welding methods mainly include submerged arc welding (SAW), gas metal arc welding (GMAW), and gas tungsten arc welding (GTAW). Narrow-Groove SAW and GMAW Submerged arc welding (SAW) is a high-efficiency welding method featuring high deposition efficiency, slag protection, and the absence of a strong arc (Ref. 9). Manzoli et al. (Ref. 10) employed a new submerged-arc narrow-groove