The antagonism between ‘internal homogeneity’ and ‘large dimension’ in metallic materials is an intrinsic obstacle to the manufacturing of heavyweight yet reliable structural components used for real commercial production. Economical and scalable manufacturing strategies to this challenge need to be acknowledged. This study elucidated the effectiveness and potential of a novel submerged arc additive manufacturing (SAAM) method to homogenize microstructure in-situ and high-efficiently fabricating large-scale components. By leveraging a ‘full-layer-penetrated’ intrinsic heat treatment inherent to the SAAM process, the thoroughly homogenized microstructure of a Mn-Ni-Mo nuclear power high-strength steel consists of finer equiaxial prior-γ grains (~110 µm) along the build direction, with predominantly fine (~7.2 µm) α-Fe phase (bainite) formed inside. Isotropic mechanical characteristics and superior strength-toughness balance (high tensile strength ~740 MPa and low ductile-brittle transition temperature (DBTT) ~− 34 ℃) were achieved and outperformed a wide range of nuclear power or offshore engineering steels processed by conventional methods. The strengthening behaviors in our SAAMed part mainly attribute to the grain boundary and solid solution strengthening whilst the high impact toughness and low DBTT benefit from finer grains and martensite/austenite islands compared to wrought counterparts. It is envisioned that this novel method shows tremendous promise in the additive manufacturing of heavyweight yet homogeneous components.

金属材料中“内部均匀性”和“大尺寸”之间的对抗是制造用于真正商业生产的重量级但可靠的结构部件的内在障碍。需要承认应对这一挑战的经济和可扩展的制造策略。本研究阐明了一种新型埋弧增材制造 (SAAM) 方法在原位均匀化微观结构和高效制造大型部件方面的有效性和潜力。通过利用 SAAM 工艺固有的“全层穿透”内在热处理，Mn-Ni-Mo 核电高强度钢的彻底均匀微观结构由更细的等轴先验γ 晶粒 (~110 µm) 沿构建方向，内部主要形成细小的 (~7.2 µm) α-Fe 相（贝氏体）。实现了各向同性的机械特性和优异的强度-韧性平衡（高抗拉强度 ~740 MPa 和低韧性-脆性转变温度 (DBTT) ~- 34 ℃），并优于通过常规方法加工的各种核电或海洋工程钢。我们的 SAAMed 零件的强化行为主要归因于晶界和固溶强化，而与锻造零件相比，高冲击韧性和低 DBTT 得益于更细的晶粒和马氏体/奥氏体岛。可以预见，这种新方法在重量级但均质部件的增材制造中显示出巨大的前景。