提高淬透性以使板厚方向组织性能均匀化是海洋工程用高品级特厚钢板生产的技术关键和难点。本工作通过热膨胀和Jominy末端淬火实验，并结合铝固氮处理，研究了V分布状态对一种新型980 MPa级海工特厚板用钢在850和910 ℃奥氏体化后的淬透性及显微组织的影响规律。采用EPMA、SEM和TEM等手段表征了钢的显微组织和V原子的分布特性。结果表明，910 ℃奥氏体化过程中AlN的产生能够促进V原子在原奥氏体晶界上的偏聚，提高过冷奥氏体的稳定性并延缓先共析铁素体的转变，从而有效提高海工钢特厚板的淬透性，使其在更宽的冷速范围(对应于更厚的钢板截面)内组织与性能均匀性更好、强韧性匹配度更高。

Improving the hardenability of a ferrous alloy to achieve uniform microstructures and mechanical properties along the direction of the plate thickness is a key challenge in the production of high-grade extra-thick steel plates suitable for marine engineering (hereinafter referred to as “marine steel”). Hence, in this study, the effect of V distribution on the microstructures and hardenability of marine steel was investigated by employing the following procedure: a novel 980 MPa grade extra-thick steel plate was subjected to austenitization at 850 and 910 ^oC; subsequently, through thermal expansion and Jominy end-quench tests combined with fixed nitrogen treatment with aluminum. The microstructures and state of V atoms in the marine steel sample were characterized using SEM, EPMA, and TEM. Results showed that the occurrence of AlN during austenitizing at 910 ^oC promoted the segregation of V atoms on the original austenite grain boundaries, improved the stability of undercooled austenite, and delayed the transformation of proeutectoid ferrite. Thus, this study showed that the incorporation of V in marine steel substantially improved the hardenability of marine steel over a wide range of cooling rates (corresponding to steel plates with thicker cross-sections) and facilitated better microstructure uniformity, performance in marine environments, and matching between the required strength and toughness.