在焊接热循环过程中，Mn / N质量比对节Ni型双相不锈钢(DSS)的转变奥氏体形成、析出相形成和两相(δ和γ相)比例有较大影响，探究其对多道次焊接热影响区(HAZ)组织转变的影响有利于改善HAZ的综合力学性能。本工作基于2205 DSS对比研究了Mn / N比对DSS固溶态和多道次焊接热影响区(HAZ)组织演变和力学性能的影响。结果表明，高的N含量(Mn / N比为3.77)促进HAZ形成了高体积分数(58.7%)的部分转变奥氏体(PTA)，其抗拉强度和延伸率分别为836 MPa和39.5%，具有高的强塑性。Mn / N比增至17.80时，HAZ中δ/γ相界上形成胞状Cr₂N，魏氏体奥氏体(WA)数量增多导致相界附近铁素体位错墙的形成，使延伸率相对固溶态明显降低。高Mn / N比(65.91) DSS的HAZ中晶界转变奥氏体(GBA)数量先增后减，晶内奥氏体(IGA)和WA数量增多，抑制了Cr₂N析出且强塑性降低。与2205 DSS (Mn / N比为3.06)相比，较低Mn / N比DSS焊接HAZ冲击断口以脆性断裂为主。当Mn / N比为3.77时，高N固溶和Cr₂N析出对奥氏体相的共同强化增大了DSS中HAZ两相硬度差，且大尺寸(Cr, Mn)O夹杂也一定程度促进了裂纹萌生，使其冲击功降至24.2 J。高Mn / N比则会导致HAZ中形成较多的GBA和WA分割细化铁素体，形成细小IGA而阻碍裂纹扩展，且少量细小σ相的析出提高了铁素体硬度，降低两相硬度差，冲击功增加至134.8 J。

Variations in the Mn / N ratio greatly affect the formation of reformed austenite and precipitation and two-phase ratio in duplex stainless steel (DSS) during the welding thermal cycle. Therefore, investigating the influence of the Mn / N ratio on the multipass welding heat-affected zone (HAZ) microstructure is beneficial for enhancing the comprehensive mechanical properties of the HAZ of low-nickel-type DSS thick plates. This study comparatively investigated the effect of Mn / N ratio on the microstructure evolution and mechanical properties of DSS in the solution-treated and multi-pass welded HAZ, with 2205 DSS as a reference. The higher nitrogen content (Mn / N ratio = 3.77) resulted in substantial partial transformed austenite formation with a high volume fraction of 58.7%, yielding a tensile strength of 836 MPa and an elongation of 39.5%, indicating its high strength and plasticity. As the Mn / N ratio increases to 17.80, an increase in the Widmanstätten austenite (WA) amount caused cellular Cr₂N formation at the δ/γ phase interfaces and dislocation walls in ferrite for HAZ, considerably decreasing elongation compared to the solid solution state. For DSS with a high Mn / N ratio of 65.91, the grain boundary austenite (GBA) amount initially increased and then decreased, while the intragranular austenite (IGA) and WA amounts increased in HAZ, inhibiting Cr₂N precipitation and reducing ductility and strength. Compared with the 2205 DSS (Mn / N ratio = 3.06), the fracture surfaces of DSS with lower Mn / N ratios exhibited brittle fracture. The combined strengthening effect of the high-nitrogen solid solution and Cr₂N precipitation on the austenite phase increased the hardness difference between the two phases in the HAZ of the DSS with Mn / N ratio of 3.77. In addition, the formation of some large (Cr, Mn)O inclusions promoted crack initiation to some extent, lowering the impact energy to 24.2 J. High Mn / N ratio led to more GBA and WA segmented ferrite refinement, as well as the formation of small amounts of IGA, which hindered crack propagation. Moreover, the precipitation of a small amount of the σ phase increased the hardness of ferrite, reduced the hardness difference between the two phases, and increased the impact energy to 134.8 J.