Lean Duplex Stainless Steel Weld Heat-Affected Zone Corrosion

The invention changes the compositional parameters by precisely controlling the content ranges of Ni (1.0-4.0%), Mo (1.0% or less), V (0.05-0.5%), and N (0.10-0.25%), along with their interaction products (N×V≥0.005, N×Nb≥0.003). This parameter optimization resolves the contradiction by achieving the desired balance between cost reduction and maintaining corrosion resistance/toughness in the weld heat affected zone.

The invention creates a composite alloy system that combines multiple elements (Cr, Ni, Mo, Cu, V, Nb, N) in specific proportions to achieve synergistic effects. The combination of V and Nb with controlled N content creates a composite microstructure that prevents chromium nitride precipitation, thereby maintaining both cost-effectiveness and mechanical properties in the weld heat affected zone.

The invention optimizes the Ni content parameter within the range of 1.0-4.0% and combines it with controlled Mo (≤1.0%), V (0.05-0.5%), and N (0.10-0.25%) contents. The interaction parameter N×V≥0.005 is specifically controlled to prevent chromium nitride precipitation. This multi-parameter optimization allows reduced Ni content while maintaining corrosion resistance in the weld heat affected zone.

The invention introduces V and Nb as intermediary elements that mediate between Ni content reduction and corrosion resistance maintenance. These elements form carbides and nitrides that stabilize the microstructure and prevent harmful chromium nitride precipitation, thereby compensating for the reduced Ni content and maintaining corrosion resistance in the weld heat affected zone.

The invention changes the Mo content parameter to ≤1.0% (substantially reduced from conventional 3-4%) and compensates by optimizing other parameters: Ni (1.0-4.0%), Cu (0.1-3.0%), V (0.05-0.5%), and N (0.10-0.25%). The controlled interaction products (N×V≥0.005, N×Nb≥0.003) prevent chromium nitride precipitation, thereby maintaining corrosion resistance and toughness with substantially reduced Mo content.

The invention merges the functions of multiple elements to compensate for reduced Mo content. V and Nb are combined with controlled N content to prevent chromium nitride precipitation, while Cu (0.1-3.0%) and Ni (1.0-4.0%) work together to maintain austenite phase stability and corrosion resistance. This functional merging allows Mo reduction while maintaining weld heat affected zone properties.

The invention optimizes the content parameters of V (0.05-0.5%) and Nb (0.02-0.20%) to achieve the minimum effective dosage for suppressing chromium nitride precipitation. The interaction parameters N×V≥0.005 and N×Nb≥0.003 define the threshold for effectiveness. This parameter optimization achieves the desired reliability improvement while minimizing the cost increase from V and Nb addition.

The invention applies partial action by adding small amounts of V (0.05-0.5%) and Nb (0.02-0.20%) that are sufficient to suppress chromium nitride precipitation without excessive addition. This controlled partial addition achieves the necessary corrosion resistance and toughness improvement while minimizing the cost impact of these expensive alloying elements.