Comprehensive Comparative Analysis of Stainless Steels S32205 and S31254

1. Chemical Composition Differences

S32205 (Duplex Stainless Steel)

· Main Components: Chromium (22–23%), Nickel (4.5–6.5%), Molybdenum (3–3.5%), Nitrogen (0.14–0.20%).

· Features: Balanced strength and corrosion resistance through a dual-phase (austenitic + ferritic) microstructure. High chromium and nitrogen content enhance resistance to pitting corrosion.

S31254 (Super Austenitic Stainless Steel)

· Main Components: Chromium (19.5–20.5%), Nickel (17.5–18.5%), Molybdenum (6.0–6.5%), Nitrogen (0.18–0.25%).

· Features: Exceptional resistance to chloride corrosion due to ultra-high molybdenum and nickel content. It is a high-alloy austenitic steel.

Key Difference: S31254 has twice the molybdenum and higher nickel than S32205 but slightly lower chromium. S32205 optimizes performance via its dual-phase structure, while S31254 relies on high alloying for corrosion resistance.

2. Mechanical Properties Comparison

S32205

· Yield Strength: ≥450 MPa, Tensile Strength: ≥620 MPa, Elongation: ≥25%.

· Advantages: The dual-phase structure provides high strength, suitable for high-stress environments (e.g., offshore platforms, pressure vessels).

S31254

· Yield Strength: ≥300 MPa, Tensile Strength: ≥650 MPa, Elongation: ≥40%.

· Advantages: Superior ductility and toughness, ideal for complex forming (e.g., chemical reactors, seawater desalination equipment).

Key Difference: S32205 offers higher strength, whereas S31254 excels in ductility, making them suitable for different mechanical demand scenarios.

3. Heat Treatment Methods

S32205

· Solution Treatment: Heated to 1020–1100°C, then rapidly cooled to dissolve carbides and maintain the dual-phase structure.

· Welding: Requires controlled interpass temperature to avoid ferrite imbalance.

S31254

· Solution Treatment: Requires higher temperatures (1150–1200°C) to ensure austenitic stability.

· Welding: Must use high-alloy filler materials (e.g., ERNiCrMo-3) to prevent σ-phase precipitation.

Key Difference: S31254 demands higher heat treatment temperatures due to its high alloy content and has more complex welding requirements.

4. Application Scenarios

S32205

· Typical Uses: Marine engineering (seawater piping, platforms), petrochemicals (chloride-containing equipment), desulfurization units.

· Applicable Conditions: Moderate to high chloride environments (≤5000 ppm), temperatures ≤90°C.

S31254

· Typical Uses: Seawater desalination evaporators, high-concentration hydrochloric acid equipment, high-temperature chloride environments.

· Applicable Conditions: Extreme corrosion environments (chlorides ≤50,000 ppm), temperatures ≤150°C.

Key Difference: S32205 is suitable for moderate corrosion conditions, while S31254 is designed for high-corrosion, high-temperature extreme environments.

5. Referenced Standards

S32205

· International: ASTM A240/A240M (plates), EN 1.4462.

· China: GB/T 20878 (S22053).

S31254

· International: ASTM A240/A480 (plates), EN 1.4547 (254SMO).

· China: GB/T 20878 (S31252).

Key Difference: The two steels are classified differently in standard systems—S32205 is a duplex steel, while S31254 is a super austenitic steel.

Summary

Selection Recommendations:

· Choose S32205 if you need a balance of strength and chloride corrosion resistance (e.g., offshore platforms).

· Choose S31254 if you need to withstand extremely high chloride concentrations or high-temperature acidic media (e.g., chemical reactors).