1. Chemical Composition & Duplex Structure
The core of F55’s chemical design lies in its high alloying elements, including:

• Chromium (Cr): 24-26%, providing exceptional oxidation resistance and corrosion protection, especially in oxidative environments.

• Molybdenum (Mo): 3-4%, enhancing resistance to reducing acids (like sulfuric and hydrochloric acid) and chloride-induced corrosion.

• Nickel (Ni): 6-8%, balancing the duplex structure while improving toughness.

• Nitrogen (N): 0.2-0.3%, solid solution strengthening to improve strength and optimize PREN value.

• Tungsten (W) & Copper (Cu): 0.5-1.0% each, further enhancing localized corrosion and resistance to non-oxidizing acids.

• The ferrite and austenite phases are evenly balanced (1:1 ratio) and maintained through solution treatment (1050-1120°C rapid cooling) to avoid the precipitation of harmful phases (e.g., sigma phase), ensuring toughness and corrosion resistance.

2. Physical & Mechanical Properties

（1）Physical Properties

• Density: 8.0 g/cm³

• Melting Point: 1400-1450°C

• Thermal Conductivity: 12.8 W/m·K

• Thermal Expansion Coefficient: Approx. 17.2×10⁻⁶/K, suitable for environments with frequent temperature changes.

（2）Mechanical Properties

• Tensile Strength: ≥750 MPa

• Yield Strength: ≥550 MPa

• Elongation: ≥45%

• Hardness: ≤270 HB

• F55’s strength is 2-3 times that of standard austenitic stainless steels (e.g., 316L), allowing for reduced component wall thickness and lightweight design.

3. Corrosion Resistance
（1）PREN (Pitting Resistance Equivalent Number): ≥40

（2）Formula: PREN = %Cr + 3.3×%Mo + 16×%N

（3）F55 excels in chloride, acidic media (H₂S, CO₂), and is resistant to:

• Pitting Corrosion

• Crevice Corrosion

• Stress Corrosion Cracking (SCC)

• Erosion Corrosion

（4）Temperature Limitations

• For long-term use, the temperature should not exceed 300°C, as higher temperatures may degrade material toughness.

4. Typical Applications

• Marine Engineering: Subsea pipelines, ship propellers, offshore platform structures—resistant to seawater corrosion and salt mist environments.

• Petrochemical: Oil & gas pipelines, reactors, storage tanks, and hydrogenation equipment—ideal for sulfurous and chloride-induced corrosion.

• Energy & Environmental Protection: Desalination systems, flue gas desulfurization (FGD)—able to withstand high salinity and acidic media.

• Other Sectors: Nuclear power equipment, food processing machinery, medical devices—ensuring hygiene and corrosion resistance.

5. Processing & Usage Considerations
（1）Welding Process:

• Use high-alloy welding materials (such as nickel-based filler rods or ER2594 electrodes), control heat input and interpass temperature (<150°C), and prevent sigma phase precipitation that can cause embrittlement.

• Post-welding acid pickling or passivation is required to restore corrosion resistance.

（2）Heat Treatment:

• Solution treatment at approximately 1100°C with rapid cooling to stabilize the duplex microstructure; avoid holding between 800-950°C to prevent sigma phase formation.

（3）Surface Treatment:

• Sandblasting, electropolishing, and other methods enhance surface corrosion resistance. Regular non-destructive testing of welds and stress concentration areas is recommended.

6. Future Development Trends

（1）Material Upgrades: 

By adjusting the proportions of chromium, molybdenum, tungsten, and other elements, F55 derivatives with even higher PREN values (e.g., 45+) can be developed to meet deep-sea and polar environment requirements.

（2）Manufacturing Technology: 

The combination of 3D printing for custom complex parts or ceramic coatings to enhance wear resistance and anti-biofouling capabilities.

7.Conclusion
F55 duplex stainless steel, with its balanced duplex microstructure and comprehensive performance, is the ideal material choice for demanding working conditions. Its applications have expanded from traditional industries to emerging fields, and with advances in material science and manufacturing technology, F55 will continue to solidify its position as a “corrosion-resistant and high-strength benchmark.”

8.About Suzhou Bolaibao Metal
Suzhou Bolaibao Metal specializes in the supply and technical services of high-performance duplex stainless steels, including F55 (UNS S32760 / EN 1.4501), nickel alloys, and special alloys. With a stable inventory, precision processing equipment, and an experienced engineering team, we are dedicated to providing professional material selection advice, custom cutting, and comprehensive after-sales technical support for high-end industries like marine engineering, petrochemicals, and energy & environmental protection.

Bolaibao always adheres to the philosophy of “Technology First, Quality Above All” to control product quality with stringent standards and help our clients solve critical material challenges, ensuring safe and stable operation of equipment in extreme conditions. Choosing Bolaibao means choosing a reliable partner for material solutions.

For more technical information and cooperation plans, feel free to contact us:

• Phone: +86 15366282159

• Email: sale@bolaibao1.com

• Website: www.bolaibao1.com