Duplex Steel Flanges
Duplex Steel Flanges are engineered to provide exceptional mechanical strength, superior resistance to corrosion, and long-lasting durability in some of the harshest industrial environments. Unlike conventional stainless steels, Duplex steels are designed with a dual-phase microstructure that combines both austenitic and ferritic properties. This unique balance delivers outstanding toughness, high yield strength, and excellent resistance to stress corrosion cracking.
Duplex Steel Flanges are widely used in industries such as oil & gas, chemical processing, desalination, marine, and power generation, where safety and performance under high pressure and corrosive conditions are critical. Available in various types such as slip-on, weld neck, socket weld, blind, lap joint, and threaded flanges, they ensure reliable connection and sealing for pipelines and equipment.
Chemical Composition
The exceptional properties of Duplex Steel Flanges stem from their carefully controlled chemical composition.
Grade S31803 and S32205 are standard duplex steels offering around 22–23% chromium, 4.5–6.5% nickel, and 2.5–3.5% molybdenum with nitrogen content up to 0.20%. This blend provides excellent resistance to pitting and crevice corrosion while maintaining high mechanical strength.
Super Duplex grades S32750 and S32760 contain higher levels of chromium (24–26%) and nickel (6–8%), along with added molybdenum and nitrogen. These alloys offer even greater resistance to chloride-induced corrosion and deliver enhanced strength, making them ideal for highly saline and aggressive environments such as seawater applications and subsea pipelines.
This balanced composition makes Duplex Steel Flanges superior to standard stainless steels in terms of both corrosion performance and durability.
Mechanical Properties
Duplex Steel Flanges are well-regarded for their high mechanical strength and thermal stability.
Standard Duplex grades S31803 / S32205 have a density of about 7.805 g/cm³ and a melting range between 1420°C and 1465°C. This enables them to perform reliably in elevated temperature environments while retaining excellent toughness.
Super Duplex grades S32750 / S32760 feature a density of 7.8 g/cm³ with a melting point of around 1350°C (2460°F). These grades are designed to withstand extreme pressure and chloride stress conditions, making them suitable for offshore and marine engineering applications.
With nearly double the yield strength of conventional stainless steels, Duplex flanges allow the use of thinner material sections, reducing overall weight and cost without compromising safety.
Key Advantages of Duplex Steel Flanges
Superior Corrosion Resistance – Effective against pitting, crevice corrosion, and chloride stress corrosion cracking.
High Strength – Nearly twice the yield strength of austenitic stainless steels.
Thermal and Structural Stability – Performs efficiently in both high and sub-zero temperatures.
Cost Efficiency – Reduced material thickness and longer service life lower total project costs.
Versatile Applications – Suitable for industries requiring robust performance under harsh conditions.
Applications of Duplex Steel Flanges
Duplex Steel Flanges are trusted across multiple industries for their exceptional reliability and long service life:
Oil & Gas Industry – Subsea systems, pipelines, and high-pressure processing equipment.
Chemical & Petrochemical Plants – Heat exchangers, reactors, and pressure vessels.
Marine & Offshore – Seawater handling, ballast systems, and desalination units.
Pulp & Paper Industry – Bleaching equipment, digesters, and chemical tanks.
Power Generation – Flue gas desulfurization units and heat recovery systems.
Conclusion
Duplex Steel Flanges combine high strength, excellent corrosion resistance, and cost efficiency, making them one of the most reliable choices for demanding industrial applications. Whether in offshore platforms, chemical processing plants, or desalination projects, these flanges are engineered to withstand extreme conditions while delivering consistent performance and durability.
Connect with us
Quality Pipe Fitting Solutions
Reliable, durable, and precise pipe fittings for every industrial need.
Buttweld Fittings
High-quality buttweld fittings for secure, leak-proof pipe connections.
Explore more
Flanges
Durable industrial flanges for reliable piping connection and pressure sealing.
Explore more
Threaded Fittings
Precision threaded fittings for secure, easy, and leak-resistant pipe connections.
Explore more
Socket Weld Fittings
Robust socket weld fittings for high-pressure, leak-proof pipe connections.
Explore more
Pre Fabricated Fittings
Custom pre-fabricated fittings for efficient, accurate, and time-saving piping installations.
Explore more
Fastners
High-performance fasteners for strong, reliable, and durable industrial connections.
Explore more
Pipes & Tubes
Premium pipes and tubes for efficient flow and structural reliability in industrial systems.
Explore more
Spades & Ring Spacers
Spades and ring spacers for safe pipeline isolation and maintenance operations.
Explore moreFAQs - Duplex Steel Flanges
uplex Steel flanges feature a dual-phase microstructure combining ferritic and austenitic properties, offering high strength, corrosion resistance, and durability in aggressive industrial environments.
They are widely used in oil and gas, petrochemical, desalination, marine, pulp and paper, and power generation industries due to their reliability under extreme conditions.
Duplex flanges typically contain chromium, nickel, molybdenum, and nitrogen, offering superior resistance to pitting, crevice corrosion, and chloride-induced cracking compared to conventional stainless steels.
They offer nearly double the yield strength of standard stainless steels, with excellent toughness, ductility, and thermal stability, ensuring performance under both high and sub-zero temperatures.
Common types include slip-on, weld neck, socket weld, blind, lap joint, and threaded flanges, each designed for specific piping and pressure system requirements.
Super Duplex grades like S32750 and S32760 have higher chromium, nickel, and molybdenum levels, providing enhanced strength and superior resistance in highly saline or offshore environments.
Their high strength allows thinner material sections, reducing overall weight and material costs, while their durability lowers long-term maintenance and replacement expenses significantly.
Yes, their high chromium, molybdenum, and nitrogen content makes them exceptionally resistant to seawater-induced pitting, crevice corrosion, and chloride stress cracking in marine applications.
Duplex flanges perform well in elevated temperatures up to 1350°C, as well as cryogenic conditions, maintaining strength, toughness, and structural reliability throughout.
They are critical in subsea pipelines, chemical reactors, desalination units, offshore platforms, digesters, and flue gas systems requiring corrosion resistance and mechanical strength.