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What Different Materials Are Used for Duplex Flanges


Duplex flanges are manufactured using duplex stainless steels, which are known for their excellent corrosion resistance and high strength. Duplex stainless steels have a mixed microstructure of austenite and ferrite, which gives them unique properties making them suitable for demanding applications. Here are some of the key materials used for duplex flanges:

Duplex Stainless Steel Grades for Flanges

1. Duplex 2205 (UNS S31803/S32205)

  - Composition: Approximately 22% chromium, 5% nickel, and 3% molybdenum.

  - Characteristics: High strength, excellent resistance to pitting, crevice corrosion, and stress corrosion cracking. Commonly used in chemical processing, petrochemical, and marine environments.

2. Super Duplex 2507 (UNS S32750)

  - Composition: Approximately 25% chromium, 7% nickel, and 4% molybdenum, with a small amount of nitrogen.

  - Characteristics: Higher strength and corrosion resistance compared to standard duplex grades. Excellent resistance to chloride-induced stress corrosion cracking and erosion. Used in oil and gas, offshore, and seawater applications.

3. Lean Duplex (UNS S32101, S32304)

  - Lean Duplex 2101 (UNS S32101)

    - Composition: Approximately 21% chromium, 1.5% nickel, and 0.3% molybdenum.

    - Characteristics: Lower nickel content makes it more cost-effective while still offering good corrosion resistance and strength. Suitable for structural applications and storage tanks.

  - Duplex 2304 (UNS S32304)

    - Composition: Approximately 23% chromium, 4% nickel.

    - Characteristics: Good general corrosion resistance, particularly in environments with moderate chloride levels. Often used in heat exchangers and water treatment systems.

4. Hyper Duplex (UNS S32707, S33207)

  - Hyper Duplex 2707 (UNS S32707)

    - Composition: High chromium, molybdenum, and nitrogen content.

    - Characteristics: Superior pitting and crevice corrosion resistance, extremely high strength. Used in the most demanding applications involving high chloride levels and aggressive environments.

5. Other Specialized Duplex Grades

  - Zeron 100 (UNS S32760)

    - Composition: Approximately 25% chromium, 7% nickel, 3.5% molybdenum, with copper and tungsten.

    - Characteristics: Very high resistance to pitting, crevice corrosion, and stress corrosion cracking. Used in oil and gas, chemical processing, and marine industries.

  - Duplex 2202 (UNS S32202)

    - Composition: Lower nickel content compared to other duplex grades, with approximately 22% chromium, 2% nickel, and 0.2% molybdenum.

    - Characteristics: Cost-effective alternative with good corrosion resistance and strength, used in structural and architectural applications.

Benefits of Using Duplex Stainless Steels for Flanges

- Corrosion Resistance: Duplex stainless steels offer excellent resistance to various forms of corrosion, including pitting, crevice corrosion, and stress corrosion cracking, making them suitable for harsh environments.

- High Strength: The dual-phase microstructure provides high mechanical strength, allowing for the design of thinner, lighter components without compromising performance.

- Cost-Effectiveness: Certain grades like lean duplex offer a good balance between cost and performance, reducing material costs while still providing adequate corrosion resistance and strength.

- Versatility: Duplex stainless steels are versatile and can be used in a wide range of applications, including oil and gas, chemical processing, water treatment, and marine environments.

Applications of Duplex Flanges

- Oil and Gas Industry: Used in pipelines, pressure vessels, and offshore platforms due to their high strength and corrosion resistance.

- Chemical Processing: Suitable for handling aggressive chemicals and corrosive environments.

- Marine Industry: Ideal for seawater applications, including desalination plants, due to their excellent resistance to chloride-induced corrosion.

- Water Treatment: Used in various components of water treatment facilities where corrosion resistance is crucial.

- Structural Applications: Employed in construction and structural applications where both strength and resistance to environmental factors are important.


Duplex flanges are made from various grades of duplex stainless steels, each offering unique benefits in terms of corrosion resistance, strength, and cost-effectiveness. The choice of material depends on the specific requirements of the application, such as the level of corrosive exposure, mechanical load, and economic considerations. These materials ensure that duplex flanges provide reliable and long-lasting performance in challenging environments.

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