Duplex Stainless Steel Flanges

Duplex stainless steel flanges are widely used in industries where both high strength and corrosion resistance are required. Duplex stainless steel grades have a mixed microstructure of austenite and ferrite, which provides enhanced mechanical properties compared to conventional austenitic stainless steels like 304 and 316. Below are some common standards, material grades, and specifications for duplex stainless steel flanges:

1. Common Standards for Duplex Stainless Steel Flanges:

• ASTM A182: Standard for forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service.
• ASTM A240: Standard for chromium and chromium-nickel stainless steel plates, sheets, and strips for pressure vessels and general applications.
• ASME B16.5: Standard for pipe flanges and flanged fittings, covering sizes NPS ½ to NPS 24.
• ASME B16.47: Large diameter steel flanges, NPS 26 through NPS 60.
• EN 1092-1: European standard for flanges.
• API 605: Standard for large-diameter carbon steel flanges (similar to ASME B16.47).

2. Duplex Stainless Steel Grades:

• UNS S31803 (1.4462): Known as Duplex 2205, it’s one of the most commonly used duplex grades. Offers good pitting and crevice corrosion resistance, with a balanced austenite and ferrite structure.
• UNS S32205 (1.4462): Similar to S31803 but with slightly improved corrosion resistance, particularly in chloride-containing environments.
• UNS S32750 (1.4410): Super duplex stainless steel with a higher alloy content, offering better corrosion resistance and mechanical properties. Known as SAF 2507.
• UNS S32760 (1.4501): Another super duplex grade with even higher corrosion resistance, used in highly aggressive environments such as offshore and chemical processing.

3. Mechanical Properties:

Duplex stainless steel generally has higher tensile strength and yield strength than standard austenitic grades like 316L. The typical yield strength of duplex stainless steel is in the range of 450-550 MPa, and tensile strength can reach up to 700-800 MPa.

4. Specifications:

• Temperature Range: Duplex stainless steel flanges are suitable for use in environments ranging from cryogenic temperatures to about 300°C.
• Corrosion Resistance: The duplex microstructure provides excellent resistance to chloride stress corrosion cracking, pitting, and crevice corrosion. Super duplex grades are particularly suited for highly corrosive environments.
• Pressure Rating: Depending on the standard and class (such as ASME B16.5 Class 150, 300, 600, etc.), duplex flanges can withstand high pressures.

5. Common Applications:

• Oil and gas industry (especially offshore platforms)
• Chemical processing
• Seawater equipment
• Pulp and paper industry
• Heat exchangers and pressure vessels

These standards and specifications ensure that duplex stainless steel flanges provide the strength, corrosion resistance, and durability needed for demanding applications.