Flange Types
Duplex Flanges
Duplex and super duplex stainless steel flanges for offshore and chemical service.
Duplex stainless steel flanges are manufactured from a microstructure containing approximately equal proportions of austenite and ferrite phases. This dual-phase structure gives duplex grades roughly twice the yield strength of standard austenitic stainless steels (F304/F316) while providing significantly better resistance to chloride stress corrosion cracking and pitting. The most common duplex grade is UNS S31803/S32205 (commonly called 2205), forged per ASTM A182 F51.
Super duplex grades such as UNS S32750 (2507, ASTM A182 F53) and S32760 push corrosion resistance even further with higher chromium, molybdenum, and nitrogen content. The PREN (Pitting Resistance Equivalent Number) for 2507 super duplex exceeds 40, compared to approximately 34 for standard 2205 duplex and 25 for 316L. This makes super duplex the standard for critical offshore and subsea piping where chloride exposure is severe.
Flanges.AI stocks duplex and super duplex flanges in all standard types per ASME B16.5, sizes from 1/2" through 24", and pressure classes 150 through 2500. All duplex flanges are solution annealed and meet ferrite content requirements (typically 40-60% per ASTM A923). Impact testing per ASTM A182 supplementary requirements is available for low-temperature applications. Contact us for your duplex flange requirements.
