UNS S32750 Super Duplex 2507 Stainless Steel: Properties and Applications

What Is UNS S32750

UNS S32750, also known as super duplex 2507 and equivalent to EN 1.4410, is a super duplex stainless steel with a balanced ferritic-austenitic microstructure of approximately 50 percent each phase. Its high chromium, molybdenum, and nitrogen contents give a pitting resistance equivalent number above 40, providing exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride environments.

Chemical Composition

Limits are carbon 0.030 percent maximum, chromium 24.0 to 26.0 percent, nickel 6.0 to 8.0 percent, molybdenum 3.0 to 4.5 percent, nitrogen 0.24 to 0.32 percent, manganese 1.20 percent maximum, silicon 0.80 percent maximum, phosphorus 0.035 percent, and sulfur 0.020 percent.

Mechanical Properties

In the solution-annealed condition the material has a yield strength of at least 550 MPa, a tensile strength of 750 to 1000 MPa, elongation of at least 25 percent, hardness up to 300 HB or 32 HRC, and impact toughness of at least 45 J at minus 46 degrees C. Density is 7.8 to 7.9 g per cubic centimeter and thermal conductivity about 13.5 W per meter per Kelvin.

Strength Advantages

Super duplex 2507 offers roughly twice the yield strength of common 300-series austenitic stainless steels and about 20 percent more than duplex 2205, around 550 MPa versus 450 MPa. This enables thinner wall sections, lighter constructions, and improved safety factors for pressure equipment and structural components.

Corrosion Resistance

With PREN above 40, S32750 resists pitting and crevice corrosion in hot seawater, concentrated brine, and other aggressive chloride media where standard duplex and austenitic grades fail. It also provides high resistance to erosion-corrosion in high-velocity flow and good toughness at sub-zero temperatures.

Applications

S32750 is used in offshore platforms and subsea equipment, chemical processing vessels and heat exchangers, seawater desalination plants, flue gas desulfurization systems, pulp and paper digesters, and oil and gas downhole and process equipment in sour service.

Frequently Asked Questions

Q: What is the yield strength of S32750?

A: 550 MPa minimum.

Q: What is the PREN of S32750?

A: Above 40.

Q: How does 2507 compare with 2205?

A: Higher chromium, molybdenum, and nitrogen, with about 20 percent higher yield strength.

Q: What is the impact energy at minus 46 degrees C?

A: 45 J minimum.

Q: What applications use S32750?

A: Offshore, desalination, chemical, and sour oil and gas service.

Q: Is S32750 heat treatable?

A: No, it is supplied solution annealed and is not hardenable by heat treatment.

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