2507 (S32750) Super Duplex Stainless Steel Plate Prime Quality with 3.1 Test Certificate
 
Products Specification

Introduction to S32750 Super Duplex Stainless Steel

S32750 (commonly known as 2507) is a super duplex stainless steel belonging to the family of duplex (ferritic-austenitic) stainless steels. It is characterized by an exceptionally high strength and outstanding corrosion resistance, particularly in aggressive chloride-containing environments.

Key Characteristics

1. Dual-Phase Microstructure: S32750 consists of approximately 50% ferrite and 50% austenite. This balanced microstructure combines the benefits of both phases:

   • Ferrite: Provides high strength and resistance to stress corrosion cracking (SCC).

   • Austenite: Provides toughness and good weldability.

2. High Strength: Offers roughly twice the yield strength of standard austenitic stainless steels (like 316L) and many other duplex grades. Typical minimum yield strength is around 550 MPa (80 ksi).

3. Exceptional Corrosion Resistance:

   • Pitting & Crevice Corrosion: Features a very high Pitting Resistance Equivalent Number (PREN) typically > 40 (calculated as PREN = %Cr + 3.3x(%Mo + 0.5x%W) + 16x%N). This makes it highly resistant to pitting and crevice corrosion, surpassing grades like 316L, 2205 (standard duplex), and even 904L in many environments.

   • Stress Corrosion Cracking (SCC): Excellent resistance to chloride-induced SCC, a common failure mode for standard austenitics in warm chloride environments.

   • General Corrosion: Excellent resistance to a wide range of acids, alkalis, and other corrosive media.

4. Good Weldability: Generally weldable using appropriate procedures (matching or over-alloyed filler metals, controlled heat input) to maintain the corrosion resistance and phase balance in the weld zone.

5. Good Toughness and Ductility: While not matching the very high toughness of some austenitic grades at cryogenic temperatures, it offers good toughness for most demanding applications, especially considering its high strength.

Typical Chemical Composition (wt.%)

• Chromium (Cr): 24.0 - 26.0% (Provides excellent oxidation and general corrosion resistance)

• Nickel (Ni): 6.0 - 8.0% (Stabilizes austenite, improves toughness)

• Molybdenum (Mo): 3.0 - 4.0% (Significantly enhances pitting/crevice corrosion resistance)

• Nitrogen (N): 0.24 - 0.32% (Crucial for strengthening, stabilizing austenite, and boosting pitting resistance - key to the "super" duplex classification)

• Manganese (Mn): ≤ 1.2%

• Silicon (Si): ≤ 0.8%

• Phosphorus (P): ≤ 0.035%

• Sulfur (S): ≤ 0.020%

• Copper (Cu): ≤ 0.5%

• Tungsten (W): 0.5 - 1.0% (Further enhances pitting resistance and stability)

• Carbon (C): ≤ 0.030%

• Iron (Fe): Balance

Key Mechanical Properties (Typical, Annealed Condition)

• Tensile Strength (Rm): 800 - 1000 MPa (116 - 145 ksi)

• Yield Strength (Rp0.2): ≥ 550 MPa (≥ 80 ksi)

• Elongation (A5): ≥ 25%

• Hardness (HB): ≤ 290 (Brinell)

• Impact Toughness (Charpy V, RT): Typically > 100 J

Standards & Designations

• UNS: S32750

• EN / Euronorm: 1.4410 (X2CrNiMoN25-7-4)

• ASTM A182: F53 (Forgings), F55 (Castings - investment)

• ASTM A276/A479: UNS S32750

• ASTM A789/A790: UNS S32750 (Seamless/Welded Tubes/Pipe)

• Common Name: 2507

Typical Applications

S32750 is used in demanding environments where its combination of strength and corrosion resistance is essential:

• Oil & Gas Industry: Downhole components, pipelines (flowlines, risers), umbilicals, manifolds, valves, pumps, heat exchangers (seawater cooling), pressure vessels in subsea and topside applications.

• Chemical & Petrochemical Processing: Reactors, pressure vessels, columns, piping systems handling corrosive chemicals (acids, chlorides).

• Desalination & Water Treatment: Seawater reverse osmosis (SWRO) high-pressure piping, pumps, valves, evaporators.

• Marine & Offshore: Propeller shafts, seawater piping systems, fittings, fasteners, offshore platform components.

• Flue Gas Desulfurization (FGD): Absorber towers, ducts, dampers, chimney liners handling aggressive scrubber environments.

• Pulp & Paper Industry: Bleach plants, digesters.

• Heat Exchangers: Especially for cooling with seawater or brackish water.

• High-Strength Structural Components: Where weight savings or resistance to corrosive atmospheres is critical.

Advantages over Other Grades

• Higher Strength: Compared to 316L, 904L, 6Mo austenitics, and standard duplex 2205.

• Higher PREN/Better Localized Corrosion Resistance: Compared to 316L, 904L, 254 SMO (6Mo), and 2205. Competes closely with higher-nickel alloys in many chloride environments.

• Better SCC Resistance: Significantly better than 316L and other austenitics in chloride environments.

• Potentially Lower Cost: Compared to high-nickel alloys like Alloy 625 or super austenitics, offering a cost-effective solution for many applications requiring extreme corrosion resistance.

Important Considerations

• Heat Treatment: Requires solution annealing (typically 1020-1100°C followed by rapid quenching) to achieve the optimal duplex microstructure and corrosion resistance.

• Welding: Requires careful procedure qualification using matching (e.g., ER2594) or super duplex/over-matching filler metals (e.g., ER2595/NiCrMo-10) to avoid detrimental phases (sigma, chi) and maintain corrosion resistance. Control of heat input and interpass temperature is critical.

• Phase Balance: Maintaining the near 50/50 ferrite/austenite balance is crucial for performance. Improper heat treatment or welding can skew this balance and degrade properties.

Summary

S32750 (2507) super duplex stainless steel is a premium material offering an outstanding combination of very high strength, excellent corrosion resistance (especially to pitting, crevice, and SCC in chloride environments), and good toughness. Its high PREN (>40) places it among the most corrosion-resistant stainless steels available. It is a cost-effective alternative to high-nickel alloys in many demanding applications within the oil & gas, chemical processing, desalination, marine, and offshore industries, where both strength and resistance to aggressive media are paramount.