Key Technical Metrics & Core Attributes
Provides double the mechanical yield strength compared to standard austenitic grades like 316L.
High proof stress allows significant wall thickness reduction and lighter structural piping designs.
Pitting Resistance Equivalent Number guarantees immunity to localized pitting and crevice corrosion.
Universal super duplex standard for severe sour service, offshore oilfield, and chemical handling.
Comprehensive Material Overview: ASTM A815 WPS UNS S32750 Super Duplex Elbows
ASTM A815 WPS UNS S32750 represents the supreme benchmark for wrought ferritic/austenitic super duplex stainless steel piping fittings. Engineered specifically to meet the grueling demands of extreme marine, petrochemical, subsea, and aggressive chemical processing environments, UNS S32750 (commonly known as 2507 Super Duplex or EN 1.4410) offers a balanced 50/50 dual-phase microstructure consisting of roughly equal proportions of austenite and ferrite. This synergistic metallurgical design grants the material exceptionally high mechanical yield strength—nearly double that of conventional austenitic grades such as 316L or 317L—alongside virtually complete immunity to chloride-induced stress corrosion cracking (SCC).
The designation WPS in ASTM A815 indicates wrought grade seamless piping fittings manufactured to strict ASME B16.9 and MSS SP-43 requirements. These elbows, available in both Long Radius (LR, R=1.5D) and Short Radius (SR, R=1.0D) configurations, serve as crucial flow-direction altering components in high-pressure piping networks. Whether utilized in deepwater offshore oil rigs, reverse osmosis seawater desalination plants, aggressive sour gas scrubbers, or high-purity chemical reactors, ASTM A815 WPS UNS S32750 elbows perform reliably under extreme mechanical fatigue, thermal shocks, and highly oxidizing corrosive media.
Key Material Classifications Covered by Specification ASTM A815:
- Class WP-S: Wrought seamless fittings manufactured from seamless pipe, tube, or wrought stock.
- Class WP-W: Wrought fittings containing welds where the filler metal has been added and non-destructively inspected via radiography (RT).
- Class WP-WX: Wrought welded fittings where all welds are 100% radiographed per ASME Boiler and Pressure Vessel Code.
- Class WP-WU: Wrought fittings where all welds are 100% examined using ultrasonic testing (UT).
Chemical Composition Limits (%) — UNS S32750 vs Duplex Family
Strict elemental control ensures maximum corrosion resistance, prevention of harmful intermetallic phase precipitation (such as Sigma σ and Chi χ phases), and structural integrity.
| Grade / UNS | Carbon (C) | Cr | Ni | Mo | N | Cu | Mn (Max) | Si (Max) | P / S (Max) |
|---|---|---|---|---|---|---|---|---|---|
| WPS S32750 (2507) | ≤ 0.030 | 24.0 – 26.0 | 6.0 – 8.0 | 3.0 – 5.0 | 0.24 – 0.32 | ≤ 0.50 | 1.20 | 0.80 | 0.035 / 0.020 |
| WPS S31803 (2205) | ≤ 0.030 | 21.0 – 23.0 | 4.5 – 6.5 | 2.5 – 3.5 | 0.08 – 0.20 | — | 2.00 | 1.00 | 0.030 / 0.020 |
| WPS S32202 (2202) | ≤ 0.030 | 21.5 – 24.0 | 1.0 – 2.8 | 0.45 max | 0.18 – 0.26 | — | 2.00 | 1.00 | 0.040 / 0.010 |
| WPS S32760 (Zeron 100) | ≤ 0.030 | 24.0 – 26.0 | 6.0 – 8.0 | 3.0 – 4.0 | 0.20 – 0.30 | 0.50 – 1.00 | 1.00 | 1.00 | 0.030 / 0.010 |
* Note: UNS S32750 contains deliberate additions of Nitrogen (0.24–0.32%) to significantly boost pitting resistance, promote rapid intergranular re-austenitization during heat treatment, and increase mechanical yield strength.
Mechanical & Structural Performance Data
The unique balance between ferrite and austenite phases endows UNS S32750 elbows with exceptional tensile strength, severe impact toughness down to sub-zero temperatures (-50°C), and remarkably high resistance to mechanical erosion-corrosion. When compared to standard 300 series stainless steel or conventional lean duplex alloys, S32750 permits engineers to specify thinner wall schedules (e.g., SCH 10S vs SCH 40S) without sacrificing structural safety margins.
Higher allowable design stress under ASME B31.3 piping codes allows up to 40% reduction in overall system weight for high-pressure offshore topsides.
ASTM A815 S32750 Mechanical Limits
| Mechanical Parameter | ASTM A815 Standard Limit |
|---|---|
| Tensile Strength, min (MPa / ksi) | 800 – 965 / [116 – 140] |
| Yield Strength (0.2% offset), min | 550 MPa / [80 ksi] |
| Elongation in 2 in. (50 mm), min % | 15.0 % |
| Hardness, Brinell (HBW), max | 310 HBW max |
| Hardness, Rockwell C (HRC), max | 32 HRC max |
| Charpy V-Notch Impact Energy (-40°C) | ≥ 80 Joules (Average) |
Corrosion Resistance Physics & PREN Formula Calculations
The exceptional pitting and crevice corrosion performance of Super Duplex UNS S32750 is directly quantified using the Pitting Resistance Equivalent Number (PREN). Higher PREN numbers denote significantly greater resistance against localized passive film breakdown in hostile chloride-rich environments such as ocean water, acids, and brines.
Pitting & Crevice Corrosion
With a minimum PREN of 42, S32750 elbows remain completely impervious to pitting corrosion in chlorinated seawater systems even under elevated temperature conditions up to 45°C.
Stress Corrosion Cracking (SCC)
Austenitic steels (like 304L / 316L) are vulnerable to chloride SCC above 60°C. S32750’s duplex structure resists SCC in environments with extremely high H2S and chloride ions.
Erosion-Corrosion
High material hardness combined with superior dynamic passive film regeneration grants UNS S32750 elbows exceptional resistance to sand slurry erosion in subsea manifolds.
Long Radius (LR) vs Short Radius (SR) Duplex Elbows
Selecting between Long Radius (R = 1.5D) and Short Radius (R = 1.0D) depends on hydraulic head loss limitations, fluid velocity, pigging requirements, and space constraints.
Long Radius (LR) Elbow (R = 1.5D)
- Center-to-End Distance: 1.5 times the nominal pipe diameter (A = 1.5 × NPS).
- Frictional Head Loss: Minimal fluid turbulence and low pressure drop across the bend.
- Pigging Capability: Ideal for pipeline systems requiring intelligent inline inspection pigging.
- Erosion Resistance: Lower flow impingement velocity reduces wall thinning inside the extrados.
- Primary Applications: Long-distance cross-country oil pipelines, offshore subsea risers, process chemical lines.
Short Radius (SR) Elbow (R = 1.0D)
- Center-to-End Distance: Equal to the nominal pipe diameter (A = 1.0 × NPS).
- Frictional Head Loss: Higher directional change resistance and slightly elevated turbulence.
- Pigging Capability: Not suitable for standard rigid intelligent pigging operations.
- Compact Layout: Used where tight physical clearance prevents the installation of LR elbows.
- Primary Applications: Subsea skid packages, compact FPSO topside modules, marine engine rooms, skid systems.
ASME B16.9 90° Long Radius (LR) Elbow Dimensions & Weight Chart
Comprehensive dimensional guide for ASTM A815 WPS UNS S32750 Butt Weld 90-Degree LR Elbows (1/2″ to 24″).
| Nominal Size (NPS) | Outside Diameter (OD) [mm] | Center to End (A) [mm] | Wall Thickness (SCH 10S) [mm] | Wall Thickness (SCH 40S) [mm] | Wall Thickness (SCH 80S) [mm] | Approx. Weight (SCH 40S) [kg] |
|---|---|---|---|---|---|---|
| 1/2″ (DN15) | 21.3 | 38.0 | 2.11 | 2.77 | 3.73 | 0.08 |
| 3/4″ (DN20) | 26.7 | 38.0 | 2.11 | 2.87 | 3.91 | 0.11 |
| 1″ (DN25) | 33.4 | 38.0 | 2.77 | 3.38 | 4.55 | 0.16 |
| 1-1/2″ (DN40) | 48.3 | 57.0 | 2.77 | 3.68 | 5.08 | 0.42 |
| 2″ (DN50) | 60.3 | 76.0 | 2.77 | 3.91 | 5.54 | 0.78 |
| 3″ (DN80) | 88.9 | 114.0 | 3.05 | 5.49 | 7.62 | 2.15 |
| 4″ (DN100) | 114.3 | 152.0 | 3.05 | 6.02 | 8.56 | 4.12 |
| 6″ (DN150) | 168.3 | 229.0 | 3.40 | 7.11 | 10.97 | 11.20 |
| 8″ (DN200) | 219.1 | 305.0 | 3.76 | 8.18 | 12.70 | 23.50 |
| 10″ (DN250) | 273.0 | 381.0 | 4.19 | 9.27 | 12.70 | 41.80 |
| 12″ (DN300) | 323.8 | 457.0 | 4.57 | 9.52 | 12.70 | 64.50 |
ASME B16.9 / MSS SP-43 90° Short Radius (SR) Elbow Dimensions
Dimensions and weights for compact radius Super Duplex 2507 elbows (R = 1.0D).
| NPS Size | Outside Diameter (OD) [mm] | Center-to-End SR (A) [mm] | SCH 10S Wall [mm] | SCH 40S Wall [mm] | Approx. Weight (SCH 80S) [kg] |
|---|---|---|---|---|---|
| 1″ (DN25) | 33.4 | 25.4 | 2.77 | 3.38 | 0.14 |
| 1-1/2″ (DN40) | 48.3 | 38.1 | 2.77 | 3.68 | 0.35 |
| 2″ (DN50) | 60.3 | 50.8 | 2.77 | 3.91 | 0.65 |
| 3″ (DN80) | 88.9 | 76.2 | 3.05 | 5.49 | 1.80 |
| 4″ (DN100) | 114.3 | 101.6 | 3.05 | 6.02 | 3.40 |
| 6″ (DN150) | 168.3 | 152.4 | 3.40 | 7.11 | 9.80 |
| 8″ (DN200) | 219.1 | 203.2 | 3.76 | 8.18 | 19.50 |
Critical Heat Treatment & Microstructural Phase Balance
The physical properties and corrosion resistance of ASTM A815 WPS UNS S32750 elbows depend heavily on achieving a balanced 40%–60% Ferrite / 60%–40% Austenite phase ratio. Improper thermal treatment can trigger dangerous intermetallic precipitation, specifically the embrittling Sigma Phase (σ) and Chi Phase (χ), which rapidly destroy impact toughness and pitting resistance in acidic environments.
| Grade / ASTM | Solution Annealing Temperature | Cooling / Quenching Method | Target Ferrite Content |
|---|---|---|---|
| WPS S32750 (2507) | 1025°C – 1125°C [1920°F – 2060°F] | Rapid Water Quench (below 300°C within seconds) | 40% – 60% Ferrite (E562 Point Count) |
| WPS S31803 (2205) | 1020°C – 1100°C [1870°F – 2010°F] | Water Quench or Rapid Air Cool | 40% – 60% Ferrite |
| WPS S32202 (2202) | 1020°C – 1080°C [1870°F – 1975°F] | Water Quench or Forced Air Quench | 45% – 55% Ferrite |
Quenching Rate Importance: Slow cooling between 600°C and 1000°C allows chromium and molybdenum to segregate rapidly, causing intermetallic phase formation in less than two minutes. Water quenching ensures that elements remain in solid solution, preserving optimal toughness down to -50°C.
Manufacturing Workflows for Seamless & Welded Elbows
Combining hot mandrel bending, cold hydraulic pushing, precision beveling, and non-destructive testing for flaw-free super duplex fittings.
Hot Mandrel Forming
Seamless pipe stock is heated via induction coils and pushed over a horn-shaped mandrel die to achieve accurate bend radius, wall uniformity, and roundness.
Plate Pressing & Welding
For large-diameter fittings (>24″), super duplex plates (ASTM A240 UNS S32750) are pressed into half-shells, bevelled, and welded using matching ER2594 filler metal.
Full Solution Annealing
Formed elbows undergo full solution annealing at 1100°C followed by high-volume water jet quenching to eliminate internal stress and restore the 50/50 phase balance.
Beveling & Surface Pickling
Elbow ends are CNC-machined into standard ASME B16.25 welding bevels. Entire outer and inner surfaces are acid pickled and passivated for pristine surface purity.
Welding Specification & Consumables Guidelines for S32750
Welding ASTM A815 WPS S32750 elbows requires strict heat input control to avoid both excessive ferrite formation in the Heat-Affected Zone (HAZ) (caused by cooling too rapidly) and intermetallic phase precipitation (caused by excessive heat input).
| Welding Process | AWS Filler Metal Specification | Recommended Heat Input | Shielding / Backing Gas |
|---|---|---|---|
| GTAW (TIG) | AWS A5.9 ER2594 (Over-alloyed Ni ~ 9%) | 0.2 – 1.5 kJ/mm | Pure Ar or Ar + 2% N2 / Ar + 30% He + 2% N2 |
| SMAW (Stick) | AWS A5.4 E2594-16 / E2594-17 | 0.5 – 1.5 kJ/mm | N/A (Flux coated) |
| GMAW (MIG) | AWS A5.9 ER2594 Wire | 0.5 – 1.2 kJ/mm | Ar + 2% N2 or Ar + 30% He + 2% N2 |
| SAW (Submerged Arc) | AWS A5.9 ER2594 Wire + Basic Flux | 0.8 – 1.8 kJ/mm | Neutral / Basic Welding Flux |
Maximum interpass temperature must be strictly limited to 100°C (212°F) during all pass sequences to prevent precipitation of secondary austenite and embrittling phases.
Quality Control & Testing Protocols
Every ASTM A815 WPS UNS S32750 elbow undergoes comprehensive non-destructive and destructive testing prior to release.
1. PMI Testing
100% Positive Material Identification (PMI) using X-ray fluorescence (XRF) or OES spectrometry to verify Cr, Ni, Mo, and N content.
2. Corrosion Testing
ASTM G48 Method A ferric chloride pitting corrosion test performed at 50°C for 24 hours (zero weight loss requirement).
3. Microstructure & Ferrite
Metallographic examination per ASTM E562 to ensure 40%–60% ferrite fraction and zero harmful intermetallic phase precipitates.
4. Radiographic (RT) / UT
Class WP-W and WP-WX fittings undergo 100% Radiographic Examination (RT) on all welded seams per ASME Section VIII.
International Standards & Equivalent Designations Matrix
| Standard Organization | Standard Code | Description / Fitting Type |
|---|---|---|
| ASTM Standard | ASTM A815 / A815M | Standard Specification for Wrought Ferritic, Ferritic/Austenitic, and Martensitic Stainless Steel Piping Fittings |
| ASME Standard | ASME B16.9 | Factory-Made Wrought Buttwelding Fittings (NPS 1/2 through NPS 48) |
| MSS Standard | MSS SP-43 | Wrought and Fabricated Butt-Welding Fittings for Low Pressure, Corrosion Resistant Applications |
| MSS Standard | MSS SP-97 | Integrally Reinforced Forged Branch Outlet Fittings — Socket Welding, Threaded, and Buttwelding Ends |
| European Norm | EN 10253-4 / EN 10088-3 | Butt-welding pipe fittings – Wrought austenitic and austenitic-ferritic (duplex) stainless steels |
| NACE Standard | NACE MR0175 / ISO 15156 | Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production |
Key Industrial Applications for Super Duplex S32750 Elbows
Proven track record in high-stress, highly aggressive corrosive industrial environments globally.
Offshore Oil & Gas Topsides
Extensively utilized in subsea manifolds, Christmas trees, flowlines, risers, and high-pressure firewater systems where salt spray and sour oil/gas require immunity to pitting and stress corrosion cracking.
Seawater Desalination Plants
Standard choice for high-pressure Reverse Osmosis (RO) pump manifolds, brine discharge headers, and energy recovery systems handling concentrated saline solutions at extreme velocities.
Chemical Processing & Acid Plants
Crucial for heat exchangers, reboilers, organic and inorganic acid piping networks (such as nitric, phosphoric, and organic acids) where standard austenitic alloys suffer rapid wall degradation.
Dimensional Tolerances per ASME B16.9 / MSS SP-43
| Nominal Pipe Size (NPS) | Off Angle Tolerance (Q) | Off Plane Tolerance (P) | Center-to-End Tolerance | Inside Diameter at End |
|---|---|---|---|---|
| 1/2″ to 2-1/2″ | ± 1 mm | ± 2 mm | ± 2.0 mm | +0.8 mm / -0.8 mm |
| 3″ to 3-1/2″ | ± 2 mm | ± 3 mm | ± 2.0 mm | +1.6 mm / -1.6 mm |
| 4″ | ± 2 mm | ± 3 mm | ± 2.0 mm | +1.6 mm / -1.6 mm |
| 5″ to 8″ | ± 3 mm | ± 5 mm | ± 2.0 mm | +1.6 mm / -1.6 mm |
| 10″ to 18″ | ± 4 mm | ± 6 mm | ± 3.0 mm | +3.2 mm / -1.6 mm |
| 20″ to 24″ | ± 5 mm | ± 10 mm | ± 3.0 mm | +4.8 mm / -1.6 mm |
Export Packaging, Product Marking & Quality Certification
To guarantee zero contamination and physical protection during international ocean freight transport, all ASTM A815 WPS UNS S32750 elbows adhere to strict export packing and clear hard-stamping traceability guidelines.
Standard Marking Specification
Continuous die-stamped marking on each elbow includes: Manufacturer Name/Logo, Standard Code (ASTM A815 WPS S32750), Pipe Size, Wall Thickness/Schedule, Heat Number for 100% mill traceability.
Seaworthy Fumigation-Free Wooden Cases
Fittings are protected with end plastic caps, individually wrapped in moisture-proof plastic film, and packed into heavy-duty fumigation-free plywood boxes with steel strap reinforcement.
EN 10204 3.1 & 3.2 Mill Certificates
Supplied with certified Material Test Reports (MTR) according to EN 10204 3.1. Independent third-party inspection (TPI by Lloyd’s Register, Bureau Veritas, SGS, or TÜV) available upon request.
Procurement Quick Reference
ASTM A815 WPS UNS S32750 Super Duplex Elbow Data Card
Instant technical lookup for engineers, procurement officers, and piping designers.
You must be logged in to post a comment.