2507 (S32750) Super Duplex Stainless Steel Coil Tube
Product Overview
The 2507 (UNS S32750) Super Duplex Stainless Steel Coil Tube is a high-performance austenitic-ferritic alloy engineered for the most demanding corrosion environments in the global energy, marine, and chemical processing industries. Supplied in continuous coil form, this product enables efficient downstream processing—including cold drawing, cold forming, and welding—while maintaining the exceptional mechanical and corrosion resistance properties inherent to the super duplex steel family. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube represents the pinnacle of stainless steel metallurgical engineering, combining a PREN (Pitting Resistance Equivalent Number) exceeding 40 with yield strengths approximately double those of conventional austenitic grades such as 316L.
As a super duplex grade, 2507 occupies a distinct position within the duplex stainless steel hierarchy, offering superior resistance to pitting corrosion (Pitting Corrosion), crevice corrosion (Crevice Corrosion), chloride stress corrosion cracking (Chloride-Induced Stress Corrosion Cracking, Cl-SCC), and general uniform corrosion compared to standard duplex grades such as 2205 (UNS S31803).
Material & Properties
The 2507 (S32750) super duplex stainless steel coil tube is characterized by a balanced microstructure consisting of approximately 50% austenite and 50% ferrite, which confers a unique combination of mechanical strength, toughness, and corrosion resistance.
Chemical Composition (Weight Percent)
| Element | Minimum | Maximum | Typical |
|---|---|---|---|
| Carbon (C) | — | 0.030 | 0.020 |
| Manganese (Mn) | — | 2.00 | 1.50 |
| Silicon (Si) | — | 1.00 | 0.60 |
| Chromium (Cr) | 22.0 | 25.0 | 24.0 |
| Nickel (Ni) | 6.0 | 8.0 | 7.0 |
| Molybdenum (Mo) | 3.0 | 4.0 | 3.8 |
| Nitrogen (N) | 0.24 | 0.32 | 0.28 |
| Copper (Cu) | 0.5 | 1.0 | 0.7 |
| Tungsten (W) | — | 0.30 | — |
Mechanical Properties (Solution Annealed Condition)
| Property | Specification |
|---|---|
| Tensile Strength (UTS) | ≥ 795 MPa (≥ 115 ksi) |
| Yield Strength (0.2% Offset) | ≥ 550 MPa (≥ 80 ksi) |
| Elongation (A50mm) | ≥ 15% |
| Hardness (HBW) | ≤ 340 |
| Pitting Resistance Equivalent Number (PREN) | > 40 |
Corrosion Resistance Characteristics
- Pitting Resistance: PREN > 40, representing the highest tier among commercial duplex stainless steels, providing outstanding resistance in chloride-rich environments.
- Crevice Corrosion Resistance: Superior to 316L and standard 2205 duplex in aggressive chloride solutions, particularly at elevated temperatures.
- Stress Corrosion Cracking (SCC) Resistance: Excellent resistance to chloride-induced SCC, making it suitable for hot chloride service where austenitic grades fail.
- Acid Resistance: Demonstrates good performance in dilute sulfuric acid (H₂SO₄), hydrochloric acid (HCl), and mixed acid environments.
- Temperature Range: Optimal service temperature from cryogenic conditions up to 300°C (572°F); above 300°C, intermetallic phase precipitation (σ-phase, Laves phase) may occur.
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | 2507 / UNS S32750 / EN 1.4410 / 0.4410 / ZCDUN25-7-4 / SDSS 2507 |
| Product Form | Coil Tube (Continuous Coil / Spooled Tubing) |
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (typical coil tube range) |
| Wall Thickness | 0.3 mm – 2.0 mm |
| Coil Length | Customized; typically 500 m – 3,000 m per coil |
| Coil Inner Diameter | 300 mm – 600 mm |
| Surface Finish | 2B (Cold Rolled & Annealed), BA (Bright Annealed), No. 4, Mirror (upon request) |
| Delivery Condition | Solution Annealed (Solution Heat Treated), typically 1050–1100°C followed by rapid quenching |
| Applicable Standards | ASTM A790 / A790M, EN 10217-7, ISO 2862, NACE MR0175 / ISO 15156 |
| Welding Suitability | Excellent (TIG/GTAW, MIG/GMAW, resistance welding); no preheating required |
| Heat Treatment | Solution annealing: 1050–1100°C, water or air quench; no aging treatment recommended |
Manufacturing Process
The production of 2507 (S32750) super duplex stainless steel coil tube follows a rigorous multi-stage manufacturing sequence designed to ensure consistent metallurgical quality, dimensional accuracy, and surface integrity:
- Raw Material Selection: High-purity vacuum arc remelted (VAR) or electro-slag remelted (ESR) ingots are selected to ensure low interstitial element content (C, N, S) and freedom from macro-segregation.
- Hot Rolling: Billets are reheated to 1150–1250°C and hot-rolled into strip stock with controlled reduction ratios to achieve uniform grain structure and minimize centerline segregation.
- Pickle and Scale Removal: Hot-rolled strip undergoes acid pickling (HNO₃/HF blend) to remove oxide scale, followed by thorough rinsing and drying to prevent intergranular corrosion initiation.
- Cold Rolling: Cold-rolled to target wall thickness with cumulative reductions of up to 85–90%, achieving precise dimensional tolerances (±0.05 mm on wall thickness) and a controlled surface finish.
- Intermediate Annealing: Periodic annealing treatments are performed during multi-pass cold rolling to relieve accumulated cold work, prevent cracking, and maintain ductility.
- Solution Annealing (Final Heat Treatment): The coil tube is solution-annealed at 1050–1100°C with rapid quenching (water quench or high-velocity air quench) to dissolve carbides and intermetallic phases, restoring the equilibrium 50/50 austenite-ferrite microstructure.
- Coiling and Spooling: The finished tube is wound onto precision-machined spools with controlled tension to prevent wrinkling, deformation, or surface damage.
- Quality Inspection: Every coil undergoes 100% inline inspection including ultrasonic testing (UT), eddy current testing (ECT), optical surface inspection, dimensional verification, and periodic chemical analysis (spectrometry) and mechanical testing.
Applications
The exceptional combination of high PREN (>40), elevated mechanical strength, and superior chloride corrosion resistance renders 2507 (S32750) super duplex stainless steel coil tube ideal for the following critical applications:
Deep-Sea Oil & Gas Riser Systems (Deepwater Riser Applications)
- Subsea riser tubes and flowline connections operating at depths exceeding 2,000 m, where high hydrostatic pressure, low temperature, and aggressive chloride-laden seawater create extreme service conditions.
- Wellhead Christmas trees, subsea production manifolds, and umbilical systems.
- Compliant riser internal connectors and tensioner systems.
High-Concentration Chloride Environments (High-Chloride Service)
- Brine concentration systems and evaporator tubes in desalination plants (Multi-Stage Flash, MSF, and Reverse Osmosis pretreatment).
- Chlor-alkali plant process piping, brine handling systems, and chlorine dioxide generation equipment.
- Seawater cooling systems, heat exchanger tubes, and pump components in coastal industrial facilities.
- Chemical processing equipment handling concentrated hydrochloric acid (HCl) and mixed chloride-acid solutions.
Flue Gas Desulfurization Systems (FGD — Flue Gas Desulfurization)
- Absorber tower internals, demister supports, and spray nozzles in forced oxidation (FOROX) and limestone-gypsum FGD systems.
- Wet scrubber internals exposed to acidic mist containing SO₂, SO₃, HCl, and HNO₃.
- Catalytic converter inlet/outlet ducting in sulfuric acid manufacturing and waste acid regeneration plants.
Additional Industrial Applications
- Offshore platform structural components, deck loading systems, and mooring hardware.
- Nuclear waste storage containers and radioactive waste transport casks.
- Oil and gas subsea umbilical jackets and flexible pipe armor wire.
- Bioreactor vessels and pharmaceutical processing equipment requiring high purity and corrosion resistance.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and compliance accreditations for its 2507 (S32750) super duplex stainless steel coil tube products:
Management System Certifications
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health and Safety Management Systems
- ISO/TS 22163:2014 — Automotive Industry Quality Management (where applicable)
Industry-Specific Certifications
- NACE MR0175 / ISO 15156 — Materials for Use in H₂S-Containing Environments in Oil and Gas Production
- API 5CT / API 5L — Compliance for oil and gas industry applications
- DNV-GL — Marine and Offshore Engineering certification
- ABS (American Bureau of Shipping) — Marine classification approval
- LR (Lloyd's Register) — Marine classification approval
- CE Marking (PED 2014/68/EU) — Pressure Equipment Directive compliance
Material Testing & Traceability
- Mill Test Certificates (MTC): Full EN 10204 3.1 certification provided for every coil, including chemical composition, mechanical properties, and heat treatment records.
- Heat Number Traceability: Complete lot-by-lot traceability from raw material ingot through final coil delivery.
- Non-Destructive Testing (NDT): 100% ultrasonic testing (UT) and eddy current testing (ECT) for internal and surface defect detection.
- Corrosion Testing: Third-party validated testing including ASTM G48 (pitting and crevice corrosion), ASTM G150 (PREN verification), ASTM G5 (immersion testing), and ASTM G36 (stress corrosion cracking).
- Mechanical Testing: Tensile testing (ASTM A370), impact testing (ASTM E23, Charpy V-Notch), and hardness testing (ASTM E10) performed at certified laboratories.
Unique Selling Points
- Highest PREN in Commercial Duplex Steels: With a Pitting Resistance Equivalent Number exceeding 40, 2507 offers the most robust chloride corrosion resistance available in the duplex stainless steel family—surpassing 2205 (PREN ~34–38) and significantly outperforming 316L (PREN ~24–26).
- Exceptional Strength-to-Weight Ratio: Yield strength of ≥550 MPa allows for thinner wall designs compared to 316L (yield strength ~170 MPa), reducing overall weight and material costs while maintaining structural integrity.
- Coil Form Advantage: Continuous coil supply enables high-efficiency downstream processing—eliminating the need for butt-welding multiple straight lengths, reducing labor costs, and ensuring metallurgical homogeneity along the entire coil length.
- Weldability Without Preheating: Unlike many high-alloy steels, 2507 maintains excellent weldability in the solution-annealed condition, requiring no preheating and no post-weld heat treatment for most applications—reducing fabrication complexity and cost.
- Cryogenic to Moderate Temperature Versatility: Retains full mechanical properties from cryogenic temperatures (−196°C / −320°F) up to 300°C, enabling use in LNG (Liquefied Natural Gas) systems and deepwater applications.
- Comprehensive Global Certification Portfolio: NACE MR0175, DNV-GL, API, and PED compliance ensures immediate acceptance across oil & gas, marine, and pressure vessel industries worldwide.
Conclusion
The 2507 (S32750) Super Duplex Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd represents a premier material solution for engineers and designers facing the most aggressive corrosion environments in offshore energy, chemical processing, and environmental protection industries. Its unparalleled combination of PREN > 40, high mechanical strength, excellent weldability, and coil-form processability makes it the material of choice for deep-sea riser systems, high-concentration chloride service