Super Duplex Stainless Steel 2507 (S32750) Coil Tube
Product Overview
The Super Duplex Stainless Steel 2507 (UNS S32750) Coil Tube is a premium-grade austenitic-ferritic stainless steel product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. As a next-generation super duplex alloy, 2507 represents the pinnacle of corrosion-resistant stainless steel technology, offering exceptional resistance to chloride-induced stress corrosion cracking (SCC), pitting corrosion, and crevice corrosion. This product is supplied in continuous coil form, providing maximum processing flexibility for downstream fabricators and end users across demanding industrial sectors.
With a Pitting Resistance Equivalent Number (PREN) exceeding 40, the 2507 grade outperforms conventional 300-series austenitic stainless steels (304, 316, 317L) by a significant margin, while also surpassing standard duplex grades such as 2205 (S31803/S32205). This coil tube product is engineered for the most aggressive chemical and marine environments encountered in modern industrial operations.
Material & Properties
Chemical Composition (wt%)
| Element | Minimum | Maximum |
|---|---|---|
| Carbon (C) | — | 0.030 |
| Chromium (Cr) | 24.0 | 26.0 |
| Nickel (Ni) | 6.0 | 8.0 |
| Molybdenum (Mo) | 3.0 | 4.0 |
| Nitrogen (N) | 0.24 | 0.32 |
| Iron (Fe) | Balance | |
| Equivalent Notation | Cr25-Ni7-Mo4-N0.28 | |
Mechanical Properties (Annealed Condition)
| Property | Specification |
|---|---|
| Tensile Strength (Rm) | ≥ 800 MPa (116 ksi) |
| Yield Strength (Rp0.2) | ≥ 550 MPa (79.8 ksi) |
| Elongation (A5) | ≥ 15% |
| Hardness (HBW) | ≤ 325 |
Corrosion Resistance
- Pitting Resistance Equivalent Number (PREN): > 40 (calculated as %Cr + 3.3×%Mo + 16×%N)
- Intergranular Corrosion Resistance: Superior, even after prolonged exposure to sensitizing temperatures
- Stress Corrosion Cracking (SCC) Resistance: Excellent in hot chloride-containing solutions up to 60°C
- Cavitation and Erosion-Corrosion Resistance: Significantly improved over 316L and 2205 grades
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (Continuous Coiled Length) |
| Material Grade | 2507 / S32750 / UNS S32750 |
| Classification | Super Duplex Stainless Steel (Austenitic-Ferritic) |
| Applicable Standards | ASTM A790/A790M, EN 10216-5, NACE MR0175/ISO 15156 |
| PREN | > 40 |
| Maximum Service Temperature | 300°C (572°F) |
| Maximum Chloride Concentration (25°C) | > 50,000 ppm |
| Surface Finish | Pickled & Passivated (2B), or as specified |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
Manufacturing Process
The production of 2507 Super Duplex Stainless Steel Coil Tubes follows a rigorously controlled multi-stage manufacturing sequence designed to ensure metallurgical integrity, dimensional accuracy, and superior surface quality:
- Raw Material Selection: Vacuum Arc Remelting (VAR) or Electro-Slag Remelting (ESR) ingots are sourced to ensure ultra-low impurity levels (S, P < 0.015% each).
- Hot Rolling: Billets are reheated and hot-rolled into semi-finished coil stock at temperatures above 1100°C to establish the initial austenite-ferrite dual-phase microstructure.
- Hot Forming / Extrusion: The semi-finished coil is formed into tube blanks through seamless extrusion or hot-rolled and welded (ERW/ODW) processes, depending on the final wall thickness and diameter requirements.
- Solution Annealing: Tubes are solution-annealed at 1050–1100°C followed by rapid water quenching to homogenize the microstructure and achieve an optimal austenite (≈45-55%) to ferrite (≈45-55%) phase balance.
- Pickling & Passivation: Acid pickling removes oxide scales, followed by passivation treatment to restore the protective chromium oxide passive film.
- Coiling: Finished tubes are wound onto precision coils with controlled tension to prevent deformation or surface damage.
- Final Inspection: Each coil undergoes 100% non-destructive testing (NDT) including eddy current (ET) and ultrasonic testing (UT), supplemented by hydrostatic pressure testing per ASTM A790.
Applications
The 2507 Super Duplex Coil Tube is purpose-engineered for the most corrosive and high-integrity industrial applications:
- Deep-Sea Oil & Gas Riser Systems: The high yield strength (≥550 MPa) and superior chloride SCC resistance make 2507 the material of choice for subsea risers, flowlines, and umbilicals operating in cold, high-pressure, high-chloride seawater environments. Its strength-to-weight advantage over carbon steel and standard stainless steels reduces catenary mass and installation costs.
- High-Concentration Chloride Environments: Ideal for chemical processing plants handling concentrated hydrochloric acid, sodium hypochlorite solutions, and other aggressive chloride-bearing media where 316L and 2205 grades would suffer premature failure.
- Flue Gas Desulfurization (FGD): In power plant and industrial FGD systems, the 2507 grade withstands the combined attack of sulfuric acid mist, particulate erosion, and cyclic wet-dry conditions that cause rapid degradation of conventional alloys.
- Additional Applications: Seawater desalination (RO membrane housings, heat exchangers), pulp and paper digesters, pharmaceutical processing equipment, nuclear waste storage, and offshore platform structural components.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality assurance framework ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- NACE MR0175 / ISO 15156 — Compliance for sour service (H₂S-containing) applications
- ASTM A790/A790M — Standard Specification for Seamless and Welded Austenitic-Ferritic Stainless Steel Pipes and Tubes
- EN 10216-5 — European standard for welded austenitic-ferritic stainless steel tubes
- DNV / API Standards — Marine and petroleum industry compliance certifications
- Mill Test Certificates (MTC) — Full chemical analysis, mechanical test data, and NDT reports provided per EN 10204 Type 3.1
- Third-Party Inspection (TPI) — Available upon request for critical project applications
Unique Selling Points
Exceptional PREN > 40: The highest pitting and crevice corrosion resistance among commercially available duplex stainless steels, providing a safety margin far exceeding conventional grades in chloride-rich environments.
High Strength at Moderate Weight: Yield strength of ≥550 MPa—approximately 60% higher than 316L—enabling thinner wall designs, reduced material consumption, and lower overall system costs without compromising corrosion performance.
Continuous Coil Format: Delivered as a continuous coil, minimizing cutting waste and enabling high-throughput automated forming, bending, and welding operations for large-scale manufacturing.
Full Traceability: Every coil is accompanied by comprehensive mill documentation ensuring complete lot-to-heat traceability, critical for regulatory compliance in oil & gas, nuclear, and pharmaceutical sectors.