2205 (S32205) Duplex Stainless Steel Coil Tube — Technical Specification
Product Overview
The 2205 (UNS S32205) Duplex Stainless Steel Coil Tube is a high-performance austenitic-ferritic (duplex) alloy coil tube engineered for demanding industrial environments requiring superior corrosion resistance, mechanical strength, and thermal stability. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube product represents a premier grade within the standard duplex stainless steel family, distinguished by its balanced microstructure of approximately 50% austenite and 50% ferrite phases.
Designed as a seamless or welded coil tube configuration, this product delivers exceptional performance in aggressive chloride-containing environments, high-pressure service conditions, and elevated-temperature applications. The coil tube form factor enables efficient downstream processing, including straightening, cutting, forming, and fabrication into complex geometries required by modern industrial systems.
Material Composition & Metallurgical Properties
The 2205 duplex stainless steel achieves its outstanding properties through a precisely engineered chemical composition that balances chromium (Cr), nickel (Ni), molybdenum (Mo), and nitrogen (N) content. The Pitting Resistance Equivalent Number (PREN) of approximately 34–38 positions this alloy well above standard austenitic grades such as 316L (PREN ≈ 24–26), providing substantially enhanced resistance to pitting corrosion, crevice corrosion, and stress corrosion cracking (SCC).
Chemical Composition (Typical)
| Element | Symbol | Minimum (%) | Maximum (%) | Function / Role |
|---|---|---|---|---|
| Carbon | C | — | 0.030 | Controls precipitation hardening; low C limits carbide formation |
| Chromium | Cr | 22.0 | 23.0 | Primary passive film former; enhances pitting and general corrosion resistance |
| Nickel | Ni | 4.5 | 6.5 | Stabilizes austenitic phase; balances duplex microstructure |
| Molybdenum | Mo | 2.5 | 3.5 | Significantly improves chloride resistance and PREN |
| Nitrogen | N | 0.14 | 0.20 | Raises yield strength and PREN; stabilizes austenite |
| Manganese | Mn | — | 1.50 | Minor austenite stabilizer |
| Silicon | Si | — | 1.00 | Deoxidizer; contributes to oxidation resistance |
| Iron | Fe | Balance | — | Base metal constituent |
Mechanical Properties (Annealed Condition)
| Property | Standard Value | Comparison vs. 316L |
|---|---|---|
| Yield Strength (0.2% Offset) | ≥ 450 MPa (65 ksi) | ~2× higher than 316L (≥ 170 MPa) |
| Tensile Strength | 550 – 800 MPa (80 – 116 ksi) | ~1.5× higher than 316L |
| Elongation (at fracture) | ≥ 25% | Comparable or slightly higher |
| Density | 7.8 g/cm³ | Similar to 316L |
| Thermal Conductivity (20°C) | 18 W/(m·K) | Lower than 316L (16.3 W/(m·K)) — moderate |
| Thermal Expansion Coefficient | 11.5 × 10⁻⁶ /K | Lower than 316L (17.1 × 10⁻⁶ /K) — reduced thermal stress |
| PREN (Pitting Resistance Equivalent Number) | 34 – 38 | ~1.4× higher than 316L (24–26) |
Corrosion Resistance Characteristics
- Pitting Corrosion Resistance: Superior resistance in chloride-containing environments (seawater, brine, acidic solutions) with PREN of 34–38 enabling reliable performance in saturated salt solutions at ambient temperature.
- Crevice Corrosion Resistance: Excellent resistance under tight geometries and stagnant fluid conditions where oxygen depletion occurs.
- Stress Corrosion Cracking (SCC) Resistance: The duplex microstructure provides significantly better SCC resistance than single-phase austenitic alloys, particularly in chloride environments at elevated temperatures (up to 100°C).
- General Corrosion: Outstanding performance in sulfuric acid (H₂SO₄) concentrations up to 10% at ambient temperature and in phosphoric acid solutions.
- Intergranular Corrosion: Low carbon content (≤ 0.030%) minimizes chromium carbide precipitation at grain boundaries during welding and heat exposure.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Designation | 2205 / UNS S32205 / 1.4462 / 03Cr22Ni5Mo3N |
| Product Form | Coil Tube (盘管) — Seamless or Welded |
| Applicable Standards | ASTM A790 / A790M, ASTM A213 / A213M, ASTM A269, EN 10216-5, ISO 3506 |
| Outer Diameter (OD) Range | 6.0 mm – 219.1 mm (¼" – 8½") |
| Wall Thickness Range | 0.5 mm – 12.0 mm (0.020" – 0.472") |
| Coil Length (Typical) | 5 m – 30 m per coil (customizable) |
| Surface Finish | Pickled & Passivated (P&P), No. 4 Brushed, BA (Bright Annealed), or Custom |
| Delivery Condition | Annealed (Solution Heat Treated), or Cold Worked (1/4 Hard, 1/2 Hard, Full Hard) |
| Maximum Service Temperature | 300°C (572°F) — Limited by 475°C intergranular embrittlement |
| Maximum Operating Pressure | Up to 100 bar (1,450 psi) — dependent on OD/WT and temperature |
| Welding Compatibility | Excellently weldable; use matching filler (e.g., ER2209, E309L) per AWS D1.6 |
| Equivalent PREN | 34 – 38 |
| Equivalent Number (EN) | 35 – 38 |
| Packaging | Export-grade wooden pallets with moisture-proof wrapping; VCI (Vapor Corrosion Inhibitor) treated |
Manufacturing Process
The production of 2205 duplex stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing workflow designed to ensure metallurgical integrity, dimensional accuracy, and consistent mechanical performance.
Process Flow
- Raw Material Sourcing & Verification: Virgin duplex stainless steel billets or slabs are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition compliance with ASTM/EN specifications.
- Piercing & Pipe Forming: Billets are heated to controlled temperatures (1,100–1,200°C) and pierced to form hollow blanks. Alternatively, strip material is cold-rolled and welded (ERW — Electric Resistance Welded) for seamless coil tube production.
- Hot Rolling & Sizing: The pierced tube is hot-rolled through a series of reducing stands to achieve the target outer diameter and wall thickness. Precise temperature control during rolling ensures the desired duplex phase balance (45–55% ferrite/austenite ratio).
- Cold Drawing / Cold Rolling: For tighter tolerances and improved surface finish, tubes undergo cold drawing or cold rolling to final dimensions. This step enhances mechanical properties through controlled work hardening.
- Heat Treatment (Solution Annealing): Tubes are heated to 1,020–1,100°C and rapidly quenched (air or water) to dissolve precipitates, restore full duplex microstructure, and achieve maximum corrosion resistance and ductility.
- Pickling & Passivation: The surface is treated with mixed acid solutions (HNO₃/HF) to remove mill scale and oxidation products. Subsequent passivation forms a stable chromium oxide (Cr₂O₃) passive film, enhancing long-term corrosion resistance.
- Coiling & Straightening: Tubes are wound into coils at controlled tension to prevent deformation. Downstream straightening (induction or mechanical) is available upon request for specific applications.
- Quality Inspection & Testing: Each coil undergoes comprehensive quality control including dimensional verification (OD, WT, straightness), hydrostatic pressure testing, visual inspection, and non-destructive testing (NDT) as required.
- Packaging & Dispatch: Finished coils are packaged to export standards with protective wrapping, moisture barriers, and secure palletization for global shipment.
Applications & End-Use Industries
The 2205 duplex stainless steel coil tube is the material of choice for high-performance industrial applications where the combination of high strength and exceptional corrosion resistance is critical. Its primary application domains include:
Primary Applications
- High-Pressure Heat Exchangers: The elevated yield strength (≥ 450 MPa) allows for thinner wall designs at high operating pressures, reducing material costs and weight while maintaining structural integrity. The coil tube form enables efficient hairpin or U-tube configurations in shell-and-tube heat exchangers.
- Desalination Equipment: Widespread use in Reverse Osmosis (RO) membrane housings, brine concentrate piping, seawater intake systems, and distillation plant components. The high PREN (34–38) ensures long service life in saturated sodium chloride environments.
- Oil & Gas Pipelines: Employed in subsea flowlines, wellhead equipment, oil and gas separators, and chemical injection systems. The duplex structure provides resistance to sulfide stress cracking (SSC) and chloride-induced SCC in sour service conditions (NACE MR0175 compliant).
Additional Application Areas
- Offshore platforms and subsea production systems
- Pulp and paper processing equipment (digesters, washers)
- Chemical processing vessels and piping (fertilizer, pharmaceutical)
- Marine engineering (propulsion shafts, seawater cooling systems)
- Food processing equipment requiring high hygiene standards
- Power generation (condenser tubes, boiler components)
- Environmental protection (flue gas desulfurization systems)
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that every 2205 duplex stainless steel coil tube product meets or exceeds international standards and industry requirements.
Applicable Standards & Certifications
| Standard / Certification | Scope |
|---|---|
| ASTM A790 / A790M | Seamless and Welded Duplex Stainless Steel Tubes for High-Pressure Boilers and Heat Exchangers |
| ASTM A213 / A213M | Seamless Austenitic Chromium-Stainless Steel Tubing for Heat-Exchanger and Heat-Treating Equipment |
| EN 10216-5 | Seamless Tubes for Technical Uses — Duplex Stainless Steel Tubes |
| ISO 9001:2015 | Quality Management System Certification |
| ISO 14001:2015 | Environmental Management System Certification |
| ISO 45001:2018 | Occupational Health and Safety Management |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for EU market |
| NACE MR0175 / ISO 15156 | Materials for use in H₂S-containing environments in oil and gas production |
| API 5CT / API 5L (Equivalent) | Petroleum and natural gas industry piping and tubular goods |
| Mill Test Certificates (MTC) | EN 10204 3.1 / 3.2 — Chemical analysis, mechanical test results, NDT reports |
Testing & Inspection Protocols
- Chemical Analysis: Optical Emission Spectroscopy (OES) and/or Inductively Coupled Plasma (ICP) analysis for every heat lot.
- Mechanical Testing: Tensile testing, hardness testing (Rockwell/Brin