S31803 Duplex Stainless Steel Coil Tube for Industrial Applications
Product Overview
The S31803 Duplex Stainless Steel Coil Tube is a high-performance austenitic-ferritic (duplex) alloy tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed as an early-generation designation for the widely recognized 2205 duplex stainless steel family, S31803 offers exceptional mechanical strength, outstanding resistance to chloride stress corrosion cracking (SCC), and superior resistance to pitting and crevice corrosion. This coil tube format provides manufacturing flexibility, enabling customers to form, cut, and fabricate tubing to precise dimensional requirements for a wide range of industrial applications.
S31803 represents the legacy designation for 2205 duplex steel, distinguished from the current S32205 specification by a slightly lower minimum nitrogen (N) content requirement. While S32205 is the recommended designation for new engineering designs, S31803 continues to be specified in numerous legacy projects, ongoing maintenance programs, and established equipment platforms where historical material traceability and consistency are paramount.
Material & Properties
S31803 duplex stainless steel features a balanced microstructure consisting of approximately 50% austenite and 50% ferrite, delivering a unique combination of properties that surpasses conventional austenitic stainless steels such as 304 and 316 in many demanding service environments.
- Chemical Composition (Typical): C ≤ 0.03%, Mn ≤ 2.0%, Si ≤ 1.0%, P ≤ 0.030%, S ≤ 0.020%, Cr 22.0–23.0%, Ni 4.5–6.5%, Mo 3.0–3.5%, N ≥ 0.14% (minimum slightly lower than S32205's 0.14–0.20% range)
- Yield Strength: ≥ 450 MPa (65,250 psi) — approximately twice that of 304/316 austenitic grades
- Tensile Strength: ≥ 550 MPa (79,750 psi)
- Elongation: ≥ 25% (indicating excellent ductility and formability)
- PREN (Pitting Resistance Equivalent Number): ≥ 34, providing superior resistance to localized corrosion in chloride-containing environments
- Thermal Conductivity: ~14.6 W/(m·K) — approximately double that of 304/316, enabling efficient heat transfer
- Coefficient of Thermal Expansion: ~11.5 µm/(m·°C) — significantly lower than austenitic grades, reducing thermal stress in cyclic service
- Maximum Service Temperature: 250°C (482°F) in chloride environments; up to 300°C (572°F) in non-chloride environments
- Cold Workability: Excellent — suitable for deep drawing, bending, and coil-forming operations
Specifications
| Parameter | Specification |
|---|---|
| Material Designation | S31803 (UNS) / 1.4462 (EN) / 03Cr22Ni5Mo3N (China GB) |
| Equivalent Grades | 2205 Duplex / SAF 2205 / Z22053 (France) / 1.4462 (Germany) |
| Product Form | Coil Tube (盘管) |
| Outer Diameter (OD) | 3.18 mm (1/8") – 38.10 mm (1.5") |
| Wall Thickness | 0.30 mm (0.012") – 3.18 mm (1/8") |
| Coil Inner Diameter (ID) | 200 mm – 500 mm (8" – 20") |
| Coil Length | Custom lengths available; standard up to 200 m (656 ft) per coil |
| Surface Finish | Pickled & Passivated (2B), Bright Annealed (BA), or Custom Polished |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm (±0.002" – ±0.006") |
| Tolerance (Wall) | ±10% of nominal |
| Applicable Standards | ASTM A790 / A790M, EN 10216-5, GB/T 21832, ASME B31.3 |
| Manufacturing Method | Seamless (Pierced & Drawn) or Welded (ERW/ODW) |
| Hardness | ≤ 32 HRC (annealed condition) |
Manufacturing Process
The production of S31803 Duplex Stainless Steel Coil Tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing sequence to ensure consistent quality, dimensional accuracy, and metallurgical integrity:
- Raw Material Selection: Virgin duplex stainless steel billets or strip are sourced from certified mills with full chemical composition verification and heat number traceability.
- Hot Rolling / Piercing: Billets are heated to 1150–1250°C (2092–2282°F) and pierced or hot-rolled into hollow tubes, establishing the initial outer diameter and wall thickness.
- Intermediate Annealing: Tubes are solution-annealed at 1020–1080°C (1868–1976°F) followed by rapid water quenching to restore the balanced austenite-ferrite microstructure and ensure maximum ductility.
- Cold Drawing / Cold Pilgering: Tubes are cold-worked through a series of dies to achieve precise final dimensions, superior surface finish, and enhanced mechanical properties.
- Final Annealing & Stress Relief: A controlled annealing cycle eliminates residual stresses introduced during cold working while maintaining the duplex microstructure.
- Pickling & Passivation: Tubes are pickled to remove mill scale and oxidized surfaces, followed by passivation treatment to establish a protective chromium oxide layer, ensuring maximum corrosion resistance.
- Coil Winding: Finished tubes are carefully wound into coils on precision-controlled winding equipment, maintaining consistent coil geometry and preventing surface damage.
- Quality Inspection & Packaging: Each coil undergoes comprehensive non-destructive testing (NDT), dimensional verification, and visual inspection before protective packaging and labeling.
Applications
S31803 Duplex Stainless Steel Coil Tube is specified in demanding industrial applications where superior strength-to-weight ratios, exceptional corrosion resistance, and high thermal efficiency are critical:
- Oil & Gas Industry: Subsea pipelines, wellhead components, heat exchanger tubes, and process piping in offshore platforms and refineries
- Chemical Processing: Reactor heat exchangers, condensers, evaporators, and process coils handling aggressive chemical media
- Marine & Offshore Engineering: Seawater piping systems, ballast water treatment equipment, and shipbuilding applications exposed to chloride-rich environments
- Pulp & Paper Industry: Black liquor evaporators, recovery boilers, and digesters where sulfuric acid and high-temperature chloride exposure is present
- Power Generation: Flue gas desulfurization (FGD) systems, boiler feedwater systems, and cooling water circuits
- Food & Beverage Processing: Hygienic process coils, pasteurization systems, and dairy processing equipment requiring high cleanliness and corrosion resistance
- Pharmaceutical Industry: Process heat exchangers, sanitary tubing, and equipment subject to caustic cleaning solutions (CIP systems)
- Desalination Plants: Multi-stage flash (MSF) and reverse osmosis (RO) system components, brine handling coils
- Legacy Project Maintenance: Replacement tubing for existing installations originally designed with S31803 specifications, ensuring metallurgical compatibility and traceability
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications ensuring that every S31803 Coil Tube product meets international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System certification
- CE Marking — Conformity with European Union directives for pressure equipment (PED 2014/68/EU)
- NORSOK M-650 — Norwegian standard for stainless steel materials in oil & gas applications
- ASTM A790 / A790M Compliance — Full material and mechanical property compliance
- EN 10204 3.1 Certificates — Third-party verified material test certificates provided with every shipment
- NDT Testing: 100% ultrasonic testing (UT), eddy current testing (ECT), and hydrostatic pressure testing
- Full Heat Traceability: Every coil is traceable to its original mill heat number with complete chemical and mechanical test data
Unique Selling Points
Exceptional Strength at Half the Weight: S31803 duplex steel delivers approximately twice the yield strength of 304/316 austenitic stainless steels, enabling thinner wall designs, lighter equipment, and significant cost savings in material and structural support.
Superior Chloride Corrosion Resistance: With a PREN of ≥ 34, S31803 provides outstanding resistance to pitting, crevice corrosion, and chloride stress corrosion cracking — making it the material of choice for marine, chemical, and oil & gas environments.
Enhanced Thermal Performance: The duplex microstructure provides roughly double the thermal conductivity of austenitic grades, resulting in more compact and efficient heat exchanger designs with reduced tube counts and footprint.
Legacy Project Compatibility: As the original 2205 designation, S31803 ensures metallurgical consistency for maintenance and replacement work on existing installations, while maintaining full compliance with current international standards.
Coil Tube Flexibility: The coil format eliminates joint wastage, enables automated cutting and forming, and provides cost-effective solutions for high-volume production runs.
Lower Thermal Expansion: Approximately 40% lower coefficient of thermal expansion than 304/316, reducing thermal fatigue and extending service life in cyclic temperature applications.
Recommendation Note
While S31803 remains fully compliant with ASTM A790 and EN 10216-5 standards and is suitable for all applications where 2205 duplex steel is specified, engineering teams initiating new project designs are advised to reference S32205 — the current ASTM designation — which specifies a slightly higher minimum nitrogen content (0.14–0.20% vs. S31803's lower bound) and is the preferred reference in modern design codes. Wenzhou Jixing Metal Materials Co., Ltd. offers both S31803 and S32205 designations to accommodate both legacy maintenance requirements and new engineering specifications.