S31803 Duplex Stainless Steel Coil Tube (2205)
S31803 Duplex Stainless Steel Coil Tube is a high-performance austenitic-ferritic duplex stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This grade represents the early designation of the well-known 2205 duplex family, offering an excellent balance of mechanical strength, corrosion resistance, and toughness for demanding industrial applications. As a legacy but still widely specified grade, S31803 remains a trusted choice for existing project requirements and maintenance programs worldwide.
Product Overview
The S31803 duplex stainless steel coil tube is a cold-worked, coiled seamless tube engineered from a balanced austenitic-ferritic microstructure. This dual-phase metallurgy provides approximately twice the yield strength of conventional austenitic grades such as 304 or 316, while delivering superior resistance to chloride-induced stress corrosion cracking (SCC) and pitting corrosion. The coil form factor enables continuous, high-efficiency downstream processing including heat exchanger manufacturing, U-tube production, and spiral winding operations, minimizing material waste and fabrication time.
As an early designation of the 2205 duplex family, S31803 features a slightly lower nitrogen content lower limit compared to its successor S32205. This characteristic makes it particularly suitable for applications where moderate nitrogen levels are sufficient and where historical project specifications or procurement standards mandate the S31803 designation. Wenzhou Jixing Metal Materials Co., Ltd. maintains strict adherence to legacy specifications while ensuring full traceability and compliance with international material standards.
Material & Properties
Chemical Composition (Typical)
| Element | Specification (wt%) |
|---|---|
| C (Carbon) | ≤ 0.030 |
| Si (Silicon) | ≤ 1.00 |
| Mn (Manganese) | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.030 |
| S (Sulfur) | ≤ 0.020 |
| Cr (Chromium) | 22.0 – 23.0 |
| Ni (Nickel) | 3.0 – 3.5 |
| Mo (Molybdenum) | 3.0 – 3.5 |
| N (Nitrogen) | ≤ 0.08 (lower limit slightly below S32205) |
| Fe (Iron) | Balance |
Mechanical Properties (Annealed Condition)
| Property | Specification |
|---|---|
| Tensile Strength | ≥ 620 MPa (≥ 90 ksi) |
| Yield Strength (0.2% offset) | ≥ 450 MPa (≥ 65 ksi) |
| Elongation | ≥ 25% |
| Hardness | ≤ 32 HRC (typical 25–30 HRC) |
| Density | 7.81 g/cm³ |
| Thermal Conductivity (20°C) | ≈ 24 W/(m·K) |
| Thermal Expansion Coefficient (20–600°C) | ≈ 12.4 × 10⁻⁶ /K |
| Maximum Service Temperature | 250°C (482°F) |
Corrosion Resistance
- PREN (Pitting Resistance Equivalent Number): 32–34, indicating excellent resistance to pitting and crevice corrosion in chloride-containing environments.
- Stress Corrosion Cracking (SCC): Superior resistance to chloride-induced SCC compared to 304 and 316 austenitic grades, making S31803 ideal for marine, chemical, and offshore environments.
- Intergranular Corrosion: Low carbon content (≤ 0.030%) provides excellent resistance to sensitization during welding and fabrication.
- Acid Resistance: Effective in dilute sulfuric, phosphoric, and acetic acid solutions at moderate temperatures.
Specifications
| Parameter | Specification |
|---|---|
| Grade Designation | S31803 (UNS) / EN 1.4462 equivalent |
| Common Trade Name | 2205 Duplex (Early Designation) |
| Product Form | Coil Tube (Continuous Coil) |
| Manufacturing Method | Seamless (Pierced / Continuous Casting) |
| Outer Diameter Range | Φ6.0 mm – Φ108.0 mm (custom sizes available) |
| Wall Thickness Range | 0.5 mm – 6.0 mm |
| Coil Inner Diameter | 200 mm – 600 mm (configurable) |
| Coil Weight | Up to 2,000 kg per coil (standard) |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated |
| Delivery Condition | Solution Annealed / Pickled & Passivated |
| Applicable Standards | ASTM A790, ASTM A928, EN 10217-7, ISO 11612 |
| Equivalent Grades | S32205 (successor), 2205, UNS S31803 |
Manufacturing Process
Wenzhou Jixing Metal Materials Co., Ltd. employs a rigorous multi-stage manufacturing process to produce S31803 duplex stainless steel coil tubes that meet the highest quality standards:
- Raw Material Selection: Only certified, low-carbon S31803 duplex stainless steel slabs are sourced from approved mills. Each heat is accompanied by a full mill test certificate (MTC) confirming chemical composition and mechanical properties.
- Hot Rolling & Piercing: Slabs are reheated to forging temperature and hot-rolled into seamless tube blanks through either the Mannesmann piercing method or continuous casting process, ensuring uniform wall thickness and structural integrity.
- Cold Drawing & Sizing: Tubes undergo precision cold drawing through calibrated dies to achieve exact outer diameter and wall thickness tolerances. Multi-pass cold reduction ensures optimal grain structure and dimensional accuracy.
- Solution Annealing: Tubes are solution-annealed at 1050–1100°C followed by controlled cooling to achieve the target austenitic-ferritic phase balance (typically 40–60% ferrite), ensuring optimal mechanical and corrosion properties.
- Pickling & Passivation: Surface treatment involves acid pickling to remove scale and oxide layers, followed by passivation treatment to establish a protective chromium oxide film on the surface.
- Coiling: Finished tubes are wound into coils on precision-controlled coiling equipment, with internal protective wrapping to prevent mechanical damage and surface contamination during storage and transportation.
- Quality Inspection: Every coil undergoes 100% visual inspection, dimensional measurement, hydrostatic pressure testing, and sampling for mechanical property verification and corrosion testing.
Applications
S31803 duplex stainless steel coil tube is engineered for demanding environments where the combination of high strength and excellent corrosion resistance is critical:
- Petrochemical & Oil/Gas Industry: Heat exchanger tubes, separator internals, pipeline systems, and offshore platform components where chloride-induced SCC is a concern.
- Marine & Offshore Applications: Seawater cooling systems, ballast tanks, propeller shafts, and subsea equipment operating in aggressive marine environments.
- Chemical Processing: Reactor vessels, heat exchangers, distillation columns, and process piping handling corrosive chemicals including chlorinated solutions and dilute acids.
- Power Generation: Boiler tubes, condensate systems, and cooling water circuits in both conventional and renewable energy power plants.
- Food & Pharmaceutical Processing: Sanitary-grade heat exchangers, mixing vessels, and processing equipment requiring high strength and corrosion resistance.
- Water Treatment & Desalination: Seawater reverse osmosis (SWRO) systems, brine handling equipment, and municipal water treatment infrastructure.
- Legacy Project Maintenance: Replacement and repair of existing systems originally designed and specified with S31803 material, ensuring metallurgical compatibility and continued performance.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and international certifications to ensure every S31803 coil tube product meets global standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating environmental responsibility in manufacturing.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- EN 10204 3.1 — Mill Test Certificates with full chemical and mechanical test data for every heat and coil.
- ASTM / ASME Compliance — Products manufactured to ASTM A790, A928, and ASME B36.19M standards.
- EN 10217-7 Compliance — European standard compliance for seamless stainless steel tubes.
- NORSOK M-650 — Compliance for offshore and subsea applications where specified.
- Third-Party Inspection (TPI) — Available upon request for critical applications, with inspection by recognized organizations including BV, DNV, Lloyd's Register, and SGS.
Unique Selling Points
- Legacy Specification Compliance: Full adherence to S31803 specifications for existing projects, maintenance programs, and procurement standards that require this early 2205 designation — ensuring drop-in replacement compatibility without design modifications.
- Superior Strength-to-Corrosion Ratio: Approximately twice the yield strength of 304/316 austenitic grades combined with PREN of 32–34, enabling thinner wall designs that reduce weight and material costs without compromising performance.
- Continuous Coil Format: Coil delivery enables uninterrupted downstream processing, reducing fabrication time, labor costs, and material waste compared to cut-length alternatives.
- Full Traceability: Every coil is accompanied by detailed mill test certificates, ultrasonic testing reports, and heat-number traceability from raw material through final delivery.
- Customization Capability: Flexible sizing, surface finishing, and coil configuration options to meet specific project requirements.
- Cost-Effective Alternative: While S32205 is recommended for new designs, S31803 offers a cost-effective solution for applications where slightly lower nitrogen content is acceptable, reducing material expenditure without significant performance compromise.
Design Note: For new engineering projects, S32205 is the recommended successor grade with a higher nitrogen content lower limit (≥ 0.14%), providing enhanced mechanical properties and corrosion resistance. However, S31803 remains fully compliant with all applicable standards and is the preferred choice for legacy system maintenance, spare parts procurement, and projects governed by historical specifications. Wenzhou Jixing Metal Materials Co., Ltd. supplies both grades with identical manufacturing quality and certification rigor.