0Cr25Ni20 Heat-Resistant Super Austenitic Stainless Steel Coil Tube for Superheated Steam Service
Product Overview
The 0Cr25Ni20 heat-resistant super austenitic stainless steel coil tube (also designated as S31008 / UNS S31008 in international standards) is a high-performance seamless tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coil tube is specifically engineered for superheated steam (Superheated Steam Coil Tube) applications in power generation, petrochemical processing, and high-temperature industrial furnaces. The material designation "0Cr25Ni20" indicates a composition of approximately 25% Chromium (Cr) and 20% Nickel (Ni), providing exceptional resistance to oxidation, scaling, and thermal cycling at temperatures exceeding 1100°C.
This product represents a critical component in the superheater systems of coal-fired boilers, waste-to-energy incinerators, and high-temperature process heaters where conventional austenitic grades such as 304 or 310S may exhibit accelerated degradation. The coil tube configuration allows for flexible field installation in serpentine or hairpin tube arrangements typical of radiant and convective superheater sections.
Material & Properties
Chemical Composition (Wt%)
| Element | Minimum | Maximum |
|---|---|---|
| Carbon (C) | — | 0.08 |
| Chromium (Cr) | 24.0 | 26.0 |
| Nickel (Ni) | 19.0 | 21.0 |
| Manganese (Mn) | — | 2.0 |
| Silicon (Si) | — | 1.0 |
| Sulfur (S) | — | 0.03 |
| Phosphorus (P) | — | 0.035 |
| Iron (Fe) | Balance | — |
Mechanical Properties (Solution-Treated Condition)
| Property | Specification |
|---|---|
| Tensile Strength (UTS) at Room Temperature | ≥ 520 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Hardness (HBW) | ≤ 200 |
| Creep Strength at 1000°C (10,000 hours) | ≥ 30 MPa |
| Maximum Continuous Service Temperature | 1150°C |
| Short-Time Peak Temperature | 1200°C |
Thermophysical Properties
- Thermal Conductivity (1000°C): ~12 W/(m·K)
- Linear Thermal Expansion (20–1000°C): ~19.5 × 10⁻⁶ /K
- Density: 7.98 g/cm³
- Specific Heat (1000°C): ~0.55 J/(g·K)
- Corrosion Resistance: Superior resistance to oxidizing atmospheres, SO₂, SO₃, and ash-induced corrosion; excellent resistance to intergranular corrosion (IGC) due to low carbon content
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | 0Cr25Ni20 Heat-Resistant Stainless Steel Coil Tube (Coiltube) |
| Standard Designation | GB/T 24511, GB/T 12770, ASTM A213 TP310H, EN 10216-5 |
| Outer Diameter (OD) | Φ14.0 mm – Φ60.3 mm |
| Wall Thickness (WT) | 1.5 mm – 8.0 mm |
| Coil Inner Diameter | 500 mm – 1200 mm (configurable) |
| Tube Length per Coil | Continuous coil, typically 200 m – 2000 m per spool |
| Surface Finish | Mill finish, polished, or pickled & passivated |
| Tolerance (OD) | ±0.15 mm (standard); ±0.10 mm (precision) |
| Tolerance (WT) | ±10% of nominal wall thickness |
| End Condition | Plain end, beveled, or flanged per customer specification |
| Heat Treatment | Solution annealed at 1050°C – 1100°C, followed by water quench |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
Manufacturing Process
- Raw Material Selection: Virgin nickel-based ingots or EBF (Electric Arc Furnace) + AOD (Argon Oxygen Decarburization) refined heats are selected to ensure precise Cr/Ni ratios and ultra-low sulfur and phosphorus content.
- Hot Rolling / Hot Extrusion: Billets are reheated to 1150°C–1250°C and hot-rolled or hot-extruded into seamless tube blanks with controlled dimensional tolerances.
- Piercing and Elongation: For coil tube production, the tube blanks undergo piercing on a Mannesmann-type piercer, followed by multi-stand rolling mills to achieve the desired OD and WT in coil form.
- Solution Annealing: Tubes are solution-annealed in a continuous annealing furnace (CAF) at 1050°C–1100°C under a protective atmosphere (N₂ or H₂/CH₄ mixture) to dissolve carbides and restore full austenitic structure.
- Quenching: Immediate water quenching follows annealing to prevent grain growth and maintain solution-strengthened microstructure.
- Pickling and Passivation: Tubes are subjected to acid pickling (HNO₃/HF blend) to remove scale and oxide films, followed by passivation to establish a protective chromium oxide layer.
- Coiling: Finished tubes are coiled onto mandrels using precision coiling machines to maintain uniform curvature without residual stress or deformation.
- Non-Destructive Testing (NDT): 100% eddy current testing (ECT) and ultrasonic testing (UT) are performed along the entire tube length to detect internal defects, wall thinning, or surface cracks.
- Hydrostatic Testing: Each coil is hydrostatically tested at 1.5–2.0 times the maximum design pressure to verify structural integrity and weld/seam soundness.
Applications
- Superheated Steam Coil Tubes in Coal-Fired Boilers: Primary application in radiant and convective superheater sections of utility boilers operating at steam temperatures of 550°C–620°C, where thermal fatigue and ash corrosion are dominant failure mechanisms.
- Waste-to-Energy (WtE) Incinerator Furnaces: Used for furnace wall tubes and superheaters in municipal solid waste incineration plants exposed to aggressive flue gas containing Cl, S, and alkali metals.
- Petrochemical Process Heaters: Tubular furnaces in refineries and chemical plants where hydrocarbon cracking and reforming require tubes at temperatures up to 1100°C.
- Cement Kiln Burners and Preheater Systems: High-temperature exhaust ducts and heat recovery coils in cement manufacturing.
- Crack Repair and Field Replacement: As documented in the technical study case "0Cr25Ni20 Heat-Resistant Steel Superheated Steam Coil Tube Crack Repair", this coil tube serves as a reliable replacement material for in-service repair of cracked superheater tubes, restoring structural integrity and extending boiler operational life.
- Heat Exchangers and Radiators: High-temperature air heaters, regenerators, and waste heat recovery systems in metallurgical and glass manufacturing industries.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification for manufacturing processes
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management
- ASME Certificate of Compliance (CoC): For products intended for pressure vessel and boiler applications per ASME BPVC Section I
- TÜV Certification: Product conformity assessment for European market compliance
- EN 10204 3.1 Test Reports: Independent third-party material certification for each heat and coil
- Mill Test Reports (MTR): Comprehensive documentation including chemical analysis, mechanical test results, NDT reports, and dimensional verification for every production lot
- NB (National Board) Registration: For products exported to North American boiler and pressure vessel markets
Unique Selling Points
- Exceptional Thermal Stability: The high Cr (25%) and Ni (20%) content provides a stable, protective Cr₂O₃ oxide scale even at 1100°C, significantly outperforming 304H or 310S in aggressive oxidizing environments.
- Proven Crack Repair Performance: Extensive field experience documented in technical case studies demonstrates the material's suitability for in-service repair of superheater tubes, reducing unplanned outages and extending asset life by 3–5 years.
- Coil Configuration Advantage: Pre-coiled delivery reduces on-site fabrication time, minimizes field welding joints, and ensures consistent tube geometry for optimal heat transfer in serpentine superheater circuits.
- Low Carbon Content: With C ≤ 0.08%, the material exhibits excellent resistance to intergranular corrosion and sensitization, even after prolonged exposure to elevated temperatures.
- Comprehensive Quality Traceability: Full heat-to-heat traceability from raw material through final coiling, supported by digital MTR documentation and third-party inspection.
- Customizable Dimensions: Flexible OD, WT, and coil diameter options to accommodate specific OEM specifications and retrofit requirements.
Note: The technical knowledge base associated with this product includes documented case studies on crack repair of 0Cr25Ni20 superheated steam coil tubes, providing valuable engineering guidance for maintenance and replacement decisions in operating power plants. Wenzhou Jixing Metal Materials Co., Ltd maintains a dedicated technical support team to assist customers with material selection, failure analysis, and repair engineering for high-temperature coil tube applications.