Stainless Steel Coil Tube (Coiltube) — Product No. 1334
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous tube product designed for demanding industrial applications, particularly in high-temperature and high-pressure environments such as once-through boilers (DC boilers), heat exchangers, chemical processing systems, and energy generation facilities. Unlike conventional straight-length tubes, coil tubes are produced in continuous spiral form, enabling seamless integration into complex piping networks with minimal joint requirements, thereby significantly reducing the risk of leak points and failure sites.
This product line addresses critical industry challenges identified through extensive field research, including the well-documented phenomenon of corrosion-induced perforation in DC boiler coil tubes. The engineering design incorporates advanced metallurgical solutions to mitigate common degradation mechanisms such as pitting corrosion, intergranular corrosion, stress corrosion cracking (SCC), and flow-accelerated corrosion (FAC).
Material & Properties
Grade Designations
- Austenitic Stainless Steels: SUS304 (ASTM 304), SUS304L (ASTM 304L), SUS316L (ASTM 316L), SUS321 (ASTM 321), SUS310S (ASTM 310S)
- Super Austenitic Grades: Alloy 20, Alloy 6 (UNS N08066), Alloy 800 (UNS N08800)
- Ferritic/Martensitic Grades (upon request): SUS430, SUS410
Key Mechanical Properties
| Property | ASTM 304L | ASTM 316L | Alloy 6 (N08066) |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 485 | ≥ 485 | ≥ 586 |
| Yield Strength (MPa) | ≥ 205 | ≥ 205 | ≥ 276 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 35 |
| Maximum Service Temperature (°C) | 870 | 870 | 1000 |
| Corrosion Resistance (PWHT recommended) | Good | Excellent (chloride resistant) | Outstanding |
Chemical Composition (Typical, wt%)
| Element | ASTM 304L | ASTM 316L |
|---|---|---|
| C (Carbon) | ≤ 0.030 | ≤ 0.030 |
| Cr (Chromium) | 18.0 – 20.0 | 16.5 – 18.5 |
| Ni (Nickel) | 8.0 – 10.5 | 10.0 – 14.0 |
| Mo (Molybdenum) | — | 2.0 – 3.0 |
| N (Nitrogen) | ≤ 0.10 | ≤ 0.10 |
| Si (Silicon) | ≤ 1.00 | ≤ 1.00 |
| Mn (Manganese) | ≤ 2.00 | ≤ 2.00 |
Specifications
| Parameter | Specification Range |
|---|---|
| Outer Diameter (OD) | φ6.0 mm – φ114.3 mm (¼" – 4½") |
| Wall Thickness | 0.3 mm – 6.0 mm (0.012" – 0.236") |
| Coil Length | Up to 3000 m (continuous production capability) |
| Bend Radius (Minimum) | ≥ 3D (D = outer diameter) |
| Tolerance — OD | ± 0.10 mm (± 0.004") |
| Tolerance — Wall Thickness | ± 10% of nominal |
| Surface Finish | Mill finish, polished (Ra ≤ 0.4 μm), or electropolished (upon request) |
| End Form | Plain cut, beveled, or threaded (per customer specification) |
| Delivery Condition | Annealed (Solution Heat Treated), pickled, and passivated |
| Coil Diameter (Shipping) | 1000 mm – 2000 mm |
| Maximum Operating Pressure | Up to 35 MPa (dependent on grade and dimensions) |
| Standards Compliance | ASTM A213, ASTM A269, GB/T 13296, EN 10216-5, JIS G3459 |
Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous multi-stage process engineered to ensure dimensional precision, metallurgical integrity, and corrosion resistance:
- Raw Material Selection: Only certified virgin or certified recycled stainless steel billets and flat strips are procured, with full chemical composition verification via spectrometric analysis.
- Hot Rolling / Hot Extrusion: Billets are heated to 1150–1200°C and hot rolled or extruded to produce seamless tube blanks or hot-rolled coil strip.
- Pickle & Passivation: Tubes are subjected to acid pickling (HNO₃/HF blend) to remove mill scale, followed by passivation treatment to establish a stable chromium oxide protective layer.
- Cold Drawing / Cold Pilgering: Tubes are cold-worked through precision-die drawing mills to achieve exact final dimensions with tight tolerances and improved surface finish.
- Continuous Coiling: The drawn tube is wound onto precision-guided rollers to form a continuous spiral coil with uniform curvature and no kinks or deformations.
- Solution Annealing (PWHT): Tubes are heat-treated at 1050–1150°C followed by controlled water quenching to dissolve precipitated carbides, restore full austenitic microstructure, and maximize corrosion resistance.
- Final Pickle & Passivation: Post-annealing pickling removes oxide scale; passivation re-establishes the protective passive film.
- Quality Inspection: 100% hydrostatic testing, eddy current testing (ECT), ultrasonic testing (UT), and dimensional verification are performed on every production lot.
Anti-Corrosion Engineering Considerations
Based on extensive analysis of DC boiler coil tube failure modes — including intergranular corrosion from chromium carbide precipitation, pitting in chloride-bearing boiler water, and flow-accelerated corrosion at high-velocity flow zones — the following engineering measures are incorporated:
- Ultra-Low Carbon Grades: Use of 304L and 316L (C ≤ 0.03%) to prevent sensitization and intergranular corrosion during high-temperature service.
- Stabilized Grades: Availability of Ti-stabilized (321) and Nb-stabilized (347) grades for applications exceeding 600°C.
- Stress Relief Annealing: Optional intermediate stress-relief treatments to minimize residual stresses that could promote SCC.
- Enhanced Surface Finish: Electropolished surfaces (Ra ≤ 0.2 μm) reduce surface roughness, minimizing localized corrosion initiation sites.
- Microalloying Options: Optional addition of rare earth elements (REE) to refine grain structure and enhance pitting resistance equivalent number (PREN).
Applications
- Power Generation: Once-through (DC) boilers, superheater tubes, reheater tubes, economizer elements, and steam generator tubing in subcritical, supercritical, and ultra-supercritical power plants.
- Chemical & Petrochemical Processing: Reactor heat exchange coils, distillation column internals, acid service piping, and high-purity process lines.
- Food & Pharmaceutical Industry: Sanitary process tubing requiring CIP (Clean-in-Place) compatibility and non-reactive surfaces.
- Oil & Gas: Subsea production manifolds, wellhead tubing, and offshore heat exchanger bundles.
- Nuclear Industry: Secondary circuit heat exchanger tubes (non-fuel applications).
- Marine Engineering: Seawater cooling coils, condenser tubes, and ballast system piping.
- Heat Exchanger Manufacturing: Pre-formed coil tube for coil-wound heat exchangers, condensers, and evaporators.
Quality Certifications & Testing
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| EN 10204 3.1 | Third-party inspection certificates for every lot |
| PE stamp / NACE SP0106 | Pressure equipment compliance (where applicable) |
| ASME SA-213 / SA-269 | Boiler and heat exchanger tube specifications |
| ASTM A270 | Corrosion testing — intergranular corrosion (ASTM A262 Practice E) |
| ASTM A967 | Passivation verification |
Inspection & NDT Methods Employed
- 100% Hydrostatic Pressure Test: Performed at 1.5× working pressure for a minimum hold time of 10 seconds per meter.
- Eddy Current Testing (ECT): Full-length automated inspection for wall thickness variation, surface defects, and internal discontinuities.
- Ultrasonic Testing (UT): Phased array UT for volumetric flaw detection in thicker wall sections.
- Spectroscopic Chemical Analysis: Every heat number verified against specification limits (± 0.5% tolerance on alloying elements).
- Hardness Testing: Rockwell B or Vickers hardness verification per ASTM E18/E92.
- Grain Size Verification: ASTM E112 grain size analysis confirming ≥ Grade 6 austenitic structure post-annealing.
- Flaring / Flattening / Expansion Tests: Per ASTM A213 Appendix requirements for formability verification.
Unique Selling Points
- DC Boiler Failure-Prevention Engineering: Product design informed by decades of field failure analysis data on once-through boiler coil tube perforation, incorporating metallurgical and surface engineering countermeasures.
- Continuous Length Capability: Coils up to 3000 meters eliminate longitudinal weld joints, dramatically reducing leak probability in high-pressure systems.
- Full Traceability: Every coil is traceable to mill heat number with complete chemical, mechanical, and NDT documentation.
- Custom Engineering Support: Dedicated metallurgical engineering team available for application-specific grade selection, corrosion resistance optimization, and failure analysis consultation.
- Multi-Standard Compliance: Simultaneous compliance with ASTM, EN, GB, and JIS standards enables global project qualification without re-testing.
Note: All specifications are subject to confirmation against the applicable standard revision in force at the time of order. Custom specifications beyond standard ranges are available upon technical review and mutual agreement between Wenzhou Jixing Metal Materials Co., Ltd and the purchaser.