Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed for high-performance thermal management systems, heat exchange applications, and fluid transport networks. The product is supplied in continuous coil form, offering significant advantages in installation efficiency, material utilization, and structural flexibility compared to straight-pipe alternatives.
Rooted in extensive experimental research on coil tube thermal performance — including studies on ice-storage systems and enhanced heat transfer mechanisms — this product line integrates metallurgical excellence with thermodynamic optimization. The coiled geometry inherently promotes turbulent flow patterns within the tube bore, significantly enhancing convective heat transfer coefficients and reducing thermal resistance in heat exchange applications.
2. Material Composition & Properties
2.1 Base Alloy Grades
- Austenitic Stainless Steels: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100)
- Super-Austenitic Grades: AISI 316L (UNS S31603), AISI 904L (UNS N08904)
- Duplex Stainless Steels: 2205 (UNS S31803), 2507 (UNS S32750)
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥ 515 MPa (AISI 304), ≥ 585 MPa (AISI 316L)
- Yield Strength (0.2% offset): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 223 HB (annealed condition)
2.3 Physical & Thermal Properties
- Thermal Conductivity: 14.6–16.3 W/(m·K) at 25°C
- Specific Heat Capacity: 478 J/(kg·K)
- Thermal Expansion Coefficient: 16.0–17.4 × 10⁻⁶ /°C
- Density: 7.90–8.00 g/cm³
- Operating Temperature Range: −196°C to +870°C (grade-dependent)
2.4 Corrosion Resistance
The austenitic and duplex alloy compositions provide exceptional resistance to general corrosion, pitting, crevice corrosion, and stress corrosion cracking (SCC). The passive chromium oxide film (Cr₂O₃) self-repairs in oxidizing environments, ensuring long-term service life in aggressive chemical and marine atmospheres.
3. Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 60.0 mm | ASTM A269 / ASME SA-213 |
| Wall Thickness | 0.3 mm – 3.0 mm | ASTM A269 |
| Coil Inner Diameter (CID) | 200 mm – 800 mm | Manufacturer Specification |
| Coil Length (per roll) | 50 m – 500 m (configurable) | — |
| Bending Radius (minimum) | ≥ 3× OD | ASTM A999 |
| Surface Finish | 2B, BA (Bright Annealed), No. 4, Mirror (Ra ≤ 0.2 μm) | ASTM A480 |
| Tolerance — OD | ±0.05 mm to ±0.15 mm | ASTM A269 |
| Tolerance — Wall Thickness | ±0.025 mm to ±0.05 mm | ASTM A269 |
| End Condition | Plain cut, beveled, or capped | — |
| Packaging | Wooden pallet with moisture barrier; coil wrap (PP/PE film) | ISO 4180 |
4. Manufacturing Process
4.1 Process Flow
- Hot Rolling & Slab Preparation: Primary steelmaking via Basic Oxygen Furnace (BOF) or Electric Arc Furnace (EAF) with Vacuum Arc Remelting (VAR) or Argon Oxygen Decarburization (AOD) for alloy refinement.
- Cold Rolling (Reduction Rolling): Multi-stand cold rolling to achieve precise dimensional tolerances and improved surface quality.
- Intermediate Annealing: Solution annealing at 1050–1150°C followed by controlled cooling to restore ductility and dissolve carbides.
- Pipe Forming: Seamless tube production via piercing, plug rolling, and continuous tube mills; or welded tube via ERW (Electric Resistance Welding) with subsequent weld annealing.
- Precision Cold Drawing: Drawing through tungsten carbide dies to achieve final OD and wall thickness with tight tolerances.
- Final Annealing & Pickling: Solution treatment at 1040–1120°C, followed by acid pickling and passivation to establish the protective chromium oxide layer.
- Coiling: Continuous coiling onto precision-mandrel pay-off reels with controlled tension to prevent deformation or ovality.
- Quality Inspection & Packaging: Full-length eddy current testing, hydrostatic pressure testing, and dimensional verification prior to packaging.
4.2 Key Process Advantages
- Continuous coil supply eliminates field welding, reducing potential leak points by up to 95%.
- Controlled coiling tension preserves material grain structure and mechanical integrity.
- Precision cold drawing ensures uniform wall thickness critical for consistent heat transfer performance.
5. Applications
5.1 Primary Application Domains
- Thermal Energy Storage (TES): Ice-storage and hot-water storage systems where coil tubes serve as the primary heat transfer medium. Research has demonstrated that the coiled geometry enhances heat transfer coefficients by 20–40% compared to straight tubes due to secondary Dean vortex flow patterns.
- Heat Exchangers: Shell-and-tube, plate-fin, and spiral heat exchangers for HVAC, refrigeration, and industrial process cooling.
- Refrigeration & Air Conditioning: Evaporator and condenser coils for commercial and industrial refrigeration systems.
- Chemical Processing: Reactor cooling jackets, distillation column internals, and chemical heat transfer loops.
- Food & Pharmaceutical Industry: Pasteurization systems, CIP (Clean-in-Place) loops, and sanitary fluid transfer.
- Automotive & Aerospace: Intercooler tubes, hydraulic lines, and cryogenic fuel delivery systems.
- Building Services: Radiant heating/cooling floor systems, solar thermal collectors, and district heating networks.
5.2 Enhanced Heat Transfer Mechanism
Experimental studies on coil tube heat transfer have confirmed that the curvature-induced centrifugal force generates Dean vortices within the tube cross-section. These secondary flows continuously renew the thermal boundary layer, effectively disrupting the insulating fluid film near the tube wall. The resulting enhancement in convective heat transfer is quantified by the Nusselt number ratio (Nu_coil / Nu_straight), which typically ranges from 1.2 to 1.6 depending on the Reynolds number and coil curvature ratio (d/D, where d is tube diameter and D is coil diameter).
6. Quality Certifications & Compliance
6.1 Manufacturing Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management
- ISO/TS 22163 — Automotive Quality Management
6.2 Product Standards & Conformity
- ASTM A269 / ASME SA-269 — Seamless and Welded Austenitic Stainless Steel Tubes
- ASTM A312 / ASME SA-312 — Seamless and Welded Ferritic and Austenitic Cr-Ni Stainless Steel Tubing
- EN 10216-5 — Heat Exchanger Tubes (Stainless Steel)
- EN 10217-7 — Cold-drawn Stainless Steel Tubes for Technical Applications
- JIS G3459 — Seamless Stainless Steel Tubes for General Use
- GB/T 12771 — Chinese National Standard for Seamless Stainless Steel Tubes
6.3 Testing & Inspection Protocol
| Test Method | Standard | Frequency |
|---|---|---|
| Chemical Composition Analysis (Spark OES) | ASTM E135 | Per heat number |
| Tensile Test | ASTM A370 | Per lot |
| Hardness Test (Rockwell B) | ASTM E18 | Per lot |
| Hydrostatic Pressure Test | ASTM A269 §12 | 100% of production |
| Eddy Current Inspection | ASTM E309 | 100% of production |
| Intergranular Corrosion Test (ASTM A262 Practice E) | ASTM A262 | Per heat number |
| Pitting Corrosion Test (ASTM G48) | ASTM G48 | Per grade qualification |
| Dimensional Verification (OD, WT, Ovality) | ASTM A269 §10 | Per coil |
7. Unique Selling Points
- Enhanced Thermal Performance: The coiled geometry inherently promotes secondary flow patterns that boost heat transfer efficiency by 20–60% over equivalent straight tubes, validated by experimental research on coil tube thermal systems.
- Elimination of Field Welds: Continuous coil supply minimizes joint requirements, dramatically reducing the risk of leakage and corrosion at welded connections in critical service environments.
- Superior Corrosion Resistance: Multiple alloy grade options (304, 316L, 904L, 2205, 2507) accommodate a wide spectrum of corrosive media, from fresh water to seawater and aggressive chemical solutions.
- Precision Dimensional Accuracy: Cold-drawing process achieves tolerances as tight as ±0.05 mm on OD and ±0.025 mm on wall thickness, ensuring compatibility with precision-fitted headers and manifold systems.
- Full Traceability: Every coil is accompanied by a mill test certificate (MTC) with full chemical and mechanical data, enabling complete material traceability from steelmaking through final delivery.
- Cost-Efficient Installation: Coil form reduces installation labor by 40–60% compared to field-cut and field-welded straight pipe assemblies, with superior material yield rates.
- Research-Validated Design: Product development informed by peer-reviewed experimental research on coil tube ice storage and enhanced heat transfer, ensuring optimal geometric parameters for maximum thermal performance.
8. Ordering & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support for coil tube selection, including thermal performance calculations, compatibility assessments, and application-specific engineering guidance. Custom coil configurations, special alloy compositions, and non-standard dimensions are available upon request. Minimum order quantities and lead times vary by grade and specification; contact the sales engineering team for detailed quotations.