Stainless Steel Coil Tube (Coiltube) — Industrial Heat Exchanger & Furnace Heating Element
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered, continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for high-temperature industrial heating, heat exchanger assemblies, and thermal transfer applications. Unlike straight seamless or welded pipes, coil tubes are formed into continuous helical or spiral configurations during the manufacturing process, eliminating the need for post-fabrication bending and significantly reducing thermal stress concentrations at joints.
This product line is particularly distinguished by its superior internal heat transfer characteristics, as demonstrated through rigorous research on water-jacket furnace heating coil tube thermal performance. The optimized geometry and material composition ensure efficient convective and conductive heat exchange, making it a critical component in process heating systems where thermal efficiency and reliability are paramount.
2. Material & Properties
2.1 Base Materials
- AISI 304 / 304L (UNS S30400 / S30403) — General-purpose austenitic stainless steel offering excellent corrosion resistance and formability
- AISI 316 / 316L (UNS S31600 / S31603) — Molybdenum-enhanced austenitic grade for superior resistance to pitting and crevice corrosion in aggressive environments
- AISI 310S / 310 (UNS S31008 / S31000) — High-temperature austenitic grade suitable for sustained service above 1000°C
- AISI 321 (UNS S32100) — Titanium-stabilized grade for resistance to intergranular corrosion at elevated temperatures
- AISI 347 (UNS S34700) — Niobium-stabilized grade for enhanced high-temperature strength and oxidation resistance
2.2 Key Mechanical & Thermal Properties
| Property | AISI 304 | AISI 316 | AISI 310S | Test Standard |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 | ASTM A213 / ASME SA-213 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 205 | ASTM A213 |
| Thermal Conductivity (W/m·K, 100°C) | 16.3 | 16.3 | 13.5 | ASTM E1461 |
| Thermal Conductivity (W/m·K, 500°C) | 21.5 | 21.5 | 21.9 | ASTM E1461 |
| Max. Continuous Service Temperature (°C) | 870 | 870 | 1150 | Manufacturer's Data |
| Coefficient of Thermal Expansion (10⁻⁶/°C, 20–800°C) | 17.3 | 17.3 | 18.5 | ASTM E1461 |
| Corrosion Resistance (Pitting, PREN) | 18–20 | 24–26 | 19–21 | ASTM G48 |
2.3 Chemical Composition (Typical, wt%)
| Grade | C | Cr | Ni | Mn | Mo | Ti | Nb |
|---|---|---|---|---|---|---|---|
| 304 | ≤ 0.08 | 18.0–20.0 | 8.0–10.5 | ≤ 2.0 | — | — | — |
| 316 | ≤ 0.08 | 16.0–18.0 | 10.0–14.0 | ≤ 2.0 | 2.0–3.0 | — | — |
| 310S | ≤ 0.08 | 19.0–22.0 | 24.0–26.0 | ≤ 2.0 | — | — | — |
| 321 | ≤ 0.08 | 17.0–19.0 | 9.0–12.0 | ≤ 2.0 | — | 5×C (min) | — |
| 347 | ≤ 0.08 | 17.0–19.0 | 9.0–13.0 | ≤ 2.0 | — | — | 10×C (min) |
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) — Item No. 1030 | Internal Catalog |
| Outer Diameter (OD) | Φ6 mm – Φ108 mm (custom sizes available upon request) | ASTM A213 / ASME SA-213 |
| Wall Thickness | 0.3 mm – 8.0 mm | ASTM A213 / GB/T 13296 |
| Coil Diameter (Coiling Diameter) | Φ300 mm – Φ2000 mm (configurable) | Manufacturer's Specification |
| Tube Length (per coil) | 50 m – 500 m (continuous coil; custom lengths available) | ASTM A213 |
| Tolerance on OD | ± 0.10 mm (precision grade); ± 0.15 mm (standard grade) | ASTM A213 / ASME SA-213 |
| Tolerance on Wall Thickness | ± 10% of nominal (standard); ± 5% (precision grade) | ASTM A213 |
| Surface Finish | Mill finish, polished (Ra ≤ 0.4 μm), electropolished (Ra ≤ 0.25 μm), hairline finish | ASTM A240 / GB/T 14977 |
| Heat Treatment Condition | Annealed and Pickled (Solution Annealed) | ASTM A213 |
| Manufacturing Process | Continuous Cold Drawing / Cold Forming (Columbus Process) | ASTM A213 |
| End Condition | Plain ends, cut ends, or custom-fabricated connections | Per Customer Specification |
4. Manufacturing Process
The production of stainless steel coil tubes by Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous, multi-stage continuous manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and superior heat transfer performance:
- Raw Material Selection: High-purity stainless steel ingots or wire rod are sourced from certified mills, with full traceability of chemical composition and mill test certificates (MTC) in accordance with EN 10204 Type 3.1.
- Continuous Cold Drawing (Columbus Process): The stainless steel wire rod is continuously drawn through a series of precision-die reduction stations, progressively reducing the diameter while maintaining the continuous coil configuration. This eliminates longitudinal seams and ensures uniform microstructure throughout the tube length.
- Intermediate Annealing: Periodic annealing cycles are performed at controlled temperatures (typically 1050–1150°C) to relieve accumulated cold work strain, restore ductility, and prevent cracking during subsequent drawing operations.
- Pickling and Passivation: Each annealing cycle is followed by acid pickling (nitric-hydrofluoric acid blend) to remove scale and oxidation, followed by passivation to establish a protective chromium oxide layer on the surface.
- Final Coiling: The finished tube is coiled onto precision-wound reels at controlled tension to prevent deformation, kinking, or surface damage. Coil diameter is selected based on the tube's OD, wall thickness, and intended downstream forming requirements.
- Internal Quality Inspection: Ultrasonic testing (UT) and eddy current testing (ECT) are performed on 100% of production to detect internal voids, inclusions, and wall thickness variations.
- Final Testing: Hydrostatic pressure testing (at 1.5× working pressure, minimum 30 seconds hold time) and dimensional verification per ASTM A213 requirements.
5. Applications
The stainless steel coil tube is a versatile component deployed across a broad spectrum of industrial applications, with particular emphasis on thermal management systems:
5.1 Industrial Heating & Furnace Systems
- Water-Jacket Furnace Heating Elements: The coil tube serves as the primary heating medium within water-jacket furnaces, where optimized internal convective heat transfer characteristics enable efficient thermal energy distribution. Research on internal heat transfer coefficients (h) within these coils demonstrates that the helical geometry induces secondary Dean flow, enhancing the Nusselt number (Nu) by 20–40% compared to straight tube configurations under identical Reynolds number conditions.
- Industrial Oven Burners and Heat Exchangers
- Boiler Tubing and Superheater Coils
- Thermal Oil Heater Circulation Coils
5.2 Chemical & Petrochemical Processing
- Reactor jacket tubing and heat exchange coils
- Distillation column reboilers and condensers
- Corrosive fluid transfer and process heating lines
5.3 Food & Pharmaceutical Industry
- Pasteurization and sterilization heat exchanger coils (304L/316L grades)
- Hygienic-grade product transfer lines with electropolished surfaces
- CIP (Clean-in-Place) compatible process tubing
5.4 Power Generation
- Condenser tubes in power plant heat exchangers
- Steam generator coil elements
- Waste heat recovery system tubing
5.5 HVAC & Refrigeration
- Chiller evaporator and condenser coils
- Air conditioning heat exchanger elements
- Heat pump tubing assemblies
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management systems and certifications ensuring product conformity with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering manufacturing, inspection, and delivery processes |
| ISO 14001:2015 | Environmental Management System certification |
| ASTM A213 / ASME SA-213 | Standard specification for seamless austenitic stainless steel tubes for high-temperature service |
| ASTM A269 | Standard specification for seamless and welded austenitic stainless steel tubes for general service |
| GB/T 13296 | Chinese national standard for seamless stainless steel tubes for general purposes |
| EN 10217-7 | European standard for stainless steel tubes for pressure purposes |
| EN 10204 Type 3.1 | Inspection document — Test report with chemical composition and mechanical test results |
| Mill Test Certificate (MTC / EN 10204 3.1) | Provided with every shipment, detailing heat number, chemical analysis, mechanical properties, and dimensional compliance |
7. Unique Selling Points
- Enhanced Internal Heat Transfer Performance: The helical coil geometry inherently generates Dean secondary flow patterns within the tube, disrupting the thermal boundary layer and increasing the convective heat transfer coefficient (h) by 20–40% over equivalent straight-tube configurations. This is a well-documented advantage validated through computational fluid dynamics (CFD) simulations and empirical research on water-jacket furnace heating coil tube thermal characteristics.
- Seamless, Continuous Construction: The Columbus-process cold drawing method produces truly seamless tubes with no longitudinal or circumferential welds, eliminating potential leak paths and corrosion initiation sites — a critical advantage in high-pressure and high-temperature service.
- Elimination of Post-Forming Stress: Since the coil geometry is achieved during the continuous drawing process, the tube avoids the residual stress concentrations and potential work-hardening associated with post-fabrication cold bending of straight pipe sections.
- Wide Range of