Stainless Steel Coil Tube — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coiled Tubing) is a precision-engineered continuous tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed to meet the rigorous demands of industrial, HVAC (Heating, Ventilation, and Air Conditioning), and fluid transport applications. The coil tube is supplied in a helically wound configuration, offering enhanced flexibility, space efficiency, and superior heat transfer performance compared to conventional straight-segment piping.
Integrating advanced metallurgical engineering with precision forming technology, this coil tube is compatible with next-generation Fan Coil Unit (FCU) Temperature Control Systems, enabling optimized thermal regulation in commercial and industrial environments. The product embodies the principles of energy efficiency, corrosion resistance, and long-cycle durability, making it an ideal solution for modern HVAC and process engineering applications.
2. Material & Properties
The stainless steel coil tube is fabricated from high-grade austenitic and duplex stainless steel alloys, selected to ensure optimal mechanical strength, corrosion resistance, and thermal conductivity across a wide operating temperature range.
2.1 Available Material Grades
- 304 / AISI 304 (1.4301): General-purpose austenitic stainless steel with excellent formability and resistance to atmospheric and mild chemical corrosion.
- 316 / AISI 316 (1.4401): Enhanced molybdenum-containing grade offering superior resistance to chloride-induced pitting and crevice corrosion.
- 316L / AISI 316L (1.4404): Low-carbon variant of 316, suitable for welded assemblies requiring resistance to sensitization during welding operations.
- 321 / AISI 321 (1.4541): Titanium-stabilized grade providing excellent resistance to intergranular corrosion at elevated temperatures (up to 870 °C).
- 304L / AISI 304L (1.4307): Low-carbon austenitic grade ideal for heavy cold forming and welding applications.
2.2 Key Mechanical Properties (Typical — 304 Grade)
- Tensile Strength (Ultimate): 515–730 MPa
- Yield Strength (0.2% Offset): ≥ 205 MPa
- Elongation (at Break): ≥ 40%
- Hardness (Brinell): ≤ 217 HB
- Operating Temperature Range: −196 °C to +870 °C
- Thermal Conductivity (20 °C): 14.9 W/(m·K)
- Specific Heat Capacity: 500 J/(kg·K)
2.3 Surface Finish Options
- 2B Finish: Standard cold-rolled surface with a matte appearance; suitable for general industrial applications.
- No. 4 Brushed Finish: Fine linear grain pattern; aesthetically pleasing for visible installations.
- Mirror Finish (8K): Highly polished surface with reflectivity ≥ 90%; ideal for decorative and hygienic applications.
- Pickle & Passivate (P&P): Chemically cleaned surface free of oxide scale, with a passive chromium oxide layer for maximum corrosion protection.
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Outer Diameter (OD) | 6.0 mm – 159.0 mm | ASTM A554 / EN 10217 |
| Wall Thickness (WT) | 0.30 mm – 6.00 mm | ASTM A554 / EN 10217 |
| Coil Inner Diameter (CID) | 200 mm – 1,200 mm | Manufacturer's Specification |
| Coil Length (per Roll) | 10 m – 300 m (customizable) | — |
| Material Grades | 304, 304L, 316, 316L, 321, 310S, Duplex 2205 | ASTM A240 / EN 10088 |
| Manufacturing Method | Seamless (Pierced & Pilgered) or Welded (ERW / TIG) | ASTM A554 / EN 10217-2 |
| Surface Finish | 2B, No.4 Brushed, Mirror (8K), Pickle & Passivate | ASTM A480 |
| Tolerance — OD | ±0.05 mm – ±0.20 mm (depending on size) | ISO 4893 / EN 10217 |
| Tolerance — Wall Thickness | ±10% of nominal | ASTM A554 |
| Coil Tolerance | ±5 mm on coil inner diameter | Manufacturer's Specification |
| Operating Pressure (Design) | Up to 40 MPa (grade-dependent) | ASME B31.3 / EN 13480 |
| Packaging | Wooden reel / steel drum with VCI (Vapor Corrosion Inhibitor) wrap | ISO 11607 |
| Standards Compliance | ASTM A554, EN 10217-1/2, ISO 4893, GB/T 12771 | — |
4. Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality. The process flow is outlined below:
- Raw Material Selection & Inspection: Ingot or slab material is sourced from certified mills. Incoming material undergoes 100% chemical composition analysis (spectrometric testing) and mechanical property verification per ASTM A240 and EN 10088 requirements.
- Hot Rolling / Forging: Billet material is heated to forging temperature (1,050–1,200 °C) and rolled or forged into a pre-tube blank with controlled dimensions and grain structure.
- Piercing & Pilgering (Seamless Process): The pre-tube is pierced through a mandrel to create a hollow cross-section, followed by pilger rolling to achieve precise wall thickness and outer diameter. Alternatively, welded tube processes (ERW — Electric Resistance Welding, or orbital TIG welding) are employed for specific size ranges.
- Heat Treatment (Solution Annealing): Tubes are annealed at 1,010–1,150 °C followed by controlled cooling (air or water quench) to restore full austenitic microstructure, relieve residual stresses, and ensure maximum ductility and corrosion resistance.
- Pickling & Passivation: Post-heat-treatment, tubes are pickled in mixed acid baths (HNO₃/HF) to remove oxide scale, followed by passivation to form a protective chromium oxide (Cr₂O₃) layer on the surface.
- Precision Cold Drawing / Expansion: For seamless tubes requiring tighter tolerances, cold drawing through a die and mandrel assembly achieves final dimensional accuracy within ±0.05 mm tolerance.
- Coiling / Winding: The finished tube is wound onto a precision-controlled coil winding machine, maintaining consistent tension to prevent deformation, kinking, or inter-coil contact damage. Coil inner diameter is maintained within ±5 mm tolerance.
- Final Quality Inspection: Each coil undergoes dimensional verification (laser OD gauge, ultrasonic wall thickness measurement), surface inspection (visual and automated), and optional non-destructive testing (NDT) including eddy current testing (per ASTM E709) and hydrostatic pressure testing (per ASTM A554).
- Packaging & Dispatch: Coils are wrapped with VCI (Vapor Corrosion Inhibitor) film, secured with steel strapping, and mounted on wooden reels or steel drums for safe international shipping.
5. Applications
The stainless steel coil tube is engineered for a broad spectrum of industrial and commercial applications, with particular relevance to HVAC and process engineering sectors:
- HVAC Systems & Fan Coil Units (FCU): The primary application domain. Coil tubes serve as heat exchanger elements in fan coil units, chiller condensers, evaporators, and air handling units. Their superior thermal conductivity and corrosion resistance enable efficient heat transfer in humid and chemically aggressive environments.
- Process Heat Exchangers: Used in shell-and-tube heat exchangers, plate-fin coils, and spiral wound heat exchangers for chemical processing, petrochemical, and power generation industries.
- Automotive & Aerospace HVAC: Lightweight, high-performance coil tubes for vehicle air conditioning condensers, evaporators, and thermal management systems.
- Food & Pharmaceutical Processing: Sanitary-grade coil tubes (316L, electropolished finish) for fluid transport, CIP (Clean-in-Place) systems, and thermal processing equipment where hygienic standards are critical.
- Marine & Offshore Applications: 316 and duplex stainless steel coil tubes for seawater cooling systems, ballast water handling, and desalination plant heat exchangers.
- Geothermal & Solar Thermal Systems: Coil tubes for geothermal heat exchange loops and solar thermal collector absorber tubes, exploiting the material's thermal stability and resistance to scaling.
- Refrigeration & Cryogenic Systems: Operating reliably from cryogenic temperatures (−196 °C) to high-temperature applications, with no risk of brittle fracture due to the austenitic crystal structure.
- Industrial Fluid & Gas Transport: Continuous coil supply reduces field welding requirements, minimizing leak points and installation time in long-run piping systems.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a rigorous quality management system ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- ISO/TS 22163 — Automotive quality management system certification for automotive-grade coil tube production.
- CE Marking (EU Conformity) — Compliance with European Pressure Equipment Directive (PED 2014/68/EU) for pressure applications.
- ASME / NB (National Board) Certification — For pressure vessel and piping components manufactured to ASME codes.
- Mill Test Certificates (MTC) per EN 10204 3.1/3.2 — Third-party witnessed inspection available upon request.
- NDT (Non-Destructive Testing) Reports: Eddy current testing, ultrasonic testing, and hydrostatic pressure test reports provided with each shipment.
- Material Traceability: Full heat-number traceability from raw material ingot through to finished coil, enabling complete supply chain auditability.
7. Unique Selling Points
Integrated Thermal Performance: The coil tube geometry provides a high surface-area-to-volume ratio, enhancing heat transfer efficiency by up to 30% compared to equivalent straight-tube configurations. This makes the product particularly suitable for integration with advanced FCU temperature control systems.
- Continuous Supply Advantage: Delivered in continuous coil form, eliminating the need for field splicing and reducing installation time and labor costs by up to 40%.
- Exceptional Corrosion Resistance: Available in 316/316L and duplex 2205 grades for aggressive chemical, marine, and chloride-rich environments.
- Wide Dimensional Range: OD from 6 mm to 159 mm with wall thicknesses from 0.30 mm to 6.00 mm, covering virtually all industrial heat exchanger and piping requirements.
- Precision Tolerances: Tight dimensional tolerances (±0.05 mm OD) ensure reliable press-fit and expansion fitting into tube sheets without secondary machining.
- Cryogenic to High-Temperature Capability: Austenitic grades maintain full ductility and toughness from −196 °C to +870 °C, with no risk of ductile-to-brittle transition.
- Custom Coiling Configuration: Coil inner diameter, length, and packaging tailored to customer-specific handling and installation requirements.
- Full Traceability & Third-Party Inspection: Complete material traceability with optional EN 10204 3.2 certified inspection for critical applications.