Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuously wound tubular product manufactured from high-grade austenitic stainless steel strip, supplied in coil form for downstream forming, cutting, and fabrication. This product is engineered to meet the rigorous demands of hydronic systems, HVAC (Heating, Ventilation, and Air Conditioning) applications, fan coil units, heat exchangers, and industrial process piping. The coil configuration ensures material continuity, minimizes weld joints, and facilitates automated coil-forming operations in high-throughput manufacturing environments.
Produced by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube product integrates metallurgical excellence with dimensional precision, offering consistent mechanical performance across the full coil length. The product is particularly suited for applications requiring resistance to corrosion, thermal cycling, and fluid transport under varying hydraulic conditions.
2. Material & Properties
2.1 Base Material Grades
The coil tube is manufactured from certified austenitic stainless steel grades, with the following primary options:
- AISI 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- AISI 316 (UNS S31600) — Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion
- AISI 316L (UNS S31603) — Low-carbon variant of 316, optimized for welding and resistance to intergranular corrosion
- AISI 321 (UNS S32100) — Titanium-stabilized grade for elevated-temperature service
2.2 Chemical Composition (Typical — AISI 304)
| Element | C | Si | Mn | P | S | Cr | Ni | N |
|---|---|---|---|---|---|---|---|---|
| Maximum (%) | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | — | — | 0.10 |
| Minimum (%) | — | — | — | — | — | 18.0 | 8.0 | — |
2.3 Mechanical Properties (Cold-Drawn Condition)
| Property | Specification | Standard Reference |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ASTM A213 / EN 10216-5 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ASTM A213 / EN 10216-5 |
| Elongation (A50) | ≥ 35 % | ASTM A213 / EN 10216-5 |
| Hardness (HBW) | ≤ 220 | ASTM A213 / EN 10216-5 |
| Density | 7.93 g/cm³ | — |
| Thermal Conductivity (20 °C) | 16.3 W/(m·K) | ASTM E1461 |
| Specific Heat Capacity (20 °C) | 502 J/(kg·K) | — |
| Thermal Expansion Coefficient (20–100 °C) | 17.3 × 10⁻⁶ /K | — |
2.4 Corrosion Resistance
The chromium-rich passive oxide layer (Cr₂O₃) formed on the surface provides inherent resistance to atmospheric, aqueous, and many chemical environments. AISI 316/316L grades, with their 2–3 % molybdenum content, demonstrate significantly enhanced resistance to chloride-induced pitting and crevice corrosion, making them suitable for marine, chemical processing, and pharmaceutical applications.
3. Specifications
| Parameter | Specification | Tolerance | Standard |
|---|---|---|---|
| Outer Diameter (OD) | 6.00 – 50.80 mm | ± 0.10 mm | ASTM A213 / EN 10216-5 |
| Wall Thickness (WT) | 0.50 – 3.00 mm | ± 10 % | ASTM A213 / EN 10216-5 |
| Coil Length | Up to 1,200 m (continuous) | — | Manufacturer standard |
| Coil Inner Diameter (ID) | 305 mm / 508 mm | ± 10 mm | — |
| Surface Finish | No. 4 Brushed / 2B / BA (Bright Annealed) / Mirror | — | ASTM A480 |
| Surface Roughness (Ra) | 0.4 – 1.6 μm (BA) / 0.05 – 0.2 μm (Mirror) | — | ASTM A480 |
| Maximum Operating Temperature | −196 °C to +870 °C (AISI 304/316) | — | ASTM A213 |
| Maximum Operating Pressure | Up to 16 bar (design-dependent) | — | EN 10216-5 |
| End Treatment | Open end / Welded cap / Flanged (on request) | — | — |
| Packaging | Wooden pallet with moisture-proof wrapping | — | ISO 4180 |
4. Manufacturing Process
The production of the stainless steel coil tube follows a precisely controlled multi-stage manufacturing sequence designed to ensure metallurgical integrity, dimensional accuracy, and surface quality:
- Hot Rolling (Hot-Rolled Coil Production) — Stainless steel slabs are reheated to approximately 1,150–1,250 °C and passed through tandem hot-rolling mills to reduce thickness to the target hot-rolled gauge. This establishes the initial grain structure and near-final cross-sectional dimensions.
- Pickling and Annealing (Pickling & Descaling) — The hot-rolled coil is subjected to acid pickling (HNO₃/HF blend) to remove scale and restore the passive chromium oxide layer. Subsequent annealing in a controlled-atmosphere continuous annealing line (CAL) relieves residual stresses and refines the microstructure to a fully austenitic condition.
- Cold Reduction (Cold Rolling) — The annealed hot-rolled coil is cold-rolled to achieve the final wall thickness and outer diameter specifications. Cold working introduces controlled strain hardening, improving mechanical strength while maintaining formability.
- Intermediate Annealing — For tubes requiring higher formability (e.g., thin-wall applications), intermediate annealing cycles are performed between cold-rolling passes to reset the strain state and prevent cracking during further deformation.
- Final Cold Drawing / Pipe Forming — The flat or semi-formed strip is wound and drawn through precision tooling (mandrel dies or roll-forming stations) to form the final tubular geometry. The continuous drawing process ensures uniform wall thickness and concentricity along the coil length.
- Final Annealing and Surface Treatment — The formed coil tube undergoes final solution annealing in a continuous protection-atmosphere furnace to restore full austenitic microstructure, eliminate cold-work hardening, and achieve the desired surface finish (2B, BA, No. 4, or Mirror).
- Quality Inspection and Testing — Each coil is subjected to comprehensive non-destructive testing (NDT) including ultrasonic testing (UT) for wall thickness verification, eddy current testing (ECT) for surface and near-surface defect detection, and hydrostatic pressure testing to verify internal integrity. Chemical composition is verified via optical emission spectroscopy (OES) or X-ray fluorescence (XRF) analysis.
- Coiling and Packaging — The finished coil tube is wound onto standardized cores, wrapped in moisture-proof film, and secured on wooden pallets for transport, in compliance with ISO 4180 packaging requirements.
5. Applications
The stainless steel coil tube is a versatile product serving a broad spectrum of industrial and commercial applications:
5.1 HVAC and Fan Coil Unit Systems
In fan coil unit (FCU) systems, the coil tube serves as the primary heat exchange element, facilitating thermal transfer between the refrigerant or hydronic fluid and the air stream. The continuous coil configuration enables efficient serpentine or zig-zag tube layouts within compact fan coil housings. The product's thermal conductivity and corrosion resistance ensure long-term performance under repeated thermal cycling and exposure to humid air environments. System modeling studies, including hydraulic condition analysis of fan coil unit systems, confirm that the uniform wall thickness and smooth internal surface of this coil tube contribute to predictable pressure drop characteristics and optimized flow distribution.
5.2 Heat Exchangers and Condensers
Used in shell-and-tube heat exchangers, condensers, evaporators, and plate-fin heat exchangers for industrial process cooling and heating applications.
5.3 Food and Beverage Industry
Compliant with FDA and EC 1935/2004 regulations, the coil tube is employed in sanitary piping, beverage processing lines, dairy equipment, and brewing systems where hygienic design and corrosion resistance are paramount.
5.4 Pharmaceutical and Biomedical Equipment
AISI 316L grade coil tubes are used in pharmaceutical processing equipment, bioreactors, clean room piping systems, and medical device manufacturing, where biocompatibility and resistance to sterilization (CIP/SIP) are critical.
5.5 Chemical and Petrochemical Processing
The corrosion-resistant properties of AISI 316/316L coil tubes make them suitable for handling aggressive chemical media, acids, and solvents in chemical processing plants, refineries, and wastewater treatment systems.
5.6 Marine and Offshore Applications
Used in seawater cooling systems, ballast water piping, and marine HVAC systems where resistance to chloride-induced corrosion is essential.
5.7 Architectural and Decorative Applications
Mirror-finish coil tubes are used in architectural railings, decorative trim, elevator interiors, and commercial display structures.
6. Quality Certifications and Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health and Safety Management System certification |
| EN 10204-3.1 | Inspection Certificate — full material traceability with third-party testing |
| EN 10216-5 | European standard for seamless and welded stainless steel tubes for pressure purposes |
| ASTM A213 | American standard for austenitic stainless steel seamless, welded, and heavy-wall tubes |
| ASTM A269 | American standard for austenitic stainless steel seamless and welded tubing |
| ASME B31.3 / B31.5 | Pressure piping code compliance for process and sanitary piping |
| NSF/ANSI 61 | Drinking water system components — health effects (food-grade applications) |
| 3-A Sanitary Standards | Dairy and food processing sanitary design compliance |
| Mill Test Certificate (MTC) | Provided with every shipment — chemical composition, mechanical properties, and dimensional verification |
7. Unique Selling Points
- Continuous Coil Configuration: Eliminates the need for butt-welding of individual tube lengths, reducing potential leak points and improving system integrity. The continuous coil enables automated coil-forming, cutting, and U-bend manufacturing, significantly reducing fabrication labor and cycle time.
- Metallurgical Consistency: Continuous annealing and cold-drawing processes ensure uniform microstructure and mechanical properties along the entire coil length, eliminating property variations associated with individual tube manufacturing.
- Superior Surface Quality: Bright Annealed (BA) and Mirror finish options provide smooth internal surfaces that minimize fouling, reduce hydraulic resistance, and facilitate cleaning in sanitary applications.
- Multi-Grade Availability: Full range of AISI 304, 316, 316L, and 321 grades available, allowing customers to select the optimal alloy for their specific corrosion, mechanical, and temperature requirements.
- Dimensional Precision: Tight tolerances on outer diameter (± 0.10 mm) and wall thickness (± 10 %) ensure reliable fit-up in heat exchanger tube sheets, flange connections, and brazing operations.
- Full Traceability: Every coil is accompanied by a Mill Test Certificate (MTC) per EN 10204-3.1, providing complete traceability from raw material mill to finished product, including chemical analysis, mechanical test results, and non-destructive testing reports.