Stainless Steel Coil Tube (盘管) — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (Chinese: 盘管, English: Coil Tube / Coil Pipe) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. It is produced in continuous coil form, enabling efficient downstream processing including cutting, bending, welding, and forming. This product is specifically designed for use in Fan Coil Unit (FCU) systems — a critical component in modern building HVAC (Heating, Ventilation, and Air Conditioning) infrastructure. The coil tube serves as the heat exchange medium within fan coil systems, where thermal energy is transferred between a circulating fluid (water or refrigerant) and ambient air.
Wenzhou Jixing Metal Materials Co., Ltd. specializes in the production of high-grade stainless steel tubing products, adhering to international standards and delivering consistent quality for industrial and commercial applications. The coil tube product line is engineered to meet the demanding requirements of fan coil unit system modeling and control optimization, ensuring superior thermal performance, mechanical integrity, and long-term reliability under cyclic operating conditions.
2. Material & Properties
The stainless steel coil tube is fabricated from austenitic and ferritic stainless steel grades, selected for their exceptional combination of corrosion resistance, thermal conductivity, and mechanical strength. The primary material grades include:
- Austenitic Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS321 (UNS S32100) — offering excellent general corrosion resistance, high-temperature stability, and non-magnetic properties.
- Ferritic Grades: SUS430 (UNS S43000), SUS439 (UNS S43900) — providing good oxidation resistance at elevated temperatures and cost-effective performance for moderate-corrosion environments.
- Duplex Grades: SUS31803 (UNS S31803) — delivering enhanced yield strength and superior resistance to chloride-induced stress corrosion cracking (SCC).
Key Physical and Mechanical Properties
- Chemical Composition: Carbon (C) ≤ 0.08% (for 304 grade); Chromium (Cr) 18–20%; Nickel (Ni) 8–10.5% (for 304 grade); Molybdenum (Mo) 2–3% (for 316 grade).
- Tensile Strength: 515–730 MPa (depending on grade and temper condition).
- Yield Strength: ≥ 205 MPa (0.2% offset).
- Elongation: ≥ 40% (minimum, per ASTM A269).
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C.
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (at 20–100°C).
- Density: 7.93 g/cm³.
- Operating Temperature Range: −196°C to +870°C (grade-dependent).
3. Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A269 / EN 10217 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / JIS G3446 |
| Coil Length | Up to 500 m per coil (continuous) | Manufacturer standard |
| Coil Inner Diameter (ID) | 300 mm – 600 mm | Customizable |
| Surface Finish | No.1 Pickled, 2B Annealed, BA (Bright Annealed), Electropolished (Ra ≤ 0.4 μm) | ASTM A480 |
| Tolerance (OD) | ±0.05 mm (precision grade); ±0.1 mm (standard grade) | ISO 14612 |
| Tolerance (Wall) | ±10% of nominal | ASTM A269 |
| End Condition | Plain cut, beveled, or welded (for seamless loop) | Customer specification |
| Material Grades | SUS304, SUS304L, SUS316, SUS316L, SUS321, SUS430, SUS439, SUS31803 | ASTM A269 / EN 10217 / JIS G3446 |
| Heat Treatment | Annealed (Solution Annealed) at 1050–1150°C, followed by controlled cooling | ASTM A269 |
| Maximum Operating Pressure | Up to 4.0 MPa (grade and dimension dependent) | ASME B31.9 |
| Corrosion Resistance | Pitting Resistance Number (PREN) ≥ 19 (316L); ≥ 24 (Duplex 31803) | ISO 3659 |
| Packaging | Wooden pallet with moisture-proof wrapping; steel banding | ISO 4180 |
4. Manufacturing Process
The production of the stainless steel coil tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, microstructural integrity, and surface quality:
- Raw Material Selection and Incoming Inspection: Cold-rolled stainless steel strip (coil) is procured from certified mills. Incoming material undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition conformity with specified grades.
- Slitting: The master coil is slit into precise-width strip using a high-speed slitting line. Edge quality is maintained to prevent defects during the subsequent forming process.
- Forming (Seamless Tube Forming): The strip is fed into a multi-roller forming station where it is progressively shaped into a tubular profile. This continuous forming process ensures uniform wall thickness and tight dimensional tolerances.
- Welding: A high-frequency induction welding (HFIW) or laser welding process is applied to create a longitudinal seam. Weld parameters are continuously monitored to ensure full penetration and minimal heat-affected zone (HAZ).
- Inline Annealing: The welded tube passes through a controlled-atmosphere annealing furnace (hydrogen or nitrogen atmosphere) at 1050–1150°C. This step relieves welding residual stresses, restores austenitic microstructure, and achieves the required mechanical properties.
- Pickling and Passivation: The annealed tube is pickled in an oxidizing acid bath to remove surface scale, followed by passivation to restore the passive chromium oxide layer, ensuring optimal corrosion resistance.
- Surface Finishing: Optional electropolishing or mechanical polishing may be applied to achieve specified surface roughness (Ra values), critical for hygienic and high-heat-transfer applications.
- Dimensional Inspection: Online laser measurement systems verify OD, wall thickness, and roundness in real time. Non-conforming sections are automatically rejected.
- Coiling and Packaging: The inspected tube is wound onto a precision coiler to form a uniform coil. The coil is then wrapped, banded, and palletized for shipment.
5. Applications
The stainless steel coil tube is engineered for a wide range of industrial and commercial applications, with particular emphasis on thermal management systems:
- Fan Coil Unit (FCU) Systems: The primary application domain. The coil tube is formed into heat exchanger coils within fan coil units used in commercial buildings, hospitals, hotels, and data centers. The tube geometry is optimized for maximum heat transfer surface area while minimizing pressure drop, as validated through computational fluid dynamics (CFD) modeling and control system optimization studies.
- HVAC Heat Exchangers: Used in air handlers, chillers, condensing units, and radiant heating/cooling systems where corrosion resistance and thermal efficiency are paramount.
- Refrigeration and Cryogenic Systems: SUS304L and SUS316L grades are suitable for low-temperature applications down to −196°C, maintaining ductility and resistance to brittle fracture.
- Food and Pharmaceutical Processing: BA (Bright Annealed) and electropolished finishes meet FDA (Food and Drug Administration) and 3-A (Sanitary Standards) requirements for hygienic fluid conveyance.
- Chemical Processing: SUS316 and Duplex 31803 grades provide superior resistance to aggressive chemical media, chlorides, and acidic environments.
- Automotive and Aerospace: High-temperature grades (SUS321) are used in exhaust systems, fuel lines, and thermal management circuits requiring sustained performance above 600°C.
- Water Distribution and Desalination: Corrosion-resistant coil tubing for potable water systems and seawater desalination plants.
Unique Selling Points
- Thermal Performance Optimization: The coil tube geometry is designed with reference to fan coil unit system modeling and control optimization research, ensuring that the heat exchanger achieves target performance coefficients (COP — Coefficient of Performance) with minimal energy consumption.
- Precision Manufacturing: Tight tolerances (±0.05 mm OD) and consistent wall thickness ensure reliable crimping, brazing, and mechanical fitting during downstream assembly.
- Material Versatility: Availability in multiple stainless steel grades allows customers to select the optimal material for their specific operating environment, balancing cost, corrosion resistance, and mechanical requirements.
- Long Service Life: Inherent corrosion resistance eliminates the need for internal coatings or linings, reducing lifecycle maintenance costs and ensuring dependable operation over decades of service.
- Environmental Sustainability: Stainless steel is 100% recyclable. The coil format minimizes material waste during cutting and forming operations, reducing manufacturing carbon footprint.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers tailored specifications including custom OD, wall thickness, coil length, surface finish, and material grade to meet specific project requirements.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system aligned with international standards. The stainless steel coil tube product complies with the following certifications and standards:
| Certification / Standard | Scope | Applicable Reference |
|---|---|---|
| ISO 9001:2015 | Quality Management System (QMS) | Organization-wide |
| ISO 14001:2015 | Environmental Management System | Manufacturing operations |
| ISO 45001:2018 | Occupational Health and Safety Management | Production facilities |
| ASTM A269 / A270 | Standard Specification for Stainless Steel Tubular Products (Seamless, Welded, and Heavy-Walled) | Material and dimensional compliance |
| EN 10217-7 | Technical Delivery Conditions for Stainless Steel Tubes for General Purposes | European market compliance |
| JIS G3446 / G3447 | Stainless Steel Tubes for General Purposes | Japanese market compliance |
| GB/T 12771 | Chinese National Standard — Stainless Steel Tubes for General Purposes | Domestic market compliance |
| ASME B31.9 | Process Piping | Pressure vessel and piping applications |
| CE Marking | European Conformity | EU market access |
| Material Test Reports (MTR) | Mill certification with full chemical and mechanical property data | Per-heat-lot traceability |
| Third-Party Inspection | Available upon request (SGS, Bureau Veritas, TÜV) | Customer-specified projects |
Each production batch is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 Type 3.1, providing full traceability of chemical composition, mechanical properties, heat treatment records, and non-destructive testing (NDT) results. Available NDT methods include magnetic particle inspection (MPI), eddy current testing (ECT), and ultrasonic testing (UT) for weld seam integrity verification.
Note: The technical specifications and performance characteristics described herein are based on standard production configurations. Customized specifications, including non-standard dimensions, special surface treatments, or alternative material grades, may be available upon request. Wenzhou Jixing Metal Materials Co., Ltd. recommends consulting with their technical engineering team for project-specific material selection and design validation, particularly for applications involving extreme temperatures, high pressures, or aggressive chemical environments.