Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for thermal exchange, fluid conveyance, and structural applications across industrial, HVAC, and process engineering sectors. The coil tube is supplied in continuous coil form, enabling high-efficiency downstream forming, bending, and welding operations. This product is particularly suited for fan coil unit (FCU) assemblies, where acoustic performance — including noise measurement and application optimization — plays a critical role in system design. The coil geometry facilitates compact heat exchanger configurations while maintaining dimensional stability under thermal cycling.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades, primarily conforming to international material standards. The following properties characterize the material selection:
- Primary Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS321 (UNS S32100)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and marine environments due to chromium (Cr ≥ 18%) and nickel (Ni ≥ 8%) alloying
- Temperature Range: Operational capability from cryogenic temperatures (−196 °C) to 870 °C (SUS304) or 1100 °C (SUS321)
- Mechanical Properties: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
- Non-magnetic: Austenitic microstructure ensures non-magnetic behavior after cold working
- Weldability: Superior weldability with minimal distortion; compatible with TIG (Tungsten Inert Gas), MIG, and resistance welding processes
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.00 mm – 38.10 mm | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.50 mm – 3.00 mm | ASTM A269 / EN 10216-5 |
| Coil Length (Continuous) | 50 m – 500 m (customizable) | — |
| Coil Inner Diameter (ID) | 152 mm – 508 mm (6" – 20") | — |
| Surface Finish | Ba&E (2B), No.1 Pickled, Polish (Ra ≤ 0.4 μm) | ASTM A480 |
| Dimensional Tolerance | ±0.10 mm (OD); ±10% (Wall Thickness) | ISO 6508 |
| Weld Seam | AUT (Automatic Ultrasonic Testing) verified | ISO 17637 |
| End Condition | Plain end, Bevel-cut, or Threaded (optional) | — |
| Coil Packaging | Wooden reel / Steel reel with moisture-proof wrapping | ISO 4180 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage process ensuring dimensional accuracy and metallurgical integrity:
- Strip Sourcing: Cold-rolled stainless steel strip is procured from certified mills, with incoming inspection verifying chemical composition (per ASTM E415) and mechanical properties.
- Coiling & Forming: The strip is precisely coiled into a tube blank using high-precision coil winding equipment, maintaining controlled tension to prevent inter-coil contact damage.
- Welding (if applicable): Longitudinal weld seams are formed via high-frequency induction welding (HF welding) or TIG welding, with weld parameters optimized for penetration and minimal heat-affected zone (HAZ) distortion.
- Piercing & Sizing: Welded tube blanks pass through multi-stand rolling mills for diameter reduction and wall thickness calibration, achieving final dimensions within ±0.10 mm tolerance.
- Heat Treatment: Solution annealing at 1040–1120 °C followed by rapid water quenching restores full austenitic structure, relieves residual stresses, and maximizes corrosion resistance.
- Pickling & Passivation: The tube surface is treated with citric or nitric acid solutions to remove mill scale and form a stable chromium oxide passive film (minimum 10⁻⁶ g/cm² Cr₂O₃).
- Non-Destructive Testing (NDT): 100% inline inspection via eddy current (EC) and ultrasonic (UT) methods detects wall thickness variations, seam defects, and internal voids.
- Final Coiling & Packaging: Finished tubes are recoiled onto protective reels, wrapped in VCI (Vapor Corrosion Inhibitor) film, and secured for export-ready shipping.
Applications
The coil tube finds extensive application in the following domains:
- Fan Coil Units (FCU) & HVAC Systems: The primary application context. Coil tubes serve as heat exchange elements in fan coil units, where optimized geometry and material properties contribute to controlled airflow noise levels. Studies on noise measurement and application of fan coil unit assemblies demonstrate that precise tube dimensions and smooth surface finishes reduce aerodynamic turbulence, thereby lowering operational noise below 35 dB(A) at 1 meter distance.
- Heat Exchangers & Condensers: Evaporator and condenser coils for refrigeration, air conditioning, and process cooling systems.
- Food & Pharmaceutical Processing: Sanitary-grade coils (Ra ≤ 0.4 μm) for hygienic fluid transfer, pasteurization, and CIP (Clean-in-Place) compatible systems.
- Automotive & Marine: Radiator tubes, exhaust heat recovery systems, and marine condensers where corrosion resistance is paramount.
- Chemical & Petrochemical Industry: Process piping coils for handling aggressive media including acids, chlorides, and solvents.
- Building Services & Radiators: Tubular radiator coils and underfloor heating manifold coils.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains the following quality certifications and adheres to international standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and traceability
- ISO 14001:2015 — Environmental Management System, governing sustainable manufacturing practices
- EN 10204 3.1 / 3.2 — Third-party material test certificates available upon request
- Mill Test Reports (MTR): Full chemical analysis and mechanical test data provided per batch
- Product Standards Compliance: ASTM A213, ASTM A269, GB/T 12771, EN 10216-5, JIS G3459
- NDT Certification: Personnel certified to ISO 9712 Level II for ultrasonic and eddy current inspection
- Pressure Vessel Compatibility: Available in specifications meeting PED 2014/68/EU and ASME B31.3 requirements
Unique Selling Points
Acoustic Optimization for FCU Applications: Leveraging research findings on fan coil unit noise measurement, the coil tube's dimensional precision (±0.10 mm OD tolerance) and ultra-smooth surface finish (Ra ≤ 0.4 μm) minimize aerodynamic noise generation. This directly contributes to energy-efficient, low-noise thermal systems compliant with ISO 3741 and ISO 3745 acoustic measurement standards.
- Continuous Coil Supply: Eliminates butt welds inherent in straight-length tubes, reducing failure points and improving system reliability.
- Full Traceability: Each coil batch carries unique heat number identification with complete metallurgical documentation.
- Custom Dimensional Capability: Special OD, wall thickness, and coil length configurations available to meet OEM-specific thermal design requirements.
- Corrosion Performance: SUS316 grade option provides superior chloride pitting resistance (CPT ≥ 30 mV per ASTM G48) for marine and chemical applications.
- Supply Chain Reliability: Established long-term partnerships with major stainless steel mills ensure consistent material availability and competitive lead times.
Technical Support & Consultation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including thermal design consultation, material selection guidance based on service environment, and post-delivery quality assurance. Engineering teams are available to assist with noise performance optimization for fan coil unit integration, referencing applicable standards such as ISO 5136 (Acoustics — Determination of sound power levels of small sources) and EN 13053 (Acoustics — Sound power levels of fan coil units).