Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous coil of stainless steel tubing manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed for seamless integration into HVAC (Heating, Ventilation, and Air Conditioning) systems, heat exchanger assemblies, and industrial fluid transfer applications, this product delivers superior thermal conductivity, corrosion resistance, and structural integrity in a continuous coil configuration that maximizes material utilization and minimizes fabrication waste.
Rooted in the principles of Energy Efficiency Ratio (EER) optimization for fan coil units (FCUs), this coil tube product is specifically engineered to enhance the thermal exchange performance of downstream applications. The comprehensive evaluation of energy efficiency in fan coil unit systems has driven the development of coil tubes with optimized wall thickness profiles, tight dimensional tolerances, and surface finishes that reduce thermal resistance and fluid friction losses.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel grades, selected for their exceptional combination of mechanical strength, weldability, and resistance to oxidation and chemical attack.
- Primary Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), SUS321 (UNS S32100)
- Microstructure: Fully austenitic (Face-Centered Cubic — FCC), non-magnetic, solution-annealed
- Corrosion Resistance: Superior resistance to atmospheric corrosion, weak acids, alkaline solutions, and chloride environments (particularly with SUS316 due to 2.5–3.0% molybdenum content)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, providing efficient heat transfer in coil-based heat exchanger applications
- Mechanical Strength: Tensile strength ≥ 520 MPa (annealed condition); Yield strength ≥ 205 MPa
- Temperature Range: Operational service from −196°C (cryogenic) to +870°C (intermittent); continuous service up to +650°C
- Surface Finish: 2B (cold-rolled and bright annealed), BA (Bright Annealed), or polished (Ra ≤ 0.4 μm available on request)
3. Technical Specifications
| Parameter | Specification | Applicable Standard |
|---|---|---|
| Outer Diameter (OD) | Φ3.0 mm – Φ108.0 mm | GB/T 14976; ASTM A269 |
| Wall Thickness (WT) | 0.25 mm – 6.00 mm | GB/T 14976; EN 10216-5 |
| OD Tolerance | ±0.05 mm (standard); ±0.02 mm (precision grade) | ISO 1128 |
| WT Tolerance | ±10% of nominal (standard); ±5% (precision grade) | ASTM A213 |
| Coil Length (Continuous) | 15 m – 500 m per coil | Manufacturer specification |
| Coil Inner Diameter | 200 mm – 800 mm (customizable) | — |
| Coil Weight | 50 kg – 2,000 kg per coil | — |
| End Condition | Plain end, beveled end, or threaded end | ASME B1.20.1 (threaded) |
| Weld Type | Seamless or welded (TIG/Orbital) | GB/T 12771; ASME B31.3 |
| Heat Treatment | Solution annealing (1050–1150°C + water quench) | ASTM A269 |
| Maximum Operating Pressure | Up to 40 MPa (PN40) depending on geometry | EN 10216-5 |
| Hydrostatic Test | 1.5× maximum operating pressure, 30-second hold | GB/T 24511 |
4. Manufacturing Process
The production of Wenzhou Jixing's stainless steel coil tube follows a rigorously controlled multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical homogeneity, and surface integrity:
- Raw Material Selection: Ingot or billet sourcing from certified mills with full chemical composition verification via Optical Emission Spectroscopy (OES) and Inductively Coupled Plasma (ICP) analysis.
- Piercing & Reaming: Hot piercing of billets to produce seamless tube blanks, followed by reaming to achieve initial dimensional conformity.
- Hot Rolling / Cold Drawing: Tubes are either hot-rolled to near-final dimensions or cold-drawn through precision dies to achieve tight tolerances (±0.02 mm OD) and superior surface finish.
- Solution Annealing: Continuous furnace annealing at 1050–1150°C with rapid water quenching to dissolve carbides, restore full austenitic structure, and eliminate residual stresses.
- Pickling & Passivation: Immersion in mixed acid solution (HNO₃/HF) to remove oxide scale, followed by passivation to form a protective chromium oxide layer (Cr₂O₃).
- Coiling & Straightening: Tubes are coiled at controlled bending radii (minimum 5× OD) to prevent ovality and deformation, using CNC-controlled coiling machines with real-time dimensional monitoring.
- Quality Inspection: 100% hydrostatic testing, electromagnetic (Eddy Current) flaw detection, ultrasonic thickness measurement, and visual surface inspection per ASME BPV Section I requirements.
- Coating & Packaging: Inner coil protection with PE (Polyethylene) film or VCI (Vapor Corrosion Inhibitor) paper; outer wrapping with stretch film and steel banding for shipping integrity.
5. Applications
The coil tube configuration provides significant advantages in applications where continuous, kink-free tubing is required for automated forming, bending, and assembly operations:
- HVAC & Fan Coil Units: Primary application in the manufacture of air-coil heat exchangers for commercial and residential fan coil units. The coil tube's optimized geometry directly contributes to improved Energy Efficiency Ratio (EER) by maximizing surface area-to-volume ratio and minimizing pressure drop across the coil.
- Automotive Radiators & Condensers: Used in brazed aluminum heat exchanger assemblies and stainless steel radiator cores requiring high thermal cycling resistance.
- Food & Pharmaceutical Processing: Sanitary-grade coil tubes (SUS316L, Ra ≤ 0.4 μm) for CIP (Clean-In-Place) and SIP (Sterilization-In-Place) compatible fluid transfer systems.
- Chemical Processing: Resistance to aggressive chemical environments including sulfuric acid, nitric acid, and organic solvents at elevated temperatures.
- Oil & Gas Industry: Heat exchanger tubes and heat transfer coils for upstream and midstream processing facilities.
- Appliance Manufacturing: Heat exchanger coils for refrigerators, air conditioners, heat pumps, and water heaters.
- Marine & Offshore: Seawater cooling coils and condensate recovery systems where chloride pitting resistance is critical.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management infrastructure to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Union directives (PED 2014/68/EU for pressure equipment)
- EN 10204 3.1 — Material test certificates per European standard
- ASME "S" Stamp — Sectional certification for pressure vessel and piping components
- GB/T 14976 — Chinese national standard for seamless and welded stainless steel tubes
- Third-Party Inspection: Available upon request via SGS, Bureau Veritas, or TÜV Rheinland
7. Unique Selling Points
The integration of energy efficiency research into product design sets this coil tube apart from conventional offerings in the market.
- EER-Optimized Geometry: Wall thickness profiles and coil winding parameters are calibrated to minimize thermal resistance and fluid friction, directly improving the Energy Efficiency Ratio of downstream fan coil unit systems by an estimated 8–15%.
- Continuous Coil Delivery: Eliminates butt-weld joints inherent in straight-length tube supply, reducing leak points and improving system reliability in heat exchanger applications.
- Material Traceability: Full batch-to-batch chemical and mechanical property documentation with digital quality passport for each coil.
- Custom Coiling Parameters: Coil inner diameter, winding direction (left-hand/right-hand), and tension parameters can be customized to match customer-specific uncoiling equipment.
- Multi-Grade Capability: Single-source procurement of SUS304, SUS316, SUS321, and duplex grades (SUS2205) from one manufacturer reduces supply chain complexity.
- Export-Grade Packaging: Container-optimized coil packaging with moisture barrier protection ensures arrival condition integrity for international shipments.
8. Ordering Information
Customers are advised to specify the following parameters when placing orders:
- Stainless steel grade (e.g., SUS304, SUS316L)
- Outer diameter (OD) and wall thickness (WT) with required tolerance class
- Required coil length and coil inner diameter
- Surface finish requirement (2B, BA, or polished with Ra value)
- End condition (plain, beveled, or threaded per ASME B1.20.1)
- Applicable standard or specification (GB, ASTM, EN, ASME)
- Required certifications and inspection protocols
Wenzhou Jixing Metal Materials Co., Ltd — Engineering Excellence in Stainless Steel Coil Tube Solutions.