Stainless Steel Coil Tube — Floor Radiant Cooling Coil (Item No. 679)
1. Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tube product designed specifically for floor radiant cooling and heating systems. This coil tube is fabricated from high-grade austenitic stainless steel and is supplied in continuous coiled configurations to facilitate seamless installation within underfloor distribution networks. The product has been validated through comprehensive floor coil tube refrigeration simulation analysis, ensuring optimal thermal performance, pressure resistance, and long-term structural integrity under both cooling and heating operational cycles.
Unlike conventional copper or PEX piping alternatives, stainless steel coil tubes offer superior resistance to microbial growth, chemical corrosion, and mechanical deformation, making them the preferred medium for high-performance radiant floor systems in commercial, industrial, and premium residential applications.
2. Material & Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel — Grade 304 (UNS S30400) and Grade 316 (UNS S31600)
- Chromium (Cr): 18.0% – 20.0% (Grade 304); 16.5% – 18.5% (Grade 316)
- Nickel (Ni): 8.0% – 10.5% (Grade 304); 10.0% – 14.0% (Grade 316)
- Molybdenum (Mo): ≤ 0.08% (Grade 304); 2.0% – 3.0% (Grade 316)
- Carbon (C): ≤ 0.08% (Grade 304); ≤ 0.08% (Grade 316)
2.2 Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (Grade 304); ≥ 515 MPa (Grade 316)
- Yield Strength (0.2% Offset): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 22 HRB (annealed condition)
- Operating Temperature Range: −196 °C to +450 °C
2.3 Physical Properties
- Density: 8.00 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20 °C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)
- Specific Heat Capacity: 500 J/(kg·K)
2.4 Corrosion Resistance
Both Grade 304 and Grade 316 exhibit excellent resistance to atmospheric corrosion, aqueous corrosion, and oxidation at elevated temperatures. Grade 316 provides enhanced resistance to chlorides, pitting, and crevice corrosion due to the addition of molybdenum, making it particularly suitable for coastal environments and systems utilizing treated water containing residual chlorine.
3. Specifications
| Parameter | Specification / Value | Standard Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Floor Radiant Coil) | — |
| Item No. | 679 | — |
| Material Grade | 304 / 316 / 316L | ASTM A269 / ASTM A270 |
| Outer Diameter (OD) | Φ 8.0 mm – Φ 25.4 mm (standard); custom available | ISO 6520 |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 |
| OD Tolerance | ±0.10 mm (standard); ±0.05 mm (precision) | EN 10217-7 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A269 |
| Surface Finish | BA (Bright Annealed) / 2B / No. 4 Brushed | ASTM A270 |
| Coil Diameter | Φ 200 mm – Φ 1,500 mm (configurable) | — |
| Coil Length | 15 m – 200 m per coil (continuous) | — |
| Working Pressure | ≤ 1.6 MPa (typical radiant system); up to 4.0 MPa (industrial) | EN 12828 |
| Bending Radius | ≥ 3 × OD (cold bending); ≥ 2 × OD (hot bending) | — |
| Hydrostatic Test Pressure | 1.5 × working pressure (minimum) | ASTM A269 |
| Heat Treatment | Solution Annealed (1050–1150 °C) + Water Quench | ASTM A269 |
| Traceability | Full heat number traceability per coil | ISO 9001 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection & Inspection: Ingot or continuous-cast strip from certified stainless steel mills, verified for chemical composition via Optical Emission Spectrometry (OES) and mechanical properties via tensile testing.
- Hot Rolling & Annealing: Billet or strip is hot-rolled to approximate dimensions and solution-annealed at 1050–1150 °C followed by controlled water quenching to achieve full austenitic microstructure and relieve residual stresses.
- Cold Drawing / Seamless Forming: The annealed strip undergoes cold forming through multi-pass roll forming or seamless extrusion to achieve precise OD and wall thickness tolerances. This cold working process enhances surface quality and dimensional accuracy.
- Intermediate Annealing: Periodic solution annealing cycles are performed during multi-pass cold working to prevent work hardening and maintain ductility for continued forming.
- Pipe Welding (if applicable): For welded coil tubes, precision TIG (Tungsten Inert Gas) welding is employed with continuous argon shielding on both inside and outside of the weld seam. Weld parameters are monitored in real time to ensure full penetration and consistent weld geometry.
- Final Annealing & Surface Finishing: A final solution anneal followed by controlled cooling achieves the target mechanical properties. The surface is then finished via pickling and passivation (for BA finish) or mechanical brushing (for No. 4 finish).
- Coiling: The continuous tube is wound onto precision coils with controlled tension to prevent distortion or kinking. Coil diameter and winding density are optimized for downstream handling and installation.
- Non-Destructive Testing (NDT): 100% eddy current testing (ECT) for wall thickness and surface defect detection; hydrostatic pressure testing at 1.5× working pressure for leak integrity verification.
- Final Inspection & Packaging: Dimensional verification via laser measurement systems; visual inspection of surface quality; protective packaging with desiccant and moisture barrier for corrosion prevention during transit.
4.2 Key Process Controls
- Real-time laser OD and wall thickness monitoring at each forming station
- Automated weld seam geometry inspection via inline vision systems
- Full heat number traceability from raw material through final coil packaging
- Calibrated NDT equipment with documented traceability to national standards
5. Applications
5.1 Floor Radiant Cooling Systems
The primary application domain validated through simulation analysis is floor radiant cooling (also known as Active Radiant Cooling Panels — ARCP). The stainless steel coil tube is embedded within concrete screed or composite floor panels to provide uniform surface cooling. Simulation studies have confirmed that stainless steel coil tubes deliver:
- Superior thermal conductivity compared to polymer alternatives, enabling faster response times to cooling demand
- Elimination of microbial growth within the piping (compared to copper systems), critical for indoor air quality (IAQ) compliance
- Resistance to scale formation and biofilm accumulation under continuous water circulation
- Long service life exceeding 50 years under proper installation conditions
5.2 Additional Application Domains
- Commercial HVAC: Underfloor heating and cooling in office buildings, shopping malls, and hotels
- Industrial Process Heating/Cooling: Heat exchanger coils, process fluid distribution, and chemical processing lines
- Food & Pharmaceutical: Sanitary process piping where corrosion resistance and cleanability are critical
- Marine & Offshore: Ballast water systems, bilge systems, and deck piping where chloride resistance is paramount (Grade 316L)
- Automotive: Radiator tubing, fuel lines, and exhaust components
- Renewable Energy: Solar thermal collector tubing and geothermal heat exchanger coils
6. Quality Certifications & Standards Compliance
6.1 Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European directives for pressure equipment and construction products
- EN 10204 — Type 3.1 mill certificates with third-party inspection
6.2 Applicable Standards
| Standard | Description |
|---|---|
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Applications |
| ASTM A270 | Standard Specification for Austenitic Stainless Steel Seamless, Welded, and Heavy-Walled Cold-Formed Pipe and Tubing |
| EN 10217-7 | Non-alloy and Alloy Steel Tubes for Mechanical and Thermal Purposes — Stainless Steel Tubes |
| ISO 6520 | Stainless Steel Tubes and Fittings — Dimensions and Tolerances |
| EN 12828 | Heating Systems in Buildings — Design of Water-Based Heating Systems |
| GB/T 12771 | Chinese National Standard for Stainless Steel Tubes for General Purposes |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport |
7. Unique Selling Points
- Simulation-Validated Performance: Each coil tube design has been verified through rigorous floor radiant cooling simulation analysis, ensuring predictable thermal behavior and optimal system efficiency before deployment.
- Full Traceability: Complete heat number traceability from raw material to finished coil, enabling recall management and quality accountability across the entire supply chain.
- Hygienic Design: Bright Annealed (BA) surface finish with Ra ≤ 0.5 μm provides a smooth, non-porous surface that inhibits bacterial adhesion — a critical advantage over copper and polymer alternatives in cooling applications.
- Extended Service Life: Austenitic stainless steel construction ensures resistance to fatigue cracking, stress corrosion cracking (in appropriate grades), and general corrosion, delivering a projected service life exceeding 50 years.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable OD, wall thickness, coil diameter, and length configurations to meet project-specific engineering requirements.
- Sustainability: Stainless steel is 100% recyclable without loss of material properties, supporting circular economy objectives and reducing lifecycle environmental impact.
8. Technical Support & Documentation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical documentation for each shipment, including:
- Mill test certificates (EN 10204 Type 3.1) with full chemical analysis and mechanical test results
- Dimensional inspection reports with laser measurement data
- NDT test reports (eddy current and hydrostatic)
- Heat treatment records with temperature-time curves
- Simulation