Stainless Steel Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered, continuously formed tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed for integration into Fan Coil Unit (FCU) air conditioning systems and other thermal exchange applications requiring high corrosion resistance, thermal conductivity, and mechanical durability. The coil tube is supplied in continuous coil form, enabling seamless downstream processing, cutting, and bending operations without introducing joint weaknesses or thermal discontinuities.
Unlike discrete pipe segments, the coil tube format eliminates the need for field welding at connection points, thereby significantly reducing the risk of thermal bridge formation and leakage points — two of the most prevalent failure modes identified in domestic fan coil unit systems. The continuous geometry ensures uniform wall thickness distribution and consistent hydraulic performance throughout the entire coil length.
Material & Properties
The coil tube is fabricated from premium-grade austenitic stainless steel, selected specifically for its exceptional balance of corrosion resistance, thermal conductivity, and mechanical strength under prolonged exposure to water, refrigerant solutions, and ambient humidity.
Primary Material Grades
- ASTM A269 / UNS S30408 (304) — General-purpose grade with excellent resistance to atmospheric and mild chemical corrosion; suitable for most HVAC and residential applications.
- ASTM A269 / UNS S31603 (316) — Enhanced molybdenum alloy offering superior resistance to chloride-induced pitting and crevice corrosion; recommended for coastal environments and aggressive chemical service.
- ASTM A269 / UNS S30403 (304L) — Low-carbon variant designed to minimize intergranular corrosion sensitivity during welding and high-temperature exposure.
Mechanical & Thermal Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength | ≥ 520 MPa (75,400 psi) | ASTM A269 / ASTM A312 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (29,730 psi) | ASTM A269 |
| Elongation (in 50 mm / 2 in.) | ≥ 35% | ASTM A269 |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) — 304 Grade | ASTM E1530 |
| Thermal Conductivity (at 20°C) | 14.6 W/(m·K) — 316 Grade | ASTM E1530 |
| Thermal Expansion Coefficient | 17.3 × 10⁻⁶ /°C | ASTM E228 |
| Density | 8.0 g/cm³ | — |
| Maximum Service Temperature | 870°C (continuous), 1100°C (intermittent) | — |
Specifications
| Parameter | Specification | Notes |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | Item No. 1051 |
| Outer Diameter (OD) | 6.35 mm, 9.52 mm, 12.7 mm, 15.88 mm, 19.05 mm (¼", ⅜", ½", ⅝", ¾") | Custom diameters available upon request |
| Wall Thickness | 0.5 mm – 1.5 mm | Tolerance: ±10% or ±0.05 mm, whichever is greater |
| Coil Width | 150 mm – 1,200 mm | Adjustable per customer requirement |
| Coil Length | Continuous coil; standard cut lengths of 3 m, 6 m, or custom | Supplied in protective coil packaging |
| Surface Finish | No. 4 Brushed, Mirror (8K), Satin, or Pickled & Passivated | Finish selection based on application |
| Inner Surface Roughness | ≤ 0.8 μm Ra | Hygienic grade available upon request |
| End Condition | Plain cut, beveled, or pre-formed | Per customer drawing |
| Pressure Rating | Up to 1.6 MPa (232 psi) — dependent on OD and wall thickness | Hydrostatic tested at 1.5× working pressure |
| Operating Temperature Range | −196°C to +600°C | Cryogenic to moderate thermal service |
| Standard Reference | ASTM A269 / A269M, ASTM A312 / A312M, ASME B36.19M | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality compliance:
- Raw Material Procurement & Inspection: Stainless steel strip is sourced from certified mills and subjected to incoming inspection for chemical composition (via optical emission spectroscopy, OES), mechanical properties, and surface defect screening.
- Strip Preparation & Annealing: The raw strip undergoes controlled annealing to relieve residual stresses and achieve the target mechanical softness for forming operations.
- Roll Forming / Seamless Tube Drawing: The strip is cold-formed into tubular geometry using precision-calibrated rolling dies. For smaller diameters, the seamless drawing process is employed to eliminate longitudinal seams entirely.
- In-Line Dimensional Inspection: Laser micrometry and ultrasonic wall thickness gauging are performed continuously during production to maintain dimensional tolerance within specified limits.
- Heat Treatment & Solution Annealing: The formed tube is solution-annealed at temperatures between 1,010°C and 1,150°C followed by controlled quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation: The tube surface is pickled to remove scale and oxides, then passivated with a citric or nitric acid solution to form a stable chromium oxide passive film, ensuring long-term corrosion protection.
- Coiling & Packaging: The finished tube is wound onto precision-mandrel coils, wrapped in protective film, and packed in moisture-resistant cartons or steel-encased drums to prevent mechanical damage and moisture ingress during transit.
Applications
The stainless steel coil tube is engineered for demanding thermal management and fluid transport applications. Key application domains include:
- Fan Coil Units (FCUs) & HVAC Systems: The primary application domain. The coil tube serves as the heat exchange element in air-side thermal transfer, where it circulates chilled or heated water to regulate indoor temperature and humidity. The continuous coil geometry maximizes heat transfer surface area per unit volume, directly addressing the common issue of insufficient heat exchange capacity identified in domestic FCU systems.
- Chilled Water & Hot Water Distribution: Used in secondary loop piping for central air conditioning systems, providing corrosion-resistant, long-life water circulation paths.
- Condenser & Evaporator Coils: Integral components in refrigeration and air conditioning compressors, where the tube undergoes cyclic thermal stress and exposure to refrigerant condensate.
- Industrial Process Cooling: Applicable in chemical processing, pharmaceutical manufacturing, and food-grade cooling systems where hygienic and corrosion-resistant tubing is mandated.
- Automotive Thermal Management: Utilized in intercooler and radiator assemblies requiring high thermal conductivity and lightweight construction.
- Domestic Water Heaters & Heat Exchangers: Employed in immersion coils and heat exchanger bundles for residential and commercial water heating applications.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and supply chain processes.
- ISO 14001 — Environmental Management System certification ensuring environmentally responsible production practices.
- ASTM A269 / A269M — Conformance to the standard specification for seamless and welded austenitic stainless steel tubing.
- ASTM A312 / A312M — Conformance to the standard specification for seamless austenitic stainless steel pipe.
- ASME B36.19M — Compliance with dimensional and pressure rating requirements for wrought austenitic stainless steel pipe and tube.
- EN 10216-5 — European standard for welded austenitic stainless steel tubes for general purposes.
- CE Marking — Conformity with European health, safety, and environmental protection standards.
Third-Party Inspection: Each production lot is accompanied by a Mill Test Certificate (MTC) and EN 10204 Type 3.1 Certificate, providing verified chemical composition, mechanical test results, and dimensional measurements. Independent third-party inspection agencies (e.g., SGS, Bureau Veritas, TUV Rheinland) may be engaged for pre-shipment verification upon customer request.
Unique Selling Points
- Seamless Continuous Geometry: Eliminates longitudinal weld seams, removing the primary source of corrosion initiation and mechanical failure in conventional welded tube systems. This directly mitigates the corrosion and leakage issues commonly reported in domestic FCU systems.
- Superior Thermal Performance: The austenitic stainless steel matrix provides reliable thermal conductivity while resisting fouling and scaling, ensuring consistent heat transfer efficiency over the product's service life.
- Extended Service Life: With proper maintenance, the coil tube offers a service life exceeding 20–25 years in HVAC applications, significantly outperforming carbon steel alternatives that are susceptible to rust and perforation within 5–8 years.
- Hygienic Surface Finish: The passivated inner surface with Ra ≤ 0.8 μm minimizes biofilm adhesion and bacterial colonization, making it suitable for potable water and food-grade applications without requiring additional internal coatings.
- Customization Flexibility: Wenzhou Jixing Metal Materials Co., Ltd. offers full customization of diameter, wall thickness, coil dimensions, and surface finish to meet specific OEM and project requirements, enabling direct integration into proprietary FCU and heat exchanger designs.
- Cryogenic and High-Temperature Capability: The material retains ductility and mechanical integrity across an extraordinary temperature range (−196°C to +600°C), making it suitable for cryogenic refrigeration and high-temperature industrial service without material degradation.