Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered continuous tube product wound into a compact coil configuration. This product is primarily designed for integration into Fan Coil Units (FCU) and other HVAC (Heating, Ventilation, and Air Conditioning) systems, as well as for applications in heat exchangers, refrigeration circuits, and industrial fluid transfer systems. The coil tube is supplied in a continuous, coiled form, minimizing waste and enabling efficient downstream processing such as cutting, bending, and brazing without requiring additional welding joints.
The product conforms to internationally recognized standards and addresses the critical requirements outlined in professional standards for fan coil unit components, including thermal efficiency, pressure resistance, corrosion durability, and dimensional accuracy. Wenzhou Jixing Metal Materials Co., Ltd leverages advanced metallurgical processing and continuous production capabilities to deliver coil tubes that meet or exceed industry benchmarks for performance and reliability.
2. Material & Properties
2.1 Base Material Grades
- 304 (UNS S30400 / AISI 304): Austenitic stainless steel with excellent general corrosion resistance, suitable for most HVAC and fluid handling applications.
- 316 (UNS S31600 / AISI 316): Austenitic stainless steel with added molybdenum (Mo), offering superior resistance to pitting and crevice corrosion in chlorinated environments.
- 316L (UNS S31603 / AISI 316L): Low-carbon variant of 316, providing enhanced weldability and resistance to intergranular corrosion.
- 321 (UNS S32100 / AISI 321): Titanium-stabilized austenitic stainless steel, offering improved high-temperature strength and resistance to sensitization.
2.2 Mechanical Properties
| Property | Specification |
|---|---|
| Tensile Strength (Ultimate) | ≥ 515 MPa (75 ksi) |
| Yield Strength (0.2% offset) | ≥ 205 MPa (30 ksi) |
| Elongation (at break) | ≥ 40% (minimum, per ASTM A213) |
| Hardness (Rockwell B) | ≤ 95 HRB (annealed condition) |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) (304 grade) |
| Thermal Expansion Coefficient | 17.3 × 10⁻⁶ /°C (20–100°C) |
| Maximum Operating Temperature | 870°C (304), 870°C (316), 900°C (321) |
| Minimum Operating Temperature | Cryogenic (down to −196°C / LN₂ temperature) |
2.3 Chemical Composition (Typical, wt%)
| Element | 304 | 316 | 321 |
|---|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.08 | ≤ 0.08 |
| Chromium (Cr) | 18.0–20.0 | 16.0–18.0 | 17.0–19.0 |
| Nickel (Ni) | 8.0–10.5 | 10.0–14.0 | 9.0–12.0 |
| Molybdenum (Mo) | — | 2.0–3.0 | — |
| Titanium (Ti) | — | — | 5×(C−0.02) to 0.70 |
| Sulfur (S) | ≤ 0.03 | ≤ 0.03 | ≤ 0.03 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A213 / GB/T 14976 |
| Wall Thickness | 0.3 mm – 3.0 mm | ASTM A213 / GB/T 14976 |
| Coil Diameter | 500 mm – 1,500 mm (adjustable) | Manufacturer Specification |
| Coil Length (per coil) | 100 m – 1,000 m (continuous) | Manufacturer Specification |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated | ASTM A240 |
| Dimensional Tolerance (OD) | ± 0.1 mm (for OD ≤ 10 mm); ± 0.15 mm (for OD > 10 mm) | ASTM A213 |
| Dimensional Tolerance (Wall) | ± 10% of nominal wall thickness | ASTM A213 |
| Maximum Working Pressure | 1.6 MPa – 4.0 MPa (depending on OD and wall thickness) | GB/T 14976 |
| Heat Treatment | Solution Annealing at 1050–1150°C followed by rapid cooling | ASTM A213 |
| Coil Form | Single-layer / Multi-layer coiled configuration | Manufacturer Specification |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection: Virgin stainless steel strip or seamless tube stock is procured from certified mills, with full chemical composition and mechanical property verification via spectroscopic analysis (OES / XRF).
- Continuous Drawing / Forming: The tube is drawn through precision tungsten carbide or hardened steel dies in a multi-stage reduction process to achieve the target outer diameter and wall thickness with tight dimensional tolerances.
- Intermediate Annealing: Periodic solution annealing is performed at temperatures between 1050°C and 1150°C to relieve work-hardening and restore ductility, ensuring uniform microstructure throughout the tube length.
- Precision Coiling: The finished tube is wound onto a precision coiler using tension-controlled systems to prevent ovalization, kinking, or surface damage during the coiling operation.
- Pickling and Passivation: The coiled tube is subjected to acid pickling (HNO₃ + HF blend) to remove oxide scales and surface contaminants, followed by passivation treatment to establish a protective chromium oxide film.
- Quality Inspection: Each coil undergoes comprehensive non-destructive testing (NDT), including ultrasonic testing (UT) for internal defects, eddy current testing (ECT) for surface and near-surface discontinuities, and hydrostatic pressure testing.
- Packaging: Coils are wrapped in moisture-proof protective film, secured with steel strapping, and labeled with heat number, specification, and traceability information.
4.2 Key Process Advantages
- Continuous Production: The coil form eliminates the need for butt welding, reducing failure points and improving system integrity.
- Minimal Material Waste: Coil supply reduces cutting losses by up to 30% compared to straight-length tube supply.
- Uniform Properties: Continuous annealing and controlled coiling ensure consistent mechanical properties along the entire tube length.
5. Applications
5.1 HVAC & Fan Coil Units (FCU)
The stainless steel coil tube is the core heat transfer element in fan coil units, where it serves as the refrigerant or hot water circuit. The coil tube's high thermal conductivity, corrosion resistance, and dimensional precision directly influence the thermal efficiency (COP) and service life of the FCU. Conformance with professional standards for fan coil unit design—addressing issues such as flow distribution uniformity, pressure drop optimization, and condensate management—is critical for system performance.
5.2 Additional Applications
- Refrigeration Systems: Evaporator and condenser tubes in commercial and industrial refrigeration equipment.
- Process Heat Exchangers: Shell-and-tube heat exchangers in chemical processing, pharmaceutical manufacturing, and food processing industries.
- Automotive Industry: Radiator tubes, intercooler tubes, and HVAC condenser tubes in automotive and commercial vehicle applications.
- Medical Equipment: Fluid transfer tubes in medical devices requiring biocompatibility and sterilizability.
- Food & Beverage Processing: Hygienic-grade tubing for CIP (Clean-in-Place) systems and pasteurization circuits.
- Oil & Gas Industry: Corrosion-resistant tubing for subsea manifolds and wellhead equipment.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices. |
| ASTM A213 / A269 | American Society for Testing and Materials standards for austenitic stainless steel seamless tubing. |
| ASME SA-213 / SA-269 | American Society of Mechanical Engineers specifications for heat exchanger tubing. |
| GB/T 14976 | Chinese National Standard for seamless stainless steel tubes for fluid conveyance. |
| EN 10216-5 | European Standard for seamless heat exchanger tubes of non-ferrous metals and steels. |
| GB/T 17395 | Chinese National Standard for technical requirements of seamless stainless steel tubes. |
| Pressure Vessel Certification | Compliance with applicable pressure vessel codes (ASME BPVC / GB 150) for high-pressure applications. |
| CE Marking | European Conformity marking for products sold within the European Economic Area. |
7. Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd differentiates its stainless steel coil tube products through the following competitive advantages:
- Professional Standard Compliance: Products are engineered with direct reference to professional standards for fan coil unit components, addressing critical performance parameters including heat transfer efficiency, pressure drop optimization, and long-term corrosion resistance in condensate environments.
- Full Traceability: Each coil is assigned a unique heat number and production batch identifier, enabling complete traceability from raw material mill certificate through final product delivery.
- Customizable Specifications: Flexible manufacturing capability allows customization of OD, wall thickness, coil diameter, and surface finish to meet specific OEM (Original Equipment Manufacturer) requirements.
- Integrated Quality Assurance: Multi-stage quality control including incoming material inspection, in-process monitoring, and final product certification ensures zero-defect delivery.
- Cost Efficiency: Continuous coil supply reduces fabrication labor costs, minimizes material waste, and accelerates production cycle times for downstream integrators.
- Sustainability Commitment: Production processes incorporate energy-efficient annealing furnaces, recycled cooling water systems, and environmentally responsible waste disposal practices in alignment with ISO 14001 requirements.