Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1706) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing product designed for demanding thermal-fluid transfer applications. This coil tube is specifically engineered for integration into column-mounted fan coil units (Column-Mounted Fan Coil Unit, CMFCU) and other HVAC (Heating, Ventilation, and Air Conditioning) systems, as well as industrial heat exchanger assemblies. The product is supplied in continuous coil form, enabling efficient downstream processing including cutting, bending, and welding without the need for seam splicing, thereby ensuring uniform metallurgical integrity throughout the entire tube length.
The coil tube construction provides superior thermal conductivity, excellent corrosion resistance, and mechanical durability, making it an ideal selection for environments where long-term reliability and hygiene are paramount. Wenzhou Jixing Metal Materials Co., Ltd leverages advanced coiling technology and rigorous quality control to deliver coil tubes that meet international standards for dimensional accuracy and surface finish.
2. Material & Properties
2.1 Base Material Grades
- Austenitic Stainless Steel: The primary material grades include SUS304 (UNS S30408) and SUS316L (UNS S31603), selected for their exceptional combination of corrosion resistance, formability, and weldability.
- Duplex Stainless Steel (optional): SUS32205 (UNS S32205) is available upon request for applications requiring elevated mechanical strength and resistance to stress corrosion cracking (SCC).
2.2 Mechanical Properties
- Tensile Strength (UTS, Ultimate Tensile Strength): ≥ 520 MPa (SUS304); ≥ 515 MPa (SUS316L)
- Yield Strength (0.2% offset): ≥ 205 MPa (SUS304); ≥ 170 MPa (SUS316L)
- Elongation (at fracture, A50): ≥ 40% (SUS304); ≥ 35% (SUS316L)
- Hardness: ≤ 95 HRB (annealed condition)
- Impact Energy (Charpy V-Notch, −40°C): ≥ 47 J (SUS316L)
2.3 Physical & Corrosion Properties
- Thermal Conductivity (at 20°C): 16.3 W/(m·K) (SUS304); 14.6 W/(m·K) (SUS316L)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C (SUS304); 16.0 × 10⁻⁶ /°C (SUS316L)
- Density: 7.93 g/cm³ (SUS304); 8.00 g/cm³ (SUS316L)
- Pitting Resistance (PREN, Pitting Resistance Equivalent Number): ≥ 19 (SUS304); ≥ 24 (SUS316L)
- Maximum Service Temperature: 870°C (SUS304); 870°C (SUS316L)
2.4 Chemical Composition (Typical, wt%)
| Element | SUS304 (UNS S30408) | SUS316L (UNS S31603) |
|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.03 |
| Si (Silicon) | ≤ 1.00 | ≤ 1.00 |
| Mn (Manganese) | ≤ 2.00 | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 |
| Cr (Chromium) | 18.00 – 20.00 | 16.00 – 18.00 |
| Ni (Nickel) | 8.00 – 10.50 | 10.00 – 14.00 |
| Mo (Molybdenum) | — | 2.00 – 2.50 |
| N (Nitrogen) | — | ≤ 0.10 |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Number | 1706 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Outer Diameter (OD) | 6.0 mm – 32.0 mm (customizable) |
| Wall Thickness (WT) | 0.40 mm – 2.00 mm |
| Coil Inner Diameter (CID) | 200 mm – 800 mm |
| Coil Length per Spool | 500 m – 3,000 m (continuous) |
| Surface Finish | 2B (Cold Rolled and Annealed), BA (Bright Annealed), No. 4 Brushed, Mirror (Ra ≤ 0.4 μm) |
| Coil Weight (per spool) | 300 kg – 1,500 kg |
| Dimensional Tolerance (OD) | ± 0.10 mm (standard); ± 0.05 mm (precision grade) |
| Dimensional Tolerance (WT) | ± 10% (standard); ± 5% (precision grade) |
| Roundness Tolerance | ≤ 10% of wall thickness |
| Hardness (Annealed) | ≤ 95 HRB |
| Delivery Condition | Annealed and Pickled (AP), Annealed and Bright Pickled (ABP) |
| Packaging | Wooden pallet with moisture-proof wrapping; export-grade packaging available |
| Standards Compliance | ASTM A269, ASTM A270, EN 10217-7, GB/T 12771, JIS G3459 |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorously controlled multi-stage manufacturing workflow to ensure dimensional precision, metallurgical homogeneity, and surface integrity:
- Raw Material Selection and Incoming Inspection: High-purity austenitic stainless steel strip is sourced from certified mills. Each batch undergoes spectrographic analysis (OES, Optical Emission Spectroscopy) to verify chemical composition compliance with the specified grade requirements.
- Slitting and Leveling: The master coil is slit to the required strip width using precision slitting lines with hydraulic tension control. The resulting strip is passed through a leveling mill to eliminate coil set and ensure flatness within ± 0.1 mm/m.
- Tube Forming (Cold Rolling): The leveled strip is fed into a multi-stand cold-rolling tube mill (typically 6–10 passes) where it is progressively rolled into a tubular cross-section. The forming process is conducted at ambient temperature to preserve the austenitic microstructure and avoid work-hardening-induced residual stresses.
- Seam Welding: The formed tube is welded along the longitudinal seam using TIG (Tungsten Inert Gas) welding or IG (Induction) welding, depending on the specified wall thickness. Inert gas shielding (Argon, Ar) is applied on both the inner and outer surfaces to prevent oxidation. The weld bead is subsequently ground or polished flush to achieve a smooth internal surface.
- Heat Treatment (Solution Annealing): The welded tube is passed through a continuous annealing furnace at temperatures between 1,050°C and 1,150°C under controlled inert atmosphere (Nitrogen, N₂, or Argon, Ar). This step dissolves carbide precipitates, relieves residual welding stresses, and restores full ductility and corrosion resistance.
- Pickling and Passivation: Following annealing, the tube undergoes acid pickling (typically a mixture of nitric acid and hydrofluoric acid) to remove scale and discoloration. A subsequent passivation treatment (dilute nitric acid, HNO₃, or citric acid) forms a stable chromium oxide (Cr₂O₃) passive film on the surface, enhancing corrosion resistance.
- Coiling: The finished tube is wound onto a precision coiling head to form the final coil configuration. The coiling process employs active tension control to prevent ovalization, kinking, or surface marking. The coil is then stabilized and trimmed to the specified length.
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Final Inspection and Testing: Every coil undergoes comprehensive quality verification including:
- Hydrostatic Pressure Testing (per ASTM A269): 1.5 × maximum working pressure, held for a minimum of 10 seconds.
- Dimensional Inspection: OD, wall thickness, roundness, and straightness measured at intervals of 10 m using ultrasonic and optical gauging systems.
- Surface Quality Assessment: Visual and dye penetrant inspection (DPI) for surface defects, weld bead integrity, and passivation uniformity.
- Corrosion Testing: Salt spray test (ASTM B117, NaCl 5% solution) for minimum 480 hours without pitting (SUS316L); 240 hours (SUS304).
- Chemical Re-verification: Sampling from each coil for laboratory confirmation of chemical composition.
- Packaging and Dispatch: Qualified coils are wrapped in moisture-proof polyethylene film, strapped with steel bands, and placed on export-grade wooden pallets. Each package is accompanied by a Mill Test Certificate (MTC, EN 10204 3.1) and a Certificate of Conformance (CoC).
5. Applications
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd is engineered for a wide spectrum of industrial and commercial applications, with particular emphasis on thermal-fluid transfer systems:
- HVAC Systems: Primary application in column-mounted fan coil units (CMFCU), ceiling-mounted fan coil units, and air handling units (AHU) where the coil tube serves as the heat exchange medium for chilled water, hot water, or glycol solutions.
- Industrial Heat Exchangers: Shell-and-tube heat exchangers, plate-fin heat exchangers, and compact air-to-water heat exchangers in petrochemical, pharmaceutical, and food processing industries.
- Refrigeration and Air Conditioning: Evaporators, condensers, and chiller coils in commercial and industrial refrigeration systems, where resistance to ammonia (NH₃) and refrigerant corrosion is critical.
- Water Treatment and Desalination: Seawater cooling coils, reverse osmosis (RO) pretreatment systems, and desalination plant heat recovery units, leveraging SUS316L's superior chloride resistance.
- Food and Beverage Processing: Heat exchangers for pasteurization, sterilization, and temperature control in dairy, brewing, and beverage manufacturing, where hygienic surface finish and corrosion resistance are mandatory (FDA-compliant).
- Pharmaceutical Manufacturing: Sanitary-grade heat transfer coils in cleanroom environments, CIP (Clean-In-Place) systems, and process temperature control loops requiring USP Class VI compliance.
- Automotive and Aerospace: Engine coolant loops, hydraulic system tubing, and thermal management components where lightweight, corrosion-resistant tubing is required.
- Power Generation: Feedwater heaters, condenser tubes, and boiler economizer coils in thermal power plants and combined heat and power (CHP) systems.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following international standards: