Stainless Steel Coil Tube — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a continuous, helically wound tubular product manufactured from austenitic stainless steel wire. Produced by Wenzhou Jixing Metal Materials Co., Ltd., this product is engineered to meet the rigorous demands of heat exchange, refrigeration, HVAC (Heating, Ventilation, and Air Conditioning), and industrial fluid transport applications. The coil tube configuration provides superior surface-area-to-volume ratios, making it an optimal choice for thermal management systems, including fan coil units (FCUs) and condenser/evaporator assemblies.
Drawing upon industry research such as the development and characterization of Fan Coil Unit Refrigeration Performance Test Benches, the design and material selection of this coiltube product have been validated against critical performance parameters including refrigeration capacity, thermal efficiency, pressure drop, and long-term corrosion resistance. The product embodies the convergence of advanced metallurgical processing and precision forming technology.
Material & Properties
The Coiltube is fabricated from high-purity austenitic stainless steel wire, with the following primary grades available:
- SAE 304 (UNS S30400): General-purpose grade offering excellent corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- SAE 316 (UNS S31600): Enhanced grade with 2–3% Molybdenum (Mo) addition for superior resistance to pitting and crevice corrosion in chloride-rich environments.
- SAE 321 (UNS S32100): Titanium-stabilized grade suitable for elevated-temperature service (up to 870°C) with reduced sensitization risk.
Mechanical Properties (Typical Values for 304 Grade)
| Property | Specification | Test Method |
|---|---|---|
| Tensile Strength (UTS) | ≥ 520 MPa | ASTM A269 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ASTM A269 |
| Elongation (A50) | ≥ 40% | ASTM A269 |
| Hardness (Brinell, HBW) | ≤ 217 | ASTM E10 |
| Density | 7.93 g/cm³ | — |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) | ASTM E1461 |
| Thermal Expansion (20–100°C) | 17.3 × 10⁻⁶ /°C | ASTM E228 |
Chemical Composition (Maximum Limits, wt%)
| Element | SAE 304 | SAE 316 | SAE 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), min 0.30 |
| Sulfur (S) | ≤ 0.03 | ≤ 0.03 | ≤ 0.03 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
Specifications
| Parameter | Specification | Remark |
|---|---|---|
| Product Code | 808 | Internal catalog number |
| Product Name | Stainless Steel Coil Tube (Coiltube) | Helical continuous tube |
| Outer Diameter (OD) | 3.0 mm – 25.0 mm | Customizable upon request |
| Wall Thickness | 0.3 mm – 1.5 mm | Tolerance: ±10% |
| Coil Diameter | 100 mm – 500 mm | Adjustable per application |
| Coil Length | 5 m – 100 m (continuous) | Spooled delivery |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated | Ra ≤ 0.8 μm (BA) |
| Delivery Condition | Soft Annealed / Half Hard / Hard Drawn | Per customer specification |
| Operating Temperature Range | −196°C to +870°C (321 grade) | Cryogenic to high-temperature service |
| Maximum Operating Pressure | Up to 4.0 MPa (design dependent) | Calculated per ASME B31.3 |
| Applicable Standards | ASTM A269, ASTM A554, EN 10216-5, GB/T 12771 | Multi-standard compliance |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorously controlled multi-stage manufacturing sequence:
- Wire Rod Preparation: Hot-rolled stainless steel wire rod is supplied from certified mills, undergoing incoming inspection for chemical composition (via Optical Emission Spectroscopy, OES) and mechanical properties.
- Wire Drawing: The rod is cold-drawn through a series of tungsten carbide (WC) dies to reduce diameter to the required tube blank dimensions. This process imparts beneficial strain hardening while maintaining dimensional accuracy within ±5% tolerance.
- Intermediate Annealing: Periodic solution annealing at 1050–1150°C in a protective atmosphere (nitrogen/hydrogen mixture) relieves accumulated cold work, restoring ductility for subsequent forming operations.
- Tube Forming (Spiral Winding): The drawn wire or pre-formed tube blank is helically wound around a mandrel using CNC-controlled coil forming equipment. The winding pitch, coil diameter, and spring-back are precisely controlled to ensure geometric consistency.
- Final Annealing & Pickling: The formed coil tube undergoes final solution annealing followed by acid pickling (HNO₃/HF mixture) and passivation to remove oxide scale and restore the passive chromium oxide film (Cr₂O₃), ensuring maximum corrosion resistance.
- Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification (laser micrometry), hydrostatic pressure testing (per ASTM A269, Section 13), and selective eddy current testing for wall thickness uniformity.
- Packaging & Delivery: Coils are wound onto steel spools, wrapped in protective film, and secured for transport. Each shipment is accompanied by a Mill Test Certificate (MTC) per EN 10204 Type 3.1.
Applications
The Stainless Steel Coil Tube is deployed across a wide spectrum of industrial and commercial applications:
- HVAC & Refrigeration Systems: Primary application in fan coil units (FCUs), air handler units (AHUs), and chiller evaporator/condenser coils. The high surface-area geometry facilitates efficient heat transfer between refrigerant and ambient air.
- Automotive Thermal Management: Used in intercooler cores, oil coolers, and battery thermal management systems for electric vehicles (EVs), leveraging the tube's fatigue resistance and formability.
- Food & Beverage Processing: Hygienic-grade (316L) coil tubes are employed in pasteurization heat exchangers, dairy processing equipment, and pharmaceutical fluid transfer systems, meeting FDA and EHEDG standards.
- Chemical & Petrochemical Industry: Corrosion-resistant coil tubing for chemical reactors, distillation columns, and heat recovery steam generators (HRSGs) handling aggressive process media.
- Cryogenic Applications: Due to the austenitic microstructure's retained ductility at low temperatures, the coil tube is suitable for liquid natural gas (LNG) transfer lines and cryogenic heat exchangers.
- Medical Equipment: Sterilizable coil assemblies for medical gas delivery systems and diagnostic imaging equipment cooling circuits.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System (QMS) certification covering all manufacturing operations.
- ISO 14001:2015 — Environmental Management System, demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- CE Marking — Conformity with European Pressure Equipment Directive (PED) 2014/68/EU for pressure-containing applications.
- EN 10204 Type 3.1 — Inspection certificates issued by authorized quality inspectors for each production lot.
- Material Test Reports: Full chemical analysis (OES), mechanical testing data, and non-destructive examination (NDE) reports provided per EN 10204.
- RoHS & REACH Compliance — Restriction of Hazardous Substances and Registration, Evaluation, Authorization and Restriction of Chemicals compliance for EU market access.
Unique Selling Points
1. Optimized Thermal Performance: The helical coil geometry maximizes heat transfer surface area per unit volume, achieving up to 30% higher thermal efficiency compared to straight-tube configurations in equivalent footprint applications.
2. Superior Corrosion Resistance: The austenitic stainless steel matrix, combined with a fully restored passive film (passivation treatment), provides excellent resistance to atmospheric, aqueous, and chemical corrosion without requiring additional protective coatings.
3. Cryogenic Capability: Retains full ductility and toughness at temperatures as low as −196°C (liquid nitrogen temperature), making it uniquely suited for LNG and cryogenic process applications where carbon steel alternatives would exhibit brittle fracture.
4. Continuous Spooled Delivery: The coil configuration eliminates butt-weld joints inherent in straight-tube assemblies, reducing leak points and installation time by up to 40% in heat exchanger manufacturing.
5. Full Traceability: Each production coil is traceable from raw material mill certificate through final product inspection, ensuring complete quality chain documentation for regulated industries.
Conclusion
The Stainless Steel Coil Tube (Product Code 808) represents a high-performance, multi-standard-compliant product engineered for demanding thermal management and fluid handling applications. Its combination of metallurgical excellence, geometric efficiency, and manufacturing precision positions it as a preferred solution in the HVAC, automotive, chemical, and cryogenic industries. Backed by Wenzhou Jixing Metal Materials Co., Ltd.'s certified quality infrastructure and supported by rigorous performance validation methodologies — including fan coil unit refrigeration performance testing protocols — this product delivers reliable, long-life service across a broad operating envelope.