Stainless Steel Coil Tube (Coiltube) — Product No. 602
Product Overview
The Stainless Steel Coil Tube (Coiltube), designated as Product No. 602 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered continuous-length tubular product supplied in coiled form. This product category encompasses seamless and welded stainless steel tubes wound into coils, designed for versatile downstream applications including heat exchangers, fan coil units (FCU), HVAC (Heating, Ventilation, and Air Conditioning) systems, refrigeration, and industrial process piping.
The coil tube format provides significant logistical and manufacturing advantages over straight-length tube segments, enabling automated forming, cutting, and fabrication with minimal material waste. The product is manufactured in accordance with internationally recognized standards and is specifically suited for applications requiring corrosion resistance, thermal conductivity, and mechanical integrity under cyclic thermal and pressure loading conditions.
Material & Properties
Base Alloy Grades
- Austenitic Stainless Steels (奥氏体不锈钢): 304 (UNS S30400/S30403), 304L (UNS S30403), 316 (UNS S31600/S31603), 316L (UNS S31603), 321 (UNS S32100/S32101), 310S (UNS S31008)
- Ferritic Stainless Steels (铁素体不锈钢): 430 (UNS S43000), 409 (UNS S40900)
- Duplex Stainless Steels (双相不锈钢): 2205 (UNS S32205), 2507 (UNS S32750)
- Super-Austenitic Grades (超级奥氏体): 904L (UNS N08904), AL-6XN (UNS N08367)
Mechanical Properties (Typical — Annealed Condition, Grade 304)
- Tensile Strength (抗拉强度): ≥ 515 MPa (74,700 psi)
- Yield Strength (屈服强度): ≥ 205 MPa (29,700 psi)
- Elongation (延伸率): ≥ 40% (over 50 mm gauge length)
- Hardness (硬度): ≤ 230 HV (Brinell equivalent)
- Density (密度): 7.93 g/cm³
- Thermal Conductivity (热导率): 16.3 W/(m·K) at 300 K
- Specific Heat Capacity (比热容): 500 J/(kg·K) at 300 K
- Thermal Expansion Coefficient (热膨胀系数): 17.3 × 10⁻⁶ /K (10–100 °C)
- Electrical Resistivity (电阻率): 0.72 × 10⁻⁶ Ω·m at 20 °C
Corrosion Resistance
The high chromium (Cr ≥ 18%) and nickel (Ni ≥ 8%) content in austenitic grades provides excellent resistance to general atmospheric corrosion, oxidation at elevated temperatures (up to 870 °C for Grade 304, 1100 °C for Grade 310S), and pitting/crevice corrosion in chloride-containing environments (particularly Grade 316 with 2–3% Mo). The passive chromium oxide film (Cr₂O₃) self-repairs in oxidizing environments, ensuring long-term durability.
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ 3.0 mm – Φ 50.8 mm (1/8" – 2") | ASTM A213 / A269 |
| Wall Thickness | 0.3 mm – 3.0 mm (0.012" – 0.118") | ASTM A213 / EN 10216 |
| OD Tolerance | ±0.05 mm (±0.002") for OD ≤ 12.7 mm; ±0.10 mm for OD > 12.7 mm | ASTM A576 |
| Wall Thickness Tolerance | ±10% (or ±0.025 mm, whichever is greater) | ASTM A576 |
| Coil Inner Diameter (ID) | Φ 150 mm – Φ 300 mm (6" – 12") | Manufacturer Specification |
| Coil Length | 10 m – 100 m per coil (customizable) | Manufacturer Specification |
| Surface Finish | 2B (Cold Rolled & Annealed), BA (Bright Annealed), No. 4 Brushed, Mirror (8K) | ASTM A480 |
| End Condition | Open ends, welded ends, or closed ends (plug-welded) | ASTM A269 |
| Heat Treatment | Solution Annealed (1050–1150 °C) + Water Quenched | ASTM A213 |
| Packaging | Wooden pallet with moisture-proof wrapping; seaworthy export packing available | ISO 4126 |
Manufacturing Process
1. Raw Material Preparation
High-purity stainless steel wire rod (Wire Rod) conforming to ASTM A666 or JIS G4306 is procured and inspected for chemical composition via Spectrographic Analysis (光谱分析) and physical properties via tensile testing. The wire rod is subjected to acid pickling (酸洗) and descaling to remove surface oxides and scale formed during hot rolling.
2. Pipe Forming
The forming process follows one of two primary routes:
- Seamless Tube Production (无缝管): Hot-finished blank tubes are cold-drawn or cold-rolled through a series of dies (Plug Drawing / Cross-Rolling) to achieve the desired OD and wall thickness. This method produces tubes without longitudinal weld seams, offering superior pressure containment.
- Welded Tube Production (焊接管): Flat stainless steel strip (Strip) is slit, slit-edge trimmed, and formed into a tube shape through roll-forming stations. The longitudinal seam is welded using Automatic Submerged Arc Welding (SAW), TIG (Tungsten Inert Gas Welding), or Laser Welding. Post-weld Heat Treatment (PWHT) ensures weld microstructure homogeneity.
3. Heat Treatment (Solution Annealing)
The formed tube is solution-annealed at temperatures between 1050 °C and 1150 °C (depending on grade) in a protective atmosphere (Argon or Nitrogen), followed by rapid water quenching. This process dissolves precipitated carbides (particularly chromium carbides, Cr₂₃C₆), restores full austenitic microstructure, and maximizes corrosion resistance and ductility.
4. Cold Work & Sizing
After annealing, the tube undergoes cold sizing (Sizing) through calibrated rollers or dies to achieve final dimensional tolerances. Cold working introduces controlled work hardening (加工硬化), improving surface finish and dimensional accuracy. Intermediate annealing cycles may be employed for tubes requiring high elongation values.
5. Surface Finishing
- Pickling & Passivation (酸洗钝化): Hydrofluoric-nitric acid (HF-HNO₃) or citric acid pickling removes surface scale; subsequent passivation with nitric acid (HNO₃) or citric acid regenerates the chromium oxide passive film.
- Electropolishing (电解抛光): Optional process that removes surface contamination and impurities through electrochemical dissolution, achieving Ra ≤ 0.4 μm surface roughness.
- Brushing & Polishing: Mechanical finishing for aesthetic or functional surface requirements.
6. Coil Winding
The finished continuous-length tube is wound onto a coil core using a hydraulic or servo-controlled winding machine. The winding tension is precisely controlled to prevent ovality, kinking, or inter-coil contact damage. Each coil is labeled with product identification, heat number, and dimensional data.
7. Quality Inspection
- Hydrostatic Testing (水压试验): Each coil is pressure-tested at 2–5 times the maximum working pressure (per ASTM A269) to verify pressure integrity.
- Dimensional Inspection (尺寸检测): OD, wall thickness, and coil ID measured at multiple points using calibrated micrometers and ultrasonic thickness gauges.
- Chemical Analysis (化学成分分析): Spectrographic verification of Cr, Ni, Mo, C, Si, Mn, S, and P content per grade specification.
- Mechanical Testing (力学性能测试): Tensile tests, hardness testing, and impact tests (if applicable) conducted on coupon samples.
- Non-Destructive Testing (无损检测): Eddy Current Testing (ECT, 涡流检测) or Magnetic Particle Inspection (MPI, 磁粉检测) for surface defect detection; Ultrasonic Testing (UT, 超声波检测) for internal defect verification.
- Visual Inspection (外观检验): Surface examination for scratches, dents, discoloration, and other surface imperfections.
Applications
1. HVAC & Fan Coil Unit Systems (风机盘管系统)
Stainless steel coil tubes are integral components in Fan Coil Units (FCU, 风机盘管), where they serve as the refrigerant-side heat exchange tubes. The combination of high thermal conductivity, corrosion resistance to refrigerants (R-410A, R-32, R-134a, R-407C), and resistance to condensation-induced corrosion makes stainless steel coil tubes superior to traditional copper tubes in humid or corrosive environments. Research on Adaptive Energy-Saving Control Strategies for Fan Coil Units (风机盘管自适应节能控制策略) has demonstrated that stainless steel coil tubes maintain consistent heat transfer performance over extended operational cycles, contributing to overall system energy efficiency improvements of 15–25%.
2. Refrigeration & Air Conditioning
- Evaporator and condenser tube bundles
- Chilled water piping
- Heat recovery units
3. Food & Beverage Processing
- Pasteurization and sterilization piping (Grade 316L)
- CIP (Clean-in-Place) system tubing
- Milk processing equipment (Grade 304/316L, Ra ≤ 0.5 μm)
4. Chemical & Petrochemical Industry
- Process piping for corrosive media (acids, alkalis, chlorides)
- Heat exchanger tubes (Grade 316, 321, 904L)
- Distillation column internals
5. Medical & Pharmaceutical
- Sterilization equipment tubing (autoclave-compatible)
- Medical gas supply piping
- Cleanroom fluid transfer lines
6. Architectural & Decorative
- Handrails, balustrades, and structural elements
- Facade cladding supports
- Interior design features (mirror-finish coil tube)
7. Automotive & Transportation
- Exhaust system components (Grade 321, 409, 310S)
- Fuel system tubing
- Brake hydraulic lines
Quality Certifications & Standards Compliance
Applicable International Standards
- ASTM A213: Standard Specification for Seamless and Welded Austenitic Stainless Steel and Heat-Resisting Alloy Tubes for High-Temperature Service
- ASTM A269: Standard Specification for Seamless and Welded Austenistic Stainless Steel Tubes for Chemical and General Applications
- ASTM A576: Standard Specification for General Requirements for Seamless and Welded Stainless Steel Tubes
- EN 10216-5: Tubes for Heat Exchangers and Heat Sinks — Technical Delivery Conditions — Part 5: Austenitic and Austenitic-Ferritic Stainless Steel Tubes
- ISO 11497-2: Tubes for Heat Exchangers and Heat Sinks — Part 2: Austenitic and Austenitic-Ferritic Stainless Steel Tubes
- GB/T 12771: Stainless Steel Seamless Tubes for Fluid Transport (Chinese National Standard)
- JIS G3459: Stainless Steel Tubes for General Purposes (Japanese Industrial Standard)
Factory Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — European Conformity (PED 2014/68/EU for pressure equipment)
- PED Compliance — Pressure Equipment Directive (where applicable)
- Material Test Reports (MTR) — Full chemical and mechanical test documentation per ASTM E1013 (Spectrographic Analysis)
Unique Selling Points
1. Superior Corrosion Resistance: The austenitic stainless steel matrix with ≥ 18% Cr provides exceptional resistance to atmospheric