Stainless Steel Coil Tube (Coiltube) — Medium-Temperature Air-Cooled Coil Performance Series
Product Code: JX-CT-457 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司) | Category: Literature Study & Performance Analysis Series
1. Product Overview
The JX-CT-457 Stainless Steel Coil Tube is a precision-engineered coiled tubular product specifically designed for medium-temperature air-cooled coil (Medium-Temperature Air-Cooled Coil Unit) applications in HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial heat exchangers, and process cooling circuits. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents the culmination of extensive performance analysis research, including the comprehensive study titled "Performance Analysis of Medium-Temperature Air-Cooled Coil Tubes", which validated the thermal efficiency, mechanical durability, and long-term reliability of coiled stainless steel tubing under sustained medium-temperature operating conditions.
The coil tube is supplied in continuous coil form (Coil Form), enabling seamless integration into automated manufacturing lines for fin-and-tube heat exchangers, refrigeration condensers, evaporator assemblies, and process heat transfer systems. The coiled configuration minimizes material waste, reduces cutting losses, and facilitates high-speed tube insertion into fin stacks, making it an ideal choice for high-volume production environments.
2. Material Composition & Properties
2.1 Base Material Grades
- Austenitic Stainless Steel (奥氏体不锈钢): Primary grades include SUS304 (UNS S30408) and SUS316 (UNS S31608), selected for superior corrosion resistance, formability, and thermal stability in medium-temperature environments.
- Duplex Stainless Steel (双相不锈钢): Optional grades such as SUS316L (UNS S31603) for enhanced resistance to chloride-induced pitting and crevice corrosion in aggressive service conditions.
- High-Nickel Austenitic Grades: SUS321 (UNS S32103) and SUS347 (UNS S34700) available for elevated-temperature applications requiring stabilization against intergranular corrosion.
2.2 Mechanical Properties
| Property | SUS304 (UNS S30408) | SUS316 (UNS S31608) | SUS316L (UNS S31603) |
|---|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa | ≥ 515 MPa | ≥ 485 MPa |
| Yield Strength (屈服强度, 0.2% offset) | ≥ 205 MPa | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (延伸率) | ≥ 40% | ≥ 40% | ≥ 45% |
| Hardness (硬度) | ≤ 217 HB | ≤ 217 HB | ≤ 217 HB |
| Thermal Conductivity (热导率, at 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | 14.6 W/(m·K) |
| Specific Heat (比热容, at 20°C) | 0.50 J/(g·K) | 0.48 J/(g·K) | 0.48 J/(g·K) |
| Operating Temperature Range (使用温度范围) | −196°C to +870°C | −196°C to +870°C | −196°C to +870°C |
2.3 Chemical Composition (Typical, wt%)
| Element | C (Carbon) | Cr (Chromium) | Ni (Nickel) | Mn (Manganese) | Si (Silicon) | Mo (Molybdenum) | P (Phosphorus) | S (Sulfur) |
|---|---|---|---|---|---|---|---|---|
| SUS304 | ≤ 0.08 | 18.0–20.0 | 8.0–10.5 | ≤ 2.0 | ≤ 1.0 | — | ≤ 0.045 | ≤ 0.030 |
| SUS316 | ≤ 0.08 | 16.0–18.0 | 10.0–14.0 | ≤ 2.0 | ≤ 1.0 | 2.0–3.0 | ≤ 0.045 | ≤ 0.030 |
| SUS316L | ≤ 0.03 | 16.0–18.0 | 10.0–14.0 | ≤ 2.0 | ≤ 1.0 | 2.0–3.0 | ≤ 0.045 | ≤ 0.030 |
3. Product Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD, 外径) | Φ6.00 mm – Φ25.40 mm (custom sizes available) | ASTM A213 / ASTM A269 |
| Wall Thickness (壁厚) | 0.30 mm – 1.50 mm | GB/T 14976 / GB/T 12771 |
| Coil Inner Diameter (盘管内径) | Φ500 mm – Φ1200 mm | Manufacturer Specification |
| Coil Length (盘管长度) | 100 m – 1000 m (continuous coil) | Custom per order |
| Surface Finish (表面状态) | No. 4 Brushed, Mirror (8K), Matte, or Pickled & Passivated | ASTM A480 |
| Surface Roughness (表面粗糙度, Ra) | ≤ 0.8 μm (standard); ≤ 0.2 μm (mirror finish) | ISO 1302 |
| Roundness (圆度) | ≤ 0.5% of OD | GB/T 14976 |
| Wall Thickness Tolerance (壁厚公差) | ± 10% of nominal | ASTM A269 |
| OD Tolerance (外径公差) | ± 0.10 mm (for OD ≤ 12.7 mm); ± 0.15 mm (for OD > 12.7 mm) | ASTM A269 |
| Heat Treatment (热处理) | Solution Annealed (固溶处理) + Water Quenched | ASTM A213 |
| Coil Weight (盘管重量) | 50 kg – 800 kg per coil (depending on dimensions) | — |
| Packaging (包装) | Wooden pallet with plastic wrap, moisture-proof film, and desiccant | ISO 4180 |
4. Manufacturing Process
The production of JX-CT-457 Stainless Steel Coil Tubes follows a rigorous, multi-stage manufacturing process adhering to international standards for seamless stainless steel tubing:
- Raw Material Selection & Inspection (原材料筛选与检验): Cold-rolled stainless steel strip (冷轧不锈钢带) is procured from certified mills and subjected to spectroscopic analysis (光谱分析) to verify chemical composition compliance with the specified grade. Each batch undergoes ultrasonic testing (UT) for internal defect detection.
- Coil Forming / Tube Rolling (卷管成型): The cold-rolled strip is fed through precision forming rolls (成型辊) to create a continuous tubular shape. The forming process is controlled to maintain dimensional accuracy and minimize work hardening effects.
- Welding (焊接): For welded coil tubes, the formed strip is welded using Continuous Welding (连续焊接) or High-Frequency Induction Welding (高频感应焊接) technology. Weld seam quality is verified by Helium Leak Testing (氦气泄漏检测) at a sensitivity of ≤ 1×10⁻⁹ Pa·m³/s. For seamless variants, Hot Rolling (热轧) or Piercing & Extrusion (穿孔与挤压) processes are employed.
- Pipe Milling & Finishing (管坯加工与精整): The coiled tube undergoes Calibration (定径) through precision sizing rolls to achieve exact OD and wall thickness tolerances. Surface finishing may include Grinding (研磨), Polishing (抛光), or Electropolishing (电解抛光) depending on the required surface quality.
- Solution Annealing (固溶处理): The coil tube is heat-treated at 1050°C – 1150°C followed by rapid water quenching to dissolve carbides, restore full austenitic microstructure, and maximize corrosion resistance. This step is critical for preventing sensitization (敏化) and intergranular corrosion (晶间腐蚀).
- Pickling & Passivation (酸洗与钝化): A controlled acid bath (typically nitric acid + hydrofluoric acid mixture) removes oxide scale, followed by passivation treatment to form a protective chromium oxide film (Cr₂O₃) on the surface.
- Quality Control & Testing (质量控制与检测): Every coil undergoes comprehensive testing including Dimensional Inspection (尺寸检测), Hydrostatic Testing (水压试验), Visual Inspection (目视检测), and Corrosion Testing (腐蚀试验) (including salt spray testing per ASTM B117).
- Coiling & Packaging (盘卷与包装): The finished tube is wound onto a coil using a tension-controlled coiler to prevent deformation, then packaged for shipping with protective wrapping and moisture barriers.
5. Performance Analysis — Medium-Temperature Air-Cooled Coil Applications
Based on the referenced study "Performance Analysis of Medium-Temperature Air-Cooled Coil Tubes" (《中温水风机盘管的性能分析》), the following performance characteristics have been validated for the JX-CT-457 coil tube in medium-temperature air-cooled coil (中温水风机盘管) service:
5.1 Thermal Performance
- Heat Transfer Coefficient (传热系数): The stainless steel coil tube achieves an overall heat transfer coefficient (U-value) of 60–120 W/(m²·K) in typical air-to-water medium-temperature coil configurations, with performance optimized through precise tube-fin contact resistance management.
- Thermal Conductivity Advantage: While stainless steel has lower thermal conductivity than copper, the JX-CT-457 compensates through optimized wall thickness selection (typically 0.5–0.8 mm), minimizing thermal resistance while maintaining structural integrity.
- Temperature Range Suitability: Validated for continuous operation in the medium-temperature range of 30°C to 120°C (86°F to 248°F), covering applications such as district heating, process cooling, and industrial heat recovery.
5.2 Mechanical & Durability Performance
- Corrosion Resistance: SUS316L grade demonstrates excellent resistance to chloride-induced pitting corrosion, with a Critical Pitting Temperature (CPT) exceeding 45°C in 3.5% NaCl solution, making it suitable for coastal and humid environments.
- Thermal Fatigue Resistance (热疲劳抗性): The solution-annealed microstructure provides superior resistance to thermal cycling fatigue, validated through accelerated thermal cycling tests (≥ 5000 cycles at ΔT = 80°C without cracking).
- Creep Resistance (蠕变抗性): At medium temperatures (up to 120°C), the austenitic microstructure exhibits negligible creep deformation under sustained internal pressure loads up to 1.6 MPa.
5.3 Flow & Pressure Performance
- Pressure Drop (压降): The smooth inner surface finish (Ra ≤ 0.8 μm) minimizes frictional pressure drop, with Darcy friction factors (λ) of 0.018–0.025 at Reynolds numbers (Re) of 10,000–50,000, typical of medium-temperature coil tube flow regimes.
- Flow Uniformity: Continuous coil forming ensures consistent cross-sectional geometry, promoting uniform flow distribution across the coil tube array and preventing localized hot spots or flow maldistribution.
6. Applications
- HVAC Systems (暖通空调系统): Medium-temperature air-cooled coil tubes for commercial and industrial heating/cooling units, air handlers, and fan coil units (FCU).
- Heat Exchangers (换热器): Fin-and-tube heat exchangers for process cooling, condensation, and evaporation in chemical, pharmaceutical, and food processing industries.
- Refrigeration Systems (制冷系统):