Stainless Steel Coil Tube (Coiltube) — Model JX-CT Series
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered continuous tubular product designed for high-performance thermal management and fluid conveyance applications. The coil tube is formed through a cold-drawing and coiling process, producing a seamless, continuous tube wound into a compact helical or spiral configuration. This geometry provides a significantly greater surface-area-to-volume ratio compared to straight tubing, making it exceptionally effective for heat exchange, refrigeration, and thermal regulation systems.
This product line is specifically validated through rigorous academic research, including the study "Heat Transfer Calculation and Experimental Research on the Finite Closed Cavity Space with Built-in Hot Coil Tube", which confirms the superior thermal performance characteristics of the coil tube within enclosed cavity configurations. The research demonstrates that the built-in hot coil tube achieves efficient convective and conductive heat transfer within finite closed interlayer spaces, providing quantifiable thermal performance data that underpins the product's engineering specifications.
2. Material & Properties
2.1 Base Materials
The coil tube is fabricated from high-grade austenitic stainless steel alloys, selected for their outstanding combination of corrosion resistance, mechanical integrity, and thermal conductivity. The primary material grades include:
- SAE 304 (ASTM A269 TP304) — The most widely specified austenitic stainless steel, offering excellent general corrosion resistance, good weldability, and adequate high-temperature strength.
- SAE 316 (ASTM A269 TP316) — Enhanced corrosion resistance due to molybdenum (Mo) addition, particularly suited for chlorinated environments, chemical processing, and marine applications.
- SAE 316L (ASTM A269 TP316L) — Low-carbon variant of 316, providing superior resistance to intergranular corrosion and enhanced weldability for critical fabrication scenarios.
- SAE 321 (ASTM A269 TP321) — Titanium-stabilized austenitic grade for applications requiring resistance to sensitization at elevated temperatures.
2.2 Mechanical Properties
| Property | SAE 304 | SAE 316 | SAE 316L |
|---|---|---|---|
| Tensile Strength (Ultimate) | ≥ 515 MPa (74,700 psi) | ≥ 515 MPa (74,700 psi) | ≥ 485 MPa (70,300 psi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (29,700 psi) | ≥ 205 MPa (29,700 psi) | ≥ 170 MPa (24,700 psi) |
| Elongation (at Break) | ≥ 40% | ≥ 40% | ≥ 40% |
| Density | 8.0 g/cm³ | 8.0 g/cm³ | 8.0 g/cm³ |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | 14.6 W/(m·K) |
| Maximum Service Temperature | 870°C (1,598°F) | 870°C (1,598°F) | 870°C (1,598°F) |
| Minimum Service Temperature | −196°C (−321°F) | −196°C (−321°F) | −196°C (−321°F) |
2.3 Chemical Composition
| Element | SAE 304 | SAE 316 |
|---|---|---|
| Carbon (C) | ≤ 0.08% | ≤ 0.08% |
| Chromium (Cr) | 18.0 – 20.0% | 16.0 – 18.0% |
| Nickel (Ni) | 8.0 – 10.5% | 10.0 – 14.0% |
| Molybdenum (Mo) | — | 2.0 – 3.0% |
| Iron (Fe) | Balance | Balance |
3. Specifications
3.1 Dimensional Specifications
| Parameter | Range / Value | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 108.0 mm (1/8" – 4") | ± 0.05 mm (± 0.002") |
| Wall Thickness | 0.25 mm – 3.00 mm (0.010" – 0.118") | ± 10% of nominal |
| Coil Length | 10 m – 500 m (33 – 1,640 ft) | ± 5% |
| Coil Diameter (bundle) | 300 mm – 1,200 mm (12" – 48") | ± 2% |
| Coiling Pitch | 5.0 mm – 50.0 mm (adjustable) | ± 0.5 mm |
| End Condition | Cut square, beveled, or threaded | Per customer specification |
| Surface Finish | Bright annealed, pickled, passivated, or electropolished | Ra ≤ 0.4 μm (electropolished) |
| Standard Lengths Available | 15 m, 30 m, 50 m, 100 m, custom | — |
3.2 Performance Specifications (Validated by Research)
| Performance Parameter | Typical Value | Test Condition |
|---|---|---|
| Heat Transfer Coefficient (Convective) | 1,500 – 6,500 W/(m²·K) | Fluid velocity 1 – 5 m/s, closed cavity |
| Pressure Drop (per meter) | 50 – 500 Pa/m | Dependent on fluid, velocity, and geometry |
| Thermal Efficiency (in closed interlayer space) | ≥ 85% | Based on experimental validation |
| Maximum Operating Pressure | Up to 10.0 MPa (1,450 psi) | Hydrostatic test at 1.5× working pressure |
| Cycle Fatigue Life | ≥ 10,000 thermal cycles | ΔT = 50°C, 304/316 grade |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection & Certification — Incoming stainless steel strip or bar stock is verified against mill test certificates (MTC), with spectroscopic analysis confirming chemical composition compliance.
- Piercing & Forming — Billet stock is pierced at elevated temperatures to form seamless tube blanks, eliminating weld seams and potential leak paths.
- Hot Rolling — The pierced tube is hot-rolled to approximate final dimensions, establishing initial geometry and relieving internal stresses.
- Cold Drawing — The tube is cold-drawn through precision tungsten carbide or ceramic dies to achieve exact dimensional tolerances, improved surface finish, and enhanced mechanical properties through work hardening.
- Intermediate Annealing — Periodic solution annealing at 1,050°C – 1,150°C (1,922°F – 2,094°F) followed by rapid quenching restores ductility and prevents cracking during multi-stage drawing.
- Final Cold Drawing & Sizing — Final pass through calibrated dies ensures conformance to specified OD, wall thickness, and roundness tolerances.
- Coiling — The finished tube is wound into a compact coil using precision coiling equipment that maintains consistent pitch and avoids plastic deformation or kinking. The coiling process is carefully controlled to prevent work-hardening damage.
- Heat Treatment (Final Annealing) — Solution annealing and water quenching or controlled-air cooling to achieve the desired microstructure (fully austenitic, grain size per ASTM E112 standard).
- Pickling & Passivation — Chemical treatment removes mill scale and surface contaminants, followed by passivation to restore and enhance the passive chromium oxide film for optimal corrosion resistance.
- Quality Inspection & Testing — Comprehensive dimensional, mechanical, and non-destructive testing (see Section 6).
- Packaging & Dispatch — Coils are wrapped in protective material, secured on wooden or steel reels, and shipped with complete documentation.
4.2 Key Process Controls
- Dimensional Control: In-process optical and laser measurement systems monitor OD and wall thickness continuously during cold drawing.
- Surface Integrity: Automated surface inspection systems detect and reject tubes with scratches, dents, or surface defects exceeding Ra 0.8 μm (unless electropolished specification is ordered).
- Coil Geometry Control: Coiling tension and speed are regulated to maintain uniform pitch, prevent inter-coil contact damage, and ensure the coil unwinds smoothly during downstream processing.
5. Applications
5.1 Heat Exchange Systems
Based on validated research into heat transfer within finite closed interlayer spaces, the coil tube is optimally suited for:
- Shell-and-Tube Heat Exchangers: The coil tube serves as the tube bundle element, providing maximum heat transfer surface area within a compact envelope.
- Air Conditioners & Refrigeration Units: Evaporator and condenser coils for HVAC (Heating, Ventilation, and Air Conditioning) systems, leveraging the high surface-area-to-volume ratio for efficient phase-change heat transfer.
- Process Cooling & Heating: Industrial process equipment requiring precise temperature control in chemical, pharmaceutical, and food processing industries.
5.2 Fluid Conveyance
- Chemical Processing: Conveyance of aggressive chemical fluids, acids, and solvents where corrosion resistance is critical.
- Food & Beverage Industry: Hygienic-grade tubing for dairy, brewing, and pharmaceutical processing (compliant with FDA and 3-A Sanitary Standards).
- Pharmaceutical Manufacturing: CIP (Clean-in-Place) and SIP (Sterilization-in-Place) compatible tubing for GMP (Good Manufacturing Practice) environments.
- Water Treatment & Desalination: Brackish and seawater applications leveraging 316/316L corrosion resistance.
5.3 Specialized Applications
- Heat Storage & Recovery Systems: Thermal energy storage units where the coil tube geometry maximizes heat absorption and release efficiency within confined spaces.
- Instrumentation & Piping: Precision instrumentation tubing for pressure sensing, flow measurement, and analytical laboratory applications.
- Automotive & Aerospace: Fuel lines, exhaust components, and hydraulic systems requiring lightweight, corrosion-resistant tubing.
- Marine & Offshore: Seawater cooling systems and underwater fluid conveyance.
6. Quality Certifications & Testing
6.1 Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| ISO 14001:2015 |