Stainless Steel Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (Product No. 1587) is a precision-engineered continuous bent tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Specifically designed for coil tube heat exchanger applications, this product represents the culmination of advanced metallurgical processing and bending technology. The coil tube is produced through a continuous bending process on specialized coil tube bending machines, yielding a uniform helical geometry with consistent wall thickness and dimensional accuracy throughout the entire length. This product category falls under the technical literature and engineering application domain, serving as a critical component in thermal management systems across multiple industrial sectors.
The coil tube is distinguished from standard straight tubing by its continuous helical form, which provides significantly enhanced heat transfer surface area per unit volume, reduced fluid maldistribution, and improved convective coefficients due to secondary flow (Dean vortices) generated within the curved channel geometry.
Material & Properties
Material Grades
- Austenitic Stainless Steels: SUS304 (ASTM A213 TP304), SUS316 (ASTM A213 TP316), SUS316L (ASTM A213 TP316L), SUS321 (ASTM A213 TP321)
- Duplex Stainless Steels: SUS31803 (ASTM A790 S31803), SUS32205 (ASTM A790 S32205)
- Super Austenitic Steels: SUS904L (ASTM A213 TP904L)
Mechanical Properties (Typical — Annealed Condition)
| Property | SUS304 / 304L | SUS316 / 316L | SUS321 | SUS31803 (Duplex) |
|---|---|---|---|---|
| Tensile Strength (MPa, minimum) | 515 | 485 | 550 | 620 |
| Yield Strength (MPa, 0.2% offset) | 205 | 170 | 240 | 450 |
| Elongation (% at break, minimum) | 40 | 40 | 35 | 25 |
| Hardness (HB, maximum) | 217 | 217 | 217 | 278 |
| Density (g/cm³) | 7.93 | 8.00 | 7.95 | 7.80 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 | 15.5 | 11.4 |
| Thermal Expansion Coefficient (10⁻⁶/K, 20–100°C) | 17.3 | 16.0 | 17.0 | 13.7 |
Chemical Composition (wt%, Maximum unless noted)
| Grade | C | Si | Mn | P | S | Cr | Ni | Mo | N (min) |
|---|---|---|---|---|---|---|---|---|---|
| SUS304 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 18.0–20.0 | 8.0–10.5 | — | — |
| SUS316 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| SUS321 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 17.0–19.0 | 9.0–13.0 | — | — |
| SUS31803 | 0.030 | 1.00 | 2.00 | 0.030 | 0.020 | 22.0–23.0 | 6.0–8.0 | 2.5–3.5 | 0.10 |
Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A213 / ASME B36.19M |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm | ASTM A269 / EN 10216-5 |
| Coil Pitch (Helical Pitch) | 5.0 mm – 50.0 mm | Custom / ASME TEMA |
| Coil Bend Radius | 25 mm – 150 mm (centerline radius) | ASME B31.3 / EN 10217-7 |
| Coil Length (Total Uncoiled) | 5 m – 200 m (continuous) | Manufacturer Specification |
| Number of Turns | 5 – 500 turns | Custom |
| Surface Finish | 2B, BA (Bright Annealed), No. 4, Mirror (Ra ≤ 0.4 μm) | ASTM A480 / ASTM A666 |
| End Condition | Plain, Beveled, Threaded, or Flanged | ASME B16.11 / ASME B18.1 |
| Heat Treatment | Solution Annealed (1040–1120°C) + Water Quench | ASTM A213 |
| Maximum Operating Temperature | 870°C (304/321), 815°C (316), 300°C (31803) | ASME BPVC Section VIII |
| Pressure Rating (Design) | Up to 10.0 MPa (dependent on OD/WT combination) | ASME B31.3 / PED 2014/68/EU |
| Dimensional Tolerance | OD: ±0.1 mm; WT: ±0.05 mm; Pitch: ±0.5 mm | ISO 4287 / EN 10216-5 |
Manufacturing Process
Process Flow
- Raw Material Procurement: Hot-rolled stainless steel strip or seamless tubing sourced from certified mills, conforming to ASTM A213 / EN 10216-5 specifications. Incoming material undergoes spectroscopic analysis (OES) and mechanical property verification.
- Surface Preparation: Pickling and passivation treatment using mixed acid (HNO₃ + HF) solutions to remove scale and contaminants. Surface is then passivated with dilute nitric acid (20–30% HNO₃) to establish a stable chromium oxide film.
- Coil Tube Bending (Helical Forming): The core manufacturing step is performed on a specialized coil tube bending machine (盘管弯管机). The bending process utilizes a combination of:
- Three-roll forming for continuous helical geometry
- Die-assisted bending with mandrel support to prevent ovalization
- Controlled feed rate and hydraulic pressure to maintain dimensional consistency
- Heat Treatment (Post-Forming): Solution annealing at 1040–1120°C followed by rapid water quenching to relieve residual stresses introduced during cold bending. This ensures uniform microstructure (austenitic or duplex) and restores ductility.
- Precision Dimensional Verification: Laser-based coordinate measurement of coil pitch, bend radius, and ovality. Inline inspection ensures compliance with tolerance specifications at every stage.
- Surface Finishing: Electropolishing or mechanical polishing to achieve specified surface roughness (Ra values). Final passivation treatment for maximum corrosion resistance.
- Non-Destructive Testing (NDT):
- 100% Eddy current testing (ECT) for wall thickness verification and surface defect detection
- Helium or pneumatic pressure testing (1.5× design pressure) for leak integrity
- Visual inspection (VT) per ASTM E165
- Packaging and Traceability: Each coil tube is individually identified with heat number, specification, and batch traceability documentation. Protected packaging prevents mechanical damage and contamination during transit.
Key Technical Considerations in Coil Tube Bending
During the helical forming process on the coil tube bending machine, the following metallurgical and mechanical phenomena must be carefully controlled:
- Ovalization Control: The bending radius must be maintained at a minimum of 3× the tube OD to limit cross-sectional ovalization to below 5%, as specified by ASME B31.3. Internal mandrel support is employed for small-bore tubes.
- Work Hardening: Cold forming introduces strain hardening in the austenitic matrix. Post-forming annealing eliminates this effect and ensures the material retains full ductility for subsequent welding or installation.
- Residual Stress Management: Residual stresses from forming can accelerate stress corrosion cracking (SCC) in chloride environments. Complete solution annealing mitigates this risk.
- Pitch Uniformity: Consistent helical pitch is critical for heat exchanger performance. The bending machine is equipped with servo-controlled feed systems to achieve pitch tolerances of ±0.5 mm.
Applications
Primary Application Domains
- Coil Tube Heat Exchangers (CTHE): The principal application — high-efficiency heat exchangers utilizing helically wound stainless steel tubes for liquid-liquid and gas-liquid heat exchange. The helical geometry enhances turbulent flow and increases the heat transfer coefficient by 30–60% compared to straight tubes.
- Chemical Processing: Reactor internals, heat recovery systems, and distillation column cooling coils in acid, alkali, and halogenated solvent environments.
- Pharmaceutical & Biotechnology: GMP-compliant heat exchangers for sterilization (SIP/CIP), reactor temperature control, and clean fluid transfer. SUS316L grade is preferred for biocompatibility.
- Food & Beverage Industry: Pasteurization systems, CIP loops, and thermal processing equipment requiring high corrosion resistance and hygienic surface finishes.
- Petrochemical & Oil/Gas: Heat recovery steam generators (HRSG), condenser coils, and process cooling in offshore platforms and refineries. Duplex grades (SUS31803) are specified for chloride-containing environments.
- Nuclear & Power Generation: Auxiliary heat exchangers, feedwater heaters, and secondary cooling loops requiring proven long-term reliability.
- Marine & Offshore: Seawater coolers, ballast water heat exchangers, and shipboard thermal management systems.
- Automotive Thermal Management: EV battery cooling plates and heat rejection systems utilizing compact coil tube geometries.
Quality Certifications & Compliance
Manufacturing Certifications
- ISO 9001:2015 — Quality Management System