Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coiled Tubing) is a continuous-length seamless or welded stainless steel tube supplied in a helical coil configuration. This format eliminates the need for butt-welding multiple straight pipe sections, thereby reducing joint-related failure points and improving system integrity. The coil tube is manufactured through a controlled multi-pass deformation and coiling process, ensuring uniform wall thickness, consistent dimensional accuracy, and excellent mechanical properties throughout the entire length.
Produced by Wenzhou Jixing Metal Materials Co., Ltd., this product leverages advanced coiling technology that progressively shapes and feeds the tube into a tight coil, achieving high productivity while maintaining low residual stress levels. The coil form factor is particularly advantageous for applications requiring long continuous runs without intermediate connections, such as heat exchangers, chemical processing lines, and food-grade piping systems.
2. Material & Properties
Stainless steel coil tubes are fabricated from austenitic, ferritic, or duplex stainless steel grades selected according to the service environment. The following table summarizes typical material grades and their key mechanical and chemical properties:
| Grade | UNS Designation | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | Corrosion Resistance | Typical Application |
|---|---|---|---|---|---|---|
| 304 | S30400 | ≥205 | ≥515 | ≥40 | Excellent general-purpose | Food & beverage, pharmaceutical |
| 316 | S31600 | ≥205 | ≥515 | ≥40 | Superior chloride resistance | Chemical processing, marine |
| 316L | S31603 | ≥170 | ≥485 | ≥45 | Low-carbon, weld-resistant | Welded assemblies, nuclear |
| 321 | S32100 | ≥205 | ≥515 | ≥40 | Heat-stable, intergranular resistant | High-temperature exhaust systems |
| 904L | S90411 | ≥220 | ≥550 | ≥35 | Extreme acid resistance | Harsh chemical environments |
| 2205 Duplex | S31803 | ≥450 | ≥550 | ≥25 | High strength + corrosion | Offshore, desalination |
Key metallurgical characteristics of the coil tube include:
- Crystal Structure: Austenitic grades (304, 316, 316L, 321) possess an FCC (Face-Centered Cubic) structure providing excellent ductility and formability.
- Non-Magnetic (Annealed): Austenitic coil tubes are essentially non-magnetic in the annealed condition; however, cold working during coiling may induce partial martensitic transformation, resulting in slight magnetic susceptibility.
- Cryogenic Performance: Retains full mechanical properties down to liquid nitrogen temperatures (−196 °C) without embrittlement.
- Maximum Service Temperature: Typically 870 °C (1600 °F) for 304/316 grades in oxidizing atmospheres; duplex grades limited to ~300 °C to prevent 475 °C embrittlement.
3. Specifications
The following table presents the standard dimensional and tolerance specifications for the stainless steel coil tube product:
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 114.3 mm (¼" – 4½") | ASTM A269 / A270 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm | ASTM A269 / A270 |
| OD Tolerance | ±0.05 mm (OD ≤ 25 mm); ±0.5% (OD > 25 mm) | ASTM A269 |
| Wall Thickness Tolerance | ±10% (WT ≥ 0.8 mm); ±0.13 mm (WT < 0.8 mm) | ASTM A269 |
| Coil Inner Diameter | 500 mm – 1500 mm (configurable) | Manufacturer specification |
| Coil Length per Reel | 50 m – 300 m (typical) | — |
| Surface Finish | No. 1 (mill), 2B (bright annealed), BA (bright annealed), EP (electropolished), HL (hairline), Mirror (#8) | ASTM A480 / A481 |
| End Treatment | Beveled, flat-cut, or threaded per customer requirement | — |
| Heat Treatment | Solution annealing at 1010–1150 °C followed by air/water quench | ASTM A269 |
| Packaging | Wooden pallet with moisture-proof wrapping; coil secured with steel straps | ISO 4126 |
4. Manufacturing Process
The production of stainless steel coil tubes involves a sophisticated sequence of forming, deformation, and coiling operations. The following stages outline the complete manufacturing workflow:
- Raw Material Preparation: Hot-rolled stainless steel coils (slit coils) are received and inspected for surface quality, chemical composition (via OES — Optical Emission Spectrometry), and mechanical properties. Material certifications per ASTM/EN standards are verified.
- Slitting & Leveling: The master coil is slit to the required blank width and passed through a roller leveling unit to remove coil set and ensure flatness prior to forming.
- Forming & Welding (for welded tube): The flat strip is progressively shaped through a series of roll stands into a tubular configuration. A TIG (Tungsten Inert Gas) or laser welding process fuses the longitudinal seam under inert gas (argon) shielding, ensuring a clean, oxide-free weld root.
- Heat Treatment (Solution Annealing): The formed tube is annealed in a continuous furnace at 1010–1150 °C in a controlled atmosphere (endothermic gas or vacuum) to dissolve precipitated carbides, restore full solution-hardened properties, and achieve a uniform recrystallized microstructure.
- Pickle & Passivate: Post-annealing, the tube is acid pickled (HNO₃/HF blend) to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide film on the surface.
- Multi-Pass Deformation & Sizing: The tube passes through multiple calibrating rolls to achieve precise OD and wall thickness within tolerance. This progressive deformation stage is critical for dimensional accuracy.
- Coiling Operation: The finished tube is fed through a precision coiling head that applies controlled bending moments to form a uniform helical coil. The coiling machine ("盘管器") is the key equipment that transforms straight tube into coil form with minimal residual stress. Advanced servo-controlled coilers adjust bending radius and tension in real-time to prevent ovality, wrinkles, or plastic deformation beyond yield.
- Final Inspection & Testing: Each coil undergoes hydrostatic testing (per ASTM A269), eddy current testing (ECT) for seam integrity, dimensional measurement (laser gauge), and visual surface inspection. Chemical analysis certificates and mechanical test reports are compiled.
- Packaging & Dispatch: Coils are wrapped in moisture-barrier film, strapped with high-tensile steel bands, and loaded onto wooden pallets or coil cradles for export-ready shipping.
Process Innovation Note: The progressive deformation and coiling technology employed by Wenzhou Jixing Metal Materials Co., Ltd. has been refined through iterative optimization. The coiling machine undergoes repeated adjustment cycles ("一次次变形" — successive deformation passes) to achieve optimal coil geometry with minimal energy input, reducing labor intensity while improving coil uniformity and product yield.
5. Applications
The stainless steel coil tube finds extensive application across multiple high-performance industries:
- Food & Beverage Industry: Hygienic piping for dairy processing, brewing, and beverage transfer lines (304/316L with sanitary surface finish).
- Pharmaceutical & Biotechnology: CIP/SIP (Clean-in-Place / Sterilize-in-Place) compatible tubing for drug manufacturing, fermentation, and cleanroom utilities.
- Heat Exchangers & Boilers: Coil tubes for shell-and-tube heat exchangers, air-cooled condensers, and fire-tube boilers where long continuous lengths reduce header connections.
- Chemical Processing: Reactor internals, distillation column supports, and acid/alkali transfer lines (316, 904L, Hastelloy grades).
- Automotive & Exhaust Systems: Catalytic converter inlet/outlet tubes and turbocharger piping (321, 310S grades for high-temperature service).
- Oil & Gas / Offshore: Subsea umbilical components, wellhead instrumentation tubing (duplex 2205/2507 grades).
- Medical Devices: Endoscope sheaths, surgical instrument tubing, and implant-grade components (316L with electropolished finish).
- Solar & Energy Systems: Heat pipe manufacturing, solar thermal collector tubes, and geothermal well casings.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and product certifications to ensure compliance with international standards:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO/TS 22163 | Automotive Quality Management (IATF-aligned) |
| ASTM A269 | Welded Austenitic Stainless Steel Tubes for Chemical and Similar Severe Service |
| ASTM A270 | Welded Austenitic Chromium and Chromium-Nickel Stainless Steel Tubes for Chemical and Similar Severe Service |
| EN 10216-5 | Seamless and Welded Stainless Steel Tubes — Technical Delivery Conditions |
| GB/T 12771 | Chinese National Standard for Welded Stainless Steel Tubes for General Purposes |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (food-grade applications) |
| 3-A Sanitary Standards | International Dairy & Food Grade Hygienic Design |
| PED 2014/68/EU | Pressure Equipment Directive (CE marking for pressure applications) |
Each shipment is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 Type 3.1, including:
- Chemical composition analysis (per heat number)
- Mechanical test results (tensile, yield, elongation, hardness)
- Hydrostatic test pressure and duration
- Dimensional inspection records
- Heat treatment log (furnace curve, cooling rate)
- Traceability documentation linking coil ID to mill heat number
7. Unique Selling Points
- Seamless-Length Advantage: Eliminates longitudinal butt-welds, reducing leak points and maintenance requirements by up to 90% compared to straight pipe assemblies.
- Precision Coiling Technology: Advanced servo-controlled coilers ensure consistent coil diameter, minimal tube ovality (< 2%), and low residual stress, preserving material toughness.
- Multi-Grade Flexibility: Full range from standard austenitic (304, 316) to super-austenitic (904L) and duplex (2205, 2507) grades, supporting the most demanding corrosion environments.
- Custom Surface Finishes: Available from industrial No. 1 through mirror #8 finish, with electropolishing (EP) for biocompatible, low-bacterial-surface applications.
- Full Traceability: Heat-number-linked documentation from raw material through final coil, ensuring complete supply chain accountability.
- Cost & Installation Efficiency: Coil supply reduces field fabrication labor, welding consumables, and installation time by 30–50% versus straight pipe.
8. Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers full engineering support for coil tube selection, including:
- Corrosion resistance assessment for specific process media (via potentiodynamic polarization testing)
- Thermal expansion and stress analysis for coil layout design
- Custom OD × WT configurations outside standard ranges
- Special end treatments (threaded, flanged, sanitary tri-clamp, sanitary socket weld)
- On-site installation guidance and coil spool design consultation