Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuously coiled, cold-formed tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is produced using a Three-Roll Spiral Coil Tube Bending Machine (三辊螺旋盘管弯管机), which enables the precise formation of uniform spiral-coiled stainless steel tubing with consistent cross-sectional geometry, wall thickness, and dimensional accuracy. The coil tube is supplied in continuous lengths wound into a helical or spiral configuration, making it ideal for applications requiring extended, pre-shaped tubing without the need for field welding or additional forming operations.
Coil tubes are distinguished from straight pipe by their pre-formed helical geometry, which provides inherent advantages in heat exchange efficiency, space utilization, and structural compactness. Wenzhou Jixing Metal Materials Co., Ltd. specializes in the production of high-grade stainless steel coil tubes conforming to international standards, serving industries including HVAC, chemical processing, food and beverage, pharmaceutical, and oil and gas.
2. Material & Properties
2.1 Material Grades
- AISI 304 / EN 1.4301 — General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. The most widely specified grade for coil tube applications.
- AISI 316 / EN 1.4401 — Enhanced corrosion resistance due to molybdenum (Mo) addition (2.0–3.0%); suitable for aggressive chemical environments and marine applications.
- AISI 316L / EN 1.4404 — Low-carbon variant of 316 (C ≤ 0.03%) providing superior resistance to intergranular corrosion after welding.
- AISI 321 / EN 1.4541 — Stabilized austenitic grade with titanium (Ti) addition, suitable for elevated-temperature service up to 870°C.
- AISI 310S / EN 1.4845 — High-temperature austenitic grade with elevated chromium and nickel content, designed for sustained service at 1090°C.
2.2 Mechanical Properties (Annealed Condition)
| Property | 304 / 1.4301 | 316 / 1.4401 | 316L / 1.4404 | 321 / 1.4541 |
|---|---|---|---|---|
| Tensile Strength (Rm) | ≥ 515 MPa | ≥ 515 MPa | ≥ 485 MPa | ≥ 515 MPa |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 205 MPa | ≥ 170 MPa | ≥ 205 MPa |
| Elongation (A50mm) | ≥ 40% | ≥ 40% | ≥ 40% | ≥ 40% |
| Density (ρ) | 7.93 g/cm³ | 8.00 g/cm³ | 8.00 g/cm³ | 8.00 g/cm³ |
| Thermal Conductivity (λ, 100°C) | 16.3 W/(m·K) | 16.3 W/(m·K) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Maximum Service Temperature | 870°C | 870°C | 870°C | 1090°C |
2.3 Surface Finish Options
- 2B Finish — Cold-rolled and annealed in protective atmosphere; smooth, non-reflective surface suitable for general industrial use.
- No. 4 Brushed Finish — Uniformly textured surface with fine parallel grain lines; used in architectural and food-grade applications.
- Mirror / 8K Finish — Polished to a reflective, mirror-like appearance; used in decorative and high-purity applications.
- Pickle & Passivate (P&P) — Acid pickling followed by passivation to remove mill scale and form a protective chromium oxide layer.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) — Item No. 1619 |
| Outer Diameter (OD) | 6.0 mm – 108.0 mm |
| Wall Thickness (WT) | 0.30 mm – 6.00 mm |
| Coil Diameter | 300 mm – 1,200 mm (adjustable per order) |
| Coil Length (Continuous) | Up to 200 m per coil (standard); custom lengths available |
| Spiral Pitch | 15 mm – 50 mm (configurable) |
| OD Tolerance | ±0.10 mm (≤ 25 mm OD); ±0.15 mm (> 25 mm OD) |
| WT Tolerance | ±10% (per ASTM A213 / EN 10216-5) |
| Manufacturing Equipment | Three-Roll Spiral Coil Tube Bending Machine (三辊螺旋盘管弯管机) |
| Applicable Standards | ASTM A213, ASTM A312, EN 10216-5, EN 10217-7, GB/T 12771, JIS G3459 |
| Heat Treatment | Solution Annealing (1050°C – 1150°C) followed by rapid quenching |
| End Treatment | Plain ends, beveled ends, or threaded ends (per customer specification) |
| Packaging | Wooden crate with moisture-proof wrapping; custom packaging available |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
4. Manufacturing Process
4.1 Raw Material Selection & Incoming Inspection
High-purity stainless steel strip or round bar stock is sourced from certified mills with full material traceability. Incoming material undergoes strict inspection for chemical composition (via optical emission spectrometry, OES), mechanical properties, and surface quality to ensure compliance with the specified grade and standard.
4.2 Cold Forming & Sizing
The raw strip or tube blank is fed through a series of precision roll-forming stations that progressively shape the material into the target cross-sectional geometry (circular, oval, or rectangular). Dimensional accuracy is maintained through CNC-controlled roll adjustments and in-line laser diameter measurement.
4.3 Welding (for Welded Coil Tubes)
Where applicable, the formed strip is welded along the seam using High-Frequency Induction Welding (HF) or Tungsten Inert Gas Welding (TIG/GTAW). HF welding achieves weld speeds of 10–30 m/min with minimal heat-affected zone (HAZ), preserving the metallurgical integrity of the base metal. TIG welding is employed for higher-purity applications requiring superior weld quality.
4.4 Three-Roll Spiral Coiling
The formed and welded tube is then passed through the Three-Roll Spiral Coil Tube Bending Machine, which is the core technology distinguishing this product. The machine employs three independently driven forming rolls arranged in a triangular configuration:
- Drive Roll (Top Roll) — Provides the primary driving force and controls the axial feed rate of the tube.
- Forming Rolls (Left & Right) — Apply lateral bending forces to induce the helical curvature of the tube.
- Synchronization System — A closed-loop servo control system synchronizes the rotational speeds of all three rolls to maintain a constant spiral pitch and coil diameter throughout the forming process.
The three-roll configuration ensures uniform bending stress distribution along the tube cross-section, minimizing ovality distortion and residual stress. The resulting spiral coil tube exhibits consistent curvature radius, smooth transitions, and minimal geometric deviation.
4.5 Solution Annealing & Pickle Passivation
Following coiling, the stainless steel coil tube is subjected to solution annealing at 1050°C – 1150°C in a controlled atmosphere (hydrogen or vacuum) to relieve residual stresses from cold forming and restore full solution-solid solution microstructure. The annealed tube is then rapidly quenched to achieve the required mechanical properties and corrosion resistance.
A subsequent pickle and passivate treatment removes any surface oxide scale formed during annealing and establishes a thin, adherent chromium oxide passivation layer (Cr₂O₃) that provides immediate corrosion protection.
4.6 Quality Inspection & Testing
- Dimensional Inspection — OD, WT, coil diameter, and spiral pitch verified using laser scanners and calipers.
- Hydrostatic / Pneumatic Testing — Each coil tested at 1.5× working pressure to verify seam integrity and leak-tightness.
- Chemical Analysis — OES or wet chemistry verification of alloy composition against the specified grade.
- Corrosion Testing — Salt spray test (ASTM B117) and intergranular corrosion test (ASTM A262 Practice E) for applicable grades.
- Visual & Surface Inspection — Manual and automated surface inspection for defects, weld seams, and surface finish quality.
4.7 Packaging & Dispatch
Finished coil tubes are wound, secured with steel strapping bands, wrapped in moisture-proof polyethylene film, and packed in reinforced wooden crates or steel drums. Each package is labeled with the product designation, material grade, heat number, dimensions, and manufacturing date for full traceability.
5. Applications
5.1 Heat Exchangers & Boilers
Coil tubes are extensively used in shell-and-tube heat exchangers, fired boilers, and waste heat recovery systems. The spiral geometry maximizes heat transfer surface area within a compact volume, improving thermal efficiency while reducing the footprint of the equipment.
5.2 HVAC & Refrigeration
Stainless steel coil tubes serve as evaporator and condenser coils in heating, ventilation, air conditioning (HVAC), and refrigeration systems. The corrosion resistance of austenitic stainless steels ensures long service life in humid and chemically aggressive environments.
5.3 Food & Beverage Processing
Grades 304 and 316L coil tubes are widely employed in pasteurizers, sterilizers, brewing equipment, and dairy processing systems. The smooth surface finish and hygienic design prevent microbial contamination, meeting FDA and EU food-grade requirements.
5.4 Chemical & Pharmaceutical Processing
316L coil tubes are the material of choice for chemical reactors, distillation columns, and pharmaceutical equipment where resistance to aggressive acids, alkalis, and chlorides is required. The low-carbon composition of 316L eliminates the risk of intergranular corrosion during welding operations.
5.5 Oil, Gas & Petrochemical
In oil and gas processing, stainless steel coil tubes are used in separators, condensers, and heat recovery units. Grades such as 321 and 310S provide the necessary resistance to sulfidation and high-temperature oxidation in upstream and downstream processing facilities.
5.6 Marine & Offshore
The superior chloride pitting resistance of 316L coil tubes makes them suitable for marine heat exchangers, desalination systems, and offshore platform piping where exposure to saltwater and atmospheric marine environments is constant.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| ISO 14001:2015 | Environmental Management System certification demonstrating environmental responsibility. |
| ISO 45001:2018 | Occupational Health and Safety Management System certification. |
| CE Marking | Conformity to European health, safety, and environmental protection standards (EU Directive 2014/68/EU — Pressure Equipment Directive). |
| EN 10204 3.1 | Material test certificate issued by a qualified testing authority, providing full traceability of chemical and mechanical properties. |
| NACE MR0175 / ISO 15156 | Compliance for sour service applications (H₂S-containing environments), where applicable. |
| ASME BPVC Section IX |