Stainless Steel Coil Tube (Coil Tube) — Product Technical Specification

1. Product Overview

The Stainless Steel Coil Tube (Coil Tube) is a continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., wound into a helical coil configuration for efficient storage, transportation, and direct processing. This product represents a specialized form of seamless or welded stainless steel tubing, engineered to deliver superior thermal performance, corrosion resistance, and mechanical integrity across a broad spectrum of industrial applications.

Unlike straight-length tubes, coil tubes are delivered in continuous helical form, eliminating the need for butt-welding multiple sections during installation. This configuration is particularly advantageous in applications such as coil-type ice storage systems (Coil-type Thermal Energy Storage Devices), heat exchangers, refrigeration circuits, and process piping where long, uninterrupted tube runs are required.

The theoretical design of coil-type systems — as analyzed in academic literature on thermal energy storage — demonstrates that coil geometry provides significantly higher surface-area-to-volume ratios compared to straight tube arrangements. This geometric advantage translates directly into enhanced heat transfer efficiency, making stainless steel coil tubes indispensable in thermal management applications.

2. Material Composition & Properties

2.1 Available Grades

Stainless steel coil tubes are manufactured from multiple austenitic, ferritic, and duplex stainless steel grades, each selected based on the operational environment and performance requirements:

2.2 Key Mechanical Properties

2.3 Corrosion Resistance Characteristics

The passive chromium oxide film (Cr₂O₃) on the surface provides exceptional resistance to atmospheric corrosion, aqueous environments, and chemical media. Grades containing molybdenum (Mo), such as 316L and 2205, exhibit superior resistance to pitting corrosion and crevice corrosion in chloride-rich environments. The Pitting Resistance Equivalent Number (PREN) ranges from 19 (304L) to 40+ (2507), quantifying the alloy's resistance to localized attack.

2.4 Physical Properties
  • Density: 7.90–8.00 g/cm³
  • Melting Range: 1400–1450°C (austenitic grades)
  • Electrical Resistivity: 0.40–0.80 × 10⁻⁶ Ω·m at 20°C
  • Maximum Service Temperature: 870°C (304/316), 350°C (316L in corrosive environments)

3. Technical Specifications

Parameter Specification / Range Standard Reference
Outer Diameter (OD) Φ6.0 mm – Φ159 mm ASTM A269 / EN 10217
Wall Thickness 0.5 mm – 8.0 mm ASTM A269 / EN 10217
Coil Diameter Φ1,000 mm – Φ3,000 mm (standard); customizable up to Φ5,000 mm Manufacturer specification
Tightness (Coil Winding) Layer-to-layer gap ≤ 2 mm; uniform winding ISO 8499
Surface Finish 2B, No.4 Brushed, BA (Bright Annealed), Pickled & Passivated, Mirror (6K/8K) ASTM A480 / EN 10088
Temperature Range −196°C (LN₂) to +870°C (oxidizing atmosphere) Grade-dependent
Pressure Rating Up to 40 MPa (PN40), depending on OD, wall thickness, and grade ASME B31.3 / EN 13480
Tolerance on OD ±0.1 mm (precision) / ±0.5% (standard) ASTM A269
Tolerance on Wall Thickness ±10% (standard) / ±5% (precision) ASTM A269
Coil Length (per coil) 100 m – 500 m (typical); up to 1,000 m on request Manufacturer specification
End Condition Plain ends, beveled ends, or threaded ends (upon request) ASME B1.20.1
Heat Treatment Annealed (Solution Annealed), Stress-Relieved, Cold Worked (1/4 Hard, 1/2 Hard, Full Hard) ASTM A269

4. Manufacturing Process

4.1 Process Flow Overview

  1. Raw Material Selection: High-purity stainless steel billets or slabs are procured from certified mills, with chemical composition verified via Spectroscopic Analysis (OES/AES) to ensure compliance with ASTM, EN, or JIS standards.
  2. Hot Rolling / Hot Extrusion: The billet is heated to 1150–1250°C and formed into a seamless tube via hot extrusion or hot rolling through a mandrel, establishing the initial OD and wall thickness.
  3. Solution Annealing: Tubes are heated to 1050–1150°C (austenitic grades) and rapidly quenched in air or water to dissolve carbides and restore full austenitic structure, ensuring maximum corrosion resistance and ductility.
  4. Cold Drawing / Cold Rolling: The tube is drawn through precision dies to achieve final OD, wall thickness, and dimensional tolerances. This process introduces controlled cold work, enhancing mechanical strength while maintaining formability.
  5. Pickling & Passivation: The tube surface is treated with a mixed acid solution (HNO₃ + HF) to remove scale, decarburized layers, and contaminants, followed by passivation to restore the protective chromium oxide film.
  6. Coil Winding: The straight tube is wound onto a precision winding mandrel using automated coil winding equipment. Tension is carefully controlled to ensure uniform layer-to-layer contact without introducing residual stresses or deformation. The winding direction and pitch are optimized for handling stability.
  7. Quality Inspection: Each coil undergoes comprehensive inspection including dimensional verification, surface examination, and non-destructive testing (NDT).
  8. Packaging: Coils are wrapped with protective film, secured with steel strapping, and palletized for shipment.

4.2 Critical Process Parameters

5. Applications

5.1 Coil-Type Thermal Energy Storage (Ice Storage Systems)

One of the most technically demanding applications for stainless steel coil tubes is in coil-type ice storage devices (Coil-type Thermal Energy Storage Systems). In these systems, refrigerant coils are immersed in a water tank, where ice is formed on the outer surface of the tube during off-peak hours and melted during peak demand. The theoretical analysis of such systems demonstrates that:

5.2 Other Key Application Domains

6. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality assurance programs ensuring full traceability and compliance with international standards:

6.1 Factory Certifications

6.2 Product Standards

6.3 Inspection & Testing Protocols

6.4 Documentation & Traceability

Each coil is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204