Stainless Steel Coil Tube (盘管) — Technical Product Specification

1. Product Overview

The Stainless Steel Coil Tube (盘管 Coiltube), product reference No. 541, is a precision-engineered continuous tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Unlike conventional straight-length piping, coil tubes are formed into continuous helical or serpentine configurations during the manufacturing process, enabling compact heat-transfer surfaces, fluid distribution systems, and specialized mechanical assemblies within constrained spatial environments.

This product category encompasses a wide range of austenitic and duplex stainless steel grades, engineered to deliver superior corrosion resistance, high-temperature mechanical integrity, and long-term service reliability. The coil geometry—whether wound in a single helix, double helix, or serpentine layout—provides significant advantages in thermal efficiency, pressure drop optimization, and installation flexibility compared to equivalent straight-pipe systems.

Key Engineering Insight: Coil tubes are subject to unique failure modes distinct from straight piping, including fatigue cracking at the inner bend radius, differential thermal expansion stresses, and localized wall-thinning due to erosion-corrosion at flow transition points. Understanding these mechanisms is critical to proper specification and application.

2. Material & Properties

2.1 Common Stainless Steel Grades

2.2 Mechanical Properties (Typical — Annealed Condition)

Property ASTM / EN Standard Grade 304 Grade 316 Grade 2205
Yield Strength (0.2% Offset) ASTM A213 / EN 10216-5 ≥ 205 MPa ≥ 205 MPa ≥ 450 MPa
Tensile Strength (Rm) ASTM A213 / EN 10216-5 515 – 730 MPa 515 – 730 MPa 620 – 880 MPa
Elongation (A50mm) ASTM A213 ≥ 35 % ≥ 35 % ≥ 25 %
Hardness (HBW) ASTM A213 ≤ 200 ≤ 200 ≤ 310
Thermal Conductivity (20 °C) — 16.3 W/(m·K) 14.6 W/(m·K) 15.2 W/(m·K)
Linear Expansion Coefficient (20–100 °C) — 17.3 × 10⁻⁶ /K 16.6 × 10⁻⁶ /K 13.9 × 10⁻⁶ /K

2.3 Chemical Composition (Typical, wt.%)

Element 304 316 2205
C ≤ 0.08 ≤ 0.08 ≤ 0.03
Cr 18.0 – 20.0 16.0 – 18.0 22.0 – 23.0
Ni 8.0 – 10.5 10.0 – 14.0 4.5 – 6.5
Mo — 2.0 – 3.0 3.0 – 3.5
N — — 0.14 – 0.20
Si ≤ 0.75 ≤ 0.75 ≤ 1.00
Mn ≤ 2.00 ≤ 2.00 ≤ 1.50

3. Specifications

3.1 Geometric & Dimensional Specifications

Parameter Specification Range Standard Reference
Outer Diameter (OD) Φ3.0 mm – Φ159.0 mm (1/8" – 6") ASTM A213, EN 10216-5
Wall Thickness (WT) 0.3 mm – 8.0 mm ASTM A213, ASME SA-213
Coil Bend Diameter (CBD) 50 mm – 2,000 mm (adjustable per design) Project-specific
Coil Length (Total) 5 m – 500 m (continuous) Project-specific
Tolerance on OD ± 0.10 mm (OD ≤ 25 mm); ± 0.15 mm (OD > 25 mm) ASTM A213
Tolerance on Wall Thickness ± 10 % of nominal (minimum 0.05 mm) ASTM A213
Surface Finish Mill finish, Bright Annealed (BA), or Electropolished (Ra ≤ 0.5 μm) ASTM A269, EN 10217-7
End Condition Cut ends, Beveled ends, or Threaded ends Per customer drawing

3.2 Heat-Transfer Performance Parameters

Parameter Typical Value / Range Notes
Maximum Operating Temperature (Air) 870 °C (304/316); 1,093 °C (310S) Continuous service, oxidizing atmosphere
Maximum Operating Temperature (Vacuum) 1,150 °C (304/316); 1,200 °C (310S) Reduced to prevent grain growth
Minimum Operating Temperature −196 °C (LN₂ service) Austenitic grades maintain ductility
Design Pressure Up to 400 bar (project-specific) Per ASME BPVC Section VIII
Heat Transfer Coefficient (Inside) 1,000 – 15,000 W/(m²·K) Dependent on fluid velocity and properties
Pressure Drop (per meter of coil) 0.01 – 2.5 kPa/m Function of flow regime and geometry

3.3 Applicable Standards

4. Manufacturing Process

4.1 Process Flow Diagram

  1. Raw Material Selection & Verification: Ingot or hot-rolled coil sourced from certified mills. Incoming inspection includes Chemical Composition Analysis (spectrometry), Heat Number Traceability, and Mechanical Property Verification.
  2. Hot Rolling & Annealing: Billet is hot-rolled into seamless tube blanks. Full annealing at 1,050 – 1,150 °C followed by controlled cooling (air or furnace cool) to achieve uniform austenitic microstructure and relieve residual stresses.
  3. Cold Drawing / Cold Pilgering: Seamless tube is cold-worked to achieve final OD and wall thickness tolerances. This process enhances surface finish, dimensional accuracy, and mechanical properties (work hardening).
  4. Solution Annealing & Pickling: Tubes are reheated to 1,050 – 1,100 °C (austenitization), rapidly quenched (water or air), then acid-pickled (HNO₃/HF mixture) to remove oxide scale and restore passive chromium oxide film.
  5. Coil Forming (Rolling/Bending): The straight tube is fed into a programmable coil-forming machine. Key parameters include:
    • Bend Radius Control: Minimum bend radius typically 3–5× tube OD to prevent ovalization and cracking.
    • Forming Speed: Controlled to limit strain rate, preventing adiabatic heating and microstructural damage.
    • Support Mandrel: Internal mandrel or hydraulic support used for thin-wall tubes to prevent collapse.
    • Coil Pitch & Diameter: Precisely controlled via CNC servo systems to meet design specifications.
  6. Post-Forming Stress Relief: Optional stress-relief annealing at 850 – 900 °C to reduce residual bending stresses and improve fatigue life.
  7. End Finishing & Inspection: Cut ends are deburred, chamfered, or threaded. Full-length visual inspection, dimensional verification, and pressure testing are performed.

4.2 Critical Manufacturing Considerations

5. Applications

5.1 Primary Application Domains