Stainless Steel Coil Tube (Coiltube) — Performance-Optimized Product Specification

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

Product Category: Stainless Steel Coil Tubing / Coiled Tube

Reference Document: Performance Analysis of Coiled Tube Water Quench Heat Exchanger (盘管式水凝固热换热器性能分析)

1. Product Overview

The Stainless Steel Coil Tube (Coiltube) is a precision-engineered, continuously wound tubular product manufactured from austenitic and duplex stainless steel grades. Unlike straight-cut seamless or welded tubes, coil tubes are produced in a continuous spiral or helical configuration, offering superior flexibility, enhanced heat transfer characteristics, and compact spatial packaging. This product line is specifically designed for applications demanding high thermal efficiency, corrosion resistance, and mechanical durability under continuous cyclic loading.

The coil tube configuration provides an inherently higher surface-area-to-volume ratio compared to straight pipe of equivalent mass, making it particularly advantageous for heat exchange applications such as water quench systems, condensers, evaporators, and regenerative thermal exchangers. Wenzhou Jixing Metal Materials Co., Ltd. leverages advanced cold-forming and hot-rolling technologies to deliver coil tubes with consistent wall thickness, uniform geometry, and reliable metallurgical integrity across the entire coil length.

Core Value Proposition: The coiled geometry eliminates the need for field bending, reducing installation labor, minimizing stress concentration points at elbows, and ensuring a monolithic tube integrity from end to end — critical for long-term reliability in high-temperature and high-pressure service.

2. Material & Properties

2.1 Available Material Grades

Coil tubes are manufactured from a range of stainless steel grades selected based on the target application environment:

2.2 Key Mechanical Properties (Typical — SUS304L / SUS316L)

Property Unit SUS304L (UNS S30403) SUS316L (UNS S31603)
Tensile Strength (Minimum) MPa ≥ 515 ≥ 515
Yield Strength (0.2% Offset, Minimum) MPa ≥ 205 ≥ 205
Elongation (in 50 mm, Minimum) % ≥ 40 ≥ 40
Density g/cm³ 7.93 8.00
Thermal Conductivity (at 20°C) W/(m·K) 16.3 16.3
Thermal Expansion Coefficient (20–100°C) ×10⁻⁶/K 17.0 17.3
Specific Heat (at 20°C) J/(kg·K) 500 500
Maximum Service Temperature °C 870 870
Pitting Resistance (PREN, Approximate) — 18–20 24–26

2.3 Chemical Composition (Typical, wt%)

Element SUS304L SUS316L SUS321 SUS31803 (Duplex)
C (Carbon) ≤ 0.030 ≤ 0.030 ≤ 0.08 ≤ 0.030
Cr (Chromium) 18.0–20.0 18.0–20.0 17.0–19.0 22.0–23.0
Ni (Nickel) 8.0–11.0 10.0–14.0 9.0–12.0 4.0–7.0
Mn (Manganese) ≤ 2.0 ≤ 2.0 ≤ 2.0 ≤ 3.0
Si (Silicon) ≤ 1.0 ≤ 1.0 ≤ 1.0 ≤ 1.0
P (Phosphorus) ≤ 0.045 ≤ 0.045 ≤ 0.045 ≤ 0.030
S (Sulfur) ≤ 0.030 ≤ 0.030 ≤ 0.030 ≤ 0.020
Mo (Molybdenum) — 2.0–3.0 — —
Ti (Titanium) — — 5×C to 0.70 —
N (Nitrogen) — — — 0.14–0.20

3. Specifications

3.1 Geometric Dimensions

Parameter Range / Value Notes
Outer Diameter (OD) Φ6 mm – Φ108 mm Custom diameters available upon request
Wall Thickness (WT) 0.5 mm – 6.0 mm Tolerance: ±10% of nominal
Coil Length Up to 5,000 m (continuous) Spooled or bulk packaging
Coil Inner Diameter (CID) Φ200 mm – Φ2,000 mm Dependent on OD and spring-back control
Coil Outer Diameter (COD) Φ400 mm – Φ2,500 mm For transport and handling
End Condition Plain, Beveled, or Threaded Custom end prep available
Straight Length (if pre-straightened) Up to 12,000 mm Available for coil-and-tube applications

3.2 Surface Finish Options

Finish Type Surface Roughness (Ra) Application
2B (Cold Rolled, Annealed & Bright) 0.4 – 0.8 μm General industrial use
No. 4 (Brushed) 0.8 – 1.6 μm Aesthetic and light corrosion environments
Electropolished 0.05 – 0.25 μm Pharmaceutical, food & beverage
Passivated (Acid Pickle) — Enhanced corrosion resistance
Mirror Polish (8K) ≤ 0.10 μm Decorative and high-purity applications

3.3 Applicable Standards

4. Manufacturing Process

The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical soundness, and consistent mechanical properties throughout the entire coil length.

4.1 Process Flow

  1. Raw Material Selection & Ingot Casting: High-purity stainless steel ingots or billets are sourced from certified mills. Chemical composition is verified via spectroscopic analysis (OES) prior to acceptance. Ultra-low carbon (L) grades are preferred for weldability and intergranular corrosion resistance.
  2. Hot Rolling / Piercing: Billets are heated to 1,150–1,250°C and hot-rolled to reduce cross-section. For seamless tubes, a piercing mill or plug mill is employed to create a hollow tube blank with controlled wall thickness and outer diameter.
  3. Hot Residual Stress Relief: The hot-rolled tube undergoes stress relief annealing at approximately 1,050–1,100°C followed by controlled cooling to relieve residual stresses and homogenize microstructure.
  4. Cold Drawing / Cold Rolling (for Seamless Tubes): The tube blank is cold-drawn through a series of calibrated dies to achieve precise final dimensions. This step imparts strain hardening, improving yield strength and dimensional tolerance to ±5% of nominal wall thickness.
  5. Solution Annealing & Pickling: The cold-worked tube is solution annealed at 1,050–1,150°C (grade-dependent) followed by rapid water quenching to dissolve carbides and restore full austenitic corrosion resistance. The tube is then acid-pickled (nitric/hydrofluoric acid blend) to remove oxide scale and restore a clean, passive surface.
  6. Coil Winding: The straightened tube is wound into a continuous helical coil using a precision coil-winding machine. The winding process is carefully controlled to maintain consistent coil diameter, prevent tube distortion, and minimize residual bending stresses. The winding radius is selected to ensure the coil can be uncoiled without kinking or flattening.
  7. Final Inspection & Testing: Each coil undergoes comprehensive quality verification (see Section 6).
  8. Packaging & Dispatch: Coils are packaged on wooden reels or steel cores with protective wrapping to prevent mechanical damage and surface contamination during transit.

4.2 Alternative: Welded Coil Tube Process

For larger diameters or specific applications, welded coil tubes may be produced via the following route:

  1. Stainless steel strip (cold-rolled coil) is fed through a forming roll set to create a tube shape.
  2. Longitudinal weld is formed using TIG (Tungsten Inert Gas), MIG (Metal Inert Gas), or laser welding.
  3. The welded tube is solution annealed and pickled to homogenize the weld zone.
  4. The tube is wound into a coil configuration.

5. Applications

The stainless steel coil tube is employed across a broad spectrum of industrial, commercial, and specialized applications where corrosion resistance, thermal efficiency, and mechanical reliability are paramount.

5.1 Heat Exchanger Systems