Stainless Steel Coil Tube — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) is a continuously wound tubular product formed from austenitic or duplex stainless steel strip, manufactured through a precision cold-rolling and forming process. Unlike seamless or welded straight pipe, coil tubes are delivered in continuous coil form, enabling high-efficiency downstream processing including straightening, cutting, bending, and heat exchanger assembly. These products are widely employed in heat exchangers, HVAC (Heating, Ventilation, and Air Conditioning) systems, chemical processing, food-grade equipment, and automotive radiators.
This specification covers coil tubes produced by Wenzhou Jixing Metal Materials Co., Ltd., designed to meet international standards including ASTM, EN (European Norms), JIS (Japanese Industrial Standards), and GB (Chinese National Standards).
2. Material Composition & Properties
2.1 Commonly Available Grades
- Austenitic Grades: SUS304 / AISI 304, SUS304L, SUS316 / AISI 316, SUS316L, SUS321, SUS310S
- Super Austenitic Grades: SUS904L (Alloy 20)
- Duplex Grades: SUS316L (modified), 2205 Duplex
- Other Special Grades: Custom compositions available upon request
2.2 Typical Chemical Composition (AISI 304 / SUS304)
| Element |
Carbon (C) |
Chromium (Cr) |
Nickel (Ni) |
Manganese (Mn) |
Silicon (Si) |
Phosphorus (P) |
Sulfur (S) |
| Max / Range (%) |
≤ 0.08 |
18.0 – 20.0 |
8.0 – 10.5 |
≤ 2.0 |
≤ 1.0 |
≤ 0.045 |
≤ 0.030 |
2.3 Mechanical Properties (Cold Rolled Condition)
| Property |
Value (AISI 304, Annealed) |
Test Standard |
| Tensile Strength (UTS) |
≥ 515 MPa (75 ksi) |
ASTM A270 / EN 10216-5 |
| Yield Strength (0.2% offset) |
≥ 205 MPa (30 ksi) |
ASTM A270 |
| Elongation (A₅₀) |
≥ 35% |
ASTM A270 |
| Density |
7.93 g/cm³ |
— |
| Thermal Conductivity (20°C) |
16.3 W/(m·K) |
— |
| Thermal Expansion Coefficient (20–100°C) |
17.2 × 10⁻⁶ /°C |
— |
| Corrosion Resistance |
Excellent in atmospheric, mild chemical, and food-grade environments |
ASTM A240 |
2.4 Surface Conditions
- 2B Finish: Cold-rolled, annealed, pickled, and light-tempered; smooth, semi-matte appearance
- No. 4 Finish: Uniformly matte, brushed surface with linear grain
- No. 8 / Mirror Finish: Highly polished, reflective surface (Ra ≤ 0.1 μm)
- Ba & Be (Bright Annealed): Maintains original surface luster without pickling
3. Dimensional Specifications
3.1 General Dimensions
| Parameter |
Range / Tolerance |
Standard Reference |
| Outer Diameter (OD) |
3.0 mm – 50.8 mm (⅛" – 2") |
ASTM A270 / EN 10216-5 |
| Wall Thickness (WT) |
0.25 mm – 3.0 mm (0.010" – 0.118") |
ASTM A270 |
| OD Tolerance |
±0.05 mm (±0.002") for OD ≤ 10 mm; ±0.1 mm (±0.004") for OD > 10 mm |
EN 10216-5 |
| WT Tolerance |
±10% of nominal thickness |
ASTM A270 |
| Coil Length |
Continuous, typically 50 m – 200 m per coil |
— |
| Coil Weight |
500 kg – 2,500 kg per coil |
— |
| Coil Inner Diameter (ID) |
150 mm / 200 mm / 300 mm (standard options) |
— |
3.2 Commonly Available Sizes (Selected)
| OD (mm) |
WT (mm) |
OD (inch) |
WT (inch) |
Typical Application |
| 6.35 |
0.50 |
¼" |
0.020" |
Radiator tubes |
| 8.00 |
0.50 |
⅜" |
0.020" |
Heat exchanger |
| 9.53 |
0.81 |
⅜" |
0.032" |
Automotive cooling |
| 12.70 |
1.00 |
½" |
0.040" |
HVAC coil tubes |
| 15.88 |
1.24 |
⅝" |
0.049" |
Industrial heat exchangers |
| 19.05 |
1.50 |
¾" |
0.059" |
Process piping |
| 25.40 |
1.65 |
1" |
0.065" |
Large heat exchangers |
| 31.75 |
2.00 |
1¼" |
0.079" |
Chemical processing |
| 38.10 |
2.50 |
1½" |
0.098" |
Heavy-duty applications |
| 50.80 |
3.00 |
2" |
0.118" |
Process & structural |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Preparation: Cold-rolled stainless steel strip (CRSS) supplied in coil form, typically in annealed (soft) condition with controlled chemical composition and surface quality.
- Strip Inspection & Uncoiling: Incoming strip undergoes visual inspection, thickness measurement (laser or micrometer), and chemical verification. The strip is mounted on a tension-controlled uncoiler.
- Forming (Tube Making): The flat strip is passed through a series of progressive roll-forming stations (typically 12–20 passes) that gradually bend the strip into a semi-circular profile and then close it into a tubular shape. Forming methods include:
- Welded Coil Tube (Fusion Welded): The closed tube is seam-welded using TIG (Tungsten Inert Gas) welding with high-purity argon shielding gas to ensure weld quality.
- ERW (Electric Resistance Welding): High-frequency or low-frequency resistance welding for thinner wall applications.
- Weld Heat Treatment / Annealing: The welded tube is subjected to controlled annealing (typically 1050°C – 1150°C for austenitic grades) followed by rapid cooling (water quench or air cool) to restore full solution-treated properties and eliminate welding sensitization.
- Pickling & Passivation: Annealed tubes undergo acid pickling (nitric-hydrofluoric acid blend) to remove oxide scale, followed by passivation to form a protective chromium oxide layer.
- Sizing & Straightening: The tube passes through sizing rolls to achieve precise dimensional tolerances on OD and WT. Straightening ensures the tube is free of helical distortion.
- Coiling: The finished tube is wound onto a coil core with controlled tension to prevent deformation, kinking, or surface marking during storage and transport.
- Final Inspection & Packaging: Each coil undergoes dimensional verification, surface quality inspection, and (where applicable) hydrostatic pressure testing. Coils are wrapped in protective film, sleeved, and secured for shipment.
4.2 Key Process Parameters
| Process Step |
Parameter |
Typical Value / Range |
| Forming Speed |
Production Rate |
10 – 60 m/min (depending on OD and WT) |
| TIG Welding |
Welding Current |
150 – 350 A (DC) |
| TIG Welding |
Shielding Gas Flow |
15 – 25 L/min (99.99% Ar) |
| Weld Annealing |
Temperature |
1050°C – 1150°C |
| Weld Annealing |
Holding Time |
10 – 30 minutes |
| Pickling |
Bath Temperature |
60°C – 80°C |
| Pickling |
Acid Concentration |
5% – 10% HNO₃ + 1% – 3% HF |
5. Applications
5.1 Primary Application Areas
- HVAC & Fan Coil Units (风机盘管): Stainless steel coil tubes serve as the core heat transfer element in fan coil units, air handling units, and chiller coils. The combination of high thermal conductivity, corrosion resistance, and formability makes stainless steel coil tubes ideal for precise coil winding in air-side heat exchangers. The pressure regulation and constant-speed matching methodology (调压定转速法) employed in fan coil unit systems benefits from the dimensional consistency and mechanical reliability of high-quality stainless steel coil tubes.
- Automotive Radiators & Intercoolers: Used in engine cooling systems, turbocharger intercoolers, and transmission oil coolers where resistance to coolant corrosion and thermal cycling fatigue is critical.
- Food & Beverage Processing: Heat exchangers, pasteurization equipment, and CIP (Clean-in-Place) systems in dairy, brewery, and pharmaceutical processing. SUS304 and SUS316L grades meet FDA and EU food-contact regulations.
- Chemical & Petrochemical Industry: Reactor cooling coils, distillation column internals, and process heat exchangers handling aggressive media. SUS316 and 904L grades provide superior resistance to chlorides and organic acids.
- Marine & Offshore Applications: Seawater coolers, ballast water system components, and desalination plant heat exchangers. Duplex and super-austenitic grades resist pitting and crevice corrosion in marine environments.
- Power Generation: Condenser tubes, boiler economizers, and waste heat recovery systems in thermal and nuclear power plants.
- Medical & Laboratory Equipment: Autoclave components, dialysis machine tubing, and analytical instrument fluid lines requiring biocompatibility and autoclavability.
5.2 Performance in Heat Exchanger Applications
In heat exchanger and fan coil unit applications, stainless steel coil tubes offer distinct advantages over copper and aluminum alternatives:
- Elimination of Galvanic Corrosion: When paired with stainless steel headers and fins, the absence of dissimilar metal contact eliminates galvanic corrosion entirely, a common failure mode in copper-aluminum systems.
- Long Service Life: Resistance to corrosion extends service life significantly, particularly in applications involving humid air, refrigerants, or mildly corrosive process fluids.
- Non-Toxic & Hygienic: No risk of metal ion leaching into food, beverage, or pharmaceutical products.
- Mechanical Durability: Higher yield strength compared to copper reduces risk of tube buckling and collapse under differential pressure.
6. Quality Certifications & Compliance
6.1 Applicable Standards
| Standard |
Title / Scope |
Region |
| ASTM A
|