Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered tubular product supplied in continuous coil form. Unlike conventional straight-length stainless steel tubes, coil tubes are wound onto standardized reels, offering superior logistics efficiency, reduced material waste during downstream processing, and seamless integration into automated manufacturing lines. This product line is particularly valued in the HVAC (Heating, Ventilation, and Air Conditioning), heat exchange, fluid transport, and process engineering industries.
The coil tube design facilitates continuous forming operations such as bending, welding, and assembly, making it an ideal feedstock for the production of fan coil units, heat exchangers, refrigeration coils, and industrial piping systems. The product aligns with the operational principles studied in virtual simulation environments for HVAC system regulation, where coil tube geometry and thermal conductivity play critical roles in system performance.
2. Material & Properties
2.1 Grade Selection
- AISI 304 (UNS S30400): The most widely used austenitic stainless steel grade, offering excellent corrosion resistance, formability, and weldability. Suitable for general-purpose HVAC and food-grade applications.
- AISI 316 (UNS S31600): Enhanced corrosion resistance due to molybdenum (Mo) addition, ideal for chemical processing, marine, and high-chloride environments.
- AISI 321 (UNS S32100): Titanium-stabilized austenitic grade providing superior resistance to intergranular corrosion at elevated temperatures.
- AISI 316L (UNS S31603): Low-carbon variant of 316, offering improved weldability and resistance to sensitization.
2.2 Key Mechanical and Physical Properties
| Property | AISI 304 | AISI 316 | AISI 321 |
|---|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ≥ 515 MPa | ≥ 515 MPa |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ≥ 205 MPa | ≥ 205 MPa |
| Elongation (A50mm) | ≥ 40% | ≥ 35% | ≥ 40% |
| Density | 8.00 g/cm³ | 8.00 g/cm³ | 8.00 g/cm³ |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | 16.3 W/(m·K) |
| Maximum Service Temperature | 870°C | 870°C | 900°C |
| Corrosion Resistance | Good | Excellent | Good |
2.3 Chemical Composition (Typical, wt%)
| Element | C | Cr | Ni | Mo | Ti | Si | Mn | P | S |
|---|---|---|---|---|---|---|---|---|---|
| 304 | ≤ 0.08 | 18.0–20.0 | 8.0–10.5 | — | — | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 |
| 316 | ≤ 0.08 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 |
| 321 | ≤ 0.08 | 17.0–19.0 | 9.0–12.0 | — | 5×C–0.40 | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 |
3. Product Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Outer Diameter (OD) | 3.0 mm – 108 mm (customizable) |
| Wall Thickness (WT) | 0.3 mm – 4.0 mm |
| Coil Inner Diameter (ID) | 200 mm – 600 mm (standard: 300 mm / 500 mm) |
| Coil Length per Reel | 50 m – 200 m (typical); up to 500 m for thin-wall grades |
| Surface Finish | 2B (Cold Rolled and Annealed), BA (Bright Annealed), No. 4 Brushed, Mirror (8K) |
| Manufacturing Standard | ASTM A213/A269, EN 10216-5, GB/T 14976, JIS G3447 |
| Tolerance (OD) | ±0.05 mm (precision); ±0.10 mm (commercial) |
| Tolerance (WT) | ±10% of nominal wall thickness |
| Coil Weight per Reel | 200 kg – 1,000 kg (configurable) |
| Packaging | Wooden pallet with VCI (Vapor Corrosion Inhibitor) paper wrapping; seaworthy export packaging available |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous multi-stage manufacturing workflow:
- Raw Material Procurement: High-purity stainless steel strip or plate sourced from certified mill suppliers (e.g., POSCO, Outokumpu, Taigang) with full mill test certificates (MTC) per EN 10204 Type 3.1.
- Strip Preparation & Leveling: Incoming strip undergoes edge milling, leveling, and surface inspection to ensure uniform thickness and freedom from defects such as rolls marks, scratches, or oxide inclusions.
- Punching & Slitting: Precision slitting lines cut the strip to the required width for the target tube outer diameter, with CNC-controlled blade positioning for dimensional accuracy.
- Forming (Roll Forming): Multi-station roll forming machines progressively bend the flat strip into a tubular shape. For larger diameters, a combination of roll forming and hydraulic pressing is employed.
-
Welding: Longitudinal seam welding is performed using either:
- Automatic Argon Arc Welding (TIG): For larger diameters and thicker walls, ensuring high-quality weld beads.
- High-Frequency Induction Welding (HF): For smaller diameters and thin walls, providing rapid, high-integrity welds with minimal heat-affected zone (HAZ).
- Post-Weld Heat Treatment (PWHT): Solution annealing at 1050–1150°C followed by controlled water quenching to restore full austenitic microstructure, eliminate residual stresses, and maximize corrosion resistance.
- Pickling & Passivation: Acid pickling (HNO₃/HF blend) removes weld scale and oxidation. Subsequent passivation with nitric acid (HNO₃) establishes a chromium-rich passive oxide layer.
- Surface Finishing: Electropolishing, mechanical polishing, or brushing to achieve the specified surface finish (2B, BA, No. 4, or 8K mirror).
- Dimensional Inspection & Testing: In-line laser diameter measurement, ultrasonic wall thickness gauging, hydrostatic pressure testing (per ASTM A213), and visual inspection of weld seams.
- Coiling & Packaging: Tubes are wound onto precision coils using controlled tension systems to prevent deformation, then packaged for shipment.
5. Applications
The Stainless Steel Coil Tube finds extensive application across multiple industries:
- HVAC & Fan Coil Units: As the primary heat transfer element in fan coil air conditioning systems. The coil tube geometry and thermal conductivity directly influence the system's cooling and heating efficiency, as demonstrated in virtual simulation experiments for HVAC operation regulation. Optimized coil tube design ensures laminar flow, maximized heat exchange surface area, and minimal pressure drop.
- Heat Exchangers & Radiators: Continuous coil forming enables efficient production of serpentine heat exchangers, automotive radiators, and industrial process coolers.
- Refrigeration Systems: Evaporator and condenser coils for commercial refrigeration, cold storage, and cryogenic applications.
- Food & Beverage Processing: Hygienic-grade tubing for milk processing, brewing, pharmaceutical, and chemical transfer lines (316L grade preferred).
- Automotive & Transportation: Exhaust system components, fuel lines, brake lines, and HVAC ducting in passenger and commercial vehicles.
- Construction & Architecture: Decorative handrails, structural tubing, facade elements, and building services piping.
- Medical Equipment: Endoscopic instrument tubing, surgical tool shafts, and medical gas delivery systems requiring biocompatibility and sterilizability.
- Oil & Gas: Subsea piping, wellhead components, and offshore platform structural tubing (duplex or super-austenitic grades available upon request).
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework:
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health and Safety Management Systems
- EN 10204 — Delivery Inspection Documents (Type 3.1 Mill Test Certificates)
- ASTM A213 / A269 — Standards for seamless and welded austenitic stainless steel tubing
- EN 10216-5 — European standard for welded stainless steel tubes for pressure purposes
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for fluid transport
- PED (Pressure Equipment Directive 2014/68/EU) — Compliance for pressure-containing applications
- CE Marking — Conformity with European health, safety, and environmental protection standards
- NSF/ANSI 61 — Drinking water system components certification (for food-grade applications)
- 3-A Sanitary Standards — For dairy and food processing industry applications
7. Unique Selling Points (USP)
Wenzhou Jixing Metal Materials Co., Ltd — Engineering Excellence in Stainless Steel Coil Tube Solutions
- Continuous Coil Format Advantage: Eliminates butt-weld joints inherent in straight-length tubing, reducing leak points and improving system integrity. Enables high-speed automated forming, bending, and assembly operations.
- Full Traceability: Every coil is serialized and traceable to its mill