Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered continuous tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in coiled form, enabling efficient storage, transportation, and downstream processing through automated forming, bending, and cutting operations. The coil tube is designed to meet the rigorous demands of industrial, HVAC, and fluid transport applications, offering superior corrosion resistance, mechanical integrity, and dimensional accuracy.
Unlike discrete-length tubing, the coiled configuration eliminates the need for welding joints during installation, thereby reducing potential failure points and enhancing system reliability. The continuous nature of the product also minimizes material waste and allows for customized cut-to-length solutions tailored to specific project requirements.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, including but not limited to:
- AISI 304 / SUS304 — General-purpose corrosion resistance with excellent formability
- AISI 304L / SUS304L — Low-carbon variant suitable for post-welding applications
- AISI 316 / SUS316 — Enhanced resistance to chlorides and aggressive chemical environments
- AISI 316L / SUS316L — Low-carbon 316 with superior weldability and long-term durability
- AISI 321 / SUS321 — Titanium-stabilized grade for high-temperature service up to 870°C (1600°F)
- AISI 310S / SUS310S — High-temperature oxidation resistance for extreme thermal environments
2.2 Mechanical Properties
- Tensile Strength: 515–700 MPa (depending on grade and cold-work condition)
- Yield Strength: 205–310 MPa
- Elongation: ≥35% (as-rolled condition)
- Hardness: 130–200 HV (annealed); up to 400 HV (cold-worked)
2.3 Surface Characteristics
- Surface Finish: BA (Bright Annealed), No.4 Brushed, No.8 Mirror, or 2B
- Roughness (Ra): 0.1–1.6 μm depending on finish grade
- Wall Thickness Tolerance: ±0.05 mm (precision grade)
2.4 Chemical Composition (Typical — AISI 304)
| Element | C (Carbon) | Si (Silicon) | Mn (Manganese) | P (Phosphorus) | S (Sulfur) | Cr (Chromium) | Ni (Nickel) | Fe (Iron) |
|---|---|---|---|---|---|---|---|---|
| Max/Min | 0.08% | 1.00% | 2.00% | 0.045% | 0.030% | 18.00–20.00% | 8.00–10.50% | Balance |
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code | 811 |
| Outer Diameter (OD) | Φ3.0 mm – Φ50.8 mm (customizable) |
| Wall Thickness | 0.3 mm – 3.0 mm |
| Coil Length | 50 m – 500 m (standard); up to 1000 m upon request |
| Coil Weight | 500 kg – 2000 kg per coil |
| Material Grades | 304, 304L, 316, 316L, 321, 310S, 321H |
| Standards | ASTM A269, ASTM A270, ASME SA-213, EN 10216-5, GB/T 12771 |
| Manufacturing Method | Seamless (Seamless Tube) or Welded (Welded Tube) |
| Surface Treatment | BA, No.4, No.8 Mirror, 2B, Pickled & Passivated |
| End Condition | Plain, Beveled, Threaded, or Custom |
| Temperature Range | −196°C to +870°C (grade-dependent) |
| Pressure Rating | Up to 25 MPa (design pressure varies by OD, WT, and grade) |
| Packaging | Steel drum, wooden crate, or export-grade pallet with moisture-proof wrapping |
| Moisture Resistance | Excellent — suitable for high-humidity and marine environments |
| Customization | Available — custom OD, WT, coil length, surface finish, and heat treatment |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage process to ensure dimensional precision, metallurgical quality, and surface integrity:
- Hot Rolling / Continuous Casting: Stainless steel billets are produced via continuous casting and subsequently hot-rolled into seamless tube blanks or flat strip for welded tube production.
- Heat Treatment (Solution Annealing): The tube blank is heated to 1010–1150°C (1850–2100°F) and rapidly quenched in air or water to achieve a fully austenitic microstructure, eliminating residual stresses and restoring ductility.
- Piercing and Elongation (Seamless Process): For seamless variants, the solid billet is pierced to form a hollow tube, then elongated through a series of reducing stands to achieve the target OD and wall thickness.
- Forming and Welding (Welded Process): For welded variants, flat stainless steel strip is cold-formed into a tubular shape and welded using Automatic Submerged Arc Welding (ASAW) or TIG (Tungsten Inert Gas) welding processes.
- Cold Drawing / Cold Rolling: The tube is drawn through precision dies to achieve tight dimensional tolerances, improved surface finish, and enhanced mechanical properties through work hardening.
- Pickling and Passivation: The tube is immersed in a hydrochloric or citric acid bath to remove oxide scale, followed by passivation treatment to form a protective chromium oxide layer on the surface.
- Surface Finishing: Depending on the specified finish (BA, No.4, No.8), the tube undergoes mechanical polishing, electrolytic polishing, or brush finishing to achieve the desired aesthetic and functional surface characteristics.
- Coiling: The finished tube is wound onto a precision coiling head to form a uniform, stable coil with controlled tension to prevent deformation or kinking.
- Quality Inspection: Each coil undergoes comprehensive non-destructive testing (NDT), including ultrasonic testing (UT), eddy current testing (ECT), and hydrostatic pressure testing, to verify wall thickness uniformity, weld integrity, and absence of internal defects.
- Packaging and Labeling: Coils are wrapped in moisture-proof film, secured with steel strapping, and placed in export-grade packaging with full traceability documentation.
5. Applications
The Stainless Steel Coil Tube finds extensive application across a wide range of industrial and commercial sectors:
5.1 HVAC and Fan Coil Units (FCU)
A critical application area involves the use of coil tubes in Fan Coil Units (FCU) for heating, ventilation, and air conditioning systems. The coil tube serves as the heat exchange medium within FCU evaporators and condensers. Special attention is given to the integrity of associated components, including the air exhaust valve, where cracking and failure analysis is essential to ensure long-term system reliability. The corrosion resistance and thermal conductivity of stainless steel coil tubes make them ideal for condensation-prone environments where carbon steel alternatives would fail.
5.2 Food and Beverage Processing
- Pasteurization and sterilization piping systems
- CIP (Clean-in-Place) system tubing
- Hygienic transfer lines for dairy, brewing, and pharmaceutical production
5.3 Chemical and Petrochemical Industry
- Transport of aggressive chemicals, acids, and solvents
- Heat exchanger tubes in chemical processing plants
- Reactor internals and catalyst support structures
5.4 Medical and Pharmaceutical Equipment
- Sterilization equipment (autoclaves, steam sterilizers)
- Pharmaceutical-grade fluid transfer systems
- Medical instrument manufacturing (surgical tools, endoscopes)
5.5 Architectural and Decorative Applications
- Handrails, balustrades, and structural framing
- Facade cladding and decorative trim
- Lighting fixtures and signage structures
5.6 Automotive and Aerospace
- Exhaust system components
- Fuel and hydraulic lines
- Structural tubing in lightweight vehicle designs
5.7 Marine and Offshore
- Ballast water systems and seawater piping
- Heat exchangers in marine propulsion systems
- Offshore platform piping for harsh, chloride-rich environments
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and holds the following certifications to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and customer satisfaction
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- CE Marking — Conformity with European Union health, safety, and environmental protection standards
- EN 10204 — 3.1 Inspection Certificate providing detailed material and test documentation for each batch
- ASME SA-213 / SA-269 — Compliance with American Society of Mechanical Engineers standards for austenitic stainless steel tubing
- GB/T 12771 — Conformity with Chinese National Standard for stainless steel welded tubes
- ASTM A269 / A270 — Compliance with ASTM International standards for austenitic stainless steel seamless and welded tubing
- Mill Test Reports (MTR) — Provided with every shipment, including chemical analysis, mechanical test results, and heat treatment records
- Third-Party Inspection — Available upon request through SGS, Bureau Veritas, or TÜV Rheinland
7. Unique Selling Points
Continuous Coil Configuration: Eliminates field welding joints, reducing installation time by up to 40% and minimizing potential failure points in critical service applications.
FCU-Specific Engineering: Product design incorporates lessons learned from air exhaust valve cracking analysis in Fan Coil Units, ensuring enhanced fatigue resistance and thermal cycling durability in HVAC heat exchange applications.
Multi-Grade Availability: Six standard austenitic stainless steel grades available from a single supplier, enabling seamless material selection across diverse operating environments without supply chain complexity.
Precision Dimensional Control: Cold-drawing and cold-rolling processes achieve wall thickness tolerances of ±0.05 mm and surface roughness as low as Ra 0.1 μm, meeting the most demanding OEM specifications.
Full Traceability: Every coil is serialized with a unique heat number linked to complete production records, chemical analysis, and non-destructive testing results, ensuring full product traceability from raw material to end application.
Customization Capability: Flexible manufacturing infrastructure supports custom OD, wall thickness, coil length, surface finish, and heat treatment specifications, enabling tailored solutions for specialized industrial applications.
Export-Grade Quality: Products manufactured to international standards (ASTM, ASME, EN, GB) with comprehensive certification packages, ensuring compliance with global regulatory and procurement requirements.
8. Technical Notes and Recommendations
Based on the analysis of air exhaust valve cracking in Fan Coil Units, the following technical recommendations are provided for optimal coil tube performance in HVAC applications:
- Material Selection: For FCU applications involving condensation and potential acid condensation (pH < 4.0), AISI 316L is recommended over 304 due to its superior resistance to chlorides and organic acids.