Stainless Steel Coil Tube (Coil Tube) — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (product reference No. 1688) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous coil of stainless steel tubing, specifically designed for integration into Fan Coil Units (FCUs), Air Handling Units (AHUs), and other Heating, Ventilation, and Air Conditioning (HVAC) systems. This product represents a critical component in thermal exchange applications, where the coil tube serves as the primary heat transfer medium between refrigerant or hot water and the ambient air stream.
Unlike conventional carbon steel coil tubes, the stainless steel variant offers superior corrosion resistance, extended service life, and enhanced hygienic performance — making it particularly suitable for environments demanding high standards of durability and cleanliness, such as pharmaceutical facilities, food processing plants, and commercial HVAC installations.
Material & Properties
Base Material Composition
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, with the following typical specifications:
- Grade 304 (UNS S30400): Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, Manganese (Mn) ≤ 2.0%, Carbon (C) ≤ 0.08%. Offers excellent general-purpose corrosion resistance and weldability.
- Grade 316 (UNS S31600): Chromium (Cr) 16–18%, Nickel (Ni) 10–14%, Molybdenum (Mo) 2–3%, Carbon (C) ≤ 0.08%. Provides enhanced resistance to pitting and crevice corrosion in chloride-containing environments.
- Grade 316L (UNS S31603): Low-carbon variant of 316 (C ≤ 0.03%), optimized for welding applications requiring resistance to intergranular corrosion.
Mechanical Properties
- Tensile Strength: ≥ 515 MPa (75,000 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation at Break: ≥ 40%
- Hardness: ≤ 210 HB (Brinell Hardness Number)
- Thermal Conductivity: 14.9 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +870°C
Surface Finish
The coil tube is available in multiple surface finishes to meet specific application requirements:
- 2B Finish: Standard cold-rolled, annealed, and pickled surface; suitable for general HVAC applications.
- No. 4 Brushed Finish: Directional grain pattern; aesthetic appeal for visible installations.
- Mirror Polish (8K): Ra ≤ 0.2 μm; used in pharmaceutical and food-grade applications requiring high hygienic standards.
- Pickled & Passivated: Removal of oxide scale followed by passivation treatment to restore maximum corrosion resistance.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (1/8" – 1") | ASTM A269 / ASTM A213 |
| Wall Thickness | 0.3 mm – 1.5 mm | ASTM A269 / GB/T 12771 |
| Coil Length (Continuous) | Up to 500 m per coil | Manufacturer Specification |
| Coil Inner Diameter | 500 mm – 1,200 mm | Customizable |
| Dimensional Tolerance (OD) | ±0.10 mm (±0.004") | ASTM A269 |
| Dimensional Tolerance (Wall) | ±10% of nominal | ASTM A213 |
| Roundness Tolerance | ≤ 1% of nominal OD | ISO 1128 |
| Straightness | ≤ 2 mm/m | Manufacturer Specification |
| End Condition | Plain cut, chamfered, or deburred | Customizable |
| Applicable Standards | ASTM A269, ASTM A213, ASME SA-269, EN 10216-5, GB/T 12771 | — |
| Maximum Operating Pressure | Up to 1.6 MPa (232 psi) | ASME B31.5 |
| Hydrostatic Test Pressure | 1.5 × Working Pressure | GB/T 24511 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, material integrity, and surface quality:
- Raw Material Selection: Stainless steel strip or seamless tube blanks are sourced from certified mills (e.g., POSCO, Outokumpu, Taigang Stainless) with full mill test certificates (MTC) in accordance with EN 10204 Type 3.1.
- Forming & Welding: Cold-rolled steel strip is fed through a roll-forming die set to achieve the target OD and wall thickness. The longitudinal seam is welded using Tungsten Inert Gas (TIG) welding (GTAW process, ISO 4063 code 141) with argon shielding gas (99.99% purity) to minimize oxidation and ensure a penetration-free weld.
- Weld Annealing (Solution Heat Treatment): The welded coil is passed through an induction annealing furnace at temperatures of 1,050°C – 1,150°C, followed by rapid cooling. This process dissolves carbide precipitates, restores full austenitic microstructure, and eliminates residual stresses from welding.
- Pickling & Passivation: The annealed coil is treated in a mixed acid bath (nitric acid + hydrofluoric acid) to remove heat scale, followed by a nitric acid passivation treatment to form a protective chromium oxide passive film.
- Surface Finishing: Optional polishing, brushing, or electropolishing operations are performed to achieve the specified surface roughness (Ra) values.
- Coiling & Winding: The finished tube is coiled onto precision steel cores using a controlled-tension winding system to prevent kinking, deformation, or surface damage.
- Quality Inspection: Each coil undergoes comprehensive inspection including dimensional measurement, visual examination, and destructive/non-destructive testing (NDT).
Quality Control Methods
- Visual Inspection: 100% examination of surface quality, weld seam appearance, and coil uniformity.
- Dimensional Inspection: OD, wall thickness, and coil diameter measured using calibrated micrometers and ultrasonic thickness gauges.
- Hydrostatic Testing: All coils tested at 1.5× working pressure with zero leakage tolerance.
- Intergranular Corrosion Test: Conducted per ASTM A262 Practice No. 1A (Etching in 50% H₂SO₄ + 2% CuSO₄) for grades 304L and 316L.
- Spectroscopic Analysis: Optical Emission Spectroscopy (OES) verification of chemical composition for every heat number.
- Weld Seam Testing: Penetrant Testing (PT) per ASTM E165 or Eddy Current Testing (ECT) per ASTM E709 for weld integrity verification.
Applications
Primary Applications
- Fan Coil Units (FCUs): The coil tube serves as the heat exchanger core in both chilled-water and hot-water FCUs, providing precise temperature control in commercial buildings, hospitals, and residential HVAC systems.
- Air Handling Units (AHUs): Integration into large-capacity AHU coils for central air conditioning systems in commercial and industrial facilities.
- Radiators & Convectors: Use in hydronic heating systems where corrosion-resistant, long-life heat transfer elements are required.
Industry-Specific Applications
- Pharmaceutical Industry: GMP-compliant HVAC systems requiring hygienic, easy-to-sanitize coil tubes with mirror-polished surfaces.
- Food & Beverage Processing: Temperature-controlled processing environments where resistance to acidic and caustic cleaning agents is critical.
- Marine & Offshore: HVAC systems in vessels and offshore platforms exposed to salt-laden atmospheres, where Grade 316 provides essential chloride resistance.
- Electronics Manufacturing: Cleanroom HVAC systems requiring ultra-low particulate emission and high purity thermal exchange.
- Chemical Processing: HVAC systems in plants handling aggressive chemicals where standard carbon steel would corrode rapidly.
Quality Certifications & Compliance
Management System Certifications
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health & Safety Management Systems
Product & Material Certifications
- Mill Test Certificates (MTC): Issued per EN 10204 Type 3.1 for every production lot, documenting chemical composition, mechanical properties, and heat treatment parameters.
- CE Marking: Conformity with EU Pressure Equipment Directive (PED 2014/68/EU) where applicable.
- Material Traceability: Full heat-number traceability from raw steel mill through to finished coil delivery.
Test & Inspection Reports
- Hydrostatic pressure test reports per GB/T 24511 or ASTM A269
- Intergranular corrosion test reports per ASTM A262
- Surface roughness measurement reports per ISO 4287
- Non-destructive testing (NDT) reports per applicable ASTM standards
- Third-party inspection available upon request (SGS, Bureau Veritas, TÜV)
Unique Selling Points
- Superior Corrosion Resistance: Austenitic stainless steel construction eliminates the risk of internal and external corrosion that plagues carbon steel alternatives, extending service life by 5–10× in aggressive environments.
- Hygienic Design: Mirror-polished surface options (Ra ≤ 0.2 μm) prevent microbial adhesion, making the coil tube compliant with pharmaceutical GMP and food-grade sanitation requirements.
- Continuous Coil Format: Delivered as a continuous coil (up to 500 m) enabling seamless integration with automated coil-forming and coil-bundling machinery, reducing installation labor and material waste.
- Full Traceability: Every coil is traceable to its steel mill heat number, ensuring complete supply-chain transparency and quality accountability.
- Customization Capability: Wenzhou Jixing offers flexible customization of OD, wall thickness, surface finish, coil dimensions, and end conditions to meet project-specific engineering requirements.
- Comprehensive Testing: Multi-stage quality assurance including hydrostatic testing, spectroscopic analysis, intergranular corrosion testing, and NDT ensures batch-to-batch consistency.
- International Standard Compliance: Products manufactured to ASTM, ASME, EN, and GB standards, facilitating global market acceptance and regulatory compliance.
Note: All specifications listed above are representative values based on standard production configurations. Custom specifications, non-standard grades, and special surface treatments are available upon request. Wenzhou Jixing Metal Materials Co., Ltd. recommends that end-users verify all dimensional tolerances and material certifications against project-specific engineering drawings and applicable codes prior to procurement.