Stainless Steel Coil Tube (Coiltube) for HVAC Air Conditioning Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous tube product supplied in coiled form, specifically designed for use in heating, ventilation, and air conditioning (HVAC) systems. This product is particularly suited for air conditioning coil applications in painting workshops and industrial environments where precise temperature and humidity control is critical to maintaining optimal process conditions.
The coil tube is wound into a continuous helical or serpentine configuration, enabling efficient heat exchange performance within compact air conditioning units. The coiled geometry maximizes the surface area-to-volume ratio, facilitating superior thermal transfer between the refrigerant medium and the ambient air stream. This design is essential for achieving the precise control methods required in specialized industrial painting environments, where even minor fluctuations in temperature or humidity can compromise coating adhesion, drying rates, and final finish quality.
As a supplier of high-quality metal materials, Wenzhou Jixing Metal Materials Co., Ltd. provides coil tubes that meet the demanding specifications required for HVAC coil manufacturing, ensuring reliable performance, extended service life, and resistance to the corrosive environments commonly found in industrial painting facilities.
Material & Properties
Base Material Composition
The coil tube is fabricated from austenitic stainless steel grades, with the primary alloy designations being SAE 304 (UNS S30400) and SAE 316L (UNS S31603), selected based on the specific application requirements and environmental exposure conditions.
- SAE 304 (UNS S30400): The standard austenitic stainless steel grade offering excellent general corrosion resistance, good formability, and outstanding weldability. Composed of approximately 18% Chromium (Cr) and 8% Nickel (Ni), this grade is the preferred choice for standard HVAC coil applications in moderately corrosive environments.
- SAE 316L (UNS S31603): A low-carbon variant enhanced with 2–3% Molybdenum (Mo), providing superior resistance to pitting and crevice corrosion. This grade is recommended for painting workshop applications where exposure to chemical vapors, solvents, or chlorinated atmospheres is anticipated.
Mechanical Properties
- Tensile Strength (UTS): ≥ 515 MPa (SAE 304); ≥ 485 MPa (SAE 316L)
- Yield Strength (0.2% offset): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 92 HRB
- Thermal Conductivity: 16.3 W/(m·K) at 100°C (SAE 304); 14.6 W/(m·K) at 100°C (SAE 316L)
- Coefficient of Thermal Expansion: 17.3 × 10⁻⁶ /K (20–100°C)
Corrosion Resistance
The austenitic stainless steel coil tube exhibits exceptional resistance to atmospheric corrosion, acid solutions, and organic compounds. The passive chromium oxide film formed on the surface provides a self-healing protective layer, ensuring long-term integrity even in humid and chemically aggressive painting workshop environments. The SAE 316L grade demonstrates particular resilience against chloride-induced stress corrosion cracking (SCC), a critical consideration for facilities utilizing solvent-based coatings.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (1/8" – 1") | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.3 mm – 1.5 mm | ASTM A213 / GB/T 12771 |
| Coil Length (per roll) | 50 m – 500 m (customizable) | — | Coil Inner Diameter | 150 mm – 600 mm | — |
| Surface Finish | 2B (Cold Rolled & Annealed) / BA (Bright Annealed) / No. 4 Brushed | ASTM A480 / GB/T 4237 |
| Tube End Condition | Plain end / Beveled end / Threaded (upon request) | — |
| Manufacturing Method | Seamless / Welded (TIG/ERW) | ASTM A213 / EN 10216-5 |
| Temperature Range | −196°C to +870°C | — |
| Maximum Operating Pressure | Up to 4.0 MPa (dependent on OD/WT) | ASME B31.3 |
| Passivation Treatment | Citric acid passivation / Nitric acid passivation | ASTM A967 / GB/T 4237 |
Manufacturing Process
The production of high-quality stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality.
- Raw Material Selection: High-purity stainless steel billets or strip material conforming to ASTM A213 and GB/T 12771 specifications are procured from certified mills. Incoming materials undergo spectrographic analysis to verify chemical composition within specified tolerance limits.
- Hot Rolling & Annealing: The base material is hot-rolled to approximate dimensions and subsequently annealed in a controlled atmosphere to relieve residual stresses and achieve the desired austenitic microstructure.
- Cold Drawing / Cold Rolling: Precision cold working reduces the tube to final dimensional specifications. This process enhances mechanical properties through work hardening while maintaining tight dimensional tolerances (±0.05 mm for OD, ±0.02 mm for wall thickness).
- Intermediate Annealing: Periodic annealing cycles are performed during cold working to restore ductility and prevent cracking, particularly critical for thin-wall configurations used in HVAC coil applications.
- Coil Winding: The continuous tube is wound into coils using precision winding equipment that maintains uniform tension to prevent kinking, ovality, or surface damage. Coil diameter and length are optimized for downstream HVAC coil manufacturing processes.
- Surface Treatment & Passivation: Tubes undergo mechanical cleaning, descaling, and chemical passivation (per ASTM A967) to establish a robust chromium oxide passive film. Bright Annealed (BA) finish is achieved through protective atmosphere annealing for applications requiring superior surface reflectivity and corrosion resistance.
- Quality Inspection: Final products undergo comprehensive inspection including dimensional verification (OD, WT, roundness), hydrostatic pressure testing, visual surface examination, and optional eddy current testing to detect internal or surface defects.
Applications
Primary Application: Painting Workshop HVAC Systems
The principal application domain for this coil tube product is the fabrication of air conditioning coils for industrial painting workshops. As documented in technical studies on precise control methods for painting workshop HVAC systems, the coil tube serves as the core heat exchange element within air conditioning units that maintain tightly controlled environmental conditions essential for paint application and curing processes.
- Temperature Control Coils: The coil tube is formed into serpentine or helical configurations within air handling units (AHUs) to precisely regulate workshop temperature, typically maintained within ±1°C of the setpoint to ensure consistent paint viscosity and drying characteristics.
- Dehumidification Coils: Condensing coils fabricated from this coil tube remove moisture from the air stream, maintaining relative humidity (RH) between 40–60% to prevent coating defects such as blushing, running, or poor adhesion.
- Refrigerant Circulation: The coil tube serves as the conduit for refrigerant flow (R-410A, R-134a, or similar), with its smooth internal bore minimizing flow resistance and pressure drop.
Additional Applications
- Industrial process cooling and heating systems
- Automotive paint shop HVAC installations
- Aerospace component coating facilities
- Food and pharmaceutical processing equipment heat exchangers
- Marine and offshore HVAC systems (SAE 316L grade)
- Commercial and residential air conditioning units
- Chilled water distribution systems
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and ensures all coil tube products comply with the following international and national standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices
- ASTM A213 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High-Temperature Service
- ASTM A480 — Standard Specification for Stainless Steel Chromium Sheet and Strip
- ASTM A967 — Standard Practice for Chemical Passivation of Stainless Steel Parts
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes
- GB/T 4237 — Chinese National Standard for Cold-Rolled Stainless Steel Sheets and Strips
- EN 10216-5 — European Standard for Stainless Steel Tubes for Pressure Purposes
- ASME B31.3 — Process Piping code compliance for pressure-containing applications
- RoHS & REACH — Compliance with European Union directives on restriction of hazardous substances and chemical safety
Each batch of coil tube is accompanied by a Mill Test Certificate (MTC) documenting chemical composition, mechanical properties, and dimensional verification results. Third-party inspection by agencies such as SGS, Bureau Veritas, or TUV is available upon customer request.
Unique Selling Points
Precision Engineering for Critical HVAC Applications: The coil tube is specifically optimized for the demanding requirements of painting workshop air conditioning systems, where precise temperature and humidity control is paramount to coating quality.
- Superior Corrosion Resistance: The austenitic stainless steel composition with optional molybdenum enhancement provides exceptional durability in chemically aggressive painting environments, extending service life significantly compared to carbon steel alternatives.
- Dimensional Consistency: Tight manufacturing tolerances ensure uniform coil geometry, facilitating reliable and repeatable heat exchanger fabrication with predictable thermal performance.
- Full Traceability: Each coil is traceable to its mill heat number, enabling complete supply chain transparency and quality accountability.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers flexible customization of OD, wall thickness, coil length, and surface finish to meet specific HVAC coil design requirements.
- Process-Oriented Expertise: Drawing from extensive knowledge of painting workshop HVAC precise control methodologies, the product is engineered to support advanced control strategies including variable refrigerant flow modulation and multi-zone temperature regulation.