Stainless Steel Coil Tube (Coil Tube) — Product Technical Specification

1. Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coil Tube") is a precision-engineered continuous tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Wenzhou Jixing). This product is formed by cold-drawing or hot-rolling stainless steel wire into a continuous helical or serpentine coil configuration, offering superior thermal conductivity, mechanical integrity, and corrosion resistance. The Coil Tube is widely employed in HVAC (Heating, Ventilation, and Air Conditioning) systems, refrigeration heat exchangers, industrial fluid transport, and advanced thermal management applications where energy efficiency and long service life are critical.

Building upon research in deep reinforcement learning (DRL) for fan coil unit (FCU) control optimization targeting indoor thermal comfort, the Coil Tube serves as a foundational component in next-generation energy-efficient building systems. Its consistent geometry and material homogeneity enable predictable thermal performance, which is essential for algorithm-driven climate control strategies.

2. Material & Properties

The Coil Tube is fabricated from high-grade austenitic stainless steel, with the following primary material options:

• Grade 304 (UNS S30408 / 1.4301): The most widely used austenitic stainless steel, offering excellent corrosion resistance, weldability, and formability. Suitable for general industrial and HVAC applications.
• Grade 316 (UNS S31608 / 1.4401): Enhanced corrosion resistance due to 2–3% molybdenum (Mo) content, ideal for marine environments, chemical processing, and aggressive fluid media.
• Grade 321 (UNS S32103 / 1.4541): Titanium-stabilized austenitic steel with superior resistance to intergranular corrosion at elevated temperatures (450–850 °C).
• Grade 316L (UNS S31603 / 1.4435): Low-carbon variant of 316 with improved weldability and resistance to sensitization.

Mechanical Properties (Typical — Grade 304 Annealed)

• Tensile Strength (UTS): ≥ 520 MPa (75,400 psi)
• Yield Strength (0.2% offset): ≥ 205 MPa (29,700 psi)
• Elongation at Break: ≥ 40%
• Density: 8.0 g/cm³
• Thermal Conductivity (20 °C): 16.3 W/(m·K)
• Thermal Expansion Coefficient (20–100 °C): 17.3 × 10⁻⁶ /K
• Operating Temperature Range: −196 °C to +870 °C

3. Specifications

Parameter	Specification Range	Standard Reference
Outer Diameter (OD)	Φ3.0 mm – Φ50.8 mm (1/8" – 2")	ASTM A213 / A269
Wall Thickness	0.3 mm – 3.0 mm	EN 10217-7
Coil Pitch	10 mm – 100 mm (customizable)	Manufacturer specification
Coil Diameter	Φ100 mm – Φ2000 mm	Manufacturer specification
Tube Length per Coil	5 m – 200 m (continuous)	—
Surface Finish	Ba & Bright Annealed (BA), No. 1, No. 4, No. 8 (Mirror)	ASTM A480
Tolerance on OD	±0.05 mm to ±0.20 mm (per grade)	ASTM A213
Tolerance on Wall Thickness	±10% (standard), ±5% (precision grade)	EN 10217-7
Pressure Rating	Up to 30 MPa (depending on OD and wall thickness)	ASME B31.3
End Condition	Plain, beveled, or capped	Per customer requirement
Packaging	Wooden pallet with moisture-proof wrapping; steel banding	ISO 4126

4. Manufacturing Process

The production of the Stainless Steel Coil Tube at Wenzhou Jixing follows a rigorous multi-stage manufacturing sequence:

1. Raw Material Selection: Virgin stainless steel wire rod or seamless pipe blanks are sourced from certified mills, verified via mill test certificates (MTC) for chemical composition and mechanical properties.
2. Pickling and Descaling: Raw material undergoes acid pickling (HNO₃/HF blend) to remove oxide scale, ensuring a clean base surface.
3. Forming / Cold Drawing: The tube blank is drawn through precision tungsten carbide (WC) dies to achieve target OD and wall thickness dimensions with tight tolerances.
4. Coil Forming: The formed tube is continuously wound into a helical or serpentine coil using CNC-controlled coiling equipment, ensuring uniform pitch and concentricity.
5. Stress Relief Annealing: The coiled product is annealed at 1050–1150 °C followed by controlled cooling to relieve residual stresses and restore full austenitic microstructure.
6. Pickling and Passivation: Post-annealing pickling removes heat scale; passivation treatment forms a protective chromium oxide (Cr₂O₃) passive film to enhance corrosion resistance.
7. Surface Finishing: Optional polishing (electrolytic or mechanical) achieves specified surface roughness (Ra ≤ 0.4 μm for mirror finish).
8. Quality Inspection: 100% visual inspection, dimensional verification (OD, wall thickness, coil pitch), hydrostatic pressure testing, and optional eddy current testing for internal defect detection.
9. Packaging and Dispatch: Protected packaging with desiccants and export-grade labeling for domestic and international shipment.

5. Applications

• HVAC Systems: Heat exchanger coils in air handlers, fan coil units (FCU), and rooftop units — enabling deep reinforcement learning–based optimal control for indoor thermal comfort.
• Refrigeration and Cryogenics: Evaporator and condenser coils in commercial refrigeration, cold storage, and industrial cooling systems.
• Automotive Industry: Radiator cores, intercooler tubes, and exhaust heat recovery systems.
• Food and Beverage Processing: Sanitary heat exchangers, pasteurization systems, and CIP (Clean-In-Place) compatible fluid transfer coils.
• Chemical and Pharmaceutical: Corrosion-resistant process coils for aggressive media handling and sterilization circuits.
• Marine and Offshore: Seawater heat exchangers and desalination plant components.
• Energy Sector: Solar thermal collectors, geothermal heat pump loops, and district heating distribution networks.
• Industrial Boiler Systems: Superheater and economizer tube coils for high-temperature steam generation.

6. Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains the following quality management and product certifications to assure global compliance:

• ISO 9001:2015 — Quality Management System certification for manufacturing excellence.
• ISO 14001:2015 — Environmental Management System certification.
• ISO 45001:2018 — Occupational Health and Safety Management System.
• EN 10204 3.1 — Material Test Certificate (third-party inspection available).
• ASME "S" Stamp — Authorized for Section VIII Division 1 pressure vessel components (where applicable).
• CE Marking (PED 2014/68/EU) — Conformity with European Pressure Equipment Directive.
• NORSOK M-650 — Compliance for offshore and subsea applications.
• 3-A Sanitary Standard — Food-grade hygienic design compliance.
• RoHS & REACH Compliance — Restriction of Hazardous Substances and chemical registration compliance.

7. Unique Selling Points

• Precision Geometry: CNC-controlled coil forming delivers uniform pitch and concentricity, ensuring predictable thermal and hydraulic performance — critical for algorithm-driven HVAC control optimization.
• Full Material Traceability: Every coil lot is traceable to the original mill heat number with complete chemical and mechanical test data.
• Customization Capability: Flexible OD, wall thickness, pitch, and coil diameter configurations to meet project-specific engineering requirements.
• Enhanced Corrosion Performance: Post-manufacture passivation and optional PTFE or PEEK internal coating options for extreme environments.
• Energy Efficiency Contribution: Optimized tube geometry reduces pressure drop while maximizing heat transfer surface area, directly contributing to lower energy consumption in fan coil unit systems.
• Global Delivery Network: Export-ready packaging and logistics infrastructure supporting worldwide supply chains.

Design Note: When integrating Stainless Steel Coil Tubes into smart HVAC systems employing deep reinforcement learning (DRL) for indoor thermal comfort optimization, consistent geometric tolerances and material property uniformity are paramount. Wenzhou Jixing's precision manufacturing ensures that the thermal response model embedded in the control algorithm accurately reflects real-world coil performance, minimizing control errors and maximizing occupant comfort.