Stainless Steel Coil Tube (Coiltube) — HVAC & Industrial Heat Exchanger Grade
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, the Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous tube product designed for demanding thermal management applications, including partitioned fan coil unit (FCU) workstation air conditioning systems, industrial heat exchangers, refrigeration circuits, and process piping. Delivered in continuous coil form, this product enables high-efficiency downstream forming, bending, and fabrication with minimal material waste and superior dimensional consistency.
Product Overview
The Stainless Steel Coil Tube is supplied as a cold-drawn or cold-rolled continuous coil, optimized for seamless integration into HVAC (Heating, Ventilation, and Air Conditioning) systems — particularly partitioned fan coil unit workstation air conditioning configurations where airflow organization and micro-environmental control are critical performance parameters. The coil form factor allows automated coil-to-tube heat exchanger manufacturing lines to achieve high throughput with consistent wall thickness, tight tolerances, and excellent surface finish.
This product is engineered to withstand cyclic thermal loading, chemical exposure from refrigerants and water treatment additives, and mechanical fatigue in continuous-duty HVAC and industrial applications. The seamless internal bore eliminates solder joints and potential leak points within heat transfer circuits.
Material & Properties
Material Grades
- AISI 304 / ASTM A213 TP304 — General-purpose austenitic stainless steel with excellent corrosion resistance and formability; the industry-standard grade for HVAC coil tube applications.
- AISI 316L / ASTM A213 TP316L — Enhanced molybdenum-bearing grade for aggressive chemical environments, marine HVAC systems, and pharmaceutical-grade applications.
- AISI 321 / ASTM A213 TP321 — Titanium-stabilized grade for elevated-temperature service in industrial process heat exchangers.
- AISI 310S / ASTM A213 TP310S — High-temperature austenitic grade for furnace and high-heat-flux applications.
Mechanical Properties (Typical Values for 304 Grade)
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa (74,700 psi) | ASTM A213 / ASTM A315 |
| Yield Strength (屈服强度) | ≥ 205 MPa (29,700 psi) | ASTM A213 |
| Elongation (伸长率) | ≥ 40% | ASTM A315 |
| Hardness (硬度) | ≤ 237 HB (annealed condition) | ASTM A262 |
| Thermal Conductivity (热导率) | 16.3 W/(m·K) at 20°C | ASTM E1461 |
| Thermal Expansion Coefficient (热膨胀系数) | 17.3 × 10⁻⁶ /°C | ASTM E228 |
| Maximum Service Temperature (最高使用温度) | 870°C (1,598°F) | ASTM A213 |
Corrosion Resistance
The austenitic stainless steel microstructure provides inherent resistance to atmospheric corrosion, pitting in chloride-containing environments (particularly 316L), and intergranular corrosion after stabilization heat treatment. Surface roughness of Ra ≤ 0.4 μm (annealed finish) further reduces fouling and biofilm adhesion in water-side applications.
Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (外径) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A213 / ASTM B407 |
| Wall Thickness (壁厚) | 0.3 mm – 3.0 mm | ASTM A315 |
| OD Tolerance (外径公差) | ±0.05 mm (±0.002") | ASTM A213 |
| Wall Thickness Tolerance (壁厚公差) | ±10% of nominal | ASTM A315 |
| Surface Finish (表面光洁度) | Ra 0.2 – 0.4 μm (electropolished available: Ra ≤ 0.1 μm) | ASTM A473 |
| Coil Weight (盘管重量) | 50 kg – 500 kg per coil | — |
| Coil Inner Diameter (盘管内径) | 150 mm – 400 mm | — |
| Condition (供货状态) | Annealed (A), Solution Treated (ST), Cold Worked (CW) | ASTM A213 |
| Length per Coil (每盘长度) | Continuous coil — 50 m to 2,000 m | — |
| End Condition (端面处理) | Deburred, chamfered, or laser-cut to length | — |
Manufacturing Process
1. Raw Material Selection & Ingot Casting
Virgin stainless steel billets are sourced from certified producers with full chemical composition traceability. The molten steel is cast using vacuum induction melting (VIM) or argon oxygen decarburization (AOD) processes to achieve low sulfur (S ≤ 0.02%) and low carbon (C ≤ 0.08% for 304) purity levels, ensuring consistent mechanical properties and corrosion performance.
2. Hot Rolling & Annealing
Ingots are reheated to 1,150–1,250°C and hot-rolled into seamless tube stock with controlled dimensional tolerances. The hot-rolled product undergoes a full annealing cycle (1,050–1,150°C) followed by controlled cooling to establish a fully recrystallized austenitic microstructure free of residual stresses.
3. Cold Drawing (Cold Reduction)
The seamless tube stock is cold-drawn through precision tungsten carbide tooling to achieve the final outer diameter and wall thickness. Cold drawing imparts beneficial strain hardening, tightens dimensional tolerances to ±0.05 mm, and produces a smooth internal bore surface critical for efficient heat transfer in fan coil unit heat exchanger applications.
4. Intermediate Annealing
Where significant cold reduction (>60%) is applied, intermediate solution annealing (1,050°C, air or controlled atmosphere cooling) is performed to restore ductility, eliminate work hardening, and prevent microcracking during subsequent forming operations.
5. Surface Treatment
- Pickle & Passivate (酸洗钝化) — Removal of mill scale and oxide films using citric acid or nitric-hydrofluoric acid solutions, followed by passivation to establish a protective chromium oxide layer (Cr₂O₃, thickness ≥ 2 nm).
- Electropolishing (电解抛光) — Available upon specification for Ra ≤ 0.1 μm surface finish, essential for pharmaceutical and food-grade HVAC applications.
6. Coil Winding & Packaging
The finished tube is wound onto precision coils with controlled tension to prevent kinking or ovality. Each coil is wrapped in protective PE film or kraft paper, secured with steel strapping, and labeled with heat number, grade, dimensions, and traceability documentation.
7. Non-Destructive Testing (无损检测)
- Eddy Current Testing (涡流检测) — 100% inspection of internal and external surface integrity per ASTM E709.
- Hydrostatic Testing (水压试验) — Performed at 1.5× working pressure for leak integrity verification per ASTM A213.
- Visual Inspection (目视检测) — Surface condition and dimensional verification at each production stage.
Applications
1. Partitioned Fan Coil Unit (FCU) Workstation Air Conditioning Systems
In partitioned fan coil unit workstation configurations, the stainless steel coil tube serves as the core heat transfer element within the air-side heat exchanger. The tube is formed into serpentine or zigzag fin-and-tube configurations where precise airflow organization (气流组织) is essential for achieving uniform temperature distribution and optimal micro-environmental comfort (微环境评价) at the workstation level. The corrosion resistance of 304/316L grade eliminates the risk of tube degradation in humid, chemically exposed indoor air environments, ensuring long-term thermal efficiency and air quality integrity.
2. Industrial Heat Exchangers
Used as tube bundles in shell-and-tube heat exchangers for chemical processing, petrochemical, and power generation applications where thermal cycling and chemical exposure demand superior material performance.
3. Refrigeration & Air Conditioning Circuits
Continuous coil form enables automated manufacturing of evaporator and condenser coils for commercial refrigeration units, chiller systems, and rooftop HVAC units.
4. Process Piping & Instrumentation
Deployed in pharmaceutical, food and beverage, and semiconductor manufacturing cleanroom HVAC systems where hygienic surface conditions and non-contamination properties are mandatory.
5. Solar Thermal & Geothermal Systems
Utilized in closed-loop solar thermal collectors and geothermal heat pump systems where long-term corrosion resistance and thermal fatigue performance are critical.
Quality Certifications
| Certification | Scope | Standard |
|---|---|---|
| ISO 9001:2015 | Quality Management System | ISO 9001 |
| ISO 14001:2015 | Environmental Management System | ISO 14001 |
| ISO/IEC 17025 | Testing & Calibration Laboratory Competence | ISO/IEC 17025:2017 |
| EN 10204 | Material Test Reports (Type 3.1) | EN 10204:2004 |
| ASTM A213 | Seamless Ferritic, Austenitic & Ferritic-Austenitic Alloy Steel Tubing | ASTM A213/A213M |
| ASTM A315 | Seamless & Welded Austenitic Stainless Steel Tubing for General Applications | ASTM A315/A315M |
| ASTM A269 | Seamless & Welded Austenitic Stainless Steel Tubing for Chemical Service | ASTM A269/A269M |
| NACE MR0175 | Sulfide Stress Cracking Resistance (for sour service) | NACE MR0175/ISO 15156 |
| CE Marking | European Conformity for pressure equipment | EU PED 2014/68/EU |
| NSF/ANSI 61 | Drinking Water System Components (available upon request) | NSF/ANSI 61 |
Unique Selling Points
1. Coil Form Factor Advantage: Continuous coil delivery eliminates butt-weld joints inherent in straight-length tube supply, reducing leak points by up to 95% in heat exchanger assemblies and enabling fully automated coil-to-tube manufacturing with cycle times reduced by 40%.
2. Precision Dimensional Control: Cold-drawing to ±0.05 mm OD tolerance ensures consistent fin-tube contact pressure in heat exchanger fabrication, directly translating to improved heat transfer coefficients (U-value improvement of 8–12% over standard-tolerance tube).
3. Full Traceability: Every coil is traceable to its heat number with complete mill test certificates (MTC), chemical composition analysis (spectrometric), mechanical test data, and non-destructive testing records — satisfying the most stringent audit requirements in pharmaceutical, aerospace, and nuclear-adjacent HVAC applications.
4. Application-Specific Optimization: Wenzhou Jixing Metal Materials provides grade selection consulting, surface finish customization, and coil dimension optimization specifically calibrated for partitioned fan coil unit workstation air conditioning system requirements, where precise airflow organization and micro-environmental performance are the defining engineering parameters.
Ordering Information
Customers are advised to specify the following parameters when placing orders:
- Grade (e.g., 304, 316L, 321, 310S)
- Outer Diameter × Wall Thickness (nominal dimensions)
- Surface Finish (annealed, pickled & passivated, electropolished)
- Coil Weight (target kg per coil)
- Condition (Annealed, Solution Treated, Cold Worked)
- End Treatment (as-coiled, cut to length, chamfered)
- Applicable Standards (ASTM A213, A315, A269, etc.)
- Special Requirements (NACE testing, NSF certification, custom packaging)