Stainless Steel Coil Tube (Coiltube) — Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Reference No.: 365
Classification: Literature Study / Technical Reference
Applicable Standard Reference: JB/T 9066—1999 Thermal Performance Test Analysis of Cabinet Fan Coil Units
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured in continuous coil form, designed primarily for integration into HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly cabinet fan coil units (FCUs). This product is engineered to serve as the core heat exchange element within air-handling equipment, where efficient thermal transfer between a fluid medium (water, refrigerant, or steam) and ambient air is critical to system performance.
Wenzhou Jixing Metal Materials Co., Ltd. produces these coil tubes to meet the rigorous thermal and mechanical requirements outlined in industry standards such as JB/T 9066—1999, which governs the thermal performance testing methodology for cabinet-type fan coil units. The coil tube's geometry, material composition, and surface finish are all optimized to maximize heat exchange efficiency while maintaining structural integrity under cyclic thermal loading conditions.
2. Material and Properties
2.1 Base Material
- Primary Alloy: Austenitic stainless steel (奥氏体不锈钢), typically Grade 304 (UNS S30400) or Grade 316L (UNS S31603), selected based on application-specific corrosion resistance requirements.
- Equivalent Standards: ASTM A213, EN 10216-5, GB/T 14976
- Material Form: Cold-rolled coil (冷轧盘管), supplied as continuous strip coiled for downstream forming operations.
2.2 Key Mechanical Properties
- Tensile Strength (抗拉强度): 515–730 MPa (Grade 304); 515–585 MPa (Grade 316L)
- Yield Strength (屈服强度): ≥ 205 MPa
- Elongation (延伸率): ≥ 40% (Grade 304); ≥ 35% (Grade 316L)
- Hardness (硬度): ≤ 220 HV (annealed condition)
2.3 Thermal and Corrosion Properties
- Thermal Conductivity (导热系数): 14.9–16.3 W/(m·K) at 20°C
- Specific Heat Capacity (比热容): 498–502 J/(kg·K)
- Corrosion Resistance (耐腐蚀性): Excellent resistance to atmospheric corrosion, weak acids, and chlorinated environments (Grade 316L)
- Operating Temperature Range (工作温度范围): −196°C to +870°C (Grade 304); −273°C to +425°C (Grade 316L, limited by chromium carbide precipitation)
2.4 Chemical Composition (Typical, wt%)
| Element | Grade 304 (UNS S30400) | Grade 316L (UNS S31603) |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.03 |
| Chromium (Cr) | 18.00 – 20.00 | 16.00 – 18.00 |
| Nickel (Ni) | 8.00 – 10.50 | 10.00 – 14.00 |
| Molybdenum (Mo) | — | 2.00 – 3.00 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Sulfur (S) | ≤ 0.03 | ≤ 0.03 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
3. Specifications
| Parameter | Specification / Range | Test Method / Standard |
|---|---|---|
| Outer Diameter (OD, 外径) | 6.0 mm – 32.0 mm | GB/T 1804-m |
| Wall Thickness (壁厚) | 0.5 mm – 2.0 mm | GB/T 1804-f |
| Coil Length (盘管长度) | 3 m – 120 m (continuous) | Manufacturer's specification |
| Coil Inner Diameter (ID, 盘管内径) | 200 mm – 600 mm | — |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (mirror finish available on request) | GB/T 1031 |
| Roundness Tolerance (圆度公差) | ± 0.1 mm | GB/T 14976 |
| Straightness (直线度) | ≤ 1.0 mm/m | — |
| Hydrostatic Test Pressure (水压试验压力) | 1.5 × Working Pressure | GB/T 241 |
| Heat Exchange Efficiency (换热效率) | ≥ 85% (referenced to JB/T 9066—1999 test protocol) | JB/T 9066—1999 |
| Maximum Operating Pressure (最大工作压力) | 1.6 MPa (standard); up to 4.0 MPa (custom) | — |
| Maximum Operating Temperature (最高工作温度) | 120°C (water-based); 180°C (oil-based) | — |
| Coil Weight (盘管重量) | 5 kg – 500 kg per coil | — |
| Customization (定制选项) | OD, wall thickness, coil length, end treatment, surface finish | Per customer drawing |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical quality, and thermal performance consistency.
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Raw Material Selection and Inspection (原材料选型与检验):
Virgin stainless steel coil (hot-rolled coil, HRC) sourced from certified mills is received and subjected to incoming quality inspection, including chemical composition verification via Optical Emission Spectrometry (OES, 光学发射光谱法) and mechanical property testing.
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Acid Pickling and Passivation (酸洗钝化):
The hot-rolled coil undergoes acid pickling in a nitric acid/hydrofluoric acid (HNO₃/HF) solution to remove mill scale and surface oxides. Subsequent passivation treatment forms a protective chromium oxide (Cr₂O₃) layer on the surface, enhancing corrosion resistance.
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Cold Rolling (冷轧):
The cleaned coil is cold-rolled to the target thickness with precise roll gap control. This process induces work hardening, improves surface finish, and establishes dimensional tolerances within ± 0.05 mm.
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Interpass Annealing (中间退火):
Where multiple rolling passes are required, intermediate annealing in a controlled atmosphere furnace (1100°C ± 20°C, followed by rapid cooling) relieves work-hardening stresses and restores ductility for further deformation.
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Tubular Forming (制管成型):
The cold-rolled strip is formed into tube geometry using one of the following methods:
- Seam-welded tube (焊管): Transverse or longitudinal resistance welding with full penetration and controlled heat-affected zone (HAZ, 热影响区) management.
- Weldless/autoclaved tube (无焊管): Forged or extruded seamless tubes for high-pressure applications.
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Final Annealing and Stress Relief (最终退火与去应力):
Post-forming annealing in a reducing or vacuum atmosphere eliminates residual stresses from forming and welding, stabilizing the microstructure and ensuring long-term dimensional stability.
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Coiling and Winding (盘卷与绕制):
The formed tube is coiled onto a precision mandrel using CNC-controlled winding equipment to ensure uniform pitch, consistent coil diameter, and controlled springback. The coil is secured with stainless steel strapping and wrapped in protective film.
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Quality Inspection and Testing (质量检测与试验):
Every coil batch undergoes comprehensive testing including:
- Dimensional inspection (外径、壁厚、直线度)
- Hydrostatic pressure testing (水压试验)
- Non-destructive testing (NDT, 无损检测): Eddy current (涡流检测) or ultrasonic (超声波检测) for seam integrity
- Corrosion testing (腐蚀试验): Salt spray test per GB/T 10125
- Thermal performance benchmarking (热工性能基准测试) referencing JB/T 9066—1999 methodology
5. Applications
The stainless steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple industrial sectors, with its primary deployment in HVAC systems:
5.1 Primary Applications
- Cabinet Fan Coil Units (柜式风机盘管机组): The coil tube serves as the evaporator or condenser element, facilitating heat exchange between chilled water/hot water and the airstream. Thermal performance is validated per JB/T 9066—1999 testing protocols.
- Commercial HVAC Systems (商业暖通空调系统): Used in air handling units (AHUs, 空气处理机组), rooftop units (RTUs, 屋顶机组), and chiller coils for office buildings, hotels, hospitals, and retail facilities.
- Industrial Process Cooling/Heating (工业过程冷却/加热): Integration into process chillers, heat exchangers, and thermal management systems in chemical, pharmaceutical, and food processing industries.
5.2 Secondary Applications
- Refrigeration and Cryogenics (制冷与低温工程): Evaporator coils in walk-in coolers, blast freezers, and cryogenic equipment.
- Automotive and Marine HVAC (汽车与船舶暖通): Cabin air conditioning condensers and evaporators requiring corrosion-resistant tubing.
- Electronics Cooling (电子冷却): Heat exchanger coils for server room cooling, data center thermal management, and high-power electronics.
- Medical Equipment (医疗设备): Sterilization chambers, incubators, and laboratory temperature control systems requiring biocompatible, corrosion-resistant tubing.
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliances:
| Certification / Standard | Scope of Applicability |
|---|---|
| ISO 9001:2015 — Quality Management System | Overall manufacturing and quality assurance processes |
| ISO 14001:2015 — Environmental Management System | Environmental responsibility in production operations |
| ISO 45001:2018 — Occupational Health and Safety | Worker safety and occupational health management |
| JB/T 9066—1999 — Cabinet Fan Coil Units | Thermal performance testing methodology and compliance |
| GB/T 14976 — Stainless Steel Seamless Tubes | Material and dimensional specifications for seamless tube products |