Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered continuous-length tubular product supplied in a coiled configuration. Unlike seamless or welded straight-length tubes, coil tubes are produced in long, uninterrupted lengths that are wound into coils for efficient storage, transportation, and downstream processing. This product is specifically designed for high-performance applications in HVAC (Heating, Ventilation, and Air Conditioning), heat exchangers, refrigeration systems, and industrial fluid transport systems where corrosion resistance, thermal efficiency, and mechanical integrity are paramount.
The coil tube product line encompasses a wide range of stainless steel grades, with primary emphasis on austenitic stainless steels including SUS304 (UNS S30400), SUS316L (UNS S31603), and SUS321 (UNS S32100), selected based on the end-use application's environmental and mechanical demands. The coiled format offers significant material utilization advantages over straight-length tubes, reducing cutting waste by up to 30% in production environments that require custom-length segments.
Key Advantage: The continuous coil format enables seamless integration into automated tube-processing lines, significantly reducing production cycle times and material waste while ensuring consistent dimensional accuracy along the entire coil length.
2. Material & Properties
2.1 Available Grades and Compositional Requirements
Wenzhou Jixing Metal Materials Co., Ltd. supplies coil tubes in the following primary stainless steel grades, each conforming to international standards:
| Grade (Chinese / International) | UNS Designation | Carbon (C) Max % | Chromium (Cr) % | Nickel (Ni) % | Molybdenum (Mo) % | Key Characteristics |
|---|---|---|---|---|---|---|
| SUS304 / 304 | UNS S30400 | 0.08 | 18.0–20.0 | 8.0–10.5 | — | Excellent general corrosion resistance; good formability; non-magnetic |
| SUS316L / 316L | UNS S31603 | 0.03 | 16.5–18.5 | 10.0–14.0 | 2.0–3.0 | Superior pitting and crevice corrosion resistance; low carbon for welding applications |
| SUS321 / 321 | UNS S32100 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | Titanium-stabilized; excellent resistance to intergranular corrosion at elevated temperatures (450–850°C) |
| SUS304L / 304L | UNS S30403 | 0.03 | 18.0–20.0 | 8.0–10.5 | — | Low carbon variant of 304; enhanced weldability and post-weld corrosion resistance |
2.2 Mechanical Properties
| Property | SUS304 (Annealed) | SUS316L (Annealed) | SUS321 (Annealed) |
|---|---|---|---|
| Tensile Strength (抗拉强度), MPa | ≥ 520 | ≥ 485 | ≥ 515 |
| Yield Strength (屈服强度), MPa | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (伸长率), % | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (密度), g/cm³ | 7.93 | 8.00 | 7.93 |
| Thermal Conductivity (热导率), W/(m·K) at 100°C | 16.3 | 16.3 | 16.3 |
| Magnetic Permeability (磁导率) | Non-magnetic (μr ≈ 1.002–1.005) | Non-magnetic | Non-magnetic |
2.3 Surface Finish Options
- 2B Finish (No. 2B Surface): Cold-rolled and annealed with a light pass-rolled surface; smooth, matte appearance; suitable for general industrial applications.
- Ba Finish (Bright Annealed): Annealed in a protective atmosphere to retain a bright, reflective surface without scaling; ideal for decorative and food-grade applications.
- No. 4 Brushed Finish: Directional grinding finish with uniform grain pattern; provides aesthetic appeal while maintaining corrosion resistance.
- Mirror Polish (8K): Electrolytic polishing to achieve a high-gloss, reflective surface (Ra ≤ 0.2 μm); used in pharmaceutical and cosmetic equipment.
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification Range | Applicable Standard |
|---|---|---|
| Outer Diameter (OD, 外径) | 6.0 mm – 108.0 mm (¼" – 4") | ASTM A554 / GB/T 14976 |
| Wall Thickness (壁厚) | 0.5 mm – 8.0 mm | ASTM A554 / GB/T 14976 |
| OD Tolerance | ± 0.15 mm (for OD ≤ 25 mm); ± 0.5% (for OD > 25 mm) | ASTM A554 |
| Wall Thickness Tolerance | ± 10% of nominal wall thickness | ASTM A554 |
| Coil Weight (盘重) | 300 kg – 2,000 kg per coil | Manufacturer Specification |
| Coil Inner Diameter (盘内径) | 150 mm – 500 mm (customizable) | Manufacturer Specification |
| Single Coil Length (单盘长度) | 20 m – 300 m (continuous) | — |
3.2 Applicable Standards
- ASTM A554 / A554M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipes for Chemical and Similar Severe Service
- ASTM A213: Standard Specification for Seamless Austenitic Chromium-Chromium-Nickel Steel Tubing for Heat-Exchanger and Heat-Sink Tubing
- GB/T 14976: Chinese National Standard — Seamless Stainless Steel Tubes for Fluid Transport
- JIS G3459: Japanese Industrial Standard — Cold-Drawn Stainless Steel Tubes for General Use
- EN 10216-5: European Standard — Non-ferrous Metallic Tubes and Their Fittings — Technical Delivery Conditions — Part 5: Ferritic and Austenitic Stainless Steel Tubes
- ASME B36.19M: Welded and Seamless Wrought Stainless Steel Pipe
4. Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous, multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
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Raw Material Preparation (原材料准备):
- Stainless steel slabs or billets are procured from certified mills (e.g., POSCO, Outokumpu, Taigang, Baosteel) with full chemical composition and heat-number traceability.
- Incoming materials undergo spectroscopic analysis to verify compliance with specified grade requirements.
-
Hot Rolling & Annealing (热轧与退火):
- Slabs are heated to 1,150–1,250°C and hot-rolled into tube blanks with the target outer diameter and wall thickness.
- Hot-rolled tubes undergo solution annealing (固溶退火) at 1,050–1,150°C followed by rapid water quenching to achieve a fully austenitic microstructure with dissolved carbides.
-
Pickling & Descaling (酸洗与除鳞):
- Hot-rolled scales and oxides are removed through a mixed acid pickling process (nitric acid + hydrofluoric acid) or electrochemical pickling to restore the passive chromium oxide layer.
- Post-pickling inspection ensures complete oxide removal and surface passivation.
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Cold Drawing / Cold Reduction (冷拔/冷轧):
- Tubes are cold-drawn through precision tungsten carbide dies or cold-rolled between grooved rolls to achieve final dimensions within tight tolerances.
- Multiple drawing passes may be employed for thicker-wall tubes, with intermediate annealing to prevent work hardening.
- Reduction ratio per pass is typically controlled at 15–25% to maintain dimensional accuracy.
-
Pilot Drawing (芯棒拉拔):
- For seamless tubes, a hardened steel or tungsten carbide pilot is drawn through the tube interior to maintain wall thickness uniformity and inner diameter consistency.
- Pilot-to-tube size ratio is optimized to minimize residual stress and ensure concentricity.
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Coiling (盘管):
- Finished tubes are wound onto precision coiling mandrels using hydraulic or mechanical coil winding systems.
- Coiling tension is carefully controlled to prevent tube deformation, kinking, or ovality.
- Coil ends are secured with banding straps and labeled with product identification information.
-
Final Annealing (最终退火):
- Coiled tubes may undergo a final stress-relief anneal at 800–900°C to eliminate residual stresses introduced during coiling.
- For bright annealed products, annealing is performed in a hydrogen or vacuum atmosphere to prevent surface oxidation.
-
Quality Inspection & Testing (质量检验与测试):
- Dimensional verification using calipers, micrometers, and ultrasonic thickness gauges.
- Hydrostatic testing (水压试验) at 2.5× working pressure to verify weld integrity (for welded tubes) and structural soundness.
- Surface inspection for defects such as cracks, pitting, inclusions, and scratches.
- Chemical analysis and mechanical testing on sample coupons per lot.
- Intergranular corrosion testing (晶间腐蚀试验) per ASTM A262 Practice E for 304L and 316L grades.
5. Applications
5.1 HVAC & Fan Coil Units (风机盘管系统)
Stainless steel coil tubes are extensively used in fan coil units (FCUs, 风机盘管机组), which are terminal units in central air-conditioning systems. The coil tube serves as the heat transfer element within the air handler, facilitating heat exchange between the circulating refrigerant (or hot water) and the ambient air. Key performance evaluation criteria for fan coil units include:
- Cooling Capacity (制冷量): Measured in kW or BTU/hr; directly influenced by tube material thermal conductivity and coil geometry (tube count, fin density, tube pitch).
- Heating Capacity (制热量): Evaluated at rated flow rate and inlet/outlet temperature differential.
- Airflow Rate (风量): Typically 200–2,500 m³/hr depending on unit size; must be maintained without excessive pressure drop across the coil.
- Pressure Drop (压降): Both air-side and water-side pressure drops must be minimized to ensure efficient fan operation and pump energy consumption.
- Coil Efficiency (盘管效率): Defined as the ratio of actual heat transfer to the theoretical maximum; stainless steel tubes contribute to high efficiency due to their consistent wall thickness and thermal properties.
5.2 Additional Application Domains
- Refrigeration & Heat Exchangers (制冷与热交换器): Condenser tubes, evaporator tubes, and chiller coils in industrial and commercial refrigeration systems.
- Food & Beverage Processing (食品加工): Sanitary-grade coil tubes (304L, 316L) for milk processing, beer brewing, and pharmaceutical equipment where hygienic standards (FDA, 3-A) are required.
- Chemical & Petrochemical Industry (化工与石化): Corrosion-resistant tubing for chemical reactors, distillation columns, and process piping systems handling aggressive media.
- Automotive Industry (汽车工业): Exhaust system components, fuel lines, and heat exchangers where high-temperature resistance and corrosion resistance are critical.
- Construction & Architecture (建筑与装饰): Decorative handrails, structural supports, and architectural features requiring both aesthetic appeal and weather resistance.
- Medical & Pharmaceutical (医疗与制药): Equipment tubing requiring autoclave sterilization compatibility and non-reactivity with pharmaceutical products.
- Marine & Offshore (海洋与海上): Seawater-resistant tubing for desalination plants, ballast water systems, and offshore platform piping (316L grade preferred).
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and compliance standards:
| Certification / Standard | Description | Scope |
|---|---|---|
| ISO 9001:2015 | Quality Management |