Stainless Steel Coil Tube — Air Conditioning Coil Tube Blank (Coiltube)
Product Code: 1434 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube is a precision-engineered coiled tubular product specifically designed for use in air conditioning and refrigeration heat exchanger systems. This product represents a critical intermediate component — the tube blank (Tube Billet) — from which finished air conditioning coil tubes are subsequently manufactured. The coil tube is produced in continuous helical form, enabling downstream processing operations including cutting, bending, finning, and brazing with minimal material waste and maximum dimensional consistency.
Unlike straight-length tubing, the coil tube format offers significant logistical and manufacturing advantages: it reduces cutting loss, maintains uniform mechanical properties along the entire length, and facilitates high-speed continuous processing on automated coil tube manufacturing lines. This product is manufactured in accordance with international standards for stainless steel seamless and welded tubing used in thermal exchange applications.
Material & Properties
Base Alloy Compositions
Wenzhou Jixing Metal Materials Co., Ltd. offers coil tubes in the following primary stainless steel grades suitable for air conditioning applications:
- SAE 304 / UNS S30400 — Austenitic stainless steel with excellent general corrosion resistance and formability
- SAE 316 / UNS S31600 — Austenitic stainless steel with enhanced resistance to chlorides and pitting corrosion
- SAE 321 / UNS S32100 — Stabilized austenitic grade with titanium stabilization for elevated temperature service
- SAE 304L / UNS S30403 — Low-carbon variant optimized for post-welding corrosion resistance
Mechanical Properties (Typical Values for Annealed Condition)
| Property | SAE 304 | SAE 316 | SAE 321 |
|---|---|---|---|
| Tensile Strength (UTS) — MPa | ≥ 515 | ≥ 515 | ≥ 515 |
| Yield Strength (0.2% Offset) — MPa | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (at Break) — % | ≥ 40 | ≥ 40 | ≥ 40 |
| Density — g/cm³ | 7.93 | 8.00 | 7.99 |
| Thermal Conductivity (20°C) — W/(m·K) | 16.3 | 14.6 | 16.3 |
| Thermal Expansion Coefficient (20–100°C) — ×10⁻⁶/K | 17.3 | 16.0 | 17.3 |
| Maximum Service Temperature — °C | 870 | 870 | 900 |
Chemical Composition Requirements (ASTM A270 / ASTM A554)
| Grade | C (max) | Cr | Ni | Mo | Si (max) | Mn (max) | P (max) | S (max) |
|---|---|---|---|---|---|---|---|---|
| 304 | 0.08 | 18.0–20.0 | 8.0–10.5 | — | 0.75 | 2.00 | 0.045 | 0.030 |
| 316 | 0.08 | 16.0–18.5 | 10.0–14.0 | 2.0–3.0 | 0.75 | 2.00 | 0.045 | 0.030 |
| 321 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | 0.75 | 2.00 | 0.045 | 0.030 |
Specifications
Dimensional Specifications
| Parameter | Specification Range | Tolerance |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 25.0 mm | ±0.05 mm (OD ≤ 10 mm); ±0.10 mm (OD > 10 mm) |
| Wall Thickness (WT) | 0.30 mm – 1.50 mm | ±0.03 mm |
| Coil Length | 100 m – 2,000 m (continuous) | As ordered |
| Coil Inner Diameter (ID) | 200 mm – 500 mm | ±5 mm |
| Coil Outer Diameter (OD) | 600 mm – 1,200 mm | ±10 mm |
| Surface Finish | Bright Annealed (BA) / Pickled & Bright | Ra ≤ 0.4 μm |
| End Condition | Plain / Beveled / Flared (on request) | Per customer drawing |
Available Standards
- ASTM A270 / A270M — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service
- ASTM A554 / A554M — Standard Specification for Heat Exchanger and Condenser Tubes of Nonferrous Alloys and Stainless Steels
- GB/T 14976 — Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport
- JIS G3459 — Japanese Industrial Standard for Stainless Steel Tubes for Heat Exchangers
- EN 10217-7 — European Standard for Seamless Stainless Steel Tubes for Particular Service
Manufacturing Process
The production of high-quality air conditioning coil tube blanks involves a rigorous, multi-stage metallurgical and mechanical processing sequence. The following process flowchart summarizes the key stages:
Process Flow
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Raw Material Selection (管坯制备 — Tube Blank Preparation)
High-purity stainless steel ingots or continuous casting billets are selected based on strict chemical composition requirements. Each batch undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify alloying element content within specification limits.
-
Hot Rolling / Hot Extrusion (热轧/热挤压)
Billets are heated to 1150–1250°C and subjected to hot rolling or hot extrusion to form seamless tube blanks (Tube Blanks / 管坯). This stage establishes the initial tube geometry and refines the microstructure through controlled deformation.
-
Piercing & Elongation (穿孔与拉拔)
The hot-formed blanks are pierced to create hollow sections, followed by progressive cold drawing (拉拔) through a series of dies to achieve precise final OD and wall thickness dimensions. Drawing ratios are carefully controlled to maintain dimensional accuracy.
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Intermediate Annealing (中间退火)
When cumulative cold work exceeds the material's strain-hardening capacity, intermediate annealing at 1050–1100°C is performed to restore ductility and eliminate residual stresses, ensuring uniform mechanical properties throughout the coil length.
-
Acid Pickling & Bright Annealing (酸洗与光亮退火)
The tube coil is subjected to continuous bright annealing in a protective atmosphere (Hydrogen + Nitrogen) at 1050–1150°C, followed immediately by controlled cooling. This eliminates decarburization, restores full solution-treated condition, and produces a clean, oxide-free surface suitable for brazing operations.
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Precision Sizing & Straightening (精整与矫直)
Final sizing passes through roller or die sizing equipment to ensure dimensional conformity. The coil is then straightened and wound onto a precision coil winder with controlled tension to prevent deformation during storage and transport.
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Quality Inspection & Testing (质量检测)
Each coil undergoes comprehensive inspection including dimensional measurement, hydrostatic pressure testing, chemical analysis verification, and surface quality assessment.
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Packaging & Dispatch (包装与发货)
Finished coils are wrapped in protective film, secured with steel strapping, and packaged for transport to prevent surface damage and corrosion during transit.
Key Process Parameters
| Process Stage | Temperature Range | Atmosphere | Key Control Parameter |
|---|---|---|---|
| Hot Rolling | 1150 – 1250 °C | Air | Rolling temperature, reduction ratio |
| Cold Drawing | Room temperature | — | Drawing ratio (≤ 30% per pass) |
| Intermediate Annealing | 1050 – 1100 °C | Protective (N₂/Ar) | Soak time, cooling rate |
| Bright Annealing | 1050 – 1150 °C | 5% H₂ + 95% N₂ | Dew point (≤ -40°C), O₂ content (< 10 ppm) |
| Pickling | 60 – 80 °C | HNO₃ + H₂O | Acid concentration, immersion time |
Applications
The stainless steel coil tube is a fundamental component in a wide range of thermal management and fluid transport systems. Primary application domains include:
- Air Conditioning Heat Exchangers (空调换热器) — Evaporator and condenser tubes in residential and commercial HVAC (Heating, Ventilation, and Air Conditioning) systems. The coil format enables efficient continuous processing into serpentine or U-bend configurations.
- Refrigeration Systems — Capillary tubes, expansion tubes, and evaporator coils in domestic and industrial refrigeration equipment.
- Automotive Air Conditioning — Tubes for vehicle HVAC evaporators and condensers, where lightweight and corrosion-resistant materials are critical.
- Heat Pumps (热泵) — Indoor and outdoor unit heat exchanger tubes in residential and commercial heat pump systems.
- Food Processing Equipment — Hygienic heat exchangers and piping systems in food and beverage manufacturing, leveraging the sanitary properties of stainless steel.
- Industrial Process Cooling — Shell-and-tube heat exchangers, plate-fin coils, and fluid distribution manifolds in chemical and petrochemical plants.
- Water Heaters & Boilers — Heat transfer tubes in domestic water heating appliances and industrial boiler systems.
- Medical Equipment — Precision tubing for medical device heat exchange components where biocompatibility and corrosion resistance are paramount.
Quality Certifications & Testing
Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO/TS 22163 — IATF Automotive Quality Management (for automotive-grade applications)
- NADCAP — National Aerospace and Defense Contractors Accreditation Program (for aerospace-qualified processes)
- Mill Test Reports (MTR) — Provided with every shipment, documenting chemical composition, mechanical properties, and heat treatment history