Stainless Steel Coil Tube (盘管) for Refrigeration Condenser Applications
Product Code: No. 1590 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Classification: Technical Literature & Learning Reference
1. Product Overview
The Stainless Steel Coil Tube (盘管Coiltube) is a precision-engineered tubular product designed primarily for coil-wound condenser assemblies in refrigeration systems, particularly household and commercial refrigerators. This product is manufactured in continuous coil form to facilitate seamless winding processes, enabling the formation of compact, high-efficiency heat exchange surfaces. The coil tube is supplied in continuous lengths wound onto spools, allowing downstream fabricators to uncoil and form condenser circuits with minimal material loss and maximum process continuity.
As a specialized refrigeration-grade stainless steel tubing product, the Coil Tube is engineered to withstand the thermal cycling, mechanical vibration, and chemical exposure inherent in refrigerant condensation environments. The product represents a critical component in the thermal management architecture of modern refrigeration appliances, where it serves as the primary medium for rejecting heat from the refrigerant circuit to the ambient environment.
Key Reference: Technical learning and application insights derived from the study of "Welding of Refrigerator Steel Wire Coil Condensers" (《电冰箱钢丝盘管式冷凝器的焊接》), covering advanced manufacturing and assembly techniques for coil-type condenser systems.
2. Material & Properties
2.1 Base Material
The Coil Tube is fabricated from high-grade austenitic stainless steel wire, conforming to internationally recognized standards for corrosion-resistant tubing. The primary material grades utilized include:
- AISI 304 (UNS S30408): General-purpose austenitic stainless steel with excellent corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- AISI 316 (UNS S31603): Enhanced corrosion resistance grade with 2–3% Molybdenum (Mo) addition, suitable for more aggressive environmental conditions.
- AISI 430 (UNS S43000): Ferritic stainless steel grade offering good heat resistance and cost efficiency for specific condenser applications.
2.2 Mechanical Properties
| Property | Specification / Typical Value | Test Standard |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa (AISI 304 annealed) | ASTM A269 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ASTM A269 |
| Elongation (延伸率) | ≥ 40% | ASTM A269 |
| Hardness (硬度) | ≤ 130 HRB (annealed condition) | ASTM A269 |
| Thermal Conductivity (热导率) | ~16.3 W/(m·K) at 20°C | ASTM A269 |
| Corrosion Resistance (耐腐蚀性) | PASS — 96h Salt Spray (ASTM B117) | ASTM B117 |
2.3 Chemical Composition
| Element | AISI 304 (%) | AISI 316 (%) |
|---|---|---|
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 10.0 – 14.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 |
| Carbon (C) | ≤ 0.08 | ≤ 0.08 |
| Iron (Fe) | Balance | Balance |
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 8.0 mm (customizable) |
| Wall Thickness | 0.3 mm – 1.2 mm |
| Coil Length per Spool | 500 m – 5,000 m (adjustable) |
| Coil Winding Tolerance | ± 1.0% |
| Surface Finish | Mill finish / Bright annealed / Passivated |
| Pressure Rating | Up to 2.5 MPa (depending on wall thickness) |
| Operating Temperature Range | −196°C to +450°C |
| Weldability | Excellent — TIG (GTAW), resistance, and laser welding compatible |
| Formability | High — suitable for cold bending, winding, and shaping |
| Delivery Condition | Annealed (soft) on spool coil |
| Applicable Standards | GB/T 12771, ASTM A269/A270, EN 10217-7, JIS G3447 |
4. Manufacturing Process
4.1 Wire Drawing & Annealing
The manufacturing process begins with high-purity stainless steel wire rod sourced from certified mills. The wire rod undergoes multi-pass cold drawing through precision tungsten carbide dies to achieve the target outer diameter and wall thickness tolerances. Periodic intermediate annealing (bright annealing in a controlled hydrogen or nitrogen atmosphere) is performed to restore ductility, prevent work hardening, and maintain dimensional accuracy throughout the drawing process.
4.2 Seamless Tube Forming
The drawn wire is processed through a precision seamless tube forming system. Two primary methods are employed:
- Capillary Drawing: The wire is pierced and drawn through a capillary die to form a seamless tube with precise internal and external dimensional control. This method produces tubes with uniform wall thickness and smooth internal surfaces.
- Welded Tube Forming: The wire is slit, formed into a tubular shape, and seam-welded using high-frequency induction welding (HFW) or laser welding technology. The weld seam is subsequently ground and polished to achieve a continuous, leak-free tube.
4.3 Bright Annealing & Passivation
Finished tubes undergo bright annealing in a continuous annealing furnace (CAF) operating under a controlled reducing atmosphere (H₂/N₂ mix). This process eliminates residual stresses from cold working, restores full austenitic microstructure, and produces a clean, oxide-free surface finish. Following annealing, a passivation treatment is applied to enhance the passive chromium oxide layer, improving corrosion resistance.
4.4 Coil Winding
The processed tube is wound onto precision spools in continuous coil form using automated coiling equipment. The winding process maintains consistent tension to prevent kinking, distortion, or mechanical damage to the tube. Each coil is inspected for dimensional accuracy, surface integrity, and mechanical properties before packaging.
4.5 Condenser Assembly — Coil Winding & Welding
In downstream condenser manufacturing, the coil tube is uncoiled and wound into a serpentine or spiral pattern around a mandrel to form the condenser coil geometry. The key welding processes include:
- Resistance Spot Welding (电阻点焊): Used to join the coil tube to the header pipes (inlet/outlet manifolds), creating secure, leak-tight electrical connections that also serve as thermal bridges for efficient heat transfer.
- TIG Welding (GTAW): Employed for precision butt joints and connection welds where higher quality and visual inspection are required.
- Ultrasonic Welding: An emerging technique for joining coil tubes without filler material, offering high-speed, low-deformation connections.
The welding parameters — including welding current, electrode force, welding time, and inter-electrode distance — are critically controlled to ensure consistent weld nugget size, minimal heat-affected zone (HAZ) distortion, and complete fusion without burn-through or cold welding defects.
5. Applications
5.1 Primary Applications
- Household Refrigerators: Coil-type condensers for single-door, double-door, side-by-side, and multi-door refrigerator designs. The coil tube forms the heat rejection circuit, dissipating heat from the refrigerant to the ambient air.
- Commercial Refrigeration: Display cases, reach-in freezers, walk-in coolers, and ice-making machines where compact, high-efficiency condenser coils are required.
- Air Conditioning Systems: Indoor unit condensers and evaporators in split-type and window air conditioners.
5.2 Secondary Applications
- Heat Exchangers: Compact heat exchange coils in industrial process cooling systems.
- Automotive Thermal Management: Condenser coils and evaporator tubes in vehicle air conditioning systems.
- Food Processing Equipment: Sanitary-grade heat exchange coils in dairy, beverage, and pharmaceutical processing lines.
- Medical Equipment: Precision tubing for temperature-controlled medical devices and laboratory instruments.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity with international standards:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes |
| ASTM A269 / A270 | American Standard for Welded/Automatic Stainless Steel Tubing |
| EN 10217-7 | European Standard for Heat-Exchanger and Boiler Tubes |
| JIS G3447 | Japanese Industrial Standard for Stainless Steel Seamless Tubes |
| RoHS Compliance | Restriction of Hazardous Substances |
| REACH Compliance | Registration, Evaluation, Authorisation and Restriction of Chemicals |
6.1 Quality Control Measures
- Incoming Inspection: Raw wire rod verified for chemical composition (spectroscopic analysis), mechanical properties, and dimensional accuracy.
- In-Process Monitoring: Continuous measurement of tube OD, wall thickness, and coil tension during production. Automated visual inspection systems detect surface defects.
- Final Testing: Hydrostatic pressure testing (leak testing), dimensional verification, surface roughness measurement, and corrosion resistance testing.
- Weld Quality Assurance: Non-destructive testing (NDT) including dye penetrant inspection (DPI) and eddy current testing for weld integrity verification.
7. Unique Selling Points
- Continuous Coil Delivery: Supplied in uninterrupted coil form on spools, enabling seamless downstream winding and condenser fabrication with minimal material waste and maximum production efficiency.
- Superior Weldability: Material chemistry and annealing condition are optimized for resistance spot welding and TIG welding, ensuring reliable, leak-free condenser joints with minimal HAZ distortion.
- Precision Dimensional Control: Tight tolerances on OD, wall thickness, and coil winding ensure consistent condenser geometry and predictable thermal performance.
- Corrosion Resistance: Austenitic stainless steel composition provides long-term resistance to refrigerant exposure, condensation, and humid operating environments, extending condenser service life significantly over carbon steel alternatives.
- Thermal Efficiency: Smooth internal surface finish minimizes flow resistance, improving refrigerant heat transfer efficiency and reducing compressor power consumption.
- Customization Capability: Flexible manufacturing platform supports custom OD, wall thickness, coil length, and material grade configurations tailored to specific condenser design requirements.
- Technical Knowledge Base: Deep expertise in coil condenser welding technology, derived from systematic study of industry-standard welding methodologies, ensures reliable product performance and application guidance.
8. Packaging & Delivery
Each coil tube spool is wrapped in protective plastic film to prevent surface scratches and contamination during transit. Spools are secured on wooden pallets with steel strapping and moisture-absorbent desiccant packs. Shipping documentation includes material test certificates (MTC), dimensional inspection reports, and compliance declarations per applicable standards.
9. Technical Notes
For optimal condenser performance, it is recommended that the coil tube be wound at a minimum bend radius of 5× the outer diameter to prevent kinking or wall thinning. When performing resistance spot welding for condenser assembly, electrode tips should be periodically dressed to maintain consistent contact resistance and weld nugget geometry. Post-welding, a visual and pressure leak test should be conducted on 100% of joints to ensure