Stainless Steel Seamless Coil Tube with Copper Alloy Cladding — Technical Specification

1. Product Overview

The Stainless Steel Seamless Coil Tube with Copper Alloy Cladding (hereinafter referred to as "Coil Tube") is a high-performance engineered piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product combines the corrosion resistance and mechanical strength of stainless steel with the thermal conductivity and electrical properties of copper alloy cladding, resulting in a versatile solution for demanding industrial applications. The coil tube is supplied in continuous coil form, enabling efficient downstream processing, cutting, and forming operations while minimizing material waste.

This product conforms to the current national and international standards governing copper alloy clad seamless coil tubes, including but not limited to GB/T standards for copper-clad steel tubes and relevant ASTM/EN specifications. The product is manufactured under a rigorous quality management system aligned with ISO 9001 principles, ensuring traceability, dimensional accuracy, and metallurgical integrity throughout the production cycle.

2. Material & Properties

2.1 Base Tube Material

The base tube is fabricated from austenitic or duplex stainless steel grades, selected for their superior resistance to general corrosion, pitting, and stress corrosion cracking. Common base grades include:

2.2 Cladding Material

The copper alloy cladding layer is applied to the inner or outer surface of the stainless steel base tube, providing enhanced thermal conductivity, electrical performance, and additional corrosion protection. Typical cladding materials include:

2.3 Mechanical Properties

Property Specification / Typical Value
Tensile Strength (Ultimate Tensile Strength, UTS) ≥ 520 MPa (base tube); ≥ 220 MPa (clad layer)
Yield Strength (0.2% Offset) ≥ 205 MPa (base tube)
Elongation at Break ≥ 35% (base tube); ≥ 30% (clad layer)
Thermal Conductivity 14.9 W/(m·K) (SS 304); 390 W/(m·K) (Cu); 9.0 W/(m·K) (Cu-Ni 90/10)
Operating Temperature Range −196 °C to +600 °C (stainless steel base); up to +260 °C (copper alloy clad)
Adhesion Strength (Bond Strength) ≥ 95% metallurgical bond; no delamination under standard peel testing

3. Specifications

Parameter Range / Options Notes
Outer Diameter (OD) Φ6.0 mm – Φ114.3 mm (1/4" – 4") Custom diameters available upon request
Wall Thickness (WT) 0.5 mm – 6.0 mm Tolerance: ±0.1 mm or ±10% (whichever is greater)
Clad Layer Thickness 0.05 mm – 1.5 mm Single-sided or double-sided cladding available
Coil Length 15 m – 200 m per coil Continuous lengths available for automated processing
Coil Weight 50 kg – 2,000 kg per coil Dependent on OD, WT, and coil length
Surface Finish No. 1 (Hot Rolled), 2B, BA, Pickled & Polished, Custom Surface roughness Ra ≤ 0.8 μm for polished finishes
Heat Treatment Condition Annealed (Soft), Solution Treated, Cold Worked (1/4 Hard, 1/2 Hard, Full Hard) Delivered condition per customer specification
End Form Plain, Beveled, Threaded, Flanged, Custom Post-coiling processing available
Applicable Standards GB/T 14976, GB/T 17893, ASTM A213, EN 10216-5, JIS G3459 Multi-standard compliance for global applications

4. Manufacturing Process

The production of the Stainless Steel Seamless Coil Tube with Copper Alloy Cladding involves a precisely controlled multi-stage process designed to ensure metallurgical integrity, dimensional accuracy, and consistent performance. The key manufacturing stages are outlined below:

  1. Raw Material Selection & Incoming Inspection

    Stainless steel round bars and copper alloy strips are procured from certified suppliers. Incoming materials undergo chemical composition analysis (via Optical Emission Spectrometry, OES), mechanical property verification, and visual inspection to ensure conformance to the specified grade requirements.

  2. Piercing & Seamless Tube Formation

    The stainless steel billets are heated to the appropriate forging temperature and pierced to form seamless hollow tubes. The piercing process eliminates the weld seam found in welded alternatives, ensuring uniform material properties in all directions and superior pressure containment capability.

  3. Pilger Rolling & Reduction

    The pierced tube undergoes pilger rolling to achieve the target outer diameter and wall thickness. This process provides high dimensional accuracy (typically within ±0.1 mm tolerance) and a smooth surface finish.

  4. Heat Treatment (Annealing & Solution Treatment)

    The formed tube is subjected to controlled annealing in a protective atmosphere furnace to relieve internal stresses, refine grain structure, and achieve the desired mechanical properties. For stainless steel grades, solution treatment at 1050–1150 °C followed by controlled cooling is performed to ensure full austenitization and maximum corrosion resistance.

  5. Copper Alloy Cladding (Bonding)

    The copper alloy cladding layer is applied to the stainless steel tube through one of the following methods:

    • Roll Bonding (Calender Cladding) — The copper strip and steel tube are heated to the bonding temperature and rolled through precision calender rolls under controlled pressure to achieve a metallurgical bond.
    • Explosion Bonding — For thicker cladding layers, explosion bonding is employed to create a strong, diffusion-free interface between dissimilar metals.
    • Electroplating / Electroless Plating — For thinner cladding layers (<0.1 mm), electrochemical deposition methods are utilized.
  6. Final Dimensional Reduction & Sizing

    The clad tube undergoes final sizing through cold drawing or cold rolling to achieve the precise final dimensions. This step also work-hardens the material to the specified temper condition if required.

  7. Coiling & Winding

    The finished tube is wound into coils of the specified length and diameter using automated coiling equipment. Coils are secured with banding straps and protected with moisture-barrier wrapping to prevent surface degradation during storage and transportation.

  8. Quality Control & Testing

    Comprehensive quality assurance is performed at multiple stages, including:

    • Chemical composition verification (OES / ICP-OES)
    • Mechanical testing (tensile, hardness, impact)
    • Dimensional inspection (OD, WT, roundness, straightness)
    • Non-Destructive Testing (NDT): Eddy current testing, ultrasonic testing, and dye penetrant inspection
    • Clad bond integrity testing (peel test, adhesion verification)
    • Corrosion testing (salt spray, pitting potential, electrochemical impedance spectroscopy)

5. Applications

The Stainless Steel Seamless Coil Tube with Copper Alloy Cladding finds extensive application across multiple high-value industrial sectors, where the combination of stainless steel durability and copper alloy functionality provides a decisive performance advantage:

5.1 Heat Exchanger & Condenser Manufacturing

The superior thermal conductivity of the copper alloy cladding, combined with the corrosion resistance of the stainless steel base, makes this product ideal for manufacturing heat exchanger tubes, condenser coils, and evaporator assemblies in HVAC (Heating, Ventilation, and Air Conditioning) systems, refrigeration equipment, and industrial process heat transfer applications.

5.2 Marine & Offshore Engineering

Copper-nickel clad variants offer exceptional resistance to marine biofouling, seawater corrosion, and erosion-corrosion, making them suitable for seawater piping systems, ballast water systems, and heat exchangers on offshore platforms, naval vessels, and desalination plants.

5.3 Chemical & Petrochemical Processing

In aggressive chemical environments involving acids, alkalis, and halide-containing solutions, the stainless steel base provides structural integrity while the copper alloy cladding offers additional corrosion protection and enhanced heat transfer performance in process vessels, reactors, and heat recovery units.

5.4 Electrical & Electronic Applications

The electrical conductivity of the copper cladding enables use in grounding systems, electromagnetic shielding conduits, and specialized electrical enclosures where both mechanical strength and electrical performance are required.

5.5 Nuclear & Energy Applications

In nuclear power plants and renewable energy systems, the product is used for feedwater piping, condensate extraction systems, and heat transfer components where reliability, corrosion resistance, and thermal efficiency are critical.

5.6 Food & Pharmaceutical Processing

Sanitary-grade variants with polished inner surfaces meet FDA and 3-A sanitary standards, making them suitable for dairy processing, beverage production, pharmaceutical manufacturing, and biotechnology applications where hygiene and corrosion resistance are paramount.

6. Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that every coil tube product meets international standards and customer requirements. The following certifications and compliance frameworks are maintained:

Certification / Standard Description
ISO 9001:2015 Quality Management System certification covering design, manufacturing, and service
ISO 14001:2015 Environmental Management System certification
ISO 45001:2018 Occupational Health and Safety Management System
CE Marking Conformity to European Union health, safety, and environmental protection standards
EN 10204 3.1 Inspection Certificate for material verification and traceability
NACE MR0175 / ISO 15156 Resistance to sulfide stress cracking for oil and gas applications
API 5L / API 5CT Compliance with American Petroleum Institute standards (where applicable)
GB/T National Standards Full compliance with Chinese national standards for seamless steel tubes and copper alloy products

7. Unique Selling Points

Note: All specifications listed herein are provided as typical values. Actual product dimensions