CuNi 70/30 (C71500) Copper-Nickel Alloy Coil Tube
Wenzhou Jixing Metal Materials Co., Ltd. presents its premium-grade CuNi 70/30 (ASTM B151 / UNS C71500) copper-nickel alloy coil tube, engineered for the most demanding marine and offshore environments. This advanced alloy, composed of approximately 70% copper and 30% nickel with carefully controlled trace additions of iron, manganese, and zinc, delivers superior corrosion resistance, mechanical strength, and long-term service life in aggressive seawater conditions where conventional materials fail.
Product Overview
The CuNi 70/30 coil tube represents the gold standard in heat exchanger and seawater handling tubing for offshore platforms, naval vessels, and industrial marine applications. Unlike the more commonly specified CuNi 90/10 alloy, the 70/30 composition provides significantly enhanced resistance to pitting, crevice corrosion, and erosion-corrosion—particularly under high-velocity flow conditions where differential aeration and cavitation stresses are prevalent. The coil configuration allows for compact heat exchanger coil installations, maximizing thermal transfer surface area within confined spatial footprints.
Material & Properties
The CuNi 70/30 (C71500) alloy is distinguished by its exceptional combination of corrosion resistance, mechanical properties, and fabricability. The higher nickel content compared to CuNi 90/10 provides a more robust passive film and superior resistance to dezincification, making it the preferred choice for high-flow-rate seawater cooling circuits, offshore oil and gas production facilities, and desalination plants.
- Superior Corrosion Resistance: Significantly higher resistance to pitting and crevice corrosion than CuNi 90/10, with a corrosion rate in seawater of less than 0.01 mm/year under normal flow conditions
- Enhanced Mechanical Strength: Tensile strength of 410–550 MPa and yield strength exceeding 200 MPA in annealed condition, providing structural integrity under thermal cycling and mechanical vibration
- Resistance to Erosion-Corrosion: Capable of withstanding seawater velocities up to 5.0 m/s without significant degradation
- Anti-Fouling Characteristics: The alloy's surface chemistry inhibits biological fouling and marine organism attachment, reducing maintenance intervals
- Excellent Thermal Conductivity: Approximately 25–30 W/(m·K), ensuring efficient heat transfer performance
- Non-Magnetic Properties: Suitable for applications requiring non-magnetic materials
Specifications
| Parameter | Specification |
|---|---|
| Alloy Designation | CuNi 70/30 — ASTM B151 / UNS C71500 / EN 1.2185 |
| Chemical Composition (wt%) | Cu: 69.0–71.0 | Ni: 28.0–34.0 | Fe: 0.5–2.0 | Mn: 0.5–1.5 | Zn: ≤0.5 | Pb: ≤0.05 | S: ≤0.03 |
| Outer Diameter | 6.0 – 50.8 mm (1/4" – 2") — custom sizes available |
| Wall Thickness | 0.50 – 3.00 mm — tailored to pressure rating requirements |
| Coil Diameter | Standard coil ID: 1.0 – 3.0 m — custom coil configurations available |
| Tensile Strength (annealed) | 410 – 550 MPa (60 – 80 ksi) |
| Yield Strength (0.2% offset) | ≥ 200 MPa (≥ 29 ksi) |
| Elongation | ≥ 30% |
| Hardness (annealed) | ≤ 110 HV |
| Corrosion Rate (seawater, 1.5 m/s) | < 0.01 mm/year |
| Maximum Flow Velocity | 5.0 m/s (20 ft/s) — continuous service |
| Operating Temperature Range | -40°C to +350°C |
| Supply Condition | Annealed (soft) or half-hard |
| Surface Finish | Mirror polished, bright annealed, or as-rolled |
| Standards Compliance | ASTM B151, ASTM B751, ASME B463, EN 1057, ISO 11907 |
Manufacturing Process
Wenzhou Jixing Metal Materials Co., Ltd. employs a rigorous multi-stage manufacturing process to ensure consistent quality and performance of CuNi 70/30 coil tubes:
- Vacuum Induction Melting (VIM): Raw copper and nickel are melted under controlled vacuum conditions to achieve precise chemical composition and minimize inclusion content, ensuring metallurgical purity and homogeneity.
- Continuous Casting: The molten alloy is cast into precision-controlled ingots or billets with tightly specified dimensions and surface quality.
- Hot Rolling & Extrusion: Billets are hot-rolled and extruded to produce seamless tube blanks with uniform wall thickness and minimal residual stress.
- Cold Drawing: Seamless tube blanks are cold-drawn through precision dies to achieve final dimensional tolerances (±0.05 mm OD, ±0.02 mm wall thickness) and enhanced mechanical properties.
- Solution Annealing: Tubes are annealed at 800–900°C in a protective atmosphere to relieve cold-work stresses, restore full ductility, and promote a uniform microstructure free of deformation bands.
- Coiling: Annealed tubes are precisely coiled using hydraulic winding systems with controlled tension to prevent surface marking, kinking, or ovality.
- Quality Inspection: Every coil undergoes 100% hydrostatic testing, ultrasonic flaw detection, eddy current inspection, and visual examination to verify dimensional accuracy, freedom from defects, and compliance with specified standards.
Applications
Primary Applications
- Offshore Oil & Gas Platforms: Seawater cooling circuits, heat exchanger tubes, and process cooling systems on fixed and floating production platforms
- High-Velocity Seawater Systems: Condenser tubes and heat exchanger coils operating at flow rates up to 5.0 m/s where CuNi 90/10 would suffer accelerated erosion-corrosion
- Power Generation: Seawater-cooled condenser tubes in coastal power plants and nuclear facilities
- Desalination Plants: Multi-stage flash (MSF) and multi-effect distillation (MED) evaporator tubes
- Marine Propulsion Systems: Coolant circuits for marine diesel engines, lubricating oil coolers, and hydraulic systems on naval and commercial vessels
- Chemical Processing: Heat exchangers handling acidic or chloride-containing process streams
Why CuNi 70/30 Over CuNi 90/10?
In high-velocity seawater applications (>2.0 m/s), the CuNi 70/30 alloy demonstrates a corrosion rate reduction of 40–60% compared to CuNi 90/10. The elevated nickel content provides a more stable passive film and superior resistance to selective leaching, extending service life by 2–3 times in aggressive marine environments. For offshore platforms and high-flow cooling circuits, this translates to reduced maintenance downtime, lower lifecycle costs, and enhanced operational reliability.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ASTM B151 / ASTM B751 — Material and product standard compliance
- ASME B463 — Coil heat exchanger material specifications
- EN 10204 3.1 — Full mill test certificates provided with every shipment
- DNV / Lloyd's / ABS — Marine classification society approval available
- NACE MR0175 / ISO 15156 — Compliance for sour service applications
Every production lot is accompanied by a comprehensive mill test report documenting chemical analysis (including trace elements), mechanical test results, heat treatment records, and dimensional verification data. Third-party inspection (TPI) by organizations such as SGS, Bureau Veritas, or DNV is available upon customer request.
Why Choose Wenzhou Jixing Metal Materials Co., Ltd.
- Specialized Expertise: Decades of experience in copper-nickel alloy tube production with deep knowledge of marine and offshore applications
- Custom Engineering: Flexible production capabilities to accommodate non-standard diameters, wall thicknesses, coil configurations, and surface finishes
- Full Traceability: From raw material sourcing to final delivery, every coil is fully traceable with complete documentation
- Competitive Lead Times: Optimized production scheduling and inventory management for reliable on-time delivery
- Technical Support: Dedicated engineering team available for application-specific material selection, design consultation, and performance validation