UNS C71500 (70/30) Cupronickel – High-Performance Copper-Nickel Alloy for Severe Marine Service
UNS C71500 (70/30 cupronickel) is a copper-nickel alloy containing approximately 70% copper and 30% nickel, with controlled iron and manganese additions to enhance corrosion resistance and mechanical properties.
This alloy offers medium-high strength, good creep resistance at elevated temperatures, and exceptional performance in high-velocity seawater, marine, and chemical environments. It is the preferred material for seawater cooler pipes, ship propellers, power plant condensers, and offshore platform components where maximum corrosion resistance is required.
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1. Product Specifications & Physical Data
UNS C71500 is available in multiple mill forms for severe marine and industrial applications requiring verified corrosion resistance and mechanical properties.
Available Forms: Pipe, tube, plate, sheet, bar, forgings, and fittings .
Specifications: ASTM B111, ASTM B151, ASTM B171, ASME SB-111, UNS C71500, EN CW354H .
| Chemical Composition (Weight %) | UNS C71500 Specification |
|---|---|
| Copper (Cu) | 65.0 min. (Balance) |
| Nickel (Ni) | 29.0 - 33.0 |
| Iron (Fe) | 0.40 - 1.0 |
| Manganese (Mn) | 1.0 max. |
| Carbon (C) | 0.05 max. |
| Lead (Pb) | 0.05 max. |
| Zinc (Zn) | 1.0 max. |
| Sulfur (S) | 0.02 max. |
| Physical Properties | Metric | Imperial |
|---|---|---|
| Density | 8.9 g/cm³ | 0.323 lb/in³ |
| Melting Range | 1170 - 1240°C | 2140 - 2265°F |
| Modulus of Elasticity | 150 GPa | 21.8 × 10⁶ psi |
| Thermal Conductivity (RT) | 29 W/m·K | 201 BTU·in/hr·ft²·°F |
| Coefficient of Expansion (20-300°C) | 16.2 µm/m·°C | 9.0 µin/in·°F |
| Mechanical Properties (Annealed) | Metric | Imperial |
|---|---|---|
| Tensile Strength (min.) | 380 MPa | 55 ksi |
| Yield Strength (0.2% offset, min.) | 140 MPa | 20 ksi |
| Elongation (min.) | 30% | 30% |
| Hardness (Rockwell B) | 70 - 90 | 70 - 90 |
2. Operating Conditions & Selection Criteria
UNS C71500 is specified when designers require maximum resistance to seawater corrosion, erosion-corrosion, and impingement attack in high-velocity marine environments.
Service Temperature Range: Design temperature up to 371°C (700°F) in annealed condition; retains mechanical properties at cryogenic temperatures without embrittlement .
Seawater Performance: Excellent resistance to seawater corrosion with corrosion rates ≤0.003 mm/a. The higher nickel content (29-33%) provides superior resistance to erosion-corrosion and impingement attack compared to 90/10 cupronickel .
High-Velocity Capability: Withstands high-velocity seawater flow (up to 3-4 m/s) in condenser and heat exchanger tubes where lower alloys would fail .
Iron Addition: Controlled iron content (0.40-1.0%) promotes formation of a protective iron-rich oxide film, enhancing corrosion resistance in polluted or stagnant seawater conditions .
Stress Corrosion Cracking: Excellent resistance to stress corrosion cracking in marine and industrial environments .
Biofouling Resistance: Naturally resistant to marine organism attachment, reducing maintenance requirements for seawater systems .
Hydrogen Embrittlement: High resistance to hydrogen embrittlement, suitable for environments where other alloys may fail .
3. Fabrication & Material Comparison
Annealing: 649-816°C (1200-1500°F) × 15-60 minutes, air cool; relieves cold work stresses .
Hot Working: 927-1038°C (1700-1900°F); good hot workability .
Cold Working: Good cold workability using standard methods; 20% machinability rating .
Machining: Machinability rate of 20; requires sharp tools and adequate lubrication; surface finish achievable up to Ra 0.1 μm .
Welding: Excellent weldability using soldering, brazing, oxyacetylene, GTAW/TIG, GMAW/MIG, SMAW, spot, seam, and butt welding methods .
Deep Drawing: Supports deep drawing for complex component fabrication .
| Material Comparison | UNS C71500 (70/30) | UNS C70600 (90/10) | 316L Stainless | Aluminum Bronze |
|---|---|---|---|---|
| Copper Content | 65-70% | 88% min. | — | 80-90% |
| Nickel Content | 29-33% | 9-11% | 10-14% | — |
| Tensile Strength (min.) | 380 MPa | 310 MPa | 485 MPa | 550-650 MPa |
| High-Velocity Seawater | Excellent | Good | Moderate | Good |
| Impingement Resistance | Superior | Good | Moderate | Good |
| Chloride SCC Resistance | Excellent | Excellent | Poor | Good |
| Creep Resistance at High Temp | Good | Moderate | Good | Good |
| Relative Cost | Higher | Moderate | Moderate | Lower |
| Primary Use | High-velocity seawater, condensers, nuclear | General seawater piping | General marine | Propellers, pumps |
4. Applications
Marine Engineering: Seawater cooler pipes, ship propellers, propeller sleeves, offshore platform components, seawater intake systems
Power Generation: Nuclear plant condensers, steam surface condensers, heat exchangers, feedwater heaters
Chemical Processing: Distillation towers, reactors, heat exchanger sleeves, process vessels for non-oxidizing media
Aerospace: Engine components, hydraulic system pipelines, fuel systems
Desalination: Evaporator tubing, heat exchangers for high-temperature brine service
Industrial: High-temperature process equipment requiring creep resistance
Contact ZYTC Alloy for certified UNS C71500 (70/30) cupronickel with complete traceability, EN 10204 3.1/3.2 certificates, and competitive pricing. Available in pipe, tube, plate, sheet, bar, forgings, and fittings for marine, power generation, and chemical processing applications.
📧 Email: daisy@zytcsteel.com
📲 WhatsApp: +86 17335753350
🌐 Website: https://www.zytcalloys.com/product-UNS-C71500-CuNi70/30-Copper-Nickel-Alloy.html
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