UNS C71640 is a copper-nickel-iron-manganese alloy representing a modified, high-strength version of the 70-30 cupronickel family. With approximately 30% nickel and controlled additions of iron (1.7-2.3%) and manganese (1.5-2.5%), this alloy offers exceptional resistance to high-velocity seawater corrosion, erosion-corrosion, and impingement attack. Originally developed for demanding naval and desalination applications, C71640 is the material of choice for seawater heat exchangers, condenser tubes, and piping systems where standard 90-10 or 70-30 cupronickels may not provide sufficient performance .
1. Product Specifications & Physical DataUNS C71640 is available in seamless and welded tube forms for heat exchanger and desalination service. It is covered by ASTM B111, ASTM B552, and ASTM B543 specifications. Available Forms: Seamless tube, welded tube, pipe, plate, sheet, bar Key Specifications: ASTM B111/B111M (condenser tubes), ASTM B552 (water desalting plant tubes), ASTM B543/B543M (welded heat exchanger tubes)
| Chemical Composition (Weight %) | UNS C71640 Specification |
|---|
| Copper (Cu) | Balance | | Nickel (Ni) | 29.0 - 32.0 | | Iron (Fe) | 1.7 - 2.3 | | Manganese (Mn) | 1.5 - 2.5 | | Carbon (C) | 0.06 max. | | Sulfur (S) | 0.03 max. | | Lead (Pb) | 0.05 max. | | Zinc (Zn) | 1.0 max. |
| Physical Properties | Metric | Imperial |
|---|
| Density | 8.94 g/cm³ | 0.323 lb/in³ | | Melting Range | 1170 - 1240°C | 2140 - 2265°F | | Modulus of Elasticity | 152 GPa | 22.0 × 10⁶ psi | | Thermal Conductivity (RT) | 29 W/m·K | 201 BTU·in/hr·ft²·°F | | Electrical Resistivity | 34 µΩ·cm | 34 µΩ·cm | | Coefficient of Expansion (20-300°C) | 16 µm/m·°C | 8.9 µin/in·°F |
| Mechanical Properties (Annealed) | Metric | Imperial |
|---|
| Tensile Strength (min.) | 420 MPa | 61 ksi | | Yield Strength (0.2% offset, min.) | 150 MPa | 22 ksi | | Elongation (min.) | 30% | 30% | | Hardness (Vickers) | 110 Hv | 110 Hv | | Grain Size (max.) | 0.045 mm | 0.045 mm |
| Mechanical Properties (Hard Temper HR50) | Metric | Imperial |
|---|
| Tensile Strength (min.) | 560 MPa | 81 ksi | | Yield Strength (0.2% offset, min.) | 400 MPa | 58 ksi | | Elongation (min.) | 20% | 20% |
2. Fabrication & Material ComparisonAnnealing: 649-816°C (1200-1500°F), air cool; relieves cold work stresses and restores ductility Hot Working: 927-1038°C (1700-1900°F); good hot workability Cold Working: Good cold workability; can be cold drawn and rolled to achieve hard temper (HR50) with higher strength Machining: Machinability rating of 20 (similar to C71500); requires sharp tools and adequate lubrication Welding: Excellent weldability using GTAW/TIG, GMAW/MIG, and resistance welding methods; matching filler metal recommended
3. ApplicationsWater Desalination: Multi-stage flash (MSF) desalination plants—heat rejection sections, brine heaters, heat recovery sections Marine & Offshore: High-velocity seawater cooling systems, shipboard condensers, offshore platform heat exchangers Power Generation: Coastal power plant condensers, cooling water systems for nuclear and fossil fuel plants Naval Vessels: High-speed ship heat exchangers, condensers, and seawater systems requiring superior erosion resistance Chemical Processing: Heat exchangers for chloride-containing process streams Industrial Cooling: Cooling systems with seawater or brackish water containing suspended solids
Contact ZYTC Alloy for certified UNS C71640 copper-nickel tubes with complete traceability, certificates, and competitive pricing. Available in seamless and welded tubes per ASTM B111 and ASTM B552 for desalination, marine, and power generation applications. Email: daisy@zytcsteel.com WhatsApp/WeChat: +86 17335753350 |
