ASTM B111 UNS C71500 CuNi 70/30 Copper Nickel Seamless Tube Heat Exchanger Tube
ASTM B111 UNS C71500 / CuNi 70/30 Copper Nickel Seamless Tube
ASTM B111 UNS C71500 is the proven, reliable standard for seamless tubes in clean seawater heat exchange. Its success hinges on proper water chemistry (clean, oxygenated), correct flow velocity, and adherence to sound fabrication practices to preserve its innate corrosion properties. It is chosen not for its absolute strength, but for its predictable, long-term performance in one of the most corrosive natural environments.
Environmental & Lifecycle Considerations
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Sustainability: Copper-nickel is 100% recyclable without loss of properties, with a high recycled content in production.
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Lifecycle Cost: While the initial cost is higher than carbon steel or aluminum brass, the Total Cost of Ownership (TCO) over a 25-40+ year lifespan in seawater is often lower due to minimal maintenance, no required chemical dosing, and high reliability.
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Biofouling Resistance: Its natural anti-fouling property eliminates the need for toxic anti-fouling paints or coatings within tubing, making it an environmentally preferred choice for seawater systems.
Chemical Composition of Copper Alloys
| Designation | Chemical Composition % | ||||||||
| Cu | Sn | Al | As | Ni | Fe | Mn | Pb max. | Zn | |
| C44300 | 70.0-73.0 | 0.9-1.2 | – | 0.02-0.06 | – | 0.06 max | – | 0.07 | Rem |
| C68700 | 76.0-79.0 | – | 1.8-2.5 | 0.02-0.06 | – | 0.06 max | – | 0.07 | Rem |
| C70400 | Rem | – | – | – | 4.8-6.2 | 1.3-1.7 | 0.3-0.8 | 0.05 | 1.0max |
| C70600 | Rem | – | – | – | 9.0-11.0 | 1.0-1.8 | 1.0max | 0.05 | 1.0max |
| C71500 | Rem | – | – | – | 29.0-33.0 | 0.4-1.0 | 1.0max | 0.05 | 1.0max |
| C71640 | Rem | – | – | – | 29.0-32.0 | 1.7-2.3 | 1.5-2.5 | 0.05 | 1.0max |
Equivalent Grades of Copper Alloys
| Material Designation | Corresponding Material Symbol | ||||
| GB/T8890 | ASTM B111 | BS2871 | JIS H3300 | DIN1785 | |
| Copper-Nickel | BFe10-1-1 | C70600 | CN102 | C7060 | CuNi10Fe1Mn |
| BFe30-1-1 | C71500 | CN107 | C7150 | CuNi30Mn1Fe | |
| (BFe30-2-2) | C71640 | CN108 | C7164 | CuNi30Fe2Mn2 | |
| (BFe5-1.5-0.5) | C70400 | – | – | – | |
| B7 | – | – | – | – | |
| Aluminums Brass | HAL77-2 | C68700 | CZ110 | C6870 | CuZn20Al2 |
| Admiralty Brass | HSn70-1 | C44300 | CZ111 | C4430 | CuZn28Sn1 |
| Boric Brass | Hsn70-18 | – | – | – | – |
| HSn70-1 AB | – | – | – | – | |
| Arsenical Brass | H68A | – | CZ126 | – | – |
| Brass Tube | H65/H63 | C28000/C27200 | CZ108 | C2800/C2700 | CuZn36/CuZn37 |
Tensile Requirements:
| Copper or Copper Alloy UNS NO. | Temper Designation | Tensile Strength | Yield Strength | |
| Standard | Former | min ksi | min ksi | |
| C44300 | O61 | annealed | 45 | 15 |
| C68700 | O61 | annealed | 50 | 18 |
| C70400 | H55 | light-drawn | 38 | 30 |
| C70600 | H55 | light-drawn | 45 | 15 |
| C71500 | O61 | annealed | 52 | 18 |
| C71640 | O61 | annealed | 63 | 25 |
Application
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Superior Seawater Corrosion Resistance: Forms a tight, protective surface oxide film. Highly resistant to impingement attack, stress corrosion cracking (SCC), and macro-fouling (biomarine growth attaches poorly compared to other metals).
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Key Applications:
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Seawater Cooled Condensers & Heat Exchangers (power plants, ships, offshore platforms).
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Desalination Plant (Multi-Stage Flash & Multi-Effect Distillation) evaporator and heat rejection tubes.
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Shipboard Piping for fire mains, bilge, and ballast systems.
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Marine Engineering and coastal infrastructure.
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