ASTM B111 C70600 Copper Nickel Seamless Tube CuNi 90/10 U Bend Heat Exchanger Tube
ASTM B111 UNS C70600 / CuNi 90/10 Temper O61 Copper Nickel Seamless Tube U Bend Heat Exchanger Tube
ASTM B111 C70600 (CuNi 90/10) U bend tubes are seamless and specifically designed for marine heat exchangers and condensers. Composed of 90% copper and 10% nickel with iron, they offer excellent corrosion resistance, especially against seawater and biofouling. The U-bend configuration accommodates thermal expansion in shell-and-tube systems. However, they are sensitive to high-velocity turbulence at the bend (impingement attack) and must not be used in polluted water containing sulfides, which cause rapid pitting.
Cu-Ni 90/10 vs. The Competition
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vs. Carbon Steel (SA179): SA179 is cheaper and stronger, but it rusts instantly in seawater. Cu-Ni is chosen where corrosion resistance is mandatory.
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vs. Stainless Steel (316L): Stainless steel can suffer from "Crevice Corrosion" in stagnant seawater (under barnacles or gaskets). Cu-Ni handles stagnant conditions (with proper velocities) better. Also, Cu-Ni has superior biofouling resistance.
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vs. Titanium: Titanium is virtually immune to seawater corrosion but is extremely expensive and has poorer heat transfer than copper alloys. Cu-Ni is the "mid-range" option: better corrosion resistance than steel, lower cost than titanium.
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 |
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
1. Seawater Heat Exchangers
2. Offshore Oil & Gas Platforms
3. Power Plant Auxiliary Coolers
4. Firewater Systems (Trim Coolers)
5. Hydraulic Oil Coolers
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