What ASTM B111 C70600 Copper Nickel Tubes Are
ASTM B111/B111M is the standard specification for seamless copper and copper-alloy condenser tubes, evaporator tubes and heat exchanger tubes. Within that specification, UNS C70600 is the 90/10 copper-nickel grade, often written as CuNi 90/10, CuNi10Fe1Mn, BFe10-1-1 or CW352H. The alloy is a single-phase solid solution of nickel in copper, which is why it stays ductile after cold drawing, resists chloride pitting and shows almost no susceptibility to stress corrosion cracking in seawater.
The iron and manganese content is not incidental. These two elements are deliberately held inside narrow ranges so that a thin, iron-rich oxide layer forms on the water side during the first weeks of service. That film is what limits general corrosion and impingement attack, and it is also what makes the alloy resistant to biofouling, because marine organisms do not readily settle on a releasing copper-nickel surface. Tubes supplied without the correct iron balance may meet the tensile requirements yet still fail early in high-velocity seawater.
Chemical Composition
| Element | Composition (%) | Function |
|---|---|---|
| Copper, Cu | Remainder | Matrix metal; governs thermal and electrical conductivity |
| Nickel, Ni | 9.0-11.0 | Raises strength and seawater corrosion resistance |
| Iron, Fe | 1.0-1.8 | Forms the protective film; controls impingement resistance |
| Manganese, Mn | 1.0 max | Deoxidiser; stabilises the microstructure |
| Zinc, Zn | 1.0 max | Residual element, controlled for weldability |
| Lead, Pb | 0.05 max | Impurity limit |
Equivalent designations are UNS C70600, EN CW352H, DIN 2.0872, JIS C7060 and the Chinese designation BFe10-1-1 under GB/T 8890 for heat exchanger tube. Larger wall pipe is often ordered to ASTM B466/B466M, and the U-bend version of the same tube follows ASTM B395/B395M.
Mechanical and Physical Properties
| Property | Value |
|---|---|
| Temper designations | O61 annealed; H55 light drawn |
| Tensile strength, annealed | approx. 300-380 MPa |
| Tensile strength, light drawn | approx. 380-420 MPa |
| Elongation, annealed | 30% min in 50 mm |
| Density | 8.94 g/cm³ |
| Thermal conductivity | approx. 29-40 W/m.K |
| Modulus of elasticity | approx. 140 GPa |
| Melting range | approx. 1100-1150 °C |
Strength values are quoted as ranges because the delivered temper, wall thickness and test direction all shift the result; the purchase order fixes the temper code and the certificate reports the actual figures. Annealed tube is used where the tube has to be rolled into a tube sheet or bent, while light drawn tube gives extra stiffness for unsupported spans.
Typical Service Applications
Surface condensers and steam condensers in power stations and on board ship.
Shell-and-tube heat exchangers and oil coolers in marine and offshore packages.
Multi-stage flash and reverse osmosis desalination trains, brine heaters and reject lines.
Cooling water circuits, ballast water systems and hull coolers.
Petrochemical and refinery exchangers handling brackish or chloride-bearing water.
Condenser tube sheets, ferrule stock and waterbox linings in matching 90/10 material.
Sizes, Fabrication and Inspection Points
Condenser tube is normally supplied in outside diameters from about 12 mm to 45 mm with wall thickness of 0.7 mm to 3 mm, and in straight lengths up to 6 m or as U-bends. Larger diameter drawn pipe to ASTM B466 covers roughly 10 mm to 160 mm outside diameter with 1 mm to 8 mm wall, and extruded pipe for headers runs to much heavier walls. Wall thickness selection follows an allowance calculation that adds a corrosion allowance and a manufacturing tolerance to the design pressure requirement.
Roller expanding into a tube sheet needs an annealed tube end and a correctly sized hole; over-rolling creates residual stress and later cracking. Welding is done by TIG or MIG with matching ERCuNi filler, a preheat is not required, and the joint area has to be clean and dry because copper-nickel picks up carbon and sulphur from marking inks and oil. Drilling must avoid graphite-bearing lubricants for the same reason.
Inspection normally covers chemical analysis, tensile and flattening tests, eddy-current testing of the finished tube, pneumatic or hydrostatic pressure testing, dimensional checks and a visual examination of the bore. Cleanliness matters as much as dimensions: tubes are shipped with capped ends and dry, and they should be stored indoors on timber rather than on bare steel, since contact with steel and with chlorides starts pitting before installation.
FAQ
Q: What is the difference between C70600 and C71500?
C70600 contains about 10% nickel and C71500 contains about 30% nickel. The 70/30 grade is stronger and tolerates higher seawater velocity, while the 90/10 grade offers better thermal conductivity, easier forming and lower cost for the majority of clean seawater duties.
Q: Why are iron and manganese specified so tightly in C70600?
They are the elements that grow and maintain the protective oxide film on the water side. Below the specified iron range the film is weak and impingement corrosion starts quickly, and above it the alloy can become sensitive to hot cracking during welding.
Q: Which standards cover C70600 tubes apart from ASTM B111?
Seamless copper-nickel pipe and tube is covered by ASTM B466/B466M, U-bend heat exchanger tube by ASTM B395/B395M, and the matching ASME designations are SB111, SB466 and SB395. European orders frequently reference EN 12451 for heat exchanger tube.
Q: What flow velocity can 90/10 copper-nickel tube accept in seawater?
Published design guidance generally allows continuous clean seawater velocities of roughly 2.5 m/s to 3.5 m/s for 90/10 tube, and slightly higher for 70/30. Tubes containing sand or entrained air need a lower limit or a protective ferrous sulphate treatment during commissioning.
Q: Is C70600 tube suitable for fresh water and steam service?
Yes. The alloy is used in condensers and feedwater heaters on the steam side as well as the water side, and it handles fresh water, brackish water and many neutral and alkaline process solutions. Strongly oxidising acids and ammonia-bearing media are the exceptions and should be referred for a separate corrosion assessment.
Q: How is the tube delivered for export shipment?
Straight lengths are bundled in wooden cases with end caps, U-bent tubes are nested in wooden frames, and every bundle carries the heat number, size, temper and standard on a weatherproof label so that the mill certificate can be matched on arrival.
