C70600 (B10) Copper Nickel Alloy Heat Exchanger Pipe

C70600 and the B10 Designation

C70600 is the unified numbering system designation for the 90/10 copper nickel alloy, and B10 is the short form of the Chinese designation BFe10-1-1 given to the same material in GB/T 5231. The two names appear together on datasheets and drawings because both are in everyday use: an engineer trained on American standards writes C70600, while a fabricator working to Chinese standards writes B10 or BFe10-1-1, and the pipe, tube, plate and fittings they order are the same alloy.

The material is one of the standard workhorses of seawater service. It is ductile enough to be bent and expanded, strong enough to carry pressure, readily welded and brazed, and it resists both general corrosion and impingement attack in flowing sea water. Those characteristics explain its long standing use in desalination plant, shipboard sea water systems, power station condensers and process heat exchangers.

Chemical Composition

All values are percentages by mass. Copper is described here as the remainder because that is how the specification expresses it, and it corresponds to a nominal level of roughly 88 to 89 percent. Statements sometimes seen in circulation that the copper content of this alloy is only 65 to 70 percent are incorrect: that range belongs to the 70/30 composition, which is roughly seventy percent copper with about thirty percent nickel and is a different grade. Because the two are sometimes confused, a purchase order should always quote the full designation and the product standard rather than a percentage alone.

Standards and Mechanical Requirements

Mechanical property requirements depend on the temper ordered: the annealed condition is the softest and most formable and is normally used for tube that will be bent or rolled into a tube sheet, while lightly drawn tempers give higher strength with less ductility. The ordering standard states the minimum tensile strength, yield strength and elongation for each temper, and the mill certificate for the batch reports the actual results against those figures.

Product Forms and Supply Range

Applications: Desalination, Marine and Process Plant

Multi stage flash and reverse osmosis desalination plant, including brine heater and distiller tubing.

Shipboard sea water piping, cooling systems, condensers and heat exchangers.

Power station surface condensers, feedwater heaters and auxiliary coolers.

Refinery and petrochemical coolers and condensers, including sulphide bearing service.

Offshore platform sea water systems, firewater lines and potable water circuits.

In these duties the alloy's performance depends on maintaining an even, clean flow of water over the metal surface. Design velocity should be selected to avoid both stagnation, which encourages deposits and under-deposit attack, and excessive speed, which erodes the protective film; water boxes and channels should distribute flow uniformly; and cleaning should be gentle enough to leave the surface film intact.

Fabrication, Installation and Inspection

Copper nickel pipe and tube are fabricated with the ordinary shop processes used for copper alloys: cutting, bending, expanding, welding and brazing. Gas shielded arc welding with a matching filler gives the best results, and joints must be dry and free of grease, paint and marking dye before welding, since contamination is the usual cause of porosity. After welding the heat tint should be removed chemically or mechanically to restore uniform corrosion resistance.

Tube that is rolled into a tube sheet needs the correct expansion sequence and torque, and stress relief of expanded ends is worthwhile where the service environment is aggressive. Pipework should be insulated or shielded where it passes through dissimilar metal structures, and gaskets and fasteners chosen so that galvanic couples do not concentrate attack.

Inspection follows the ordering standard: chemical analysis, tensile testing in the ordered temper, dimensional checks, pressure tightness testing and an electric non-destructive test such as eddy current examination for the covered sizes. Certificates can be issued to EN 10204 type 3.1, and third-party inspection can be witnessed at the producing works. Material is packed with protective caps and wrapping in strapped bundles or wooden cases for sea transport.

FAQ

Q: Is B10 the same as C70600?
Yes. B10 is the short form of the Chinese designation BFe10-1-1, and it describes the same 90/10 copper nickel alloy registered in the unified numbering system as C70600.

Q: What is the copper content of C70600?
Copper is the balance of the composition, at a nominal level of about 88 to 89 percent, with nickel at 9 to 11 percent and iron at 1.0 to 1.8 percent.

Q: Why is a copper content of 65 to 70 percent sometimes quoted for this alloy?
That range belongs to the 70/30 copper nickel grade rather than to 90/10, and the two alloys should not be treated as interchangeable.

Q: Which standard covers C70600 exchanger pipe?
ASTM B111/B111M for seamless condenser and heat exchanger tube, ASTM B466 for seamless pipe, ASTM B467 for welded pipe, and GB/T 1527 with the GB/T 5231 designation system for Chinese requirements.

Q: Is welded pipe as good as seamless pipe?
For many sea water duties a properly made welded pipe performs well and allows larger diameters and heavier walls, but seamless tube remains the usual choice for condensers where pressure and expansion demands are high.

Q: What tests accompany the pipe on delivery?
Chemical analysis, tensile testing, dimensional inspection, pressure tightness testing and an electric non-destructive examination as required by the ordering standard, with certificates available to EN 10204 type 3.1.