What the 90/10 Round Tube Is
ASTM B466/B466M covers seamless copper-nickel pipe and tube in straight lengths for general engineering service and includes UNS C70600 among its alloys. A "90/10 round tube" is simply that alloy supplied in the 90% copper, 10% nickel composition, round section, seamless form and in the finished size the exchanger or piping drawing requires.
The grade is the standard workhorse of seawater-cooled equipment. It combines moderate strength with excellent thermal conductivity and a corrosion behaviour that suits chloride-bearing water: it is immune to chloride stress corrosion cracking, resists biofouling better than steel and stainless steel, and forms a protective surface film that is continuously maintained by the iron in the alloy.
Chemical Composition
| Element | Content, % |
|---|---|
| Copper, incl. silver | Remainder |
| Nickel, incl. cobalt | 9.0 - 11.0 |
| Iron | 1.0 - 1.8 |
| Manganese | 1.0 max |
| Lead | 0.05 max |
| Zinc | 1.0 max |
A typical cast analysis falls close to 88.6% copper, 10.0% nickel and about 1.4% iron, which shows how the iron addition sits in the middle of its window in normal production. That iron is the element most often under-supplied in low-cost material, and it is the element that decides long-term performance in seawater.
Equivalent Designations
| System | Designation |
|---|---|
| ASTM / UNS | C70600 |
| BS | CN102 |
| JIS | C7060 |
| EN / NF | CuNi10Fe1Mn |
| IS | CuNi10Fe1 |
Because so many designations describe the same alloy, drawings from different regions can look inconsistent when they are in fact compatible. The check that matters is that the designated composition window and the required temper match the duty, not that the label is identical.
Mechanical and Physical Data
| Property | O60 annealed | H55 drawn | H80 drawn |
|---|---|---|---|
| Tensile strength, min | 260 MPa | 310 MPa | 345 MPa |
| Yield strength, min | 90 MPa | 240 MPa | 275 MPa |
| Density | 8.94 g/cm³ | ||
| Melting range | Approximately 1105 - 1140 C | ||
Annealed tube is the normal supply condition for heat exchanger duty because the tube has to be expanded into the tube sheet and often bent. The drawn tempers are used for small-bore piping and for components that must resist mechanical damage.
Dimensions and Tolerances
Round tube is ordered by outside diameter and wall thickness, with the tolerance scheme and gauging practice defined by the specification. Points that decide whether tubes assemble correctly:
Outside diameter tolerance, which must suit the tube sheet hole and the expansion clearance.
Wall thickness tolerance, including any eccentricity allowance, so that minimum wall is maintained around the circumference.
Roundness, because ovality reduces the quality of the expanded joint.
Straightness and length tolerance for straight tubes; developed length and bend radius tolerance for U-bent tubes.
Cleanliness of the bore, since scale or debris left in the tube affects both heat transfer and the eddy-current examination.
Applications
Heat exchanger and condenser tubes in power, marine and process plants.
Cooling water and seawater piping in shipbuilding and offshore installations.
Desalination plant tube bundles and distiller tubes.
Refinery and chemical plant coolers where chlorides rule out stainless steel.
Automotive and industrial heat transfer components, including brake and power steering tubing on some designs.
Inspection and Handling
Chemical analysis, tensile testing and hardness testing on each lot.
Flattening, expansion or flare testing to demonstrate forming behaviour.
Hydrostatic or pneumatic pressure testing, and eddy-current examination for condenser-grade tube.
Grain size verification where the customer's specification requires it.
Keep tubes dry and protected in store; copper-nickel surfaces tarnish and can pick up chloride and sulfur contamination from packaging materials and site dust.
FAQ
Q: What does 90/10 mean?
It describes the nominal composition: about 90% copper and 10% nickel. The nickel range in the specification is 9.0 to 11.0%, and the alloy also carries 1.0 to 1.8% iron plus manganese, both of which are needed for corrosion resistance in seawater.
Q: Is 90/10 tube suitable for potable water?
Copper-nickel is used in water systems, but potable water approval depends on local regulatory requirements for the specific product and installation. For seawater and industrial cooling water, the alloy's performance is well established and needs no special approval beyond the project specification.
Q: Which temper should be ordered for a condenser retube?
Annealed tube is normally specified because it must be expanded into the existing tube sheet and may have to be bent. The retube procedure should also confirm the tube sheet hole condition, since an oversized or corroded hole changes the expansion behaviour more than the tube temper does.
Q: Can 90/10 and 70/30 tubes be mixed in one exchanger?
They can be installed in separate circuits, but mixing grades in the same bundle is not advisable. The two alloys have different hardness and expansion behaviour, and different corrosion resistance, so a mixed bundle complicates both installation and later failure analysis.
Q: How should tube ends be prepared before expansion?
Ends should be cut square, deburred, cleaned of all traces of oil, iron and chloride contamination, and measured for ovality. Cleaning is the single most important step: contamination pressed into the tube sheet during expansion becomes the initiation site for corrosion.
