70/30 - C71500 Copper Nickel (CDA 715)

Copper nickel 70/30 contains 70% copper and 30% nickel. It also has a small amount of manganese and iron in it, making it more resistant to erosion and corrosion. The resistance of 70/30 CuNi has been found to be much better in polluted seawater and in high-velocity waters (up to 4.5 m/s). Cu-Ni 70/30 can be readily welded, fabricated and cold worked, without the use of any special materials.

ASTM B151, ASTM B466, ASTM B111, ASTM B171, ASME SB466, ASME SB111, ASME SB151, ASME SB171, DIN 2.0872, BS 2871 CN102, EN CW352H, MIL-C-1726F, MIL-C-24679, MIL-T-16420K

Related designations: C71500, DEF STAN 02-879 Annex B, BS2874, CuNi30Mn1Fe, CN107, NES780, DGS320, C71520, EN 12164, CW354H, ASTM B151, DEF STAN 02-780, 2.0882

Superior erosion and corrosion resistance – Performs much better than other copper alloys in polluted seawater and high-velocity waters up to 4.5 m/s.

High strength with good ductility – Tensile strength reaches 75 ksi (rod, H02) with 15% elongation; annealed products offer 45-55 ksi with 40-45% elongation.

Excellent fabricability – Can be readily welded, fabricated, and cold worked without special materials or procedures.

Proven in marine environments – Used extensively in salt water piping, flanges, heat exchangers, and condenser components.

Good thermal conductivity – 29 W/(m·K) at room temperature, suitable for heat transfer applications.

Low magnetic permeability – Non-magnetic, suitable for sensitive electronic environments.

Selection guidance: Choose C71500 for polluted seawater, high-velocity conditions above 3.5 m/s, marine defense applications, and high-pressure steam lines. Choose C70600 for clean seawater, lower velocities, and budget-sensitive projects.

Salt water piping and pipe fittings

Refrigerator and condenser components

Weld wire and boiler parts

Salt water flanges

Heat exchangers and cooling plants

Welding backing rings

Elongation at Break (rolled-H04 / hard drawn-H80): 11.0%

Elongation at Break (annealed): 40%

Poisson's Ratio: 0.325

Shear Modulus: 57.2 GPa (8300 ksi)

Tensile Strength: 359 MPa (52,000 psi)

Q1: C71500 vs C70600 – which one handles higher seawater velocity?

C71500 handles higher seawater velocity, up to 4.5 m/s. The page states that 70/30 CuNi resistance is "much better in polluted seawater and in high-velocity waters (up to 4.5 m/s)." C70600 (90/10) is typically limited to 3-3.5 m/s. For applications with fast flow or turbulence, choose C71500.

Q2: What is the density of C71500 for weight calculation?

C71500 density is 0.323 lb/in³ (8.94 g/cm³). For pipe weight calculation: (OD - wall) × wall × 10.68 = lb per foot. For example, a 1" OD × 0.065" wall C71500 pipe weighs approximately 0.65 lb per foot.

Q3: What is the thermal conductivity of 70/30 copper nickel?

Thermal conductivity is 29 W/(m·K) at room temperature (17 Btu/(sq ft·ft·hr·°F)). This is lower than pure copper but acceptable for heat exchangers and condensers where seawater corrosion resistance is the primary requirement.

Q4: Can C71500 be welded without special materials?

Yes, C71500 can be readily welded without special materials. The page states the alloy "can be readily welded, fabricated and cold worked, without the use of any special materials." Recommended methods include gas shielded arc welding, coated metal arc welding, and resistance welding.

Q5: What is the machinability rating of C71500?

Machinability rating is 20 (free-cutting brass = 100). This is listed in the fabrication properties table. For rod in H02 temper (1/2 hard), tensile strength is 75 ksi with 15% elongation – this temper machines better than annealed. Use sharp carbide tools and lower cutting speeds.

Q6: What is the difference between OS025 and OS035 tube temper?

OS025 has higher strength (60 ksi tensile, 25 ksi yield); OS035 is softer (54 ksi tensile, no yield specified). OS035 has nominal grain size 0.035 mm and hardness 36 HRF. OS025 has finer grain size (0.025 mm) with hardness 45 HRB / 80 HRF. Choose OS035 for bending and tube expansion; choose OS025 for higher strength in straight pipe runs.

Q7: What military specifications cover C71500?

MIL-C-1726F, MIL-C-24679, MIL-T-16420K, MIL-T-15005, and MIL-T-22214 cover C71500. For naval seawater piping and condenser applications, these MIL specs apply. The page also lists DEF STAN 02-879 and DEF STAN 02-780 for UK military applications.

Q8: What is the annealing temperature for C71500?

Annealing temperature is 1200-1500°F. Hot working temperature is 1700-1900°F. These temperatures are listed in the thermal properties table. Annealing restores ductility after cold working. Hot working at the higher range is for forging and forming operations.

Q9: What are the common applications of C71500?

Salt water piping and pipe fittings, refrigerator and condenser components, weld wire, boiler parts, salt water flanges, heat exchangers, cooling plants, and welding backing rings. The page lists all these applications. The alloy's corrosion resistance in polluted and high-velocity seawater makes it suitable for demanding marine service.

Chemical verification: Optical emission spectrometry checks every heat for Ni (29-33%), Fe (0.40-1.0%), Mn (≤1.0%), Pb (≤0.05%), Zn (≤1.0%). Cu + sum of named elements minimum 99.5%.

Mechanical testing: Tensile testing confirms tensile strength (54-75 ksi depending on form and temper), yield strength (20-70 ksi), and elongation (15-45%). Hardness testing verifies proper temper (35-80 HRB, 36-80 HRF).

Flattening test (tube): Ensures ductility for forming – no cracks when flattened to specified percentage of OD.

Expansion test (tube): Confirms ability to expand into tubesheets – no cracks after expansion.

Hydrostatic testing: Each tube is pressure tested to ensure no leaks. Test pressure per ASTM B111 / B466.

Eddy current testing (when specified): 100% non-destructive testing for pits, slivers, and wall variations per ASTM E243.

Dimensional inspection: OD, wall thickness, straightness, and length checked against ASTM B111 / B466 tolerances.

Traceability: All test reports linked to heat number. Records retained for full material traceability. Third-party inspection available.

Bundling: Pipes are strapped into hexagonal bundles with steel bands every 1.5 meters. Plywood separators between each layer prevent surface scratching.

Bundle weight: Maximum 2000 kg (4400 lbs) per bundle for safe handling.

End protection: Plastic caps on both pipe ends keep debris out and protect threads or beveled ends.

Cut length packaging: Shorter pipes are packed into ISPM-15 certified wooden crates with foam lining.

Coiled pipe packaging: Long continuous lengths are wound onto steel reels. Reel flange is marked with heat number, size, and total length.

Labels on every package: Alloy (C71500 70/30), heat number, OD × wall thickness, length, quantity, PO number, net weight, gross weight.

Sea freight protection: Desiccant bags placed inside moisture-barrier plastic liners for tropical destinations or storage exceeding 6 months.

Export packaging: All wooden crates and pallets are ISPM-15 certified for international shipping.

Melting: Induction furnaces of 6 ton capacity with argon stirring. Composition precisely controlled to Ni 29-33%, Fe 0.4-1.0%, Cu balance.

Casting: Horizontal continuous caster produces 200 mm (8") diameter billet specifically for tube extrusion.

Extrusion: 3500 ton extrusion press pierces the billet to form a hollow shell (tube blank). Tooling accommodates OD from 30 mm to 250 mm.

Cold pilgering: Multiple pilger mill stands reduce OD and wall thickness. Can reduce OD by up to 75% in a single pass. Maximum finished tube length is 40 meters.

Drawing: Draw benches of 30 ton and 60 ton capacity perform final sizing. Internal surface finish achieves Ra 0.4 µm or better. Straightness after drawing is 0.5 mm per meter (0.020" per foot).

Annealing: Car bottom furnace operating at 1200-1500°F (650-815°C) with rapid water quench. Produces OS035 (nominal grain size 0.035 mm) or OS025 (finer grain) temper.

Stress relieving: Lower temperature furnace produces HR50 drawn and stress relieved temper for higher strength applications.

Straightening: 6-roll rotary straighteners correct bending from drawing process. Achieves straightness of 0.5 mm per meter.

Eddy current testing: 100% online inspection with rotating probe detects pinholes, slivers, longitudinal and transverse defects. Rejects marked with spray paint.

Hydrostatic testing: Pressure up to 6000 psi. Each tube held at test pressure for minimum 5 seconds with automated pressure recording.

Inspection laboratory: OES spectrometer for chemical analysis, universal tensile tester, hardness tester (Rockwell B/F), and metallurgical microscopes.

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