What Is C71500
C71500 is a wrought copper-nickel alloy with nominally 70 percent copper and 30 percent nickel, strengthened with small amounts of iron and manganese. It is the high-nickel member of the cupronickel family and is specified for seawater piping, condenser tubes, heat exchangers, and marine hardware where maximum corrosion resistance is required. Common specifications are ASTM B151 (rod and bar), ASTM B171 (tube and plate), and ASTM B466/B466M (seamless pipe and tube).
Chemical Composition
| Element | Content (mass %) |
|---|---|
| Copper (Cu) | 65.0 - 70.0 |
| Nickel (Ni), incl. cobalt | 29.0 - 33.0 |
| Iron (Fe) | 0.40 - 1.0 |
| Manganese (Mn) | 1.0 max |
| Zinc (Zn) | 1.0 max |
| Lead (Pb) | 0.05 max |
| Other impurities (total) | 0.5 max |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.94 g/cm3 |
| Melting range | Approx. 1170 - 1240 C |
| Electrical conductivity | Approx. 5% IACS |
| Thermal conductivity | Approx. 29 - 40 W/(m·K) |
| Coefficient of thermal expansion (20 - 200 C) | Approx. 16.2 x 10-6 /C |
| Modulus of elasticity | Approx. 150 GPa |
Mechanical Properties (Typical)
| Condition | Tensile Strength | Yield Strength (0.2%) | Elongation |
|---|---|---|---|
| Annealed | 380 - 450 MPa | 130 - 180 MPa | 35 - 45% |
| Cold drawn / hard | 480 MPa and above | 300 - 450 MPa | 8 - 20% |
Corrosion Resistance
C71500 is the benchmark alloy for seawater service among wrought coppers. It resists general corrosion, pitting, crevice attack, and stress corrosion cracking in chloride environments, and it maintains a protective film that limits biofouling. The 30 percent nickel content also gives excellent resistance to erosion by fast-moving water, making the alloy suitable for high-velocity seawater lines and condenser tubes where 90-10 cupronickel might suffer impingement damage.
Equivalents
| System | Designation |
|---|---|
| UNS | C71500 |
| EN | CuNi30Mn1Fe (CW352H) |
| DIN / W-Nr | 2.0882 |
| JIS | NCu 30-1-1 (C7150) |
C71500 vs Other Marine Alloys
| Property | C71500 (70-30) | C70600 (90-10) | C72200 (CuNi-Cr) |
|---|---|---|---|
| Nickel content | 29 - 33% | 9.0 - 11.0% | 15.0 - 18.0% |
| Relative strength | Highest | Moderate | High |
| Seawater resistance | Excellent | Very good | Very good |
| Typical use | High-velocity seawater, condenser tubes | General marine piping, heat exchangers | Turbulent flow, chemical service |
Applications
Seawater piping and fire mains on ships and offshore platforms
Condenser, evaporator, and heat exchanger tubes
Desalination plants
Feed-water heaters
Hydraulic and pneumatic tubing in marine environments
Frequently Asked Questions
Q: What is the composition of C71500?
A: Copper 65.0 to 70.0 percent, nickel 29.0 to 33.0 percent, iron 0.40 to 1.0 percent, manganese 1.0 percent max, with zinc and lead tightly controlled.
Q: Is C71500 the same as 70-30 cupronickel?
A: Yes. The 70-30 name refers to the nominal copper-to-nickel ratio; C71500 is the UNS designation.
Q: How does C71500 compare with C70600?
A: C71500 has about three times the nickel content of C70600 (90-10), giving higher strength and better resistance to erosion and high-velocity seawater, at higher cost.
Q: Can C71500 be welded?
A: Yes. It welds well with gas tungsten arc and gas metal arc processes using matching 70-30 cupronickel filler, followed by proper cleaning.
Q: What is the thermal conductivity of C71500?
A:Approximately 29 to 40 W/(m·K), typical of high-nickel cupronickels and much lower than pure copper.
Q: What standards cover C71500?
A: ASTM B151, B171, and B466/B466M, with EN CuNi30Mn1Fe (CW352H) and DIN 2.0882 as European equivalents.
Q: Where is C71500 commonly used?
A: Marine piping, condenser and heat exchanger tubes, desalination plant tubing, and feed-water heaters.
