Copper Alloy C71640-HR50
Supply condition
UNS C71640
HR50 = drawn and stress relieved
Choose for high-pressure or high-velocity seawater piping needing 345 MPa minimum yield with residual stresses removed to avoid SCC.
Values for the HR50 condition
Other C71640 tempers and conditions
C71640 is listed in 3 conditions; see the grade overview at C71640.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
O61Default Annealed | Standard stocked condition for seawater condenser and heat-exchanger tube where bending, expanding and tube-sheet rolling are required. | 220 | 515 | 35 | 120 HB | 4.3 % IACS |
Light drawn | Light cold-drawn tube giving straighter, stiffer lengths with moderate strength gain where no heavy re-forming is needed. | 330 | 550 | 20 | 150 HB | — |
HR50This page Drawn and stress relieved | Choose for high-pressure or high-velocity seawater piping needing 345 MPa minimum yield with residual stresses removed to avoid SCC. | 380 | 570 | 18 | 160 HB | 4.2 % IACS |
What is C71640-HR50?
C71640-HR50 is C71640 supplied in the HR50 condition — choose for high-pressure or high-velocity seawater piping needing 345 MPa minimum yield with residual stresses removed to avoid SCC. C71640-HR50 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 570 MPa (82.7 ksi) — stronger than 77% of copper alloy grades. Elongation at break is 18% and the elastic modulus is 152 GPa (22 Msi). C71640-HR50 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,171°C (2,140 °F). O61 is the default condition FabDigit quotes; HR50 is available on request or by drawing note.
Advantages
- Stiff — 152 GPa (22 Msi), better than 99% of copper alloy grades
- Good corrosion resistance — 80/100, better than 96% of copper alloy grades
- Readily welded — 85/100, better than 95% of copper alloy grades
- High service temperature — 280°C (536 °F), better than 78% of copper alloy grades
- High strength — 380 MPa (55.1 ksi), better than 77% of copper alloy grades
Limitations
- Poor heat conductor — 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 98% of copper alloy grades
- Low electrical conductivity — 4.2 % IACS, worse than 98% of copper alloy grades
- High embodied carbon — 7.5 kg CO₂/kg, worse than 97% of copper alloy grades
C71640-HR50 properties
Typical room-temperature values for C71640-HR50; 16 are specific to this condition. Other listed values are C71640 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C71640-HR50 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,171°C (2,140 °F).
Mechanical13
C71640-HR50 has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 570 MPa (82.7 ksi) — stronger than 77% of copper alloy grades. Elongation at break is 18% and the elastic modulus is 152 GPa (22 Msi).
Thermal6
C71640-HR50 is rated for continuous service to 280°C (536 °F). It conducts heat at 25 W/m·K (14.4 BTU/hr·ft·°F), worse than 98% of copper alloy grades. Thermal expansion is 15.9 µm/m·K (8.83 µin/in·°F).
Electrical3
C71640-HR50 conducts electricity at 4.2 % IACS, worse than 98% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 96% of copper alloy grades.
Sustainability4
Producing a kilogram of C71640-HR50 takes about 95 MJ of energy and emits 7.5 kg of CO₂ — more than 95% of copper alloy grades. Typical recycled content is 30%.
Manufacturability8
C71640-HR50's machinability is poor (34/100, worse than 53% of copper alloy grades); weldability excellent (85/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C71640-HR50
Is C71640 easy to machine?
Tough and gummy — use sharp positive-rake carbide, low speed/heavy positive feed and copious coolant to avoid work hardening and built-up edge (≈20% of free-cutting brass).
Can C71640 be welded?
Readily GTAW/GMAW welded with matching 70/30 Cu-Ni filler (ERCuNi); keep interpass low, no preheat, and use very clean, oxide- and sulfur-free surfaces to avoid porosity and hot cracking.
Can C71640 be formed, bent or molded?
Excellent cold formability in O61 for bending, expanding and tube-sheet rolling; intermediate anneals ~700–800 °C needed for heavy cold work, and drawn tempers should be stress-relieved before seawater service.
What surface finishes work on C71640?
Not anodizable; pickle/passivate before commissioning and grow the protective oxide with clean flowing seawater — avoid sulfide-polluted water during start-up; can be polished or coated but usually used bare.
C71640 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| NiNi + Co | 29 – 32 | 30 |
| Feraises erosion-corrosion resistance | 1.7 – 2.3 | 2 |
| Mnkey distinction vs C71500 | 1.5 – 2.5 | 2 |
| Zn | ≤ 1 | — |
| Pb | ≤ 0.05 | — |
| C | ≤ 0.06 | — |
| S | ≤ 0.03 | — |
| P | ≤ 0.02 | — |
| Curemainder, nominally ~64–66% | balance | — |
C71640-HR50 — frequently asked
What is C71640-HR50 used for?
C71640-HR50 is typically used for high-velocity seawater piping, naval piping systems and condenser tubes. In short: strongest Cu-Ni here; erosion-corrosion resistant 70/30; high-velocity seawater grade.
What is the yield strength of C71640-HR50?
C71640-HR50 has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 570 MPa (82.7 ksi) — stronger than 77% of copper alloy grades. Strength varies by condition: see the 3 listed tempers.
Is C71640-HR50 easy to machine?
Not especially — machinability is rated poor (34/100, worse than 53% of copper alloy grades). Tough and gummy — use sharp positive-rake carbide, low speed/heavy positive feed and copious coolant to avoid work hardening and built-up edge (≈20% of free-cutting brass).
Can C71640-HR50 be welded?
Yes — weldability is rated excellent (85/100). Readily GTAW/GMAW welded with matching 70/30 Cu-Ni filler (ERCuNi); keep interpass low, no preheat, and use very clean, oxide- and sulfur-free surfaces to avoid porosity and hot cracking.
What surface finishes work on C71640-HR50?
Not anodizable; pickle/passivate before commissioning and grow the protective oxide with clean flowing seawater — avoid sulfide-polluted water during start-up; can be polished or coated but usually used bare.
Can C71640-HR50 be formed, bent or molded?
Excellent cold formability in O61 for bending, expanding and tube-sheet rolling; intermediate anneals ~700–800 °C needed for heavy cold work, and drawn tempers should be stress-relieved before seawater service.
What is the maximum service temperature of C71640-HR50?
C71640-HR50 is rated for continuous use to about 280°C (536 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C71640-O61 and C71640-HR50?
O61 is the default condition — standard stocked condition for seawater condenser and heat-exchanger tube where bending, expanding and tube-sheet rolling are required. HR50: choose for high-pressure or high-velocity seawater piping needing 345 MPa minimum yield with residual stresses removed to avoid SCC. Yield strength is 220 MPa in O61 versus 380 MPa in HR50.
Sources
- ASTM B111/B111M — Copper and Copper-Alloy Seamless Condenser Tubes and Ferrule Stock — ASTM International (2021)
- ASTM B466/B466M — Seamless Copper-Nickel Pipe and Tube — ASTM International (2020)
- CDA Alloy Database — C71640 — Copper Development Association (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.