Copper Alloy C71700
UNS C71700
C71700 is a niobium-stabilised 70/30 copper-nickel in the C70000–C79999 wrought family, developed so that thin-wall tube can be fusion welded without hot cracking or porosity.
Reference datasheet — C71700 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the O61 condition
C71700 tempers and conditions
C71700 is supplied in 7 conditions, soft to hard. O61 is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed to 0.025 mm grain size | Grain-size-controlled anneal for sheet/strip that must be deep drawn or spun without orange peel. | 150 | 390 | 45 | 80 HB | 4.6 % IACS |
O61Default Annealed | Standard stocked condition for seawater and aerospace tubing where bending, flaring and welding are required. | 160 | 400 | 42 | 85 HB | 4.6 % IACS |
Light drawn | Choose for straight tube lengths needing better handling stiffness while still allowing moderate bending. | 275 | 450 | 25 | 118 HB | 4.5 % IACS |
Quarter hard | Mild cold work for flat products that still need forming after cutting. | 310 | 470 | 22 | 125 HB | 4.6 % IACS |
Half hard | General structural flat/rod condition balancing strength and residual formability. | 420 | 540 | 14 | 155 HB | 4.6 % IACS |
Hard drawn | Highest-pressure tubing condition; use where hoop strength governs and no further cold bending is needed. | 515 | 585 | 10 | 9 HRC | 4.5 % IACS |
Full hard | Maximum as-drawn/rolled strength for springs, fasteners and wear faces; minimal further forming. | 550 | 620 | 8 | 13 HRC | 4.5 % IACS |
Supply forms, finishes and certifications
Ways C71700 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WM50 | As-welded tube | Surface finish |
WO50 | Welded tube, cold worked and annealed | Surface finish |
What is C71700?
C71700 is a niobium-stabilised 70/30 copper-nickel in the C70000–C79999 wrought family, developed so that thin-wall tube can be fusion welded without hot cracking or porosity. Engineers use it for aerospace hydraulic and fuel line tubing and for seawater service, where 400 MPa tensile strength, 42% elongation and a self-forming protective oxide are needed; it is supplied as seamless and welded tube, strip and rod, including WO50 and WM50 welded conditions. Electrical conductivity is only 4.6% IACS, service is limited to 350 °C, and the alloy is gummy to machine. Standard C71500 is the cheaper choice when weld sensitivity is not the driver. C71700 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,170°C (2,138 °F). C71700 has a yield strength of 160 MPa (23.2 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 65% of copper alloy grades. Elongation at break is 42% and the elastic modulus is 152 GPa (22 Msi).
What is C71700 used for?
- aircraft hydraulic tubing
- fuel lines
- seawater piping
Advantages
- Stiff — 152 GPa (22 Msi), better than 99% of copper alloy grades
- Good corrosion resistance — 82/100, better than 98% of copper alloy grades
- Readily welded — 88/100, better than 97% of copper alloy grades
- High service temperature — 350°C (662 °F), better than 95% of copper alloy grades
- Ductile — tolerates forming and impact — 42%, better than 86% of copper alloy grades
Limitations
- High embodied carbon — 7.5 kg CO₂/kg, worse than 97% of copper alloy grades
- Low electrical conductivity — 4.6 % IACS, worse than 96% of copper alloy grades
- Difficult to machine — 22/100, worse than 94% of copper alloy grades
- Poor heat conductor — 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 93% of copper alloy grades
C71700 properties
Typical room-temperature values for C71700-O61; bars are the position among copper alloy grades.
Physical3
C71700 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,170°C (2,138 °F).
Mechanical14
C71700 has a yield strength of 160 MPa (23.2 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 65% of copper alloy grades. Elongation at break is 42% and the elastic modulus is 152 GPa (22 Msi).
Thermal6
C71700 is rated for continuous service to 350°C (662 °F). It conducts heat at 29 W/m·K (16.8 BTU/hr·ft·°F), worse than 93% of copper alloy grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
C71700 conducts electricity at 4.6 % IACS, worse than 96% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (82/100), better than 98% of copper alloy grades.
Sustainability4
Producing a kilogram of C71700 takes about 105 MJ of energy and emits 7.5 kg of CO₂ — more than 97% of copper alloy grades. Typical recycled content is 30%.
Manufacturability8
C71700's machinability is poor (22/100, worse than 94% of copper alloy grades); weldability excellent (88/100); formability excellent (85/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the copper alloy family
Yield strength against density for every copper alloy grade FabDigit runs. C71700 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C71700
Is C71700 easy to machine?
Gummy and work-hardening — use sharp positive-rake carbide, low speed (~30–60 m/min), heavy feed, rigid setup and flood coolant to avoid built-up edge.
Can C71700 be welded?
Excellent GTAW/GMAW with CuNi 70/30 (ERCuNi) filler; the Nb addition suppresses weld hot cracking and porosity — keep interpass low, no preheat, argon backing, and avoid sulphur/lead contamination.
Can C71700 be formed, bent or molded?
Very good cold formability in O61 (bend radii ≈1t); high work-hardening rate means interstage anneals at 700–850 °C with rapid cool for severe draws; hot work 900–1050 °C.
C71700 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 – 33 | 31 |
| Feerosion-corrosion resistance | 0.4 – 1 | 0.7 |
| Mndeoxidiser | 0.4 – 1 | 0.7 |
| Nbcolumbium; stabilises weld metal | 0.2 – 0.7 | 0.45 |
| Zn | ≤ 1 | |
| Pb | ≤ 0.05 | |
| C | ≤ 0.05 | |
| S | ≤ 0.02 | |
| P | ≤ 0.02 | |
| Curemainder, ~65–68 % | balance |
What surface finishes work on C71700?
Cannot be anodised; pickle in inhibited sulphuric/chromate-free solutions, then leave bare (self-forming protective oxide in seawater), or electroplate Ni/Sn or lacquer for decorative use — polishes to a bright silvery finish.
Surface treatments FabDigit runs on copper alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
How much does C71700 cost?
C71700 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C71700 — frequently asked
What is C71700 used for?
C71700 is typically used for aircraft hydraulic tubing, fuel lines and seawater piping. In short: weldable 70/30 copper-nickel; aerospace hydraulic tube alloy; highest formability in family.
What is the yield strength of C71700?
C71700 has a typical yield strength of 160 MPa (23.2 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 65% of copper alloy grades. Strength varies by condition: see the 7 listed tempers.
Is C71700 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 94% of copper alloy grades). Gummy and work-hardening — use sharp positive-rake carbide, low speed (~30–60 m/min), heavy feed, rigid setup and flood coolant to avoid built-up edge.
Can C71700 be welded?
Yes — weldability is rated excellent (88/100). Excellent GTAW/GMAW with CuNi 70/30 (ERCuNi) filler; the Nb addition suppresses weld hot cracking and porosity — keep interpass low, no preheat, argon backing, and avoid sulphur/lead contamination.
What surface finishes work on C71700?
Cannot be anodised; pickle in inhibited sulphuric/chromate-free solutions, then leave bare (self-forming protective oxide in seawater), or electroplate Ni/Sn or lacquer for decorative use — polishes to a bright silvery finish.
Can C71700 be formed, bent or molded?
Very good cold formability in O61 (bend radii ≈1t); high work-hardening rate means interstage anneals at 700–850 °C with rapid cool for severe draws; hot work 900–1050 °C.
What is the maximum service temperature of C71700?
C71700 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C71700-O61 and C71700-H04?
O61 is the default condition — standard stocked condition for seawater and aerospace tubing where bending, flaring and welding are required. H04: maximum as-drawn/rolled strength for springs, fasteners and wear faces; minimal further forming. Yield strength is 160 MPa in O61 versus 550 MPa in H04.
How much does C71700 cost?
C71700 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B466/B466M — Seamless Copper-Nickel Pipe and Tube — ASTM International (2020)
- ASTM B122/B122M — Copper-Nickel-Zinc, Copper-Nickel Plate, Sheet, Strip and Rolled Bar — ASTM International (2021)
- CDA Standard Designations for Wrought Copper Alloys (UNS C71700) — Copper Development Association (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (Copper-Nickel in Seawater) — ASM International (2005)
- Copper-Nickel Alloys — Properties and Fabrication Guide — Nickel Institute / CDA UK (2016)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.