Copper Alloy C75700-O61
Heat-treated state
UNS C75700 · EN CW403J
O61 = annealed
Pick for deep drawing, spinning and severe forming where maximum ductility is needed.
Values for the O61 condition
Other C75700 tempers and conditions
C75700 is listed in 8 conditions; see the grade overview at C75700.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
O61This page Annealed | Pick for deep drawing, spinning and severe forming where maximum ductility is needed. | 152 | 365 | 42 | 75 HB | 9 % IACS |
Quarter hard | Pick when moderate bending/forming must be combined with higher strength than annealed strip. | 330 | 434 | 20 | 110 HB | — |
H02Default Half hard | General-purpose stocked strip temper: balanced strength and bendability for hardware, frames and stampings. | 420 | 496 | 10 | 135 HB | — |
Full hard | Pick for flat springs, contacts and stiff hardware where high strength matters more than bend radius. | 505 | 565 | 4 | 165 HB | — |
Extra hard | Pick for higher-load spring strip formed only with generous bend radii along the grain. | 560 | 620 | 3 | 180 HB | 8.5 % IACS |
Hard drawn | Cold-drawn wire condition for spectacle-frame wire, springs and formed wire parts. | 590 | 655 | 3 | 190 HB | 8.5 % IACS |
Spring hard | Pick for flat springs, clips and contact fingers requiring high elastic limit. | 620 | 675 | 2 | 195 HB | 8.5 % IACS |
Extra spring hard | Maximum-strength rolled strip for demanding spring contacts; essentially no formability across grain. | 660 | 710 | 2 | 208 HB | 8.5 % IACS |
What is C75700-O61?
C75700-O61 is C75700 heat treated to O61 — pick for deep drawing, spinning and severe forming where maximum ductility is needed. C75700-O61 has a yield strength of 152 MPa (22 ksi) and a tensile strength of 365 MPa (52.9 ksi) — weaker than 67% of copper alloy grades. Elongation at break is 42% and the elastic modulus is 124 GPa (18 Msi). C75700-O61 has a density of 8.72 g/cm³ (0.315 lb/in³), lighter than 54% of copper alloy grades. It melts at 1,004°C (1,839 °F). H02 is the default condition FabDigit quotes; O61 is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 90/100, better than 99% of copper alloy grades
- Forms and bends easily — 90/100, better than 89% of copper alloy grades
- Ductile — tolerates forming and impact — 42%, better than 86% of copper alloy grades
- High service temperature — 300°C (572 °F), better than 85% of copper alloy grades
Limitations
- Difficult to machine — 25/100, worse than 86% of copper alloy grades
- High embodied carbon — 4.6 kg CO₂/kg, worse than 82% of copper alloy grades
- Low electrical conductivity — 9 % IACS, worse than 78% of copper alloy grades
- Poor heat conductor — 45 W/m·K (26 BTU/hr·ft·°F), worse than 76% of copper alloy grades
C75700-O61 properties
Typical room-temperature values for C75700-O61; 13 are specific to this condition. Other listed values are C75700 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C75700-O61 has a density of 8.72 g/cm³ (0.315 lb/in³), lighter than 54% of copper alloy grades. It melts at 1,004°C (1,839 °F).
Mechanical12
C75700-O61 has a yield strength of 152 MPa (22 ksi) and a tensile strength of 365 MPa (52.9 ksi) — weaker than 67% of copper alloy grades. Elongation at break is 42% and the elastic modulus is 124 GPa (18 Msi).
Thermal6
C75700-O61 is rated for continuous service to 300°C (572 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), worse than 76% of copper alloy grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
C75700-O61 conducts electricity at 9 % IACS, worse than 78% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (65/100), better than 58% of copper alloy grades.
Sustainability4
Producing a kilogram of C75700-O61 takes about 65 MJ of energy and emits 4.6 kg of CO₂ — more than 81% of copper alloy grades. Typical recycled content is 40%.
Manufacturability7
C75700-O61's machinability is poor (25/100, worse than 86% of copper alloy grades); weldability fair (40/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C75700-O61
Is C75700 easy to machine?
Machinability ~20 % of free-cutting brass — gummy, work-hardening chips; use sharp positive-rake carbide, moderate speed and generous coolant.
Can C75700 be welded?
Resistance and brazing/soldering are preferred; fusion welding risks zinc fume and porosity, so use low-heat processes with adequate ventilation.
Can C75700 be formed, bent or molded?
Excellent cold formability in O61/H01 for deep drawing and stamping; interanneal between heavy reductions and stress-relieve at ~250–300 °C to avoid ammonia-induced SCC.
What surface finishes work on C75700?
Takes a bright silver-white polish and readily accepts Ni, Cr, Ag or Au plating; lacquer or clearcoat for long-term tarnish protection — not anodizable.
C75700 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 |
|---|---|---|
| Cuincludes Ag if reported | 63.5 – 66.5 | 65 |
| NiNi + Co | 11 – 13 | 12 |
| Pb | ≤ 0.05 | — |
| Fe | ≤ 0.25 | — |
| Mn | ≤ 0.5 | — |
| Zn | balance | — |
C75700-O61 — frequently asked
What is C75700-O61 used for?
C75700-O61 is typically used for optical frame components, hardware, nameplates and electrical parts. In short: mid-nickel strip grade; good cold workability; silvery-white stamping alloy.
What is the yield strength of C75700-O61?
C75700-O61 has a typical yield strength of 152 MPa (22 ksi) and a tensile strength of 365 MPa (52.9 ksi) — weaker than 67% of copper alloy grades. Strength varies by condition: see the 8 listed tempers.
Is C75700-O61 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 86% of copper alloy grades). Machinability ~20 % of free-cutting brass — gummy, work-hardening chips; use sharp positive-rake carbide, moderate speed and generous coolant.
Can C75700-O61 be welded?
With care — weldability is rated fair (40/100). Resistance and brazing/soldering are preferred; fusion welding risks zinc fume and porosity, so use low-heat processes with adequate ventilation.
What surface finishes work on C75700-O61?
Takes a bright silver-white polish and readily accepts Ni, Cr, Ag or Au plating; lacquer or clearcoat for long-term tarnish protection — not anodizable.
Can C75700-O61 be formed, bent or molded?
Excellent cold formability in O61/H01 for deep drawing and stamping; interanneal between heavy reductions and stress-relieve at ~250–300 °C to avoid ammonia-induced SCC.
What is the maximum service temperature of C75700-O61?
C75700-O61 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C75700-H02 and C75700-O61?
H02 is the default condition — general-purpose stocked strip temper: balanced strength and bendability for hardware, frames and stampings. O61: pick for deep drawing, spinning and severe forming where maximum ductility is needed. Yield strength is 420 MPa in H02 versus 152 MPa in O61.
Sources
- ASTM B122/B122M Copper-Nickel-Zinc (Nickel Silver) Plate, Sheet, Strip and Rolled Bar — ASTM International (2022)
- ASTM B151/B151M Copper-Nickel-Zinc and Copper-Nickel Rod and Bar — ASTM International (2020)
- CDA Alloy Datasheet C75700 (Nickel Silver 65-12) — Copper Development Association (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- EN 1652 / CW403J CuNi12Zn24 — CEN (1997)
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.