Copper Alloy C72500-H08
Supply condition
UNS C72500 · EN CW351H, CuNi9Sn2
H08 = spring hard
Pick for high-force contact springs and washers where bend radii are generous and stress relief follows forming.
Values for the H08 condition
Other C72500 tempers and conditions
C72500 is listed in 10 conditions; see the grade overview at C72500.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for deep drawing, severe forming or as the starting stock before customer-side stamping and stress relief. | 150 | 380 | 35 | 45 HRB | 11.5 % IACS |
As hot rolled | Pick for heavier plate/bar stock where no cold-rolled temper is required and further machining or forming follows. | 180 | 410 | 30 | 50 HRB | 11.5 % IACS |
Quarter hard | Pick when moderate strength must be combined with tight-radius bending in both grain directions. | 400 | 470 | 15 | 66 HRB | 11 % IACS |
H02Default Half hard | Default stocked strip temper: balanced strength and formability for stamped connector shells, lead frames and terminals. | 480 | 530 | 9 | 76 HRB | 11 % IACS |
Full hard | Pick for contact springs and clips needing higher yield and stress-relaxation resistance with simple, mostly good-way bends. | 550 | 590 | 5 | 83 HRB | 11 % IACS |
H04 + stress relieved | Pick when formed springs must keep contact force at 100–150 °C; a low-temperature bake raises yield slightly and cuts stress relaxation. | 580 | 610 | 6 | 187 HB | 11.5 % IACS |
Extra hard | Pick when high spring force is needed and forming is limited to gentle good-way bends. | 605 | 640 | 4 | 87 HRB | 11 % IACS |
H08This page Spring hard | Pick for high-force contact springs and washers where bend radii are generous and stress relief follows forming. | 655 | 690 | 3 | 90 HRB | 11 % IACS |
Extra spring hard | Pick for thin-gauge, high-deflection springs where maximum yield strength outweighs formability. | 690 | 725 | 2.5 | 92 HRB | 11 % IACS |
Strain hardened, half hard | Pick for the highest available strength in thin strip; forming must be limited to flat blanking or very light bends. | 725 | 760 | 2 | 94 HRB | 11 % IACS |
What is C72500-H08?
C72500-H08 is C72500 supplied in the H08 condition — pick for high-force contact springs and washers where bend radii are generous and stress relief follows forming. C72500-H08 has a yield strength of 655 MPa (95 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 3% and the elastic modulus is 138 GPa (20 Msi). C72500-H08 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 72% of copper alloy grades. It melts at 1,060°C (1,940 °F). H02 is the default condition FabDigit quotes; H08 is available on request or by drawing note.
Advantages
- High strength — 655 MPa (95 ksi), better than 96% of copper alloy grades
- Stiff — 138 GPa (20 Msi), better than 95% of copper alloy grades
Limitations
- Limited ductility — 3%, worse than 97% of copper alloy grades
- Limited service temperature — 150°C (302 °F), worse than 96% of copper alloy grades
- Poor heat conductor — 45 W/m·K (26 BTU/hr·ft·°F), worse than 76% of copper alloy grades
C72500-H08 properties
Typical room-temperature values for C72500-H08; 11 are specific to this condition. Other listed values are C72500 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C72500-H08 has a density of 8.89 g/cm³ (0.321 lb/in³), heavier than 72% of copper alloy grades. It melts at 1,060°C (1,940 °F).
Mechanical11
C72500-H08 has a yield strength of 655 MPa (95 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 3% and the elastic modulus is 138 GPa (20 Msi).
Thermal5
C72500-H08 is rated for continuous service to 150°C (302 °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
C72500-H08 conducts electricity at 11 % IACS, worse than 68% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (70/100), better than 76% of copper alloy grades.
Sustainability4
Producing a kilogram of C72500-H08 takes about 62 MJ of energy and emits 4.2 kg of CO₂ — more than 76% of copper alloy grades. Typical recycled content is 30%.
Manufacturability7
C72500-H08's machinability is poor (34/100, worse than 53% of copper alloy grades); weldability good (55/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C72500-H08
Is C72500 easy to machine?
Gummy, low machinability (~20–30 % of free-cutting brass): use sharp, positive-rake carbide, high coolant flow and moderate speeds; harder tempers chip more cleanly than annealed.
Can C72500 be welded?
Resistance and laser welding are good; GTAW/GMAW possible with Cu-Ni filler but keep heat input low and avoid oxide/sulphur pickup — soldering and brazing are the preferred joining routes.
Can C72500 be formed, bent or molded?
Anneal or H01/H02 for deep drawing and tight bends; in H06–H14 restrict to good-way bends with generous radii and stress-relieve formed springs at 200–260 °C.
What surface finishes work on C72500?
Not anodizable; solders and plates readily with Sn, Ni, Ag or Au — Ni underplate is common for lead frames, and bright-rolled strip polishes to a warm silver-grey finish.
C72500 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 |
|---|---|---|
| Niincluding Co | 8.5 – 10.5 | 9.5 |
| Sn | 1.8 – 2.8 | 2.3 |
| Fe | ≤ 0.6 | 0.1 |
| Mn | ≤ 0.2 | 0.05 |
| Zn | ≤ 0.5 | — |
| Pb | ≤ 0.05 | — |
| CuCu + named elements 99.8 % min | balance | — |
C72500-H08 — frequently asked
What is C72500-H08 used for?
C72500-H08 is typically used for connectors, relay springs, lead frames and switch contacts. In short: beryllium-free spring alloy; good stress-relaxation resistance; solders and plates easily.
What is the yield strength of C72500-H08?
C72500-H08 has a typical yield strength of 655 MPa (95 ksi) and a tensile strength of 690 MPa (100 ksi) — stronger than 96% of copper alloy grades. Strength varies by condition: see the 10 listed tempers.
Is C72500-H08 easy to machine?
Not especially — machinability is rated poor (34/100, worse than 53% of copper alloy grades). Gummy, low machinability (~20–30 % of free-cutting brass): use sharp, positive-rake carbide, high coolant flow and moderate speeds; harder tempers chip more cleanly than annealed.
Can C72500-H08 be welded?
Yes — weldability is rated good (55/100). Resistance and laser welding are good; GTAW/GMAW possible with Cu-Ni filler but keep heat input low and avoid oxide/sulphur pickup — soldering and brazing are the preferred joining routes.
What surface finishes work on C72500-H08?
Not anodizable; solders and plates readily with Sn, Ni, Ag or Au — Ni underplate is common for lead frames, and bright-rolled strip polishes to a warm silver-grey finish.
Can C72500-H08 be formed, bent or molded?
Anneal or H01/H02 for deep drawing and tight bends; in H06–H14 restrict to good-way bends with generous radii and stress-relieve formed springs at 200–260 °C.
What is the maximum service temperature of C72500-H08?
C72500-H08 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C72500-H02 and C72500-O61?
H02 is the default condition — default stocked strip temper: balanced strength and formability for stamped connector shells, lead frames and terminals. O61: pick for deep drawing, severe forming or as the starting stock before customer-side stamping and stress relief. Yield strength is 480 MPa in H02 versus 150 MPa in O61.
Sources
- ASTM B122/B122M — Copper-Nickel-Tin, Copper-Nickel and Copper-Nickel-Zinc Plate, Sheet, Strip and Rolled Bar — ASTM International (2022)
- EN 1654 / EN 1652 — Copper and copper alloys, strip for springs and connectors (CuNi9Sn2, CW351H) — CEN (2019)
- C72500 alloy datasheet (properties, tempers, machinability rating) — Copper Development Association (copper.org) (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials (copper and copper alloys) — ASM International (2005)
- Cu-Ni-Sn connector strip datasheets (temper strength/hardness tables) — Wieland / Aurubis Stolberg / Materion (2023)
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.