Copper Alloy C70250-TM03
Temper
UNS C70250 · ASTM B740 · EN CW112C, CuNi3Si1Mg
TM03 = mill hardened, higher strength
Choose for higher contact normal force and better stress-relaxation resistance with modest forming.
Values for the TM03 condition
Other C70250 tempers and conditions
C70250 is listed in 15 conditions; see the grade overview at C70250.
Compare all 15 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution heat treated | Choose for severe forming or deep drawing, then age (TF00) to develop strength. | 170 | 380 | 35 | 55 HRB | 22 % IACS |
Solution heat treated and cold worked, full hard | Intermediate mill condition supplied when the customer performs its own ageing after stamping. | 520 | 570 | 6 | 157 HB | 24 % IACS |
Mill hardened | Use where the part is severely formed after stamping and no post-forming heat treatment is possible. | 530 | 600 | 13 | 88 HRB | 40 % IACS |
TD01 and precipitation hardened | Lowest-strength aged temper when tight 90° bends in the bad-way direction are required. | 550 | 620 | 12 | 171 HB | 38 % IACS |
Mill hardened | Small strength step above TM00 for contacts with moderately tight bad-way bends. | 600 | 655 | 11 | 176 HB | 40 % IACS |
TD02 and precipitation hardened | Balanced aged temper for stamped contacts needing moderate bending plus high spring force. | 630 | 690 | 9 | 188 HB | 38 % IACS |
TM02Default Mill hardened, half hard | The default stocked strip temper: best all-round mix of ~690 MPa strength, 40 % IACS and formability. | 640 | 700 | 9 | 200 HV | 40 % IACS |
Rolled and order-strengthened | Cold-rolled strip given a low-temperature strengthening/stress-relief anneal for flat, low-springback coil stock. | 645 | 690 | 7 | 188 HB | 38 % IACS |
TM03This page Mill hardened, higher strength | Choose for higher contact normal force and better stress-relaxation resistance with modest forming. | 685 | 740 | 8 | 210 HV | 39 % IACS |
Cold rolled (H03) and precipitation heat treated | Pick when the highest aged spring strength is needed and only generous bend radii are used. | 710 | 760 | 6 | 205 HB | 37 % IACS |
Mill hardened, full hard | For miniature contacts needing maximum spring force with only gentle forming. | 720 | 775 | 6 | 18 HRC | 39 % IACS |
Rolled and order-strengthened, hard | Harder rolled-and-strengthened level for stamped parts requiring high yield with minimal forming. | 730 | 775 | 5 | 209 HB | 37 % IACS |
Mill hardened, extra hard | Extra-high-strength mill-hardened strip for flat springs formed in the good-way direction only. | 755 | 810 | 5 | 20 HRC | 38 % IACS |
TD04 and precipitation hardened | Maximum-strength aged strip for flat springs and contacts formed with large radii only. | 760 | 800 | 4 | 20 HRC | 36 % IACS |
Mill hardened, spring hard | Top mill-hardened level; use for flat, essentially unformed spring elements at maximum load. | 800 | 845 | 4 | 22 HRC | 37 % IACS |
What is C70250-TM03?
C70250-TM03 is C70250 in the TM03 temper — choose for higher contact normal force and better stress-relaxation resistance with modest forming. C70250-TM03 has a yield strength of 685 MPa (99.4 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 8% and the elastic modulus is 131 GPa (19 Msi). C70250-TM03 has a density of 8.82 g/cm³ (0.319 lb/in³), heavier than 63% of copper alloy grades. It melts at 1,065°C (1,949 °F). TM02 is the default condition FabDigit quotes; TM03 is available on request or by drawing note.
Advantages
- High strength — 685 MPa (99.4 ksi), better than 96% of copper alloy grades
- Stiff — 131 GPa (19 Msi), better than 91% of copper alloy grades
Limitations
- Limited ductility — 8%, worse than 83% of copper alloy grades
C70250-TM03 properties
Typical room-temperature values for C70250-TM03; 10 are specific to this condition. Other listed values are C70250 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C70250-TM03 has a density of 8.82 g/cm³ (0.319 lb/in³), heavier than 63% of copper alloy grades. It melts at 1,065°C (1,949 °F).
Mechanical11
C70250-TM03 has a yield strength of 685 MPa (99.4 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 96% of copper alloy grades. Elongation at break is 8% and the elastic modulus is 131 GPa (19 Msi).
Thermal6
C70250-TM03 is rated for continuous service to 200°C (392 °F). It conducts heat at 152 W/m·K (87.8 BTU/hr·ft·°F), better than 73% of copper alloy grades. Thermal expansion is 17.6 µm/m·K (9.78 µin/in·°F).
Electrical3
C70250-TM03 conducts electricity at 39 % IACS, better than 74% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 57% of copper alloy grades.
Sustainability4
Producing a kilogram of C70250-TM03 takes about 58 MJ of energy and emits 4 kg of CO₂ — more than 61% of copper alloy grades. Typical recycled content is 30%.
Manufacturability7
C70250-TM03's machinability is fair (36/100, better than 55% of copper alloy grades); weldability fair (35/100); formability good (58/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C70250-TM03
Is C70250 easy to machine?
Machines like a hard bronze — moderate rating (~30 % of AISI 1212); use sharp carbide, positive rake, high speed and flood coolant; stamping dies wear faster than with brass so carbide tooling is preferred.
Can C70250 be welded?
Not suited to fusion welding (hot-crack sensitive, ageing lost in HAZ); resistance/spot welding, laser microwelding and soldering/brazing are the practical joining routes.
Can C70250 be formed, bent or molded?
Form in TM/TH tempers with grain-direction-aware bend radii (good-way ≈0–1t, bad-way 1–3t depending on temper); for severe draws start from TB00 and age at ~450–480 °C afterwards.
What surface finishes work on C70250?
Readily electroplated with Sn, Ni, Ag or Au and easily soldered; no anodizing — protect with plating or antitarnish rinse to prevent oxide/tarnish on contact surfaces.
C70250 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 |
|---|---|---|
| Ni | 2.2 – 4.2 | 3 |
| Si | 0.25 – 1.2 | 0.65 |
| Mg | 0.05 – 0.3 | 0.15 |
| Zn | ≤ 1 | — |
| Fe | ≤ 0.2 | — |
| Mn | ≤ 0.1 | — |
| Pb | ≤ 0.05 | — |
| CuCu + named elements 99.5 % min | balance | — |
C70250-TM03 — frequently asked
What is C70250-TM03 used for?
C70250-TM03 is typically used for automotive connectors, consumer electronics connectors, precision springs and EMI shielding fingers. In short: beryllium-free connector alloy; strength with 40 % IACS; mill-hardened strip tempers.
What is the yield strength of C70250-TM03?
C70250-TM03 has a typical yield strength of 685 MPa (99.4 ksi) and a tensile strength of 740 MPa (107 ksi) — stronger than 96% of copper alloy grades. Strength varies by condition: see the 15 listed tempers.
Is C70250-TM03 easy to machine?
Not especially — machinability is rated fair (36/100, better than 55% of copper alloy grades). Machines like a hard bronze — moderate rating (~30 % of AISI 1212); use sharp carbide, positive rake, high speed and flood coolant; stamping dies wear faster than with brass so carbide tooling is preferred.
Can C70250-TM03 be welded?
With care — weldability is rated fair (35/100). Not suited to fusion welding (hot-crack sensitive, ageing lost in HAZ); resistance/spot welding, laser microwelding and soldering/brazing are the practical joining routes.
What surface finishes work on C70250-TM03?
Readily electroplated with Sn, Ni, Ag or Au and easily soldered; no anodizing — protect with plating or antitarnish rinse to prevent oxide/tarnish on contact surfaces.
Can C70250-TM03 be formed, bent or molded?
Form in TM/TH tempers with grain-direction-aware bend radii (good-way ≈0–1t, bad-way 1–3t depending on temper); for severe draws start from TB00 and age at ~450–480 °C afterwards.
What is the maximum service temperature of C70250-TM03?
C70250-TM03 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C70250-TM02 and C70250-TB00?
TM02 is the default condition — the default stocked strip temper: best all-round mix of ~690 MPa strength, 40 % IACS and formability. TB00: choose for severe forming or deep drawing, then age (TF00) to develop strength. Yield strength is 640 MPa in TM02 versus 170 MPa in TB00.
Sources
- ASTM B740 — Copper-Nickel-Tin/Copper-Nickel-Silicon Strip for Electrical Connectors — ASTM International (2020)
- ASTM B601 — Temper Designations for Copper and Copper Alloys — ASTM International (2019)
- CDA Alloy Database — C70250 — Copper Development Association (2023)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- High-performance Cu-Ni-Si connector strip datasheets (Wieland/Olin-type C7025) — producer (2022)
- EN 1654 / CW112C CuNi3Si1Mg strip for springs and connectors — CEN (2019)
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.