Copper Alloy C12900
UNS C12900
C12900 is a fire-refined tough pitch copper with a specified minimum silver content, which raises resistance to softening after brazing, soldering or moderate service heat while keeping 98 % IACS electrical conductivity and 386 W/m·K thermal conductivity.
Reference datasheet — C12900 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 H04 condition
C12900 tempers and conditions
C12900 is supplied in 11 conditions, soft to hard. H04 is the default FabDigit quotes; the values on this page are for it.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed to 0.050 mm grain size | Softest commercial anneal — pick for deep drawing, severe forming and maximum conductivity. | 69 | 221 | 45 | 42 HB | 101 % IACS |
As hot extruded | As-extruded bar, rod, bus bar and commutator sections before any drawing or annealing. | 69 | 220 | 50 | 42 HB | 100 % IACS |
Annealed to 0.025 mm grain size | Fine-grain anneal — forming with better surface finish (less orange peel) than OS050. | 76 | 235 | 42 | 48 HB | 100 % IACS |
As hot rolled | Mill temper for hot-rolled plate and bus plate where soft, formable copper is acceptable. | 76 | 228 | 45 | 45 HB | 100 % IACS |
1/8 hard | Slight stiffening while keeping most forming ductility — good for lightly formed conductive parts. | 190 | 250 | 30 | 60 HB | 100 % IACS |
Quarter hard | Balanced temper for moderate bending with useful spring-back resistance. | 205 | 262 | 25 | 70 HB | 99 % IACS |
Half hard | General-purpose semi-rigid temper for bus bar, gaskets and formed conductive hardware. | 230 | 276 | 14 | 80 HB | 98 % IACS |
H04Default Full hard | Standard stocked hard temper for bus bar, commutator segments and hard-drawn conductor parts. | 280 | 315 | 6 | 95 HB | 98 % IACS |
Extra hard | Between full hard and spring; used where extra stiffness is needed without spring-temper flatness. | 295 | 330 | 5 | 100 HB | 97 % IACS |
Spring hard | Spring-hard strip for contacts, clips and gaskets that must resist set at slightly elevated temperature. | 310 | 345 | 4 | 105 HB | 97 % IACS |
Extra spring hard | Maximum cold-worked strength for thin strip springs; essentially no further forming possible. | 325 | 365 | 4 | 110 HB | 97 % IACS |
What is C12900?
C12900 is a fire-refined tough pitch copper with a specified minimum silver content, which raises resistance to softening after brazing, soldering or moderate service heat while keeping 98 % IACS electrical conductivity and 386 W/m·K thermal conductivity. It is used for commutator bars and general electrical hardware in strip, bar and drawn profile form, and tolerates service to 200 °C — above the 150 °C limit of the plain FRTP grades. The alloy is still oxygen-bearing, so hydrogen embrittlement applies and machinability is only 25; silver-bearing ETP coppers such as C11400 are the closest alternative. C12900 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,065°C (1,949 °F). C12900 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 315 MPa (45.7 ksi) — stronger than 59% of copper alloy grades. Elongation at break is 6% and the elastic modulus is 120 GPa (17.4 Msi).
What is C12900 used for?
- Commutator bars and segments
- General electrical hardware
- Busbar and connector stock
- Brazed electrical assemblies
- Motor and generator components
- Formed terminals and lugs
- Soldered heat-transfer parts
Advantages
- High electrical conductivity — 98 % IACS, better than 94% of copper alloy grades
- Conducts heat well — 386 W/m·K (223 BTU/hr·ft·°F), better than 93% of copper alloy grades
Limitations
- Limited ductility — 6%, worse than 89% of copper alloy grades
- Difficult to machine — 25/100, worse than 86% of copper alloy grades
C12900 properties
Typical room-temperature values for C12900-H04; bars are the position among copper alloy grades.
Physical3
C12900 has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,065°C (1,949 °F).
Mechanical13
C12900 has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 315 MPa (45.7 ksi) — stronger than 59% of copper alloy grades. Elongation at break is 6% and the elastic modulus is 120 GPa (17.4 Msi).
Thermal6
C12900 is rated for continuous service to 200°C (392 °F). It conducts heat at 386 W/m·K (223 BTU/hr·ft·°F), better than 93% of copper alloy grades. Thermal expansion is 17 µm/m·K (9.44 µin/in·°F).
Electrical3
C12900 conducts electricity at 98 % IACS, better than 94% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 68% of copper alloy grades.
Sustainability4
Producing a kilogram of C12900 takes about 57 MJ of energy and emits 3.9 kg of CO₂ — less than 52% of copper alloy grades. Typical recycled content is 50%.
Manufacturability8
C12900's machinability is poor (25/100, worse than 86% of copper alloy grades); weldability fair (40/100); formability poor (30/100).
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. C12900 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C12900
Is C12900 easy to machine?
Gummy and stringy (rating ≈20 % of free-cutting brass) — use sharp positive-rake carbide, high speed, generous soluble-oil coolant; hard tempers cut cleaner than annealed.
Can C12900 be welded?
Oxygen-bearing tough pitch copper: use GTAW/GMAW with low heat input or resistance welding; avoid oxyacetylene and any hydrogen-containing atmosphere above ~370 °C to prevent hydrogen embrittlement.
Can C12900 be formed, bent or molded?
Excellent cold formability in OS tempers (deep draw, roll form, bend to 0T); hard and spring tempers need generous bend radii and interstage anneals at 375–650 °C.
C12900 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 |
|---|---|---|
| Ag≈16 troy oz per short ton silver minimum — the defining addition of C12900 | ≥ 0.05 | 0.06 |
| Otough pitch oxygen, typically 0.02–0.05 % as Cu2O; not a specification limit | ≈ 0.03 | 0.03 |
| CuCu + Ag combined, minimum per ASTM B5 / CDA registration for fire-refined tough pitch copper | ≥ 99.88 (balance) |
What surface finishes work on C12900?
Solders and brazes readily; can be tin-, nickel- or silver-plated, mechanically polished to bright lustre, or lacquered/patinated — tarnishes in air if left bare.
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 C12900 cost?
C12900 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.
C12900 — frequently asked
What is C12900 used for?
C12900 is typically used for commutator bars and segments, general electrical hardware, busbar and connector stock, brazed electrical assemblies, motor and generator components and formed terminals and lugs. In short: silver-bearing softening resistance; 98 % IACS conductivity; 200 °C service copper.
What is the yield strength of C12900?
C12900 has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 315 MPa (45.7 ksi) — stronger than 59% of copper alloy grades. Strength varies by condition: see the 11 listed tempers.
Is C12900 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 86% of copper alloy grades). Gummy and stringy (rating ≈20 % of free-cutting brass) — use sharp positive-rake carbide, high speed, generous soluble-oil coolant; hard tempers cut cleaner than annealed.
Can C12900 be welded?
With care — weldability is rated fair (40/100). Oxygen-bearing tough pitch copper: use GTAW/GMAW with low heat input or resistance welding; avoid oxyacetylene and any hydrogen-containing atmosphere above ~370 °C to prevent hydrogen embrittlement.
What surface finishes work on C12900?
Solders and brazes readily; can be tin-, nickel- or silver-plated, mechanically polished to bright lustre, or lacquered/patinated — tarnishes in air if left bare.
Can C12900 be formed, bent or molded?
Excellent cold formability in OS tempers (deep draw, roll form, bend to 0T); hard and spring tempers need generous bend radii and interstage anneals at 375–650 °C.
What is the maximum service temperature of C12900?
C12900 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 C12900-H04 and C12900-OS050?
H04 is the default condition — standard stocked hard temper for bus bar, commutator segments and hard-drawn conductor parts. OS050: softest commercial anneal — pick for deep drawing, severe forming and maximum conductivity. Yield strength is 280 MPa in H04 versus 69 MPa in OS050.
How much does C12900 cost?
C12900 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 B5 — Electrolytic Tough Pitch / fire-refined copper refinery shapes — ASTM International (2021)
- CDA Alloy Database — C12900 fire-refined tough pitch copper with silver — Copper Development Association (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASTM B152/B152M — Copper Sheet, Strip, Plate and Rolled Bar — ASTM International (2019)
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.