Precious Metal CuCr50
GB CuCr50
CuCr50 is a 50/50 copper-chromium contact composite produced by press-and-sinter, chromium-skeleton infiltration or vacuum melting, and is the standard material for medium-voltage vacuum interrupters.
Reference datasheet — CuCr50 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 PM-I condition
CuCr50 tempers and conditions
CuCr50 is supplied in 4 conditions, soft to hard. PM-I is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Press and solid-state sintered | Pick when chopping-current level and dielectric withstand matter more than conductivity; blended powder pressed and solid-state sintered gives fine, uniform chromium at 37% IACS. | 220 | 300 | 5 | 105 HB | 37 % IACS |
PM-IDefault Chromium skeleton infiltrated with copper | Choose as the default contact blank: a pre-sintered chromium skeleton vacuum-infiltrated with pure copper gives high density, 43% IACS conductivity and moderate cost. | 245 | 350 | 8 | 95 HB | 43 % IACS |
Sintered plus repress/resinter or hot pressing | Use for large-diameter contacts breaking high currents; repressing and resintering or hot pressing after solid-state sintering cuts porosity and lifts strength to 380 MPa and 41% IACS. | 270 | 380 | 8 | 110 HB | 41 % IACS |
Hot isostatic pressed | Choose for high-end vacuum interrupter contacts needing high dielectric withstand, low chopping current and long electrical life; hot isostatic pressing gives near-full density, minimal gas content. | 290 | 410 | 10 | 112 HB | 42 % IACS |
Supply forms, finishes and certifications
Ways CuCr50 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
VAM | VAM/VIM | Supply option |
WRT | Densified blank hot forged / rolled to finished contact form | Supply option |
What is CuCr50?
CuCr50 is a 50/50 copper-chromium contact composite produced by press-and-sinter, chromium-skeleton infiltration or vacuum melting, and is the standard material for medium-voltage vacuum interrupters. Typical values are 7.95 g/cm³, 245 MPa yield, 350 MPa tensile, 8% elongation, 95 HB, 190 W/m·K, 43% IACS and service to 300 °C, supplied as cup, disc and axial-magnetic-field slotted contacts. It combines low chopping current with high dielectric recovery, but cold formability is very poor, it is not fusion welded, and the chromium particles make machining abrasive (score 32). W70Cu30 is the usual alternative for air-break arcing contacts. CuCr50 has a density of 7.95 g/cm³ (0.287 lb/in³), lighter than 99% of precious metal grades. It melts at 1,076°C (1,969 °F). CuCr50 has a yield strength of 245 MPa (35.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 76% of precious metal grades. Elongation at break is 8% and the elastic modulus is 150 GPa (21.8 Msi).
What is CuCr50 used for?
- vacuum circuit breakers
- vacuum contactors
- medium-voltage switchgear interrupters
Advantages
- Low embodied carbon — 6.5 kg CO₂/kg, better than 100% of precious metal grades
- Lightweight — 7.95 g/cm³ (0.287 lb/in³), better than 99% of precious metal grades
- Stiff — 150 GPa (21.8 Msi), better than 87% of precious metal grades
- High strength — 245 MPa (35.5 ksi), better than 76% of precious metal grades
Limitations
- Hard to polish — 55/100, worse than 97% of precious metal grades
- Limited formability — 20/100, worse than 96% of precious metal grades
- Needs corrosion protection — 55/100, worse than 94% of precious metal grades
- Limited ductility — 8%, worse than 92% of precious metal grades
- Difficult to machine — 32/100, worse than 80% of precious metal grades
CuCr50 properties
Typical room-temperature values for CuCr50-PM-I; bars are the position among precious metal grades.
Physical3
CuCr50 has a density of 7.95 g/cm³ (0.287 lb/in³), lighter than 99% of precious metal grades. It melts at 1,076°C (1,969 °F).
Mechanical10
CuCr50 has a yield strength of 245 MPa (35.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 76% of precious metal grades. Elongation at break is 8% and the elastic modulus is 150 GPa (21.8 Msi).
Thermal6
CuCr50 is rated for continuous service to 300°C (572 °F). It conducts heat at 190 W/m·K (109.8 BTU/hr·ft·°F), better than 68% of precious metal grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
CuCr50 conducts electricity at 43 % IACS, better than 68% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 94% of precious metal grades.
Sustainability4
Producing a kilogram of CuCr50 takes about 95 MJ of energy and emits 6.5 kg of CO₂ — less than 100% of precious metal grades. Typical recycled content is 15%.
Manufacturability7
CuCr50's machinability is poor (32/100, worse than 80% of precious metal grades); weldability poor (25/100); formability poor (20/100).
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 precious metal family
Yield strength against density for every precious metal grade FabDigit runs. CuCr50 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with CuCr50
Is CuCr50 easy to machine?
The hard chromium particles are strongly abrasive: use fine-grain carbide or PCD tooling with large rake angles, low feed and full coolant. After finish turning the contact face, vacuum degas the part to secure dielectric withstand.
Can CuCr50 be welded?
Fusion welding is generally not used because of porosity and chromium segregation. Contacts are brazed to copper conductor stems with BAg or BCu filler in a vacuum or hydrogen furnace.
Can CuCr50 be formed, bent or molded?
Standard routes are powder pressing plus sintering, chromium-skeleton infiltration, or vacuum melting; dense blanks can be hot forged or hot rolled into cup or axial-magnetic-field slotted contacts. Cold forming capability is very poor and cracking is likely.
CuCr50 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 |
|---|---|---|
| Crchromium powder or Cr skeleton, typically 40–150 µm particle size | 48 – 52 | 50 |
| Ototal oxygen; vacuum-melted parts can reach ≤0.03% | ≤ 0.06 | 0.04 |
| Fe | ≤ 0.05 | 0.02 |
| Si | ≤ 0.03 | 0.01 |
| C | ≤ 0.02 | 0.01 |
| Ngas content directly affects dielectric withstand level | ≤ 0.02 | 0.01 |
| Al | ≤ 0.02 | 0.01 |
| S | ≤ 0.01 | 0 |
| Cuoxygen-free or electrolytic copper | ≥ 48 (balance) |
What surface finishes work on CuCr50?
After finish turning or grinding, clean, degrease and vacuum degas. Conductive joint faces can be silver- or nickel-plated, while arcing faces are left as bare metal with no coating.
Equivalent designations
Standards and trade names that resolve to Precious Metal CuCr50 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Cu-Cr
How much does CuCr50 cost?
CuCr50 is a high-cost precious metal ($$$$), 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.
CuCr50 — frequently asked
What is CuCr50 used for?
CuCr50 is typically used for vacuum circuit breakers, vacuum contactors and medium-voltage switchgear interrupters. In short: standard vacuum interrupter material; low chopping current; poor cold formability.
What is the yield strength of CuCr50?
CuCr50 has a typical yield strength of 245 MPa (35.5 ksi) and a tensile strength of 350 MPa (50.8 ksi) — stronger than 76% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is CuCr50 easy to machine?
Not especially — machinability is rated poor (32/100, worse than 80% of precious metal grades). The hard chromium particles are strongly abrasive: use fine-grain carbide or PCD tooling with large rake angles, low feed and full coolant. After finish turning the contact face, vacuum degas the part to secure dielectric withstand.
Can CuCr50 be welded?
Not readily — weldability is rated poor (25/100). Fusion welding is generally not used because of porosity and chromium segregation. Contacts are brazed to copper conductor stems with BAg or BCu filler in a vacuum or hydrogen furnace.
What surface finishes work on CuCr50?
After finish turning or grinding, clean, degrease and vacuum degas. Conductive joint faces can be silver- or nickel-plated, while arcing faces are left as bare metal with no coating.
Can CuCr50 be formed, bent or molded?
Standard routes are powder pressing plus sintering, chromium-skeleton infiltration, or vacuum melting; dense blanks can be hot forged or hot rolled into cup or axial-magnetic-field slotted contacts. Cold forming capability is very poor and cracking is likely.
What is the maximum service temperature of CuCr50?
CuCr50 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 CuCr50 PM-I and CuCr50-HIP?
PM-I is the default condition — choose as the default contact blank: a pre-sintered chromium skeleton vacuum-infiltrated with pure copper gives high density, 43% IACS conductivity and moderate cost. HIP: choose for high-end vacuum interrupter contacts needing high dielectric withstand, low chopping current and long electrical life; hot isostatic pressing gives near-full density, minimal gas content. Yield strength is 245 MPa in PM-I versus 290 MPa in HIP.
How much does CuCr50 cost?
CuCr50 is a high-cost precious metal ($$$$), 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
- ASM Handbook Vol. 7 — Powder Metallurgy (electrical contact materials) — ASM International (2015)
- ASM Alloy Phase Diagrams — Cu-Cr system — ASM International (2016)
- CuCr (CuCr25/CuCr40/CuCr50) (2023)
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.