CU · copper alloy
Beryllium Copper C17200 (UNS C17200)
Machines like a hard brass in the annealed state and like a tool steel after ageing. It is bought for the combination of strength and conductivity that nothing else provides - with a health hazard attached.
Quoting this material
- Typical lead time
- 15–25 working days
- Condition
- Mill hardened, or solution annealed for forming and machining then aged
- Achievable finish
- Ra 1.6 µm typical · Ra 0.8 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
Machines like a hard brass in the annealed state and like a tool steel after ageing. It is bought for the combination of strength and conductivity that nothing else provides - with a health hazard attached.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength (aged) | 1,100–1,400 | MPa |
| Yield strength (aged) | 1,000–1,200 | MPa |
| Elongation (aged) | 3–10 | % |
| Hardness (aged) | 38–42 | HRC |
| Thermal conductivity | 105 | W/m·K |
| Modulus of elasticity | 128 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Mill hardened, or solution annealed for forming and machining then aged
Heat treatment
Precipitation hardening: solution anneal, machine or form, then age at 315–345 °C for 2–3 hours. Ageing is predictable, distortion is modest, and the strength roughly doubles.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Finished before ageing where possible, since the aged condition is hard. Plating or a conversion coating is common for corrosion resistance.
Tooling and cutting parameters
Cutting speed
- 80–150 m/min annealed · 40–70 m/min aged (carbide)
Feed
- 0.08–0.20 mm/rev turning · 0.05–0.12 mm/tooth milling
Tooling
- Coated carbide; CBN for the aged condition
Coolant
- Flood, and the swarf must be managed as a controlled material
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Injection mould cores and inserts
- Non-sparking tools and hand tools
- Electrical springs and connectors
- Resistance welding electrodes
- Aerospace bushings and bearings
DFM notes for this grade
- Beryllium dust is a serious health hazard: machining has to be done wet, with extraction, and the swarf and sludge need controlled disposal. This is a process requirement, not a preference
- Ageing after machining moves the part slightly, so the finishing allowance and the sequence both matter
- The conductivity is why it is used - for a mould core, the heat transfer is what shortens the cycle; do not substitute a tool steel without checking the cooling time
Questions buyers ask
- Is beryllium copper dangerous to machine?
- The alloy is safe in solid form; the hazard is the dust and mist produced by machining. Machining wet, with extraction and controlled disposal of the swarf, is how it is handled - and the same rules apply to grinding and polishing, where the airborne fraction is higher.
- Why would a mould core be made from beryllium copper?
- Thermal conductivity. It conducts heat at roughly three times the rate of a tool steel, so a beryllium copper core pulls heat out of a thick section and shortens the cycle. On a part with a heavy boss or a deep rib, that is a direct saving on every cycle.
Grades we would quote instead
C18200 Chrome Copper
6/10Copper with chromium for strength: roughly 80% of the conductivity of pure copper and about twice the strength, and it machines better than C110 because it is harder.
17-4 PH
4/10In the annealed condition it machines like a tough 304; in H900 it is hard enough that finishing has to be done by grinding or hard turning.
C11000 ETP Copper
6/10Pure copper: gummy, prone to built-up edge and famous for long stringy chips.