Chromium copper C18200 – UNS C18200
Precipitation-hardening copper with ≈ 1% Cr
Copper with 0.6 – 1.2% chromium, precipitation hardenable, offering ≈ 80% IACS conductivity and tensile strength of ≈ 450 – 530 MPa in the aged condition. It keeps much of its hardness at moderate temperatures, which is why it is used in welding electrodes and electrical parts that heat up. Contains no beryllium.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | C18200 |
| W.Nr./EN | CW105C – CuCr1 |
| DIN | 2.1291 (CuCr) |
| Trade names | CuCr1, RWMA Class 2 |
| Others | MIL-C-19311 (forgings, bar and strip) |
Standards by product form
| Form | Standard |
|---|---|
| Bar | MIL-C-19311; EN 12163 (CW105C)* |
| Forging | MIL-C-19311; EN 12420 (CW105C)* |
| Wire | ASTM F9 |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7407.10.10 | 7407.10 | 7407.10.5050 | 7407 10 00 |
| Hot-rolled bar | 7407.10.10 | 7407.10 | 7407.10.5050 | 7407 10 00 |
| Flange and fitting | 7412.10.00 | 7412.10 | 7412.10.0000 | 7412 10 00 |
Tariff class: refined copper (by chemical composition, under the Chapter 72 Notes and Section XV Note 5). Copper alloyed with chromium (and zirconium) within the limits of Chapter 74 Note 1 a) counts as refined copper.
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
CDA / UNS C18200
| Element | Range (%) |
|---|---|
| Cr | 0.6 – 1.2 |
| Fe | ≤ 0.10 |
| Si | ≤ 0.10 |
| Pb | ≤ 0.05 |
| Cu | balance (Cu + named elements ≥ 99.5) |
Mechanical properties
typical, bar (CDA)
| Property | Value |
|---|---|
| Solution treated (TB00): tensile strength | ≈ 310 MPa |
| Aged (TF00, Ø 25 mm): tensile strength | ≈ 495 MPa |
| Aged (TF00, Ø 25 mm): yield strength (0.5%) | ≈ 450 MPa |
| Aged (TF00, Ø 25 mm): elongation | ≈ 18% |
| Cold worked and aged (TH04): tensile strength | ≈ 530 MPa |
| Hardness, aged | ≈ 70 – 82 HRB |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.89 g/cm³ |
| Melting range | 1,070 – 1,075 °C |
| Modulus of elasticity | 117 GPa |
| Electrical conductivity (aged) | ≈ 80% IACS |
| Thermal conductivity (20 °C) | ≈ 324 W/m·K |
| Thermal expansion (20–100 °C) | 17.6 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Begins to soften above ≈ 450 °C*; for hotter service, prefer chromium-zirconium copper C18150. |
| Heat treatment | Solution treatment at ≈ 1,000 – 1,030 °C with rapid cooling. Aging at ≈ 460 °C for ≈ 3 h, air cooling. Hot working between ≈ 815 and 925 °C. |
| Welding | Good brazing and soft soldering. TIG/MIG welding possible, with loss of hardening in the affected zone. Spot, seam and oxyacetylene welding not recommended. |
| Machining | Low machinability (≈ 20, C36000 = 100). Sharp tool, positive rake and coolant; best in the aged condition. |
Typical applications
- Electrodes and electrode holders for resistance welding
- Contacts, terminals and busbars that run hot
- Circuit breaker and switch components
- Welding machine parts and conductive clamps
- Molds and components needing heat transfer
Alternatives: Chromium-zirconium copper C18150 for a higher softening temperature and electrode life; low-beryllium copper C17510 when more hardness is needed.
Frequently asked questions
What is the chemical composition of Chromium copper C18200?
Per CDA / UNS C18200: Cr 0.6 – 1.2; Fe ≤ 0.10; Si ≤ 0.10; Pb ≤ 0.05; Cu balance (Cu + named elements ≥ 99.5).
Which standards cover Chromium copper C18200?
Bar: MIL-C-19311; EN 12163 (CW105C)*. Forging: MIL-C-19311; EN 12420 (CW105C)*. Wire: ASTM F9.
Up to what temperature can Chromium copper C18200 be used?
Begins to soften above ≈ 450 °C*; for hotter service, prefer chromium-zirconium copper C18150.
Which materials can replace Chromium copper C18200?
Chromium-zirconium copper C18150 for a higher softening temperature and electrode life; low-beryllium copper C17510 when more hardness is needed.
