Chromium-zirconium copper C18150 – UNS C18150
High-conductivity precipitation-hardening copper
Copper alloy with ≈ 1% Cr and a small Zr addition, precipitation hardenable, combining conductivity of ≈ 80% IACS with strength of ≈ 450 – 550 MPa. Zirconium raises the softening temperature compared with chromium copper, which makes it the standard material for resistance welding electrodes (RWMA Class 2). Contains no beryllium.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | C18150 |
| W.Nr./EN | CW106C – CuCr1Zr |
| DIN | 2.1293 (CuCrZr) |
| Trade names | CuCrZr, RWMA Class 2, Elbrodur G (KME) |
| Others | RWMA Class 2 (ISO 5182 A2/2*) |
Standards by product form
| Form | Standard |
|---|---|
| Bar | EN 12163 (CW106C)* |
| Forging | EN 12420 (CW106C)* |
| Plate | EN 1652 (CW106C)* |
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 |
| Plate (> 10 mm, width ≥ 600 mm) | 7409.19.00 | 7409.19 | 7409.19.1000 | 7409 19 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 C18150
| Element | Range (%) |
|---|---|
| Cr | 0.50 – 1.5 |
| Zr | 0.02 – 0.20 |
| Cu | balance (Cu + named elements ≥ 99.7) |
Mechanical properties
typical, bar solution treated, cold worked and aged (TL04, CDA)
| Property | Value |
|---|---|
| Tensile strength | ≈ 545 – 560 MPa |
| Yield strength (0.5%) | ≈ 515 – 545 MPa |
| Elongation | ≈ 14 – 16% |
| Hardness | ≈ 78 – 82 HRB |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.89 g/cm³ |
| Melting range | 1,070 – 1,080 °C |
| Modulus of elasticity | 117 GPa |
| Electrical conductivity | ≈ 80% IACS |
| Thermal conductivity (20 °C) | ≈ 324 W/m·K |
| Thermal expansion (20–100 °C) | 17.1 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Softening temperature in the ≈ 500 °C range*, higher than chromium copper; suitable for electrodes and conductive parts that run hot. |
| Heat treatment | Solution treatment at ≈ 980 – 1,010 °C with rapid cooling. Precipitation hardening at ≈ 425 – 500 °C for 2 – 4 h*. Hot working between ≈ 815 and 925 °C. |
| Welding | Brazing and soft soldering possible. Fusion welding cancels the hardening in the heated region; normally joined mechanically or by low-temperature brazing. |
| Machining | Low machinability, typical of high-conductivity copper (≈ 20, C36000 = 100)*. Sharp tool and positive rake angle; best in the aged condition. |
Typical applications
- Electrodes, caps and tips for spot welding (RWMA Class 2)
- Seam welding wheels and butt welding clamps
- Molds and continuous casting components
- Conductive components of welding machines and induction furnaces
- Mold inserts with high heat extraction
Alternatives: Chromium copper C18200 in less temperature-demanding applications; low-beryllium copper C17510 (RWMA Class 3) when more hardness with lower conductivity is needed.
Frequently asked questions
What is the chemical composition of Chromium-zirconium copper C18150?
Per CDA / UNS C18150: Cr 0.50 – 1.5; Zr 0.02 – 0.20; Cu balance (Cu + named elements ≥ 99.7).
Which standards cover Chromium-zirconium copper C18150?
Bar: EN 12163 (CW106C)*. Forging: EN 12420 (CW106C)*. Plate: EN 1652 (CW106C)*.
Up to what temperature can Chromium-zirconium copper C18150 be used?
Softening temperature in the ≈ 500 °C range*, higher than chromium copper; suitable for electrodes and conductive parts that run hot.
Which materials can replace Chromium-zirconium copper C18150?
Chromium copper C18200 in less temperature-demanding applications; low-beryllium copper C17510 (RWMA Class 3) when more hardness with lower conductivity is needed.
