CuNi2Si
2.0855Nickel-silicon precipitation-hardened copper alloy combining high strength (UTS ~700 MPa aged) with good electrical conductivity (35–45% IACS) and excellent stress relaxation resistance at elevated temperatures. Lead-free and RoHS compliant — the modern replacement for CuBe2 in many connector applications where beryllium toxicity is a concern. Trade names: Wieland K55 (Wieland), C70250 (Olin Brass). Used for automotive high-current connectors, IC lead frames, relay springs, fuse clips and miniaturized electronic contacts.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | UNS | USA | C70250 | C70250 | REF |
| 🇪🇺 | EN | Europe | CW109C | — | 100% |
Sources: ASTM B534, EN 12163
Chemical composition comparison (wt%)
Side-by-side: CuNi2Si (EN) (EN 12163) vs CW109C (EN) (EN 12163)
| Element | CuNi2Si (EN) | CW109C (EN) | Overlap |
|---|---|---|---|
| Si | 0.4–0.8% | 0.4–0.8% | OK |
| Ni | 1.6–2.5% | 1.6–2.5% | OK |
| Cu | — | — | — |
| Mg | ≤ 0.3% | ≤ 0.3% | OK |
Mechanical properties
Solution annealed
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 300–380 | MPa |
Precipitation hardened
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 620–720 | MPa |
| Yield Strength Rp0.2 | 550–660 | MPa |
| Elongation A | 5–12 | % |
General
| Property | Value | Unit |
|---|---|---|
| Density | 8.81 | g/cm³ |
| Electrical Conductivity | 35–45 | % |
| Thermal Conductivity | 170–200 | W/mK |
Compatibility verdict
CuNi2Si and CW109C: 100% composition match
Close equivalents but NOT identical.
Related materials
CuZn37
2.0321Lead-free alpha/alpha+beta brass (63% Cu, 37% Zn). Compromise between cold formability (CuZn35) and hot formability (CuZn40). The most widely used unleaded brass. Used for cartridge cases, radiator cores, lamp components, plumbing fixtures, and decorative hardware.
CuZn36Pb3
CW603NFree-cutting leaded brass — the benchmark for non-ferrous machinability (rated 100%). Lead particles act as chip breakers for excellent surface finish. Used for screw machine parts, fittings, valves, watch components, precision mechanics, and electrical connectors. Old DIN number 2.0375.
CuSn6
CW452KPhosphor bronze with 6% tin — better cold formability than CuSn8 at slightly lower strength. Excellent spring properties and fatigue resistance. Used for electrical connectors, spring contacts, switch parts, bellows, bourdon tubes, and precision springs.
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