EN
What Is C18070 Copper Strip? Composition, Standards and Why Its Conductivity Matters
As vehicles electrify and solar installations scale up, one requirement keeps appearing on connector drawings: carry a large current, stay cool, survive heat over years, and still be formable into a complex shape. Ordinary copper conducts well but is too soft; most high-strength alloys give up too much conductivity. C18070 is one of the few strip alloys that holds both ends at once. This article explains what it is, how it is designated, and why its conductivity is the headline property.
A precipitation-hardened copper-chromium-silicon-titanium alloy
C18070 is a high-copper alloy — over 99% copper — with small additions of chromium, silicon and titanium. During aging, chromium and the silicon/titanium form fine precipitates that strengthen the metal while leaving the copper matrix clean enough to keep conducting. Because so little is dissolved in the copper, conductivity stays high; because the precipitates are stable, strength and spring force survive at temperature. It belongs to the copper-chromium family and is commonly written CuCrSiTi.
The design intent is a deliberate balance rather than a single peak property: high conductivity, medium strength, good bendability and stable behaviour when hot, all in one strip.
Cross-standard designations
The same alloy appears under several naming systems. When comparing quotations from different regions, these refer to the same material:
Standard |
Designation |
Specification |
Region |
UNS / ASTM |
C18070 |
ASTM B (high-copper) |
North America |
EN |
CuCrSiTi |
EN 1652 / EN 1654 |
Europe |
GB/T |
TCr0.3-0.2-0.05 |
GB/T |
China |
C18070 is often specified as a more economical alternative to C18080, a silver-bearing copper-chromium alloy in the same performance class. For many high-current connector parts C18070 delivers the conductivity and relaxation behaviour the design needs without the added alloying, which is a large part of its appeal.
Chemical composition
Composition in weight percent:
Element |
Content (%) |
Function |
Cu |
99.0 |
Base metal — conductivity |
Cr |
0.15 – 0.40 |
Precipitation strengthening |
Si |
0.02 – 0.07 |
Works with Cr/Ti to form precipitates |
Ti |
0.01 – 0.40 |
Refines precipitates, aids softening resistance |
Others |
≤ 0.1 |
Impurity limit |
The very high copper content is the reason the alloy conducts so well. The chromium, silicon and titanium together contribute less than one percent by weight, yet through precipitation they raise strength and high-temperature stability far beyond what pure copper offers.
Physical properties at a glance
Property |
Metric |
Imperial |
Density |
8.9 g/cm³ |
0.322 lb/in³ |
Electrical conductivity |
78 – 83% IACS |
78 – 83% IACS |
Thermal conductivity |
approx. 310 W/(m·K) |
approx. 179 Btu/(ft·h·°F) |
Modulus of elasticity |
138 GPa |
20,000 ksi |
Thermal expansion |
18 × 10⁻⁶ /K |
10.0 × 10⁻⁶ /°F |
The figure to note is conductivity of 78–83% IACS in the aged condition. That is close to pure copper and far above the 35–40% IACS of a high-strength spring alloy such as C70250. High conductivity means less resistive heating when a large current passes, which is exactly what a battery or PV connector needs. The full property set by temper is covered in the next article.
Where it is not the right choice
Being clear about the limits saves more money than promoting the strengths:
- Maximum spring force in a compact contact — a beryllium-free spring alloy such as C70250 reaches higher strength if conductivity is secondary.
- Pure busbar duty with no forming or heat requirement — plain C11000 copper is more economical.
- Applications where the very highest conductivity plus silver-level performance is specified — C18080 is the higher-alloyed option.
Shanghai Xinye Metal Material has produced copper and copper alloy strip since 2009 and supplies customers in around 30 countries; for a high-current connector that also has to be formed and run hot, sending the part drawing is usually the quickest way to have the temper matched to the duty.
Frequently asked questions
Is C18070 the same as CuCrSiTi?
Yes. CuCrSiTi is the European chemical designation for the same alloy that UNS lists as C18070 and GB lists as TCr0.3-0.2-0.05.
What is the conductivity of C18070?
Around 78–83% IACS in the aged condition — close to pure copper, and high for an alloy with this strength and heat stability.
How does C18070 compare with C18080?
They sit in the same performance class. C18080 is a silver-bearing variant; C18070 is often chosen as the more economical option when its properties already meet the requirement.
Next in this series: C18070 Properties — conductivity, strength, bendability, and the two high-temperature behaviours that must not be confused.
Related: High Performance Copper Alloy range · Contact us for a specification review