IACS stands for International Annealed Copper Standard. It sets the conductivity of annealed copper at 100%, and other metals are expressed as a percentage of that. High-purity EC grade aluminium reaches about 61-62% IACS. Because aluminium is roughly one third the density of copper, it carries more current per kilogram, which is why it dominates overhead power lines. Conductivity can also be stated as resistivity, which is its inverse.
Why it matters when buying
- For wire rod, conductors and bus bars, conductivity is an acceptance parameter; ask for measured values on the mill test certificate.
- Impurities such as titanium, vanadium, chromium and manganese, even at small levels, lower conductivity; check the chemistry as well.
- Alloying and temper change conductivity: 6201 alloy rod trades conductivity for strength, and cold work lowers it slightly.
- Eddy-current meters are also used to check temper and sort alloys non-destructively.
Typical uses
Acceptance testing of wire rod, AAC, AAAC and ACSR conductors, bus bars and winding strip. See wire and conductors and wire rod.