Introduction
This article explains ASTM B75 C11000 electrolytic tough pitch copper tube. C11000 electrolytic tough pitch copper, also written Cu-ETP, is the most widely used electrical copper grade. It combines a copper minimum of 99.90 percent with high conductivity and moderate cost, which makes it the default material for conductors, bus bars, terminals and heat exchange components where brazing is not required.
Composition and Structure
ETP copper is refined electrolytically and cast with a controlled oxygen content of about 0.02 to 0.04 percent. The oxygen is present as cuprous oxide particles dispersed in the copper matrix. These particles do not reduce electrical performance, but they do define the material's limits: under reducing atmospheres at high temperature, hydrogen can diffuse in and react with the oxide to form internal steam, causing porosity and cracking known as hydrogen embrittlement.
Properties
C11000 reaches at least 101 percent IACS conductivity when annealed, with a thermal conductivity near 388 W/(m·K) and tensile strength from 200 to 260 MPa in the annealed condition. It work-hardens readily, so cold-worked tempers such as half-hard and hard give higher strength with reduced ductility, which is useful for spring contacts and connectors.
| Property | Typical Value | Note |
|---|---|---|
| Copper | 99.90% min | With controlled oxygen |
| Oxygen | 0.02 - 0.04% | Cuprous oxide particles |
| Conductivity | 101% IACS min | Annealed |
| Thermal conductivity | About 388 W/(m·K) | Heat exchange duty |
Applications and Limits
ETP copper is used for electrical conductors, bus bars, switchgear, transformer windings, terminals, heat sinks and general sheet, strip, rod and tube products. It is the standard material for mechanically joined or soft-soldered electrical connections. For assemblies that must be torch-brazed, welded or bright-annealed in hydrogen, a phosphorus-deoxidized or oxygen-free grade should be selected instead.
Selection and Verification
Specify the temper, dimensions and surface condition against standards such as ASTM B75 for tube, B152 for sheet and strip, B187 for bar and B49 for rod. Confirm conductivity, oxygen level and tensile properties on the mill certificate, and check that the delivered temper matches the forming and joining process.
