1 Scope

This document concerns graphite-based grades that are used for sliding electrical contacts, such as carbon brushes or pantograph strips.

By extension, it is possible to apply the test procedures of this document to all electrical sliding contacts for electrical transmission appliances and to other appliances of graphite-based materials (heat exchangers, bearings, etc.).

This document specifies uniformized procedures for determining their following properties:

• density and porosity;

• resistivity;

• flexural strength;

• hardness;

• ash content.

In addition, it provides recommendations on test procedures for other properties:

• Mechanical properties: Charpy impact test, compressive strength, tensile strength (Annex B).

• Thermal properties: coefficient of thermal expansion, specific heat capacity, thermal conductivity (Annex C).

The properties determined by these tests are inherent to the graphite-based materials and it is therefore important to distinguish them from performance characteristics in operation on electrical equipment (carbon brush in an electrical rotating machine, contact strips on a pantograph, etc.).

Since these materials are generally brittle, porous materials, it is reasonable that their properties vary much more than the same properties in metals.

Some test methods are suitable for use in production quality control (routine tests), others only for more thorough investigations, using precise laboratory techniques (see Annex A).