Specific Electrical Contact Resistance of Copper in Resistance Welding

摘要

The electrical contact resistance (ECR) of copper (Cu-ETP R200, soft) contacts forresistance welding (RW) is characterized. ECR plays a major role in the RWprocess and provides local heat generation between the parts. A specialdetermination method is used on different testing variants to observe theinfluence of contact pressure (two levels: 68, 155 MPa), contact temperature(20–550 C), and surface parameters, like roughness or oxide layer thickness, onthe specific electrical contact resistance (SECR). For each surface parameter,three different levels are investigated. The study shows decreasing SECR withhigher mechanical load on the contact and a more complex behavior for increasein contact temperature. SECR shows a characteristic behavior for contact statesnear the temperature-dependent tensile strength of the base material for roughand clean surfaces, where SECR approaches toward zero. The variation of oxidelayer thickness and surface roughness has a strong influence on the resultingSECR and both surface parameters show a strong coupling regarding theireffects.