Minimising electrode wear in resistance spot welding of aluminium alloys

Abstract

Rapid electrode wear due to localised random alloying between copper and aluminium at high temperature is by far the greatest challenge for the resistance spot welding of aluminium alloys. An effective recourse would be to enhance the overall electrical conductivity along the electrode/sheet interface to reduce the resistive heating of copper electrode and to prohibit direct contact between electrode and sheet during welding. We propose here the application of carbon black paste in fluidic form as a barrier along the electrode/sheet interface both for the enhancement of electrical conductivity and for the prohibition of direct electrode to sheet contact. Carbon black is chemically inert to both copper and aluminium and in fluidic form allows the enhancement of thermal and electrical conductance due to better conformability within a pressurised contact. The present experimental study has shown a significant enhancement in electrode life in the presence of the carbon black based barrier coating along the interface.