Study On Joint Forming And Electrode Failure Of Resistance Spot Welding Of 5083 Aluminum Alloy

With the rapid development of transportation industry,aluminum alloy resistance spot welding is widely used in the production of automobile automation as well as railway vehicle.However,there are two mainly problems in the process of aluminum alloy resistance spot welding,which are electrode wearing quickly and spot weld nucleation quality instability.These problems lead to frequent electrode replacement and instability welding spot molding,which affects the production efficiency and welding quality.Therefore,it is very important to study the aluminum alloy electrode failure and welding forming during spot welding.In this paper,CrZrCu alloy and alumina dispersion copper were used as spot welding electrodes.The welding spot forming,state of electrode and workpiece,current voltage during continuous spot welding of aluminum alloy were studied and analyzed by metallographic microscope,scanning electron microscope,EDS and oscilloscope.The mechanism of electrode failure and nucleation were discussed during continuous spot welding of aluminum alloy.Results showed that the electrode life of CrZrCu alloy was about 102,while that of alumina dispersion copper was about 151,which increased by 50%.Because the softening temperature of alumina dispersion copper was higher than that of CrZrCu alloy.The failure of the electrode was mainly caused by plastic deformation of the electrode and pitting corrosion on the electrode surface.The failure mechanism of the electrode was that the electrode was subjected to heat and force in continuous spot welding,the plastic deformation of the electrode end face increased,and the current density reduced between workpieces.At the same time,eutectic reaction occurred between the electrode and the workpiece under the action of resistance heat,and the alloying product increased the resistance value of the contact surface of workpiece.The increasing of heat production led to the increasing of nucleation and thickness between the electrode and the workpiece during welding.When the nucleation thickness was thickened to full penetration,the workpiece adhered to the electrode causing pitting corrosion,which indirectly affected the pressure on the workpiece and the contact resistance between workpieces.Therefore,the combined action of pitting corrosion and end face diameter reduced the resistance heat between workpieces that led to electrode failure.Due to the pitting corrosion of the electrode,the surface of the workpiece was not good during spot welding,and nucleation first increased and then decreased with the increasing of number of solder joints,which was caused by the interaction of the contact resistance between workpieces and between the electrode and the workpiece.