Experimental study of single sided sheet to tube resistance spot welding

To reduce weight and improve performance, hydroformed tubes are being widely used in automotive structure fabrication and the single sided sheet to tube resistance spot welding ( SSRSW) is considered as a feasible method for joining a tube to other parts. However, in the sheet to tube SSRSW process, it is difficult to assure welding quality because of large welding deformation due to a lack of support inside the tube. The present paper investigates the influences of welding parameters, such as electrode force and welding current, on the welding deformation and quality of the sheet to tube SSRSW using electrode displacement and tensile shear tests. The effects of different electrode force patterns on the welding quality are investigated utilising the force characteristics of a servo gun. It is found that the welding deformation is influenced by both the electrode force and the welding current, and the tensile shear strength declines with larger electrode force and higher welding current. However, the tensile strength could be enhanced significantly and the welding deformation decreased greatly by reducing the electrode force in the welding stage or holding stage. In order to decrease manufacturing cost and improve weld quality, the reduced electrode force is recommended for the sheet to tube SSRSW process.