Investigation on Joining Process and Joining Parameter

Study of High-Current Density Resistance Spot Welding Process (2nd. Report)

Abstract

In the high-current density resistance spot welding process, the fusion layer at the interface of the joints is much thinner than one of the conventional spot welding process, the strength of the joints is sufficiently high, and its indentation is very small, and so the contact resistance at the interface is used efficiently to form nugget and the thermal loss is obstructed due to the pulsed high current density with very short duration.
As this joining process utilizes the contact resistance at the interface efficiently, the current path is main factor to be determined the joining area. The current path is mainly under the control of the electrode diameter, sheet thickness, electrode force, and current value. For obtaining the joints with sufficiently high strength, the current density in the current path among sheets must be larger than the certain value (2.0 kA/mm²). Furthermore, if the current density at the current path between electrode and sheet is larger than the certain value (2.6 kA/mm²), the electrode sticks on the sheet.
Thus, for obtaining the satisfactory joints with sufficiently high strength and without the electrode sticking on the sheet surface, the proper joining conditions exist under certain range of sheet thickness and electrode tip diameter for joining.