Spot Welding Electrode Structure for Expulsion-Free Large Nuggets

The patent applies multi-stage welding current control with different current values and durations in sequential stages. The first stage uses a higher current to rapidly heat and form the initial nugget, while subsequent stages use reduced current to complete the welding without causing expulsion. This periodic variation in welding parameters enables stable welding of high-tensile steel sheets by preventing the expulsion phenomenon that occurs with constant high current application.

The patent implements a multi-stage welding current control method where the welding current is divided into multiple stages with different current values and durations. The first stage applies a higher current to rapidly generate heat and form the nugget core, while subsequent stages reduce the current to prevent excessive heat generation and expulsion. This periodic action enables the formation of sufficiently large nugget diameters for fracture suppression without triggering expulsion in high-tensile steel sheets.

The patent employs multi-stage welding current control that divides the welding process into sequential stages with varying current intensities. The initial stage uses elevated current to rapidly heat the steel sheets and form the nugget core, achieving sufficient nugget diameter growth. Subsequent stages reduce the current to maintain heat input within safe limits, preventing expulsion while completing the welding process. This periodic modulation of current enables controlled nugget diameter enlargement without harmful expulsion effects.