Abstract
A systematic experiment was performed for four types of welding circuit with different circuit inductances and a common welding coil, where each circuit inductance is given by the sum of a different remaining inductance and a common effective inductance. It was demonstrated that increasing the circuit inductance causes adverse effects on the discharge current, resulting in a long first collision time and a low deformation velocity of the moving sheet. When the circuit inductance increases from 0.0587 μH to 0.2280 μH, the maximum current decreases from 223 kA to 132 kA at a discharge energy of 2.0 kJ. With the decrease in discharge current, the deformation velocity of the sheet decreases from 383 m∙s-1 to 164 m∙s-1. The higher the circuit inductance is, the lower the deformation velocity of the sheet is. With the lower velocity, the shearing load of the resulting welded sheet further decreases, ultimately leading to joining failure. However, in the circuit with a minimum inductance of 0.0587 μH, it is possible to weld an aluminum alloy sheet to a 1 GPa class high-strength steel sheet. It has been clarified that the decrease in circuit inductance improves the joining property of a welded sheet.
