Experimental study of laser welding with applied electrical potential

The objective of the present study is to develop laser welding with an appl ied voltage potential, to increase the weld bead root size in laser welding and thereby to improve the welding speed and the butt joint gap tolerance. The influences of the experimental conditions, namely, input laser power, applied voltage between plate and backside electrode, welding speed, plasma operating gaseous species (air, argon, or argon-helium), and the butt join t gap, on the plasma stability and the weld bead were investigated. The wel d beads were evaluated from the point of view of the bead appearance, the p enetration depth, the ratio of the widths of the weld bead root and weld be ad face, and the smoothness of the bead surface. It is found that to stabil ise the plasma, it is preferable to set the plate polarity as the cathode ( electrode positive), and to use argon or helium gas as a plasma operating g as. Also. it is concluded that this novel method is effective in increasing the bead root/face width ratio, and the melting area. Although it is neces sary to optimise the experimental conditions to avoid overheating and melti ng of the plates, the present method is applicable for higher speed and wid er gap but joint welding than in conventional laser welding.