2006 Volume 24 Issue 1 Pages 45-51
To know whether an arc plasma burns down into a keyhole during hybrid welding is very important in terms of the interpretation of welding phenomena and the production of deeper weld beads. In this paper, therefore, with the objective of understanding the existence level of the arc plasma in the keyhole during YAG laser-TIG arc hybrid welding, electric currents were measured by utilizing normal specimens and two different experimental samples of Type 304 stainless steel plates with simplified keyholes. In the lap- and butt-joint weld-type experiments, special samples consisting of the upper and lower plates of 2 mm in thickness were set with some gaps, and the currents flowing through respective plates were measured while the keyhole was formed in the lower plate during hybrid welding. It was confirmed in the lap-joint type weld experiment that the current flowing through the lower plate was not so high as it increased the penetration. And in the butt-joint type weld experiment, the current forced to pass through the lower plate decreased by the formation of laser-induced plume. It was consequently concluded that the arc was pinched around the keyhole inlet but did not burn down into the keyhole during hybrid welding.