Unpulsed/pulsed TIG welding

Abstract

This chapter provides an overview of the pulsed and un-pulsed Tungsten Inert Gas (TIG) welding. In the un-pulsed TIG welding mode, the output current from the power source remains stable and only varies, as in both the modes, when the arc gap is increased or decreased. The advantages of pulsed Direct Current (DC), TIG are best realized when welding metals that readily melt and flow, such as stainless steels. The aim of pulsing is mainly to achieve maximum penetration without excessive heat build-up, by using the high current pulse to penetrate deeply and then allowing the weld pool to dissipate some of the heat during a proportionately longer arc period at a lower current. Pulsed TIG welding has a drawback in that it is slower than using unpulsed current but its great advantage is that heat build-up in the component is much reduced. Indeed, pulsed current is even used to weld end caps to seal the ends of small detonator cans after filling with explosive. Pulsed current also does not permit too much build-up of residual heat in circumferential or orbital welding especially where, at the end of a run, the weld seam overlaps the start.