Abstract：Pulsed current tungsten inert gas (TIG) shielded arc welding is widely used in high quality welding. The arc characteristics, including the variations of the arc shape, gray-scale and temperature with the pulsed current, are studied here to understand the dynamic physical characteristics of pulsed TIG welding arcs, especially the welding stability and the control of the weld seam quality. The pulse current and corresponding arc images were acquired synchronously during the welding process. Image processing using the Fowler-Milne method was used to characterize the arc shape, gray-scale and temperatures at specific positions within the pulsed TIG welding arc to analyze their periodic variations. The experimental results show that the arc characteristic parameters at specific positions within the pulsed arc are synchronized with the current variations to within 0.1 ms. The arc expands and the arc temperature quickly rises as the current increases along the front edge of the pulse and then the arc contracts and the arc temperature falls as the current decreases. The arc temperature 1 mm below the tungsten electrode rises at a rate of 11 613 K/ms as the current increases and decreases at a rate of 5 710 K/ms as the current decreases. The arc gray-scale changes less closer to the tungsten electrode before and after the current changes, but the arc temperature changes are greater.
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