Abstract
This paper aims to develop a novel tungsten inner gas (TIG) welding torch in order to join thin sheets efficiently. Using a narrowing nozzle (constricted nozzle) inside a conventional TIG torch can critically improve the position accuracy of the tungsten electrode and also the arc plasma characteristics and heat input density. In order to evaluate the efficiency of this new torch, weld bead appearance and cross-section images were examined by an optical microscope, scanning electron microscope (SEM), and electron back scatter diffraction patterns (EBSD). The results showed that in all cases, the weld bead profile was stable without undercut and burn-through. Full penetration weld was seen. The width of weld bead on the bottom surface was increased much in comparison to conventional TIG welding. However, the results from SEM and EBSD images indicated that in the case of low welding current, the blowholes were found out on the side of the thinner material (SS400). The penetration of SUS430 material to SS400 material was not good. It seems that no fusion of SUS430 material to SS400 at the bottom surface can be seen. Meanwhile, no blowholes were seen in the case of high welding current. The penetration was better, and the fusion was reached on the bottom surface.
Highlights
Welding in the plat position is the easiest way to keep the arc stable, preventing a drop of molten metal before solidification
This paper indicated that thin sheets of 0.1 mm can be welded with sound quality at an extremely short distance of arc length (0.1 mm), high welding speed and low welding current with no surface defects such as undercut and burn-through [15]
It can be seen that the weld pool seems be extended in the downward direction due to the opposition of gravity force to the welding direction
Summary
Welding in the plat position is the easiest way to keep the arc stable, preventing a drop of molten metal before solidification. In automatically production lines, welding in this position is not always applied. Joints are required in the vertical position. For in welding in the vertical position, due to the critical influence of gravity force and the difficult set-up experimental process, no reports were found in the case of thin sheets. A few papers were published recently for joining thin plates by a micro-tungsten inner gas (TIG) welding process [1], micro-Plasma welding [2,3], and laser welding [4] in the plat position.
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