Abstract
Developing a deep penetration TIG welding technique to produce welds of equal quality to the industrial standard practise of laser-based welding techniques has the potential to lower production complexity and cost. Higher currents levels are required to increase penetration depth in conventional TIG welding but this results in excessive weld bead width amongst other detrimental effects. However, through K-TIG and A-TIG techniques these detrimental effects can be circumnavigated. Prior experimental work on weld pool dynamics in conventional TIG welding in higher current regions has been sparse as TIG welding enhanced through novel techniques provides the best quality welds. This paper is an early feasibility study for novel deep penetration welding techniques motivated by observations made during research done at The University of Sheffield where unexpected activity in the weld pool was identified during TIG welding with a VBC IE500DHC between 300A – 1000A. This current range is labelled the ‘Red Region’. Understanding the fluid dynamics of the molten metal in the weld pool at the ‘ Red Region' current level will help in the creation of novel techniques for deep penetration TIG welding. Addressing this, this paper compares the quality of welds produced between 100A and 200A on 316 Stainless Steel by two industrially leading welding machines; the Miller Dynasty 350 and the VBCie 500DHC.
Highlights
Achieving consistent high quality deep penetration welds is a difficult but potentially highly profitable endeavour
Due to complex activity in the weld pool, deep penetration welding requires the use of specialised techniques to push the weld pool deeper into the work piece
A-TIG involves the addition of surfactants to the work piece to increase the surface tension in centre of the weld pool so that Marangoni convection pushes the weld pool deeper into the work piece
Summary
Achieving consistent high quality deep penetration welds is a difficult but potentially highly profitable endeavour. Due to complex activity in the weld pool, deep penetration welding requires the use of specialised techniques to push the weld pool deeper into the work piece. The prevailing industrial solutions of laser-based deep penetration techniques are expensive and cumbersome to transport. TIG welding often does not require considerable preparation of the work piece and through novel modification of TIG welding, a technique which manipulates weld pool dynamics to achieve deep penetration could be developed. TIG welding solutions for deep penetration require novel techniques to avoid the adverse effects of the large current required for deep penetration such as the bead width becoming excessively large. The Active flux TIG, or A-TIG, technique is a good demonstration of how the Marangoni effect can be manipulated to achieve deep weld penetration. The novel principle of K-TIG is to cool the weld torch by circulating water around it - this changes the shape of the arc such that a keyhole can be formed during welding
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