Page 42 - Welding Robots Technology, System Issues, and Applications

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Welding Technology

2.1 Gas Tungsten Arc Welding (GTAW)

The gas tungsten arc welding (GTAW) process is based on the electric arc
established between a non-consumable electrode of tungsten and the work-pieces
to be joined. Part of the heat generated by the electric arc is added to the work-
pieces, promoting the formation of a weld pool. The weld pool is protected from
air contamination by a stream of an inert gas (Ar or He) or a mixture of gases.

2.1.1 Introduction

This process is also known as tungsten inert gas (TIG), although small amounts of
non-inert gases may be used in the shielding mixture, such as hydrogen or
nitrogen. Figure 2.1 illustrates the principal elements of the conventional process.

Autogenous GTAW welding (without filler metal) is used in thin square edged
sections (2mm), while V and X type edge preparations are needed in thicker
sections. In this case, the addition of filler metal is necessary. This process is
extensively used for welding thin components of stainless steel, aluminum,
magnesium or titanium alloys as well pieces of carbon and low alloy steels [1],[2].

Heat input in GTAW does not depend on the filler material rate. Consequently, the
process allows a precise control of heat addiction and the production of superior
quality welds, with low distortion and free of spatter. It is less economical than
other consumable electrode arc welding processes, due to its lower deposition rate,
and it is sensitive to windy environment because of the difficulty in shielding the
weld pool. Besides it shows low tolerance to contaminants on filler or base metals.

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