Gas Tungsten Arc Welding

GTAW (gas tungsten arc welding), commonly referred to as “TIG” welding, utilizes a nonconsumable tungsten electrode and separate filler metal in the form of wire (separate filler metal is not always used for very thin sections). Inert shielding gas is supplied through an annular nozzle around the tungsten electrode. The process is much better suited for shop fabrication than field fabrication since air movement must be less than 5 mph to maintain the inert gas blanket. (See Figure 600-10.)

GTAW is predominantly a manual process, but automatic processes have been developed. The automatic GTAW processes, however, are used primarily for high quality pipe and tube welding.

The manual GTAW process has specific, but limited, applications for pressure vessel fabrication. This process is preferred for root passes of welds which cannot be backwelded, such as vessel-closure welds or welds on small diameter sections. It is also sometimes used for welding very thin stainless steel parts like vessel internals. This process can be used for all positions, but welding confined joints may not be feasible because GTAW requires both of the welder’s hands. The manual GTAW process is also slow, and typically not economically attractive for thick welds or filler passes due to low deposition rates.

Equipment for Gas Tungsten Arc Welding

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