Advanced Welding Processes: Technologies and Process Control

6.1 Introduction
The gas tungsten arc welding (GTAW) process is well established as a highquality
fusion welding technique. Developments in the process have extended
the potential application range and offer improved process control.
6.2 Process developments
Some of the more significant process advances are described below and
further developments in the field of automation, computer control and adaptive
control are discussed in Chapter 11.
The basic process developments and the principles involved in the control
of the process will be discussed under the following headings:
∑ arc initiation and electrode development;
∑ pulsed GTAW and high-frequency pulsed GTAW;
∑ square-wave AC GTAW and plasma;
∑ cold- and hot-wire feed additions in GTAW;
∑ dual-gas GTAW and plasma welding;
∑ multicathode GTAW;
∑ A-TIG welding;
∑ buried arc GTAW;
∑ high current GTAW;
∑ control of GTAW and related processes.
6.2.1 Arc initiation and electrode development
Arc initiation in the GTAW process is a two-stage process consisting
of initial breakdown of the arc gap (stage I) and stabilization of the arc
(stage II).
Stage I is influenced by the electrode, the open-circuit voltage of the
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Advanced gas tungsten arc welding