Advanced Welding Processes: Technologies and Process Control

High-energy density processes 155
adequate protective screening must be provided. It is also necessary for
appropriate eye protection to be worn when performing alignment and
monitoring of the process. Other hazards that must be considered are common
to other welding processes and these include fume and electrocution.
8.3.7 Developments
Laser-enhanced GTAW and GTAW augmented laser welding
The use of a TIG arc to heat and pre-melt the plate combined with a laser to
increase penetration and/or welding speed has been investigated by several
workers. [171, 172] It has been shown that using a 300 A GTAW arc to
augment the 1 kW laser may produce equivalent welding performance to a
2 kW laser device and, clearly, there is potential for extending the range of
low-power lasers by this technique. The laser also assists in preventing humping
of GTAW welds made at high current and high speeds. Comparisons with
multicathode GTAW (see Chapter 6) have not been made, but it is likely that
similar results could be achieved with this lower-cost process option.
Laser hybrid welding
More recently, combinations of laser and GMAW welding have been developed
and applied in such diverse applications as automotive fabrication and
shipbuilding. The process, which has become known as ‘Hybrid Laser GMAW’
offers increased speed and penetration compared with GMAW and improved
tolerance to fit-up when compared with laser welding. The use of the laser
tends to stabilise the arc root of the arc process and reduces arc ignition
problems. Although systems comprising individual laser and GMAW heads
have been used, commercial laser hybrid heads are now available.
Multiple laser operation
In the case of Nd:YAG lasers a novel system has been devised [168] in which
three 400 W lasers are brought to a common output housing by means of
fibre optic beam delivery systems. The three lasers may be pulsed in phase
to produce the maximum peak output or phaseshifted to give improved control
and higher welding speeds.
Laser development
Several alternative laser systems are available and improvements in efficiency
both in laser generation and application are being developed. Some of the
most interesting development areas are: