Advanced Welding Processes: Technologies and Process Control

∑ no heavy slag – reduced post-weld cleaning;
∑ low hydrogen – reduces risk of cold cracking.
An introduction to welding processes 13
Gas nozzle
Contact tip
Shielding gas
Filler wire
Metal droplet
transfer
Arc
1.10 Gas metal arc welding (GMAW) or metal inert gas (MIG)
welding.
Depending on the operating mode of the process, it may be used at low
currents for thin sheet or positional welding.
The process is used for joining plain carbon steel sheet from 0.5 to
2.0 mm thick in the following applications: automobile bodies, exhaust systems,
storage tanks, tubular steel furniture, and heating and ventilating ducts. The
process is applied to positional welding of thicker plain carbon and low alloy
steels in the following areas: oil pipelines, marine structures and earth-moving
equipment. At higher currents, high deposition rates may be obtained and the
process is used for downhand and horizontal–vertical welds in a wide range
of materials. Applications include earth-moving equipment, structural steelwork
(e.g. I-beam prefabrication), weld surfacing with nickel or chromium alloys,
aluminium alloy cryogenic vessels and military vehicles.
Plasma welding {15}
In plasma welding, the heat generated by a constricted arc is used to fuse the
joint area, the arc being formed between the tip of a non-consumable electrode
and either the workpiece or the constricting nozzle (Fig. 1.11). A wide range
of shielding and cutting gases are used depending on the mode of operation