The weld metal deposited using the GMAW process is generally cleaner (fewer non-metallic inclusions)
and in the case of high strength structural steels, weld metal with superior toughness can be obtained
with proper selection of shielding gas (Ar-5% to 15% CO2). Such applications include girth welding of
large diameter natural gas and oil pipelines, submarine hulls, etc. The “low hydrogen” nature of the
process is an additional important characteristic, especially for welding of high strength steels.
One of the main limitations of the gas metal arc welding process is its sensitivity to the welding
parameters. Seemingly small changes in voltage, electrode extension, etc. can have a significant
influence on the bead shape and penetration, and thus on the incidence of weld flaws such as
incomplete fusion. Faithful reproduction of qualified welding procedures is therefore critical to obtain
sound production welds. In this regard, matching wire feed speed between the qualification procedure
and production situation is a good indicator that the correct procedure has been implemented. One
must also be aware that air drafts can reduce the effectiveness of the shielding medium causing
porosity in the weld metal.