12
Argon-Nitrogen
Small amounts of nitrogen have been
added to Ar-1% 02 to achieve a completely
austenitic microstructure in welds
made with type 347 stainless steel filler metal. Nitrogen concentrations in the
range of 1.5 to 3% have been
used. Quantities above 10% produced considerable fuming
but welds are sound. Additions greater than
2% N2 produced porosity in single pass
GMAW welds made in mild steel; additions less than 1/2%
caused porosity in multipass GMAW welds
in carbon steel. A few attempts have been made to utilize N2
rich argon mixtures
for GMAW welding of copper and its alloys, but spatter percentage is high.
Argon-Chlorine
Chlorine is sometimes bubbled through
molten aluminum to remove hydrogen from ingots or castings. Since
this degassing operation is successful
it follows that chlorine might remove hydrogen from aluminum weld
metal. Some claims were made that Ar-C12
mixtures eliminated porosity in GMAW but fabricators have not
been able to achieve consistent results.
Moreover, since chlorine gas forms chloric acid in the respiratory
system, such mixtures can be disagreeable
or noxious to operators and those in the vicinity of welding.
Consequently, Ar-C12
mixtures are not popular or recommended except in special cases where adequate
safety and control is implemented.
