MetFab - Welding Fume Handbook - Flipbook - Page 42
12 Recommended gases
The choice of shielding gas should be based primarily on
its welding performance, but consideration should also be
given to its impact on the working environment. This section
summarises the results of detailed trials evaluating both the
welding performance and emission rates of fume of different
shielding gases.
12.1 Mild steel welding
Environmental
MIG
Welding with carbon dioxide as the
shielding gas generates the most
particulate fume, but the particulate
fume emission rates with all other
mixtures tested are very similar.
Ferromaxx® Plus is the optimum gas for
welding all thicknesses of carbon steels
and is particularly beneficial when
high deposition rates are required.
Ferromaxx® 7 is recommended for
welding thinner plate materials and
Ferromaxx® 15 for thick plate.
Environmental
None of the shielding gases used
commonly for welding mild steel offer
any significant advantage in reducing
particulate fume emission rates.
However, ozone may be generated in
significant quantities relative to its
exposure limit. Ferromaxx® Plus or
Ferromaxx® 15 is recommended when
exposure to ozone presents a problem.
The generation rate of carbon monoxide
increases with the carbon dioxide
content of the shielding gas, but it is
not expected that exposure to carbon
monoxide will present a problem
when welding with any gas from the
Ferromaxx® range.
FCAW
80% argon/20% CO, is the
recommended gas mixture for all
applications.
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That said, the difference between the
fume emission rates for carbon dioxide
and the other gases is not expected to
change any fume control measures
required, so there is no preferred gas in
terms of particulate fume reduction.
Exposure to ozone is low, and similar for
each of the shielding gases tested.
Welding with carbon dioxide generates
the most carbon monoxide, but it is not
anticipated that exposure to carbon
monoxide will present a problem.
As a result, there is no preferred
shielding gas in terms of reducing fume
or gas emissions.
