MetFab - Welding Fume Handbook - Flipbook - Page 22
8 Effect of shielding gas: particulate fume
FCAW
10
I
8
I
9.2
6
I
4
I
2
I
Fume emission rate mg/s
Figure 11 shows the effect of shielding gas on fume emission rate
for FCAW of mild steel.
5.9
5.5
0
35% Ar/50% He
15% CO
80% Ar/20% CO
CO
Figure 11:The effect of shielding gas formulation on fume
emission rate during pulsed MAG welding of mild steel
Shielding with pure carbon dioxide generates significantly
more fume than an argon/20%CO mixture, confirming the
effect of higher concentrations of carbon dioxide. Helium
additions also increase fume emission, because a shielding
gas containing 15% carbon dioxide plus 50% helium in
argon generates fume at approximately the same rate as
the formulation containing 20% carbon dioxide in argon.
However, the differences in particulate fume emission
rate between the two gas mixtures were too small to be
significant when choosing a shielding gas.
8.2 Stainless steel welding MAG
Shielding gases for stainless steel MAG welding are usually
argon/helium mixtures with small additions of active gases
such as carbon dioxide or oxygen. Figure 12 shows the effect
of a range of gases on particulate fume emission rate when
dip transfer MAG welding stainless steel.
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