MetFab - Welding Fume Handbook - Flipbook - Page 37
10 Effect of shielding gas: carbon monoxide
Figure 30 shows that for the same level of carbon dioxide,
carbon monoxide emissions were lower when the shielding
gas contained a small amount of oxygen.
Welding with spray transfer generates more carbon dioxide
than welding with dip transfer.
FCAW
The emission rate of carbon dioxide in FCAW is higher than
for MAG welding.
Figure 31 shows carbon monoxide emission rates with a
selection of common shielding gases for FCAW of mild steel.
Carbon dioxide creates the highest emissions of carbon
monoxide, but the argon/helium mixture containing 15%
carbon dioxide generates more carbon monoxide than an
argon/20% carbon dioxide mixture.
10
I
8
I
9.7
5.9
6
4
I
2
I
6.1
I
CO emission rate ml/s
Thus, the presence of helium in the formulation appears to
raise the carbon monoxide emission rate, but the levels of
carbon monoxide generated are not considered significant.
0
35% Ar/50% He/15%CO
80% Ar/20%CO
CO
shielding gas
Figure 31: The effect of shielding gas on carbon monoxide emission
rate during FCAW of mild steel
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