MetFab - Welding Fume Handbook - Flipbook - Page 19
7 Emission Rates: general factors
In MIG/MAG welding the relationship is more complex
because changes in current and voltage induce changes in
the mode of metal transfer. In general, dip transfer creates
relatively low levels of particulate and gaseous fume.
Globular transfer gives slightly higher emission rates. In spray
transfer, emission rates are low at low current but increase
rapidly as the current rises. At similar average values for
current and voltage, pulsed transfer tends to generate less
fume than spray transfer (Figure 7).
4.4
6
I
3
I
Fume emission rate mg/s
9.2
I
9
12.2
I
12
13.5
I
15
4.4
DIP
6.9
SPRAY
6.2
5.0
4.2
PULSED
92% Ar/
8% CO
DIP
SPRAY
93% Ar/5% CO/2% O
SPRAY
Ferromaxx® Plus
DIP
SPRAY
Ferromaxx® 15
Figure 7:The effect of metal transfer mode on fume emission rate during
MAG welding of mild steel
Shielding gas composition
As a general rule, particulate fume emission rate tends to
increase with higher concentrations of active components
(oxygen and carbon dioxide) or helium in the shielding
gas. This is not always the case, however, and the following
sections provide detailed information on the effects of named
gases used with specific materials.
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