Selco Genesis 2700 PMC Instrucciones De Uso página 57

SELECTION GUIDE OF WELDING PARAMETERS WITH REFERENCE TO THE MOST TYPICAL APPLICATIONS AND MOST
COMMONLY USED WIRES.
Wire diameter - weight per metre
Voltage
arc (v)
Low penetration for thin
16 - 22
SHORT - ARC
24 - 28
GLOBULAR-ARC
(transition area)
30 - 45
SPRAY - ARC
Gases
MIG-MAG welding is defined mainly by the type of gas used: inert for MIG welding (Metal Inert Gas), active for MAG welding
(Metal Active Gas).
- Carbon dioxide (CO 2 )
Using CO2 as a shielding gas, high penetrations and low operating cost are obtained with high feeding speed and good mechani-
cal properties. On the other hand, the use of this gas creates considerable problems with the final chemical composition of the
joints as there is a loss of easily oxidisable elements with simultaneous enrichment of carbon in the weld pool.
Welding with pure CO 2 also creates other types of problems such as excessive spatter and the formation of carbon monoxide
porosity.
- Argon
This inert gas is used pure in the welding of light alloys whereas, in chrome-nickel stainless steel welding, it is preferable using
argon with the addition of oxygen and CO 2 in a percentage of 2% as this contributes to the stability of the arc and improves the
form of the bead.
- Helium
This gas is used as an alternative to argon and permits greater penetration (on thick material) and faster wire feeding.
- Argon-Helium mixture
Provides a more stable arc than pure helium, and greater penetration and travel speed than argon.
- Argon-CO 2 and Argon-CO 2 -Oxygen mixture
These mixtures are used in the welding of ferrous materials especially in SHORT-ARC operating mode as they improve the specific
heat contribution. They can also be used in SPRAY-ARC. Normally the mixture contains a percentage of CO 2 ranging from 8% to
20% and O 2 around 5%.
0,8 mm
Good penetration and
materials
60 - 160 A
Automatic fillet welding Automatic welding
150 - 250 A
Low penetration with Automatic welding
adjustment to 200 A
150 - 250 A
1,0-1,2 mm 1,6 mm
Good flat and vertical
melting control
100 - 175 A
120 - 180 A
Automatic welding
with high voltage
200 - 300 A 250 - 350 A
Good penetration
with multiple runs
200 - 350 A 300 - 500 A
2,4 mm
Not used
melting
150 - 200 A
Not used
downwards
300 - 400 A
Good penetration, high
downwards deposit on thick materials
500 - 750 A
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