Gas selection -
The purpose of the gas in the
MIG process is to protect / shield the wire,
the arc and the molten weld metal from the
atmosphere. Most metals when heated to a
molten state will re act with the air in the
atmosphere, without the protection of the
shielding gas the weld produced would contain
defects like porosity, lack of fusion and slag
inclusions. Addit ionally some of the gas
becomes ionised (electrically charged) and
helps the current flow smoothly.
The correct gas flow is also very important in
protecting the welding zone from the
atmosphere.
Argon Co2
CO2
Penetration Pattern for Steel
Too low flow will give inadequate coverage
and result in weld defects and unstable arc
conditions. Too high flow can cause air to be
drawn into the gas column and contaminate
the weld zone. Use the correct shielding
gas. CO2 is good for steel and offers good
penetration characteristics, the weld profile
is narrower and slightly more raised than the
weld profile obtained from Argon Co2
mixed gas. Argon CO2 mix gas offers better
weld ability for thin metals and has a wider
range of setting tolerance on the machine.
Argon 80% CO2 20% is a good all round
mix suitable for most applications.
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