spatter and over heat the contact tip. Too long stick out will cause an unstable arc, lack of
penetration, lack of fusion and increase spatter.
Travel Speed
- Travel speed is the rate that the gun is moved along the weld joint and is usually
measured in mm per minute. Travel speeds can vary depending on conditions and the welders
skill and is limited to the welders ability to control the weld pool. Push technique allows faster
travel speeds than Drag technique. Gas flow must also correspond with the travel speed,
increasing with faster travel speed and decreasing with slower speed. Travel speed needs to match
the amperage and will decrease as the material thickness and amperage increase.
Too Fast Travel Speed
- A too fast travel speed produces too little heat per mm of travel resulting
in less penetration and reduced weld fusion, the weld bead solidifies very quickly trapping gases
inside the weld metal causing porosity. Undercutting of the base metal can also occur and an
unfilled groove in the base metal is created when the travel speed is too fast to allow molten metal
to flow into the weld crater created by the arc heat.
Too Slow Travel Speed
-
A too slow travel speed produces a large weld with lack of penetration
and fusion. The energy from the arc dwells on top of the weld pool rather than penetrating the
Normal stick out
Too short
Too long
Even arc, good
penetration even
fusion, good finis.
Unstable arc, spatter,
over heat contact tip.
Unstable arc, spatter,
poor penetration and
fusion.
Too Fast Travel Speed
high narrow bead
undercut
lack of fusion
lack of joint penetration
spatter
porosity
37
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