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24
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 ow 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 mate-
rial thickness and amperage increase.
Too Slow Travel Speed - A too slow travel speed produces a large weld with lack of penetration and fu-
sion. The energy from the arc dwells on top of the weld pool rather than penetrating the base metal.
This produces a wider weld bead with more deposited weld metal per mm than is required resulting in a
weld deposit of poor quality.
cold lap
lack of fusion
lack of joint penetration
porosity
large wide bead
Too Slow Travel Speed
Correct Travel Speed - The correct travel speed keeps the arc at the leading edge of the weld pool allow-
ing the base metal to melt suciently to create good penetration, fusion and wetting out of the weld
pool producing a weld deposit of good quality.
good toe fusion
good penetration
good side wall fusion
even shaped bead
Correct Travel Speed
spatter
undercut
lack of joint penetration
lack of fusion
porosity
high narrow bead
Too Fast Travel Speed
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 solidies very quickly trapping gases inside the
weld metal causing porosity. Undercutting of the base metal can also occur and an unlled groove in the
base metal is created when the travel speed is too fast to allow molten metal to ow into the weld crater
created by the arc heat.
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