OPERATION 6-12 Manual 0-5406
Description Possible Cause Remedy
5 A groove has been formed in the
base metal adjacent to the toe of a
weld and has not been filled by the
weld metal (undercut).
A Welding current is too high. A Reduce welding current
B Welding arc is too long. B Reduce the length of the
welding arc
C Angle of the electrode is
incorrect.
C Electrode should not be
inclined less than 45° to the
vertical face
D Joint preparation does not
allow correct electrode angle.
D Allow more room in joint
for manipulation of the
electrode.
E Electrode too large for joint. E Use smaller gauge electrode.
F Insufficient deposit time at
edge of weave.
F Pause for a moment at edge
of weave to allow weld metal
build-up.
Art # A-07714
Figure 6-31: Examples of undercut
6 Non-metallic particles are trapped in
the weld metal (slag inclusion)
A Non-metallic particles may
be trapped in undercut from
previous run
A If bad undercut is present,
clean slag out and cover
with a run from a smaller
diameter electrode
B Joint preparation too
restricted
B Allow for adequate
penetration and room for
cleaning out the slag
C Irregular deposits allow slag
to be trapped
C If very bad, chip or grind out
irregularities
D Lack of penetration with slag
trapped beneath weld bead
D Use smaller electrode with
sufficient current to give
adequate penetration. Use
suitable tools to remove all
slag from corners
E Rust or mill scale is
preventing full fusion
E Clean joint before welding
F Wrong electrode for position
in which welding is done
F Use electrodes designed for
position in which welding
is done, otherwise proper
control of slag is difficult
Not cleaned,
or incorrect
electrode
Slag
trapped in
undercut
Slag trapped in root
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