Tweco 300 TS Arcmaster(Feb2006) - Manual (Page 48)

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4 Portions of the weld
run do not fuse to the
surface of the metal
or edge of the joint.
A
B
Small electrodes used
on heavy cold plate.
Welding current is
too low.
A
B
Use larger electrodes and
pre-heat the plate.
Increase welding current.
C Wrong electrode angle. C Adjust angle so the welding arc is
directed more into the base metal.
D Travel speed of
electrode is too high.
D Reduce travel speed of electrode.
E Scale or dirt on
joint surface.
E Clean surface before welding.
Figure 9. Example of Lack of Fusion
5 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.
Figure 10. Examples of Slag Inclusion