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4 Portions of the
weld run do not
fuse to the surface
of the metal or
edge of the joint.
5 Non-metallic parti-
cles are trapped in
the weld metal
(slag inclusion).
A
Small electrodes used on
heavy cold plate.
B
Welding current is too low.
C Wrong electrode angle.
D Travel speed of electrode is
too high.
E Scale or dirt on joint surface. E Clean surface before welding.
Figure 9 – Example of lack of fusion
A Non-metallic particles may
be trapped in undercut from
previous run.
B Joint preparation too
restricted.
C Irregular deposits allow slag
to be trapped.
D Lack of penetration with slag
trapped beneath weld bead.
E Rust or mill scale is
preventing full fusion.
F Wrong electrode for position
in which welding is done.
Figure 10 – Examples of slag inclusion
43
A
Use larger electrodes and pre-
heat the plate.
B
Increase welding current
C Adjust angle so the welding
arc is directed more into the
base metal
D Reduce travel speed of
electrode
A If bad undercut is present,
clean slag out and cover with a
run from a smaller diameter
electrode.
B Allow for adequate
penetration and room for
cleaning out the slag.
C If very bad, chip or grind out
irregularities.
D Use smaller electrode with
sufficient current to give
adequate penetration. Use
suitable tools to remove all
slag from corners.
E Clean joint before welding.
F Use electrodes designed for
position in which welding is
done, otherwise proper control
of slag is difficult.
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