Tweco 400 MSTP Arcmaster - Manual (Page 65)

59
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