Tweco 400 MST Arc Master - Manual (Page 32)

400MST
6
BASIC TROUBLE SHOOTING
6 – 5
Figure 6-2: Example of lack of fusion
Figure 6-3: Examples of slag inclusion
Description Possible Cause Remedy
4 Portions of the weld run
do not fuse to the
surface of the metal or
edge of the joint.
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.
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.
E Clean surface before welding.
Description Possible Cause Remedy
5 Non-metallic particles
are trapped in the weld
metal (slag inclusion).
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.
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.
Lack of Root Fusion
Lack of inter-run Fusion
Lack of fusion caused by dirt,
electrode angle incorrect, rate
of travel too high
Lack of side fusion, scale
dirt, small electrode,
amperage too low
Not cleaned, or
incorrect electrode
Slag trapped in
undercut
Slag trapped in root