Tweco 95 S Thermal Arc(Jan2013) - Manual (Page 38)

THERMAL ARC 95 S SERVICE
Manual 0-5086 5-2 Service
5.02 STICK Welding Problems
Description Possible Cause Remedy
1. Gas pockets or voids in weld metal
(Porosity).
A. Electrodes are damp.
B. Welding current is too high.
C. Surface impurities such as oil,
grease, paint, etc.
A. Dry electrodes before use.
B. Reduce welding current.
C. Clean joint before welding
2. Crack occurring in weld metal soon
after solidification commences.
A. Rigidity of joint.
B. Insufficient throat thickness.
C. Cooling rate is too high.
A. Redesign to relieve weld joint of severe
stresses or use crack resistance
electrodes.
B. Travel slightly slower to allow greater
build up in throat.
C. Preheat plate and cool slowly.
3. A gap is left by failure of the weld
metal to fill the root of the weld.
A. Welding current is too low.
B. Electrode too large for joint.
C. Insufficient gap.
D. Incorrect sequence. A. Increase welding current
B. Use smaller diameter electrode.
C. Allow wider gap.
D. Use correct build-up sequence.
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 preheat
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.
5. Non-metallic particles are trapped
in the weld metal (slag inclusion).
Not cleaned,
or incorrect
electrode
Slag
trapped in
undercut
Slag trapped in root
Art # A-05868_AC
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.
Insufficient Gap
Incorrect Sequence
Art # A-05866_AC
Art # A-05867_AC Lack of
inter-run fusion
Lack of side fusion,
scale dirt, small electrode,
amperage too low
Lack of root fusion
Lack of fusion caused by dirt,
electrode angle incorrect,
rate of travel too high