Tweco 300 MST Arcmaster - Manual (Page 49)

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9.04 Stick Welding Problems
Description Possible Cause Remedy
1 Gas pockets or voids in
weld metal (Porosity).
A
B
C
Electrodes are damp.
Welding current is too high.
Surface impurities such as oil,
grease, paint, etc.
A
B
C
Dry electrodes before use.
Reduce welding current.
Clean joint before welding.
2 Crack occurring in weld
metal soon after
solidification
commences.
A
B
C
Rigidity of joint.
Insufficient throat thickness.
Cooling rate is too high. A
B
C
Redesign to relieve weld joint of
severe stresses or use crack
resistance electrodes.
Travel slightly slower to allow greater
build up in throat.
Preheat plate and cool slowly.
3 A gap is left by failure of
the weld metal to fill the
root of the weld.
A
B
C
Welding current is too low.
Electrode too large for joint.
Insufficient gap. A
B
C
Increase welding current
Use smaller diameter
electrode.
Allow wider gap.
D Incorrect sequence. D Use correct build-up sequence.
Figure 9. Example of Insufficient Gap or Incorrect Sequence
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 10. Example of Lack of Fusion