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15
ACCESSORIES
7.2 MMA WELDInG PROBLEMS
Description
Possible cause
Remedy
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
Crack occurring
in weld metal
soon after so-
lidification.
(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.
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
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.
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. adequate
penetration. Use suitable
tools to remove all slag
from corners
(f) Use electrodes
designed for position in
which welding is done,
otherwise proper control
of slag is difficult.
7.3 TIG WELDInG PROBLEMS
Weld quality is dependent on the selection of the correct
consumables, maintenance of equipment and proper welding
technique.
Description
possible Cause
Remedy
Excessive bead
build up or poor
penetration or
poor fusion at
edges of weld
Welding current is too
low
Increase weld
current and/or faulty
joint preparation
Weld bead too
wide and flat
or undercut at
edges of weld
or excessive
burn through
Welding current is too
high
Decrease weld
current
Weld bead
too small or
insufficient
penetration or
ripples in bead
are widely
spaced apart
Travel speed too fast
Reduce travel speed
Weld bead
too wide or
excessive
bead build up
or excessive
penetration in
butt joint
Travel speed too slow
Increase travel
speed
Uneven leg
length in fillet
joint
Wrong placement of
filler rod
Re-position filler rod
Electrode melts
when arc is
struck
Electrode is connected
to the ‘+’ terminal
Connect the
electrode to the
‘-’ terminal
Dirty weld pool
(a) Electrode
contaminated through
contact with work piece
or filler rod material
(b) Gas contaminated
with air
(a) Clean the elec-
trode by grinding off
the contaminates
(b) Check gas lines
for cuts and loose
fitting or change gas
cylinder
Electrode melts
or oxidizes
when an arc is
struck
(a) No gas flowing to
welding region
(b) Torch is clogged with
dust
(c) Gas hose is cut
(d) Gas passage
contains impurities
(e) Gas regulator is
turned off
(f) Torch valve is turned
off
(g) The electrode is too
small for the welding
current
(a) Check the gas
lines for kinks or
breaks and gas
cylinder contents
(b) Clean torch
(c) Replace gas
hose
(d) Disconnect gas
hose from torch
then raise gas
pressure to blow
out impurities.
(e) Turn on
(f) Turn on
(g) Increase
electrode diameter
or reduce the
welding current
Poor weld finish
Inadequate shielding
gas
Increase gas flow or
check gas line for
gas flow problems
