www.parweld.co.uk
7.0 Fault Finding
MMa welding problem
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
solidification.
(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
Description
Possible cause
Remedy
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.
F
aul
t
FI
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DIn
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