Parweld XTI-201 - MMA Welding Problems

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11
7.0 Fault Finding
MMA welding problem
Descripon Possible cause Remedy
Gas pockets
or voids in
weld metal
(porosity)
(a) Electrodes
are damp
(b) Welding
current is too
high.
(c) Surface
impuries such
as oil, grease,
paint, etc
(a) Dry electrodes
before use
(b) Reduce
welding current
(c) Clean joint
before welding
Crack occur-
ring in weld
metal soon
aer solidi-
caon.
(a) Rigidity of
joint.
(b) Insucient
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 le
by failure
of the weld
metal to ll
the root of
the weld
(a) Welding
current is too
low.
(b) Electrode too
large for joint.
(c) Insucient
gap
(d) Incorrect
sequence
(a) Increase
welding current
(b) Use smaller
diameter
electrode.
(c) Allow wider
gap
(d) Use correct
build-up sequence
FAULT
FINDING
Descripon Possible cause Remedy
Porons 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
parcles
are trapped
in the weld
metal (slag
inclusion).
a) Non-metallic
parcles may
be trapped in
undercut from
previous run
(b) Joint
preparaon too
restricted
(c) Irregular
deposits allow
slag to be
trapped.
(d) Lack of
penetraon with
slag trapped
beneath weld
bead.
(e) Rust or
mill scale is
prevenng full
fusion.
(f) Wrong
electrode for
posion 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
penetraon and
room for cleaning
out the slag
(c) If very bad,
chip or grind out
Irregularies
(d) Use smaller
electrode with
sucient current
to give adequate
penetraon.
adequate
penetraon. Use
suitable tools to
remove all slag
from corners
(f) Use electrodes
designed for
posion in which
welding is done,
otherwise proper
control of slag is
dicult.