Miller 900019 Panduan Instalasi dan Pengoperasian - Halaman 15
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Halaman Cetak
TEE AND
LAP
JOINTS
Practice
making
butt welds
starting
on
thin
material about
/8
thick. Avoid
very thin
mater
ial
(around
1/16
thick)
in the
beginning
as
this
requires
a
fair
degree
of
skill.
Separate
the
squared
edges
of
the
/8
material about
1/16
and make
a
butt weld all the
way
through
with
a
/8
electrode.
Probably
the first
attempts
will
fail
to
penetrate
the sheet
or
may
burn
through.
Keep trying, adjusting
the
current
within the
re
commended
range;
also
vary
the travel
speed
to
give
the desired weld.
Having
mastered the
/8,
proceed
to
a
similar exercise
on
1/4~
This
time,
however, deposit
a
bead
on
each side of the
joint
and
try
to
fuse
one
to
the other. Since
the weld
from
one
side is in
effect
on
/8
thickness,
no
bevel is needed.
Next make
a
single
V
groove
on
1/4
plate
LI
beveled
30
degrees.
Start
with
a
/a
electrode for
the first bead
or
layer
and finish with
a
5/32
electrode. Be
sure
to
penetrate
about
1/32
beyond
the bottom of the V
(called
the
root).
When
skill has been
acquired
on
the
...
material,
pro
ceed
to
%
and then
to
‰.
On
these,
particularly
the
‰,
make also the double V
butt
joints.
Generally speaking,
it
will be necessary
to
deposit
a
bead
or
layer
for each 1/s
thickness. On the
heavier
plates weaving
of the
top layers
may be
necessary to
fill the groove
completely.
When
making
practice
butt welds it is wise
to
check the
results
occasionally.
Where elaborate
testing equipment
is
not
available,
this may be
done
with
a
hammer and
vise.
Grip
a
short,
weld
ing piece
with
the
weld
just
above the
jaws.
Hammer it in
a
direction that tends
to
open the
bottom,
root
side
of
the
weld,
in
the
manner
shown
in
Figure
13.1. A
good
weld will
not
break
under
this
test
but will bend
over.
If the weld
breaks,
examine
it
to
determine
the
cause.
If
there
are a
large
number of holesthe
weld looks
spongy
it is porous and
this
probably
due
to
holding
too
long
an
arc.
If there
are
bits of
slag
in
the weld
perhaps
the
arc
was
too
short
or
the electrode
was
manipulated incorrectly
thus
permitting
the molten
slag
from the
coating
to
be
trapped.
This
is
quite
likely
to
happen
on
a
V
joint
made
in several
layers
and calls for
thorough
cleaning
between
layers. Perhaps
on
breaking
it will be found
that the
original
surface
of the bevel
is
still evident. That
means
that it
was
not
melted and the
cause
is
quite likely
to
be found
in too fast
a
travel
speed
or
insufficient
heat.
The other basic
type
of
weld,
the fillet
weld,
is
used for
making
tee
and
lap
joints.
For this
type
of
welding,
no
special preparation,
other
than
squared edges,
is necessary.
Typical
welded
tee
and
lap joints
are
pictured
in
Figures
14.1 and
15.1
respectively.
Considering
the
tee
joint first,
it will be
seen
immediately
that the different locations
of the
pieces
creates
a
problem.
The
method of
holding
the electrode for butt welds will
not
be satis
factory.
To
deposit
a
single
pass
fillet weld hold
the electrode
as
shown in
Figure
16.1.
This will
ARC SHORT AND MOVED AT DEFINITE
RATE OF SPEEDNO
OSCILLATION
-
!?~IKE
HER!
Figure
15.1
Figure
13.1
Figure
16.1
IOM-114A-
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