ET 220I AC/DC
BASIC WELDING GUIDE
Manual 0-5346
4-6
Art # A-07702
Figure 4-16: Multi Run Vertical Fillet Weld
Art # A-07703
Figure 4-17: Examples of Vertical Fillet Welds
2. Vertical Down
Use an 1/8" electrode. The tip of the electrode is held in
light contact with the work and the speed of downward
travel is regulated so that the tip of the electrode just
keeps ahead of the slag. The electrode should point
upwards at an angle of about 45º.
3. Overhead Welds
Apart from the rather awkward position necessary,
overhead welding is not much more difficult that down-
hand welding. Set up a specimen for overhead welding
by first tacking a length of angle iron at right angles to
another piece of angle iron or a length of waste pipe.
Then tack this to the work bench or hold in a vice so
that the specimen is positioned in the overhead position
as shown in the sketch. The electrode is held at 45º to
the horizontal and tilted 10º in the line of travel (Figure
4-18). The tip of the electrode may be touched lightly
on the metal, which helps to give a steady run. A weave
technique is not advisable for overhead fillet welds. De-
posit the first run by simply drawing the electrode along
at a steady rate. You will notice that the weld deposit
is rather convex, due to the effect of gravity before the
metal freezes.
Art # A-07704
Figure 4-18: Overhead Fillet Weld
Distortion
Distortion in some degree is present in all forms of welding. In
many cases it is so small that it is barely perceptible, but in other
cases allowance has to be made before welding commences for
the distortion that will subsequently occur. The study of distortion
is so complex that only a brief outline can be attempted hear.
The Cause of Distortion
Distortion is caused by:
A. Contraction of Weld Metal:
Molten steel shrinks approximately 11 per cent in volume on
cooling to room temperature. This means that a cube of molten
metal would contract approximately 2.2 per cent in each of
its three dimensions. In a welded joint, the metal becomes
attached to the side of the joint and cannot contract freely.
Therefore, cooling causes the weld metal to flow plastically,
that is, the weld itself has to stretch if it is to overcome the
effect of shrinking volume and still be attached to the edge of
the joint. If the restraint is very great, as, for example, in a heavy
section of plate, the weld metal may crack. Even in cases where
the weld metal does not crack, there will still remain stresses
"Locked-up" in the structure. If the joint material is relatively
weak, for example, a butt joint in thin sheet, the contracting
weld metal may cause the sheet to become distorted.
B. Expansion and Contraction of Parent Metal in the
Fusion Zone:
While welding is proceeding, a relatively small volume of the
adjacent plate material is heated to a very high temperature
and attempts to expand in all directions. It is able to do this
freely at right angles to the surface of the plate (i.e., "through
the weld", but when it attempts to expand "across the weld" or
"along the weld", it meets considerable resistance, and to fulfil
the desire for continued expansion, it has to deform plastically,
that is, the metal adjacent to the weld is at a high temperature
and hence rather soft, and, by expanding, pushes against the
cooler, harder metal further away, and tends to bulge (or is
"upset". When the weld area begins to cool, the "upset" metal
attempts to contract as much as it expanded, but, because it
has been "upset" it does not resume its former shape, and the
contraction of the new shape exerts a strong pull on adjacent
metal. Several things can then happen.
The metal in the weld area is stretched (plastic deformation),
the job may be pulled out of shape by the powerful contraction
