WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
down or sag on the plate. If the arc is too long, the difficulty
in transferring metal from the electrode to the base metal is
increased and large globules of molten metal will drop from the
electrode and the base metal.
This action can be prevented by
first shortening and then lengthening the arc at intervals. Care
must be taken not to carry too large a pool of molten metal in
the weld.
(a) When bead welding, the electrode should be held at an angle
of 90 degrees to the base metal as shown in figure 23, view A, on
the previous page. The electrode may be tilted approximately 15
degrees in the direction of welding as shown in figure 23, view B
to provide a better view of the arc and crater of the weld.
(b) Weave beads can be made in the overhead position by using
the motion illustrated in figure 23, view C. A rapid motion is
necessary at the end of each semicircular weave in order to
control the molten metal deposit.
Excessive weaving should be
avoided because this will cause overheating of the weld deposit
and the formation of a large pool of metal which will be hard to
control.
(2) Butt Joints.
(a) The plates should be prepared for butt welding in the
overhead position in the same manner as that required in the flat
position, and the most satisfactory results are obtained if
backup strips are used. If the plates are beveled with a feather
edge and no backup strip is used, the weld will tend to burn
through repeatedly unless extreme care is taken by the operator.
(b) For overhead butt welding, bead rather than weave welds are
preferred.
Each bead should be cleaned and the rough areas
chipped out before the following pass is deposited.
The first
pass should be made with the electrode held at 90 degrees to the
plate as shown in figure 23, view D.
(c) The position of the electrode and the order to be followed
in depositing beads on 1/4 and 1/2 inch plates are illustrated in
figure 23, views E and F.
(d) Fairly small diameter electrodes should be used to assist
in holding a short arc and developing a good penetration at the
root of the
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