WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
TABLE 2. CURRENT SETTINGS FOR MINERAL AND
CELLULOSE COATED ELECTRODES.
(4) In preparation for welding, the welding machine must be
adjusted to provide proper welding conditions for the particular
size and type of electrode being used. These adjustments include
proper polarity, as well as current and voltage settings.
The
dual-control machines make possible the separate control of
voltage and current that is delivered to the arc.
In single-
control units, the welding current is controlled manually while
the voltage is adjusted automatically.
(5) When proper adjustment of the welding machine is obtained,
the exposed end of the electrode should be gripped in the
electrode holder so that the entire usable length can be
deposited, without breaking the arc. In some cases, when welding
with long electrodes, the center of the electrode is bared and
gripped in the center. Carbon and graphite electrodes should be
gripped short of the full length to avoid overheating the entire
electrode.
c.
Starting the Arc (figure 12 on the following page).
(1) The following are two methods used for starting the arc:
(1) the striking or brushing method shown in figure 12, view A,
and (2) the tapping method shown in figure 12, view B. In both
methods, the arc is formed by short circuiting the welding
current between the electrode and the work surface. The surge of
high current causes both the end of the electrode and a small
spot on the base metal beneath the electrode to melt instantly.
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