NOTE:
Note the polarity of wiring, the general DC welding wire in two ways. Selected according to the
technical re quirements of welding the appropriate connection, if you choose incorrectly will
result in arc instability and spatter large adhesion and other phenomena, such cases can be quickly
reversed to joints.
If the work piece distance from the welding machine, the second line(electrode holder and
ground) is longer, so choose the appropriate conductor cross -sectional area should be larger to
reduce cable voltage drop.
3.2.3 MMA Welding
One of the most common types of arc welding is manual metal arc welding (MMA) or stick welding.
An electric current is used to strike an arc between the base material and a consumable electrode rod
or ‘stick’. The electrode rod is made of a material that is compatible with the base material being
welded and is covered with a flux tha t gives off gaseous vapours that serve as a shielding gas and
providing a layer of slag, both of which protect the weld area from atmospheric contamination. The
electrode core itself acts as filler material the residue from the flux that forms slag coverin g over the
weld metal must be chipped away after welding.
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The arc is initiated by momentarily touching the electrode to the base metal.
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The heat of the arc melts the surface of the base metal to form
a molten pool at the end of the electrode.
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The melted electrode metal is transferred across the arc into
the molten pool and becomes the deposited weld metal.
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The deposit is covered and protected by a slag which comes
from the electrode coating.
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The arc and the immediate area are enveloped by an
atmosphere of protective gas.
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