3.3.3 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 that 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 covering over the weld metal must be chipped away after welding.
●The arc is initiated by momentarily touching the electrode to
the base metal.
●The heat of the arc melts the surface of the base metal to
form a molten pool at the end of the electrode.
● The melted electrode metal is transferred across the arc into
the molten pool and becomes the deposited weld metal.
● The deposit is covered and protected by a slag which comes
from the electrode coating.
● The arc and the immediate area are enveloped by an
atmosphere of protective gas.
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