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3.2.4. MMA Welding Fundamentals
Electrode Selection
As a general rule, the selection of an electrode is straight forward, in that it is only a matter of
selecting an electrode of similar composition to the parent metal. However, for some metals there
is a choice of several electrodes, each of which has particular properties to suit specific classes of
work. It is recommend to consult your welding supplier for the correct selection of electrode.
Electrode Size
The size of the electrode generally
depends on the thickness of the section
being welded, and the thicker the section
the larger the electrode required. The
table gives the maximum size of
electrodes that maybe used for various
thicknesses of section base on using a
general purpose type 6013 electrode.
Welding Current (Amperage)
Correct current selection for a particular
job is an important factor in arc welding.
With the current set too low, difficulty is
experienced in striking and maintaining
astable arc. The electrode tends to stick
to the work, penetration is poor and
beads with a distinct rounded profile will
be deposited.Too high current is
accompanied by overheating of the
electrode resulting undercut and burning
through of the base metal and producing
excessive spatter. Normal current for a
particular job may be considered as the
maximum, which can be used without burning through the work, over-heating the electrode or
producing a rough spattered surface.The table shows current ranges generally recommended for a
general purpose type 6013 electrode.
Arc Length
To strike the arc, the electrode should be gently scraped on the work until the arc is established.
There is a simple rule for the proper arc length; it should be the shortest arc that gives a good
surface to the weld. An arc too long reduces penetration, produces spatter and gives a rough
surface finish to the weld. An excessively short arc will cause sticking of the electrode and result in
AverageThickness of
Material
MaximumRecommended
Electrode Diameter
1.0-2.0 mm
2.5 mm
2.0-5.0 mm
3.2 mm
5.0-8.0 mm
4.0 mm
>8.0 mm
5.0 mm
Electrode Size
ø mm
Current Range
(Amps)
2.5 mm
60-95
3.2 mm
100-130
4.0 mm
130-165
5.0 mm
165-260
