6 BASIC WELDING GUIDE
0463 815 001
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© ESAB AB 2021
6.4
MMA
(SMAW)
Basic
Welding
Technique
Size
of
electrode
The electrode size is determined by the thickness of metals being joined and by the type of
welding machine available. Small welding machines will only provide sufficient current to run the
smaller size electrodes.
For thin sections, it is necessary to use smaller electrodes otherwise the arc may burn holes
through the workpiece. Practice will soon establish the most suitable electrode for a given
application.
Storage
of
electrodes
Always store electrodes in a dry place and in their original containers.
Electrode
polarity
Electrodes are generally connected to the electrode holder. The electrode holder is connected to
the positive polarity. The work lead is connected to the negative polarity and it is connected to the
workpiece. If in doubt consult the electrode data sheet or your nearest accredited ESAB
distributor.
6.5
Effects of arc welding on various materials
High tensile and alloy steels
The two most prominent effects of welding these steels are the formation of a hardened zone in
the weld area, and, if suitable precautions are not taken, the occurrence in this zone of under-
bead cracks may result. Hardened zone and under-bead cracks in the weld area may be reduced
by using the correct electrodes, preheating, using higher current settings, using larger electrodes
sizes, short runs for larger electrode deposits or tempering in a furnace. Hydrogen controlled
electrodes must be used for this application.
Austenitic manganese steels
The effect on manganese steel of slow cooling from high temperatures is to embrittle it. For this
reason it is absolutely essential to keep manganese steel cool during welding by quenching after
each weld or skip welding to distribute the heat.
Cast iron
Most types of cast iron, except white iron, are weldable. White iron, because of its extreme
brittleness, generally cracks when attempts are made to weld it. Welding whiteheart malleable
iron can be problematic, due to the porosity caused by gas held in this type of iron.
Copper and alloys
The most important factor is the high rate of heat conductivity of copper, making preheating of
heavy sections necessary to give proper fusion of the weld and the base metal.
Arc welding practice
The techniques used for arc welding are almost identical regardless of what types of metals are
being joined. Naturally enough, different types of electrodes would be used for different metals as
described in the following section.
Welding position
The electrodes dealt with in this publication can be used in most positions, i.e. they are suitable
for welding in flat, horizontal, vertical and overhead positions. Numerous applications call for
welds to be made in positions intermediate between these. See some of the common types of
welds below.
