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© Weldclass 2020 | E.&O.E.
12
STICK (MMA) BASIC WELDING GUIDE
12.1
Size of Electrodes
The electrode size is determined by the thickness of metals being joined and can also be governed by the
type of welding machine available. Small welding machines will only provide current (amperage) to run
smaller sized electrodes. For thin sections, it is necessary to use smaller electrodes otherwise the arc may
burn holes through the job. A little practice will soon establish the most suitable electrode for a given
application.
12.2
Storage of Electrodes
Always store electrodes in a dry place and in their original containers. If electrodes have been exposed to
moisture or moist air then they will need to be dried out using an electrode drying oven.
12.3
Electrode Polarity
Electrodes are generally connected to the electrode holder with the electrode holder connected positive
polarity.
The work lead is connected to the negative polarity and is connected to the work piece. If in doubt consult
the electrode data sheet.
12.4
Effects of Stick (MMA) Welding on Various Materials
12.4.1
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.
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.
12.4.2
Manganese Steels
The effect on manganese steel of slow cooling from high temperatures causes embrittlement. 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.
12.4.3
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. Trouble may also be experienced when welding
white-heart malleable, due to the porosity caused by gas held in this type of iron.
