Tweco 300 TS Arcmaster(Feb2006) - Manual (Page 42)

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8.0 BASIC ARC WELDING GUIDE
8.01 Electrode Polarity
Stick electrodes are generally connected to the ‘+’ terminal and the work lead to the ‘
−’ terminal but
if in doubt consult the electrode manufacturers literature.
8.02 Effects of Stick Welding 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. 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.
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. Trouble may also be experienced
when welding white-heart malleable, 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 weld and base metal.
Types of Electrodes
Arc Welding electrodes are classified into a number of groups depending on their applications.
There are a great number of electrodes used for specialized industrial purposes which are not of
particular interest for everyday general work. These include some low hydrogen types for high
tensile steel, cellulose types for welding large diameter pipes, etc. The range of electrodes dealt with
in this publication will cover the vast majority of applications likely to be encountered; are all easy to
use and all will work on even the most basic of welding machines.