Tweco 200 ACDC Arcmaster(April2006) - Manual (Page 45)

ARCMASTER 200 AC/DC
April 13, 2006 8-1
SECTION 8:
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 Ateels
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 abso-
lutely essential to keep manganese steel cool during weld-
ing by quenching after each weld or skip welding to dis-
tribute 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 con-
ductivity 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 pur-
poses, 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 applica-
tions likely to be encountered; are all easy to use and all
will work on even the most basic of welding machines.