WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
(c) Electrodes are identified by classification numbers which
are always marked on the electrode containers. For low hydrogen
coatings, the last two numbers of the electrode classification
should be 15, 16, or 18.
Electrodes of 5/32 and 1/8 inch in
diameter are the most commonly used since they are more adaptable
to all types of welding of this type steel.
(3) It is important to avoid excessive heat concentration when
welding in order to allow the weld area to cool rather quickly.
For satisfactory welds, along with good welding practices, use a
straight stringer bead whenever possible. Restrict the weave to
a partial weave pattern.
Best results are obtained by a slight
circular motion of the electrode with the weave area never
Never use a full weave
Skip weld as practical, and peen the weld to relieve
stresses while cooling larger pieces.
Avoid toe cracks and
A soft steel wire pedestal can help to absorb
Butter welding (laying a bead, then grinding
it off) in the toe area before fillet welding strengthens the
area where a toe crack may start.
Gray cast iron has low ductility; therefore, it
will neither expand, nor stretch, to any considerable extent
Because of this characteristic,
preheating is necessary when cast iron is welded by the
metal arc without preheating if the welding heat is carefully
This can be accomplished by welding only short
lengths of the joint and allowing these sections to cool.
this procedure, the heat of welding is confined to a small area
and the danger of cracking the casting is eliminated.
castings with complicated sections, such as motor blocks, can be
welded without dismantling or preheating.
designed for this purpose are usually desirable.
(2) Welding Techniques.
(a) Cast iron can be satisfactorily welded with a coated steel
electrode, but this method should be used as an emergency measure
only. When using a steel electrode the contraction of the