Cast Iron

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

exceeding two electrode diameters.

Never use a full weave

pattern.

Skip weld as practical, and peen the weld to relieve

stresses while cooling larger pieces.

Avoid toe cracks and

undercutting.

A soft steel wire pedestal can help to absorb

shrinkage forces.

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.

e.

Cast Iron.

(1) General.

Gray cast iron has low ductility; therefore, it

will neither expand, nor stretch, to any considerable extent

before breaking or cracking.

Because of this characteristic,

preheating is necessary when cast iron is welded by the

oxyacetylene welding process. However, it can be welded with the

metal arc without preheating if the welding heat is carefully

controlled.

This can be accomplished by welding only short

lengths of the joint and allowing these sections to cool.

By

this procedure, the heat of welding is confined to a small area

and the danger of cracking the casting is eliminated.

Large

castings with complicated sections, such as motor blocks, can be

welded without dismantling or preheating.

Special electrodes

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

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