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 TM 55-1905-222-14
6-23
REPAIR PROPELLER AND PROPELLER SHAFT (Continued).
down-hand welding. Welds can be made In
the vertical position, however, suitable
copper or carbon dams should be used to
aid In supporting the weld metal In order to
obtain a proper joint, it is imperative that
the base metal be locally preheated. The
preheat temperature should be between
600F and 826F (316C and 427C).
In an emergency, a temperature of 400F
(204C) can be used. An approved rod
of 1/4-, 5/16- or 3/8- inch
diameter
should be used, especially on propeller
sections over 3/8 inch thick.
Smaller
diameters, 5/32 inch and 3/16 inch, should
not be used unless absolutely necessary,
and then only when considerable
preheating
has
been
done.
With
sufficient preheat, lower values of the
current ranges recommended by the
electrode manufacturer can be used.
Although lower currents are desirable, the
operator's skill and experience must be
considered. Therefore, higher currents are
preferable to currents too low. Higher
currents risk fine porosity in the weld metal,
but currents too low risk poor fusion and
slag inclusions.
j.
Hot-Flow Process. The hot-flow process
provides a satisfactory method for major
repairs. This process consists of flowing
molten metal of approximately the same
chemical composition as the base metal
into the joint. This flow washes away
and replaces the parent metal and forms a
continuous member upon solidification.
Foundry and mold equipment is necessary
for the use of this process.
6-125
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