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T H E Man in the Iron Mask
mystified all Europe for many
years, and is still the subject
of considerable romance and
legend, but in our great industries
men in iron masks are not at all
uncommon.
In the rather new process of arc welding,
iron masks are necessary to protect
operators from the terrific heat and dazzling
light. The electric arc is about the
hottest thing in the whole world and
almost as bright as the sun itself. The
temperature of the arc is approximately
3.500 degrees Centigrade, and as the heat
is confined to a comparatively small
space directly in contact with the arc,
the light therefrom is blinding.
Welding by the means of the electric
arc is accomplished by fusing the surfaces
to be welded by means of the high
temperature of the arc and then filling in
with additional material which also is
melted. This in effect is really a method
of casting, and unlike other forms of
welding, the use of mechanical means in
causing the parts to unite is unnecessary.
In some instances the joint is hammered
while hot but this is only for the purpose
of increasing the ductility of the
metal. When the carbon electrode is
used, the filling metal is fed into the arc
by the operator at a rate depending on
the work being done.
The metal on which the welding is to
be done is connected to one side of the
circuit and the electrode, with a suitable
holder, is connected to the other. Then
the operator dons his protective helmet.
The electrode is connected to the negative
side of the circuit and the piece of
work to the positive, for the reason that
the greater amount of heat is generated
at the positive terminal; this prevents a
too rapid consumption of the electrode.
Furthermore, carbon from a graphite
electrode is prevented, to a great degree,
from being carried over into the work,
and thus hard welds are largely eliminated.
The fact that the greater part of
the heat is liberated at the positive electrode
means that the work directly in
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