Copper breaks very easily at a heat slightly under the welding temperature
and after cooling it is simply cast copper in all cases.
_Brass and Bronze._--It is necessary to preheat these metals, although
not to a very high temperature. They must be kept well covered at all times
to prevent undue radiation. The flame should be produced with a nozzle one
size larger than for the same thickness of steel and the small blue-white
cone should be held from one-fourth to one-half inch above the surface of
the work. The flame should be neutral in character.
A rod or wire of soft brass containing a large percentage of zinc is
suitable for adding to brass, while copper requires the use of copper or
manganese bronze rods. Special flux or borax may be used to assist the
flow.
The emission of white smoke indicates that the zinc contained in these
alloys is being burned away and the heat should immediately be turned away
or reduced. The fumes from brass and bronze welding are very poisonous and
should not be breathed.
RESTORATION OF STEEL
The result of the high heat to which the steel has been subjected is that
it is weakened and of a different character than before welding. The
operator may avoid this as much as possible by first playing the outer
flame of the torch all over the surfaces of the work just completed until
these faces are all of uniform color, after which the metal should be well
covered with asbestos and allowed to cool without being disturbed.
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