The aluminum must be thoroughly cleaned with
dilute nitric acid and kept hot while the solder is applied by forcible
rubbing with the hot iron.
BRAZING
This is a process for joining metal parts, very similar to soldering,
except that brass is used to make the joint in place of the lead and zinc
alloys which form solder. Brazing must not be attempted on metals whose
melting point is less than that of sheet brass.
Two pieces of brass to be brazed together are heated to a temperature at
which the brass used in the process will melt and flow between the
surfaces. The brass amalgamates with the surfaces and makes a very strong
and perfect joint, which is far superior to any form of soldering where the
work allows this process to be used, and in many cases is the equal of
welding for the particular field in which it applies.
_Brazing Heat and Tools._--The metal commonly used for brazing will
melt at heats between 1350 and 1650 Fahrenheit. To bring the parts to
this temperature, various methods are in use, using solid, liquid or
gaseous fuels. While brazing may be accomplished with the fire of the
blacksmith forge, this method is seldom satisfactory because of the
difficulty of making a sufficiently clean fire with smithing coal, and it
should not be used when anything else is available. Large jobs of brazing
may be handled with a charcoal fire built in the forge, as this fuel
produces a very satisfactory and clean fire.
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