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Die casting is a process in which molten metal is injected under
considerable pressure into the cavity of a metal mold to form
the casting. It is also referred to as pressure die casting, but
should not be confused with gravity die casting which is another
term for permanent mold casting.
The die casting process was invented in 1905 by H. Doehler, and
it has become very popular for certain metals. The first brass
die castings produced on a commercial scale were made about 1930.
However, the main factor limiting the development of this method
of casting of copper and copper alloys has been the fact that
die life is relatively short. Copper alloys have higher casting
temperatures than other metals that are commonly die cast, and
this makes it necessary to use special die materials to obtain
serviceable and economical die performance. Improved materials
have been developed for dies, for the die casting of copper and
copper alloys. Results of a recent research project by CDA/USA
and ICA on the pressure die-casting of copper motor rotors proved
that a special high-temperature, nickel-based superalloy, in conjunction
with mold preheating, could be used to economically die cast copper
products.
Yellow brasses are most suitable for die casting. However, tin,
silicon, aluminum, and manganese bronzes can be die cast. Common
casting weights are normally less than 0.5 pounds, and rarely
exceed 2 pounds. Relatively complex castings are possible.
Dies for the casting of brass can have a service life from 10,000
to 50,000 cycles before repair or replacement is necessary. The
service life of the dies depends on the size, weight, and wall
section of the casting being produced, and the alloy being cast.
Under similar conditions, dies for thin-walled castings outlast
those for heavy-sectioned parts.
Brass die castings have a number of attractive properties. A typical
brass die casting will have high strength and toughness, with
a high level of dimensional accuracy and close tolerances, as
well as good surface finish. High production rates result in low
unit cost.
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