dermatology - DermaAmin

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Availability of a range of alloys—in a given application, any one of
several alloys may be a suitable candidate, depending on design
loads and corrosivity of the environment.
Reasonable cost—high processing yield and low machining costs
make copper alloy very economical. Gates and risers from castings
and chips from machining are also recycled, which leads to additional
overall cost reductions. In addition, copper alloys do not
require surface coatings, such as paints. The avoidance of surface
coatings further reduces initial costs and provides additional maintenance
savings. In addition, when the component reaches the end
of its useful life, it too is readily and routinely recycled.
COPPER ALLOY FAMILIES
From a metallurgical viewpoint, many copper alloys are single-phase solid
solutions in which the alloying elements, such as zinc, tin, and nickel, are
substituted for copper in the copper matrix. Examples of single-phase
solution alloys include the brasses that contain up to 35% zinc, and copper–
nickels that contain up to 33% nickel. As alloy content is increased, a second
phase may form. In the case of brass, when the zinc content is increased, a
hard second phase called beta forms within the alpha copper-rich matrix.
This second phase is found in yellow brass that contains up to 41% zinc.
Beta, which slightly impairs room temperature ductility, markedly increases
ductility at elevated temperatures. One of the most common systems used
to designate specific copper alloys is the UNS system. Copper alloys are
either wrought or cast. Wrought alloys range in UNS number from C10100
through C79999. They are subjected to hot and usually cold work after initial
melting and solidification, and are generally available as wire, rod, bar,
sheet, strip, and plate. Cast alloys range in UNS number from C80000
through C99999. They are typically cast into a mold in a variety of specific
shapes and then machined without any hot or cold working.
The Coppers
The coppers (wrought: C10100–C15999, and cast: C80000–C81399) are
essentially pure copper (99.7% min) with traces of silver or phosphorus.
The presence of silver imparts annealing resistance, while phosphorus, a deoxidizer,
aids in welding. These alloys, which have relatively low strength, are used
in applications where high thermal and electrical conductivity are desirable,
such as in electrical connectors and in hot metal handling. Copper is used
in low denomination coinage. Some individuals wear copper wrist bracelets.
THE HIGH COPPERS
High copper alloys (wrought: C16000–C19999, and cast: C81400–C83299),
which contain 95.1% copper (min), are unique in that they combine high