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EuroWire – September 2010
67
technical article
Sustainability in the
development and
production of alloys
By Ralf Hojda, Dr Michael Köhler, James Schraml
1 Introduction
The increasing scarcity of resources is
steadily impacting on economic success
in the private and industrial spheres.
Energy supply and raw materials are
equally affected.
Manufacturers of copper-alloy semi-
finished products have experienced price
rises in the three-figure percentage range,
so that in recent years the ratio of the
value added to the metal value, which
was in balance just a few years ago, is now
one to three. Although mechanical and
technological factors were once the
primary criteria for selecting a suitable
alloy, the significance of the value of
the metal has increased. This also has
consequences for the development and
manufacture of alloys.
Developers
are
equally
concerned
about the recyclability of new alloys and
composites as about using stronger alloys
to reduce wall thicknesses, and thus
conserve resources by using less material.
This article uses two developments
to illustrate good recyclability and
reduced use of materials. In the first
case the described material is a new
high-conductivity alloy that can be
recycled without any limitations, even
when tin coated.
The second concerns a high-strength
bronze, which can readily be fed back
into the material cycle and, above all, is
potentially suitable for use in numerous
miniaturisation applications, thus facili-
tating the conservation of resources.
2 Examples
2.1 Development 1
Connecting elements used in the electrical
engineering and electronics sectors have
to satisfy numerous requirements.
Mechanical strength, electrical con-
ductivity and corrosion resistance are
key criteria for the reliable functioning of
components during the total lifetime of
the whole system.
In many cases the required properties
are mutually incompatible, as when
a combination of good conductivity
and excellent resistance to corrosion is
specified.
Although components such as nickel
and chromium improve a copper alloy’s
corrosion resistance, they simultaneously
bring about a considerable reduction in
its conductivity
(see Figure 1).
Composites are a frequently adopted
solution to this problem, primarily in
the form of coatings based on pure tin
applied to the surface of copper alloy.
With just a few exceptions the RoHS
Additions in mass %
Electric conductivity in % IACS (International Annealed Copper Standard)
Electric conductivity in m/Ω mm
2
Figure 1
▼
▼
:
Influence of alloying elements on the electrical conductivity of copper