STRUCTURAL GLASS FACADES - USC School of Architecture

or some similar process to produce a uniform appearance over the surface of the
component.
2.3.2.2 Ductile Iron
The history of casting with ductile iron dates back over 2,000 years. Although most castings
used in structural glass facades are stainless steel, ductile iron is a good choice for larger
components. Ductile iron is not a single material, but a family of materials with a remarkable
range of properties. The Ductile Iron Society is an excellent resource for the designer or
engineer, providing information on all aspects of the material and process, as well as casting
producers.
Composition and mechanical properties of Austempered Ductile Iron (ADI), one form of
ductile iron with interesting properties, follow. (Keough 1998)
A typical iron composition (and control range) that can be used is shown below:
Carbon* 3.7% +/- 0.2%
Silicon* 2.5% +/- 0.2%
Manganese 0.28% +/- 0.03%
Copper
Nickel
Molybdenum
as required
as required
only if required
+/- 0.05% up to 0.8%
maximum
+/- 0.10% up to 2.0%
maximum
+/- 0.03% up to 0.25%
maximum
Mechanical Properties
ADI is a group of materials whose mechanical properties can be varied over a wide range by
a suitable choice of heat treatment. Figure 4.6 illustrates the strong correlation between
austempering temperature and tensile properties. A high austempering temperature, 750F
(400C), produces ADI with high ductility, a yield strength in the range of 500 MPa (72 ksi)
with good fatigue and impact strength. These grades of ADI also respond well to the surface
strain transformation previously discussed which greatly increases their bending fatigue
strength. A lower transformation temperature, 500F (260C), results in ADI with very high
yield strength (1400 MPa (200 MPa)), high hardness, excellent wear resistance and contact
fatigue strength. This high strength ADI has lower fatigue strength as-austempered but it can
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