GRAY
IRON ALLOY CASTINGS
When it comes to gray iron castings, we're considered experts!
Mechanical
Properties of Gray Iron
Microscopically,
all gray irons contain flake graphite dispersed in a silicon-iron
matrix. How much graphite is present, the length of the
flakes and how they are distributed in the matrix directly
influence the properties of the iron. The basic strength
and hardness of the iron is provided by the metallic matrix
in which the graphite occurs.
The
properties of the metallic matrix can range from those of
a soft, low carbon steel to those of hardened, high carbon
steel. The matrix can be entirely ferrite for maximum machinability
but the iron will have reduced wear resistance and strength.
An entirely
pearlitic matrix is characteristic of high strength gray
irons, and many castings are produced with a matrix microstructure
of both ferrite and pearlite to obtain intermediate hardness
and strength. Alloy additions and/or heat treatment can
be used to produce gray iron with very fine pearlite or
with an acicular matrix structure. Graphite has little strength
or hardness. It decreases these properties of the metallic
matrix,however, the presence of the graphite provides several
valuable characteristics to cast iron.
These
include:
- The
ability to produce sound castings economically in complex
shapes such as water cooled engine blocks
- Good
machinability even at wear resisting hardness levels and
without burring
-
Dimensional stability under differential heating such
as in brake drums and disks
- High
vibration damping as in power transmission cases
- Borderline
lubrication retention as in internal combustion engine
cylinders
Learn
a whole lot more
by reading our complete Gray Iron Casting
Guide. It's in a PDF, for easy downloading &
printing.
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