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Graphite Morphology in Cast Irons

Published online by Cambridge University Press:  21 February 2011

Carl R. Loper Jr.
Carl R. Loper Jr.*
Affiliation:
Professor Of Metallurgical Engineering The University of Wisconsin-Madison, Madison, WI, U.S.A.
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Abstract

Graphite structures formed during the cooling of molten cast irons and during their solidification were examined in alloys as a function of composition, treatment (magnesium and/or rare earths) and inoculation. The effect of cooling rate and solidification conditions on the morphology of the resultant graphite was investigated using a variety of techniques (optical and scanning electron microscopy, etching procedures, etc.) to reveal the growth characteristics of this phase and its relationship to other phases developing during the solidification process. These graphite forms have been classified according to their morphology and the factors affecting their development. Examples of these graphite forms are presented and their growth conditions and charateristics analyzed.

Kish graphite is shown to form, not as a result of internal development in a melt and subsequent flotation to the surface, but by a surface growth mechanism forming extensive graphite plates. Proeutectic graphite also forms in the melt just prior to the appearance of the eutectic, however, its growth in the absence of austenite is shown to be limited.

While a variety of graphite morphologies have been identified in eutectic solidification, it is shown that these graphite shapes may develop from the same nucleation sites, that growth conditions determine the graphite morphology, and that as the growth conditions are altered the morphology of the resultant graphite is correspondingly affected. The transition between graphite shapes such as flake, compacted, spheroidal, exploded, etc. is depicted in various microstructures.

In addition, the relationship between certain compounds (e.g., titanium carbo-nitride, etc.) and graphite growth is demonstrated and discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 34: Symposium – Physical Metallurgy of Cast Iron , 1984 , 57
Copyright
Copyright © Materials Research Society 1985

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References

REFERENCES

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