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Microstructure of gray iron

Gray iron microstructure Gray iron has an easily recognizable microstructure, with a series of graphite flakes in a silicon-iron matrix.

This microstructure is the source of all the qualities of gray iron castings, but it also makes for a brittle material that cannot sustain elongation. When you need deformation or higher loads, ductile iron castings become a better choice.

Saguenay Foundry's gray irons have a range of physical properties, with traction results from 25,000 psi to 50,000 psi. Alloying elements can also be added to obtain a variety of characteristics. Our engineers will be pleased to advise you about what will be the best choice for your requirements.

Among the particular alloying elements possible for gray iron, some of them makes it the choice material for heat resisting application. This can be particularly useful for castings like aluminum siphons, where molten metal must pass through the part. Our team will help you decide what fits best your particular application.

Microstructure of Gray iron under a 100X microscope

Microstructure of ductile iron

Ductile iron microstructure

The spheroidal microstructure gives the material its ductility. It is obtained my adding magnesium to the laddle.

The Mechanical properties of ductile iron can then be modified by adding certain perlitising elements. With it, we can obtain a range of materials, from a ferritic matrix that can reach over 18% elongation, to a very perlitic matrix that can obtain 100,000 psi of tensile strength.

In both cases, high nodularity is very important to maintain a good structural integrity. To ensure good results, Saguenay Foundry applies the strictest control over its process, assuring quality and consistency.


An example of a ductile iron microstructure under a 100X microscope.

Microstructure of Compacted Graphite Iron casting

Compacted Graphite iron microstructure

CG iron castings obtain better results for thermal fatigue than gray iron in certain applications, mostly when the brittle nature of gray iron becomes an inconvenient. It can often outperform both ductile iron castings and gray iron castings in applications with thermal shock resistance required. Fast cooling ingot mold are a great example of application with such high thermal shock resistance requirement.

We can add perlitising elements to enhance the mechanical properties of CG iron just like we do with ductile iron. A ferritic matrix will still give more elongation, while a perlitic matrix will raise the tensile resistance of the material.

Our team will be able to guide you so you can choose the best material for your needs.

Microstructure of Compacted graphite iron under a 100X microscope.

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