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An Overview of Cast Iron and Graphite Iron Castings

Aug 11th 2014 at 2:06 AM

The process of casting basically refers to creating substances in molds of desired shape and sizes and properties. The cast iron foundry manufacturers have been around for quite a long time and evidence of that is in the advancements made in techniques and equipment used in casting as well as quality of casting products. Of the several products that come out of the manufacturers’ foundries three stand out and a simple overview of them will help in gaining an appreciation of the whole industry.

One of the most important products in the industry is Gray iron. This is an alloy of iron, carbon and silicon which is versatile and strong accounting for the largest share of castings in the industry. It derives the name Gray because of the color on the fractured surface when broken. It is popular due to its cost effectiveness and ability to be made into complex shapes and frames. It also allows the convenience of easy machining and high damping capacity. Gray iron has lower vibrations and a compressive strength about three times its tensile strength. All these properties make it a choice material in a number of uses from making columns to breaks folds amongst others.

Ductile iron is closely related with gray iron although it lacks in the maneuverability of grey iron. It however offers many other advantages especially far much superior strength than grey iron. Its ductile nature is the source of its name which is also superior to gray iron. Other areas where is outperforms gray iron include; lighter weight and even lower production cost, greater wear resistance and reduced shrinking.

The third popular product from casting is the compacted graphite iron castings (CGI). CGI is also called Vermicular Graphite Iron and is more of a mix of gray iron and ductile iron. This is aptly illustrated in the shape of its graphite particles which are between the flake graphite particles of grey iron and the spherical graphite particles of ductile iron. This mix enables CGI to have the best properties of the two materials. For example it is twice as strong as gray iron but still has about the same production cost as ductile iron. It also shares the ability for thermal conductivity and high compressive strength of gray iron while at the same time possessing the tensile strength of ductile iron.

The casting of these products has to be fast and accurate to meet the demands of the market. It for this reason that the best manufacturers use green sand vertical molding during the casting process. In this process the front shape of the casting is placed on one side of the mold cake and the back end on the other. This achieves a full casting when the two sides meet. It requires high pressures and speed and results in fast, precise and safe production of castings.

For more information about Compacted Graphite Iron Castings please visit at

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