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Compacted Graphite Iron

The microscopic structure of gray iron is shown on the left, the stronger CGI is shown on the right.

The microscopic structure of gray iron is shown on the left, the stronger CGI is shown on the right.

Compacted graphite iron (CGI) is a form of cast iron which has elongated graphite particles mixed with spherical graphite particles present within the alloy, as opposed to the graphite “flakes” present in typical cast iron. The shape of the graphite particles present in CGI greatly enhance the strength and hardness of the iron. CGI is used for NASCAR and NHRA Pro Stock engine blocks due to its superior properties. CGI is approximately 100% stronger than gray iron without any additional weight. Fatigue resistance and thermal properties are also improved.

Compacted graphite iron is visually indistinguishable from gray iron, but machining procedures are considerably different due to the greatly increased hardness of the material.

Dart offers compacted graphite iron versions of many of our iron blocks and heads.

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