Cast Iron

Augusta Machine and Welding, Inc.


Cast iron is an iron-based material with a high percentage of carbon. The five types of cast iron are gray, white, malleable, alloy, and nodular.

Gray cast iron is used a great deal for machine castings. It can readily be identified by the dark gray, porous structure when the piece is fractured. Gray cast iron can be welded with comparative ease.

White cast iron possesses what is known as combined carbon. The fractured piece of white cast iron will disclose a fine, silvery white, silky, crystalline formation. Although white cast iron can be welded, welding is not recommended for this metal.

Malleable cast iron is usually white cast iron which has been subjected to a long annealing process. A fractured piece of malleable cast iron will indicate a white rim and a dark center. Malleable cast iron can be welded; however you must be sure that the metal is not heated above critical temperature. Heating beyond this point reverts the metal back to its original characteristics of white cast iron.

Alloy cast iron can be arc welded, but greater precautions must be taken in the preheating and post-weld heat treatment to prevent the destruction of the alloying elements.

Nodular iron sometimes called ductile iron has the ductility of malleable iron, the corrosion resistance of alloy cast iron and tensile strength greater than gray cast iron. Nodular can be arc welded, providing adequate preheat and post-weld heat treatments are used; otherwise some of the original properties are lost.

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Gray iron castings ...Grade 20, 25, 30, 35, 40, 45, 50, 55, 60
Ductile iron castings ...Grade 60-40-18, 60-45-12, 80-55-06,100-70-03, 120-90-02, 80-60-03
White iron castings ...Most grades
Austempered ducitle iron castings ...Grade 1, 2, 3, 4, 5, 6
Ni-resist iron castings ...Type 1, 1b, 2, 2b, 3, 4, 5, 6

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