Difference Between Cast Iron and Wrought Iron

Cast Iron vs Wrought Iron

Wrought iron and cast iron are two different iron alloys, which can be distinguished from each other based on their composition and properties. Both are produced using pig iron, which is obtained from iron ore.

Wrought Iron

Wrought iron is the purest iron available for commercial purposes. It contains 99.5 – 99.9% iron by weight. Typical wrought iron consists of 0.02% carbon, 0.108% sulfur, 0.12% Silicon, 0.02% Phosphorous and 0.07% slag by weight. Slag contains silicates, aluminosilicates and calcium-alumina-silicates. Wrought iron is produced by refining and smelting pig iron in a solid state. As the word “wrought” implies, wrought iron is made by hammering (working) at a low temperature, which implies that slag is removed by working the metal. This reduction is carried out in a puddling furnace. Moreover, wrought iron is used to make steel and cast iron. Wrought iron is ductile, tough, malleable and strong under tensile loads. However, it cannot withstand sudden and excessive shocks. The presence of carbon, which accounts for its resistance to corrosion, makes it suitable for outdoor applications like gates, structural applications, railings, etc. A fracture surface of wrought iron reveals a fibrous structure. The crystallization of wrought iron is an aggregation of cubical crystals.

Cast Iron

Cast iron contains 2-4% carbon and 1-3% Silicon by weight. Due to the presence of carbon, the melting point of cast iron is low. Also, cast iron has an excellent fluidity. Because of this fluidity, cast iron can be easily cast into complex shapes. Cast iron is produced by smelting raw iron at a higher temperature. It can be classified into white cast iron, grey cast iron, malleable cast iron, nodular cast iron and high alloy cast iron based on their micro structural features and composition. Cast iron has a high compressive strength, high hardness and a high wear resistance. A fracture surface of cast iron reveals a crystalline structure. Cast iron can be further differentiated with wrought iron by its crystallization, which is an aggregation of rhombohedral crystals. Unlike wrought iron, Cast iron is somewhat brittle due to its high carbon content.

These two iron alloys have a broad range of applications due to their higher strength than pure iron. Both are resistant to corrosion due to the presence of carbon in the alloys. However, the two alloys show different property variations because of their different compositions. On account of this, both these alloys show different micro structural variations. Workability of wrought iron and castability of cast iron make these two suitable for decorative items.

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