The key difference between cast iron and wrought iron is that cast iron has 2-4% carbon by weight while wrought iron has 0.02% carbon by weight.
Wrought iron and cast iron are two different iron alloys. The initial material for the production of these materials is pig iron, which is obtained from iron ore. We can identify the difference between cast iron and wrought iron based on their composition and properties.
What is 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. Moreover, cast iron has excellent fluidity. Because of this fluidity, we can easily cast it into complex shapes. The production process of this material includes the smelting of raw iron at a higher temperature.
There are different types of cast iron as white cast iron, grey cast iron, malleable cast iron, nodular cast iron and high alloy cast iron depending on their microstructural features and composition. Cast iron has high compressive strength, high hardness and high wear resistance. A fracture surface of this material reveals a crystalline structure. We can further differentiate this material 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.
What is 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.
The production of wrought iron includes refining and smelting of pig iron in 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. Furthermore, we can carry out this reduction in a puddling furnace.
Moreover, wrought iron is useful to make steel and cast iron. It 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.
What is the Difference Between Cast Iron and Wrought Iron?
The key difference between cast iron and wrought iron is that cast iron has 2-4% carbon by weight while wrought iron has 0.02% carbon by weight. 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. Thus, both these alloys show different microstructural variations. Moreover, workability of wrought iron and castability of cast iron make these two suitable for decorative items.
Summary – Cast Iron vs Wrought Iron
Wrought iron and cast iron are two different iron alloys. The key difference between cast iron and wrought iron is that cast iron has 2-4% carbon by weight while wrought iron has 0.02% carbon by weight.
1. Bailey, Norman. “Potential Welding Problem Areas.” Weldability of Ferritic Steels, 1994, pp. 45–53., doi:10.1533/9781845698935.45.