Question

Describe the processes of conversion of cast iron to wrought iron in brief.

Short answer

Short Answer: The conversion of cast iron to wrought iron involves a series of processes including the puddling process to reduce the carbon content, the formation of iron balls (blooms) as the molten iron solidifies, the removal of these blooms, and finally shaping and finishing the iron to achieve the desired form and properties. This process transforms the brittle and hard cast iron into the more malleable and ductile wrought iron.

Step-by-step solution

Introduction to Cast Iron and Wrought Iron

Cast iron is a type of iron containing a high amount of carbon, typically between 2 to 4%. Due to the high carbon content, cast iron is brittle, hard, and cannot be easily forged or welded. Wrought iron, on the other hand, is also a type of iron, but it contains much less carbon, usually less than 0.08%. Wrought iron is more malleable, ductile, and can be easily forged or welded. The process of converting cast iron to wrought iron involves reducing the carbon content to obtain the desired properties.

Puddling Process

The first process in the conversion of cast iron to wrought iron is the puddling process. In this process, the cast iron is melted in a reverberatory furnace, where the air used for combustion does not come in contact with the iron but heats the roof of the furnace. The cast iron is melted at a temperature of about 1200-1300°C. The molten iron is then stirred by the puddler using a long iron rod to expose the entire surface to air to oxidize the carbon and other impurities. The carbon oxidizes to form carbon dioxide, which escapes as gas, resulting in a decrease in carbon content.

Formation of Iron Balls

During the puddling process, the molten iron gradually loses carbon and other impurities. The residual slag, which includes silica and phosphorus, floats on the surface. Once the carbon content is sufficiently reduced, the semi-solid iron begins to collect at the bottom of the furnace, forming iron balls called "blooms."

Removing the Blooms

The puddler then removes these iron blooms from the furnace using tongs or a similar tool. The iron blooms are then transferred to a separate area, where they undergo further processing to remove any remaining impurities.

Shaping and Finishing

The iron blooms are now reheated and rolled or hammered to remove any residual slag and shape the iron into the desired form, such as bars or sheets.The rolling also helps to homogenize the structure of the iron, making it more uniform and improving its mechanical properties. The final product is wrought iron, which can be used for various applications, including blacksmithing, art, and construction. In conclusion, the process of converting cast iron to wrought involves the following steps: puddling, formation of iron balls, removing the blooms, and shaping and finishing. The primary objective of this process is the reduction of carbon content, which changes the properties of the iron from being brittle and hard to being malleable and ductile.