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Wrought iron

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Wrought iron is a special kind of metal used for many jobs. The word "wrought" means "worked," which tells us how it is made. Workers hammer, roll, or shape the metal while it is still hot.

Puddling furnace
Puddling furnace

This metal is very different from cast iron. Cast iron has a lot of carbon, which makes it brittle. If you try to bend cast iron, it will snap or break. Wrought iron has very little carbon, which makes it malleable. This means it is easy to bend and shape without breaking.

Making wrought iron is a step-by-step way of cleaning the metal. It starts with high carbon cast iron in a hot furnace. This is often done in a process called puddling.

Chinese fining
Chinese fining

Inside the furnace, the heat makes the extra carbon react with oxygen. A worker stirs the melting metal with a long rod. This stirring helps the carbon leave the iron. As the carbon goes away, the iron becomes harder to melt. It never becomes a thin liquid, but stays a thick, soft mass.

People have used different ways to make this metal for a long time. In China, during the Han dynasty, people used fining hearths to make iron tools.

A231 - Optical micrograph of wrought iron
A231 - Optical micrograph of wrought iron

They made things like iron ploughs for farms. In Europe, the puddling process was patented in 1784. This was the first way to make wrought iron on a very large scale. By the year 1876, the United Kingdom was making over 4 million tons of puddled iron every year.

There are many interesting facts about how this metal looks and acts. Wrought iron is about 99.4% pure iron. It contains small bits of glass-like material called silicate slag. These tiny bits form long layers inside the metal.

Puddling furnace
Puddling furnace

This gives the iron a grain that looks just like wood. The slag also helps protect the iron from rust. Because of these layers, the metal is anisotropic. This means its strength changes depending on which direction you pull it.

In the past, wrought iron was used for almost everything. People used it to make nails, chains, and even horseshoes. It was also used for railway rails and heavy water pipes. As new ways to make steel were found, wrought iron became less common. Today, we mostly use mild steel for those same jobs. Many garden gates look like wrought iron, but they are actually made of mild steel. They are just made to look like the old, worked iron from long ago.

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🖼️ Images & Media (3)
File:Chinese fining.png
Chinese fining.png
File:Puddling furnace.jpg
Puddling furnace.jpg
File:A231 - Optical micrograph of wrought iron.jpg
A231 - Optical micrograph of wrought iron.jpg
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