Iron

Iron is known since long before the year zero. At first is was melted in charcoal furnaces. This iron was of very different quality, dependent of the quality of the ore and the quality of the foundry. Often the cast was polluted with slag or gasbubbles which made the cast unreliable. Cast iron contains a lot of carbon, that's why it has poor resistance to tensile forces.

Wrougth iron has much better resistance to tensile forces. To turn the cast iron into wrought iron the castings are heated and hammered by the blacksmith. The heating burns a part of the carbon and the hammering reduces the slag in the material. Making wrought iron this way was a very tedious and slow process. Lateron wrought iron was produced in factories and hammered by steam-hammers. An advantage of wrought iron is that it can be hardened.a Bessemer converter

In time the elements that made the quality of the iron were understood and could be manipulated. And in 1850 the first attempts were made to produce steel. Steel contains no slag and the carbon content could be controlled during the productionprocess. Actually wrought iron was the first step in making steel.

The first steelproduction was done by the Bessemer process. The cast was melted again and air was blown through the melt. This air burned the carbon out. At the same time other elements could be added to the melt to make the steel stronger or better resistant to corrosion.