At what point does iron become steel?
Iron becomes steel when it is mixed with other metals such as nickel. Iron refers to the elemental form.
The common way to smelt iron is in a blast furnace. A blast furnace is charged with iron ore, charcoal or coke (coke is charcoal made from coal) and limestone (CaCO3). Huge quantities of air blast in at the bottom of the furnace. The calcium in the limestone combines with the silicates to form slag. At the bottom of the blast furnace, liquid iron collects along with a layer of slag on top. Periodically, you let the liquid iron flow out and cool.
The liquid iron typically flows into a channel and indentations in a bed of sand. Once it cools, this metal is known as pig iron.
Pig iron contains 4 percent to 5 percent carbon and is so hard and brittle that it is almost useless.
You melt it, mix it with slag and hammer it to eliminate most of the carbon (down to 0.3 percent) and create wrought iron. When you heat wrought iron, it is malleable, bendable, weldable and very easy to work with.
Steel is iron that has most of the impurities removed.
The open hearth furnace is one way
