The steel making process converts brittle iron into steel
, which is tougher and stronger. This process involves the lowering of the carbon content in steel from 4% in liquid iron to 0.1%- 1% in liquid steel.
Raw materials and ironmaking
Iron ore is extracted from mines around the world and is the key raw material in the production of iron. Iron ore is a mixture of various iron oxides such as haematite and magnetite
Ironmaking
Iron ore is converted to iron by reducing the oxides to metallic iron usually by contact with a reducing gas. The reaction takes place at high temperature in a blast furnace producing molten iron.
The blast furnace currently produces over 90% of the worlds iron. Direct reduction accounts for almost all of the remainder.
Steelmaking
The next step in the process is steelmaking. This takes the iron ore and converts it into steel, which is a tougher and stronger material.
The conversion from molten iron to steel primarily involves lowering the carbon content from approximately 4% in liquid iron to 0.1%-1% in the liquid steel.
For approximately the last 30 years, the predominant process has been the Basic Oxygen Steelmaking or BOS process. This accounts for 60% of the world's steel production.
Secondary steelmaking
In order to achieve steel in the exact composition required for the many different applications, there is an additional step required in the steelmaking process. This is known as secondary steelmaking.
After the molten steel is tapped into a ladle from a furnace, the Basic Oxygen Steelmaking (BOS) is usually given one or more extra treatments including:
* Ladle Stirring
* Vacuum Degassing
* Ladle Arc Heating
Some high-grade steels combine all of these treatments. These processes do the following:
* Improve homogenisation of temperature and composition
* Allow composition to be controlled to exact specifications
* Remove unwanted gases and impurities
Steel finishes and specification factors
Steel is coated with a variety of metallic and organic coatings for decoration and corrosion protection
These coatings provide a more cost effective and lower maintenance alternative to painting the final product
Steel intended for roof and wall panels, fencing, furniture and other applications is treated with a flexible paint coating to withstand manufacturing processes such as cutting used to create the end product