The production of Steel

To make steel, the carbon content of pig iron is reduced from over 3% to less than 1.5% and often to below 0.25% in the case of mild steel.

Other impurities are removed and small amounts of other elements are added.

A great deal of reorganisation has been undertaken in British steel making in recent years. Basic production is concentrated in about five main plants, which use the basic oxygen furnace process to produce 14 million tonnes annually.

The basic oxygen furnace is the principal production method and is used for making large tonnages. The furnace is tilted and charged with molten iron, from the blast furnace, and up to 30% scrap metal. It is then brought to a vertical position.

A water-cooled oxygen lance is lowered to just above the surface of the metal ready for the blow. This consists of blowing oxygen into the melt at high speed to combine with the carbon and other unwanted elements. During the blow, lime is added as a flux, so that the impurities form a slag on the surface. Once the steel has been checked it is tapped out into ladles.