Steel is the most important metal in the world
with an annual production of about 600 million tonnes.
Different steels are used in a wide range of products.
Steels are fundamental to transport.
Steel is one of the basic building materials, both for interior
and exterior use.
The principle of iron and steel production is that iron is extracted from its
ores by heating with coke and limestone
in a blast furnace.
Molten iron then becomes the raw material for producing steel
in the basic oxygen steel-making process.
On this site iron is extracted from its ores in these four blast furnaces.
Coke is made in ovens here.
Sintering, that is blending iron ore, coke and limestone, takes place here.
Iron is converted to steel
in the basic oxygen process in this plant and finished materials are converted
into a variety of shapes here.
The essential raw materials for making iron are iron ores, coal and limestone.
Iron ores are imported.
Limestone is quarried and delivered by road.
Coal is imported.
The coal is converted to coke by heating for 18 hours in an oven.
Gases, tar and ammonia
are driven off and collected leaving an impure form of carbon.
The ore, coke and limestone are blended
in this ore bed.
They're crushed and heated together to form sinter.
Sinter will not collapse in the furnace.
It has a large surface area to speed up reactions.
Sinter and extra coke, ore and limestone, known as the charge,
are lifted to the top of the blast furnace.
Furnaces run continuously day and night. A blast furnace
is a steel tower up to 40 meters high, lined with heat-resistant
brick. The charge is delivered into the top of the furnace.
Hot air is blown in at the bottom. Molten iron is produced,
and slag.
Coke burns producing heat and carbon monoxide.
The carbon monoxide reduces the iron oxide in the ore
to molten iron.
Limestone, calcium carbonate, decomposes to calcium oxide.
This reacts with the sandy impurities in the ore to give molten slag,
mostly calcium silicate.
The blast furnace reactions are maintained by blowing hot air
into the base of the furnace. Between 10 and 20 times a day
the molten iron called hot metal is tapped into torpedo ladles.
Torpedo ladles hold
300 tonnes of molten iron.
Molten slag floats on top of the iron and is tapped along with it.
The slag cools and solidifies. It can be used in cement
and for road building.
At this stage the molten iron contains around four percent carbon
and other impurities. The iron is brittle.
Steelmaking improves the properties of iron.
In the basic oxygen steelmaking process,
the BOS process, a converter is partly charged
with solid steel scrap. Hot metal from the blast furnace
makes up three quarters of the charge.
A high-speed jet of oxygen is injected onto the molten iron
and lime, calcium oxide, is added. The oxygen converts the impurities
into their oxides. The main effect is to reduce the percentage of carbon.
Carbon monoxide is collected for use as a fuel.
The other oxides react with lime
to produce slag. Molten metal is drawn off through a tap hole.
After further treatment
the steel is solidified. One method is to use moulds
to form steel ingots. A more recent method is continuous casting
where steel is poured through cooled copper molds
and drawn downwards by rollers.
The resulting steel shape is cut into lengths. Rolling the steel
produces the finished shapes required.