what can you make with steel, cars, buildings, bridges, ships, what else?
how about knives and forks, fridges and washing machines, food and drink cans
train tracks
anything else try everything else yes everything because even if something is
made of steel steel will have been used to make it from paper clips to pipe
lines paper to plastics nothing in this world could be made moved or
manufactured without steel so how do you make the product that helps make
everything else well the quick answer is you take iron ore coke and limestone and
put it in the top of a blast furnace blast stare at it until it's hot very
hot white hot in fact and out of the bottom you get molten iron the material
from which steel is made making molten iron into steel involves removing some
impurities such as carbon and silicon in other words it has to be refined and
this is done by blowing oxygen onto it other elements are then added to adjust
the steels composition making it suitable for any one of the thousands of
purposes for which it could be used the molten steel is then solidified before
being formed into a suitable useable shape well that's the quick answer but
now let's take a closer look at each of those processes and the effect they have
on the production of steel
steel is an alloy or metallic mix of mainly iron and carbon as a finished
product it's carbon content is between naught point naught 2 and 1.5% but to
start the production process we need high quality iron or iron ore is common
in the Earth's crust and contains iron chemically bonded to oxygen this is
mined in places such as the Americas Australia and Scandinavia and then
shipped around the world to steelworks ores are then blended together to
produce a favourable mix this mix is combined with coke and heated to produce
the iron rich material called sinter sintering reduces waste and provides an
efficient raw material for the blast furnace carbon is required for the blast
furnace and this is supplied in the form of coke to make coke coking coal is
heated in an oven this drives off volatile byproducts and leaves carbon
gas produced in this process is used as a fuel whilst other byproducts such as
tar and sulfur are extracted and refined
these raw materials sinter iron ore and coke meet each other at the blast
furnace where they are fed into the top of the furnace along with some limestone
a hot air blast from which the furnace gets its name is injected through
nozzles called queers in the base of the furnace this blast raises the
temperature in the furnace to white-hot intensity around 2,200 degrees
centigrade this very high temperature is needed for the chemical reduction and
melting of the sinter and iron ore to form a pool of molten iron in the lower
part of the furnace just above the half the limestone combines with the
impurities to form a liquid which floats on top of the molten iron this is known
as slag the molten iron is tapped from the furnace and the slag skimmed off and
taken away for use in other industries such as road building or cement
manufacture
the molten iron we get from a blast furnace or hot metal as it's known in
the industry isn't pure iron and contains the elements carbon sulfur
phosphorus manganese and silicon to make steel these elements must be removed or
reduced and other elements added depending on the type of steel being
made the carbon content at about four percent makes iron very brittle and
unsuitable for rolling or forging and although iron can be used for castings
most of the iron produced is for processing into steel basic oxygen
steelmaking or BOS is the main bulk production process for refining iron
into steel BOS vessels can take up to 350 tons of molten iron at a time and
convert it into steel in less than 30 minutes
first scrap steel is put into the vessel and then the hot metal is added which
may have been pre treated to remove elements such as sulfur a lance then
blows high purity oxygen onto the hot metal at about twice the speed of sound
the oxygen combines with impurities and this oxidation produces heat the
temperature is controlled by the quantity of scrap steel and also by the
addition of iron ore as a coolant the oxidized carbon creates carbon monoxide
gas which can be collected cleaned and used as a fuel
the other oxidized impurities combined with lime that has been added during the
blow to form a slag the quantities of scrap hot metal or lime and other
substances are calculated to ensure correct temperature and composition of
the steel refining can be assisted by injecting argon nitrogen or oxygen gases
through the base of the vessel and a sub lance is used to measure carbon and
temperature during the blow to allow final adjustments to be made during
tapping alloy additions are also made to adjust steel composition by this stage
the carbon has been reduced from around four percent to about naught point
naught 5 percent finally the vessel is tipped to remove the slag for recycling
the other main method of making steel is by means of the electric arc furnace or
eaf as it's known the eaf process predominantly uses cold steel scrap
making it one of the world's largest recycling processes ei FS make up to 150
tons of steel in a single melt in less than an hour the furnace is filled with
recycled steel scrap the roof is then swung into place and three graphite
electrodes are lowered into the furnace a powerful electric current is passed
through the furnace an arc is created and the heat generated melts the steel
scrap lime and fluorspar are added and usually carbon and oxygen are blown into
the melt as a result impurities in the metal combine to form a slag
the steel is sampled and analyzed and once it reaches its correct temperature
and Composition it is tapped off at this stage final adjustments to precise
customer specifications can be made by adding alloying elements these furnaces
give very precise control over composition and are used for producing a
variety of special Steel's including alloy steels and stainless steels many
bulk Steel's are also increasingly made by this route and it's expected that eaf
output will account for half the world's steel production within a few years
small steel producing plants operating with EAS closely linked to casting and
rolling facilities are often referred to as mini mills these can produce
relatively low volumes of specialist products mini mills are often situated
very close to where these products are most in demand
after the BOS or AAF steelmaking processes a combination of secondary
steelmaking processes is used to further refine the steel these specialist
processes are designed to improve the consistency of temperature and
Composition within the steel they allow the removal of gases such as hydrogen
and the reduction of elements like sulfur and the addition of alloys and
slags all of this ensures the steel meets exact customer specifications
before casting
continuous casting is the process used to solidify the molten steel ready for
shaping a ladle of Steel is teemed or poured through a gas tight refractory
tube into a tundish this is a reservoir and feeds the steel through further gas
tight refractory tubes into a number of water-cooled copper molds the flow rate
is controlled and with only the outer shell solidified the steel is drawn from
the bottom of the mold through a curved arrangement of support rolls and water
sprays it then emerges horizontally as solid steel strands and is cut to length
by automatic gas burners depending on their size these solid shapes are called
billets plumes and slabs and are now ready for shaping into finished products
sections rails rods wire and bar tubes and plates profiles and strip our
finished products are the raw materials for thousands of other industries
although forging and extrusion can be used to shape steel we are mainly going
to look at the principles of steel rolling steel is highly resistant to
shaping when it's cold and for that reason it's generally rolled whilst it's
hot to make sure the steel is at the correct temperature for rolling it's fed
into a furnace here it travels through several temperature control zones until
it's at the correct temperature and ready for rolling whatever the product
the principles of hot rolling are the same steel is squeezed between rolls
until the final thickness and shape are achieved to
do this to steal the rolls must exert forces of tens of millions of Newtons
equivalent to the weight of thousands of tons so the rolls run in massive
bearings mounted in housings of great strength and driven by powerful electric
motors these are known as mill stands layouts of rolling mill arrangements
vary from a simple single stand to several stands either side-by-side or in
a line the rolls themselves can either be planed for flat product such as strip
for car panels or profiled for sections and bars such as beams for use in
construction mill stands have various roll arrangements depending on what
product is being rolled the simplest arrangement is a two high stand and
these are mainly used for long products such as sections piling rails and rod
rolling for light sections and bars three high stands are sometimes used
with the steel passing one way through the back through the top gap for high
stands have to work rolls in contact with the steel supported by larger back
up rolls to prevent distortion caused by the rolling face these give greater
accuracy for rolling flat products Universal beam Mills also include stands
with both horizontal and vertical rolls bearing on the steel simultaneously
rolling processes are computer-controlled they're monitored up
to 50 times per second and measured to an accuracy of plus or minus 50 microns
the rolled steel is then cooled in a way appropriate to its end use and prepared
for further processing or dispatch
one of the further processes is cold rolling of strength this is used to
produce a thinner flatter product than it's possible on a hot mill down to a
thickness of naught point one five millimeters forming properties and
surface finish of cold rolled strip is better
it can also be coated with zinc to protect it from corrosion with tin four
cans and with a plastic coating or paint for protection and decorative purposes
there are two types of steel tube welded and seamless for welded tube the basic
principle is to take flat steel strip or plate and form it into a cylinder either
by rolling or pressing before welding the edges together to make a seamless
tube you must first pour a hole through a hot billet either in a large press or
by rolling the billet through special piercing rolls the hollow billet is then
stretched over a bar which enables the interior of the tube to be sized for
both types of tube a final sizing operation can take place slightly
reducing the outside diameter to the required dimensions
so these are the processes used to manufacture steel the world's most
versatile material to ensure efficient safe operations and the production of
quality steels each of these processes use sophisticated computer control and
skilled operators complex logistics support steel manufacturing and the
distribution of finished products to customers around the world to meet the
needs of those customers there are thousands of different types of steel
each with different properties making them suitable for thousands of different
uses but it doesn't stop there new Steel's are being continuously
researched and developed to offer ever better properties to meet ever greater
demands and every year almost 400 million tons of steel around half of the
world's total production is made from recycled steel making it the world's
most recycled material from the Earth's crust comes the iron ore to make the
iron which makes the steel that shapes the world