Steel is basically an alloy of iron and carbon
with a small percentage of other metals such
as nickel, chromium, aluminum, cobalt,
molybdenum, tungsten etc. Steel is a hard
ductile and malleable solid and is probably
the most solid material after plastic and iron.
There are many different types of steel
classified on the basis of the type of metal
used and the percentage content of the
metal in the particular type of steel.
Types of steel
High carbon steel
Medium carbon steel
Simply composed of iron and carbon with a more percentage of carbon in it than
The presence of excess carbon makes this type of steel is softer than the other
types of steel which contain some percentage of other elements as well.
Mostly used in the making of wood cutting tools because they can be sharpened
easily. However it cannot be used in the making of tools used for the cutting of
hard substances because it is not hard enough for that purpose. It is also used in
the making of axes, swords, scissors and other cutting tools.
Mild carbon steel
The mild carbon steel just like the high carbon steel is simply composed of iron
and carbon but it has a very low content of carbon in it.
This steel is used in the making of vehicle frames, panels, boxes, cases and sheet
metal for roofs. It is now also used as a replacement for wrought iron in the
making railroad rails.
Medium Carbon Steel
The medium carbon steels have a normal content of carbon that means that they
are not as hard as the high carbon and neither are they as strong the Mild carbon
They are used in the making of tool frames and springs.
Stainless steel is the most resistant and commonly used steel of all the types. It
apart from carbon contains 11% chromium and some amount of nickel. It is
probably the most resistant steel of all the types.
Although all the types of steel are generally resistant to rust and corrosion, the
stainless steel in particular is resistant to any sort of external attack.
This steel is used in the making of crockery, wrist watches, kitchen utensils, cutlery
and surgical equipments.
High Speed steel
High speed steel is an alloy of steel which may consists of either of the following
metals: tungsten, cobalt, molybdenum or chromium.
High speed steel is probably the toughest of all the types.The term high speed is
given to it due to the fact that it has the ability to cut the metals.
Used in the making of drills and tools and power saws.
The hardness and rigidity of high speed steel depends on the metal used in the
making of the alloy and its percentage of composition in it.
Cobalt is much like the high speed steel with an excess of cobalt present in it.
It might not be as hard as the high speed steel is but it too can drill through
certain types of metals.The drill tools made of cobalt steel have a touch of brown
Nickel Chromium Steel
Nickel chromium steel is has is a special type of steel which is shock resistant
apart from being strong therefore it is commonly used as an armor plate.
Aluminum steel is smooth steel with a high content of aluminum. Because of
its strong and smooth surface it is used in the making of furniture.
Chromium steels have a high content of chromium and are resistant to
They are very strong tensile and are elastic in nature.They are used in the
making of Automobile and airplane parts.
It can be rolled into thin sheets, rod, bar,
or beams (roofing ,structural) or forged
into different shapes.
It can be stretched and drawn out into
thin wires (wire fences) or pressed into
It is very strong and resistant to fracture
(building frames, security doors, trains,
It is a long lasting material (buildings rail
line, bridges) and resistant to wear
(machines and equipment's).
Manufacturing processes of steel
Open hearth process
It is an industrial process for the manufacture of steel from molten
The principle involved is that of oxidation of the impurities in the
iron by the oxygen of air that is blown through the molten iron; the
heat of oxidation raises the temperature of the mass and keeps it
molten during operation.
The process is carried on in a large container called the Bessemer
converter, which is made of steel and has a lining of silica and clay or
At its narrow upper end it
has an opening through
which the iron to be
treated is introduced and
the finished product is
The wide end, or bottom,
has a number of
perforations through which
the air is forced upward
into the converter during
As the air passes upward
through the molten pig
iron, impurities such as
silicon, manganese, and
carbon unite with the
oxygen in the air to form
oxides; the carbon
monoxide burns off with a
blue flame and the other
impurities form slag.
Open hearth process -
Natural gas or atomized heavy oils
are used as fuel; both air and fuel are
heated before combustion.
The furnace is charged with liquid
blast-furnace iron and steel scrap
together with iron ore, limestone,
dolomite, and fluxes.
The furnace itself is made of highly
refractory materials such as
magnetite bricks for the hearths and
Capacities of open-hearth furnaces
are as high as 600 tons, and they are
usually installed in groups, so that
the massive auxiliary equipment
needed to charge the furnaces and
handle the liquid steel can be
Cementation process –
The cementation process is an
obsolete technique for
making steel by carburization of iron.
Unlike modern steelmaking it
increased the amount of carbon in
the iron .The process begins
with wrought iron and charcoal.
It uses one or more long stone pots
inside a furnace.. Iron bars and
charcoal are packed in alternating
layers, with a top layer of charcoal
and then refractory matter to make
the pot or "coffin" airtight.
Some manufacturers used a mix of
powdered charcoal, soot and
mineral salts, called cement powder. In
larger works up to 16 tons of iron
was treated in each cycle.
Depending on the thickness
of the iron bars, the pots
were then heated from
below for a week or more.
Depending on the
thickness of the iron bars,
the pots were then heated
from below for a week or
Bars were regularly
examined and when the
correct condition was
reached the heat was
withdrawn and the pots
were left until cool—usually
around fourteen days.
The iron had "gained" a
little over 1% in mass from
the carbon in the charcoal,
and had become
of blister steel
It is used to manufacture high carbon steel.
Fragments of blister steel or bars of pure wrought
iron are mixed with charcoal and heated in fire –
The molten steel is poured into moulds to prepare
Steel thus prepared is also known as Cast steel.
This steel is used for making surgical instruments,
files and superior quality cutlery.
This steel is hard and of homogenous quality.
This process is combination of acid Bessemer
process and basic open-hearth process.
Molten pig-iron is treated in acid lined Bessemer
converter to remove impurities like carbon, silica
The charge is then transferred to basic lined open
hearth furnace and impurities, such as sulphur and
phosphorus are removed.
In order to improve the quality of steel, further
duplex process may be extend toTriplex process.
The molten steel as obtained from basic lined open
hearth furnace is further treated in electric furnace.
L. D. PROCESS
In this process, pure oxygen is used in
place of blast of air.
The charge is put in L. D. converter and a
jet of oxygen is brown through the
High temperature in the converter burns
away the impurities and pure low carbon
steel is prepared.
A separate oxygen plant has to be established.
It is difficult to exercise control over the
It can’t handle all grades of pig – iron.
The basic difference in
this process and
Bessemer or open
hearth process is the
use of electricity for
melting and heating
It consist of a vessel
made steel plates and
lined with basic
The vessel is tiltable.
Electrodes are fitted in
the vessel and electric
arcs are developed, which
produce intense heat and
cause charge in the vessel
This method cannot be
used for manufacture of
steel on large scale as its
capacity is only about 10 –
15 tonnes. It is however,
useful for the manufacture
of special steel on small
There is no smoke, ash and as such need the
Temperature can be easily control.
Amount of slag formed is small.
It is very quick process.
• IN CONTEMPORERY ARCHITECTURE STEEL IS
FREQUENTLY EMPLOYED TO PROVIDE A
STRUCTURAL FRAME FOR A BUILDING.
•THIS SCULPTURE WAS DESIGNED AND
FABRICATED BY LEE, BRUCE AND BENITA
•THE BOAT LIKE SCULPTURE IS MADE FROM
32MM PLATE STEEL.
• ALL STEEL EDGES HAVE BEEN BEVELED.
•HIGH QUALITY FINISH AS MAJORITY OF STEEL
• STEEL HOT DIP GALVANIZED.
•ALL ROOF RAFTERS SITEWELDEDTO COLUMNS AND
CRANED INTO POSITION AS WHOLE UNIT.
• ONCE IN POSITION, COLUMNS SITEWELDED TO
PLATES CAST IN SLAB.