introduction of steel making types , classification

What is Steel ?
• Steel is an alloy of iron and carbon containing less than
2% carbon and 1% manganese with some other
alloying element like Cu, Cr, Mo , V , W ,Ti , Si ,
Ni, P, etc.
STEEL : IRON+CARBON+ALLOYING ELEMENT

• Steel is the world’s most important engineering and
construction material. It is used in every aspect of our
lives; in cars and construction products, refrigerators
and washing machines, cargo ships and surgical
scalpels.

Why we choose steel ?
• Easy to design for architect
• Durability
• Strength
• Fire Safety
• Sustainability
• Energy Efficiency
• Economic Value
• Adaptability & Reuse

• Steel is completely recyclable, possesses great durability,
and, compared to other materials, requires relatively low
amounts of energy to produce. Innovative lightweight steels
(such as those used in in automobiles and buidlings) help to
save energy and resources. The steel industry has made
immense efforts to limit environmental pollution in the last
decades. Producing one tonne of steel today requires just
40% of the energy it did in 1960. Dust emissions have been
reduced by even more.

Why does steel rust?
• Many elements and materials go through chemical reactions
with other elements. When steel comes into contact with
water and oxygen there is a chemical reaction and the steel
begins to revert to its original form – iron oxide.
• In most modern steel applications this problem is easily
overcome by coating. Many different coating materials can be
applied to steel. Paint is used to coat cars and enamel is
used on refrigerators and other domestic appliances. In other
cases, elements such as nickel and chromium are added to
make stainless steel, which can help prevent rust.

Who invented steel?
• A British inventor, Henry Bessemer, is generally
credited with the invention of the first technique to mass
produce steel in the mid 1850s. Steel is still produced
using technology based on the Bessemer Process of
blowing air through molten pig iron to oxidise the
material and separate impurities. For more information,
check out our White Book of Steel available from the
column on the right of this page.

Can steel be recycled ?
• Yes, very easily. Steel’s unique magnetic properties
make it an easy material to recover from the waste
stream to be recycled. The properties of steel remain
unchanged no matter how many times the steel is
recycled.
• The electric arc furnace (EAF) method of steel
production can use exclusively recycled steel. The blast
furnace-basic oxygen furnace (BF-BOF) route can use
up to 30% recycled steel.

How much steel is produced in a year ?
• World crude
steel
production
reached 1,950
.5 million
tonnes
(Mt) for the
the year 2021.

How steel is made?
• Steel is produced via two main routes: the blast furnace-basic
oxygen furnace (BF-BOF) route and electric arc furnace (EAF)
route. Variations and combinations of production routes also
exist.
• The key difference between the routes is the type of raw
materials they consume. For the BF-BOF route these are
predominantly iron ore, coal, and recycled steel, while the EAF
route produces steel using mainly recycled steel and electricity.
Depending on the plant configuration and availability of
recycled steel, other sources of metallic iron such as direct-
reduced iron (DRI) or hot metal can also be used in the EAF
route.

• A total of around 70% of steel is produced using the BF-BOF
route. First, iron ores are reduced to iron, also called hot metal or
pig iron. Then the iron is converted to steel in the BOF. After
casting and rolling, the steel is delivered as coil, plate, sections
or bars.
• Steel made in an EAF uses electricity to melt recycled steel.
Additives, such as alloys, are used to adjust to the desired
chemical composition. Electrical energy can be supplemented
with oxygen injected into the EAF. Downstream process stages,
such as casting, reheating and rolling, are similar to those found
in the BF-BOF route. About 30% of steel is produced via the EAF
route.

The steel can be divided into two major parts-
1) Plain Carbon Steel
2) Alloy Steel

1)Plain Carbon Steel:
Plain Carbon Steel are essentially alloy of iron and
carbon only.
2)Alloy Steel:
Alloy Steel is an alloy of iron and carbon with some
other alloying element like Cu, Cr, Mn W, Ti , Mo , Ni, Si
etc to ensure specific better properties such as
mechanical strength, ductility, electrical and magnetic
properties, corossion resistance and so on.
Hot Metal: 92-94%Fe
Steel: 99%Fe

PLAIN CARBON
STEEL
(% OF CARBON)
LOW CARBON STEEL
(0.15- 0.35% C)
MEDIUM CARBON
STEEL(0.35- 0.65% C)
HIGH CARBON STEEL
(0.65- 1.75% C)
ALLOY STEEL
( % OF ALLOYING
ELEMENTS)
LOW ALLOY STEEL
(UPTO 5%)
MEDIUM ALLOY STEEL
( 5- 10% )
HIGH ALLOY STEEL (
MORE THAN 10% )
Classification of steel
Ultra low carbon
(C reduced upto
0.002%)

1. Classification of Plain Carbon Steel:
*Low Carbon Steel ~ Upto 0.35%C
*Medium Carbon Steel ~ 0.35-0.65%C
*High Carbon Steel ~ 0.65-1.75%C
*Ultra Low Carbon Steel ~ C reduced Upto 0.002%C
*Mild Steel ~ 0.16-0.25%C
2. Classification of Alloy Steel:
*Low Alloy Steel ~ Upto 5% alloying element
*Medium Alloy Steel ~ 5-10% alloying element
*High Alloy Steel ~ 10-15% alloying element

Steel Making:
Steel Making is a Melting, Purifying and alloying
process carried out at approximately 1600°C in
molten state.
Various chemical reactions are initiated either in
sequence or simultaneously in order to arrive at
specific chemical composition and temperature.
STEEL MAKING: MELTING + PURIFYING + ALLOYING

Principle of Steel Making:
*Steel Making is a refining or oxidation process with exception of
reducing conditions being specially required to eliminate sulphur.
*Being an oxidation process, steel making needs a source of
oxidising agent.
*The oxygen in the form of atmospheric air or iron oxide in the
form of iron ore and mill scale ( oxide produced during hot
working of steel). Mill Scale – Feo(wustite)
*The conventional method of steel making used either or both
of these reagent.
*Modern Steel Making process used pure oxygen.

The following reaction takes place during
refining process –
2[Fe] + 𝑂2 2(FeO)
[Si] + 𝑂2 (Si𝑂2)
2[C] + 𝑂2 2{CO}
[C] + 𝑂2 {C𝑂2}
2[Mn] + 𝑂2 2(MnO)
4[P] + 5𝑂2 2(𝑃2𝑂5)
[S] + CaO (CaS) +[O]
Oxidation Reaction
[O] Nascent Oxygen , Removal of P High Basicity

*Except the sulphur reaction, all the rest are
oxidation process and are favoured under the
oxidising condition of steel making.
*In case of oxidation of carbon, the product
being a gas passes into the atmosphere. But the
rest of the oxide product shall remain in contact
with the iron melt in the form of slag phase.
Hot metal – 1300-1450°C
Steel – 1600-1650°C
All reaction are exothermic reaction in steel
making

Raw Material For Steel Making-
1. Iron Bearing Material:
a) Hot Metal
b) Steel Scrap
c) DRI
d) Pig Iron
2. Flux:
a) Lime – CaO
b) Dolomite - CaC𝑂3MgC𝑂3
c) Fluorspar - Ca𝐹2(Fluidity)
3. Oxidising agent:
a) Air
b) Pure 𝑂2
c) Iron Oxide (hematite ore, mill scale)

Classification of steel making
process
Pneumatic
process
Bessemer
Open hearth
process
Acid open
hearth process
Basic open
hearth process
Electric arc
furnace
Conventional
and modern
BOF steel
making
process
Straight LD
Hybrid LD

1856
ACID
BESSEMER
1879
BASIC
BESSEMER
OPEN
HEARTH
1868
ELECTRIC
ARC
PROCESS
1899
1952
BOF
PROCESS
HISTORY OF STEEL MAKING PROCESS

introduction of steel making types , classification

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