Steel is a versatile alloy of iron and carbon, classified into various types based on composition and production methods. Its properties can be modified by adjusting carbon content, affecting strength and ductility, and it has been historically developed from ancient techniques to modern processes like the Bessemer and basic oxygen steelmaking. Despite its advantages in construction, steel structures face challenges such as corrosion, buckling, and fireproofing costs.

2. PROTO-GERMANIC
Which means ‘standing firm’
Definition:
Steel is an alloy of IRON and CARBON and sometimes with other
elements like Mn,Cr,Ni…etc. It is a hard ,strong grey or bluish grey alloy
which is widely used as a structural and fabricating member.

3. Earliest  4000 years old  1800 BC 
Noric steel  Roman military
Pioneers of modern steel making
process6thcentury BC
“Tamilians of Tamilakam”
 Wootz steel  Seric IRON  Carbon content
from “Avaram Poo”heated
in crucibles

4. The CHINESE of the WARRING
states  quenched hardened
steel 403-221 BC
The Chinese of HAN dynasty
 created steel  by
melting wrought iron with
cast iron 202BC-220AD
Avaram poo – Cassia auriculata

5. Mainly into 4 types , based on it’s
composition:
1) CARBON steel
2)ALLOY steel
3)STAINLESS steel
4)TOOL steel
But providing a wide range of classification
:
 PRODUCTION METHOD :
Continuous cast, elastic furnace…etc
Source: www.metasupermarkets.com

6.  FINISHING METHOD:
Cold rolled, hot rolled, cold
drawn…etc
 FORM OR SHAPE:
Bar, Rod, tube, pipe, plate,
sheet…etc
 DE-OXIDATION PROCESS:
Killed and semi killed steel…etc
 MICROSTRUCTURE:
Ferritic, Pearlitic, Martensitic…etc
 HEAT TREATMENT: Source: www.metasupermarkets.com

7.  Properties of STEEL can be varied by
VARYING the CARBON content in it.
 Increase in carbon content increases
the SHEAR STRESS and HARDNESS, at
the same time decreases the
DUCTILITY and TOUGHNESS.
 Composition : 0.05% - 2.1% of
Carbon
 Melting point : 1300-1400 C
 Can be hardened and tempered

8.  Compressive strength : 4.75 – 25.2
tonnes/sq.m
 Ultimate tensile strength : 5.51-11.02
tonnes/sq.m
 It rusts easily
 It’s TOUGH , Mallaeble and Ductile
 It absorbs SHOCKS
 It can be rapidly forged or welded
Commonly USED as a REINFORCEMENT for
RCC , in Steel structures, bolts, rivets and
sheets. For making cutlery, files and

9. Based on the carbon content steel is of
the following types:
 Dead Mild Steel ( less than 0.15% of C)
 Mild Steel (0.05-0.25% of C)
 Medium carbon steel (0.30-0.60% of
C)
 High carbon steel (0.60 – 1.50% of C)
 Cast steel or Carbon steel ( more than
1.50%)

10.  Also known as PLAIN CARBON steel
 Most common form of steel
 Material properties acceptable for many
applications
 CARBON CONTENT : 0.05 – 0.25 %
 DENSITY : 7850 kg/m3 (or)
7.85 g/cm3
 YOUNG’S MODULUS: 210 Gpa or
30,000,000psi

11. Characteristic STRESS-STRAIN curve for MILD
STEEL
As per Indian Standards(IS)
2062, there are 9 mild steel
grades as :
 Fe 250
 Fe 275
 Fe 300
 Fe 350
 Fe 410
 Fe 450
 Fe 550
 Fe 600
 Fe 650
Where NUMBER denotes the
value ofTENSILE STRENGTHS
of the variant.

12.  Carbon content : 0.3% - 0.6%
 Manganese content : 0.60% -
1.65%
 Ductile
 Strong
 Long wearing properties
 USES : Large parts of
machinery, forging
and automotive

13.  Carbon content : 0.60% -
1.70%
 Manganese content : 0.30% -
0.90%
 High CARBON content STRONG
 Holds SHAPE MEMORY well
 Uses : Springs , swords,
high strength wires
and sheets…etc

14. Cold Twisted Deformed(CTD) Bars
commonly known as TOR steel
named after TORisteg Steel
Corporation of LUXEMBORG – 1975
Thermo Mechanically Treated
(TMT) :
Hard outer surface with a
softer core. ManufacturedHot
rolled steel wires Water
Surface harder and core softer

15.  Steel wasn’t made economically till 19th
century
 Began in 1855 Introduction of
BESSEMER’S PROCESS
 Raw material PIG iron  Bessemer
converter
 CHEAP and produced LARGE quantities
Bessemer converter - 1855

16.  19th century  SIEMENS-MARTIN
process  co-melting of bar
iron with pig iron
Open hearth furnace

17.  Linz-Donawitz process of BASIC
OXYGEN STEEL (BOS) making 
developed in 1950’s  superior
to all
SOURCE:
Hyundai steel
corporation
web

18. Source : DISCOVERY channel

19.  High Strength and Light weight :
Weight of structure made of steel will
be small
 Uniformity :
Properties of Steel does not change as
opposite to concrete.
 Elasticity:
Steel follows Hooke’s law accurately
 Ductility:
Steel can withstand extensive
deformation without failure under
high tensile stress (ie) it gives WARNING
before failure takes place.
 Toughness :
Steel has both STRENGTH and
Burj
Khalifa
,
Dubai

20. Sometimes R/C structures are preferred to steel structures because
sometimes steel structures cannot provide the necessary strength due to
BUCKLING, whereas R/C columns are generally sturdy and massive (ie) no
buckling occurs.
The other disadvantages maybe:
Maintenance Cost : Steel structures
 Corrosion  Air,water & Humidity
 Painted regularly
Fire proofing cost:
SteelIncombustible  But at HIGH
temperatures Strength reduced

21.  Susceptibility to Buckling :
As the length and slenderness of a
compressive column increases, the
danger of buckling increases.
 Fatigue :
Strength of Steel gets reduced due
to cyclic loading(ie) repeated loading in
regular time intervals
 Brittle fracture:
Under certain conditions Steel
loses DUCTILITY Fracture Stress
concentrated areas  Fatigue type

22. Howrah Bridge Pamban Bridge

23. Chennai Airport Bengaluru International
Airport

24. Wankhede Cricket stadium Chennai Chepauk
CricKet Stadium

25. Petronas Towers
The Empire State
Building

26. Eiffel Tower Burj Khalifa Sears Towers
Taipei 101

27. National Olympic stadium- China Golden Gate
Bridge-SF

28. The LOUVRE
pyramid,
Paris

29. Disney Concert Hall, Los Angeles Montreal Biosphere -
Fuller