Unit 3.ppt

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1. METALLURGY

2. Unit 1II:
Ferrous Metals and
Designation

3. In this unit we are going to study:
Allotropy of Iron
Iron-iron carbide diagram
Plain carbon steels
Limitations of plain carbon steel
Unit 3: Ferrous metals and Designation

4. In this unit we are going to study:
Alloy steels
Advantages of alloy steels
Effect of alloying elements on
mechanical
properties of steel
Tool steels
Stainless steels
Cast irons
Designation of steels and cast iron
Unit 3: Ferrous metals and Designation

5. What is steel?
Steel is a interstitial solid solution of
iron and carbon containing 0.008 to
2% carbon by weight
Unit 3: Ferrous metals and Designation

6. local atomic fluctuation
formation of many small
nuclei
growth of nuclei with
critical size or greater
•Homogeneous nucleation: occurs within a homogeneous medium.
•Heterogeneous nucleation: nucleation occurs at some structural
imperfection such as foreign surface, and hence with reduced surface
energy
Unit 3: Ferrous metals and Designation

7. 7
Solid Solutions

8. 8
Solid Solutions

9. 
Allotropy of Iron

10. 910
0
C
1400
0
C
1539
0
C
Temp
Time

11. Allotropy of Iron

12. Phases in Steel
α-ferrite
Interstitial solid solution of carbon dissolve in
α-iron having BCC structure.
Maximum solubility of carbon in α-iron is
0.02% (at 727
0
C)
At room temperature solubility is 0.008%

13. Phases in Steel
Properties of α-ferrite
Soft and ductile phase
Ferromagnetic upto curie temperature(768
0
C)
Tensile Strength 40,000psi
Elongation 40% (2in GL)
Hardness 80 BHN
Toughness Low

14. Phases in Steel
Microstructure of α-ferrite

15. Phases in Steel
Austenite (γ)
Interstitial solid solution of carbon dissolve in
γ-iron having FCC structure.
Maximum solubility of carbon in γ-iron is 2.%
(at 1147
0
C)
Stable only above 727
0
C

16. Phases in Steel
Properties of Austenite
Soft and ductile phase
Non magnetic
It can be extensively worked at the temperature
of its existence.
Tensile Strength 1,50,000psi
Elongation 10% (2in GL)
Hardness Rc 40
Toughness High

17. Phases in Steel
Microstructure of Austenite

18. Phases in Steel
δ-ferrite
Interstitial solid solution of carbon dissolve in
δ-iron having BCC structure.
Maximum solubility of carbon in δ-iron is
0.1% (at 1492
0
C)
Stable only above 1400
0
C

19. Phases in Steel
Iron Carbide (Cementite)
Intemetallic compound of iron and carbon
with fixed carbon content of 6.67% and having
orthorhombic structure.
Chemical formula Fe
3C
Metastable phase

20. Phases in Steel
Properties of Iron Carbide
(Cementite)
Extremely hard and brittle phase
Ferromagnetic upto 210
0
C
Tensile Strength 5000psi
Elongation 1%
Hardness 900-1200 VHN
Toughness Very Low
Compressive StrengthVery High

21. Transformations
Peritectic reaction:
S1 + L S2
Eutectic reaction:
L S1 + S2
Eutectoid reaction:
S1 S2 + S3
9-5

22. Transformations
Peritectic reaction:
General Reaction:
S1 + L S2
Reaction in steel:
Liquid + δ γ
0.55%C 0.1% C 0.18% C
BCC FCC
9-5
1492
0
C
Cooling

23. Transformations
Eutectic reaction:
General Reaction:
L S1 + S2
Reaction in steel:
Liquid γ + Fe
3C
4.3%C 2% C 6.67% C
FCC Orthorhom
9-5
1147
0
C
Cooling

24. Transformations
Eutectoid reaction:
General Reaction:
S1 S2 + S3
Reaction in steel:
γ α+ Fe
3C
0.8%C 0.02% C 6.67% C
FCC BCC Orthorhombic
9-5
727
0
C
Cooling

25. Eutectoid reaction:
γ α+ Fe
3C
0.8%C 0.02% C 6.67% C
FCC BCC Orthorhombic
This eutectoid mixture is called Pearlitedue to its pearly
appearance under microscope.
Pearlite:It is a eutectoid mixture of alpha ferrite
and cementite formed from austenite containing
0.8%C while cooling at 727
0
C
9-5
727
0
C
Cooling

26. Phases in Steel
Properties of Pearlite
Good Hardness and T.S.
magnetic
Tensile Strength 1,20,000psi
Elongation 20% (2in GL)
Hardness Rc 20 (250 BHN)
Toughness High

27. Phases in Steel
Microstructure of Pearlite

28. Microstructure of Pearlite
Phases in Steel

29. Microstructure of Pearlite

30. Phases in Steel
Microstructure of Pearlite
Laminar (Platelike) or Fingerprint Microstructure
Ferrite (white)
Cementite
(dark)

31. Cooling of Eutectoid Steel (0.8% C)

32. Off Eutectoid Steels
Steels with compositions between
0.008 to 0.8 wt% Carbon are
hypoeutectoidsteels.
Steels with compositions between
0.8 to 2 wt% Carbon are
hypereutectoidsteels

33. 33
Fe
3
C (cementite)
1600
1400
1200
1000
800
600
400
0 1 2 3 4 5 66.7
L
g
(austenite)
g+L
g+Fe
3C
a+Fe
3C
L+Fe
3C
d
(Fe) C, wt% C
1148°C
T(°C)
a
727°C
C
0
0.76
a
pearlite
g
gg
g
a
a
a
gg
g
g
g
g
gg
Cooling of Hypoeutectoid Steel (0.8% )
Hypoeutectoid Steels

34. 34
Proeutectoid α-ferrite
Formed before the eutectoid
Ferrite that is present in the pearlite is called eutectoid ferrite.
The ferrite that is formed above the T
eutectoid(727°C) is proeutectoid.
Cooling of Hypoeutectoid Steel (0.8% )

35. Fe
3
C (cementite)
1600
1400
1200
1000
800
600
400
0 1 2 3 4 5 66.7
L
g
(austenite)
g+L
g+Fe
3C
a+Fe
3C
L+Fe
3C
d
(Fe) C, wt%C
1148°C
T(°C)
a
0.8
Fe
3C
gg
g
g
gg
g
g
gg
g
g
pearlite
Cooling of Hypereutectoid Steel (0.8% )
Hypereutectoid Steels

36. Proeutectoid Cementite
Cooling of Hypereutectoid Steel (0.8% )

37. Hypereutectoid Steel (0.8% )
Microstructure of Hypereutectoid Steel

39. The Lever rule
Amount of phase 1 = (C2 -C) / (C2 -C1)
Amount of phase 2 = (C -C1) / (C2 -C1).
If an alloy consists of more than one phase, the amount of each phase present
can be found by applying the lever rule to the phase diagram.
The composition of the alloy is represented by the fulcrum,
and the compositions of the two phases by the ends of a bar.

40. Ex.1:For eutectoid steel determine amount of
alpha ferrite and cementite just below the
eutectoid temperature
Numerical Examples

41. Solution:
Eutectoid steel means 0.8%C steel
Co=0.8
Cα=0.02
C
Fe3C=6.67
(a)Amount of alpha
Ferrite
=(6.67-0.8)/(6.67-0.02)
=88.27%
(b) Amount of Cementite
=(6.67-0.8)/(6.67-0.02)
=11.72%

42. Numerical Examples
Ex.2:For peritectic steel determine amount of
delta ferrite and austenite just below the
peritectic temperature
Ex.3:For eutectic cast iron determine amount of
austenite and cementite just below the
eutectic temperature
Ex.4: Find the maximum amount of
proeutectoid cementite in any steel.

43. Ex.5:For 0.40 % C steel at a temperature just
below the eutectoid, determine the
following
a)Amount of pearlite and proeutectiod ferrite
(a)
b)the amount of cementite
Numerical Examples

44. Solution:
(a)The amount of pearlite
=(0.4 –0.02) /( 0.8 -0.02) x 100
=48.71%
(b)Amount of
proeutectoid ferrite
=(0.8-0.4 )/ (0.8 -0.02) x 100
=51.28%
(c)Amount of Cementite
=(0.4-0.02)/(6.67-0.02) x 100
=5.7%
C
O= 0.40 wt% C
C
a
= 0.02 wt% C
C
p
= 0.8 wt% C
Fe
3
C (cementite)
1600
1400
1200
1000
800
600
400
0 1 2 3 4 5 66.7
L
g
(austenite)
g+L
g+Fe
3C
a+Fe
3C
L+Fe
3C
d
C
o, wt% C
1148°C
T(°C)
727°C
C
O
R S
C
Fe C
3
C
a

45. Ex.5:For 1.1 % C steel under equilibrium
conditions determine the following:
a)Amount of austenite and proeutectiod
cementite just above eutectoid temp.
b)Amount of pearlite and proeutectiod
cementite and total cementite at room
temperature.
Numerical Examples

46. Ex.6:A slowly cooled steel contains 10% proeutectoid
ferrite at room temperature. Determine the
amount total ferrite and cementite present in the
alloy.
Ex.7:A slowly cooled steel contains 60% ferrite and
40% pearlite at room temperature. Determine the
amount of pearlite, total ferrite and cementite
present in the alloy at the temperature just below
eutectoid temperature.
Numerical Examples

47. Critical Temperatures in
Iron-Iron Carbide Equilibrium Diagram
S.
N.
Critical
Points
Temp Significance During Heating
1A
0 210
0
C Cementite becomes
paramagnetic
2A
1 727
0
C Perlite Austenite
3A
2 768 Ferrite becomes
paramagnetic
4A
3 727-
910
0
C
Completion of
Ferrite Austenite
5Acm 727-
1147
0
C
Completion of
Cementite Austenite

48. Critical Temperatures in
Iron-Iron Carbide Equilibrium Diagram
S.
N.
Critical
Points
Temp Name of Critical Temperature
1 A
0 210
0
C Curie Temperature of Fe
3C
2 A
1 210
0
C Lower Critical Temperature
3 A
2 768 Curie Temperature of Ferrite
4 A
3 727-910
0
CUpper Critical Temperature for
Hypoeutectoid Steel
5 Acm 727-
1147
0
C
Upper Critical Temperature for
Hypereutectoid Steel

49. Property Variation With Microstructure
Mechanical properties are structure sensitive
Mech Properties= f (Types of phases, amount of
phases and morphology of
structure)
Morphology means distribution of phases
For two phase alloy with α-βstructure, the property on an
average can be expressed as(when morphology is
insignificant):
Average property=
Amount of αx property of α
+ Amount of βx property of β

50. Property Variation With Microstructure
Since hardness is less sensitive to morphology.
For hypoeutectoid steels:
Hardness (BHN) =
Amount of α-ferrite x Hardness of of α-ferrite
+ Amount of pearlitex Hardness of pearlite
= Amount of α-ferrite x 80 BHN
+ Amount of pearlite x 230BHN

51. Property Variation With Microstructure
Since hardness is less sensitive to morphology.
For hypereutectoid steels:
Hardness (BHN) =
Amount of Fe
3Cx Hardness of of Fe
3C
+ Amount of pearlitex Hardness of pearlite
= Amount of Fe
3C x 900+
Amount of pearlite x 240

52. Property Variation With Microstructure
Many of the mechanical properties like T.S., ductility,
toughness are very sensitive to morphology. Hence,
unless the distribution of phases are not known
correctly, property prediction can not be done
accuratly.
For hypoeutectoid steels:
Since phases are well distributed in
hypoeutectoid steels T.S. is less sensitive to
morphology.
T.S. (psi)
= Amount of α-ferrite x 40000 psi
+ Amount of pearlite x 1,20,000 psi

53. Property Variation With Microstructure
For hypoeutectoid steels:
T.S. (kg/mm
2
)
= Amount of α-ferrite x 28 kg/mm
2
+ Amount of pearlite x 84 kg/mm
2
= (1-%C/0.8) x 28 kg/mm
2
+ ( %C/0.8) x 84 kg/mm
2
T.S. of hypoeutectoid steel increases by
7kg/mm
2
for every 0.1%C rise.
T.S. (kg/mm
2
)=0.36 X BHN

54. Property Variation With Microstructure
%C
Property
Hardness
T.S.
Ductility
0.8 2.0
350 BHN
84 kg/mm
2
230 BHN
10%
80 BHN
28 kg/mm
2
40%
0.4 1.2

55. Non Equilibrium Cooling of
Steels

56. Non Equilibrium Cooling of
Steels
Non-equilibrium cooling means cooling faster
than equilibrium cooling.
Faster cooling lowers all transformation
temperatures
Eutectoid point shift towards left side for
hypoeutectoid steel and towards right for
hypereutectoid steel
Amount of proeutectoid phase decreases and
amount of pearlite increases
Pearlite becomes finer.

57. Why Solubility of Carbon in Austenite is Very
High?
Austenite, being FCC have four atoms per unit cell
Ferrite, being BCC have two atoms per unit cell
Empty space in FCC Austenite=25%
Empty space in BCC Ferrite=32%
This means Austenite have much denser packing of
atoms than ferrite.
Still Solubility of Carbon in Austenite (2%) is very
high compare to Ferrite (0.02).

58. Why Solubility of Carbon in Austenite is Very
High?
Reason:
The largest interstitial sphere that would just fit in
BCC cell has radius of 0.36 x 10
-8
cm
The largest interstitial sphere that would just fit in
FCC cell has radius of 0.52x10
-8
cm

59. Why Solubility of Carbon in Austenite is Very
High?
α-ferrite
BCC
Radius
=0.36x 10
-8
cm

60. Why Solubility of Carbon in Austenite
is Very High?
Austenite
FCC
Radius
=0.52 x 10
-8
cm

61. Classification of Steels
Steels are classified base on various
criterions:
Amount of carbon
Amount of alloying elements
Amount of deoxidation
Grain Coasening Characteristics
Method of Manufacturing
Depth of Hardening
Form and use

62. Classification of Steels
Amount of carbon
Low carbon steel
(0.008 –0.3 %C)
Medium carbon steel
(0.3 –0.6 %C)
High carbon steel
(0.6 –2 %C)

63. Classification of Steels
Amount of carbon
Low carbon steel
Soft
ductile
malleable
tough
machinable
weldable
non hardenable by heat treatment

64. Classification of Steels
Applications of Low carbon steel
Good for cold working such as rolling into thin sheets
Good for fabrication work by welding, pressing or
machining
Used for wire, nails, rivets, screws, panels, welding rod,
ship plates, boiler plates, tubes for bicycles and
automobiles
Steels with o.15 to 0.3 %C are widely used as Structural
steelsand used for building bars, grills, beams, angles,
channels etc.
Mild Steel is well known from this group

65. Classification of Steels
Medium carbon steel
Medium Soft
Mediumductile
Mediummalleable
Mediumtough
Depth of hardening is less
Slightly difficult to machine, weld and
harden
Difficult to cold work
They are also called as machinery
steels

66. Classification of Steels
Applications of medium carbon steel
Used for
Bolts
Axles
Lock washer
Forging dies
Springs
Wheel Spokes
Railway rails

67. Classification of Steels
High carbon steel
Hard
Wear Resistant
Brittle
Difficult to cold work
Very difficult to machine and weld
Depth of hardening is more
They are also called as Tool Steels

68. Classification of Steels
Applications of high carbon steel
Used for
Dies
Punches
Hammers
Chisels
Drills
Metal cutting saws
Razor blades

69. Classification of Steels
On the basis of alloying elements
Low alloy steels
(Total alloying elements are less than 10%)
High alloy steels
(Total alloying elements are more than 10%)

70. Classification of Steels
On the basis of alloying elements and
carbon content
Low carbon Low alloy steels
Low carbon High alloy steels
Medium carbon Low alloy steels
Medium carbon High alloy steels
High carbon Low alloy steels
High carbon High alloy steels

71. Classification of Steels
On the basis of deoxidation
Rimmed steels
Killed steels
Semi-killed steels

72. Classification of Steels
On the basis of deoxidation
A molten steel contains large amount of dissolved
oxygen and other gases.
The solubility of gases is more in the liquid metal than
in the solid metal and hence the dissolved oxygen along
with other gases tries to go out as CO during
solidification and a large part of it gets entrapped into
solidified ingot.
Rimmed steels
In rimmed steels no treatment is given to dissolved
gases.
The tapped gases form blow holes which compensate
for the usual liquid to solid shrinkage.

73. Classification of Steels
On the basis of deoxidation
Rimmed steels
The thin solidified layer of ingot i.e. rim (skin)
formed at surface which contains low carbon, less
impurities and no blow holes
These steels coarsen rapidly during heating in
austenitic region.
Generally low carbon steels containing less than
0.15% carbon are produced in sheet form in
rimmed condition and used for deep drawing and
forming operations.

74. Classification of Steels
On the basis of deoxidation
Rimmed steels

75. Classification of Steels
On the basis of deoxidation
Killed steels
The dissolved oxygen from the melt is completely
removed by addition of strong deoxidising agents
like Al, Si, Mn and V.
The deoxidisers are added to the steel in the
furnace prior to pouring into mould.
They rapidly combine with the dissolved oxygen
and form respective oxides thus reduces dissolve
oxygen.
Killed steel shows more shrinkage (called as pipe)
during solidification due to absence of blow holes.

76. Classification of Steels
On the basis of deoxidation
Killed steels

77. Classification of Steels
On the basis of deoxidation
Killed steels
Killed steels shows fined grain characteristics
since oxide inclusions which inhibits the grain
boundary migration
Killed steel ingot has sound , defect free, less
segregated structure throughout the cross section
Usually high carbon steels and alloy steels are
produced in the killed condition.

78. Classification of Steels
On the basis of deoxidation
Semi-killed steels
In these steels part of the dissolved oxygen is
removed by addition of deoxidisers.
Blow holes formed compensate for part of the
shrinkage and hence pipe is less.
They show intermediate grain coarsening
characteristics.
Usually steels containing carbon between 0.15 to
0.25% are produced.

79. Classification of Steels
On the basis of Grain Coarsening
characteristics
During heating,100 % austenite is formed at just above
the upper critical temperature and the grains are of
smallest size. As the temperature increases above this,
the grain size may increase. Depending on the grain
coarsening characteristics, steels are classified into two
types as :
Coarse grained steels
Fine grained steels

80. Classification of Steels
On the basis of Grain Coarsening
characteristics
Coarse grained steels
Coarse grained steels coarsen rapidly with temperature.
Fine grained steels
These steels maintain a relatively fine and uniform grain size
even after holding for long time at high temperature. Fine
grained steels do not coarsen up to a definite temperature.
Above this temperature, they coarsen very fast and may
reach a size greater than those of coarse grained steels.

81. Classification of Steels
On the basis of Grain Coarsening
characteristics
Temperature
Austenitic Grain Size
700 800 900 1000 11001200
Coarse Grained Steels
Fined Grained Steels

82. Classification of Steels
On the basis of Grain Coarsening
characteristics
Usually rimmed steels behave coarse grained
steels.
Killed steels and alloy steels behave fine grained
steels.
The oxide inclusions in killed steels and
undissolved alloy carbides in alloy steels inhibit
the grain boundary migration, thus reducing grain
coarsening.
In the absence of such particles, grain
coarsening is rapid.

83. Classification of Steels
On the basis of Method of Manufacuring
Basic open hearth
Acid open hearth
Acid Bessemer
Basic oxygen process
Electrical Furnace

84. Classification of Steels
On the basis of Depth of Hardening
Non-hardenable
Can’t be hardened by quenching
Shallow hardening steels
hardened by quenching up to a small
depth
Deep hardening steels
hardened by quenching deeply

85. Classification of Steels
On the basis of Depth of Hardening
Non-hardenable
Very low hardenablilty
Low carbon steels with no alloying elements
Shallow hardening steels
Medium hardenability
Medium carbon steels with low alloying
elements
Deep hardening steels
High hardenability
High carbon steels with high alloying
elements

86. Classification of Steels
On the basis of form and us
Based on form:
Cast steels
Wrought steels
Based on Use:
Boiler steels
Case hardening steels
Corrosion and heat resistant steels
Deep drawing steels
Electrical steels
Free Cutting steels
Machinery steels
Structural steels
Tool steels

87. Specification of Steels
Steels are specified on the basis of
criteria like:
Chemical Composition
Mechanical Properties
Method of manufacturing
Heat Treatment
Quality
Majority of specifications are based
on chemical composition.

88. Specification of Steels
Standard practiced for specifying steels in
India are:
IS: Indian Standard
AISI: American Iron and Steel Institute
SAE: Society for Automotive Engineers
BIS: British Institute of Standards
In addition to above every country has its own
specification system e.g.
DIN:Germany
JIS : Japan
GHOST : Russia

89. Specification of Steels
However, attempts are being made
to uniquely identify material by a
numbering system such as UNS(Unified
numbering System) by initiative of AISI
and SAE.

90. Specification of Steels
Indian Standard Designation
System:
Indian standard code for designation of steel
was adopted by Indian standard Institution (ISI)
in 1961.
Indian specifications are based on
Mechanical Properties
Chemical Composition

91. Specification of Steels
Indian Standard Designation System:
Code designation on the basis of Mech
properties is based upon T.S. and Y.S.
Property Symbol
T.S. (N/mm
2
) Fe
T.S. (Kg/mm
2
) St
Y.S. (N/mm
2
) FeE
Y.S. (Kg/mm
2
) StE

92. Indian Standard Designation System:
Designation of steels on the basis of chemical
composition consists of numerical figure
indicating 100 times the average % of carbon
content.
Alphabets are prefixed to identify type of
steels of various class
Letters C or T is followed by figure indicating
10 times the average % of Mn content
Symbols S,Se,Te,Pb or P are used to indicate
free cutting steels followed by a figure indicating
100 times the percent content of the respective
element.

93. Indian Standard Designation System:
Alphabets are prefixed to identify type of steels
of various class:
Type of Steels Prefix Used
For plain carbon steels C
For high alloy steels X
For low alloy steels -
For Plain carbon tool steels T
For alloy tool steels XT
For Wrought steel S
For Cast steel CS

94. Indian Standard Designation System:
Alloy steels are designated in the symbolic form on the
basis of their alloy content by first specifying the average
content of carbon, followed by the chemical symbols of
the significant elements in the descending order of of
percentage content
If the average alloy content is upto 1%, the index
number is expressed upto 2 decimal places underlined
by a bar
If the alloy content is between 1 and 10% the index
number is rounded to the nearest whole number
If two or more significant alloying elements have same
alloy content, the chemical symbols are grouped
together followed by alloy content

95. Indian Standard Designation System:
S.
N.
Steel Specification
1 Fe410K
2 St42
3 FeE270
4 C20
5 C40
6 25C5
7 80T11
8 15Ni13Cr1Mo12
9 35S18
1035Mn1S18

96. Indian Standard Designation System:
S.
N.
Steel Specification
11T75W18Cr4V1
12T105Cr1Mn60
13T85W6Mo5Cr4V2
14T35CrMo1V30

97. AISI/SAE Designation System
American Iron and Steel Institute and Society of
Automotive Engineers, London have almost similar
method of designation of steel and is based on the
chemical composition of steel.
The method consists of designating the steel with four
or five numerical digits. The first digit from left indicates
the types of steels as follows:
DigitTypes of Steels
1 Carbon Steels
2 Ni Steels
3 Ni-Cr Steel
4 Mo Steels
DigitTypes of Steels
5 Cr Steels
6 Cr-V Steels
7 Tungsten Steels
8 Ni-Cr-Mo Steels
9 Si-MnSteels

98. AISI/SAE Designation System
For simple alloys, the second digit indicates the approximate % of
the predominant alloying elements and for othera it indicates
modification of the alloy in that group.
The last two or three digits divided by 100 usually the average %
carbon in the steel.
In addition to the numerals, AISI specification may include a letter
prefix to indicate the manufacturing process of that steel as below:
Letter Manufacturing Process
A Basic open hearth alloy steel
B Acid bessemer carbon steel
C Basic open hearth carbon steel
D Acid open hearth carbon steel
E Electric furnace steel

99. AISI/SAE Designation System
Some Important AISI/SAE steel designation groups
S.
N.
Details of the steelAISI/SAE Group
1 Carbon Steels
(i)Plain carbon
(ii)Free Cutting Steel
(iii)Manganese Steel
1XXX
10XX
11XX , 12XX
13XX
2 Nickel Steels
(i)0.5% Ni
(ii)1.5% Ni
(iii)3.5%Ni
(iv)5%Ni
2XXX
20XX
21XX
23XX
25XX

100. AISI/SAE Designation System
Some Important AISI/SAE steel designation groups
S.
N.
Details of the steelAISI/SAE Group
3 Nickel-Chromium Steels3XXX
4 Molybdenum steels
(i)Cr-Mo
(ii)Cr-Ni-Mo
(iii)Ni-Mo
4XXX
41XX
43XX
46XX

101. AISI/SAE Designation System
Some Important AISI/SAE steel designation groups
S.
N.
Details of the steelAISI/SAE Group
5 Chromium steels 5XXX
6 Chromium-Vanadium
steels
6XXX
7 Tungsten steels 7XXX
8 Ni-Cr-Mo steels 8XXX
9 Silicon sttels 92XX

102. AISI/SAE Designation System
Steel Specification
AISI1035
Steel with 0.35%C
AISI4340
Mo steel with 0.4%C
AISI52100
Cr-steel with 1%C
and
AISI2440
Steel with 4%Ni and
0.4%C
AISI9260
Steel with 2%Si and
0.6%C

103. British Specification
British system of designation of steels is known as En series.
The En number of a steel has no corelation with the composition
or mechanical properties of steels
The new British system, BS970, used the first three digits for the
content of alloying elements, followed by a letter significance of
that is as shown below:
The last two digits after this letter is meant for carbon content
S.
N.
Letter Significance
1 A Analysis
2 H Hardenability
3 M Mechanical properties

104. British Specification
British
Old
En
British NewIndian StandardAISI/SAE
En6 080M41 C35Mn75 AISI1035
En24817M40 40Ni2Cr1Mo28AISI4340
En31534A99 109Cr1Mn60 AISI5210
0
En42070A72 C75 AISI1074

105. Questions
Q.1 State true or false and justify in brief.
a)Iron shows allotropic changes.
b)Carbon has more solubility in ferrite than in
austenite
c)Austenite is observed at room temperature in
plain carbon steel.
d)Hypoeutectoid steels shows cementite in their
structure at room temperature.

106. Questions
Q.1 State true or false and justify in brief.
e)Killed steels show better resistance to
grain coarsening than rimmed steels above
11000C.
f)Chemical analysis of steel can be obtained
from microscopic examination.

107. Eutectoid Steel
NO Proeutectoid phase!

108. The alternating αand Fe
3C
layers in pearlite causes
the redistribution of C by
diffusion as shown
during phase
transformation:
Hypoeutectoid
alloys:Alloys with
C content between
0.022 and 0.76
wt% are
hypoeutectoid
alloys.

109. Iron-Carbon System

110. Free Energy
Metastable
Stable
Unstable

111. The Iron-Carbon Diagram
Callister, Materials Science and Engineering An
Introduction, John Wiley & Sons

113. 113