1. D E P A R T M E N T O F M E T A L L U R G Y
O . P J I N D A L I N S T I T U T E O F T E C H N O L O G Y
D E P A R T M E N T O F M E T A L L U R G Y
O . P J I N D A L I N S T I T U T E O F T E C H N O L O G Y
D E P A R T M E N T O F M E T A L L U R G Y
O . P J I N D A L I N S T I T U T E O F T E C H N O L O G Y
MAJOR PROJECT REPORT
(2011-2012)
MMeecchhaanniiccaall aanndd MMiiccrroossttrruuccttuurraall
cchhaarraacctteerriizzaattiioonn ooff sstteeeell wwiitthh
rreeffeerreennccee ttoo tthhee eeffffeecctt ooff aallllooyyiinngg
eelleemmeenntt
DEPARTMENT OF METALLURGY
OP JINDAL INSTITUTE OD TECHNOLOGY
2. 2
DECLARATION
I hereby declare that this project report on, ―Mechanical & Microstructural
Characterization of Structural & HSLA steels with reference to the study of effect
of alloying elements, which is being submitted in partial fulfillment of the degree
of Bachelor of Engineering (Metallurgical Engineering) of Chhattisgarh Swami
Vivekananda Technical University, Bhilai,(CG), is the result of the work carried
out by us, at J.S.P.L, under the guidance of following members :-
1) Mr. R.K Saini ( Head QC R & D)
2) Dr. Manish Raj
3) Mr. Nimu Maure
4) Mr. D Reddy
5) Mr. Arun Behre
Also, project includes our internal guides without whom we are unable to
accomplish this project .They are-
1) Dr A.K Srivastava
(Head of the department, Metallurgy
O. P Jindal Institute of Technology)
2) Mr. Vikram Singh Nanda
(Former Assistant Professor, Department of Metallurgy,
O.P Jindal Institute of Technology)
5. 5
List of table
S.No List
1 Table 3(a) Compositional Analysis
2 Table 3(b) Tensile Test Data
3 Table 3(c) Charpy Impact Test Data
4 Table 3(d) Hardness Test Data
6. 6
List of figure
S.NO List
1 Fig-2(a) Universal Testing Machine
2 Fig-2(b) Vernier Caliper
3 Fig-2(c) Charpy Impact Specimen
4 Fig-2(d) Notched Impact Specimen
5 Fig-3(a) Microstructure of ST-02 at 400x & 1000x respectively
6 Fig-3(b) Microstructure of MA-02 at 400x & 1000x respectively
7 Fig-3(c) Microstructure of MA-03 at 400x & 1000x respectively
8 Fig-3 (d) Calculation of relative amount of phases
7. 7
ABSTRACT
This project report comprises the brief introduction to Structural
Steel including its t ype and their characteristic. Further the
project includes the m echanical and Micro structural
characterization. The mechanical testing carried out in the JSPL
while the Microstructural characterization has been ca rried out
in OPJIT. This was carried out to understand the be havior of
alloying element in imparting structural property to the steel.
8. 8
ACKNOWLEDGEMENT
We take immense pleasure in thanking J.S.P.L group especially the HR
Department for having permitted us to carry out this project work.
I further wish to express deep sense of gratitude to QC R&D where at first we
would like to thanks to Mr. R.K Saini (HEAD QC R&D) , Dr Manish Raj, Mr.
Nimu Maure, Mr. D Reddy & Mr. Arun Behre.Also, Kaushik Bose, ------- helped
us greatly for the project . Next to them ,we greet special thanks to Dr. A.K
Srivastava, Head of Department (Metallurgy) & Mr. Vikram Singh Nanda, Former
Asst. Professor for his precious guidance and useful suggestions, which helped us
in completing the project work.
Words are inadequate in offering our thanks to the Project Team Members for their
encouragement and cooperation in carrying out the project work.
Many new persons landed whole hearted support as a gesture of faith in this
venture. With this I would like to pay a sense of regard to college management, for
their immense support and constant encouragement in terms of internet and library
facilities.
Following are the members of the project team:-
1) Gaurav Sharma
2) Deepak Patel
3) Pragya Mishra
4) Pushkar Dewangan
5) Neelam Sharma
9. 9
About JSPL
“Success with social responsibility”
Jindal Steel and Power Limited (JSPL) is one of India’s major steel producers with
a significant presence in sectors like Mining, Power Generation and Infrastructure.
With an annual turnover of over US $2.9 billion, JSPL is a part of the about US $
15 billion diversified O. P. Jindal Group and is consistently tapping new
opportunities by increasing production capacity, diversifying investments, and
leveraging its core capabilities to venture into new businesses. The company has
committed investments exceeding US$ 30 bi llion in the future and has several
business initiatives running simultaneously across continents.
Mr. Naveen Jindal, the youngest son of the legendary late Shri. O. P. Jindal
spearheads JSPL and its group companies. The company produces economical and
efficient steel and power through backward integration from its captive coal and
iron-ore mines.
From the widest flat products to a whole range of long products, JSPL today sports
a product portfolio that caters to varied needs in the steel market. The company
also has the distinction of producing the world’s longest 121 metre rails and
introducing large size parallel flange beams in India.
Facilities at the plant include:
• DRI Plant - 4 nos. of 500 TPD
(0.72 million TPA) and 6 nos. of
300 TPD rotary kilns (0.6 million
TPA)
• 0.8 million TPA coke oven plant
• 2.5 million TPA sinter plant
• 1681 m3
and 446 m3
blast furnaces
• 2x100 ton EBT electric arc
• 1 No. of 6-strand billet-cum-round
caster
• 1 No. of 4-strand bloom-cum-
beam and blank-cum-round caster
• Rail & universal beam mill
(RUBM) (0.75 million TPA)
• Plate-cum-coil Mill (1.0 million
TPA)
10. 10
furnaces (EAF) (2.4 million TPA)
• Vacuum degassing unit
• RH degassing unit
• 1 No. single strand slab caster
• Submerged arc furnace (SAF)
(0.03 million TPA)
• Oxygen plant 26600NM3
/hr.
• Lime and dolomite calcinations
CHAPTER 1:-
1.1 INTRODUCTION
High strength low alloy steel (HSLA) or microalloyed s teel are designed to
provide better mechanical properties and greater resistance to atmospheric
corrosion than conventional carbon steel. they are not considered to be alloy steel
to be normal sense because they are designed to meet specific mechanical
properties rather than a chemical composition (HSLA steel have yield strength
greater than 275 MPa or 40 ksi ). The HSLA steel in sheet or plate from have low
carbon steel content (0.05-0.25%C0) in order to produce adequate formability and
weldability and they have Mg content to 2.0% .and small quantities of Cr,Ni, Mo,
Cu, nitrogen, vanadium, niobium, titanium, and zirconium are used to various
combinations.
HSLA steel categories. HSLA include many standard and proprietary grades
designed to provide specific desirable combinations of properties such as strength,
toughness, formability, weldability, and atmospheric corrosion resistance. These
steel are not considered alloy steel, even though their desired properties are
achieved by the use small alloy addition.
1.2 Types
HSLA steel can be divided into six categories:
• Weathering steels, which contain small amounts of alloying elements such
as copper and phosphorus for improved atmospheric corrosion resistance
and solid-solution strengthening (`see the article “carbon and ALLOY
steels”)
11. 11
• Microalloyed ferrite pearlite steels, which contain very small (generally less
than 0.10%) additions of strong carbide or carbonitride forming elements
such as niobium, vanadium and/or titanium for precipitation strengthening,
grain refinement, and possibly transformation temperature control.
• As-rolled pearlitic steels, which may include carbon manganese steels but
which may also have small additions of other alloying elements to enhance
strength, toughness, formability, and weldability
• Acicular ferrite (low-carbon bainite) steels, which are low carbon (less than
0.05% C) steels with an excellent combination of high yield strength, (as
high as 690 MPa, or 100 ksi) weldability , formability, and good toughness
• Dual phase steels, which have a microstructure of martensite dispersed in a
ferritic matrix and provide a good combination of ductility and high tensile
strength
• Inclusion shape controlled steels, which provide improved ductility and
through thickness toughness by small additions of calcium, zirconium, or
titanium or perhaps rare earth elements so that the shape of the sulfide
inclusions is changed from elongated stringers to small dispersed almost
spherical globules
These categories are not necessarily distinct groupings as an HSLA steel may have
characteristics from more than one grouping for example; all the above types of
steels can be inclusion shape controlled microalloyed ferrite pearlite steel may also
have additional alloys for corrosion resistance and solid solution strengthening.
The various type of micro alloyed ferrite - pearlier steel include:
• Vanadium microalloyed steels
• Niobium microalloyed steels
• Niobium - molybdenum steel
• Vanadium - Niobium microalloyed steel
• Vanadium - Nitrogen microalloyed steels
• Titanium - microalloyed steel
• Vanadium - titanium microalloyed steel
Vanadium microalloyed steels
12. 12
The development of vanadium containing steel occurred shortly after the
development of the weathering steel, and flat - rolled product with
upto 0.10% v are widely used in the hot rolled condition. Vanadium containing
steels are also used in the controlled - rolled normalized, or quenched at the
controlled condition.
Vanadium contributes to strengthening by forming small precipipate partical (5nm
to 100nm in dia.) of vanadium carbide V (CN) in ferrite during after hot rolling.
Niobium microalloyed steels
Like Vanadium Niobium also increases yield strength by precipitation hardening,
Niobium is also a more grain refiner than Vanadium. The usual niobium addition is
0.02 to 0.045, which about one third the optimum vanadium addition.
Strengthening by niobium is 35 to 40 Mpa per 0.015 additions.
Vanadium - Niobium microalloyed steels.
Steels microalloyed with both Vanadium and Niobium provide a higher yield
strength in the conventionally hot rolled c ondition than that of achievable with
either element alone .the addition of both Ni9obium and vanadium together is
especially advantage for incrasing yield strength and lowering ductile - brittle
transition temperature by grain refinement. Usually niobium - Vanadium steels are
made with relatively low carbon content(<10%C).This steels frequently referred to
as pearlier - reduced steels.
Niobium - Molybdenum microalloyed steels
This steels may have either ferrite pearlier microstructure or an acicular ferrite
microstructure . In ferrite pearlier steels the addition of MO increases the yield
strength and tensile strength by about 20 Mpa and 30 Mpa respectively. Per 0.15
MO, over investigated range of 0% to 0.27% MO. The principle effect of MO on
the morphology of the pearlier and to introduce upper bainite as replacement of
ferrite. The strengthening is due to the solid- solution strengthening and enhanced
Nb (CN) precipitation strengthening caused by a MO – Nb synergism.
Vanadium - Nitrogen microalloyed steels
13. 13
Vanadium combines with nitrogen more strongly than Niobium and forms VN
precipitates in Vanadium - nitrogen steel .precipitation hardening accomplished by
a drop in notch toughness, but this can often be overcome by lowering the carbon
content. The precipitation of Vanadium nitrides also act as a grain refiner.
Hot rolled plate with Vanadium and 0.018 to 0.0225 N have been produced by
controlled cooling in thickness upto 16 mm.
Titanium microalloyed steels
Titanium in low carbon steel forms into the no. of compounds that provide grain
refinement, precipitation strengthening, and sulfide shape control. However,
because titanium is also a strong deoxidizer titanium can used only in fully killed
steel so that titanium is available for forming into compounds other than titanium
oxide. Experimentally observed strength increases from TiC precipitation have a
range upto 440 Mpa for very fine particles.
Small amount of titanium (<0.0255% Ti) are effective grain refiner because
austenitic grain growth is retarded by titanium nitride.
Titanium – Niobium microalloyed steels
Titanium increases the efficiency of Niobium because it combines with Nitrogen
forming titanium nitrides, thus preventing the formation of Niobium nitrides. This
allows for increased precipitation of Nb(C,N) particles in ferrite. Hot rolled
Niobium titanium (0.04%) steel strip is effective achieving in yield strengths of
550 Mpa in ferrite - pearlier steels.
14. 14
CHAPTER 2:- Mechanical testing procedure
2.1 Tensile Test:-
IS 1608: 2006
ISO 6892:1998
The international standard is the specify the method for tensile testing of metallic
material and define the mechanical property at room temperature
Normally reference
The following standard contains provision which, through references in this text,
constitute provision of this international standard. At the time of publication, the
editions indicated were valid. All standard are subjected to revision, and practice to
agreement based on this international standard are encountered to investigate the
possibility of applying the most recent edition of the standards indicate below.
Member of IEC and ISO maintain register of currently valid international
standards.
ISO286.2:1988, ISO system of limit and fit - part 2: tables of standard tolerance
grade and limit deviation for holes and shafts.
ISO 377: 1997, steel and steel production – location and preparation of samples
and test pieces for mechanical testing.
ISO 2566.1:1984, steel –conversion elongation value: carbon and low alloy steel .
15. 15
ISO 5266.2: 1984,steel –b conversion and elongation value- part 2: austenitic
steels.
ISO 7500.1:1986, metallic material – verification of static uniaxial testing
machines –part 1: tensile testing machines.
ISO 9513: metallic material – verification of extensometer used in uniaxial testing
2.1.1 Aim:
To conduct a tension test on given m icro alloyed and structural steel specimen
using Universal testing machine at ambient temperature by IS 1608:2005/ISO
6892:1998.
2.1.2 Principle:-
the test involves straining a test piece by tensile force, generally to fracture, for the
purpose of determining one or more of mechanical property. the test is carried out
at ambient temperature between 100
c &350
c, unless otherwise specified tests
carried out under controlled condition shall be made at a temperature of 230 +_
5o
.
2.1.3 Apparatus & Equipment Used:-
Fig-2(a) Universal Testing Machine
16. 16
1. UTM
2. Specimen with desired dimension
3. Vernier Caliper
4. Punches
5. Marker
2.1.4 Procedure:
1. Measure the diameter of the rod using Vernier calliper.
2. Measure the original length of the rod.
3. Mark the centre of the specimen using dot punch.
4. Mark two points P and Q at a distance of 110mm on either side of the centre
mark so that the distance between P and Q will be equal to 220mm.
5. Mark two point A and B at a distance of 2.5 times the rod distance on the
either side of the centre mark so that the distance between A & B will be
equal to 5 times the rod diameter and is known as initial gauge length of rod.
6. Insert the specimen in the middle cross head and top cross head grip of the
machince so that the two points A and B coincide with grips.
7. Apply the load gradually and continue the applications of load. After
sometime, there will be slightly pause in the increase of load. The load at
this point is noted as yield point (Py).
Fig-2(b) Vernier Caliper
17. 17
8. Apply load continuously till the specimen fails and note down the ultimate
load (Pa) and breaking load (Pb) from the digital indicator.
9. Remove the specimen from the machine and join the two pieces of the
specimens.
10.Measure the distance between the two points A and B. This distance is
known as final gauge length (li) of the specimen.
11.Measure the diameter of the rod at neck (dn).
12.Atlast calculate the following:
• Yield stress
• Ultimate stress
• Nominal breaking stress
• Actual breaking stress
• Percentage Elongation in length
2.2.CHARPY IMPACT TEST
2.2.1 Aim:-
To determine the impact strength of the of the metallic material by the charpy
impact (v-notch) method IS: 1757-1988
2.2.2Principle:-
The test consist of breaking by one blow from a swinging pendulum, under the
condition defined, here after, a test piece v-notched in middle and resulting on two
support. The energy
absorbed is determined.
18. 18
2.2.3Apparatus and equipment used:
• Impact testing machine with attachment for charpy test.
• Charpy specimen
• Vernier caliper
• Scale.
2.2.4Theory:-
1. The standard test piece shall be 55 mm long &of square selection with
10mm each side. In the centre of the length there shall be a v-notch on 45o
included angle, 2mm deep with 0.25mm roof radius.
If the standard test piece cannot be obtain from the material, one of the
subsidiary test pieces having a width of 7.5 or 5mm shall be used, the notch
being cut in on of the narrower faces. The test piece shall be machined all
over.
Fig-2(c) Charpy Impact Specimen
19. 19
2. The plane of the symmetry of the notch shall be parallel to the longitudinal
axis of the test piece
3. Preparation shall be carried out in such a way that any alteration of the test
piece, for eg:-, due to heating or cold working is minimized. the notch shall
be carefully prepared so that no groove appear at the base of the notch.
4. The test piece may be marked on any face not in contact with support or
anvils and at a position well away from the notch in order to avoid the effect
of work hardening induced by stamping.
The condition for a standard test shall be where the nominal striking energy
of the testing matching is 300 +
- 10j. in kv its value is reported.
2.2.5 Procedure:
1. The test piece shall lie squarely agents the lath support, with the plane of
symmetry of the notch within 0.5mm of the plane midway between them. Ti
shall be struck by the stricker in the plane of symmetry of the notch & on the
side opposite the notch.
2. The temperature of testing is not satisfied in the product standard, it shall be
23150
c.
3. For test of temperature other than the ambient the test piece shall be
immersed in the heating/cooling medium for sufficient time to ensure heat is
the required temperature is reached throughout the test piece. Ti shall be
broken with in 5 sec from the time of removal from the edium.
4. The transfer device shall be designed and used so as to ensure that the
temperature of test piece remains within the temperature range permitted.
2.3. HARDNESS TEST
Fig-2(d) Notched Impact Specimen
20. 20
2.3.1Aim:
To determine the mechanical property at ambient hardness.
2.3.2Apparatus and Equipments Required:
1. Rockwell Hardness Testing Machine.
2. Metal Specimen.
2.3.3 Theory:
Hardness may be defined as resistance of metal to plastic deformation
usually by indentation. However the term may also refer to stiffness or temper or
resistance to scratch, abrasion or cutting.
Rockwell testing is suitable for materials having hardness beyond the scope
of Brinell testing. Rockwell testing is faster as compared to Brinell testing ,
because the diameter of the indentation need not be measured. The Rockwell
machine gives arbitrary direct reading, Unlike Brinell testing, Rockwell testing
needs no surface preparation (Polishing) of the specimen whose hardness is to be
measured.
There are two scales on Rockwell testing specimen. i.e B scale and C scale. B
scale uses a steel ball indenter where as a diamond cone penetrate is employed for
measuring Hardness on C scale.B scale. In Rockwell hardness testing, the minor
load for all cases is 10 Kg.
Test requirements:
1. The test should be carried out in an ambient temperature of 20 +20
C in
temperate climate and 27 +20
C in tropical climates.
2. The testing machine shall be protected through out the test from shock and
vibrations.
3. The test piece shall be placed on a rigid support. The contact surfaces shall
be clean and free from foreign matter. ( such as oil and dust)
4. The thickness of the test piece shall be at least 8 times the permanent
indentation of depth. No deformation shall be visible at the back of the test
piece after the test.
5. The distance between the centres of the two adjacent indentations shall be at
least 4 times the diameters of the indentation and the distance from the
centre of any indentation to the edge of the test piece shall be at least 2.5
times the diameter of the indentation unless agreed otherwise.
21. 21
2.3.4 Procedure:
1. Test piece is placed upon the machine. The dial may be showing any
reading.
2. Hand wheel is turned , thereby raising the test piece up against the steel ball
indenter till the needle of the small dial is against the red mark. This applies
minor load.
3. Major load is applied by pressing the crank provided on the right hand side
of the machine. Time is given as 30 sec so as to make the load reach
specimen fully.
4. When the penetration is completed, the crank is turned in the reverse
direction thereby with drawing the minor load but the leaving the major load
applied.
5. The pointer moves further and becomes stand still. This reading is taken as
Rockwell Hardness Number – C scale.( HRC)
6. Hand wheel is rotated and the test piece is lowered.
CHAPTER 3:- EXPERIMENTAL PROCEDURE
3.1 Aim Of Experiment:-
To carry out the mechanical & microstructural Characterization of Micro Alloyed
steel designated as MA-02 (3108429-CFO) , MA-03 (2102906-BFO-H) and
structural steel designated as ST–02(3107162-BAO-H) so as to evaluate the effect
of various alloying elements on its properties.
3.2 Sample Description:-
The Hot Metal obtained from the Blast Furnace was primary refined in Electric
Arc Furnace (SMS – II , J.S.P.L) followed by secondary refining in Ladle Refining
Furnace. For Ultra High Refining and based on Customer demand we can also use
either R-H Degasser or Vacuum Degasser.
22. 22
The sample was then cast in form of slab using Single Strand Slab Caster. After
this the slab was then reduced in thickness using Two –high rolling arrangement
and Four – high Rolling arrangement.
The sample was then cut from the lot to a dimension of 400mmX 400mmX45mm.
From this various sample were prepared for the purpose of meeting the objective of
experiment.
For the Microstructural sample preparation initially belt grinding was carried out
(O.P.J.I.T) This was then followed by coarse and fine grinding using emery paper.
After polishing the sample was then etched using Nital solution (98%ethanol and
2% nitric acid) .
3.3 Equipments Used:-
• Band Saw
• Shaper
• Pedestal grinder
• Surface Grinder
• V- notch Cutter
• Universal Testing Machine
• Charpy Impact testing
• Electron emission spectrometer
• Vicker hardness tester
• Belt Grinder
• Upright Metallurgical Microscope.
23. 23
3.4 Results:-
3.4.1 Compositional Analysis:- It was carried out using electron emission
spectroscopy in which the specimen was subjected to an electron beam. The
interaction of the electron beam and specimen surface generates rays which yield
the compositional data of specimen.
24. 24
The composition of the three specimens is given in table 4.1.
Table 3(a) Compositional Analysis
25. 25
3.4.2 Tensile Test:- The sample was prepared with a dimension in accordance to
the Standard IS Specification. It was then tested using Universal Testing
Machine.
The various mechanical parameters associated with the test are tabulated which are
given in table 3 (b)
3.4.3 Impact Test:- In this test three sample was of each grade was prepared with
a dimension a nd groove angle as per specified in Standard EN
specification. The test was carried out at room temperature and also at sub-
zero temperature of -20 ºC using liquid nitrogen atmosphere.
Table 3(b) Tensile Test Data
26. 26
The test results are given in table 3(c)
3.4.4 Hardness Test:- Hardness test was carried out using Vicker Hardness tester
with a load of 10 Kg.
The hardness value are tabulated in table 4.4
S.No Sample - ID Hardness Values Average
valuesI II III
1. MA-02 188 160 160 160
2. MA-03 191 182 182 182
3. ST-02 156 138 149 148
Table 3(c) Charpy Impact Test Data
Table 3(d) Hardness Test Data
27. 27
3.4.5 Optical metallography:- In the metallographic study; the sample
preparation was carried out at Characterization lab of Deptt. Of
Metallurgy, O.P.Jindal Institute of Technology . Nital was used as etchant
and the specimen were examined at 500X and 1000X. The microstructure
of the samples are given at
MA-02
Fig-3 (a) Microstructure of ST-02 at 400x & 1000x respectively
Fig-3(b) Microstructure of MA-02 at 400x & 1000x respectively
30. 30
CONCLUSION
Alloying elements are added to alter the properties of base metal. This project
report covers some of the alloying elements that are added to the basic system of
iron and carbon, and what they do to change the properties or effectiveness of
steel.
With the combination of various alloying element; a wide range of properties as
well as applications are achieved. However, it is important to remember that each
of the alloying elements are unique and therefore are used depending upon
suitability of the process route and final product.
Further the main reason that led to alloying was the failure or limitation of plain
carbon steel to perform its intended function for structural applications. Also plain
carbon steels offered very narrow range of properties and its application areas are
also very less. In order to overcome the shortcoming of plain carbon steel, alloying
proved to be the most beneficial method to enhance steel properties for structural
applications.
High strength low alloy (HSLA) steels offer the advantage of weight and cost
savings compared to mild steel. Therefore they are widely used in the automotive
and the construction industry.
With the additions of micro alloys and other alloying elements, HSLA strip steels
up to a minimum yield strength of 690MPa (Grade 100) is widely applied. The
application of microalloyed high strength low alloy steels is now well established
in today’s market place for both the automotive and structural applications. Of the
two, it is undoubtedly the automotive sector, which has seen the greatest high
profile developments.
31. 31
REFERENCE
4 Bain, E.C., Alloying Elements in Steels, ASM, Cleveland, Ohio, USA (1939).
5 Sinha, A.K., Ferrous Physical Metallurgy, Butterworth Publishers, USA (1989).
6 Bhadeshia, H.K.D.H, Honeycombe, R.W.K, Steels: Microstructure and Properties,
n Elsevier
7 ASM Handbook, Vol. 4, Heat Treating, ASM International (1991).
8 Totten, G.E., Howes, M.A.H, Steel Heat Treatment Handbook, Marcel Dekker,
Inc., USA (1997).
9 Bhadeshia, H.K.D.H, Design of Ferritic Creep-resistant Steel, ISIJ International,
Vol. 41 (2001), No. 6, 626-640.
10 Porter, D.A., Easterling, K.E., Phase Transformations in Metals and Alloys, CRC
Press, Taylor & Francis Group, Finland (2004).
11 Thelning, K.E., Steels and its Heat Treatment, Butterworth & Co. and K-E
Thelning, UK (1984).
12 Leslie, W.C., The physical Metallurgy of Steels, McGraw-Hill, Tokyo, Japan,
(1981).
13 Gladman, T., The Physical Metallurgy of Micro alloyed Steels, The Institute of
Materials, UK (1997).
14 http://www.steeltalk.com/high_strengthsteels.php.
