This study analyzes the effect of composition and microstructure on the properties of Indian rail steel. It summarizes the specifications and grades of Indian rail steel as well as the typical microstructures found, including pearlite and bainite. Head hardening is discussed as a process to refine pearlite, while bainitic rail steel is proposed as an alternative that offers higher hardness, strength and toughness than pearlitic rail steel. Track testing methods are presented for comparing wear performance of different rail compositions and microstructures. Thermite welding is also summarized as the primary joining technique used in rail production.
Indian Rail Steel- Pearlitic and Bainitic Rails and comparision
1. Study on the Effect of
Structure & Composition
on Properties of
Indian Rail Steel
Presented By
MUKULDEV KHUNTE
KESHAV SAHU
Dept. of Metallurgical & Materials
Engineering.
OPJU, Raigarh
At
International Conference
On
RECENT ADVANCES IN METALLURGY FOR
SUSTAINABLE DEVELOPMENT
2. Contents
• Introduction
• Indian Rail Steel
• specification
• Analysis of Composition on Microstructure &
Property
• Head Hardening
• Pearlite Vs Bainitic
• Conclusion
• References
3. Introduction- Rail Transport System In India
Rail transport system is the main public transport system in
India and is administered by the “Federal Government of
India” namely, Indian Railways.
Rail transport system is connected with all the major cities of
the country.
Rail transport system is aiding movement of the people with
lowest fare and the source of transportation from big cities like
Delhi, Chennai, Mumbai, Kolkata, Bangalore and Hyderabad[1].
4. Introduction- Rail Transport System In India
As of August 2015, Indian Railways had 12,617 passenger
trains carrying over 30 million passengers daily.
Indian Railways is hence labelled as “Provide what is
better” “Promote what is best” Preserve what is good”
which is true.
The total length of the rail tracks is about 64,600 route
kilometres covering 7146 railway stations in India.
Indian Rail transport system is also connected with two
neighbouring countries like Pakistan and Nepal[1].
5. Rail Network System in World :-
India is World’s 3rd largest rail network as report
of IEBF (Indian brand Equity Foundation) on 2015
• United States
• Russia
• China
• India
• Canada
• Germany
• Australia
• Argentina 0
50,000
100,000
150,000
200,000
250,000
United
States
Russia China India Canada Germany Australia Argentina
6. Indian Rail Steel
Rail steel is used to make rails for railway lines and for other
uses such as tracks for moving equipment's like cranes, transfer
cars etc.[1]
The importance of the rail steel can be known from the fact that
even after years of service and high stress, there is no difference
between the grain structure of a used rail and a new rail. Age,
traffic and weather do not change its basic properties. [2]
7. Grade’s of Rail Steel
Grade 880 880
Grade 1080 HH 1080 HH
Grade 1080 Cr 1080 CR
Grade 880 Cu-MO 880 CM
Grade 880 Ni Cr Cu 880 NC
Grade 880 Vanadium 880 VN
Grade 880 Niobium 880 NB
*Note- Given data is based on INDIAN RAILWAY STANDARD SPECIFICATION (IRS T-12-2009 )
8. Indian Rail Steel – Dimensions[3]
The UIC (French: Union Internationale des Chemins de fer) or International Union of
Railways is an international rail transport industry body
9. Specification[3]
Specification Grade Hardness UTS
(Mpa)
IRS T-12 2009 Normal Grade Rail ≥260 BHN 880
IRS T-12 2009
Head Hardened
Rail
340-390 BHN 1080
EN 13674-2011 Normal Grade Rail 260-300 HBW 880
EN 13674-2011 Head Hardened
Rail
350-390 HBW 1075
BHN- Brinell Hardness Number
HBW- H from hardness, B from Brinell and W from the material of the indenter, tungsten
(wolfram) carbide
10. Rail Composition And Mech. Properties[3]
Grade 880 1080HH
C 0.6-0.8 0.6-0.8
Mn 0.8-1.5 0.8-1.50
Si 0.10-0.50 0.10-0.50
S(max) 0.03 0.03
P(Max) 0.015 0.015
Al (Max) 0.015 0.015
Hydrogen Content
in Liquid Steel
1.6 PPM 1.6PPM
UTS(Mpa min) 880 1080
Yield Strength(Mpa
Min)
460 460
Running Surface
Hardness
Min 260 340-390
*Chemical Composition and Mech. Properties as per IRST12-2009
13. Role Of Microstructure
In steels and cast irons, the microstructural constituents have
the names ferrite, pearlite , bainite, martensite, cementite, and
austenite.
In most all other metallic systems, the constituents are not
named, but are simply referred to by a Greek letter (α,β,ϒ etc.)
derived from the location of the constituent on a phase
diagram.[4]
15. Role Of Microstructure
Ferrite Microstructure
A wide variety of steels and cast
irons fully exploit the properties of
ferrite. However, only a few
commercial steels are completely
ferritic.[4]
Ferrite is essentially a solid solution
of iron containing carbon or one or
more alloying elements such as
silicon, chromium, manganese , and
nickel. Have BCC crystal
structure.[4]
Microstructure of a fully ferritic, ultralow carbon
steel. Marshalls etch + HF, 300x. Courtesy of
A.O. Benscoter , Lehigh University
16. Role Of Microstructure
Ferrite-Pearlite Microstructure
The most common structural steels
produced have a mixed ferrite-
pearlite microstructure. Their
applications include beams for
bridges and
high-rise buildings, plates for ships,
and reinforcing bars for roadways.[4]
In most ferrite-pearlite steels, the
carbon content and the grain size
determine the microstructure and
resulting properties.[4]
Microstructure of typical ferrite-pearlite structural steels
0.10% C.(2% nital + 4% picral etch. 200x)
17. Role Of Microstructure
Martensite Microstructure
Martensite is essentially a
supersaturated solid solution of
carbon in iron. The amount of
carbon in martensite far exceeds
that found in solid solution in
ferrite. Because of this, the normal
body-centered cubic (bcc) lattice is
distorted in order to accommodate
the carbon atoms. The distorted
lattice becomes body-centered
tetragonal (bct).[4] Microcracks formed in plate martensite. 4% picral +
HCl/sodium metabisulfite etch. 1000x
18. Role Of Microstructure
Bainite Microstructure
Upper bainite consists of needles of
ferrites separated by long
cementite particles
It occurs in the T ~300 -5400C
Lower bainite consists of thin plates
of ferrite containing very fine rods
or blades of cementites [5]
It occurs in T~200-3000C
(a)
(b)
Microstructure of (a) upper bainite and
(b) lower bainite in a Cr-Mo-V rotor steel.
2% nital + 4% picral etch. 500x
19. Grain size Mech. Property Correlation
The Hall-Pitch equation
Polycrystalline metals almost always show a strong effect of
grain size on hardness and strength, except possibly at very
elevated temperatures. The smaller the grain size the greater the
hardness or flow-stress.[6]
σ= σ0+kd(-1/2)
where σ is the flow-stress ,σ0 is a lattice frictional stress , k is a
constant, d is the diameter of the grains [7]
21. Head Hardening Process
Rails currently used in rail transport are mainly manufactured
of pearlitic steel. According to the standard EN13674-1,.[8]
The pearlitic structure is formed below the A1 temperature,
being approximately 7270C, during cooling from the austenite
stability range of temperatures . The most important parameter
characterizing pearlite microstructure is spacing between
cementite lamellae.[9]
Determining the actual distance between the cementite lamellae in pearlite, S0= L/2, using mean intercept method
22. New Head Hardening Process
Different methods of head hardening process aiming at
increasing rails durability in service were characterized .One of
these methods, developed by Voest Alpine, consists in
accelerated cooling of rail’s head directly after the rolling
process (in-line method) in aqueous solution of polymer
substances .
In this method, rail head is immersed in the cooling solution for
a specified period of time (around 200 s), during which it
undergoes intense cooling. The time of intense cooling is
determined in such a way so as to obtain a fine pearlite
structure,[8]
23. Stages of New Head Hardening Process
Fig -Stages of the new rail’s
head hardening process.[8]
Hardness distribution as a function of distance from
the rail running surface after cyclic cooling. .[8]
24. Bainitic Rail Steel Production Method
Full section Bainitic steel rails can be produced by conventional
methods using natural cooling after rolling. With suitable
chemistries , complex heat treatment are not necessary[10]
Bainitic Rail Steels can be produced well above 400 HB with the
Fracture toughness significantly above that commonly seen in
HH pearlitic steel rails.
This increased toughness increases the critical crack size before
sudden fracture. [10]
25. Pearlitic Rail Vs Bainitic Rail
Basis Of Distinction Bainitic Rail HH Pearlite Rail
1. Structure A fine non-lamellar
structure, commonly
consists of cementite
and dislocation-rich
ferrite.[7]
A two-phased, lamellar
structure composed of
alternating layers of
alpha-ferrite and
cementite. [7]
27. Pearlitic Rail Vs Bainitic Rail
Basis Of Distinction Bainitic Rail HH Pearlitic Rail
3. Ultimate Tensile
Strength
Bainitic structure
steels that could
achieve strength up to
1400 MPa [11]
Head Hardened
Pearlitic Rail structure
steels that could
achieve strength up to
1080 MPa [3]
28. Pearlitic Rail Vs Bainitic Rail
Basis Of Distinction Bainitic Rail HH Pearlitic Rail
4. Wear resistance Lower Wear
Resistance[13]
Higher Wear
Resistance. Wear rates
were reduced as
hardness increased by
reducing the
interlamellar spacing
[13]
29. Pearlitic Rail Vs Bainitic Rail
Basis Of Distinction Bainitic Rail HH Pearlitic Rail
5. Toughness High Toughness due to
non-lamellar
Structure[13]
Low Toughness due to
lamellar Structure. [13]
30. Joint Efforts By Tata Steel & Corus
Tata Steel In collaboration with Corus has come up with
innovative rail steel and proposed bainitic rail steel. Corus B320
has been installed in Eurotunnel – Good Performance in track
tests.[5]
31. Track Testing Methods
The rail testing procedure were applied in order to provide and
objective comparison of the rail damage behaviour.[14]
The Testing Methods are
1. Magnetic Particle Inspection
2. Eddy Current Test
3. Material Loss By Wear Using Profile Measurement Method
done by MiniProf Rail Instrument
(The MiniProf Rail instrument is an easy-to-use, lightweight and handheld tool for monitoring cross sectional profiles of the rail. It is
attached magnetically to the top of the railhead, using the opposite rail as reference through a telescopic rod.)[14]
32. Thermite Welding
The Thermite welding process is essentially a casting process,
where the molten metal obtained by the thermite reaction is
poured into the refractory cavity made around the joint.
The two pieces to be joined are properly cleaned and the edge is
prepared then wax is poured into the joint so that a pattern is
formed where the weld is to be obtained .
A mounting flask is kept around the joint and sand is rammed
carefully around the wax pattern .Providing the necessary pouring
basin, spure and risers.
A bottom opening is provided to run off the molten wax. The Wax
is melted through this opening which also used to preheat. The
joint and make it ready for welding.[15]
34. Conclusion:-
• The 100% fine pearlite Structure contains fine inter laminar
spacing and high hardness on the surface of rail by head
hardening heat treatment.
• It is applied by accelerated cooling with the force air, water
spray at a pressure 2-3 bar and pH 7.8
• Alloying approaches to refine the pearlite laminar have
included alloying with Cr, Mo, Vd & Si with hyper Eutectoid
carbon contained
• However bainitic structure can be obtained by proper designing
of heat treatment particularly on the head portion of the rail.
35. Continue:-
• Bainitic structure are more tougher harder and equivalent wear
resistance those of fine pearlite
• This structure is sustainable in curved portion of the track
where it is severally stressed under heavy traffic condition,.
• Compressive residual stress developed at the surface of the rail
and are balanced by interior tensile stress due to bainite
structure.
• Bainitic steel can be welded through thermite welding with
proper alloying elements of the thermite mixture which will
give a sound welding characteristic as compare to fine pearlite.
36. References
1. V.Rajeswari, K.Santa kumari “Satisfaction and Service Quality in Indian Railways - A Study on Passenger
Perspective” e-ISSN: 2321-5933
2. Rails and Rail steel ( www.ispatguru.com )
3. JSPL Rail Steel Inspection Brochure
4. Bruce L. Bramfitt , Homer Research Laboratories, Bethlehem Steel Corporation “Structure/Property
Relationships in Irons and Steels”
5. Dr. Shashank Shekhar “Phases and Microstructure” Knowledge Incubation for TEQIP IIT Kanpur
6. Peter Haasen “Physical Metallurgy” 3rd edition ISBN 0-521-55092-0
7. R. Ε. SMALLMAN “MODERN PHYSICAL METALLURGY” 3rd edition ISBN 0 408 70782 8
8. Roman Kuziak and Tomasz Zygmunt “A New Method of Rail Head Hardening of Standard-Gauge Rails for
Improved Wear and Damage Resistance”
9. T. Judge, “Handling HAL. Railway Track & Structure”
10. K. Sawley & J. Kristan “Devolopment Of Bainitic Rail steels with Potential resistance to Rolling contact
fatigue”
11. Ivo Hlavatý, Marián Sigmund, Lucie Krejčí, Petr Mohyla “THE BAINITIC STEELS FOR RAILS APPLICATIONS ”
12. Alberto J. Perez-Unzueta and John H. Beynon “Microstructure and wear resistance of pearlitic rail steels”
13. Ki Myung Lee, Andreas A. Polycarpou “Wear of conventional pearlitic and improved bainitic rail steels”
14. Gregor Girsch ,Rene Heyder “Advance Parlitic and Bainitic high strength rails promise to improve rolling
contact fatigue resistance”
15. Manufacturing technology volume-1 foundary,forming and welding Tata MCGraw-Hill publication third
edition by P N Rao.
