Alloy design for Structural and rail applications

Alloy Design
for
Structural and Rail Applications
By
Dr. M. Kalyan Phani
Associate Professor
Metallurgical Engineering
July 29, 2019 Faculty Development Program 1
M
KP_C
R

Contents
 Introduction
 Alloy design Goals
 Methodology for alloy design
 Prerequisites for alloy design
 Steels Classification
 Steels for Construction
 Structural grades
 Future developments in Structural steels…Light steel??
 Steels for Rails
 Future developments in steels for rail roads.
 Glimpse of JSPL Rail steel project undertaken by OPJU
Faculty Development ProgramJuly 29, 2019
2
M
KP_C
R

Introduction
• The practice of alloy design has existed for thousands of years.
• The theoretical basis took longer to arise but dates back to at
least the work of Hume-Rothery, with much development in the
intervening period.
• The process of alloy design as applied currently covers many
approaches, encompassing iterative “tinkering” with
compositions, computational approaches using electronic
structure or thermodynamic parameters, and many individual
or in-house strategies.
• Though very different methods, all are united by having a set
goal or goals for the alloys created, and using an iterative,
defined method, requiring knowledge of the behavior sought, to
reach it.
Faculty Development ProgramJuly 29, 2019 3
M
KP_C
R

The Evolution of Materials
M
KP_C
R

Alloy Design Goals
“To create products that perform their function
economically, safely, at acceptable cost”.
Faculty Development Program
Prepare
the Alloy
July 29, 2019 5
M
KP_C
R

 It is the responsibility of the end users to select
the right materials for the right purpose.
 Every material as well as manufacturer offers
advantages of their materials with regards to
mechanical & physical properties, corrosion
resistance, and even offering a very good
technological performance.
 Failure to select proper materials will shorten
their lifetime and in turn will reduce the
company profits due to lost of equipment and or
valuable production time.
In designing a structure or device, how is the engineer to choose from
this vast menu the material which best suits the purpose?
Mistakes can cause disasters.
M
KP_C
R

M
KP_C
R

Opting a Methodology for Alloy Design
• Through First principles (Tinkering with alloying
elements) – Require thorough knowledge on
literature
• Through Software (Thermocalc/Calphad…..)
• Through both
M
KP_C
R

Converting Fe Ore to usable Steels
CS<36 in2 (230 cm2)
CS > 100 sq cm2, width
2*thickness
CS>Billet CS
July 29, 2019 9
M
KP_C
R

General Classification of Metal Alloys
M
KP_C
R

Alloying uses
M
KP_C
R

Rules for alloying
• The Hume-Rothery rules are a set of basic rules describing the
conditions under which an element could dissolve in a metal,
forming a solid solution. There are two sets of rules, one which
refers to substitutional solid solutions, and another which refers
to interstitial solid solutions.
Substitutional
Solid Solution
Interstitial
Solid Solution
July 29, 2019 12
M
KP_C
R

Rules for formation of Substitutional solid solution
1. The atomic radii of the solute and solvent atoms must differ by
no more than 15%.
2. The crystal structures of solute and solvent must match.
3. Maximum solubility occurs when the solvent and solute have the
same valency. Metals with lower valency will tend to dissolve
metals with higher valency.
4. The solute and solvent should have similar electronegativity. If
the electronegativity difference is too great, the metals will tend to
form intermetallic compounds instead of solid solutions.
M
KP_C
R

Interstitial Solid Solution rules
1. Solute atoms must be smaller than the pores in the solvent
lattice.
2. The solute and solvent should have similar electronegativity.
In contrast to intermetallic compounds, solid solution in general
are
• Easier to separate,
• Melt over a range in temperature,
• have properties that are influenced by those of solvent and
solute,
• Usually show a wide range of composition so that they are
not expressed by a chemical formula
M
KP_C
R

Relevance of Phase Diagrams
M
KP_C
R

What we get from Phase Diagram?
 Identify the phases existence against the temperatures
 Shows the relationships between composition, temperature and
structure of an alloy in series.
 Study the phase separation, solidification of metal and alloys,
purification of
 material, structural changes due to heat treatment, casting etc.
 Marks the liquidus and solidus lines
M
KP_C
R

M
KP_C
R

Structure sensitive
• yield strength,
• hardness,
• tensile strength,
• ductility,
• fracture toughness,
• fatigue strength,
• creep strength,
• corrosion resistance,
• wear resistance,
• thermal conductivity,
• electrical conductivity
Property of materials
Structure insensitive
•elastic moduli,
•Poisson’s ratio,
•density,
•thermal expansion
coefﬁcient,
•speciﬁc heat
M
KP_C
R

Alloying elements and their effect on properties
July 29, 2019 19
M
KP_C
R

M
KP_C
R

Introduction to Heat Treatment
“It is a process of heating and cooling of the metal/alloy to especially alter the properties
(Physical or Chemical) to achieve the desired product to a particular application”.
½ hour
Annealing Heat Treatment
900˚C
Temperature(in˚C)
Time (in hrs)
Temperature(in˚C)
½ hour
Time (in hrs)
Normalising Heat Treatment
900˚C
Heat treatment cycles used to tailor the microstructure as desired and thus the
properties.
HT cycle: Heat  Soak  Cool
July 29, 2019 21
M
KP_C
R

Objectives of Heat treatment
Increase hardness, wear and cutting ability of the alloy
Soften the alloy for further processing
Adjust mechanical, physical or chemical properties of the alloy
Refine grain size of alloy
Increase machinability of alloy
Produce hard case
Reduce embrittlement in alloys
Induce or eliminate residual stress
Change the composition of surface to impart good wear,
corrosion and fatigue properties
22July 29, 2019 Faculty Development Program
M
KP_C
R

Time Temperature Transformation Curves with
Continuous cooling transformation curves
23July 29, 2019 Faculty Development Program
M
KP_C
R

Hierarchy of structure
Macrostructure:
– Objects can be observed by the un-aided eye.
• Mesostructure:
– Objects are on the borderline of visibility.
• Microstructure:
– Objects can be viewed by means of optical microscopy techniques. Objects are
micron sized (~0.001 mm).
• Nanostructure:
– Objects have sizes between 1 nm and 100 nm.
July 29, 2019 24
M
KP_C
R

Microstructures
Totten George – Steel heat treatment 25
(Feathery)
(Acicular)
July 29, 2019 Faculty Development Program
M
KP_C
R

M
KP_C
R

Steel Classification
Steels can be classified by a variety of different systems depending on:
 The composition, such as carbon, low-alloy or stainless steel.
 The manufacturing methods, such as open hearth, basic oxygen process, or
electric furnace methods.
 The finishing method, such as hot rolling or cold rolling
 The product form, such as bar plate, sheet, strip, tubing or structural shape
 The deoxidation practice, such as killed, semi-killed, capped or rimmed steel
 The microstructure, such as ferritic, pearlitic and martensitic
 The required strength level, as specified in ASTM standards
 The heat treatment, such as annealing, quenching and tempering, and
thermomechanical processing
 Quality descriptors, such as forging quality and commercial quality.
M
KP_C
R

M
KP_C
R

Structural Steels
• A profile formed with a specific shape or cross sections
• Certain standards of chemical composition and mechanical
properties
Properties of structural steel include:
•Tensile properties
•Shear properties
•Hardness
•Creep
•Relaxation
•Fatigue
July 29, 2019 30
M
KP_C
R

Manufacturing of structural steel grades
M
KP_C
R

M
KP_C
R

Low alloy steels
Structural steels
Controlled rolled steels
HSLA
Micro alloy steels
“Strength increase along with toughness-unique
property of these steels”
Structure - fine primary ferrite grains
Strength increased by : redn in primary ferrite grain
size, controlled hot rolling, solid soln strengthening,
precipitation of very fine precipitate in ferrite grain by
microalloying
M
KP_C
R

Structural steel grades
 S195, S235, S275, S355, S420, S460
 S"235"J2’‘K2’’C’’Z’’W’’JR’’JO’’ - European Standard classifications
 S – denotes the fact that it is Structural Steel
 235 – related to the minimum yield strength of the steel (tested at a
thickness of 16mm)
 J2 / K2 / JR / JO – material toughness in relation to the Charpy impact or
‘V’notch test methodology
 W – Weathering Steel (Atmospheric Corrosion Resistant)
 Z – Structural steel with improved strength perpendicular to the surface
 C – Cold-formed
M
KP_C
R

 All these grades have major alloying elements as C and Mn. 0.2-0.22% max C
and 1.60 % max Mn. Have minimum yield strength of 235-355 MPa. Tensile
strengths of 350-650 Mpa.
 Applications are High Rise Buildings / Skyscrapers, Houses, Factories, Offices,
Shopping Malls, Road barriers, Bridges
 ASTM A36 steel is having no Mn and very minimum C - 0.026 %.
 ASTM A36 plate is a low carbon steel that exhibits good strength coupled with
formability. It is easy to machine and fabricate and can be securely welded.
A36 is a common structural steel plate that can be galvanized to provide
increased corrosion resistance.
 A36 plate can be used for a wide range of applications, depending on the
thickness and corrosion resistance of the alloy. Some of the products
manufactured using A36 structural steel plate are: Buildings, including pre-
fabricated buildings, warehouses, industrial and commercial structures,
Cabinets, enclosures and housings, Pipe and tubing.
M
KP_C
R

Typical stress strain diagram for different class of structural steel grades
M
KP_C
R

Structural steel @ OPJU
M
KP_C
R

IS 2062
IS2062 is a standard which is compulsory for a
manufacturer to have in India to produce Hot
Rolled Steel for Medium and High Tensile
Structural Steel.
It is issued by Bureau of Indian standards to
companies having the requisite infrastructure and
facilities to manufacture steel as per the IS 2062
specifications mainly for structural purpose.
M
KP_C
R

According to IS 2062 steels having Nine grades their sub-
qualities.
(A, BR, BO, C)
A: Impact test not required, semi-killed/killed
BR: Impact test optional; if required at room temperature; semi-
killed/killed
B0: Impact test mandatory at 0°C, semi-killed/killed
C: Impact test mandatory at –20°C, killed
M
KP_C
R

M
KP_C
R

ALLOYING ELEMNTS PERMISSIBLE LIMITS IN IS 2062
STRUCTURAL STEEL
M
KP_C
R

STRUCTURAL STEEL GRADES AND APPLICATIONS
M
KP_C
R

HSLA Classification
1. Weathering steels, designated to exhibit superior atmospheric corrosion
resistance
2. Control-rolled steels, hot rolled according to a predetermined rolling
schedule, designed to develop a highly deformed austenite structure that will
transform to a very fine equiaxed ferrite structure on cooling
3. Pearlite-reduced steels, strengthened by very fine-grain ferrite and
precipitation hardening but with low carbon content and therefore little or no
pearlite in the microstructure
4. Microalloyed steels, with very small additions of such elements as niobium,
vanadium, and/or titanium for refinement of grain size and/or precipitation
hardening
5. Acicular ferrite steel, very low carbon steels with sufficient hardenability to
transform on cooling to a very fine high-strength acicular ferrite structure
rather than the usual polygonal ferrite structure
6. Dual-phase steels, processed to a micro-structure of ferrite containing small
uniformly distributed regions of high-carbon martensite, resulting in a
product with low yield strength and a high rate of work hardening, thus
providing a high-strength steel of superior formability.
M
KP_C
R

Applications
Pipe lines Automobile parts Construction
M
KP_C
R

TMT?
• TMT bars or Thermo-Mechanically Treated bars are high-strength
reinforcement bars having a tough outer core and a soft inner core. Thermo-
Mechanically Treated bars or TMT bars are widely used for different
construction projects.
• With a unique metallurgical process that combines work hardening along with
heat-treatment to create robust and high strength bars from low-carbon steel,
TMT bars have a great demand.
Size: 5mm to 50 mm
Properties:
Ductility
Weldability
High tensile strength
Corrosion resistant
July 29, 2019 46
M
KP_C
R

Manufacturing of TMT
Bending, Tagging and
Packaging
Cooling BedWater Quenching &
Tempering
Infinite Rib Pattern
Production
Sourcing of Quality
Billets
Cutting of Billets Heating Rolling Mill
July 29, 2019 47
M
KP_C
R

Properties and grades of TMT
M
KP_C
R

Future developments in structural steels?
• Light steel
• Introduction of ALUMINUM in steel
M
KP_C
R

Steels for Rail Roads
 STEEL rails have been the material of choice for railways since the first
installation at Derby station in Britain in 1857.
 Indian Railway networks – Third Largest in the world
 Route length network is spread over 121,407 km, with 12,617 passenger
trains and 7,421 freight trains each day from 7,349 stations plying 23
million travellers and 3 million tonnes (MT) of freight everyday.
 Indian Railways is targeting to increase its freight traffic to 3.3 billion
tonnes by 2030 from 1.1 billion tonnes in 2017.
 Grade 700 / R260 was the starting point of development of rail steels.
 Grade 700 composition is of 0.5%C with 70% pearlite within the rail head.
 First step of development was to increase the toughness and wear
resistance of rail head.
 Development of 100% pearlitic steels for rails started. Grades 900 (R 300
HT) and 1100 (R350 HT) were developed. The interlamellar spacing of
pearlite maintained between 0.21 - 0.3 micrometres.
M
KP_C
R

Indian Railways requirements
• Lowest initial cost
– Rails
– Welding
– Installation
– Logistics
• Better life
• Least maintenance
• Lowest whole life cost
• Predictable and safe rail
M
KP_C
R

Rail Steel Grades according to IRS
July 29, 2019 52
M
KP_C
R

M
KP_C
R

Rail types
Flat Footed Rail are cheaper, distributes the train load to a great number of
sleepers, greater track stability, longer life
July 29, 2019 54
M
KP_C
R

Rail specifications
Weight and section of
rail governed by all
factors:
 Guage of track
 Max permissible
speed
 Type and spacing
of sleepers
 Depth of Ballast
cushion
 Heaviest moving
load
Flat Footed Rail
July 29, 2019 55
M
KP_C
R

Rail Road Construction
M
KP_C
R

Challenges in Indian Railways
• Factors such as increasing axle loads, greater traffic density, and stiffer vehicles
have led to more demanding duty conditions on the rail leading to more rapid
degradation through wear and fatigue.
• 1st Imp Factor: Axle Load (An axle load of 25 tonnes has become an
international norm in freight intensive railway systems in most countries. If the
Indian Railways had a 25-tonne axle load system, the gross weight of each
wagon would be 100 tonnes, implying an increase of 19 tonnes over the present
gross weight of 81 tonnes.)
• 2nd Imp Factor: Maximum Moving Dimension (no scope for any significant
increase in the width and height of the wagons on the Indian Railways)
• To solve the above issues following have to be taken to consideration:
– Proper metallurgical design
– Modify the existing manufacturing routes and Identify a proper technique to achieve
the required properties
– Develop heat treatment methodology for improving properties
– Produce a cost effective end product with satisfied properties according to the
railway standards.
M
KP_C
R

Need for development of new procedures of Heat
treatment of Rails
Development of in-line heat treatment technique of
rails. The purpose is:
1. Better hardness and strength along the case of rail
head compared to the conventional rails.
2. Increase the weldability better than conventional
rail grades
3. Produce medium strength weldable rails for
tangents and mild curves of heavy haul rails.
Adoption of slack quenching technique to generate
the required microstructure and properties in
modern rails
July 29, 2019 58
M
KP_C
R

Effect of Quenchants
July 29, 2019 59
M
KP_C
R

M
KP_C
R

Influence of cooling rate on the final microstructure of rail steels
Common Rail steel grades
July 29, 2019 61
M
KP_C
R

M
KP_C
R

Advantages of Head
Hardened Rails
High Strength
High Wear Resistance
Low residual stresses
Prolonged service life and enhanced safety
Economical and Cost Efficient with High
Lifecycle
High resistance to deformation caused by
compression
High resistance to brittle fracture
Low residual stresses after manufacturing and
straightening
Good weldability.
M
KP_C
R

New Steels for Rails
• Low carbon Bainitic Steels
• Disadvantage of pearlitic grades – poor toughness
Microstructure
Pearlitic
Bainitic
Fracture Toughness, MPa m0.5
30-35
50-60
July 29, 2019 64
M
KP_C
R

M
KP_C
R

Glimpse of Rail Head Hardening project of RUBM, JSPL at
OPJU
• In 1976 Nippon Steel developed a new head hardened (NHH) rail that is
continuously slack-quenched by air after being subjected to induction heating.
• In 1979, the company developed NS-II rail (Super rail), the purpose of which
was to prevent the welded joints from softening.
• Head Hardened Rails are used in high speed rails (> 250 KM/Hr.) for Bullet Trains.
• Since 2003, JSPL has make up its market in rails.
• Because of increases in train speed and freight car capacity aimed at improved
efficiency, rails are subjected to severer conditions than ever.
• The tonnage of trains has increased markedly, and the axle load and tangential
force or impact force applied to the rails by the wheels have become exceedingly
great. Also keeping in view of the number of train accidents in India, JSPL planned
to go towards the HH Rails.
• JSPL developed longest rails – 121 m after welding it is ~484 m.
M
KP_C
R

Rail Manufacturing setup at JSPL
Reheating Furnce (1270 deg C) Descaling Initial Rolling Tandem Rolling
IH (if necessary)Heat treatmentSamplingYard
M
KP_C
R

Initial sketch of prototype rail cooling module for
HT of rails
M
KP_C
R

Objectives of the project
1. Prepare the prototype of rail cooling setup.
2. Perform cold trails for examining the setup stability.
3. Replicate two recipes (used by RUBM during their trails) in the
prototype setup and compare the results.
4. Identify the initial parameters for the experiments.
5. Study the effect of parameters such as water flow pressure,
nozzle height, speed of rail, sample dwell time.
6. Record and investigate the Temperature – Time histories,
microstructure and mechanical properties of the trail samples.
M
KP_C
R

Trail
No.
Speed of
Rail
Water pressures, bar Nozzle
Height, mm
Heating
temperature
(deg.C) and
Soaking time
On
head
On
side
On
Foot
1 1.0 m/s 4 4 5.5
307 mm
900 & 5 min
2 5 5 6
3 1.2 m/s 6 6 7
4 7 7 7
5 1.0 m/s 4 4 5.5
277 mm6 5 5 6
7 1.2 m/s 6 6 7
8 7 7 7
Proposed Action Plan for trail experiments at OPJU
1. Replicate one/two recipes of the RUBM trails (0.6 m/s and 1.0
m/s).
2. *Following trails are planned to be conducted at OPJU site.
*indicates that the above parameters may vary depending on the
results obtained after attempting as mentioned in point 1.
July 29, 2019 70
M
KP_C
R

RHH Equipment installation at OPJU
M
KP_C
R

Utilization of the RHH equipment
• Study in brief the heat treatment of rails
• Study the variation of heat flux in samples
• Continuous casting issues can be solved
• Effect of various cooling media can be studied
• Various heat treatment techniques can be developed (such as
interrupted cooling)
M
KP_C
R

Collaborators and supporters for the RHH
project
M
KP_C
R

Thank you
M
KP_C
R

Alloy design for Structural and rail applications

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Alloy design for Structural and rail applications

Similar to Alloy design for Structural and rail applications (20)

Recently uploaded

Recently uploaded (20)

Alloy design for Structural and rail applications