In this presentation , i have mentioned various methods to improve strength ,ductility and toughness of low carbon steel

1. Approach to Simultaneous Improvement of Strength, Ductility & Toughness in
Steel
by
SOURAV GHOSH
ROLL NO- 13/MM/13
Under the supervision of
Dr. Joydeep Maity

2. Contents
 INTRODUCTON
 AIM
 GRAIN REFINEMENT
APPLICATION OF STEEL DUE TO HIGH STRENGTH
AND DUCTILITY
 EXPERIMENTS & RESULTS
 CONCLUSIONS
 REFERENCES

3.  INTRODUCTION
 Steel is an alloy of iron and other elements, primarily carbon that
is widely used in construction and other applications because of
its high tensile strength and low cost.
 Strength , Ductility and toughness are important mechanical
properties for the application of steel.
 Steel applications can be divided into five sectors: :
1.Construction 2.Transportation 3.Energy 4.Pakaging 5.Appliances
and Industry.
 With increasing carbon content ,it has been found that strength
increases but ductility decreases to some extent.
 Ductility and strength is the measure of soft phase and finer
grains of steel respectively.

4.  Toughness is the ability of a material to absorb energy and
plastically deform without fracturing. It is the measure of area
under stress-strain curve. So, toughness is the measure of
Strength and Ductility
 Austenite and finer ferrite grains is responsible for the
improvement of
strength, ductility and toughness of the steel.
 Grain refinement is used to increase Austenite and finer
ferrite grains in steel.
 Grain refinement can be used to increase the Strength,
Ductility and toughness in steel.

5.  AIM OF THE PROJECT
 TO INCREASE AUSTENITE PHASE AND FINER FERRITE GRAINS IN
STEEL BY DIFFERENT GRAIN REFINEMENT PROCESSES

6.  GRAIN
REFINEMENT
Grain
Refinement
 Grain refinement is the reduction
size of the grains within materials.
 Grain refinement is nothing but
grain boundary strengthening
which describes the relationship
between strength ,ductility with
grain size which can be
by hall Petch relationship.
 Hall Petch Relationship
σo = σi +kD-1/2

7.  APPLICATION OF STEEL DUE TO
HIGH STRENGTH AND DUCTILITY
HIGH STRENGTH
AND DUCTILE
STEELS ARE
BEING USED IN
VARIOUS
VEHICLES.

8. EXPERIMENTS & RESULTS

9.  ECAP PROCESS
 ELECTROPULSING TREATMENT
 INCREMENTAL DEFORMATION OF TRIP STEEL
GRAIN
REFINEMENT
PROCESSES

10.  ECAP
PROCESS
Conventional
Austenitization at 920°c
for 1 hour followed by air
cooling
3 Pass ECAP in four
different temperature
such as
150°c,200°c,250°c,300
°c
Optical microscopy
and SEM analysis
of the sample
EXPERIMENTAL PROCEDURE
Mechanical
property
determination
using Universal
Testing Machine
ELEME
NT
C Mn Si P S Al As Cu
% WT 0.1 0.42 0.08 0.029 0.05 0.002 0.032 0.02
CHEMICAL COMPOSITION OF THE SAMPLE TAKEN LOW CARBON
STEEL AISI14

11. EXPERIMENTAL RESULTS
MICROSTRUCTURAL
OBSERVATION
Optical micrographs taken on the plane perpendicular to
billet axis after three ECAP passes at temperature: a) 150°C;
b)200°C ;c)250°C;d)300°C.
Initial at 150°C At 200°C At 250°C At
300°C

12. SEM
MICROGRAPHS
AT a)150°C;b)300°C
At 150°C At 300°C

13. MECHANICAL
PROPERTIES AT
DIFFERENTTEMPERATURE
TECAP YS(MPa) UTS(MPa) Austenite
(%)
150°C 562 824 11.5
200°C 814 819 9
250°C 680 779 13.5
300°C 662 761 13
Initial
Sample
252 307 38
As we can see that amount of Austenite decreases
as compared to initial sample ; a post heat
treatment is required to increase the ductility of
the low carbon steel sample.
1. hold this sample at 300°C or more
temperature it will relieve the residual stress
that was produced during ECAP process.
2. Then sample is subjected to recrystallization
annealing with simultaneous quenching to
control the grain growth so that new austenite
grain can nucleate but it does not become
coarser as coarser grain gives less strength to
the material.
New finer austenite grains will gives more
elongation during deformation and it will
increase the ductility of the low carbon steel.
With increasing ductility of the low carbon steel ,
toughness will also increase as area under the
stress –strain curve of the annealed low carbon
steel will increase in some extent.

14.  ELECTROPULSING
TREATMENT
EXPERIMENTAL PROCEDURE
A strip specimen made up of low carbon steel
was online treated by a continuous
electropulsing where the strip was moving at a
constant speed of 14 m/min through a distance
of 300 mm between the two electrodes.
The current parameters including
frequency, root mean square (RMS)
current, amplitude and duration of
current pulses were constantly
monitored and recorded by using a
Hall effect sensor connected to an
oscilloscope
The temperature of the
strip specimen was
measured by using a
infrared thermoscope
Optical microscopy of
the specimen
Tensile testing of the
specimen using universal
testing machine
Element C Mn Si S P Cr
Wt.% 0.098 0.38 0.12 0.27 0.002 0.025
CHEMICAL COMPOSITION OF LOW CARBON STEEL STRIP
SAMPLE

15. EXPERIMENTAL
RESULTS
MICROSTRUCTURE
OBSERVATION
MECHANICAL PROPERTIES
AT Different temperature
SAMPLE
CONDITION
Voltage,
V
Frequency,
Hz
Temperatur
e, k
YS, MPa %elongatio
n
EPT1 180 500 674 371 47.5
EPT2 200 500 823 376 34.5
EPT3 180 700 883 426 22.6
INITIAL
SAMPLE
- - - 235 40
*EPT REFERS TO
ELECTROPULSING
TREATMENT
At cold
rolled
conditio
n
After
EPT1

16.  INCREMENTAL
DEFORMATION
OF TRIP STEEL
EXPERIMENTAL PROCEDURE
A low alloyed trip steel was taken whose main alloying elements
play an important role in controlling the transformation
processes and stabilizing retained austenite
The treatment schedule was simulated in a thermomechanical
simulator with precise temperature and deformation control.
Optical Microscopy & Tensile testing
The experimental program was divided into two parts. In the first part, the influence of 20-
step deformation in various temperature intervals was investigated. In the second, the
influence of the cumulative amount of deformation on structure refinement was explored.

17. EXPERIMENTAL
RESULTS
MICROSRUCTURE
OBSERVATION
20-step deformation with the smaller
deformation step:
900-720°C
MECHANICAL
PROPERTIES
After deformation within the
temperature interval between900
and 720°C, fine ferrite-bainite
structure with 15% of retained
austenite was obtained (Fig.1).
The tensile strength reached 832
MPa with ductility of over 32%.
We can increase ductility to more
extent by precipitation hardening.
So toughness of trip steel also
increases.
Fig.1

18.  The ECAP processing route Bc was performed at four different elevated temperatures and the billets were
pressed in three passes. Intensive and yet non-uniform strain in the billets, excluding the end regions, was
observed by optical microscopy.
 With controlled recrystallization of the ECAPED low carbon steel by controlling grain growth, Ductility of
steel can be increased than its initial value. Strength, Ductility and Toughness of low carbon steel can be
increased economically by ECAP Process.
 Electropulsing treatment of low carbon steel strip gives an optimum combination of strength and ductility at
180V in voltage and 500Hz in frequency ; leading to a combination of Tensile strength- elongation of 375
Mpa and 47.5 % which is better than any convention heat treatment process.
 Ductility, Strength and toughness of the Trip steel has successfully increased to some extent by
INCREMENTAL DEFORMATION OF TRIP STEEL.
 Among the above processes, Electropulsing treatment can improve strength, ductility and toughness of the
low carbon steel to a great extent. It is the best method for the improvement of strength, ductility and
toughness of steel.
CONCLUSIONS

19.  REFERENCES
 [1] GEORGE E. DIETER, Mechanical Metallurgy, pp.182
 [2] W.D. CALLISTER. Fundamentals of Materials Science and Engineering, 2nd ed. Wiley & Sons. pp. 252.
 [3] Hall, E.O. (1951). "The Deformation and ageing of Mild steel: iii discussion of results". Proc. Phys. Soc.
London. 64:747–753. doi:10.1088/03701301/64/9/303.
 [4] Osman Konuk, H. Erol Akata. “A Study on the Application of the ECAP to Surface plating”. International
journal of electronics; mechanical and mechatronics engineering vol.3 num 4 pp.(625-630).
 [5] S.M. Arab, A. Akbarzadeh. “The effect of Equal Channel Angular Pressing process on the microstructure of
AZ31 Mg alloy strip shaped specimens”. Journal of Magnesium and Alloys 1 (2013) 145e149
www.elsevier.com/journals/journal-of-magnesium-and-alloys/2213-9567.
 [6] Libor KRAUS, Jozef ZRNIK, Martin FUJDA, Miroslav Cieslar.” Grain Refinement of Low Carbon Steel by
Ecap Severe Plastic Deformation”
 [7] Liuding WANG, Laizhu JIANG, Ming ZHU, Xiao LIU and Wangmin ZHOU. “Improvement of Toughness of
Ultrahigh Strength Steel Aermet 100”. J. Mater. Sci. Technol., Vol.21 No.5, 2005.
 [8] C. Capdevila, C. Garcia-Mateo, F. G. Caballero and C. García de Andrés MATERALIA Research group.”
Neural Network Model for the Improvement of Strength – Ductility Compromise in Low Carbon Sheet Steels”.

20. THANK YOU