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Internship Report

Structure Property Correlation of Thermo-

Mechanical Tempered Bars & Hot Rolled Coil

Submitted by

Anubhav Jain#

Enrolment no.: Mett 32/13

National Institute of Technology – Srinagar

Guided by

Mr. Neel Kant*

Research and Development Department

Jindal Steel Works – Dolvi

Head of Department

Mr. Pardip Kumar Patra*

Research and Development Department

Jindal Steel Works – Dolvi

* #

Duration: 4 Weeks w.e.f. 1/02/2016

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Acknowledgement

During this industrial internship in JSW (Jindal Steel Works) Dolvi, Maharashtra, in

Research and Development Department was a memorable one for me as it was rich in

experience sharing and helped me to discover my potential. I had so many rich experiences

and opportunities that I personally believe will forever shape and influence my professional

life while fostering personal growth and development.

In this report, I hope to highlight the work that I have performed and learned. Working here

not only given me the industrial experiences, but also teaches me how to sustain in tough

environment. Good working conditions and friendly behaviour of everyone inspires me to

be productive in work.

These few details lead me to realize that, like all human endeavours, this report is not perfect

and may contain errors and shortcomings.

Thus, I remain open to all criticisms and suggestions which could present me with new

sources of inspiration as I develop in my ability to research and learn.

This report would not have been possible without the contribution and collaboration of

others. My sincere gratitude:

Mr. Pardip Kumar Patra, HOD, R&D, JSW Dolvi.

Mr. Mrigandra Singhai, AGM, R & D, JSW Dolvi.

Mr. Srimanta Sam, Senior Manager, R & D, JSW Dolvi

Mr. Amit Mogale, Deputy Manager, R & D, JSW Dolvi.

Mr. Dravid, Jr. Manager JSW Dolvi

Mr. Krishana, Deputy Manager JSW Dolvi.

Mr. Vivek, JSW Dolvi.

To all of you, I extend my deepest gratitude and always owe my respect to them.

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History

JSW was set up as Nippon Denro Ispat Limited in May 1984 by founding Chairman Mr M.

L. Mittal. The company have operations in iron, steel, cement, energy and infrastructure. It is

an integrated steel plant, located at Dolvi in the state of Maharashtra.

The 1,200 acres (4.9 km2) Dolvi complex houses the 3.3 million tonnes per annum HR Coils

plant, and 1.5 million tonne per annum TMT Bar Mill (Newly established) which combines

the latest technologies the Compact Strip Process (CSP) introduced in Asia. It is

headquartered at Mumbai and employs about 3000 people.

On 21 December 2010 it was declared that JSW Steel will buy this industry at $3 billion to

emerge as India's largest private producer of the steel. On April 2013, the complete merger

has been completed. Currently this industry is owned by Mr. Sajjan Jindal.

The Dolvi unit features a sponge iron plant (1.6 million tonnes per annum), a blast furnace, a

sinter plant, a hot strip mill (3.3 million tonnes), an oxygen plant and a lime calcining plant.

The plant uses a combination of ConArc and CSP processes to produce hot rolled coils.

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List of Abbreviation

TMT Thermo mechanical tempered

HR Hot Rolled

MTPA Million tonnes per annum

MM Millimetre

MPA Mega Pascal

YS Yield strength (MPa)

UTS Ultimate Tensile Strength(MPa)

CSP Compact Strip Process

QTB Quenched & Tempered Bar

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Contents 1. Introduction ............................................................................................. 7

1.1 Safety awareness ............................................................................... 7 2. Literature Review ................................................................................... 8

2.1 Compact Strip Process (CSP)…………………………………...….8 2.2 ConArc Process (Converter & Arcing) ............................................. 8 2.3 Quenched & Tempered Bars (QTB) ................................................. 8 2.4 Standards of TMT and HR Coil ........................................................ 9

2.4.1 TMT Bar Chemical Composition ............................................... 9 2.4.2 TMT Bar Mechanical Standards ................................................. 9 2.4.3 HR Coil Chemical Composition ................................................. 9 2.4.4 HR Coil Mechanical Standards ................................................... 9

2.5 Testing ................................................................................................. 10 2.5.1 Chemical Analysis ........................................................................ 10 2.5.2 Mechanical analysis ..................................................................... 10

2.5.3 Microstructure .............................................................................. 10 3. Projects .................................................................................................. 12

3.1 TMT Bars: ....................................................................................... 12 3.1.2 Observation: .............................................................................. 13 3.1.3 Inference: .................................................................................. 13

3.2 HR Coil:........................................................................................... 15 3.2.1 Observation: .............................................................................. 15 3.2.2 Inference: .................................................................................. 16

Appendix A: IS:1786:2008…..……………………………………….…18

Appendix B: Mechanical Properties…………………………………….19

Reference………………………………………………………………..20

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1. Introduction

Industrial Training in Research and Development, Deartment of Jindal Steel Works, Dolvi,

Maharastra has given chance to work in their newly established TMT Bar Mill installed by

'Danieli Italy', with capacity of 1.5 MTPA (Million tonnes per annum) which produces TMT

bars of different diameters from 8 MM to 40MM and HR Coil Mill with capacity of 3.3

MTPA (Million tonnes per annum), which produces Coils of thickness from 1.2 MM to

25MM and 25 tonn.

In this period of training, I worked on the Microstructure of TMT bars & HR Coil,

Mechanical properties of Fe500D Grade of bar of diameters 25MM & 40MM and TR34Al Z

of HR Coil.

In TMT Bar, I figure out the Microstructures, Tensile test and Chemical composition.

Due to trial of TMT bar mill it become difficult to go further, so they suggested me to also

work on HR Coil also.

In HR Coil, I worked on the Microstructures of Coils with excess of Nitrogen and normal

Nitrogen coil and find correlations with the YS, UTS and Grain Size of Microstructures in

both of them. I used two samples of Excess Nitrogen and one sample of normal Nitrogen.

TMT Bars are used for General reinforcement of high rise building, bridges and other

concert constructions; it is highly used in earthquake prone areas.

HR Coils are used for fabrications like automobiles, pipes, gas cylinders, etc.

1.1 Safety awareness

Wear safety shoes or boots, preferably with steel toes.

Wear a hard hat while framing or when required by supervisor.

Wear safety glasses when working with any power tool and when recommended by

the supervisor.

Wear dust masks when needed.

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2. Literature Review

It is essential to understand some basic process and terms used in this report, I refer some

papers. Hence brief ideas of these processes are as follows.

2.1 Compact Strip Process (CSP)

CSP combines cost-effective and environmentally friendly production with a high

productivity and excellent strip quality in an ideal way. CSP stands for Compact Strip

Production. In a CSP caster, the liquid steel is cast into thin slabs which after temperature

equalisation in a tunnel furnace are rolled directly in the rolling mill without roughing

(removal of scales).

2.2 ConArc Process (Converter & Arcing)

ConArc combines two traditional methods – making steel using solid charge like

steel scrap, pig iron or sponge iron as well as making steel through the blast furnace route.

This provides the unit with the flexibility of using any combination of solid charge and liquid

hot metal. It chooses feed mix depending on market demands.

2.3 Quenched & Tempered Bars (QTB)

QTB plus is a recently established model by ‘Danieli Italy’ in TMT bar mill, which is

used for the better control for mechanical properties of quenched & tempered bars. This

gives an accurate estimation of YS, UTS and Hardness at different points across the section

of the bars. It calculates the thermal histories of different segments, finally the system uses

these histories to estimate the final microstructures.

This system is useful in producing the desired mechanical properties through proper process

control. It can be used to design new grades of bars with superior quality such as improves

elongation and bend ability.

An Additional Neural Network (ANN) model is set up to considered uncertainties of

processing in the plant.

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2.4 Standards of TMT and HR Coil

Followings are the standards used by the JSW Dolvi, for the manufacturing of the

above products.

Grade used for TMT Bars is: FE500D

Grade used for HR Coil is: TR34AL Z

2.4.1 TMT Bar Chemical Composition

Components Percent Composition

Carbon 0.25

Manganese 0.4

Sulphur 0.04

Phosphorous 0.04

Sulphur and Phosphorous 0.07

2.4.2 TMT Bar Mechanical Standards

YS(MPa) UTS(MPa) %EL

500 565 16%

2.4.3 HR Coil Chemical Composition

Components Percent Composition

Carbon 0.065

Manganese 0.650

Copper 0.010

Vanadium 0.030

Nitrogen 90

2.4.4 HR Coil Mechanical Standards

YS(MPa) UTS(MPa) %EL

335 390 27

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2.5 Testing

Different types of techniques are used to determine mechanical, chemical and microstructure

of the sample. These techniques are described as follows:

2.5.1 Chemical Analysis

The chemical composition of the sample is obtained by using Spectrometer.

It is used to measure a spectrum. Generally, a spectrum is a graph that shows intensity as a

function of wavelength, frequency, energy, momentum, or mass. It uses arc and spark

excitation, which produces spectrum which is further judged in to get the composition.

It is very fast; it hardly takes a minute to give the result of chemical composition.

It is used for both TMT and HR Coil.

2.5.2 Mechanical analysis

Mechanical analysis is done to obtain the YS, UTS and %Elongation of the sample.

For this purpose, Universal testing machine is used, in which a certain length of sample is

taken in the account for e.g. 300 MM length is used for HR Coil and 600 MM length is used

for TMT Bar. In this machine, sample is tightened properly at the ends and gradually load is

increased continuously until breaking is done. Each and every data is recorded

computationally.

2.5.3 Microstructure

Obtaining microstructure of a sample involves few steps, like sampling, mounting

(optional), grinding, polishing and etching.

Sampling: Sampling of material is done in which the maximum amount of

information can be revealed.

Mounting: It is done when the sample is not in the proper shape to hold during

grinding and polishing, I have done cold mounting for the HR Coil sample. Cold

mounting epoxy resin is used to mount the HR Coil sample with the Benzene

Solution.

Grinding: Rough grinding is done to provide excellent surface finish to the sample

in order to make it suitable for the further grinding. First we use 220 grit size emery

papers, and then we go for 320, then 600. Then 1200 by changing orientation of

sample by 90º to erase the pervious scratches.

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Polishing: Now samples get polished by the velvet paper, with aerosol spray and

diamond paste to give it a mirror finish to its surface.

Etching: Study of macrostructure is done by preparing a Nital solution which

contains 2 to 3 percent Nitric Acid with 98 to 99 percent balanced ethyl alcohol.

Now sample is dipped in the solution for some time until some darkness is seen in

the shining surface of the sample. In TMT bar sample three different rings can be

seen and light darkness is seen in the HR Coil sample.

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3. Projects During this internship, I have performed my work on TMT Bars and HR Coil,

information on the experimental procedures and inference are as follows:

3.1 TMT Bars:

A sample each from the two TMT Bars of the diameter 25 MM and 40 MM are taken

and different techniques of testing (mentioned above) are applied to get different results.

Grade of TMT bar used here is: FE500D.

Terminologies:

1. Austenite: A solid solution of one or more elements in face centred cubic iron. The

solute is generally assumed to be carbon.

2. Bainite: A decomposition product of austenite consistency of an aggregate of ferrite

and carbide. In general, it forms at temperature lower than those where very fine

pearlite forms and higher than those where martensite begins to form on cooling. Its

appearance is feathery, it formed in the upper part of the temperature range and

acicular (needle shaped), resembling tempered martensite, if formed in the lower part.

3. Martensite: Under slow or moderate cooling rates, the carbon atoms are able to

diffuse out of the austenite structure, the iron atoms then move slightly to become

BCC. That gamma to alpha transformation takes place by a process of nucleation &

growth and is time dependent with a still further increase in the cooling rate,

insufficient time is allowed for the carbon to diffuse out of the solution and although

some movement of the iron atom takes place, the structure cannot become BCC while

carbon is trapped in solution. The resultant structure called martensite, is a

supersaturated solid solution of Carbon trapped in a BCC tetragonal structure.

4. Tempered Martensite: After quenching, when the rods are moved on to cooling bed,

then the core start radiating heat. During this cooling of the core, heat radiates

outward and start increasing temperature of martensite ring which is formed during

quenching, hence martensite get tempered and form

tempered martensite, and hence toughness of the rod increases.

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3.1.2 Observation:

1. 25MM Diameter TMT Bar:

25 MM

YS

(MPa)

UTS

(MPa) %EL %TE W/L

THICKNESS OF

MARTENSITE RING

SAMPLE

1 594 717 16.8 7.55 3.6902 1.7116 MM

2. 40MM Diameter TMT Bar:

40 MM

YS

(MPa)

UTS

(MPa) %EL %TE W/L

THICKNESS OF

MARTENSITE RING

SAMPLE

1 542 697 17.5 8.3 9.76 2.9 MM

3.1.3 Inference:

1. The mechanical properties depend on the thickness and the distribution of the

different phases.

2. The rim formation depends on the quenching operations.

3. The control property is therefore, achieved through desired rim thickness and corrects

combination of microstructure across section.

4. Microstructure formed can be characterized in three different sections namely Ferrite

and Pearlite (core), Banite (Middle ring), and Tempered martensite (outermost ring).

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FOR 25MM

Grade –

FE500D

200X 500X 1000X

Centre

Bainite

Tempered

Martensite

For 40MM

Grade –

FE500D

200X 500X 1000X

Centre

Bainite

Tempered

Martensite

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3.2 HR Coil:

Three different samples are chosen, two are the excess nitrogen sample and the one is

the normal nitrogen sample. In this experiment, comparison between these samples is plotted

in graph v/s YS, UTS, %EL and ASTM Grain Size.

Terminologies:

1. Strain-aging: The changes in ductility, hardness, yield point, and tensile strength that

occur when a metal or alloy that has been cold worked are stored for some time. In

steel, strain aging is characterized by a loss of ductility and a corresponding increase

in hardness, yield point, and tensile strength. This happens due to presence of excess

Nitrogen in the material.

2. Ductility: It is a solid material's ability to deform under tensile stress; this is often

characterized by the material's ability to be stretched into a wire.

3. ASTM Grain Size: Standard Test Methods for Determining Average Grain Size.

ASTM E112 is used as standard for the same, in this method we take microstructures

at 100X magnification, and apply different methods such as grain interaction method

and grain plain-metric method to obtain the grain size. Under this experiment of

finding the grain size we use ‘Grain plain- metric’ method. It should be noted that, as

the ASTM Grain size increase with the decrease in grain size.

3.2.1 Observation:

Sample N(ppm) YS(MPa) UTS(MPa) %El

ASTM

Grain

size(Edge)

ASTM

Grain

size(Centre)

Grain

Size Mid

Thick

(Micron)

Grain

Size

Edge

(Micron)

Normal* 75 370 460 35 10.15 10.08 10.90 10.67

B** 150 400 475 34 10.26 10.07 10.95 10.26

C*** 265 450 520 32 10.37 10.30 10.11 9.87

*Sample Normal contains normal amount of nitrogen.

**Sample B is taken as the sample from excess nitrogen contained coil.

***Sample C is taken as the sample from excess nitrogen contained coil.

Images are attached below.

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0

100

200

300

400

500

600

50 100 150 200 250 300

Nitrogen (ppm)

Str

en

gth

10.05

10.1

10.15

10.2

10.25

10.3

10.35

10.4

YS

UTS

GS Subsurface

GS Mid

Thickness

Plot between Nitrogen (ppm) v/s Grain size (secondary axis) v/s Strength (Primary axis)

3.2.2 Inference:

1. With the increase in Nitrogen concentration the grain size decreases and ASTM grain size

increase.

2. With increase in Nitrogen concentration the YS and UTS increase and Elongation

decreases, which confirms the strain aging effect.

3. The grain size in mid thickness (centre) is more as comparative to subsurface (edge), it is

because of the cooling process, edge cools faster than the mid hence centre get sufficient

time to expand its grain size.

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SAMPLE HR COIL (N-75 ppm)

Normal

HR COIL (N-150 ppm)

B

HR COIL (N-256 ppm)

C

Subsurface GRADE-

E34

(TR34AL^)

Mid

thickness GRADE-

E34

(TR34Al^)

^ Grade named by JSW.

Images from Subsurface and mid thickness at 100X.

Magnificati

on

NORMAL B C

AT 200x

AT 500x

Arbitrary images with different magnification.

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Appendix A: IS 1786:2008

IS No. Title

228 (Parts 1 to 24) Methods for chemical analysis of steels

1387:1993 General requirements for the supply of

metallurgical materials (second revision)

1608:2005 Method for bend test (second revision)

1599:1985

Metallic material - Tensile testing at

ambient temperature (third revision)

2062:2006

Hot rolled low, medium and high tensile

structural steel (sixth revision)

2770 (Part 1):

Methods of testing bond in 1967

reinforced concrete: Part 1 Pull-out test.

9417:1989

Recommendations for welding cold-

worked steel bars for reinforced concrete

construction (first revision)

11587:1986 Structural weather resistant steels

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Appendix B: Mechanical Properties

%EL: Elongation: The increase in length of a tensile test piece under stress. The

elongation at fracture is conventionally expressed as a percentage of the original

gauge length of a standard test piece.

Percentage Total Elongation at Maximum Force: The elongation corresponding to

the maximum load reached in a tensile test (also termed as uniform elongation).

UTS: Tensile Strength: The resistance of a material to breaking under tension. It can be formulated as the maximum load reached in a tensile test divided by the

effective cross-sectional area of the gauge length portion of the test piece (also

termed as ultimate tensile stress).

YS: Yield Stress: The stress at which a specific amount of plastic deformation is

produced. Stress (that is, load per unit cross-sectional area) at which elongation first

occurs in the test piece without increasing the load during the tensile test. In the case

of steels with no such definite yield point, proof stress shall be applicable.

0.2 Percent Proof Stress: The stress at which a non-proportional elongation equal to

0.2 percent of the original gauge length takes place.

ASTM: American Standards of testing and materials, it is international standards for

certify standards.

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References

1. Shyam Steel, Hand Book On TMT Bars.

2. A. Mukhopadhyay, L. M. Galasso, M. Ena, G. Buzzi, Technological

Papers, Danieli Automation.

3. IS:1786:2008, Fourth Revision, Bureau Of Indian Standards, 2008.

4. K Priyesh, Studies on Properties of TMT Steels for Structural

Applications, International Journal of Engineering Research &

Technology (IJERT), August – 2013.