Internship Report-ISL-2012 Yaseen Raza

2012

YASEEN RAZA

NED University of Engineering

And Technology

INTERNSHIP REPORT

Yaseen Raza Ned University Of Engineering And Technology Page 2

INTERNSHIP

REPORT

SUBMITTED TO

MR. SHERAZ BHATTI

DEPUTY MANAGER CRM

SUBMITTED BY

YASEEN RAZA (MY-50)

NED UNIVERSITY OF ENGINEERING AND TECHNOLOGY

BATCH: 2009~2010

DURATION: 21ST MAY 2012 TO 30TH JUNE 2012


ACKNOWLEDGMENT

Starting with the name of Allah who is the most merciful and

beneficent

My report work has accomplished under excellent guidance and

supervision of production and management team of

International Steels Limited, Karachi. I offer my heartiest

gratefulness to ISL team for its step to step guidance and close

supervision during the conduct of all the period of internship at

ISL.

No acknowledgement could ever adequately express my

obligations to my affectionate parents for their all inspirations

and guidance which always motivated us to carry ourselves

through the noblest ideas of life and solving all troubles and

boosted my moral to fly high to accomplish our goals.

I convey special thanks to my dear class adviser MR

IFTIKHAR AHMED CHANNA, NED University for his

excellent, efficient, accurate and reliable help to completion of

this internship as well as completed our report.


I also convey special thanks to CRM plant production team

MR Yasir Sohail (SR.Manager CRM Operations)

MR Sheraz Bhatti (Deputy Manager CRM)

MR Imran Wasti (Deputy Manager CRM)

MR Danish Aftab (Asst.Manager CRM)

MR Abu Talha Kalimi (Asst.Manager CRM)

MR Umair baig (Deputy Manager CRM)

MR Shamsher Ali (Asst.Manager CRM)

MR Faraz Shafiq (Asst.Manager CRM)

MR Danish khan (Asst.Manager CRM)

MR Waseem (Operator Pickling)

MR Ayaz (Sr.shift Incharge Annealing)

MR Farhan (Operator Annealing)

MR Tasawar (Operator Rewinding)

MR Ahsan Munir (Shift Incharge Skin Pass)


INDEX

Sr. No Plant Description PG.NO

1 Pickling 7-23

2 4 Hi Mill 24-34

3 Rewinding 34-37

4 Annealing 37-41

5 Skin pass Mill 42-44

6 Roll Grinding 44-45


International Steels Limited

Process Flow Chart

HR Yard

Pickling

Rewinding 4 Hi Mill

Annealing

Galvanizing Plant

Skin Pass Mill

SL/CTL

SL/CTL

Finish Product


INTRODUCTION TO PICKLING:

Pickling is a metal surface treatment used to remove impurities, such as

stains, rust or scale from ferrous metals. A solution called pickle liquor,

which contains strong acids, is used to remove the surface impurities. It

is commonly used to de scale or clean steel. The hydrogen from the acid

reacts with the surface and makes it brittle and causes cracks. Because of

its high reactance to treatable steels, acid concentrations and solution

temperatures must be kept under control to assure desired pickling rates.

Pickling process is divided into three sections: Entry section, process

section, exit section.

ENTRY SECTION:

The process from feeding coil at the uncoiler mandrel and till the sheet is

given few wraps at the recoiler, is called threading. Coil from the HR

yard is first picked by crane and transfer to coil trolley, than it is moved

to pickling shop. Maximum three coils can be loaded at a time on the

coil trolley. Coils are placed on to the saddle than fed to uncoiler

mandrel by coil car. This mandrel cans expands or collapse according to

internal diameter of the coil. Uncoiler drive side and operator side can be

controlled manually or can be auto control. Starting face of coil is called

tongue end and last end is called fish end. Tongue end has to be sheared

b/c as sheet moved during threading; it may hanged/fix in support rolls.

As the tongue end is sheared, scrap system table moves up and sheared

piece fell into scrap box.

Sheet is flattened by moving the flattener rolls (#1 & #2) up and down.

Side guide/Centre guide assembly is used to keep sheet at the center

position during threading. Sheet is passed through def rolls, pinch rolls

then finally to the pickling tank no 1. Squeeze rolls are attached at the

http://en.wikipedia.org/wiki/Metal

http://en.wikipedia.org/wiki/Rust

http://en.wikipedia.org/wiki/Mill_scale

http://en.wikipedia.org/wiki/Ferrous

http://en.wikipedia.org/wiki/Strong_acid

http://en.wikipedia.org/wiki/Steel


starting and end of each tank so that acid from 1 tank may not enter to

another tank.

PICKLING PROCESS SECTION:

Processing section is the main section in pickling process sheet is passed

through different ART`s having lower, middle and higher concentration

of acid. There are three acid recycling tanks. Each tank of acid is heated

by heat exchangers through steam by counter flow action. Acid is

entered through heat exchange through bottom and steam is passed from

top.

TANK CONCENTRATION:

First tank has 3-8% conc. In this iron content is max i.e. (98-120g/lit)

Second tank has 8-14% conc. In this iron content lower i.e. (35-50g/lit).

Third tank has 14-18% conc. In this iron content is lowest i.e. (Nil Fe)

ACID FLOW:

Fresh acid is provided to 3rd ART. Its overflow goes to ART 2 than

overflow of ART 2 goes to ART 1. From here it goes to spent acid tank

then ARP plant.

Pump sucks the acid from ART and transfer to heat exchangers. As acid

enter heat exchangers it is heated by steam till 80-85°c then valve of

steam is closed. Heated acid goes to tank, from tank to ART. Pump

again transfers acid to tank and then process continues.

When level of acid is increased from 11 tons in ART 3 it overflows to

ART 2. In ART 2 heating process is same i.e. heated by steam in heat

exchangers. Construction of ART 3 is at a bit higher than ART 1 and

ART 2. Similarly an ART 2 level is higher than ART 1 so as to overflow

easily. Squeeze rolls are attached at the ends of each tank to squeeze


acid, so that concentration of each tank may not get mixed. Since acid is

heated, fumes are generated. They may damage wall roofs and other

equipment so they have to be condensed.

SCRUBBER:

Scrubber is used to condense acid fumes. Each tank has yellow pipe

which is used to transfer fumes from tank to scrubber. Blower is used to

suck fumes from tanks and transfer to scrubber.

Scrubber has three floors each floor is filled inside with some fibers and

shower of water to convert these acid vapors into liquid. At a rate of

350Lit/hr, water is delivered to tower. Water is provided at the bottom,

pump suck this water and delivered it from the top. This acidic water is

than transfer to rinse conc. tank.

Certain fumes do not condense and moved to next chamber. Again water

is sprayed from the top, the water become acidic and this goes to

previous tank. Now remaining fumes are exhaust by a chimney by a fan

which blows away fumes from this section.

RINSE SECTION:

This section consists of series of chambers. Its function is to remove acid

droplets from sheet by spraying of water. First there is a rinse conc. tank.

In which water is sprayed by set of two nozzles. Water is provided from

scrubber section; water is pumped by pump and transferred to tank.

Again here it runs a cycle means acidic water is sprayed on sheet than

returns to tank, it goes on until as its condition become dead it is

delivered to ARP. There are 5 rinse tanks; in each there is a set of

nozzles and set of squeeze rolls at start and end of each section. Fresh


water is provided to tank 5 its overflow goes to tank#4 and then to

tank#3, than to tank#2, than to tank#1.tank#2&1 have same acidic nature

or it may go to ARP. At end of tank#5 there is a pair of two squeeze

rolls.

PICKLING EXIT SECTION:

As sheet came out from rinse section, it may have some water droplets

at the edges. Edge knife blower is used to remove water from edges of

sheet then sheet is passed in hot dryer, in which heated air is used to dry

the sheet. Temperature is about 100-200°c in hot air dryer. Center guide

assembly is used to maintain sheet`s position at the centre.

After passing through pinch rolls and deflector rolls sheet is fed to

recoiler mandrel where it is fixed in recoiler mandrel. Mandrel collapse

then sheet is fixed in it and mandrel collapse again and given few wraps,

than tension is provided by tension units (#1 & #2). Line starts and

process goes on. Fish end/last end of sheet is sheared then coil car

moves in. pusher plate pushes the pickled coil on to coil car than it is

transferred to 4-HI plant.

ASSIGNMENTS OF PICKLING:

Following assignments were given by MR Danish Aftab & MR Imran

Wasti during our learning at pickling plant.

ASSIGNMENT # 1

Task: To analyze the problem and observe how it is removed

NAME OF THE PART:

The name of the given part is side guide assembly. It is also called center guide

assembly.


FUNCTION:

The function of center guide assembly is to guide the sheet towards the

center.

It is only used during the charging of the sheet at the entrance and exit

during recoiling.

It consists of two balancing shafts at the bottom and a lead screw.

Two blocks move on the lead screw supported by the balancing rods.

On lead screw the threads are on opposite separated by a bush which is

mounted through dowel pins

Two vertical side rollers which support movement of the sheet

FAULT:

When sheet moved away from its path it pushed one guide roll too much that its

alignment became out. This led to non uniform movement of side guide rolls.

MAINTENANCE:

For maintenance assembly is turned upside down. Bush which separates the two

lead screw rods is uncoupled; alignment is adjusted and coupled again.

TIME REQUIREMENT:

Total approximated time for maintenance of center guide assembly is 2 hours.

ASSIGNMENT # 2

TASK:

“To study and observe installation of spent acid tank.”

I had been provided the diagram of tank and parts detail.

This tank was fabricated at Lahore then delivered to ISL. From main gate, it

was transferred to pickling entrance gate by truck.

lifter was used to lift the tank from hook

Accessories of tanks were also provided in a box.

Lifter put both of tanks & box on coiler & delivered inside the pickling shop.


List of all accessories was provided from which all parts were verified.

Reducer FRD 80x mm was missing.

Tank was lifted from coiler & was placed on the floor in horizontal position

b/c if we lift it vertically it nozzle may get damaged.

It was then turned in vertical position then transferred to its place.

Now its position was adjusted so as to connect necessary accessories like

overflow pipe & drainage pipe etc.

ASSIGNMENT # 3

Pickling Entry section:

1. CRANE:

It is used to pick the coil from the coil yard. Its capacity is 30 tons

2. COIL CAR:

Pick coil is then transferred to the coil car. Maximum two coils can be placed on

coil car.

3. BABY COIL CAR:

It is used to transfer coils from the coil car to the saddle and also to uncoiler. It is

hydraulically operated. It has two buttons on the panel.

*Baby coil car (In/Out)

*Baby coil car (Lift/Lower)

4. SADDLE:

It is the place where extra coils are placed so that our operation remains

continuous.


Description Of Entry Panel Buttons And

Their Functions:

5. UNCOILER:

It is used uncoil the coil for processing. It has four buttons on the panel for

controlling it.

*Uncoiler (Operator side In/Out)

*Uncoiler (Driver side In/Out)

*Uncoiler (both side in and both side out)

6. UNCOILER MANDREL:

It is that part where the coil is attached. It has two buttons on the panel,

*One for the expansion of the mandrel

* Other for mandrel collapse.

7. UNCOILER HOLDS DOWN:

It is that part, which is used to hold the sheet so that it may not fall backward

because of its weight. One button on the panel is used for upward or downward

movement.

*uncoiler hold down (up/down)

8. PEELER TABLE:

Peeler table is used to make the face of the sheet and push the sheets towards pinch

rolls. It also acts as support. Two buttons are placed (up/down) and (Lift/lower).

*Peeler table (up/down)

*Peeler table (lift/lower)


9. FLATTENER PINCH ROLLS:

They are used to hold the sheet and remove edge defects. Also have two buttons.

*Flattener cum pinch rolls (up/down)

*Flattener cum pinch rolls (forward/reverse)

10. FLATTENER:

Flattener rolls are used to flat the face of the sheet and there are 5 rollers for

flattening, 3 on downward side and 2 on upward side. Two upward sides one can

move only and individually as well.

*Flattener rolls#1 (up/down)

*Flattener rolls#2 (up/down)

*Quick lift for quick movement of both in any emergency.

*Flattener (increase/decrease) this button is used to increase or decrease the speed

of the rolls.

11. CENTER GUIDE (UNCOILER):

When the sheet is out, it is used to place the sheet on center, it can be manually be

operated and automatically as well.

*Center guide (auto/manual)

12. SHEAR CUTTER:

To cut the face of the sheet, this is treated as scrap. One button named entry shear

mode safe has two options (manual/cut). For cut only there is one more button

named cut which we press it will cut the sheet. Cutter movement is not operator’s

control. For manual only there is one more button named entry

* shear (up/down) which controls the movement of the shear cutter.


13. SCRAP SYSTEM TABLE:

It is used to place the table upward so that scrap which is cut through shear cutter

does not go forward on the line.

*Scrap system table (up/down)

14. CENTER GUIDE ASSEMBLY:

When sheet is out of center then it is used to place the on center.

*Side guide (in/out)

15. EDGE TRIMMING:

If the requirement is of less sheet width then we use edge trimmer to cut the

desired sheet width. Two buttons are used on the panel.

* Edge trimmer (up/down) *Edge trimmer (forward/reverse)

16. EDGE TRIMMER HOLD DOWN:

It is used to hold the sheet when trimming is performed.

*Edge trimmer hold down (up/down)

17. SCRAP WINDER:

It is used to wind the scrap which is cut through edge trimmer.

*Driver side (in/out)

*Operator side (in/out)


ASSIGNMENT # 4

Pickling Process Section:

Processing section is the main section in pickling process sheet is passed

through different ART`s having lower, middle and higher concentration of

acid.

There are three acid recycling tanks. Each tank is heated by regenerates

through acid in stem by counter flow action.

Acid is entered through heat exchange through bottom and steam is passed

from top.

First tank has 3-8% conc. In this iron content is max i.e. (98-120g/lit)

Second tank has 8-14% conc. In this iron content is max i.e. (35-50g/lit)

Third tank has 14-18% conc. In this iron content is max i.e. (Nil Fe)

Fresh acid is providing to 3rd ART.

Its flow overflow goes to ART 2 than overflow of ART 2 is gone to ART 1.

From here it goes to spent acid tank then ARP.

Pump sucks the acid from ART than to HX. As acid enter HX it is heated by

steam till 80-85 then valve of steam is closed. Acid goes to tank from tank to

ART then suck by pump again transfer to tank and then process kept going

on.

When level of acid is increased from 11 tons in ART 3 it is overflow to ART

2. In ART 2 heating process is same i.e. heated by steam in HX.

ART 3 is at a bit higher than ART 1 and ART 2.

An ART 2 level is higher than ART 1 so as to overflow easily.

Squeeze nuts are attached at the ends of each tank to squeeze at acid. So that

conc. of each tank may not get mixed.

Since acid is heated fumes are generated.

4 tons of acid is flowing in pipes. They may damage wall roofs and other

equipment so they have to be condensed.


Scrubber:

Scrubber is used to condense acid fumes each tank has yellow pipe which is

used to transfer fumes from tank to scrubber. Blower is used to suck fumes

from tanks and transfer to scrubber.

Scrubber has three floors each floor is filled inside with some fibers and

shower of water to convert these acid vapors into liquid. 350L/hr water is

delivered to tower.

Water is provided at the bottom pump suck this water and shivered it from

the top.

This acidic water is than transfer to rinse conc. tank. Certain fumes do not

condense and moved to next chamber again water is sprayed from the top,

the water become acidic and this goes to tank. Now remaining fumes are

exhaust by exhaust by a chimney.

A fan is used to blown away fumes from this section.

Rinse Section:

This section consists of series of chambers. Its function is to remove acid

droplets from sheet by spraying of water.

First there is a rinse conc. tank. In which water is sprayed by set of two

nozzles.

Water is provided from scrubber section; water is pumped by pump and

transferred to tank. Again here it runs a cycle as its condition become dead it

is delivered to ARP.

After this the 5 rinse tanks. Each there is a set of nozzle and set of squeeze

rolls at start and end of each section. Fresh water is provided to tank 5 its

overflow goes to 4 and then 3, 2, 1. 2, 1 has same acidic nature or it may go

to ARP.

At end of set 5 there are two squeeze rolls then there is an edge knife blower

which removes water from edges of sheet then it comes in hot dryer.


ASSIGNMENT # 5

EXIT BUTTONS DESCRIPTION:

(NOTE; * shows button)

1. MAIN HYDRAULIC PUMP:

*Main hydraulic pump is first on because all hydraulic system is activated through

this button.

2. FEED MODE BUTTON:

*Feed mode button is pressed when sheet has passed through the center guide

assembly.

3. EDGE KNIFE BLOWER:

This is used to clear the remaining water on the edges of the sheets so that sheet

may not become rusty again. It has one button.

*Edge blower (on/off)

4. HOT AIR DRYER:

When the sheet comes out of the rinse tank it may be wet, to remove the water

spread on the sheet it is dried through air in hot air dryer. It has one button. *Hot

dryer (on/off)

5. CENTER GUIDE #1

When the sheet came out from hot dryer, it is used to place the sheet on center.

6. PINCH ROLLS:

They are used to hold the sheet and remove edge defects. Also have two buttons.

*Pinch rolls (up/down) *Pinch rolls (forward/reverse)


8. EDGE GUIDE PUMP:

To remain sheet on the center edge guide pump must be on so that recoiler can

move adjust the sheet. It has one button.

*Edge guide pump (on/off)

9. APRON TABLE:

Apron table is used to support the sheet when it is recoiled. Two buttons are

*placed for (up/down) and (lift/lower).

10. DB SUPPORT:

To support the recoiler mandrel

11. RECOILER LUBRICATION:

To provide lubrication during process:

12. RECOILER MANDREL:

It is that part where the coil is recoiled. It has two buttons on the panel, one for the

expansion of the mandrel and other for mandrel collapse.

13. LINE BUTTON:

It is activated when the sheet is fixed into the recoiler the end of threading. * Line

(on/off)

14. TENSION UNITS BUTTON:

To provide tension in the sheet when it is recoiled it must have passed through the

tension units. These units also flatten the sheet. There are two tension units at the

exit.

*Tension unit#1(up/down)

*Tension unit#2(up/down)


15. SHEAR CUTTER:

To cut the end of the sheet which is treated as scrap. One button named exit shear

mode safe has two options (manual/cut). For cut only there is one more button

named cut which we press it will cut the sheet. Cutter movement is in operator’s

control. For manual only there is one more button named entry shear (up/down)

which controls the movement of the shear cutter.

16. SCRAP SYSTEM TABLE:

It is used to place the table upward so that scraps which are cut through shear

cutter do not go forward on the line. *Scrap system table (up/down).

17. CENTER GUIDE #2:

When sheet is out of center then it is used to place the on center.

*Side guide (in/out)

19. PUSHER PLATE:

When sheet is completely recoiled it is used to remove the coil from the mandrel.

*Pusher plate (in/out)

20. COIL CAR PUMP:

This pump must be on so that coil car can move. It has one button

*Coil car pump (on/off)

21. COIL CAR:

Coil car is used to transfer coils from the recoiler to the saddle. It is hydraulically

operated. It has two buttons on the panel.

*Baby coil car (In/Out)

*Baby coil car (Lift/Lower)


ASSIGNMENT # 6 In pickling three is one main hydraulic pump which provides hydraulic power to

all hydraulic pipes. Following information is about main hydraulic pump.

GENERAL KNOWLEDGE:

Max working pressure 105 bar

Operating temperature min=40°c and max=55°c

Working fluid=mineral oil.

Power source ac 415v-50Hz and operate on 3 phase.

All pipes joint with tag welding only.

ABOUT:

There are two induction motors in main hydraulic pump.

One motor work and other motor for safety if some problem occur then we

use second motor to avoid down time.

In main hydraulic machine there is a filter which also has silica jell for

absorbing moisture.

Some times due to leakage and other factor the quantity of hydraulic oil will

be low then we add hydraulic oil in machine.

Hydro motors are more powerful then electric motors and in speed electric

motors more than hydraulic.

WORKING:

The main hydraulic pump provide power to all hydraulic cylinders for

moving many machines

There are two pipes in every machine which proceed by hydraulic one are in

let and other is out let.

In let for in the pressure of hydraulic oil and out let for return to the machine

USES:

Baby coil car moves due to hydraulic power.

Squeeze roll also move due to hydraulic.

UN coiler also moves due to hydraulic.


Re coiler also move due to hydraulic.

Peeler table also move due to hydraulic system

ASSIGNMENT # 7

TASK: The quality of sheet is not proper and acid is not complete wash away from

sheet, so inspect the nozzle.

BASIC KNOWLEDGE:

When sheet comes from acid tank the acid wash from sheet with water.

The water shower through nozzles.

There are one concentration tank and five cascade tanks.

In concentration tank there are 32 nozzles while in each cascade tank there

are 16 nozzles.

The water pass supply of concentration tank is separate while water supply

in 5 cascade tank and then its flow pass in fourth then 3rd till 1st cascade tank

INSPECTION AND MAINTAINANCE:

First main steam wall done off.

Then check the flow of water from nozzles also check the damage of nozzles

If flow of water is not properly then take out headers and set the direction of

nozzles.

If any nozzle break or have crack then change nozzle.

The important thing is when you fit the nozzle you should not fit it much

tight it chance to break or crack.

The error comes in nozzles generally when sheet strike with nozzle.


ASSIGNMENT # 8

Manometer:

DEFINATION:

Pressure measuring devices using liquid columns in vertical or inclined

tubes are called manometers.

A manometer is referred to a pressure measuring instrument, usually limited

to measuring pressures near to atmospheric. The term manometer is often

used to refer specifically to liquid column hydrostatic instruments.

PRINCIPLE:

The level of the liquid being determined by the fluid pressure and the height

of the liquid being indicated on a scale.

Pressure is exerted on one end of a U-shaped tube partially filled with liquid;

the liquid is displaced upwards on the other side of the tube by a distance

proportional to the pressure difference on each side of the tube.

Manometers are cheap, simple, and reliable. They are widely used,

particularly in undergraduate fluid mechanical laboratories.

The most serious drawback of a manometer, is that is has a very poor

temporal response. A manometer can not pick up rapid changes in pressure.

As a result, they are best suited to applications where steady-state pressure is

being measured.

http://en.wikipedia.org/wiki/Pressure

http://en.wikipedia.org/wiki/Measuring_instrument


4 HI COLD ROLLING MILL:

ROLLING:

Rolling is a metal forming process in which material is deformed plastically by

passing through a pair of rolls. Rolling is the most widely used forming process,

which provides high production and close control of final product. The metal is

subjected to high compressive stresses as a result of the friction between the rolls

and the metal surface. Rolling is classified according to the temperature of the

metal rolled. If the temperature of the metal is above its recrystallization

temperature, then the process is termed as hot rolling. If the temperature of the

metal is below its recrystallization temperature, the process is termed as cold

rolling.

Rolling

Cold rolling Hot rolling

The initial breakdown of ingots into blooms and billets is generally done by hot-

rolling. Irregularities and impurities are homogenized. Improvement of properties

in the direction of rolling so hot roll properties is better than cast components. It is

economical for mass production etc. however oxide formation, scaling,

decarburization, and poor surface finish are some of the limitations in hot rolling.

COLD ROLLING:

Cold rolling occurs with the metal below its recrystallization temperature (usually

at room temperature), which increases the strength via strain hardening. It also

improves the surface finish. The cold-rolling of metals has played a major role in

industry by providing sheet, strip, and foil with good surface finishes and increased

mechanical strength with close control of product dimensions. Commonly cold-

http://en.wikipedia.org/wiki/Metal_forming

http://en.wikipedia.org/wiki/Recrystallization_%28metallurgy%29

http://en.wikipedia.org/wiki/Strength_of_materials

http://en.wikipedia.org/wiki/Strain_hardening

http://en.wikipedia.org/wiki/Surface_finish


rolled products include sheets, strips, bars, and rods; these products are usually

smaller than the same products that are hot rolled. Because of the smaller size of

the work pieces and their greater strength, as compared to hot rolled stock, four-

high or cluster mills are used. Cold rolling cannot reduce the thickness of a work

piece as much as hot rolling in a single pass.

REDUCTION IN COLD ROLLING:

The total reduction achieved by cold-rolling generally will vary from about 50 to

90%. The reduction in each stand should be distributed uniformly without falling

much below the maximum reduction for each pass. Generally the lowest

percentage reduction is taken place in the last pass to permit better control of

flatness, gage, and surface finish. Cold-rolled sheets and strips come in various

conditions: full-hard, half-hard, quarter-hard, and skin-rolled. Full-hard rolling

reduces the thickness by 50%, while the others involve less of a reduction.

Cold rolling mills reduce hot rolled coils to lighter thicknesses; establish uniform

hardness, accurate dimensional tolerances and the required surface finish

PROCESS:

Cold rolling is performed by unwinding the hot roll coil and passing the strip

through pairs of horizontal rolls or mill "stands". Coils are received from pickling

and placed in the stock area, then transferred to POR (Pay off Reel) mandrel. The

process from feeding coils at the POR mandrel and till the sheet is given few wraps

at the recoiler is called threading.

Reduction is not carried out completely in a single pass; however in each pass

reduction occurs to a certain limit. A reduction of max 38% is possible in first pass

then reduction rate decreases in upcoming passes. The number of passes depend on

the thickness of HR sheet, higher the thickness; greater will be the number of

passes required.


EMULSION:

Emulsion, which is a mixture of soluble oil and water, is used as a roll coolant,

lubricant and cleaner. Its composition is 2-4% oil and remaining is water.

Emulsions contain both a dispersed and a continuous phase; the boundary between

these phases is called the interface. Emulsions tend to have a cloudy appearance

because the many phase interfaces scatter light as it passes through the emulsion.

Emulsions appear white when all light is scattered equally. Used emulsion goes to

emulsion tank, where it is cleaned. Emulsion tank has two parts; dirty section and

clean section. Used emulsion is filtered, cleaned and then came back to mill again.

Temperature of emulsion is about 50°c. Temperature at rolling mill is about 200°c

due to friction and plastic deformation. Therefore, we use emulsion of 50°c to

avoid chilling of sheet. Two pumps are used for roll bite and roll coolant. Roll bite

is contact area between work rolls and roll coolant is area between work rolls and

backup rolls.

The water used in emulsion is demineralized water. The minerals present in water

are normally calcium, magnesium, sodium, alkalinity, chlorides, sulfates, nitrates,

and silica can harm pipes, assemblies etc by causing corrosion, scale building,

spotting etc.

http://en.wikipedia.org/wiki/Phase_boundary

http://en.wikipedia.org/wiki/Scattering

http://en.wikipedia.org/wiki/White


HRC (mm) Min gauge (mm) % Reduction % Max Pass Red

1.6 0.15 90.6 38

1.8 0.18 90 36

1.9 0.20 89.5 32

2.0 0.20 90 32

2.3 0.25 89.1 25

2.5 0.3 88 23

2.8 0.45 83.9 20

3.0 0.60 80 18

3.1 0.60 80.6 18

3.2 0.85 73.44 16

3.3 1.0 69.7 15

3.4 1.1 67.65 15

3.5 1.25 64.29 14

4.0 1.6 65.22 12

(This table shows the Max % reduction of HR sheet)

ROLL PROFILE:

The profile consists of how the thickness of the workpiece varies across the width

of the workpiece and can be measured in units of length. Profile is made up of the

measurements of crown and wedge. Crown is the thickness in the center as

compared to the average thickness at the edges of the workpiece. Wedge is a

measure of the thickness at one edge as opposed to the other edge. Both may be

expressed as absolute measurements or as relative measurements. For instance, one

could have 2 mil of crown (the center of the workpiece is 2 mil thicker than the


edges), or one could have 2% crown (the center of the workpiece is 2% thicker

than the edges).

4 HI ROLLS:

4 Hi Rolling Mill consist of four rolls, two work rolls which perform reduction and

two backup rolls. Backup rolls are intended to provide rigid support required by the

working rolls to prevent bending under the rolling load. Rolling balance system is

use to ensure that the upper work and back up rolls are maintain in proper position

relative to lower rolls. AGC (Automatic Gap Control) controls the roll gap. In Roll

changing process a unit designed to attach to the neck of the roll to be removed

from or inserted into the mill.

THICKNESS MEASUREMENT:

Thickness is measured by x-ray gauges and reading is provided to computer. Initial

and final thicknesses at the entry and exit of each pass are fed in computer.

Thickness at exit of first pass became the entry thickness of second pass, similarly

for each pass. A graph continuously shows the variation in thickness at entry and

exit. This thickness variation gives feedback to AGC which controls the roll gap.

The arc of the contact is circular and the coefficient of friction is constant at all

points on the arc of contact. The elastic deformation of the sheet is negligible in

comparison with the plastic deformation.

SHAPE OF HR SHEET:

This is the actual shape of HR sheet. Its thickness is greater at the center but

smaller at the edges (thickness varies in microns). During hot rolling it is not

possible to completely make the sheet flat because stirring is not achieved for

completely flat sheet. Therefore its shape is like this. During cold rolling, as the


sheet is worked below recrystallization temperature, profile of work rolls and

backup rolls is needed to be concerned.

Completely flat rolls cannot be used because they apply greater force at the center

but a b lower force at the edges. As a result waviness appears on the sheet because

due to tension sheet deforms in longitudinal direction. Width remains the same but

increase in length form waves like appearance on the sheet. Phenomenon of roll

flattening occurs, which increases the roll pressure and cause the rolls to deform

more easily then the sheet. Sheet shifting, sheet breakage etc can be occurred.

ROLL GAP:

The roll gap must be perfectly parallel to produce sheets/plates with equal

thickness at both ends. The rolling speed is very sensitive to flatness. Maintaining a

uniform gap between the rolls is difficult because the rolls deflect under the load

required to deform the work piece. The deflection causes the work piece to be

thinner on the edges and thicker in the middle. This can be overcome by using a

crowned roller (parabolic crown)

CONTINUOUSLY VARIABLE CROWN (CVC):

Continuously variable crown (CVC) profile involves grinding a third order

polynomial curve into the work rolls and then shifting the work rolls laterally,

equally, and opposite to each other. The effect is that the rolls will have a gap

between them that is parabolic in shape, and will vary with lateral shift, thus

allowing for control of the crown of the rolls dynamically. The basic fundamental

of continuously variable crown (CVC) profile is to improve final product shape.

CVC profile also rename as a fish profile in which both roll shifting mechanisms

inside the mill can be made. In CVC profile we can shift a roll to maintain this

shape. Continuously variable crown (CVC) system is an effective method for

controlling strip flatness and profile. The key issue in the development of the CVC

system is the design of the roll profile, which is based on a cubic function. Not

only the desired variable crown can be obtained, but also the axial force acted on

the rolls can be minimized.


+C2

-

CVC

-C4 +C4

+

-

Bending

+ -C2

Positive bending

Maximum of 1000KN per roll or 500KN per neck positive bending can be applied.

Negative bending

Maximum of 700KN per roll or 350KN per neck negative bending can be applied


WORK ROLL BENDING:

Other methods of compensating for roll deformation include work roll bending.

Work roll bending involves using hydraulic cylinders at the ends of the rolls to

counteract roll deflection

Another way to overcome deflection issues is by decreasing the load on the rolls,

which can be done by applying a longitudinal force; this is essentially drawing.

Other method of decreasing roll deflection includes increasing the elastic modulus

of the roll material and adding back-up supports to the rolls. In order to produce

flat material, the material must be reduced by the same percentage across the

width. This is important because mass flow of the material must be preserved, and

the more a material is reduced, the more it is elongated. Skewing, a linear position

change of roll gape is done to remove the linear part of flatness error.

For Centre

For Edges

Defects:

Symmetrical edge wave

The edges on both sides of the work piece are "wavy" due to the material at the

edges being longer than the material in the center.

http://en.wikipedia.org/wiki/Drawing_%28manufacturing%29

http://en.wikipedia.org/wiki/Elastic_modulus


Asymmetrical edge wave

One edge is "wavy" due to the material at one side being longer than the other side.

Center buckle

The center of the strip is "wavy" due to the strip in the center being longer than the

strip at the edges.

ASSIGNMENTS:

Following assignments were given to us at the 4 hi rolling mill.

Assignment # 1

To find out the number of wraps in a coil:

GIVEN:

Internal dia of coil = 610mm

Outer dia of coil = 2500mm

Thickness = 2.0mm

No of wraps =?

SOLUTION:

NO OF WRAPS = (O.D-I.D)/2

= (2500-610)/2

= 945

NO OF WRAPS = 945/2

= 473 wraps


Assignment # 2

To find out the weight & length of coil:

GIVEN:

Density = 7860kg/m³

Thickness = 2.0mm

Inner dia = 610mm

Outer dia= 1950mm

Width = 1219mm

Weight=?

Length =?

SOLUTION:

Area = π/4(O.D²-I.D²)

Area = 2.694m²

Volume = Area x Width

Volume = 3.284m³

Density= Mass/Volume

Mass = Density x Volume

Mass = 25.8 tons

Length = Volume/ (width x thickness)

Length = 1348m


Assignment # 3

We were given assignment to calculate the thickness of two different samples of

sheet and generate a graph to observe the variation of thickness across the width of

sheet. We also learned the CVC profile calculation. Working of this assignment

has been attached.

Assignment # 4

In order to understand the microstructure of steel sheet during the complete

process of cold rolling, we were given task to perform the microscopy of different

samples of sheet.

These samples were following:

1) After SPM (0.828mm) 2) After 4hi (1.085mm)

3) After 4 hi2 (1.173mm) 4) Pickled HR (2.156mm)

5) HR (2.240mm) 6) After annealing (0.196mm)

Other than these samples, three more samples were provided. We went

to NED to perform microscopy. After performing microscopy, we

provide them the microstructure images etc.

REWINDING:

Coils are wound at high tension at 4 hi mill (6000kgf). The reason for

rewinding is that if coils are wind at high tension they may stick together

during annealing and annealing would not be achieved properly. At


rewinding shop their tension is released and winds at lower tension of

about 2150kgf. Therefore their tension is released at rewinding section.

TAPER TENSION:

In winding systems, decreasing the tension while the winder radius

increases is called taper tension, this can make the inner of the winder

tighten and the outer of the winder loosen, thus avoid slipping.

It is therefore necessary to analyze the relationship between taper

tension in winding section and internal stress distribution within center-

wound roll to prevent winding failure (starring, buckling, telescoping

etc).

We initially wind the coil at high tension at 610mm starting dia till

650mm, and then tension is decreased to certain % like 37% or 35% etc

till 690mm and then kept constant.

Sp.tension

3.5 2.5kgf/mm²

2.5

2.0

1.5

1.0

610 650 690 730 770 810

(Internal diameter; mm)


CALCULATIONS:

Absolute tension = Specific tension * thickness * width

Thickness =0.9mm

Width =1219mm

Specific tension =3.5kgf/mm²

Absolute tension = 0.9 X1219X3.5

=3839kgf/mm²

Decrease in tension = Absolute tension X 37%

=1420kgf/mm²

Final constant tension = 3839kgf/mm² - 1420kgf/mm²=2419kgf/mm²

COIL

Inner dia

610mm

650mm


REWINDING PROCESS:

Coil is first loaded from stock area and placed on the saddle then fed to uncoiler

mandrel. The process from feeding coil at the uncoiler mandrel and till the sheet is

given few wraps at the recoiler, is called threading. Centre is adjusted for the coil

and then threading is carried out. Coil`s face bending and shearing is made if

required. Recoiler mandrel is collapse and sheet is fixed in it and mandrel is

expanded. Sheet is given few wraps on uncoiler and then tension is provided

3800kgf initially to give a tighten core.

The tension is decreased to certain level and rest of the coil is wind at that constant

tension. CPC cameras are placed at the entry just after the apron table for

managing the centre position of the sheet. Threading is made manually than rest of

the line runs on auto process. Line speed should be control b/c wraps may become

out during rewinding which is not desirable. Wraps out may get bend during

annealing and thus increase the chance of scrap.

CORE OUT PROBLEM:

We also observed a problem about wrap out during rewinding. Wraps of coil

became out suddenly after half of the coil had winded. Rewinding machine was

running on center mode properly but not accurately on the auto mode. First CPC

cameras were checked, and replaced by new ones but still problem wasn`t solved.

Actual problem was with the gear box slider which was not functioning properly.

As the center of sheet became out it moves back but came forward slowly due to

friction. Gear box was lubricated and minimized the problem.

ANNEALING:

Annealing is a heat treatment process in which Controlled heating and controlled

cooling is carried out. It is a process that produces desire conditions by heating to

above the critical temperature, maintaining a suitable temperature, and then


cooling. Annealing is a heat treatment process in which is used to induce ductility,

soften material, relieve internal stresses, refine the structure by making it

homogeneous, and improve cold working properties.

DIFFUSION IN ANNEALING:

Diffusion phenomenon occurs in annealing. The movement of atoms has the effect

of redistributing and destroying the dislocations in metals. This alteration in

dislocations allows metals to deform more easily, so increases their ductility. On

heating at specific temperature and cooling it is possible to bring the atom at the

right lattice site and new grain growth can improve the mechanical properties

OBSERVATION & LEARNING:

Currently 3Cooling Bells and 2 Heating Bells are operating. Coil is first received

from rewinding to tilter, where its face is changed (from axial to longitudinal).

Then it is feed to stock area. A strip is tightened after two or three wraps so in

rewinding (so as to hold the core raps tight together). Before loading the base

check the base fan, sealing rubber. Clean the work base as it contains some

particles of emulsion, they may cause problems during annealing like make the

surface appear dull, and they may stick on the coils during flow of gas.

PARAMETERS FOR ANNEALING:

As coils are placed one above each other, their edges may get damaged or bend

hence increase the chance of scrap. In case if single coil is wrap out it must be

placed on the top. Generally four coils of width 1219mm each are placed one

above the other. A convector plate is placed in b/w each coil. Total height of the

furnace is 5300mm therefore total height of coils after placing must be below this.

Also 6 coils of 772mm with each or 5 coils of 910mm width each can be placed on

the base.

PARAMETERS FOR COIL PLACEMENT:

For good and proper annealing layers of coil should be wind proper so that weight

of coil must act uniformly on charge plate. It is generally in practice that all coils

placed in furnace must have same thickness, diameter, and width, no of passes etc.

If different dia coils are to be placed, the larger diameter coil must place first at the

http://en.wikipedia.org/wiki/Ductility

http://en.wikipedia.org/wiki/Cold_work

http://en.wikipedia.org/wiki/Dislocations


base then smaller dia coils above it respectively. All coils are not placed

collectively on the base first a convector plate is placed then the first coil is placed.

Before placing a coil a convector plate is places. The reason for placing convector

plate is to homogenize the uniform heat flow in inner cover from all direction of

coil. Fan blows the heat from bottom to top, heat came down from the inner dia of

coils. If all are to be placed collectively heat flow would not be uniform means

heat may not reach properly to middle wraps of coils.

Coils (5124mm)

Convector plates

(Base with same coils, width, dia, thickness etc)

(4815mm)

(Base with different coils, width, dia, thickness etc)

1219mm

1219mm

1219mm

910mm

1219mm

1219mm

1219mm

1219mm


CONVECTOR PLATES:

Two different thickness convector plates are used

For < 0.5mm 82mm thickness convector plate is used. For > 0.5mm 62mm

thickness convector plate is used. Convertor plate is placed by arm gripper.

ANNEALING PROCESS:

It takes about an hour to charge the base with capacity of 4 coils. After placing the

inner cover we perform a test to check out leakage if any in the cover after physical

inspection of cover we hold it for 18-20min by flowing N2. This is to remove

oxygen content from inner cover when there is no alarm during safety purge we

plug the heating bell then the heating start (nozzle of CH4+H2+N2 are placed

properly).

HEATING CYCLE:

Heating cycle continues about 19 hours. Initially there is a ramp heating.

Temperature is increased to certain limit i.e. 960°c.Since coils are wound in

tension heat can’t penetrate rapidly to middle portion and soaking is carried out, in

which temp is hold in furnace

Hot spot

Cold spot

(Coil cross section)

HOT & COLD SPOT:

Hot spot is heated during ramp heating but for cold spot t is difficult furnace is

hold down when temp is homogenized in complete coil heating bell is lifted and

placed on other base being charged.


BURNERS:

Total 8 burners are used ignited by natural gas and oxygen from blower air is

transferred to heat exchanger than to burners first pilot burner is start to start

ignition than all burner starts. One outer burner is than ignited by used hydrogen

going out. Inner cover is filled by hydrogen gas when burning starts in heating

bell, heat energy which is generated heats up the inner cover. Heat from inner

cover is conducted by hydrogen gas & transferred to coils in this way coils are

heated to softening point direct heat is not applied b/c it may melt the sheets or

may cause change in structure.

COOLING CYCLE:

As heating is completed heating bell is allowed to slow cool to a temp of 600°C.

Then heating bell is lifted & cooling bell is placed on the base two types of coiling

mechanism is used.

Air cooling & Water cooling:

Air cooling is carried out first. Temp is reduced to 380°c. For two hours it is

continue than water coiling starts from 380°c. A temperature is set i.e. 60°C but

time duration is not set.

It is a slow cooling process if we cool the inner cover rapidly certain problems may

be caused. Outer layers will cool more than the inner layers of coil. As the temp is

reached the cooling bell is lifted & placed on other base whose heating is complete

or about to complete. Coils are discharged from the base. First inner cover is

removed by the help of arm gripper the coil is removed. Convector plate is

removed than coil is removed respectively. It takes about 1 hour to discharge base

coils are placed in stock area then transferred to tilter than to skin pass mill.


SKIN PASS ROLLING:

Skin pass rolling also called Temper rolling, is a finishing operation in the

production of thin strips of steel and nonferrous metals. It consists of cold rolling

with very low reduction of area (not more than 3 percent). As a rule, the metal is

subjected to temper rolling after heat treatment. Temper rolling increases the yield

point reducing the possibility of formation of flow lines, which mark the surface of

products, on the metal during cold stamping

OBJECTIVE OF SKIN PASS:

The main objectives of the skin-pass are to modify the mechanical features of the

strip steel and provide the surface finish required by the client. This improves the

range and quality of the manufactured product whereby the required roughness, the

sheet is given well defined mechanical, technological and geometrical properties

(yield stress, roughness, and flatness) by the final cold forming process in the skin

pass mill. Temper rolling is necessary for sheet metal that is to undergo cold

forging with deep drawing, such as sheet steel intended for making motor-vehicle

body parts and sheet iron. Depending on the purpose of the sheet metal, its surface

is worked to various degrees during temper rolling, and it is partially aligned in the

process. Temper rolling is done in skin-pass mills, usually in one stroke, and less

frequently in several strokes. This involves a controlled light reduction to establish

the final thickness, impart the desired surface finish, flatten the strip to improve

shape and create the required hardness of the material.

SKIN PASS MILL:

After annealing, the steel has been so thoroughly relieved of internal stresses that it

has a tendency not to bend uniformly, resulting in localized strains during

subsequent forming operations. To counter this, a light reduction, between ½ to 3

percent of the thickness, is taken at the Skin Pass Mill/ Temper Mill. Temper Mill

is made up of a ‘4-Hi’ rolling mill stands. This arrangement gives operators the

flexibility to improve the flatness of the product and to allow a ‘matte’ surface

finish to be applied by the shot-blasted work-rolls while meeting the targeted

reduction, or ‘extension’. Work rolls are changed each day or so, after which the

scheduled coils are processed.


SKIN PASS PROCESS:

Power is delivered from the mill motors to the backup rolls, which turn the work

rolls, which in turn roll the steel. The reductions are much smaller, so less tension

is held between stands and the roll coolant / emulsion is normally used. Operators

at the temper mill are relied upon to make most adjustments based on the rolling

parameters and product appearance.

Oil can be applied either ‘light’ or ‘heavy’ by coating the top surface of the coil as

it is wound onto the tension reel. If necessary to make the customer’s coil weight

requirements, coils can be split with a shear at the exit of the last stand. At the exit

side of the mill, an X-ray thickness measurement device uses to record the gauge

of the steel. Both the entry and exit ends consist of rubber-coated wheels that are

turned by the strip; each revolution is counted and translated into a length

measurement.

PREPARATION AND THREADING:

Coils are first transferred from annealing to skin pass mill. First coils are placed on

a tilter than transferred to SKM stock area. Then coil is placed on uncoiler

mandrel. Large electro-mechanical screws allow for adjustment of the gap between

work rolls. An operator monitors the threading of the sheet. After the head-end is

under wound onto the tension reel, and tension has been established through the

mills, the operator makes further adjustments to the roll gaps, tension settings, and

work-roll bending (up to 110 tons).

Initially, steel is slowly rolled while final adjustments are made; when the operator

is satisfied, the mills accelerate to their run speed - up to 300 meters per minute at

which further adjustments are not normally made. The low-volume lubrication

system applies the lubricant in the skin-pass stand entry. This reduces the friction

in the roll gap and hence the roll force, and improves flatness while using a

minimum amount of lubricant.

TAIL-OUT AND INSPECTION:

When the coil has paid off down to the last few wraps, it is sheared and the inner-

most, off-gauge wraps are removed from the mandrel with the help of coil car and

scrapped. At the exit end, the finished coil is manually banded by an operator with

a single, circumferential, strip. A short sample is sheared from the tail of the coil at


the exit end and examined to assess the quality of the coil’s surface, confirm the

dimensions, and evaluate the hardness and thickness. Where indicated on the

schedule, the surface texture of the sample is evaluated to ensure the customer will

be able to paint, or otherwise process, the steel efficiently.

DISCHARGING:

The metallurgical properties of the steel are evaluated by examining the Rockwell

Hardness of the steel. It improves the range and quality of the manufactured

product whereby the required roughness, surface quality, and metallurgic product

modifications are obtained to attain excellent homogenization of the crystalline

grain and the final surface shine. Coils are packed at the packing plant to protect

the steel: high-quality paper is wrapped around the coil and protectors placed on

the corners reduce transportation damage.

ROLL GRINDING:

In grinding shop, grinding of rolls for 4hi mill and skin pass mill is carried out. The

purpose of grinding is to eliminate the roll defects like cracks, fire cracks, sheet

sticking etc.

ROLL GRINDING PARAMETERS:

Each roll has to be ground after certain duration of running. Work roll for 4 hi mill

has to be grind after running of 200Km circumferential distance. Backup roll for 4

hi mill has to be grind after running of 3000km circumferential distance. Rolls are

detached from the mill by roll changing machine, and then transferred to roll

grinding shop by crane and placed on the saddle. Initially they are in hot condition;

therefore, they are cooled for about 24 hours at room temperature.

PROCESS:

Roll is cleaned first by cleaner so that the surface may clean of emulsion, grease

etc. Grinding of work roll requires approximate one hour and for backup roll, about

twelve hours minimum requires.


As the roll is placed on the steady of grinding machine, its alignment has to be

adjusted manually by gears. Initially surface of the rolls has to be observed i.e.

either it has visible cracks, sheet sticking etc or not. If surface does not have visible

cracks, a predefined program runs on grinding machine`s computer to perform

grinding. About twenty microns (200µm) is grind for this condition. Sometimes

rolls may have visible cracks or sheet stick to it. Their grinding process is a bit

different from normal grinding of roll. They are grind to about fifty microns

(500µm).

Before starting the grinding, position of roll is set according to parameters.

Emulsion flow is checked, condition of grinding wheel is inspected. Silicon

carbide grinding wheel is used for grinding. Dia of grinding wheel is 710mm.

NON DESTRUCTIVE TESTING (NDT):

In non destructive testing, the sample under test is not destroyed. A penetrant is

sprayed on the barrel of roll. It penetrates into the crack surface. Again the surface

is cleaned, a developer is sprayed and if there are cracks, they become visible.

Then with respect to the depth of the crack, roll is grind again to eliminate the

crack.

CONCLUSION:

My internship duration at ISL was superb, I had learned a lot regarding all the

processes. All personals; HODs`, managers, operators etc were very cooperative.

Furthermore I want to say that there are a few things need to be looked out. There

was not any proper planning of HR department regarding internees. We were

divided in groups for ten days of each department, but plan wasn’t followed, we

were at CRM for about a month.

ISL provides a very good environment for learning process like Cold rolling,

galvanizing etc. Hope that it will progress more in upcoming future and keep on

providing such type of learning sessions to us.

Documents

Internship Report-ISL-2012 Yaseen Raza