SAIL Bhilai Steel Plant 5 Roll Assembly Project Report

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STEELAUTHORITY OF INDIA LIMITED
~~~
BHILAI STEEL PLANT
Preparation of 5 Roll Assembly
Sets of CCS in MARS-2
&
26.05.14 - 21.06.14
Under the Guidance of
Arindum Halder
Roll No: - P 14/2214
Aritra Chatterjee
Roll No: - P 14/2216
Subham Shit
Roll No: - P 14/2215
Mr. Gitesh Dewangan
Department of Mechanical Engineering
INDIAN INSTITUTE OF ENGINEERING SCIENCE AND TECHNOLOGY, SHIBPUR
Assistant Manager, MARS-2, BSP
By
Project on :
STEEL AUTHORITY OF INDIA LIMITED
(FORMERLY BENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR)
BHILAI STEEL PLANT

Acknowledgement
We would sincerely like to thank the Human Resource Department, of Bhilai Steel Plant,
SAIL for their constant assistance to help us achieve this project work successfully. Our
sincere regards to Mr. S.K. Marathe for helping us realise the do’s and don’ts pertaining to
this specific project report and also helping us in all other sort of ways throughout the entire
duration of our project work. We would like to thank Mr. Gitesh Dewangan , Assistant
Manager of MARS-2, BSP who opted to become our project guide and it was owing to
him only that our project has become a piece of tangible reality from just a dream. It is only
owing to his sincere help, guidance and hours of teaching and learning we gained from him
that we have finally been able to jot down this project report. We are sincerely indebted to
him, for the large chunks of time he spent every now and then to answer all of our doubts
and questions and scrutinise our reports, pointing our mistakes and guiding us to the correct
path. We would also like to pay our sincere gratitude to Mr. M.L. Soni, the person who
was referred to, by none other than our own project guide, Mr. Dewangan, for further
clarifying our doubts, with his year long experience and it was only owing to him that we
came to know how the practical field work is done in the industry, how various
machines are operated, the technique for dismantling, operation and measurements, which
one cannot find in any sort of books or in internet. Last, but not the least, we would like to
thank and send our sincere regards to Mr. Samiran Sikdar, who has remained one of the
key figures behind this project report. It was only owing to him that we obtained the lion’s
share of the information which we used for this very project report. We are extremely
thankful to him for all the minute details he provided us regarding our project and it was
only due to him that we could obtain the basic idea required to understand our project topic.
It can truly be stated that without his help, our report and ideas would have been incomplete.
Lastly, we would like to thank all other various persons and workers of BSP, who have
helped us in one way or another during this month-long project based training of ours.

Contents
 INTRODUCTION
 Introduction to Bhilai Steel Plant I – II
1. CHAPTER 1: A REPORT ON MARS-2
1.1 Introduction to MARS-2 1
1.2 Annual production in MARS-2 5
1.3 Cost control of MARS-2 during 2013-14 6
2. CHAPTER 2 : AN OVERVIEW OF CONTINUOUS CASTING
2.1 Introduction 9
2.2 Components involved in the Continuous Casting Process 10
2.3 General Overview of Continuous Casting Machines 14
2.4 Development And Principal Types of Casting Machines 15
2.5 Processes Involved in Continuous Casting 16
2.6 Causes of Defects in The Cast Product And Prevention 20
3. CHAPTER 3: A BRIEF DISCUSSION ON FIVE ROLL SET
3.1 Introduction & General Overview 22
3.2 Location of Five Roll Set 23
3.3 Different Parts Present in a Five Roll Assembly 24
4. CHAPTER 4: PREPARATION OF 5 ROLL SET
4.1 Introduction 42
4.2 Description of the Process 42
4.3 Various Instruments Used in the Reassembling Process 47
5. CHAPTER 5: FAILURES IN 5 ROLL SET AND MEASURES FOR
VVVVVVVX.PREVENTION
5.1 Introduction 50
5.2 Failures in Bearings : Causes and Cures 50
5.3 Failures in Rollers : Causes and Cures 54
 CONCLUSION 56
 REFERENCE 57

I
An Introduction to Bhilai Steel Plant
Bhilai Steel Plant - a symbol of Indo-Soviet techno-economic collaboration, is one of the first
three integrated steel plants set up by Government of India to build up a sound base for the
industrial growth of the country, The agreement for setting up the plant with a capacity of 1
MT of Ingot steel was signed between the Government of erstwhile U.S.S.R. and India on 2nd
February, 1955, and only after a short period of 4 years, India entered the main stream of the
steel producers with the commissioning of its first Blast Furnace on 4th
February, 1959 by the
then President of India, Dr Rajendra Prasad. Commissioning of all the units of 1 MT stage was
completed in 1961. A dream came true-the massive rocks from the virgin terrains of Rajhara
were converted into valuable iron & steel.
In the initial phase the plant had to face many teething problems, mostly unknown to the
workforce at the time. But by meticulous efforts and teamsprit, these problems were
surmounted and the rated capacity production was achieved only within a year of integrated
operation of the plant.
Thereafter, the plant was expanded to 2.5 MT capacity per year, and then to 4 MT of crude
steel per year, with Soviet assistance.
BSP is the sole manufacturer of rails and producer of the widest and heaviest plates in India.
Bhilai specializes in the high strength UTS 90 rails, high tensile and boiler quality plates, TMT
bars, and electrode quality wire rods. It is a major exporter of steel products with over 70% of
total exports from the Steel Authority of India Limited being from Bhilai. The distinction of
being the first integrated steel plant with all major production units and marketable products
covered under ISO 9002 Quality Certification belongs to BSP. This includes manufacture of
blast furnace coke and coal chemicals, production of hot metal and pig iron, steel making
through twin hearth and basic oxygen processes, manufacture of steel slabs and blooms by
continuous casting, and production of hot rolled steel blooms, billets and rails, structural,
plates, steel sections and wire rods. The plant's Quality Assurance System has subsequently
been awarded ISO 9001:2000.
Not content with the Quality Assurance system for production processes, Bhilai has one in for
ISO 14001 certification for its Environment Management System and its Dalli Mines. Besides
environment-friendly technology like Coal Dust Injection System in the Blast Furnaces, de-
dusting units and electrostatic precipitators in other units, BSP has continued a vigorous
afforestation drive, planting trees each year averaging an impressive 1000 trees per day in the
steel township and mines.
A leader in terms of profitability, productivity and energy conservation, BSP has maintained
growth despite recent difficult market conditions. Bhilai is the only steel plant to have been
awarded the Prime Minister's Trophy for the best integrated steel plant in the country seven
times.
Bhilai Steel Plant, today, is a panorama of sky-scraping chimneys and blazing furnaces as a
modern integrated steel plant, working round the clock, to produce steel for the nation. Bhilai
has its own captive mines spread over 10929.80 acres. We get our iron ore from Rajhara group
of mines, 85 kms south-west of Bhilai. Limestone requirements are met by Nandini mines, 20
kms north of Bhilai and dolomite comes from Hirri in Bilaspur district, 135 kms east of the
plant. To meet the future requirement of iron ore, another mining site Rowghat , situated about
100 km south of Rajhara, is being developed; as the ore reserves at Rajhara are depleting.

II
Bhilai expanded its production capacity in two phases - first to 2.5 MT which was completed
on Sept. 1, 1967 and then on to 4 MT which was completed in the year 1988. The plant now
consists of ten coke oven batteries. Six of them are 4.4 metres tall. The 7 metre tall fully
automated Batteries No 9 & 10 are among the most modern in India. Of Bhilai's seven blast
furnaces, three are of 1033 cu. metre capacity each, three of 1719 cu. metre and one is 2000
cu. metre capacity. Most of them have been modernized incorporating state-of-the-art
technology.
Steel is made through twin hearth furnaces in Steel Melting Shop I as well as through LD
Convertor -continuous Casting route in SMS II. Steel grades conforming to various national
and international specifications are produced in both the melting shops. Production of cleaner
steel is ensured by flame enrichment and oxygen blowing in SMS I while secondary refining
in Vaccum
Arc Degassing ensures homogenous steel chemistry in SMS II. Also in SMS II is a 130 T
capacity RH (Ruhshati Heraus) Degassing Unit, installed mainly to remove hydrogen from rail
steel and Ladle Furnace to meet present and future requirements of quality steel. Bhilai is
capable of providing the cleanest and finest grades of steel.
The rolling mill complex consists of the Blooming & Billet Mill, Rail & Structural Mill,
Merchant Mill, Wire Rod Mill and also a most modern Plate Mill. While input to the BBM and
subsequently to Merchant Mill and Wire Rod Mill comes from the Twin Hearth Furnaces, the
Rail & Structural Mill and Plate mill roll long and flat products respectively from continuously
cast blooms and slabs only. The total length of rails rolled at Bhilai so far would circumvent
the globe more than 4.5 times.
To back this up, there is Ore Handling Plant, three Sintering Plants – of which one is most
modern, two captive Power Plants with a generating capacity of 110 MW, two Oxygen Plants,
Engineering Shops, Machine Shops and a host of other supporting agencies giving Bhilai a lot
of self-sufficiency in fulfilling the rigorous demands of an integrated steel plant. Power Plant
No.2 of 74 MW capacity has been divested to a 50:50 SAIL/NTPC joint venture company. The
plant has undertaken massive modernization and expansion plan to produce 7.5 MT of hot
metal by the year 2010.
More than the machinery and processes, it is the men i.e. the engineers, technicians, skilled and
unskilled workers behind them that constitute the flesh and blood of this steel plant.
Bhilai at present has around 34000 persons to run this pulsating giant. The culture which has
today become the hallmark of Bhilai is a result oriented approach to work. It is their effective
and co-operative working relationship nurtured in a spirit of dedication and enthusiasm that
has shaped Bhilai's image today.
Adjoining the plant, a modern township - Bhilai Nagar, having the spaciousness of a village
and the cleanliness of a modern town is spread – over in 17 self-sufficient sectors with schools,
markets, parks and other facilities. Free Medical aid is given to all the employees and their
dependents through a network of health centers, dispensaries and hospitals. Medical facilities
are extended to retired employees & their spouses also. The Education Department runs a
number of higher secondary, middle, primary, and pre-primary schools in Bhilai and also in
the mines townships at Rajhara, Nandini and Hirri.
Thus together with all this facilities the Bhilai Steel Plant has not only become the leading steel
plant in the country but also has set a standard so high that other industries strive to achieve.

A REPORT ON MARS-2
Introduction, Annual Production & Cost Control of
Machining, Assembly & Re-Engineering Services-2
Chapter 1

Page | 1
MARS-2
1.1 INTRODUCTION TO MARS-2
• MARS-2 is popularly known as Machine Shop-2. MARS-2 stands for Machining,
Assembly & Re-Engineering Services-2. MARS-2 was established during 4 MT
expansion project to take care of machining & assembly jobs of Convertor,
Continuous Casting Shop & Plate Mill. The shop has got two machining bays
(Light bay and Heavy & Medium bay 78 x 24 M each), and one Assembly bay (72
x 24 M) which forms a Tee with the machining bays.
 Working Area of the shop : 5161m2
 Electrical Power : 1 MVA
• Past & Present:
MARS-2 started with manpower of 128. The present strength is only 86. Initially
MARS-2 was dedicated for 4 MT expansion area but presently it is dealing with
almost all the major shops of BSP.
• Specialization:
MARS-2 has two MACHINE BAY
1. LIGHT BAY- for Light Machining
2. HEAVY BAY- for Heavy Machining
MARS-2 has one ASSEMBLY BAY for assembly work.
• Capacity :
Annual machining capacity: 2200 T
Annual assembly capacity: 6000 T
Main assemblies done are 5-roll set, 8-roll set, 10-roll set, and Pinch rolls used in
Slab Caster of Continuous Casting Shop.
• Machining Jobs:
Following important high value items are machined:
1. Slide Block of Plate Mill
2. Inserts for Continuous Casting Shop
3. Hammer Plates of Sintering Plant-2 & 3
4. Top Tie Rod of Coke-oven
5. New Wheels of Various Departments.

Page | 2
• Repairing & Reclamation Jobs:
Following items are repaired & reclaimed:
1. Pinch Roll of Slab & Bloom Caster
2. Truing of Dia. 230 Roller of Continuous Casting Shop
3. Roll Table Cylindrical Roller Of Plate Mill
4. Reclamation of Various Wheels
5. Partening of Magnet of Continuous Casting Shop & Plate Mill
6. Reclamation of Ribbed Roller of Plate Mill
• Assembly Jobs:
Following important items are dismantled & reassembled in MARS-2
1. 5 ROLL SET OF CONTINUOUS CASTING SHOP
2. 10 ROLL SET OF CONTINUOUS CASTING SHOP

Page | 3
3. TONG ASSEMBLY OF CONTINUOUS CASTING SHOP
4. BREAST ROLL ASSEMBLY OF PLATE MILL
5. MUDGUN BARREL ASSEMBLY OF BLAST FURNACE

Page | 4
6. MUDGUN COLUMN ASSEMBLY OF BLAST FURNACE
7. DEDUSTING FAN OF SINTERING PLANT-3
• MARS-2 Assembly Jobs:
Following important items are dismantled & reassembled:
 Input/ Output Shaft Assembly
 Wheel Assembly
 Eccentric Shaft Assembly
 Reducer Assembly etc.
• Main Equipment(s):
MARS-2 is one of the most well equipped machine shop in BSP. It boasts of series of
highly useful machines like- Vertical Boring machine (1 No), Horizontal Boring
Machine (1 No), HMT Lathe (8 Nos.). MARS-2 also consists of 1 Cylindrical
Grinding Machine, 1 Heavy Duty Lathe, 1 Plano Milling Machine, 1 HMT Horizontal
Milling Machine, 1 HMT Universal Milling Machine etc. Beside these, it has 2
Slotting Machine, 1 Shaping Machine, 1 Thread Cutting Machine, and 1 Auto Welding
Machine of 10 T too.
 MARS-2 Crane Details:
MARS-2 has 3 overhead cranes each in Heavy, Light & Assembly Bay:
 Assembly Bay Crane- 50 / 20 T Capacity
 Heavy Bay Crane- 20 / 10 T Capacity
 Light Bay Crane- 20 / 10 T Capacity

Page | 5
1.2 ANNUAL PRODUCTION IN MARS-2
 Manufacturing of High Value Items :
S.N. Name of Items Qty. Total Value (Rs.)
1 Slide Block (Insert) of CCS 68 81,600
2 Slide Block (PMM- 548) for Plate Mill 18 2,61,000
3 Slide Block of Plate Mill Main Stand 27 54,00,000
4 Hammer Plates of SP – 3 1176 19,20,408
5 Machining of New Wheels 46 9,27,406
6 Tie Rod Size M48X16 Mtr. of Coke Oven 22 3,85,000
Total Value (Rs.) 89,75,414
 Repair & Reclamation of High Value Items :
S.N. Name of Items Qty.
Total Value
(Rs.)
1 Vertical Roll of R & S Mill 27 10,12,500
2 Pinch Roll of CCS 156 2,24,07,216
3 Breast Roll of P/Mill 6 13,33,332
4 Motorized Tong Assembly Of CCS 3 9,00,000
5 Welding of Various Sizes Wheels 168 34,99,944
6 Hydraulic Mud Gun Assembly 4 20,00,000
7 Dia. 230 Roller of 8- Roll set 176 68,74,912
8
Reclamation of Dia. 450 Cylindrical Roller of Plate
Mill
16 32,00,000
9
Reclamation of Dia. 300 Roller of Plate Mill (Welding
& Machining)
6 20,66,670
10
Reclamation of Dia. 350 & 450 Ribbed Roller of Plate
Mill
18 72,00,000
Total Value (Rs.) 5,04,94,574

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 Important Assemblies for CCS Operation :
 5 Roll Set Assembly - 91 Sets
So, total no. of sets for CCS Operation = 138 Sets
1.3 COST CONTROL OF MARS-2 DURING 2013-14
 Saving in Bearings :
S.N.
Name of
Items
Bearing
Used
New
Bearing
Reclaimed
Bearing
Value
Per
Piece
Total
Saving
1
5 Roll Set
Bearing No.
6212
5460 1415 4045 419 16,94,855
2
8 Roll Set
Bearing No.
22220
384 42 342 3564 12,18,888
3
10 Roll Set
Bearing No.
22213
2800 773 2027 2000 40,54,000
 Steps taken to Save Bearings :
 By removing old bearing from the sets.
 By cleaning properly then checking.
 By assembling properly with sufficient grease.
 Cost Control in Maintenance :
S.N. Name Of Items Qty. Total Value (Rs.)
1
Saving Of Head Stock Of Lc-100 Lathe Machine
By Sleeving Bearing Seating.
1 50,000
2
In-House Repair Of Lubrication Oil Pump Of L-
45 Lathe Machine
1 20,000
3
Repair Of Feed Mechanism Of Horizontal Boring
Machine
1 30,000

Page | 7
 Total Saving :
1. Saving in Manufacturing of High Value Items = 89,75,414
2. Saving in Repair & Reclamation of High Value Items = 5,04,94,574
3. Saving in Bearing = 69,67,743
4. Saving in Maintenance = 1,00,000
So, the Total Saving = 6,65,37,731.
 Saving In Power Consumption :
 Total Consumption of Electricity during 2013-14 -648500 KWH
 Total Consumption of Electricity during 2009-10 -750690 KWH
 Saving in Power consumption during last 4 year– 102190 KWH
 Steps Taken For Power Reduction :
 Over Hauling of Heavy Duty Motors & Generators.
 Switching off Machines, Fans, and ACs & Coolers etc. during idle time.
 Switching off of MG Sets.
 Saving In Oil Consumption :
 Total Oil Consumption during 2012-13 - 4430 Ltrs.
 Targeted reduction in Oil consumption for 2013-14 – 3390 Ltrs.
 Saving in oil consumption in current year - 1040 Ltrs.
 Steps Taken For Reducing Oil Consumption :
 By stopping leakages from Machines.
 By properly handling in Oil store room.
 By taking care at the time of pouring oil in machines.
• MARS-2 Certification:
MARS-2 has following important Certifications:
 OHSAS: 18001
 SA:8000
 ISO:14001

Page | 8
 Manpower Statistics in MARS-2:
• MARS-2 Awards & Rewards:
MARS-2 has got following awards:
 NATIONAL SAFETY AWARD for various categories.
 BEST HOUSEKEEPING AWARD.

2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13 2013-14
Executive 4 4 4 4 4 3 3 3 3
Non-Executive 107 106 102 101 99 91 88 86 82
0
20
40
60
80
100
120
Manpower
Years
Manpower over the Years
Non-Executive Executive

AN OVERVIEW OF
CONTINUOUS CASTING
Continuous Casting Process, Parts of CCM, Types,
Processes Involved & Casting Defects
Chapter 2

Page | 9
CONTINUOUS CASTING
2.1 INTRODUCTION
Continuous casting of steel is a process in which liquid steel is continuously solidified into a
strand of metal. Depending on the dimensions of the strand, these semi-finished products are
called slabs, blooms or billets. The process was invented in the 1950s in an attempt to increase
the productivity of steel production. Previously only ingot casting was available which still has
its benefits and advantages but does not always meet the productivity demands. Since then,
continuous casting has been developed further to improve on yield, quality and cost efficiency.
This process also known as ‘strand casting’ is used most frequently to cast steel (in terms of
tonnage cast). Aluminium and copper are also continuously cast. Sir Henry Bessemer, of
Bessemer converter fame, received a patent in 1857 for casting metal between two contra-
rotating rollers. The basic outline of this system has recently been implemented today in the
casting of steel strip.
Liquid steel is supplied to the continuous caster from the secondary steelmaking shop. The
ladle is usually delivered by crane and positioned into a ladle turret, which subsequently rotates
the ladle into the casting position. A slide gate in the bottom of the ladle is opened to allow the
liquid steel to flow via a protective shroud into a tundish, a vessel that acts as a buffer between
the ladle and the mould. As the tundish fills, stopper rods are raised in order to allow the casting
of steel into a set of water-cooled copper moulds below the tundish. Solidification begins at the
mould walls and the steel is withdrawn from the mould by a dummy bar. As it leaves the mould,
the strand of steel requires a sufficiently thick solid shell to carry the weight of the liquid steel
that it contains, i.e. the ferrostatic pressure.
Fig. 2.1: Continuous Casting Machine in action

Page | 10
Throughout the entire casting process, the mould oscillates vertically in order to separate the
solidified steel from the copper mould. This separation is further enhanced by introducing a
mould powder into the mould. The strand is withdrawn from the mould by a set of rolls which
guide the steel through an arc until the strand is horizontal. The rolls have to be positioned
close enough together to avoid bulging or breaking of the thin shell.
As the steel leaves the mould, it has only a thin solidified shell which needs further cooling to
complete the solidification process. This is achieved in the so-called secondary cooling zone,
in which a system of water sprays situated between the rolls are used to deliver a fine water
mist onto the steel surface. At this point, the steel, solidified shell and liquid center, is called
the strand. After the strand has been straightened and has fully solidified, it is torch-cut to pre-
determined product lengths. These are either discharged to a storage area or to the hot rolling
mill.
Continuous Casting has evolved from a batch process into a sophisticated continuous process.
This transformation has occurred through understanding principles of mechanical design, heat-
transfer, steel metallurgical properties and stress-strain relationships, to produce a product with
excellent shape and quality. In recent years, the process has been optimized through careful
integration of electro-mechanical sensors, computer-control, and production planning to
provide a highly-automated system designed for the new millennium.
2.2 COMPONENTS INVOLVED IN THE CONTINUOUS
XX.CASTING PROCESS
Components Primary Task Secondary Task
Ladle Transport and hold the liquid steel Facilitate inclusion removal
Ladle Turret
Position full ladles over the tundish
and remove empty ones.
Free the cranes for higher
productivity.
Tundish
Act as a buffer between the ladle
and the mould.
Facilitate inclusion removal
Mould
Cool down the liquid steel to form
a solidified shell
Rolling Strand
Further cool the strand to fully
solidified and straighten it
The above table provides a brief idea about the various components involved in the continuous
casting process and states their actions briefly. However a further detailed overview of the
various parts is given below:
 Ladle
Molten metal is tapped into the ladle from furnaces. After undergoing any ladle treatments,
such as alloying and degassing, and arriving at the correct temperature, the ladle is transported
to the top of the casting machine. Usually the ladle sits in a slot on a rotating turret at the casting

Page | 11
machine. One ladle is in the 'on-cast' position (feeding the casting machine) while the other is
made ready in the 'off-cast' position, and is switched to the casting position when the first ladle
is empty. From the ladle, the hot metal is transferred via a refractory shroud (pipe) to a holding
bath called a tundish.
 Ladle Turret
One very important part of a continuous casting plant is the ladle turret. It holds the pouring
ladles, which weigh up to 300 ton. By means of the ladle turret, the pouring ladles are
alternately slewed into pouring and charging position. This function ensures the uninterrupted
option of the continuous casting plant. While one ladle is being emptied a full ladle is provided
on the other side.
The bearings of the ladle turret, in spite of being subjected to high forces and considerable
tilting moments, have prolonged service life. The ladle turret serves for sequential casting.
 Tundish
From the ladle, the hot metal is transferred via a refractory shroud (pipe) to a holding bath
called a tundish. The tundish allows a reservoir of metal to feed the casting machine while
ladles are switched, thus acting as a buffer of hot metal, as well as smoothing out flow,
regulating metal feed to the moulds and cleaning the metal. The shape of the tundish is typically
rectangular, but delta and "T" shapes are also common. Nozzles are located along its bottom to
distribute liquid steel to the moulds. The tundish also serves several other key functions:
 Enhances oxide inclusion separation
 Provides a continuous flow of liquid steel to the mould during ladle exchanges
 Maintains a steady metal height above the nozzles to the moulds, thereby keeping steel flow
constant and hence casting speed constant as well (for an open-pouring metering system).
 Provides more stable stream patterns to the mould(s).
Fig. 2.2: Intermediate ladle of Continuous Casting Machine:
1 – Steel Jacket; 2 – Metering Nozzle; 3 – Metal Reservoir;
4 – Gunned Layer; 5 – Concrete

Page | 12
 Tundish Nozzle
Two basic types of tundish nozzles are used: (1) a metering or open nozzle and; (2) a stopper
rod-controlled nozzle. Metering nozzles, a simpler system, have been generally employed in
billet and small bloom casters, producing silicon-killed steels. Metal discharge rate is
controlled by the bore of the nozzle and the ferrostatic pressure (metal height in the tundish)
above the nozzle. Different bores are selected depending on the section size cast and casting
speed required. Stopper rod-controlled nozzles are used for casting slabs and large sections
when aluminum-killed steels are produced. In this application, metal discharge rate through the
nozzle is controlled manually or automatically by the setting of the stopper head in relation to
the nozzle opening. Originally, over-sized nozzles were used for casting aluminum-killed
steels: as alumina build-up occurred, the stopper head was raised to compensate for a reduction
in flow rate.
 Mould
The main function of the mould is to establish a solid shell sufficient in strength to contain its
liquid core upon entry into the secondary spray cooling zone. Key product elements are shape,
shell thickness, uniform shell temperature distribution, defect-free internal and surface quality
with minimal porosity, and few non-metallic inclusions.
The mould is basically an open-ended box structure, containing a water-cooled inner lining
fabricated from a high purity copper alloy. Mould water transfers heat from the solidifying
shell. Although the material of construction of the inner lining is usually a high purity
cold-rolled copper, copper with small amounts of silver is commonly used to obtain increased
elevated-temperature strength. The working surface of the liner is often plated with chromium
or nickel to provide a harder working surface and also to avoid copper pickup on the surface
of the cast strand.
There are two types of mould designs; tubular moulds and plate moulds. Tubular
moulds conventionally consist of a one-piece copper lining that usually has relatively thin walls
and is restricted to smaller billet and bloom casters. Plate moulds consist of a 4-piece copper
lining attached to steel plates. In some plate mould designs opposite pair of plates can be
adjusted in position to provide different section sizes. For example, slab width can be changed
by positioning the narrow-face plates, and the slab thickness changed by altering the size of the
narrow-face plates. The plate mould is inherently more adaptable than the fixed-configuration,
tubular mould. In addition to permitting size changes, changes can also be made to the mould
taper (to compensate for different shrinkage characteristics of different steel grades) as well as
ease of fabrication and reconditioning.
Mould heat transfer is both critical and complex. Mathematical and computer modeling are
typically utilized in developing a greater understanding of mould thermal conditions. Heat
transfer is generally considered as a series of thermal resistances as follows:
 Heat transfer through the solidifying shell
 Heat transfer from the steel shell surface to the copper mould outer surface
 Heat transfer through the copper mould
 Heat transfer from the copper mould inner surface to the mould cooling water

Page | 13
 Rolling Strand
In the mould, a thin shell of metal next to the mould walls solidifies before the middle section,
now called a strand, exits the base of the mould into a spray chamber. The bulk of metal within
the walls of the strand is still molten. The strand is immediately supported by closely spaced,
water-cooled rollers which support the walls of the strand against the ferrostatic pressure
(compare hydrostatic pressure) of the still-solidifying liquid within the strand. To increase the
rate of solidification, the strand is sprayed with large amounts of water as it passes through the
spray-chamber; this is the secondary cooling process. Final solidification of the strand may
take place after the strand has exited the spray-chamber.
It is here that the design of continuous casting machines may vary. This describes a 'curved
apron' casting machine; vertical configurations are also used. In a curved apron casting machine,
the strand exits the mould vertically (or on a near vertical curved path) and as it travels through
the spray-chamber, the rollers gradually curve the strand towards the horizontal. In a vertical
casting machine, the strand stays vertical as it passes through the spray-chamber. Moulds in a
curved apron casting machine can be straight or curved, depending on the basic design of the
machine. In a true horizontal casting machine, the mould axis is horizontal and the flow of steel
is horizontal from liquid to thin shell to solid (no bending). In this type of machine, either strand
or mould oscillation is used to prevent sticking in the mould.
After exiting the spray-chamber, the strand passes through straightening rolls (if cast on other
than a vertical machine) and withdrawal rolls. There may be a hot rolling stand after withdrawal
to take advantage of the metal's hot condition to pre-shape the final strand. Finally, the strand
is cut into predetermined lengths by mechanical shears or by travelling oxyacetylene torches,
is marked for identification, and is taken either to a stockpile or to the next forming process.
In many cases the strand may continue through additional rollers and other mechanisms which
may flatten, roll or extrude the metal into its final shape.
Fig. 2.3: Continuous Casting Mould with Ceramic Insert:
1 – Secondary Oxidation Protector; 2 – Ceramic Insert; 3 – Porous Ring;
4 – Ultrasonic Transducer; 5 – Copper part of the Mould

Page | 14
2.3 GENERAL OVERVIEW OF CONTINUOUS
XX.CASTING MACHINES
Casting machines can be classified into several main groups depending on the section shape
produced: billet, bloom, round, slab and beam blank. In some cases, overlaps occur where the
moulds on a particular machine can be changed to cast other shapes; for example, billets or
blooms, blooms or small slabs, and blooms or rounds. In addition, machines exist where special
shapes, such as rectangles and dogbone structural sections can be cast as well as billets or
blooms.
 Billet:
Billet machines, which cast section sizes up to approximately 5 inches square, are multi-strand
machines that are widely used in the mini-mill sector of the industry but only to a relatively
limited extent in fully integrated plants. This has occurred because of practical considerations
which are related to the heat size, casting rate per strand (tons/minute) and casting time. In
general, casting times are limited to approximately one hour for each heat because of heat
losses in the ladle. It is practical, for example, to cast a 50 net-ton heat on a 2-strand machine
or a 100 net-ton heat on a 4-strand machine. However, the number of strands required for
casting heat sizes in excess of 200 net tons, which are common in integrated steel plants,
becomes impractical.
 Bloom:
Bloom casters have been more widely installed by integrated plants because the casting rate
for the larger section size is higher than for billet sizes and, consequently, larger heat sizes can
be cast with relatively fewer strands. Bloom section sizes cast can vary, for example, from 7
in. sq., cast on a 6-strand machine from 150 net-ton heats, up to as large as 14.6 in. x 23.6 in.,
cast on a 3-strand machine from 180 net-ton heats.
 Round:
The installation of machines for casting rounds, principally for seamless tube production, has
been relatively slow. Although a 4-strand caster was installed, for example to produce 125 and
210-mm (4.9 and 8.3 in.) diameter rounds from a 30 metric-ton (33 net ton) heat in 1965,
potential surface cracking problems delayed the introduction of round casting. Some
modifications were made later for an existing 6-strand billet/bloom caster, for example, to
produce 152-mm (6-in.) diameter rounds in 1980s. The installations of the modified caster
included the 640,000 metric tons (700,000 net tons) per year U.S. Steel machine at Lorain,
which is a 6-strand caster producing up to 232-mm (9 and 1/4 in.) diameter rounds.
 Slab:
There are a large number of slab casters throughout the world which, although operated
principally in integrated steel plants, are also used for producing stainless and specialty steel.
These machines are generally high production units with rated annual capacities of up to 1.4

Page | 15
million metric tons (1.5 million net tons) and above. They are usually either single or
twin-strand machines casting large heat sizes. A wide variety of low carbon, low alloy, alloy
and stainless steel grades are cast for sheet, strip, plate and specialty applications. Successful
examples of the slab casters are the CSP technology developed by then SMS, and ISP from
then Mannesmann Demag, both in Germany. (The two companies have merged as
SMS Demag). Beam Blank and Special Shapes: Beam blanks are cast to be subsequently rolled
into I beams. Other special shapes are also cast to produce near-net shapes for various final
products. . The new technology has been developed to cast beam blank with thinner web, such
as 50 mm and less.
2.4 DEVELOPMENT AND PRINCIPAL TYPES OF
XX.CASTING MACHINES
One of the major objectives in the design of continuous casting machines has been to reduce
the capital cost of the installation while at the same time maintaining or improving the quality
of the cast product. This objective has been achieved by a progressive reduction in the height
of the machine which has resulted in a reduction in the size of the supporting structure, building
height and foundation. It has led to the development of five principal types of casting machines
which are essentially applicable to all section shapes cast whether billets, blooms, slabs, etc.
Chronologically, these types, illustrated schematically are:
1. Vertical machine with a straight mould and cutoff in the vertical position.
2. Vertical machine with a straight mould, single-point bending and straightening.
3. Vertical machine with a straight mould, progressive bending and straightening.
4. Bow type machine with curved mould and straightening.
5. Bow type machine with curved mould and progressive straightening.
Fig. 2.4: Various Section Shapes Produced in Continuous Casting

Page | 16
The choice between these types of casting machines depends on a complex optimization of the
specific facility requirements for caster productivity, product quality and machine complexity,
and cost. With the introduction of the newer designs there has been an increasing adoption of
the bow-type machines with curved moulds for slab casters and to a lesser extent for billet and
bloom machines. Curved machines are usually simpler to build (i.e., lower cost) and maintain
than vertical with bending machines, as the bender is eliminated. However, for some grades of
steel, for example, plate grades, quality and casting speed limitations were previously more
restrictive on these curved machines. Recently, technical developments such as "clean" steel
practices and electromagnetic stirring have been applied to curved machines to overcome these
restrictions. In general, the complexity of the casting process and machine varies greatly
between the type of product being cast (e.g., billet, bloom, or slab). This is due both to
the thermo-mechanical characteristics of these cast sections, and to the different applications
of the cast product.
Billet sections are self-supporting in
the secondary cooling zone, while
slabs are usually not. Generally,
billet casters have tended to be
simple in design, with open-pouring
streams, limited automatic controls,
and no roll support in the secondary
cooling zone. Conversely, slab
casters are complex and use the total
range of subsystems such as total
stream shrouding, computer controls,
and total roll containment
throughout the machine. Bloom
casters are intermediate between
these two extremes.
2.5 PROCESSES INVOLVED IN CONTINUOUS
XX.CASTING
To start a cast, the mould bottom is sealed by a steel dummy bar, which is held in place
hydraulically by the Straightener Withdrawal Units. This bar prevents liquid steel from flowing
out of the mould. The steel poured into the mould is partially solidified, producing a steel strand
with a solid outer shell and a liquid core. In this primary cooling area, once the steel shell has
a sufficient thickness, about 0.4 - 0.8 inches (10 to 20 mm), the Straightener Withdrawal Units
are started, and proceed to withdraw the partially solidified strand out of the mould along with
the dummy bar. Liquid steel continues to pour into the mould to replenish the withdrawn steel
at an equal rate. The withdrawal rate depends on the cross-section, grade and quality of steel
Fig. 2.5: Principal Types of Casting Machines

Page | 17
being produced, and may vary between 12 and 300 inches per minute. Casting time is typically
1.0 - 1.5 hours per heat to avoid excessive ladle heat losses.
Upon exiting the mould, the strand enters a roller containment section and secondary cooling
chamber in which the solidifying strand is sprayed with water, or a combination of water and
air (referred to as Air-Mist) to promote solidification. This area preserves cast shape integrity
and product quality. Larger cross-sections require extended roller containment (Figure 3). Once
the strand is fully solidified and has passed through the Straightener Withdrawal Units, the
dummy bar is disconnected, removed and stored. Following the straightener, the strand is cut
into individual pieces of the following as-cast products: slabs, blooms, billets, rounds, or beam
blanks, depending on machine design.
 Liquid Steel Transfer
There are two steps involved in transferring liquid steel from the ladle to the moulds. First, the
steel must be transferred (or teemed) from the ladle to the tundish. Next, the steel is transferred
from the tundish to the moulds. Tundish-to-mould steel flow regulation occurs through orifice
devices of various designs: slide gates, stopper rods, or metering nozzles, the latter controlled
by tundish steel level adjustment.
 Primary Cooling
Metal is drained from the tundish through another shroud into the top of an open-base copper
mould. The depth of the mould can range from 0.5 to 2 metres (20 to 79 in), depending on the
casting speed and section size. The mould is water-cooled to solidify the hot metal directly in
contact with it; this is the primary cooling process. A lubricant can also be added to the metal
in the mould to prevent sticking, and to trap any slag particles—including oxide particles or
scale—that may be present in the metal and bring them to the top of the pool to form a floating
layer of slag.
 Mould Oscillation
Mould oscillation is necessary to minimize friction and sticking of the solidifying shell, and
avoid shell tearing, and liquid steel breakouts, which can wreak havoc on equipment and
machine downtime due to clean up and repairs. Friction between the shell and mould is reduced
through the use of mould lubricants such as oils or powdered fluxes. Oscillation is achieved
either hydraulically or via motor-driven cams or levers which support and reciprocate (or
oscillate) the mould.
Mould oscillating cycles vary in frequency, stroke and pattern. However, a common approach
is to employ what is called "negative strip", a stroke pattern in which the downward stroke of
the cycle enables the mould to move down faster than the section withdrawal speed. This
enables compressive stresses to develop in the shell that increase its strength by sealing surface
fissures and porosity.

Page | 18
 Secondary Cooling
Typically, the secondary cooling system is comprised of a
series of zones, each responsible for a segment of controlled
cooling of the solidifying strand as it progresses through the
machine. The sprayed medium is either water or a
combination of air and water. To increase the rate of
solidification, the strand is sprayed with large amounts of
water as it passes through the spray-chamber; this is the
secondary cooling process. Final solidification of the
strand may take place after the strand has exited the spray-
chamber.
Three (3) basic forms of heat transfer occur in this region:
 Radiation: The predominant form of heat transfer in the upper regions of the secondary
cooling chamber, described by the following equation:
Q = σEA(Ts
4
− Ta
4
) [3.5.1]
Where σ is the Stephan-Boltzmann constant, E is the emissivity constant (≈0.8), A is the
surface area, Ts and Ta are steel surface and ambient temperatures respectively.
 Conduction: As the product passes through the rolls, heat is transferred through the shell
as conduction and also through the thickness of the rolls, as a result of the associated contact.
This form of heat transfer is described by the Fourier Law:
Q =
KA(Ti − To)
∆X
[3.5.2]
For conductive heat transfer through the steel shell, k is the shell's thermal conductivity,
whereas A and ∆X are the cross-sectional area and thickness of the steel shell, respectively,
through which heat is transferred. Ti and To are the shell's inner and outer surface
temperatures, respectively.
 Convection: This heat transfer mechanism occurs by quickly-moving sprayed water
droplets or mist from the spray nozzles, penetrating the steam layer next to the steel surface,
which then evaporates. This convective mechanism is described mathematically by
Newton's Law of Cooling:
q = hA(Ts − Tw) [3.5.3]
Where h is a constant coefficient of heat transfer, A is the surface area, Ts and Tw are the
steel surface and spray water temperature.
Fig. 2.6: Secondary Cooling
Process

Page | 19
 Shell Growth
Shell growth can be reliably predicted from Fick's Law:
L = V (
D
k
)
2
[3.5.4]
D = shell thickness; L = Cast distance from mould steel meniscus from where solidification
begins; V = Casting speed; k is an empirical constant determined from cast grade and machine
design.
 Metallurgical Length
Metallurgical length, is
defined as the distance from
the mould at which the strand
becomes totally solid. It is a
parameter which depends
upon the casting speed and
secondary cooling rate. The
metallurgical length is a
complex function of steel
composition, casting speed,
cooling rate and strand
dimensions.
 Strand Containment
The containment region is an integral part of the secondary cooling area. A series of retaining
rolls contain the strand, extending across opposite strand faces. Edge roll containment may also
be required. The focus of this area is to provide strand guidance and containment until the
solidifying shell is self-supporting. In order to avoid compromises in product quality, careful
consideration must be made to minimize stresses associated with the roller arrangement and
strand unbending. Thus, roll layout, including spacing and roll diameters are carefully selected
to minimize between-roll bulging and liquid/solid interface strains.
Strand support requires maintaining strand shape, as the strand itself is a solidifying shell
containing a liquid core that possesses bulging ferrostatic forces from head pressure related to
machine height. The area of greatest concern is high up in the machine. Here, the bulging force
is relatively small, but the shell is thinner and at its weakest. To compensate for this inherent
weakness and avoid shell rupturing and resulting liquid steel breakouts, the roll diameter is
small with tight spacing. Just below the mould all four faces are typically supported, with only
the broad faces supported at regions lower in the machine.
 Bending and Straightening
Equally important to strand containment and guidance from the vertical to horizontal plane are
the unbending and straightening forces. As unbending occurs, the solid shell outer radius is
under tension, while the inner radius is under compression. The resulting strain is dictated by
Fig. 2.7: Diagram illustrating Metallurgical Length

Page | 20
the arc radius along with the mechanical properties of the cast steel grade. If the strain along
the outer radius is excessive, cracks could occur, seriously affecting the quality of the steel.
These strains are typically minimized by in-corporating a multi-point unbending process, in
which the radii become progressively larger in order to gradually straighten the product into
the horizontal plane.
After straightening, the
strand is transferred on
roller tables to a cut off
machine, which cuts the
product into ordered
lengths. Sectioning can be
achieved either via torches
or mechanical shears. Then,
depending on the shape or
grade, the cast section will
either be placed in inter-
mediate storage, hot-
charged for finished rolling
or sold as a semi-finished
product. Prior to hot rolling,
the product will enter a
reheat furnace to adjust its
thermal conditions to
achieve optimum metal-
urgical properties and
dimensional tolerances.
2.6 CAUSES OF DEFECTS IN THE CAST PRODUCT
XX.AND PREVENTION
There are five categories of failure for the strand:-
1. Internal Cracking
2. Surface cracking
3. Center segregation
4. Inclusion Content
5. Oscillation Marks
Fig. 2.8: Diagram illustrating Bending and Straightening Zone

Page | 21
Internal cracking and surface cracking is decided by the strains and stresses in strand during
casting. Possible measures to prevent crack formation are optimizing mould powder and mould
oscillation to result in an oscillation mark depth < 0.2mm and to provide good maintenance
regarding misaligned rolls.
Center segregation can be reduced by choosing a combination of casting speed and secondary
cooling rate so that the point of solidification is well within the soft reduction zone. Having
done so the next step of optimization is to increase the soft reduction level further to achieve a
greater thickness reduction.
Inclusion content can be lowered by making sure that the residence time for liquid steel in
tundish is as long as possible. This is achieved by maintaining a high level of steel in the tundish
and/or casting at lower speeds.
In order to minimize the depth of the oscillation marks it is essential to properly optimize the
oscillation settings. The negative strip time should be as close to 0.11 s as possible combined
with a stroke that results in the smallest possible oscillation mark depth. The negative strip time
(hatched areas) is the main influencing factor for the formation of oscillation marks. Increasing
negative strip time is accompanied with increasing depth of oscillation marks.
A breakout will occur if the ferrostatic pressure exceeds the strength of the strand shell. It is
avoided by ensuring the shell thickness at any given point in the strand is sufficient to carry the
weight of the liquid steel above this point .Since the probability of breakout increases with a
decreasing shell thickness, it is very important to maintain a high steel level in the mould and
to have as low superheat as possible. This allows the shell to solidify to an adequate thickness
before the steel leaves the mould. Given that a thin shell might break under the pressure of the
liquid steel, oscillation marks should be kept as shallow as possible.
Depending on its precise composition, the linepipe steel grade can either be peritectic or hypo-
peritectic. Peritectic compositions are very crack sensitive, and so require more careful casting
to avoid cracks forming and propagating through the shell to cause breakout.


A BRIEF DISCUSSION ON
5 ROLL SET
General Overview, Location, Different Parts Present
in 5 Roll Assembly & Description
Chapter 3

Page | 22
A BRIEF DISCUSSION ON
5 ROLL SET
3.1 INTRODUCTION & GENERAL OVERVIEW
5 roll sets are an integral component of the traditional slab caster machines used for continuous
casting process. Although 5 roll sets may not find their application in the latest forms of the
continuous casting machines yet they still form an integral part in the traditional slab casters
still widely used in most steel plants. The 5 roll set design has been introduced by the aid of
the Russian technologies since the 1970’s and are still adopted by SAIL.
5 roll sets form the first of the numerous sets of rolling assemblies used in the rolling strand of
slab caster. Located just below the mould, the chief function of 5 roll sets is to provide better
support to the slab being cast in the earlier stages of the continuous casting process. As the Cast
Slab starts to solidify at the mould, 95% of the slab remains in hot liquid form and only rest
5% solidifies at the surfaces of the Slab-wall. So, if the support is less, then it is more prone to
break-out. Break-out means the extraction of liquid hot metal from any leakage or crack
developed on the solidified walls of the cast slab. So it is mandatory to provide more support
points to the cast slab when it is not fully solidified i.e. having maximum liquid hot metal inside
it in the earlier stage of Continuous casting.
Also 5 roll sets play an integral part in the secondary cooling process of the cast slab. The
process of primary cooling starts in the mould and the secondary cooling starts in the 5 roll
assembly of the rolling strand. The 5 roll sets in a rolling strand are provided with supply of
water through a network of water pipes attached to the assembly which spray water on the cast
slab while it is supported by the 5 roll set and thus secondary cooling is achieved. 5 rolls thus
have several usage in a slab caster and it is used in radial type slab caster or single point bending
continuous casting machines. In this report we discuss the preparation of 5 roll assemblies used
in slab caster and a detailed study of its individual components their production, application,
failure and reclamation.
Fig. 3.1: 5 Roll Assembly Set of CCS

Page | 23
3.2 LOCATION OF 5 ROLL SETS
The arrangement of rollers in the slab caster is described in the diagram above. The sequence
of the rollers along with their brief details is stated below:
 The mould is situated on top of the rolling strand. In case of radial slab caster machines the
curvature starts from the mould part itself.
 Just below the mould the 5 roller assembly set is situated which marks the beginning of the
rolling strand. The roller diameter is generally 140 mm in this section.
 The ten roller assembly set follows the 5 roll assembly set. The ten roll assembly provides
further support to the cast slab. The roller diameter is generally kept 180 mm.
 Four types of Radial Pinch rolls are situated after the ten roll assemblies. The four types of
pinch rolls used are described below:-
1. Pinch roll 320 (the rollers are having diameter ϕ 320 mm). Six sets of such rollers are
used in each machine, with each set consisting of four rollers. One roller is connected
to the driver motor hence called the drive roller while the rest three are idle rollers.
2. Pinch roll 360 (the rollers are having diameter ϕ 360 mm). Four sets of such rollers are
used in each machine, with each set consisting of four rollers. The arrangement of drive
roller and idle roller is the same.
3. Pinch roll 400 (the rollers are having diameter ϕ 360 mm). Four sets of such rollers are
used in each machine, with each set consisting of four rollers. The arrangement of drive
roller and idle roller is the same.
4. Pinch roll 450 (the rollers are having diameter ϕ 450 mm). Three sets of such rollers
are used in each machine, with each set consisting of four rollers. The arrangement of
drive roller and idle roller is the same.
Fig. 3.2: Location of 5 Roll Assembly Set in CCM

Page | 24
The pinch roller assemblies complete the radial zone. The radius of curvature is maintained
at 12 metres.
 After the radial section the straightening zone begins. This is the terminal part of the rolling
strand as the slab enters the unbending zone followed by the horizontal section. 5 sets of
rollers are used in this portion with a roller diameter of approximately 480 mm.
3.3 DIFFERENT PARTS PRESENT IN A 5 ROLL
XX.ASSEMBLY
A 5 roll assembly generally consists of the outer frame to which the rollers are attached. The
frame which is generally made of mild steel or fabricated steel generally consists of a number
of parts like the big radius , the small radius, the pressure plates ,column etc. Along with this
various parts like the L-plates , Lock plates , End Cover and Ring are inlcuded in the working
drawing of the 5 roll sets.
Each 5 roll set consists of 30 rollers altogether with a diameter of 140 mm and length 648 mm
approximately. The rollers consist of the following parts:-
i) Axle
ii) Bearings
iii) Inner ring
iv) Outer ring
v) Steel clips
Detailed sescription of various parts of the 5 roller assembly along with their working drawing,
materials used along with their chemical composition and certain design criterias to be
considered during production are mentioned in this context.
Fig. 3.3: Various Parts of Dismantled Roller

Page | 25
 L-Plate
The above diagram shows the working drawing of the L-plates used in 5 roll sets.
The material used in manufacturing of the L-Plates is generally termed as Fe410WA under the
standard of IS 2062-92. Fe410WA is a kind of structural steel with IS standard. The carbon
content in this steel is less than 0.2% and hence they are used to roll sections. The rolled
sections are higly bendable, ductile and easily weldable. Thus it can be easily understood why
Fe410WA is often the first choice while dealing with the materials for various equipments of
5 roll sections.
The weight of the specimen is about 0.54 kg. Dimensions are taken from the actual part. The
roughness of the specimen is generally indicated by the roughness symbol ∇ which indicates
the reference Ry/Rz length is about 8 mm. The Ra value varies from 25 – 12.5 mm and the
roughness grade number used can be N11 or N10.

Page | 26
 Lock Plate
The above diagram shows the working drawing of the Lock plates used in 5 roll sets.
The Lock plates are used in roller bearing assemblies to hold the roller bearing end cap to the
outer end of an axle journal in order to prevent the accidental removal of the capscrews and
hence they are an integral component of the 5 roller sets. The Locking plate is held in place
by a grease fitting extending through the aperture and threaded into the end cap.
The material used in manufacturing of the Lock Plates is generally termed as Fe410WA under
the standard of IS 2062-92. Fe410WA is a kind of structural steel with IS standard. The carbon
content in this steel is less than 0.2% and hence they are used to roll sections. The rolled
sections are higly bendable, ductile and easily weldable. Thus it can be easily understood why
Fe410WA is often the first choice while dealing with the materials for various equipments of
5 roll sections.
the reference Ry/Rz length is about 8 mm. The Ra value varies from 25 - 12.5 mm and the

Page | 27
 Ring
The above diagram shows the working drawing of the rings used in bearings of the rollers used
in the 5 roll sets.
The rollers are guided by a flange on the inner ring. This stops the rollers from sliding out at
high speed due to their momentum.The roller bearings ususally consist of the following
components:- the outer ring, inner ring and the roller assembly.

Page | 28
The material used in the manufacturing of these rings is ‘Heat resistant Low Alloy Chromium
Cast Iron’. Such irons have high abrasive rsistance and also they can show high resistance to
impact loading. They also have high corrosion resistant properties due to their chemical
composition.
The purpose for such chemical composition of low chromium alloy cast iron are explained
below:
i) The high carbon content (3.0 to 3.7% approx.) is prescribed when maximum abrasion
resistance is desired.
ii) Silicon is needed for two reasons. Fristly a minimum amount of silicon is required to
enhance fluidity of the melt. However it has further importance due to its effect on as-
cast-hardness. Increased amount of silicon increases the amount of martensite and the
resulting hardness.
iii) Manganese is typically held to a maximum value of 0.8 ~ 1 %. While it provides
increased hardenen-ability to avoid pearlite formation, it is also a more potent austenite
stabiizer than nickel and promotes increased amount of retained austenite and lower
as-cast-hardness.
iv) Chromium is primarily added in order to offset the graphitizing effects of nickel and
silicon.
v) Sulphur improves the machinability properties but has little effects on the longitudinal
mechanical properties
vi) Phosphorous increases strength and hardness but at the expense of ductility and impact
to toughness.
The chemical composition of such type of iron used is given below:
i) Carbon(C) – 3.0 to 3.7%
ii) Silicon(Si) – 1.3 to 2.5%
iii) Manganese(Mn) – 1.0 Maximum %
iv) Sulphur(S) – 0.12 Maximum %
v) Phosphorous(P) – 0.3 Maximum %
vi) Chromium(Cr) – 0.3 to 1.1 %
Hardness HB 163-210
The following things should be noted during the production and designing of rings:-
i) Casting should be free from all casting defects
ii) Non-perpendicularity of the surface with respect to the axis of ϕ 113 should not be more
than 0.3 mm
the reference Ry/Rz length is about 8 mm. The Ra value varies from 25 – 12.5 mm and the

Page | 29
 End Cover -1
The above diagram shows the working drawing of the end covers used in the 5 roll sets.
End covers are available for roller bearing units fitted at shaft ends. In addition to protecting
the shaft ends of bearing arrangements, they also play a key role in preventing accidents.The

Page | 30
designation of appropiate end covers are generally available in the product tables (SYNT series,
FYNT series). The permissible length of the shaft end and the allowable protrusion dimensions
of the end cover are also provided. Sometimes end covers are used to replace the complete seal
at that side of the bearing.
According to the standrads set by SKF the end covers can be broadly categorised in to two
different units:-
i) End covers for metric SKF ConCentra units
These end covers can be snapped easily intp the recess of the housing bore, on the
mounting collar side.
ii) End covers for Inch SKF ConCentra units and units with a locking collar
End covers in this series are mounted with an interference fit on the housing bore.They
are always supplied together with the bearing units.
Cast Iron’. Such irons have high abrasive rsistance and also they can show high resistance to
impact loading. They also have high corrosion resistant properties due to their chemical
composition.
The chemical composition of such type of iron used is given below:
i) Carbon(C) – 3.0 to 3.7%
Hardness HB 163-210
The following things should be noted during the production and designing of end cover:-
i) Radial runout of bore ϕ 60 A4 with respect to its axis should not be more than 0.05 mm.
ii) Taper & ovality of bore should not be more than half the tolerances on diameter.
iii) Non-perpendicularity of the surface ‘S’ with respect to the axis of Φ60 A4 should not
be more than 0.05 mm on ϕ 79.5.
roughness of the specimen in the periphery is generally indicated by the roughness symbol ∇∇
while the rest is given by the roughness symbol ∇. ∇∇ symbol corresponds to Ra values of 6.3,
3.2, 1.6 (N9, N8, N7) while for ∇ symbol Ra values vary from 25 to 12.5 (N11, N10).

Page | 31
 End Cover -2
The above diagram shows the working drawing of the end covers used in the 5 roll sets.
Cast Iron’.The chemical composition of such type of iron used is given below:
i) Carbon(C) – 3.0 to 3.7%
Hardness HB 163-210
The following things should be noted during the production and designing of end cover:-
i) Radial runout of ϕ 110 X3 with respect to its axis should not be more than 0.06 mm.
ii) Non-perpendicularity of the surface ‘R’ with respect to the axis of ϕ 113 X3 should not
be more than 0.05 mm on Φ110 X3.
roughness of the specimen in the periphery is generally indicated by the roughness symbol ∇∇
while the rest is given by the roughness symbol ∇. ∇∇ symbol corresponds to Ra values of 6.3,
3.2, 1.6 (N9, N8, N7) while for ∇ symbol Ra values vary from 25 to 12.5 (N11, N10).

Page | 32
 Axle-1
The above diagram shows the working drawing of the axle used in the rollers of the 5 roll
assemblies.
The Axle is the component which sustains the roller when it is assembled into the troughing
set supports. It is made from drawn steel, cut and machined by automatic numerically
controlled machines. The axle is the load carrying component of the roller and must be sized
in relation to the load and the roller length. It is important not to overload the roller due to the
resultant excessive deflection of the spindle which in turn places irregular pressure on the
bearing, and reduces, as a consequence, the roller life.
Axles are generally round or hexagonal shaped. Hexagonal axles are specified by the length
across the flats. Round axles are specified by their diameter. The most common axle sizes are
7/16" hex and 11/16" hex. Axles are mostly made from either Mild Steel or Stainless Steel.
Axles are generally retained by a spring or cotter pins. Springs are held in place with dimples
stamped into the material .Cotter Pins are put into holes drilled thru the axle. Other axle
retention methods include:
i) Hog Rings
ii) Spring Both Ends
iii) Fixed or Staked
Axle machining offers other options for retaining the axle. Some of the axle operations include
the following processes:-
i) Drilled and Cut
ii) Threaded
iii) Milled slot for keeping bar

Page | 33
iv) Milled flat
v) Turned
vi) Snap Ring Groove
The material used in the manufacturing of these axles is termed as ‘40Cr1’ under the Indian
Standard IS 1970. This is a kind of alloy steel which is used in axle manufacturing.
The table given below enlists the properties of 40Cr1 in hardened and tempered condition:
Designation
of Steel
Tensile
Strength
(kgf/mm2
)
Yield
Stress
Minimum
(kgf/mm2
)
Normalizing
Temperature
℃
Hardening
Temperature
℃
Quenching
Medium
Tempering
Temperature
℃
40 Cr 1 80-95 60 850-880 850-880 Oil 550-660
The chemical composition of such type of ally steel used is given below:
i) Carbon(C) – 0.35 to 0.45%
iii) Manganese(Mn) – 0.50 to 0.80%
Hardness HB 220-250.
The following things should be noted during the production and designing of axles:-
i) Radial runout of ϕ 60 Xn with respect to its axis should not be more than 0.05mm.
ii) Non-concentricity of the surfaces P and Q (ϕ 60 Xn) with respect to each other should
not be more than 0.025 mm.
iii) Ovality and taper of the surfaces P and Q (ϕ 60 Xn) should not be more than 0.02 mm
in diameter.
iv) Radial runout of ϕ 58 X3 with respect to the axis of ϕ 60 Xn should not be more than
0.05 mm.
v) Non-perpendicularity of the surface G with respect to the axis of ϕ 60 Xn should not
be more than 0.025 mm.
roughness of the specimen in the periphery is generally indicated by the roughness symbol ∇∇∇
and at some of the edges by the roughness symbol ∇∇. The rest of the surface roughness is
denoted by the roughness symbol ∇. From the various charts regarding roughness symbols and
roughness grade numberswe can conclude that the roughness symbol ∇∇∇ corresponds to the
roughness value (Ra) value of 0.8, 0.4, 0.2 and the roughness grade numbers concerned are N6,
N5, N4. ∇∇ symbol corresponds to Ra values of 6.3, 3.2, 1.6 (N9, N8, N7) while for ∇ symbol
Ra values vary from 25 to 12.5 and the roughness grade numbers concerned are namley N11
and N10.

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 Axle-2
The above diagram shows the working drawing of the axle used in the rollers of the 5 roll
assemblies.
The material used in the manufacturing of these axles is termed as ’40Cr1’ under the Indian
Standard IS 1970. This is a kind of alloy steel which is used in axle manufacturing.
The following things should be noted during the production and designing of axles:-
i) Radial runout of ϕ 60 Xn with respect to its axis should not be more than 0.05mm.
ii) Non-concentricity of the surfaces P and Q (ϕ 60 Xn) with respect to each other should
iii) Ovality and taper of the surfaces P and Q (ϕ 60 Xn) should not be more than 0.02 mm
in diameter
iv) Radial runout of ϕ 58 X3 with respect to the axis of ϕ 60 Xn should not be more than
0.05 mm
v) Non-perpendicularity of the surface G with respect to the axis of ϕ 60 Xn should not
be more than 0.025 mm
Hardness HB 220-250.
denoted by the roughness symbol ∇. The roughness symbol ∇∇∇ corresponds to the roughness
value (Ra) value of 0.8, 0.4, 0.2 (N6, N5, N4). ∇∇ symbol corresponds to Ra values of 6.3, 3.2,
1.6 (N9, N8, N7) while for ∇ symbol Ra values vary from 25 to 12.5 (N11, N10).

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 Rollers
The above diagram shows the working drawing of the rollers of the 5 roll assemblies.
Technical requirments regarding manufactuing of the specific rollers:-
1. Material Specification and other technology requirements shall be as per RDCIS, SAIL-
RANCHI No. RD/SCR/FF-95 Dt. 10-12-96
2. Ovality and taper of Bore ϕ 110 An should not be more than half of the tolerance on
diameter.
3. Non-concentricity of Bore ϕ 110 An marked ‘P’ & ‘Q’ with respect to each other should
4. Non -perpendicularity of the surface ‘R’ & ‘S’ with respect to axis of ϕ 110 An should
5. Radial runout of surface ϕ 110 An should not be more than 0.05 mm.
6. Radial runout of surface ϕ 140 G with respect to axis of ϕ 110 An should not be more than
0.05 mm.
7. Annular groove of ϕ 120, 2 mm depth on both faces of the roller, is provided for
identification of these rollers, among rollers produced earlier.
8. This plain roller as per RDCIS recommendation is the modified version of the earlier
grooved roller as per DRG. No. CC-90-017.2.

Page | 36
Although the main purpose of rollers used in 5 roll sets is for providing better support to the
cast slab, the rollers also have a host of other applications. Below are listed some common
situations and the ways in which rollers are specialized to best handle these conditions. Keep
in mind that a particular application may include several of the following scenarios.
i) Gravity Applications
Rollers are not directly driven and only rotate when product passes over them. For light
products rollers are light-weight and bearings are lightly oiled to reduce rotational friction.
Bearings may be grease packed for heavier products that can easily overcome rotational
friction.
ii) Powered Applications
Rollers are directly driven by belts, chains, or other means. Rollers may be rotating even when
product is not present. Bearings are grease packed to maintain lubrication through more
continuous use.
iii) High Speeds
Rollers are subjected to operating speeds above 250 RPM. Rollers are built with light weight
tubes that are straightened to tight tolerances to reduce imbalances and prevent bouncing.
Bearings are semi-precision or precision for prolonged service life. When operating speeds
exceed 400 RPM rollers are built using only precision bearings.
iv) Heavy Loads
Rollers are subjected to large live loads during normal use. For small, light-duty rollers, a heavy
load may be less than 100 lbs. For large, heavy-duty rollers, a heavy load may be more than
1000 lbs. Rollers are built with components that are large enough to resist deflection. At long
BF’s a Center puck may be added to the axle to prevent the axle from deflecting too far and
rubbing along the inside of the tube.
v) Stationary Loads
Rollers are subjected to long periods of being loaded but not rotating. Rollers are built with
thicker tubes to prevent denting from prolonged loading on just one side of the tube. Bearings
feature hardened raceways to resist denting and cages, or retainers, that keep the balls evenly
spaced around the bearing to evenly distribute the load. Bushings may also be used due to their
high static load capacities.
vi) Impact Loads (Shock Loading)
Rollers are subjected to objects colliding with them. Products may have uneven bottoms that
cause them to bounce along the rollers or products may be dropped or thrown while being
loaded onto the rollers. Rollers are built with heavy walled tubes to resist denting. Bearings are
high capacity to reduce the risk of damage. Bushings may be used due to their lack of moving
(breakable) parts.
vii) Dirty/Gritty Environment
Rollers are subjected to small particles of dirt or dust that can contaminate bearing lubrication
and prevent the bearings from rotating. Bearings feature contact seals and shields that prevent

Page | 37
particles from entering. Bearings may also be regreaseable so that lubrication can be regularly
flushed. Bushings may also be used due to their lack of moving parts or need for lubrication.
The material used in the manufacturing of the rollers is generally high chromium steel having
chromium content as high as 13%. Addition of chromium increases the corrosion resistance
greatly.
The specification for forged quality foot rolls and 5 set rolls are given below:-
1. Scope:
The specification covers the requirement of forged and heat treated top rolls (140 mm
dia.) of continuous slab casting machines.
Composition (%):
C = 0.25 - 0.30 Ni = 1.0
Mn = 0.80 max. Mo = 0.60 – 0.80
Si = 0.70 max. P = 0.040 max.
Cr = 12 - 14 S = 0.025 max.
2. Forging Operation:
Forging shall be made as per IS: 1570 Pt. V – 72 and will be supplied duly deal treated
and in finish machined condition as per drawings. The forging could be produced in
multi-piece blanks which must be parted of into individual rolls before final hardening
treatment. The forging will have following mechanical properties in hardened and full
tempered condition;
UTS > 950 MPa %E > 10%
YS > 750 MPa BHN = 280 – 320
3. Processing Parameters:
A. Forging Temperature Range = 1100 – 900 ℃
(Charge hot forgings for controlled furnace cooling before the temperature falls
before - 650℃)
B. Soft Annealing (8 hrs.) = 720 – 730 ℃
(Furnace cool up to 250℃)
C. Hardening Treatment:
All forging will be rough machined including bores with heat treatment allowance
& subjected to total surface inspection to ensure freedom from any surface defects
including bore before hardening as per the following:
i) Preheating (2 hrs.) – 700 – 720℃
ii) Cooling – Air/oil/salt bath (60 minutes)
iii) Austenitising (2 hrs.) – 980 + 5℃
(After hardening immediately charge for tempering treatment. Any of the electric
furnace/ salt bath furnace or gas fired furnace should be utilized for heat treatment.
Finish machining/grinding allowance so be left on rough machined forgings before
hardening treatment should be decided on the basis of type of I I.T. furnace used)
D. Tempering Treatment:
Hardness – HB: 280 – 320 = 620 + 5℃ (12 hrs.)/air cool

Page | 38
4. Finish Machining:
All forging after heat treatment shall be finish machined / grind as per dimensions and
other instructions given in the drawings.
5. Ultrasonic Testing:
All forging shall be ultrasonically tested after heat treatment with test frequency more
than 2 MHz. The forging shall be from ultrasonic defects except isolated flow echo with
maximum level of 50% with 100% back echo.
The following things should be noted during the production and designing of rollers:-
i) After hot forging the forged blanks must be controlled, cooled in furnace and in no
case these will be allowed to cool in air below 650℃.
ii) After cooling the forgings will be inspected for surface quality and shall be finally
soft annealed before rough machining.
iii) All the annealed forgings must be rough machined including bore with heat
treatment allowances (2 – 3 mm) on the surface and will be visually inspected for
any surface flaw on outer as well as bore surfaces. Preferably few sample pieces in
the developmental stage could be magnaflux tested to ensure freedom from any
surface defect.
iv) The other processing norms and metallurgical parameters may be kept as per
standard operating practices.
The weight of the specimen is about 46 kg. Dimensions are taken from the actual part. The
denoted by the roughness symbol ∇. From the various charts regarding roughness symbols and
roughness grade numberswe can conclude that the roughness symbol ∇∇∇ corresponds to the
roughness value (Ra) value of 0.8, 0.4, 0.2 and the roughness grade numbers concerned are N6,
N5, N4. ∇∇ symbol corresponds to Ra values of 6.3, 3.2, 1.6 (N9, N8, N7) while for ∇ symbol
Ra values vary from 25 to 12.5 and the roughness grade numbers concerned are namley N11
and N10.

Page | 39
 Bearings
The above diagram shows the working drawing of the bearing used in the rollers of the 5 roll
assemblies.
The materials from which the bearing components are made determine to a large extent the
performance and reliability of rolling bearings. For the bearing rings and rolling elements
typical considerations include hardness for load carrying capacity, fatigue resistance under
rolling contact conditions, under clean or contaminated lubrication conditions, and the
dimensional stability of the bearing components. For the cage, considerations include friction,
strain, inertia forces, and in some cases, the chemical action of certain lubricants, solvents,
coolants and refrigerants. The relative importance of these considerations can be affected by
other operational parameters such as corrosion, elevated temperatures, shock loads or
combinations of these and other conditions.
Contact seals integrated in rolling bearings can also have a considerable impact on the
performance and reliability of the bearings. The materials they are made of have to offer
excellent oxidation, thermal or chemical resistance. In order to meet the needs of various
applications, SKF uses different materials for bearing rings, rolling elements, cages and seals.
Furthermore, in applications where sufficient lubrication cannot be achieved or where an
electric current passing through the bearings has to be prevented, SKF bearings can be supplied
with special coatings.
The bearing which is generally used in the rollers of 5 roll sets is of bearing 6212 type.
According to the bearing nomenclature rules the inner diameter of such bearing is 5 times the
last two digits of the bearing name and hence the inner diameter of bearing 6212 is 60 mm.The
type of bearing used is deep groove ball bearings,single row hybrid bearings.
Principal Dimensions Basic Load Ratings Speed Ratings Mass Designation
Inner
Dia.
Outer
Dia.
Breath Dynamic
Load
Limit
Static
Load
Limit
Fatigue
Load
Limit
Reference
Speed
Limiting
Speed
d D B C Co Pu
mm mm mm KN KN KN r/min r/min kg
60 110 22 55.3 36 1.53 17000 4000 0.71
6212-2RS1/
HC5C3WT

Page | 40
Bearings are manufactured to take pure
radial loads, pure thrust loads, or a
combination of the two kinds of loads.
The nomenclature of a ball bearing is
illustrated in the adjoining figure which
also shows the four essential parts of a
bearing. These are the outer ring, the inner
ring, the balls or rolling elements, and the
separator. The bearings are the parts
which give virtually frictionless rotation
to the tube body with respect to the fixed
spindle. Bearings are the most complex
and critical part of a roller. Bearings come
in a wide variety of sizes, shapes, and
features that all offer different
performance characteristics. Bearing
capacity does not dictate roller capacity.
Roller load capacity is usually dictated by axle or tube deflection. Higher capacity bearings in
a long roller will not necessarily change the load capacity of the roller. Bearing capacity is
usually the limiting factor of roller capacity only at short BF’s. In a rolling bearing the starting
friction is about twice the running friction, but still it is negligible in comparison with the
starting friction of a sleeve bearing. Load, speed, and the operating viscosity of the lubricant
do affect the frictional characteristics of a rolling bearing.
Fig. 3.4: Nomenclature of Ball Bearing
Fig. 3.5: Various Types of Ball Bearing

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The various types of ball-bearings are shown in the above figure. The single-row deep-groove
bearing will take radial load as well as some thrust load. The use of a filling notch in the inner
and outer rings enables a greater number of balls to be inserted, thus increasing the load
capacity. The angular-contact bearing provides a greater thrust capacity. Single-row bearings
will withstand a small amount of shaft misalignment of deflection, but where this is severe,
self-aligning bearings may be used. Double-row bearings are made in a variety of types and
sizes to carry heavier radial and thrust loads. Sometimes two single-row bearings are used
together for the same reason, although a double-row bearing will generally require fewer parts
and occupy less space. The one way ball thrust bearings are made in many types and sizes. All
these bearings may be obtained with shields on one or both sides. The shields are not a complete
closure but do offer a measure of protection against dirt. A variety of bearings are manufactured
with seals on one or both sides. When the seals are on both sides, the bearings are lubricated at
the factory. Although a sealed bearing is supposed to be lubricated for life, a method of re-
lubrication is sometimes provided.
The following things should be noted during the production and designing of 6212 bearings:-
i) Deep groove geometry for high speeds and supporting both radialand axial loads.
ii) “Light” bearing design for use in limited space applications or for average loads.
iii) C3 radial clearance allows thermal expansion for continuous opeating temperatures up to
120 degrees C/248 degrees F.
iv) Sheet steel cage evenly spaces balls for reduced friction , vibration, and noise.
v) Open bearing for lubrication applied in place.
Preloading of straight roller bearings may be obtained by:
i) Mounting the bearing on a tapered shaft or sleeve to expand the inner ring,
ii) Using an interference fit for the outer ring,
iii) Purchasing a bearing with the outer ring pre-shrunk over the rollers.
Ball bearings are usually preloaded by the axial load built in during assembly. The permissible
misalignment in bearings depends on type of bearing and the geometric and material properties
of the specific bearing. The object of preloading is to remove the internal clearance usually
found in bearings, to increase the fatigue life, and to decrease the shaft slope at the bearing.
In general, cylindrical and tapered roller bearings require alignments that are closer than deep-
groove ball bearings. Additional protection against misalignment is obtained by providing the
full shoulders recommended by the manufacturer. Also, if there is any misalignment at all, it
is good practice to provide a safety factor of around 2 to account for possible increases during
assembly. The life of the bearing decreases significantly when the misalignment exceeds the
allowable limits.
Felt seals may be used with grease lubrication when the speeds are low. The rubbing surfaces
should have a high polish. Felt seals should be protected from dirt by placing them in machined
grooves or by using metal stampings as shields. The commercial seal is an assembly consisting
of the rubbing element and, generally, a spring backing, which are retained in a sheet-metal
jacket. These seals are usually made by press fitting them into a counter bored hole in the
bearing cover. Since they obtain the sealing action by rubbing, they should not be used for high
speeds.


PREPARATION OF
5 ROLL SET
Introduction, Description of Process, Instruments
Used in Reassembling
Chapter 4

Page | 42
PREPARATION OF 5 ROLL SET
4.1 INTRODUCTION
In earlier chapters the description of the various components of the 5 roll assembly sets of
Continuous Casting were discussed. The damaged and rejected parts of the 5 roller sets, once
they are no longer fit to be used, are removed from the rolling strand and they are sent to the
respective repairing and reassembling workshops for their reclamation and to be made fit for
further usage. MARS-2 is established for repairing of the damaged or malfunctioning
equipment of the machines of various shops including Continuous Casting Shop. In MARS-2
the repairing of 5 Roller Assembly Set of Continuous Casting Shop is done in several steps. In
this chapter we discuss about the various processes undertaken by the workshop for reclamation
of the damaged parts and preparation of new parts for the 5 roll assemblies.
4.2 DESCRIPTION OF THE PROCESS
The whole process can be classified into three basic processes:
A. Dismantling & Separating the Parts
B. Repair or Reclamation of Parts
C. Assembling the 5 Roll Assembly Set
A. Dismantling & Separating the Parts
This process involves several steps which are discussed below:
1. First of all, the set must be placed in a proper place and cleaned by removal of all the
impurities and dust particles that have accumulated inside the rollers and the frame. In
Continuous Casting Process, the semi-solidified metal chips got stuck in the assembly
set and often rollers got stuck. So, dedusting is necessary before further Dismantling
process can be started. In this case, by blowing high pressure air all dust particles are
removed and the semi-solidified metal chips are often removed by oxy-acetelene flame
cutting.
2. After cleaning the assembly set, the entire
assembly is placed with the help of the crane
in such a way that the Big Radius remains in
the upward direction and the Small radius in
downward direction. This particular position
of the assembly is necessary because the big
radius is separated first by shifting it with the
help of crane and placing it in another place. Fig. 4.1: Use of Crane for Shifting Big Radius

Page | 43
3. In order to separate the big radius from the assembly,
firstly the bolts [4×2×2 =16; Dimensions: M48×200
for 200 mm gap & M 48×300 for 250 mm gap],
clamping Big Radius and Small Radius must be
unbolted and kept at a proper place. Each of the Big
Radius and Small Radius have eight bolts each. This
bolts are used to keep the big radius and small radius
attached firmly to the frame. Before removal of the
rollers, separating of the Big Radius and Small Radius
is necessary such that the removal process of rollers
become easier.
4. In order to separate the big radius and small radius, a proper sling is used. The sling is
tightly attached to the Big Radius manually and then the sling is hooked up with the help
of the hook (having capacity of 10 T) of the crane of the Assembly Bay [Fig. 4.1].
5. Once the Big Radius is hooked up, it must be kept at a proper place to remove its rollers.
The Big Radius is oriented in vertical position as per the Fig. 4.2.
6. After that, the bolts of the rollers and L – Plate, Lock Plates are removed. Then, all
rollers [3×5 = 15] are separated from the frame by applying external force with the help
of a rod and are arranged in a place in order.
7. Now, once the rollers are removed from the frame the axle is the first to be removed.
The axle extends out on both side and so manual hammering is enough to take it out.
After the axle is removed the outer rings are removed by fixing a rod from the other side
and hammering is done. Along with outer rings comes out the inner ring and bearing.
The same is done for the other side also. If the bearing gets stuck inside due to damage
or increase in friction due to dust, so oxy-acetylene arc is used for metal gas cutting.
8. Thereafter the Small Radius frame must be placed properly so as to dismantle its rollers
[3×5 = 15] and plates present in the frame, then it must be properly clamped. Following
the same way, the roller’s nuts and bolts, axles must be carefully dismantled of Small
Radius.
Fig. 4.2: Orientation of Big Radius
Fig. 4.3: Separated Parts of the Roller

Page | 44
In this way, all parts of the 5 roll assembly set are dismantled properly with the help of
various instruments and machines.
B. Repair or Reclamation of Parts
The parts of damaged or malfunctioning rollers can be treated in two manners depending
upon its use and damage:
1. Reclamation & Reuse of parts
2. Rejection & Replacement of parts
The bearings, axle that are undamaged should be cleaned and properly greased to be reused
again. This method of reusing is known as reclamation. In this case, the bearings are
generally heated in oil bath to remove any soil, dust or grease whatever is stuck in side of
the bearing dissolves and comes out of it. So, the bearing gets cleaned and can be reused
again.
Lubrication in Bearing:
If rolling bearings are to operate reliably they must be adequately lubricated to prevent
direct metal-to-metal contact between the rolling elements, raceways and cages. The
lubricant also inhibits wear and protects the bearing surfaces against corrosion. The choice
of a suitable lubricant and method of lubrication for each individual bearing application is
therefore important, as is correct maintenance.
A wide selection of greases and oils is available for the lubrication of rolling bearings and
there are also solid lubricants, e.g. for extreme temperature conditions. The most favorable
operating temperatures will be obtained when the minimum amount of lubricant needed for
reliable bearing lubrication is provided. However, when the lubricant has additional
functions, such as sealing or the removal of heat, additional amounts of lubricant may be
required.
Fig. 4.4: Rejected Rollers

Page | 45
The lubricant in a bearing arrangement gradually loses its lubricating properties as a result
of mechanical work, ageing and the build-up of contamination. It is therefore necessary for
grease to be replenished or renewed and for oil to be filtered and changed at regular
intervals.
Defects in Rollers:
The rollers are dusted to remove any surface impurities and metal flux. If the cracks in
rollers are observed the rollers are rejected. Often the rollers get flattened brings about a
change in curvature, due to the high temperature and pressure. In this case, the rollers are
rejected because they increase the number of contact points that may become a cause of
break-out. If any crack is noticed in axle, then it is also replaced with new one. If the axle
becomes deformed or bends due to hammering or any kind of other pressure, then it is
subjected to grinding operation in order to bring its correct shape. In general, defects in
rollers are due to defective bearing damaged by soil, dust and grease. To remove these,
bearings are heated in oil-bath; thus the dust, soil are precipitated and grease dissolves in
the oil. Then the bearings are cleaned & regreased and in this way bearings become
reusable. This process is called ‘Reclamation’.
C. Assembling of the 5 Roll Assembly Set
The steps to assemble the 5 roll assembly set are the following:
1. The process of assembling the frame starts by assembling of roller. The rollers are
assembled in the way the rollers are dismantled. The sequence of assembling follows the
procedure similar to dismantling, i.e. one that goes out last is the first to be inserted. The
inner, outer rings along with bearings are attached to roller first on both sides. The inner
rings are attached then the bearings and after that the outer rings. Hence the axle is
assembled. The bearings are attached with steel clip to remove slip.
2. In the sequence of placing rollers in frame, the rollers of the Big Radius are attached first.
While placing rollers in roller place they must be provided with correct sling and kept on
frame following methods/commands of only one person. The rollers are fixed to the frame
by using L-clamp and bolts for fixing it with pedestal.
3. The rollers of the two end rows are fixed first. These two rows are aligned with the help of
a straight edge. The height of the rollers from the base of the Big Radius is 310 mm when
the Big Radius is oriented in such a way that the rollers are above. Their height from the
Fig. 4.5: Assembling the Rollers

Page | 46
surface in contact with pressure plate is 264 mm. The bolts used for bolting the two end
rows are M20×120 mm.
4. Next, the central three rows are fixed with the help of two aligned side rollers and a
template. This template is a measure to make the 5 roll set get the exact curvature of 12 m.
The template has a radius of 12 m, of dimensions 1650×150 (mm). The bolts used in these
three rows M20×140 mm. The three rows in the middle are provided with pegging, often
of 1-0.5 mm thickness at the bottom for increased height and thus 140mm length bolts are
used as they have to cover a further depth. The rollers are adjusted with lock plates. The
three rows in the middle are movable or replaceable but those at the periphery are fixed.
5. Then the Big Radius and Small Radius are both assembled to reconstruct the frame. The
separated parts are again placed upon one another in the correct position and then they are
assembled together by means of clamping and bolting together. The bolts used here are
M48×200 –for 200 mm gap and M48×300 – for 250 mm gap. The pressure plates used
vary as 20 mm –for a 200 mm slab, 70 mm –for a 250 mm slab and two plates of 70 mm
are used one on top and other at bottom for 320 mm slab. The washers used are of 52 mm
diameter.
6. While placing rollers in Small Radius frame the rollers are adjusted with the aligned Big
Radius maintaining the optimum distance with a micrometer.
The distance between the corresponding rollers of big radius and small radius must be
maintained. The distances vary as:
a. 1st
roller after mould – 251.70 mm
b. 2nd
c. 3rd
d. 4th
e. 5th
7. Finally this distances are checked by Micrometer. The extra width is provided between the
rollers prior to 250 mark in order to provide the much needed clearance and to also ensure
that the cast slab does not get stuck within the rollers. The extra width is provided with the
help of pegging’s which have minimal thicknesses.
Fig. 4.6: Rows of Rollers

Page | 47
The total frame dimension is 3400X800 mm. The total distance between the rolls is
2000mm and the slab that is rolled has a width of 1500mm.
4.3 VARIOUS INSTRUMENTS USED IN THE
XX.REASSEMBLING PROCESS
1. Inside Micrometer
The micrometer is a precision measuring instrument, used by engineers. Micrometer use the
principle of a screw to amplify small distances (that are too small to measure directly) into
large rotations of the screw that are big enough to read from a scale. The accuracy of a
micrometer derives from the accuracy of the thread- forms that are at its heart. The amount of
rotation of an accurately made screw can be directly correlated to a certain amount of axial
movement (and vice versa), through the constant known as the screw’s lead. A screw’s lead is
the distance it moves forward axially with one complete turn (360).
Parts of Micrometer:
Frame – The thick body that holds the anvil and barrel in constant relation to each other. It is
thick because it needs to minimize flexion, expansion and contraction, which would distort the
measurement. It is heavy to increase the thermal mass, to prevent substantial heating up by the
holding hand/fingers.
Fig. 4.7: Complete Assembly of 5 Roll Set
Fig. 4.8: Diagrams of Micrometer

Page | 48
Anvil – The shiny part that the spindle moves toward, and the sample rests against.
Sleeve/barrel/stock – The stationary round part with the linear scale on it.
Lock nut/ thimble lock – The knurled part that one can tighten to hold the spindle stationary.
Screw – It is inside the barrel.
Spindle - The shiny cylindrical part that the thimble causes to move toward the anvil.
Thimble – The part that one’s thumb turns.
Ratchet stop – Device on end of handle that limits applied pressure by slipping at a calibrated
torque.
The spindle of an ordinary metric micrometer has 2 threads per millimeter, and thus one
complete revolution moves the spindle through, a distance of 0.5 millimeter. The longitudinal
line on the frame is graduated with 1 millimeter divisions and 0.5 millimeter subdivisions. The
thimble has 50 graduation, each being 0.01 millimeter. Thus, the reading is given by the number
of millimeter divisions visible on the scale of the sleeve plus the particular division on the
thimble which coincides with the axial line on the sleeve.
2. Template
The template is a measuring instrument used to measure the radius of curvature of the rolling
strand including the 5 roll set. In case of 5 roll sets, the template is used to check whether it is
properly aligned with the exact radius of curvature of 12 m. The template has a radius of 12 m,
of dimensions 1650×150 mm. The template is used to check the alignment of the three set of
rollers in the middle while that at the two edges are checked with the help of straight edges.
The bolts used in these three rows M20×140 mm.
This instrument is used in MARS-2 during the assembling of the 5 roll sets to align the rollers
of Big Radius in the curvature of radius 12 m. Then, Template is again used in Continuous
Casting Shop to recheck its alignment after placing the 5 roll assembly set in the slab caster
machine below the mould before the machine is started.
Fig. 4.9: Diagram of Template

Page | 49
3. Straight Edge:
Straight Edge is a tool with and edge free from curves, or straight, used for transcribing straight
lines, or straight, used for transcribing straight lines, or checking the straightness of lines. If it
has equally spaced markings along its length it is usually called a ruler.
Straight edges are used in the automotive service and machining industry to check the flatness
of machined mating surfaces.
True straightness can in some cases be checked by using a laser line level as an optical straight
edge; it can illuminate an accurately straight line on a flat surface such as the edge of a plank
or shelf.
We use the straight edge for aligning the two rollers on the periphery. These two rollers are
aligned at a height of 310 mm from the base of Big Radius when oriented such that the rollers
are facing up.

Fig. 4.10: Diagram of Straight Edge

FAILURES IN 5 ROLL SET
AND MEASURES FOR
PREVENTION
Introduction, Failures in Bearings and Rollers, Their
Causes and Cures
Chapter 5

SAIL Bhilai Steel Plant 5 Roll Assembly Project Report

SAIL Bhilai Steel Plant 5 Roll Assembly Project Report

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