APROJECT REPORT

ON“Eliminating corner gap in sc

mould at LD2 SNC”

SUBMITTED BY:

Vinay kumarB.Tech

Machenical EngineeringB.A. College of Engg & Tech.

Jamshedpur.

GUIDED BY:Mr.Shaswat Anand

Manager-segment shop

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APPROVAL CERTIFICATEThe foregoing project report entitled “Elimnating corner gap in sc mould at LD2 SNC” submitted by Mr. Vinay kumar (Summer Intern ‘15 )is hereby approved as authentic study of his Project work during his vocational training at Tata Steel, Jamshedpur.It is presented in satisfactory manner to warrant its acceptance as a prerequisite in the completion of his vocational training.

GUIDEMr. Shaswat Anand

Manager-Segment Shop

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ACKNOWLEDGEMENT

Any accomplishment, big or small, has a number of persons behind the scene and I must acknowledge that this project was no exception.

First of all I would like to convey my gratitude to my guide Mr. Shaswat Anand (Manager-segment shop) for his continuous support during my project. He has been a constant source of encouragement during the entire project. He provided me valuable information as well as knowledge regarding my project. I

Finally, I would like to convey a word of thanks to “ TATA STEEL” administration for providing me this great opportunity to undergo my summer internship under its esteemed banner.

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TATA STEELAn Introduction

Established in 1907, Tata Steel is the world’s 6th largest steel company with anExisting annual crude steel capacity of 28MTPA. Asia’s first integrated steel plant& India’s largest integrated private sector steel company is now the world’s second most geographically diversified steel producer, with operations in 24countries &commercial presence in over 50 countries .Tata steel completed 100years of existence on August 26, 2007 following the ideals & philosophy laid down by its Founder , JAMSETJI NUSSERWANJI TATA. The first private sector steel plant which started with a production capacity of 1, 00,000 tones has transformed into a global giant.

J.N.Tata-The Founder An overview of TATA STEEL

Tata Steel plans to grow & globalize through organic & inorganic routes. Its 6.08MTPA Jamshedpur works plans to 10MTPA capacity by 2012. The company also has three Greenfield steel projects in the states of Jharkhand, Orissa &Chhattisgarh and proposed steel making facilities in Vietnam and Bangladesh.

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Through investments in Corus , Millennium Steel { Renamed Tata Steel Thailand }and NatSteel Asia , Singapore , the Tata steel has created a manufacturing and marketing network in Europe , South East Asia and the Pacific- rim countries. Corus, which manufactured 18.3 MT of steel in 2006, has operations in the UK, the Netherlands, Germany, France, Norway &Belgium. Tata Steel (Thailand) is the largest producer of long steel products in Thailand, with a manufacturing capacity of 1.7 MT. NatSteel Asia produces about 2 MT of steel products annually across its regional operations in seven countries. Tata Steel through its joint venture with Tata Blue Scope Steel limited has also entered the steel building and construction applications market.

The iron ore ones & collieries in India give the company a distinct advantage in raw material sourcing. Tata steel is also striving towards raw materials security through joint ventures in Thailand, Australia, Mozambique, Ivory Coast (West Africa) and Oman.

Tata Steel’s vision is to be the global steel industry benchmark for “Value Creation and Corporate Citizenship”.

Process Flow At Tata Steel

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SNTI (Shavak Nanavati Technical Institute)

• SNTI (Shavak Nanavati Technical Institute) the erstwhile Jamshedpur technical institute, was established in the year 1921 to provide the technically qualified human resource for Tata Steel.

• It was the inspiration of the founder of TISCO, “Let the Indians learn to do things by themselves” , which came into reality by the establishment of the institute.

• Today SNTI form an integral part of the HR management division of TATA STEEL.

• It has rendered commendable service in nation development of technical manpower not only for Tata Steel, but also for the steel plants in the public sector and other manufacturing industries.

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Corporate Functions

Shared Services (Provides Maintenance Services and Operates Utilities)

Marketing & Sales

Marketing & sales Division

Long Product

Marketing & Sales

Flat Product Marketing &

Sales Cust

omer

s

Rolling

Flat & Long Rolling Division

Wire Rod MillNew Bar MillMerchant Mill

Hot Strip MillCold Rolling MillCRC West Mill

Steel Making

Steel Making Division

LD#1

LD#2

Iron Making

Sinter Plant

Coke Plant

Blast Furnaces

Coke, Sinter & Iron

Division

Sinter

Coke

Ore Mines

& Quarri

es Divisio

n

West Bokar

o Divisio

nJharia Divisio

nRaw

Materials Division

RawMaterials

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What is steel?Steel is a compound of iron and carbon. Modern steels also use traces of magnesium, chromium, tungsten, molybdenum, manganese, nickel and cobalt. All of these can be used to varying degrees to help make the steel harder, lighter, more or less resistant to heat and electrical current, more ductile and corrosion resistant. Steels are a large family of metals. All of them are alloys in which iron is mixed with carbon and other elements. Steels are described as mild, medium- or high-carbon steels according to the percentage of carbon they contain, although this is never greater than about 1.5%.

Steel is an alloy of iron and other elements, including carbon. When carbon is the primary alloying element, its content in the steel is between 0.002% and 2.1% by weight. The following elements are always present in steel: carbon, manganese, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen and aluminum. Alloying elements intentionally added to modify the characteristics of steel include: manganese, nickel, chromium, molybdenum, boron, titanium, vanadium and niobium.[1]

Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

Alloys with a higher than 2.1% carbon (depending on other element content and possibly on processing) are known as cast iron. Because they are not malleable even when hot, they can be worked only by casting, and they have lower melting point and good castability.[1] Steel is also distinguishable from wrought iron, which can contain a small amount of carbon, but it is included in the form of slag inclusions.

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Though steel had been produced in a blacksmith's forge for thousands of years, its use became more extensive after more efficient production methods were devised in the 17th century. With the invention of the Bessemer process in the mid-19th century, steel became an inexpensive mass-produced material. Further refinements in the process, such as basic oxygen steelmaking (BOS), lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1.3 billion tons produced annually. It is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations.

What is steel production?When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable. To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. This liquid is then continuously cast into long slabs or cast into ingots. Approximately 96% of steel is continuously cast, while only 4% is produced as ingots.[12]

The ingots are then heated in a soaking pit and hot rolled into slabs, blooms, or billets. Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structural steel, such as I-beams and rails. In modern steel mills these processes often occur in one assembly line, with ore coming in and finished steel coming out.[13] Sometimes after a steel's final rolling it is heat treated for strength, however this is relatively rare

Iron ore pellets for the production of steel.

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How a steel plant work ?A plant has many needs for it to grow. The most important are: Carbon, hydrogen and oxygen Nitrogen, phosphorus, potassium Sulfur, calcium, and magnesiumThe most important of these are nitrogen, phosphorus and potassium. Nitrogen, phosphorus and potassium are important because they are necessary for these basic building blocks. For example: Every molecule making up every cell's membrane contains phosphorous. Potassium makes up 1 percent to 2 percent of the weight of any plant.Without these tree items, the plant could not grow because it can't make the pieces it needs. In nature, the nitrogen, phosphorous and potassium often come from the decay of plants.Steel is an alloy of iron and carbon. It is produced in a two-stage process. First, iron ore is reduced or smelted with coke and limestone in a blast furnace, producing molten iron which is either cast into pig iron or carried to the next stage as molten iron. In the second stage, known as steelmaking, impurities such as sulfur, phosphorus, and excess carbon are removed and alloying elements such asmanganese, nickel, chromium and vanadium are added to produce the exact steel required. Steel mills then turn molten steel into blooms, ingots, slabs and sheet through casting, hot rolling and cold rolling.

How is steel produce?There are two types of metals, ferrous & non-ferrous. Ferrous comes from, or contains iron, while Non-Ferrous does not contain iron.

Some examples of ferrous metals would be mild steel, cast iron, high strength steel, and tool steels.

Examples of non-ferrous metals would be copper, aluminum, magnesium, titanium, etc.

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To make steel, iron ore is first mined from the ground. It is then smelted in blast furnaces where the impurities are removed and carbon is added. In fact, a very simple definition of steel is "iron alloyed with carbon, usually less than 1%."

The following text is taken from the Structural Manual For Ironworkers Manual V-Volume I.

Blast furnaces require many auxiliary facilities to support their operations. However, in simplest terms, the furnace itself is a huge steel shell almost cylindrical in shape and lined with heat-resistant brick. Once started, or "blown-in," the furnace operates continuously until the refractory lining needs renewal or until demand for iron drops to the point where the furnace is closed down. The duration of furnace operations from start to finish is referred to as a "campaign" and may last several years.

Iron ore and other iron bearing materials, coke and limestone are charged into the furnace from the top and work their way down, becoming hotter as they sink in the body of the furnace which is called the stack. In the top half of the furnace, gas from burning coke removes a great deal of oxygen from the iron ore. About halfway down, limestone begins to react with impurities in the ore and the coke to form a slag.

Ash from the coke is absorbed by the slag. Some silica in the ore is reduced to silicon and dissolves in the iron as does some carbon in the coke. At the bottom of the furnace where temperatures rise well over 3000 Fahrenheit, molten slag floats on a pool of molten iron which is four or five feet deep. Because the slag floats on top of the iron it is possible to drain it off through a slag notch in the furnace. The molten iron is released from the hearth of the furnace through a tap hole. The tapping of iron and slag is the major factor permitting additional materials to be charged at the furnace top.

This brief summary of the complex operations of a blast furnace is presented here to provide a point of reference for the actual flow of operations. Very often, several blast furnaces may be arranged in a single plant so that the most efficient possible use can be made of fuels, internal rail facilities, etc

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2.0) MATERIAL HANDLING PROCESS AT TATA STEELUnder 3.0MTPA Expansion Projectof Tata Steel the following facilities have been installed at Jamshedpur works in addition to its present operations:1.0) Pellet Plant 6.0MTPA: Produces pellets for Blast Furnace 2.0) Blast Furnace 3.0 MTPA: Produces pig iron from

Ore/Sinter/Pellet, and Coke & PCI Coal

3.0) Coke Oven Battery: Produces coke from coal for Blast Furnace

4.0) Lime Kilns#8&9: Produces lime from lime stone for LD#35.0) LD#3: Produces steel from pig ironand uses limeThe following basic raw materials are required for operation of above plants.

1. Blast Furnace – Coke, Sinter, Ore/additives, Pellet and PCI coalCoke Ovens – Coal

2. Lime Calcining Plant – Lime stone,3. Pellet Plant – Iron ore fines, 4. LD: Lime and additives

In order to handle huge amount of several varieties of raw materials for above production units, Tata Steel has installed fully automated bulk material handling system. This document outlines the study of material handling process and the associated automation systems for operation of Raw Material Handling systems.

Primarily raw material handling process broadly covers the following activities:

1. Raw materials receiving from various sources thru rail/road2. Unloading of incoming raw materials3. Transfer of raw materials from unloading points to

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4. Stock piling of materials5. Reclaiming anddistribution of raw materials from storage/stock piles thru conveying system to consuming production plants

The automation system associated with materials handling system ensures safe and energy efficient handling of materials in desired quantities as per requirements by the production units without any losses or with minimum losses.

The Material handling system consists the following major equipment:

1 Weigh bridges 13 Belt Feeders

2 Track hoppers 14 Weigh Feeders3 Plough feeders 15 Vibrating Feeders4 Wagon Tippler 16 Vibrating Screens5 Apron feeder 17 Surge hoppers6 Stacker cum

reclaimer18 Reversible

Conveyors7 Bucket wheel

stacker cum reclaimer

19 Reversible shuttle conveyor

8 Traveling Tipper 20 Reversible hammer mill

9 Conveyors 21 Double roll coke crusher

10 Magnetic separators

22 Twin Boom Stacker

11 Bucket wheel on boom reclaimer

23 Barrel Reclaimer

12 Bins

The operations of the above equipment are fully controlled by using PLC’s (Programmable Logic Controllers) and facilitate remote operations from control rooms.

Apart from PLC automation, there are several other systems facilitate safe operation of the handling process in auto.

1. Electrical motors/drives2. Safety switches

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3. Metal detectors4. Magnetic Separators5. Belt Scales6. CCTV monitoring7. Fire Detection and Alarm systems8. Communication systems

Among all material handling equipment, the conveying system plays major role to transfer the bulk raw materials from one place to other. The conveying system used in Tata Steel is elaborated further

LD SHOP DESCRIPTION • The LD shop takes in Hot metal from the blast furnace and

refine them so that it can be turned into refined steel before being cast into billets and slabs depending on the requirements.

• In Tata Steel there are presently LD#1, LD#2, LD#3 and TSCR departments for the above mentioned process.

LD#2 ShopThe main units of LD#2 Shop are:-1). Hot metal receiving and Handling2). Desulphurization3). Basic oxygen furnace4). Online purging 5). Ladle furnace6).RH degasser7). Gas cleaning plant8).Secondary emission plant

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LD#2 Shop Process The hot metal is received in the torpedo pits of the LD

shop via torpedo (capacity is 200T to 320T) from the blast furnace.

The metal received is crude in terms of the composition and needed to be further refined.

The first step in LD#2 shop is DESULPHURIZATION process, the Sulphur content is controlled in this process.

The desulphurization process takes place in the D.S unit where calcium carbide and magnesium are used to and the sulphur is brought down to the target level depending on the grade requirements.

The next step is the BOF process. This is the most widely used steel refining process and this was first introduced in the towns of Linz and Donowitz and hence the name LD.

In the LD converter Oxygen is blown from the top of the converter to reduce the carbon content also various additives like fluxes, Ferro alloys and scrap is added to stabilize the process and to produce the required grade

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of Steel. The metal obtained is called “Primary Refined Steel”

The steel after refining in the BOF is tapped and is sent to the Ladle furnace where the trimming additions takes place to fine tune the steel compositions.

In the ladle furnace the molten steel is heated by means of electrode to maintain temperature wire feeding system for Ferro alloy.

From the ladle furnace the steel is sent to the caster for casting into billets or slabs.

In certain cases where high quality and cleanliness is required the steel is sent t the RH(Ruhrstahl -Heraeus) facility which is a vacuum degassing unit to further reduce carbon, oxygen, nitrogen and hydrogen content.

Overview of LD2 & Slab Caster 1.

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LD-2Supplied by S.N. Portugal of Portugal LD 2 was commissioned in 1993. With two BOF vessels from VAI, the plant has a rated capacity of 1.10 million tonnes. Hot metal is supplied in 200 t nominal capacity torpedo ladles from the blast furnaces. The metal is poured into 150 t transfer ladles at the hot metal pouring pit .The hot metal in the transfer ladle is desulphuriser at the desulphurization unit after removing the slags and thereafter, taken to the converters.

The details of hot metal handling system are:

Hot Metal Receiving: The input Hot Metal comes from Furnaces A, B, C, D, F, G, H & I in torpedo ladles of 220tons.

Torpedo Area: Hot Metal from Torpedo is transferred to ordinary Transfer Ladle of 150tons capacity by tilting the Torpedo. From 2 torpedoes we get metal for three heats.

Hot Metal Desulphurization: Initially BF Slag is raked of with the help of raking machine. Then desulphurisation starts with the injection

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of CaC2 & Mg injection through refractory lance with Nitrogen as the carrier gas. The lance dips inside the metal and injection starts. Sulphur of the hot metal removes in the form of CaS & MgS and floats up. This is raked off. The time of DS depends on the initial ‘S’ content of the hot metal & the final product specification required.

Converter: The 3 BOF vessels have been supplied by SMS Demag. Pig iron in the transfer ladle is taken inside the BOF vessels for controlled oxidation using lance heater. At this stage additives are added to prepare the required blend of steel. Inert gas, Argon is blown in order to maintain the uniformity of the hot metal.

Lance heater used for oxidation contains 3 concentric flow paths.The centre flow path is used for blowing oxygen into the vessel and the other 2 flow paths are used to water cooling of lance.At the time of oxidation, the lance goes deep into the vessel so that uniform oxidation can take place. Slag formation takes place in the upper part of the vessel whereas molten steel in produced in the lower part. Slag is removed by tilting the vessel from the top of the vessel into a ladle transfer car below and the steel is poured into another ladle below it from the neck opening of the vessel by tilting it in opposite direction.

Steel in the ladle now is taken for further secondary metallurgical processing in SMLP (Secondary Metallurgical Ladle Processing) shop mentioned below.

Different Routes: Different routes of steel making are mentioned below:

Converter-Caster(30-35% Heats) Converter-RH-Caster(18-20% Heats) Converter-LF-Caster(50-55% Heats) Converter-LF-RH-Caster(6-8% Heats)

RH Degasser: The process was developed by Rheinstahl Heinrich in 1957. The process in named after him. In order to produce steel for high-end applications, liquid steel is routed through. This degassing unit in which treatment takes place under vacuum.The degassing chamber is a cylindrical steel shell with two legs called snorkels and the openings at the top side are provided for exhaust,

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alloy additions, observations and control. During degassing metal enters the cylindrical vacuum chamber through one snorkel and flows back under gravity through other. The chamber is lifted and lowered to an appropriate level in the ladle containing molten steel. The chamber is evacuated and the molten steel just rises in the chamber. The atmospheric pressure causes the molten steel to rise above the, still bulk level, in the snorkel, under deep vacuum. Lift gas like argon is then introduced in the inlet snorkel which expands and rises up thereby raising the velocity of steel in the inlet snorkel. The net result of this is that degassing takes place very efficiently. Gravity causes steel to flow back in the ladle via the other snorkel. Degassed steel is slightly cooler and denser than in the ladle and hence it forces the lighter undegassed steel upwards thereby ensuring adequate mixing and homogeneity. At the end of the process alloy additions may be made depending upon the superheat available in the steel.

Ladle Furnace: Liquid steel from the converter is tapped into preheated ladles and then treated at the ladle furnace for homogenization, increase of temperature and for trimming additions are done. It is a simple ladle like furnace provided with bottom plug for argon purging and lid with electrodes to become an arc furnace for heating the bath. Another lid may be provided to connect it to vacuum line, if required. Chutes are provided for additions and an opening even for injection. It is capable of carrying out stirring, vacuum treatment, synthetic slag refining, plunging, injection etc. all in one unit without restraint of temperature loss, since it is capable of being heated independently.

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2. Slab CasterThere are three single strands continuous casting machine which have been specifically designed to cast high quality slabs suitable for hot charging to the Hot Strip. The main machine at LD#2 and Slab Caster was modified to include a new vertical mould and Bender/Straightener Segments, up gradation of ladle turret, modification of the Tundish. Car and existing segments, augmentation of hydraulic systems including pipe work, instrumentation & automation system and numerous attendant changes for the Company to manufacture more demanding grades of steel.The slab casting machine has been specifically designed to cast high quality slabs at higher yield, low cost and high productivity.

The machine is equipped to cast 215mm thick and 800-1550mm wide slabs. No.1 caster is vertical mould caster and other two are curved mould caster. Each bender strand has mould and a radius of 10m with a support length of 29.75m. The vertical caster has a radius of 7.5m over this length this slab is initially supported by mould followed by cooling grids and then top and bottom rollers during solidification. The partly or fully solidified curved slab is removed by continuous straightening method prior to withdrawal and final solidification. Hot metal for casting is supplied from converters via secondary steel

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making facilities. The charged ladle with steel in its optimum state is transported to position. As the turret is rotated, the Tundish is driven over the mould from its pre-heat station by a Tundish car. Ladle shroud is then fixed for shrouding of ladle to Tundish stream. Once all “ready to cast” interlocks are healthy, casting is started.

The mould is mounted on pivot arms supported from mould table support frame and is water-cooled. This mould support frame also locates and supports the top-zone. This is an important of machine as it ensures correct relationship between mould, top-zone and strand guides. The pivot arms carrying the mould are oscillated to improve surface finish of slabs by means of oscillation.

As the slab emerges from mould, it is cooled by a mist-spray cooling system. The cooling strand is guided down by various roller segments following the caster radius along a curved path. The upper sections of segments can be raised hydraulically and are held by means of hydraulic cylinders against packers, which are pre-set to give required slab thickness. Immediately following the strand guide segments is the straightener segment. This segment is designed to continuously remove the curvature of the strand as it passes through the segment.From the straightener, slab passes into withdrawal unit which has 7 segments arranged horizontally to support the slab as it progresses towards cut-off machine. As strand emerges from cast withdrawal rollers, the dummy bar disconnect mechanism is activated. The slabs are cut into lengths by oxygen/gas machine which is supported on rails. As the predetermined length is sensed, the machine lowers on to the slabs and travels with the slabs at casting speed. The twin burners mounted on cross carriages, cut the slab from either end. The discharge roller table then transports the slabs to the cross transfer area. The slabs are marked online by an Al-spray marking machine on their way to the cross transfer.

Some Benefits:

Increase Casting speed for ultra-low carbon steelReduce blister defects in the hot rolled productsSmaller roll pitches reduce strand bulging and bending / unbending strainsOptimization of mould oscillation parameters by using VAI DYNAFLEX hydraulic oscillation system.Straight mould ensures greater safety against breakouts.

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Increased cooling water for equipment and spray system.

Continuous Casting

Continuous Casting is the process whereby molten steel is solidified into a "semi-finished" billet, bloom, or slab for subsequent rolling in the finishing mills. Prior to the introduction of Continuous Casting in the 1950s, steel was poured into stationary mould to form "ingots". Since then, "continuous casting" has evolved to achieve improved yield, quality, productivity and cost efficiency. It allows lower-cost production of metal sections with better quality, due to the inherently lower costs of continuous, standardized production of a product, as well as providing increased control over the process through automation. Steel is the metal with the largest tonnage cast by this process, although aluminium and copper are also continuously cast.

In Continuous Casting molten metal is tapped into the ladle from furnaces. After undergoing any ladle treatments, such as alloying and degassing, 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 machine; one ladle is 'on cast' while the other is made ready, and is switched to the casting position once the first ladle is empty.From the ladle, the hot metal is transferred via a refractory shroud 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 feed metal feed to the mould and cleaning the metal buffer of hot metal as 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 m to 2 m, depending on the casting speed and section size. The mould is water-cooled and oscillates vertically to prevent the metal sticking to the mould walls. 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 still be present in the metal and bring them to the top of the pool to form a floating layer of slag. Often, the shroud is set so the hot metal exits it below surface of the slag layer in the mould and is thus called a submerged entry nozzle (SEN). In the mould, a thin shell of metal next to the mould walls solidifies before the metal 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

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closely-spaced, water cooled rollers; these act to support the walls of the strand against the Ferro static pressure of the still-solidifying liquid within the strand. To increase the rate of solidification, the strand is also sprayed with large amounts of water as it passes through the spray-chamber. Final solidification of the strand may take place after the strand has exited the spray-chamber.

Important Components of Continuous Casting:

LadleTundishSubmerged Entry Nozzle (SEN)MouldSegmentsTorch Cutting Machine

Ladle: Steel from the electric or basic oxygen furnace is tapped into a ladle and taken to the continuous casting machine. The ladle is raisedonto a turret that rotates the ladle into the casting position above the Tundish. Liquid steel flows out of the ladle into the Tundish. Ladle slide gate valves are used for greater pouring accuracy, increased ladle hold time, and safer and easier ladle preparation.

Tundish: 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 ladleExchanges

Maintains a steady metal height above the nozzles to the moulds, thereby keeping steel flow constant and hence casting speed constant as well.

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Provides more stable stream patterns to the mould.

Ladle shrouds are used for stream protection and reduction of steel re-oxidation between ladle and Tundish.

Submerged Entry Nozzle: From the Tundish the molten metal enters the mould through a shroud. Often, the shroud is set so the hot metal exits it below surface of the slag layer in the mould and is thus

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called a submerged entry nozzle (SEN).Submerged Entry Nozzles are used in the steelmaking process to prevent re-oxidation of the molten steel directly from stream contact with the surrounding environment and from air entrainment and splashing when the molten stream strikes the liquid surface in the mould. Elimination of accretion formation and the associated clogging of SENs will lead to increased strand speed, greater time between changes of SENs, and reduced strand termination incidence.

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. The working surface of the copper face is often plated with chromium or nickel to provide a harder working surface, and to avoid copper pickup on the surface of the cast strand, which can facilitate surface cracks on the product.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.

Segments: Segments are the set of rollers which helps the semi solidified slabs to move from the mould to the torch cutting machine through the guide rollers. Generally the rollers of the segments are in taper form so that compression of the slab up to 3 meters is possible.

Torch Cutting Machine: Torch cutting machine is used to cut the solidified slabs into desired length according to the demand. The torch cutting machine in Tata Steel is supplied by GEGA.

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Commissioning Milestone of LD2 & Slab Caster

Equipment Month Year

Slab Caster 1 October 1993Ladle Furnace 1 October 1993

Slab Caster 2 July 1994LD Convertor 1 and GCP October 1994LD Convertor 2 and GCP December 1994

DS Plant 1 June 1995RH Degasser September 1996

Gas Recovery Of Convertor no. 1 March 1996Gas Recovery Of Convertor no. 2 March 1996

Slab Caster 3 July 1998DS Plant 2 August 1998

LD Convertor 3 October 1998Ladle Furnace 2 February 1999

Slab Yard Management System April 1999Gas Recovery Of Convertor no. 3 July 1999

Up gradation of Caster 1 - 2005Up gradation of Vessel 1,2,3 - 2006-2007

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IntroductionEMBR Mold: EMBR stands for Electro Magnetic Braking.

It is a special kind of a mold quite similar to the conventional mechanical (gear) mold in terms of physical appearance but hugely different from it in the working aspect. A mold is a hollow container used to give shape to molten or hot liquid material when it cools and hardens.

ELECTROMAGNETIC STIRRING AND ELECTRO – MAGNETIC BRAKE For CONTINUOUS CASTING

In order to continuously cast high quality steels for demanding purposes electromagnetic stirring are a must for billets and blooms. Stirring will improve strand quality, reproducibility, yield, production flexibility and productivity. For each application the optimum stirrer

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choice can be made taking into account the steel grades cast, the strand sizes, reduction ratio, etc. Optimizing the molten steel flow pattern is equally important for slab casting, and here the electromagnetic brake is a successful alternative to stirrers. Minimills with thin slab casting have quickly become real competition to the integrated mills and today very few integrated mills or conventional slab casters are being built or planned. One of the remaining issues for the integrated mills has been the steel quality, especially in terms of cleanliness and mold powder entrapments. However, this situation has changed with the introduction of the ElectroMagnetic BRake (EMBR) for thin slab casters.

EMBR MOLD is used for thin slab as well as conventional slab casters. It is a prerequisite when:-

Casting thin slabs with higher throughputs Aiming at higher quality segment.

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it facilitates nearly complete elimination of mold powder entrapments as a result of reduced flow speed and turbulence.

It greatly improves coil surface quality and operates at relatively higher speed than conventional steel casters.

It reduces mold copper wear, especially at higher casting speeds.

It reduces meniscus swelling resulting in a more even mold powder layer.

It increases productivity, product quality and lower operating costs.

Reduced Mold Powder Entrapments-Inclusions remain small and relatively harmless because of the Ca-treatment of the steel. Because of this and the high casting speed normally used for thin slabs, mold powder entrapments constitutes the major source of detrimental non-metallic inclusions.With EMBR, the lower meniscus flow speed and the turbulence results in that mold powder entrapment will be nearly eliminated.More than 90% of the non-metallic inclusions are eliminated.

Improved Core Quality-Higher speed of casting means low quality. When using an optimized EMBR, the quality level at higher throughputs is improved. The quality becomes equal or better to the quality level to that for significantly lower casting speeds without EMBR.

Reduced Meniscus Swelling-The braking reduces the meniscus swelling close to the narrow mold sides. The resulting flatter meniscus allows for a more even layer of molten mold powder, thus improving lubrication and reducing the risks of surface cracks.

EMBR increases mold lifetime-EMBR lowers the mold level fluctuation. Temperature cycling and thermal fatigue of the copper plates are dramatically reduced.Twice as more mold lifetime from casters using EMBR.

Increases Steel Temperature at Meniscus-

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Heat transfer from the middle of the mold to the solidification front is reduced.Hot steel is not pushed down into the strand but kept up higher in the mold, resulting in an increase of steel temperature at meniscus.

Components of EMBR Mold:-

Wide and narrow plates Electromagnets Primary cooling system Lateral roll Spreading system Narrow plate cylinder Secondary cooling system

Wide and narrow plates - EMBR mold consists of two narrow plates and two wide plates arranged perpendicular to each other to create a rectangular opening if seen from top.

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An EMBR mold. The left plate is the movable wide plate.

Wide plateThe distance between the wide plates implies the thickness of the slab to be cast which is normally about 215 in

LD#2 Slab caster#1.

Narrow plates

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The distance between the narrow plates implies the width of the slab. The plates are coated with pure copper of thickness 40 mm on one side which are further coated with nickel and cobalt for improving the wear resistance of pure copper as pure copper is costly and degrades every 450-600 heats (1 heat=160 tonnes). The thickness of this nickel and cobalt coating increases from 0.5 mm at the top to 2 mm at the bottom of the plates. The junction of the copper coating and the plates is connected to thermocouples which indicates the temperature of that point in a screen. Copper is an excellent conductor of heat and electricity, hence the heat from the molten steel is transferred is transferred to the thermocouple via the copper coating so that the temperature and the flow of the molten steel could be monitored analytically.The thermocouples are welded to their slots in the plates.There are 4 rows and 11 columns in each of the wide plates while the narrow plates have 4 rows and 2 columns each with a total of 104 thermocouples.

The narrow plates are kept inclined at an angle of 1.1-1.28 degrees towards the lower portion so that the molten steel ,which goes on solidifying and hence consequently decreasing in dimension upon solidifying, does not just slip from in between the plates. The movement of the narrow plates are very slow which is 0.8 m/min. Each narrow plate is connected to two servos, one at the top and the other at the bottom, which facilitates its movement in or out. In every round of command given to the servos the narrow plates move by 12.5 mm. There are two methods of movement of the narrow plates so that the molten steel which is solidifying remains in a healthy position. These are:-

S type H type,

Depending on the motion which is used to cause the movement.

The plates contain cut lines (as shown in the figure) to facilitate the free circulation of water in the plates to keep the temperature

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moderate and the plates cool as well as prevent the copper coating from getting degraded.

Electromagnets - When molten steel is poured into the mold there is a lot of turbulence in it which greatly tend to hamper the properties of the steel which is being casted. Hence to obtain higher grade and better quality steel the EMBR mold has electromagnets which greatly tend to nullify this turbulence by developing a high current electromagnetic field. The electromagnets are attached to the wide plates and are totally 4 in number.

The control room screenshot of the electromagnets and its cooling system/mechanism

There are two sets of coil on each of the wide plate or strand (visible in the figure). There are two strands, namely: Strand 1 upper coil, and Strand 1 lower coil.Each of the strands now further has two coils as we discussed above. Strand 1 upper coil has: Coil 11A

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Coil 11B

Strand 1 lower coil has: Coil 12A Coil 12B

Each of the coils is water cooled continuously to maintain and regulate the temperature. The water used here is a special kind of water called “de mineralized water”. The properties of this cooling system are as follows:

Inlet temperature = 41 °C (according to data) Outlet temperature = 56, 59, 56, 60 °C (data for 4 coils)Pressure = 6 barFlow rate = 200 l/minConductivity = 0.1360-1.418 µs/cm

The EMBR electromagnet will trip under the following conditions: When the inlet temperature is 48 °C or more than that, and When the conductivity>2 µs/cm. (it has to be less than 2 at all

times).

The current and voltage required to produce the electromagnetic field is 560 Ampere and 180 volts respectively.

Primary cooling system - Primary cooling system implies the cooling of the plates. The wide and narrow plates bear an intense amount of heat from the molten steel so the need to be cooled down. This is also done to ensure the safety of the copper plates. The water used in this system is soft water.Soft water circulates in Wide plate at 4000 Lpm. Narrow plate at 550 Lpm

Lateral roll - These are the rolls attached to the bottom of the mold just below the plates to direct the solidifying steel towards the bender and from where it proceeds on to the segments. These are three in number. The average casting speed is 10218 m/min.

Spreading system- It consists of 4 hydraulic cylinders. It is used for increasing the thickness of the slabs as per requirement. One of the wide plate is kept fixed while the other is movable to adjust

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the thickness. These 4 cylinders are fixed at 4 corners of the fixed plate.

One end of the cylinder is fixed at the fixed end where it is clamped and declamped (ie. Cylinder movement off and on resp.). Upon declamping a hydraulic oil of very high viscosity index (around 400) is made to enter the cylinder at very high pressure. This applies pressure on the piston and pushes it inwards and this piston subsequently pushes the movable plate. The amount by which the movable plate has to be moved depends on the amount of the hydraulic oil made to enter the cylinder and is measured by a gauge attached to it. When the appropriate thickness has been achieved the cylinder is again clamped to make the movable plate static at this new position.

Narrow plate cylinder- there are 4 hydraulic cylinders placed in the mold for the movement of the narrow plates. Each narrow plate is attached to two cylinders, at the top and at the bottom.These cylinders are connected to the servo valve and position transducer. These receive the data from the operator and move the narrow plates very slowly at the rate of 0.8 m/min.

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As seen in the figure, the servo valve is located in the leftmost box. Attached to it on its right is the cylinder. The servo facilitates the cylinder movement which is connected to the the narrow plate with the help of a thread strand.The main difference between the EMBR mold and other molds is that here in EMBR molds the narrow plate’s movement is due to the valves whereas in the normal molds it is due to the arrangement of gears.

Secondary cooling system - This refers to the cooling of the molten steel to form a slab. The slab of steel that comes out of the mold is molten from inside and solid from outside due to cooling. Since we desire completely solid slab hence water is sprayed on to it from the moment the slab gets out of the mold till

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the very last segment

Secondary cooling systemThe water used in this system is normal tap water and is sprayed on the slab directly perpendicular it from a pipe whose ends are made flat in order to make sure that they come out with force and cover the maximum surface area.If this is not present then the heat from the molten steel inside the solidified shell will cause the shell to melt and ultimately leading to breakout or bleeding.

Problems39 | P a g e

There are various problems in a steel caster. These are mentioned below with their frequency of happening in the form of a graph:

Problem wise distribution of unplanned mold change

Mold changes in FY ’12 and FY ‘13 Above plot shows various problems during operation of mold in

a slab caster. 3 major problems with mold is Breakout, Ramming problem and

Slab Bulging which share almost 80% of total mold problems. Breakout is out of scope as research work is in progress for this

problem but it sure can be brought under control. How? We will see this further in this project.

My scope was to work for Corner Gap Elimination as it’s the major cause for breakouts that take place in casters.

The biggest problem in a steel caster is that of breakout or bleeding.Bleeding is a term used when the solid shell of the slab ruptures and the molten metal flows out. This condition will keep out the caster from running for a considerable amount of time.

When bleeding occurs all the steel that is in the mold flows out.

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Steel from the tundish and ladle also drains which amounts to the spillage of more than 200 tonnes of steel.

The segments also get damaged upon coming in contact with the molten steel, thus creating more problems in terms of maintenance, safety, reinstallation, etc.

A major hazard could be sensed when the molten metal flows and occupies positions in the lower areas and solidify there.

Metal removal is yet another challenge that has to be faced.

In steel industry, ideally the caster is expected to be in the running condition all the time, never stopping even for a minute until the shutdown of the caster. Even if the caster stops for a minute it will be termed as a loss because some amount of steel would have been casted during that time. So when bleeding or breakout occurs one can very well imagine the loss that the company faces.

Breakout/bleeding occurs due to the following reasons:

Corner gap developed between the narrow and wide plates Coating problem/level fluctuations Improper calibration at various points Taper loss due to less or excessive angle of taper.

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Data Table 1

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Data table 2On analyzing the above data one can easily suggest that corner gap is to be held accountable for more than half of the times when breakouts have occurred. Hence if corner gap issue is brought under control then productivity as well as income will increase and the amount of loss would go down to a huge extent.

Corner gap problem: Corner gap is the gap that is developed between the two adjacent narrow and wide plates upon continuous casting. Corner gap is essential in molds. It is so because the width arrangement for the slabs is done by the movement of narrow plates under the influence of the servo. Now if the adjacent narrow and wide plates are in contact with each other giving zero corner gap then the narrow plate, upon movement, would graze the copper coating of the wide plates which is undesirable. Hence some amount of corner gap

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must be present in the mold but it must not increase so as to create problems.

Ideally corner gap should be 0.6 mm at the top and 0.9 mm at the bottom. At the bottom more corner gap is needed because of the increasing thickness of nickel and cobalt coating as well as considering the shrinkage of the slab upon its movement downward.

Corner gap

It was observed however that once the mold was put into position, in caster, corner gap abnormally increased to more than 1 mm, thereby causing breakouts.

The following fishbone diagram will explain the vaious factors responsible for a high corner gap. This diagram considers almost every factor responsible for its cause because in order to remove a problem every thing must be taken care of.

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Counter Measures47 | P a g e

Solution #1: Stopper modificationSince corner gap was a major issue it was tried to get under control by adding an external stopnness over and above the four clamping bolts to check the distance by which the loose plate can move. But it proved to be ineffective. Increased Corner gap was tried to eliminate using stopper in three ways:

PDCA 1:

PDCA 1: flexible due to cantilever design support

Drawback : Not able to stop due to deflection.48 | P a g e

PDCA 2:

PDCA 2: shims between two rigid stoppers

Drawback : able to stop but difficult to set 0.4 mm.

Wedge type stoppers with locking facility

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Solution #2: Mold and bender alignmentOn the failure of stopper arrangements to control the increase in corner gap, an alternate and reliable solution was needed.

The force required to compress high tensile Sa3O4 grade steel by 0.8 mm was calculated. This force was too big for any usual explanation.

After that another aspect was looked upon- alignment of mold and bender. Upon observation it was found that the foot rolls and the bender rolls were not aligned properly.

ACTUAL REASON FOR THE OCCURRENCE OF CORNER GAP- Due to ferrostatic force or misalignment forces, all looseness in entire tie rod assembly and elongation of rod was responsible for loose plate to be pushed back and create the gap.

Result Hence the root cause of the problem was found out and appropriate measures were adopted to avoid it. The frequency of breakout was greatly reduced which is implied from the following data:-

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Total number down

The level difference of dark blue bar and the light blue bar indicates the progress.

Thank You

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