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AN INDUSTRIAL REPORT ON

DURGAPUR STEEL PLANT

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Acknowledgement

I would like to express my gratitude to Mrs. Reeta Banerjee, Manager of Center for human resource

development (CHRD), Durgapur steel plant for giving an opportunity to do the summer training.

I would like to thank specially Mr. Pradeep sett, Deputy Manager (CHRD) for his outstanding guidance and

extending his support at all times throughout the training period.

I am grateful to all plant In-charges, technicians and other employees of different dept. working under operation, maintenance and instrumentation departments for sharing their valuable experience with me.

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INDEX

S.No CONTENTS Page No.

1 Introduction 04

2 Process Flow chart of Durgapur Steel Plant 06

3 Raw Materials Handling Plant 07

4 Coke Ovens and Coal Chemical 10

5 Sinter Plant 14

6 Blast Furnace 16

7 Steel Melting Shop 19

8 Blooming and Billet Mill 22

9 Skelp Mill 25

10 Merchant Mill 26

11 Section Mill 29

12. Wheel and Axle Plant 32

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INTRODUCTION

Durgapur Steel Plant, SAIL, was set up with the British collaboration in the late fifties with an initial capacity of one million tonnes of crude steel per annum. The capacity was subsequently enhanced to 1.6 million tonnes in the late sixties. The plant undertook a large-scale modernisation programme in the early nineties. The technological upgradation of the plant was matched with a massive training programmes of it’s human resources. Since then DSP has acquired the ISO 9000:2001 Quality Assurance Systems and has emerged as one of the most modern plants in the country. Encouraged with a participative style of management, the Durgapur steel collective has amply demonstrated its determination to forge ahead in the highly competitive market scenario that has emerged over the years.

Initiated during the 1950s, Durgapur Steel Plant changed the face of India, bringing with it a lot of technical and industrial growth for the country as a whole. The plant was set up with an initial annual capacity of one million tonnes of crude steel per year. However, as time progressed, the capacity of Durgapur Steel Plant (DSP) was later expanded to 1.6 million tonnes in the 1970s. Three decades after its commencement, a massive modernization program was undertaken, which brought a number of technological developments in the plant. The yearly capacity of the plant was also increased to 2.088 million tonnes of hot metal, 1.8 million tonnes crude steel and 1.586 million tonnes saleable steel.

The modernized DSP now has state-of –the-art technology for quality steel making. The modernized units have brought about improved productivity, substantial improvement in energy conservation and better quality products. DSP’s Steel Making complex and the entire mills zone, comprising its Blooming & Billet Mill, Merchant Mill, Skelp Mill, Section Mill and Wheel & Axle Plant, are covered under ISO: 9002 quality assurance certification.

Durgapur Steel Plant is the third integrated steel plant of the then Hindustan Steels Limited to come up under Public Sector in India. Durgapur was selected as location of the plant, for its proximity to coal-fields, the Grand Trunk Road (NH-2), Kolkata - Delhi main railway track, Kolkata port, power from Damodar Valley Corporation and water from Durgapur Barrage on river Damodar.

Product Mix Tonnes/annum:

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Finished products of Durgapur Steel Plant are used in various sectors which are mentioned in the table below:

Major Production Units in Durgapur Steel Plant:

Raw Material Handling Plant Coke Ovens and Coal Chemicals Sinter Plant Blast Furnace Steel Melting Shop Blooming & Billet Mill Skelp Mill Merchant Mill Section Mill Wheel and Axle Plant

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RMHP (RAW MATERIALS HANDLING PLANT)

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Raw Material Handling Plant is the starting point of steel making process. The objective of RMHP is to receive, unload, stack and supply all the raw materials required for steel making i.e. Iron ore, Limestone, and Dolomite. Apart from this, RMHP also deals with Sinter mix preparation using state of the art automation system.

Iron ore, coal and limestone are the three most basic raw materials of Durgapur Steel Plant. The plant draws its coal from the Jharia-Raniganj coal belt, while some amount of prime coking coal, with fairly low ash content, is imported as well. The iron ore, on the other hand, is derived from the mines at Bolani, in Orissa. Lime stone comes from the Birmitrapur (Orissa), Jaisalmer (Rajasthan), and Jukehi and Nandwara (Madhya Pradesh). Durgapur Steel Plant consumes a total of about 7.4 million tonnes of different raw materials annually

Main functions of RMHP:

1. Tippling of wagons.

2. Stacking and reclaiming of raw materials.

3. Crushing of flux and coke.

4. Sinter-mix preparation and supply to Sinter Plant

5. Iron ore lump screening.

6. Screened iron ore supply to Blast Furnace.

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7. High grade limestone, dolomite & iron ore lump supply to BOF.

Major Equipments:

(A) Wagon tipplers:

These are 3 in number To unload the raw materials brought in rakes of

wagons from various mines(B) Wing Trippers:

These are 3 in number Two operated mechanically and one hydraulically To stack material on the beds

(C) Old Reclaimers:

These are 4 in number Plough and Harrow type For reclaiming the materials

(D) Stacker cum Reclaimers:

4 in number For stacking on beds as well as reclaiming from beds Two beds for Iron ore and two beds for flux

(E) Slewable Stacker:

1 in number For Sinter-mix preparation (i.e. stacking for Sinter-mix)

(F) Blender Reclaimer:

1 in number To reclaim the Sinter-mix

Major sections:

(1) Sinter-mix preparation: Capacity of 12051 T/day Raw Materials stored in 18 bunkers of junction 25 Also waste generated in the plant like flue dust, mill

scale, Ferro scraps are added Sinter mix is sent to the Sinter Plant

Main constituents of sinter mix:Iron ore fines 0-10 mmLimestone fines 0-3mmDolomite fines 0-3mmCoke fines 0-3mm

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Flux Crushing Plant:

6 Impact hammer type crusher to crush Limestone and Dolomite

3 Primary Crushers of 200 TPH and 3 Secondary Crushers of 250 TPH

Required size of –3 mm obtained by closed loop crushing system

Crushed Limestone and Dolomite conveyed to sinter-mix proportioning bunkers.

(2) Coke Crushing Plant: 6 Smooth Roll Crushers to crush the coke Coke breeze offloaded at track hoppers is reclaimed by

two paddle feeders and conveyed to storage bunkers Coke crushed to –3 mm and conveyed to sinter-mix

proportioning bunkers.

There are 8 dust extraction system and 8 dust suppression system for pollution control.

Sources of raw materials

Raw Material Size (in mm) Main Source

Iron ore fines 0-10 Bolani

Iron ore lump 10-50 Bolani

BF/SP gr. L.S 5-50 Birimitrapur

BF/SP gr. dolo 5-50Birimitrapur

BOF gr. L.S 25-55 Jaisalmer

Coke breeze 0-20 Internal

COCC (COKE OVENS & COAL CHEMICALS)

Coke Ovens is an important department in an integrated steel plant. The main objective of this department is to produce coke by carbonization of coal. Coke is an essential raw material for production of Hot Metal.

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Fig. of battery of Coke ovens

The ovens are charged using charging cars. The charge is heated inside in the ovens in the absence of air up to the temperature of 1000 – 1050 degrees. This process generally takes 16-19 hrs which is called coking period. After the coking period, coke produced is pushed out of the oven into coke bucket after which is taken to dry.During the process of carbonization of coal, a number of valuable chemicals are obtained. This department also deals with the recovery and processing of these chemicals.

Major sections of this department are:

1. Coal Handling

2. Coal washery

3. Coke Oven Battery and Coke Handling

4. Coal Chemicals

Input – Output Model:

Washed Coal

(-25 mm)

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Wagon Tipplers

Wing Tripper

Bed Reclimererners

Blending Silos

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Selective Crushing

Unit

To Battery

Major Sections:

(1) Coal Handling: To supply coal of required quality and quantity to service

bunkers for BF coke making Washed coal and imported coal received in wagons are

unloaded by means of Box Tipplers (3) The tippled coal is stacked in silos (14) as per quality

and grade Coal of different quantity is drawn from Blending silos

and selectively crushed and blended in Selective Crushing Unit.

Blended coal is sent to service bunkers for BF coke making.

(2) Coke Ovens Battery: There were 5 batteries of 78 ovens each and a half

battery of 39 ovens Now we have 3 batteries of 78 ovens each and a half

battery of 39 ovens Capacity of oven is 16.6 tonnes on dry basis

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Primary Crusher

Pneumatic Classifier

Secondary Crusher

Service Bunkers 4 of 4000T each

Coal for BF coke making

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Coking time 18 to 20 hours Flue temperature 1230o C Coke of size 20 to 80 mm is sent to BF, undersize coke is

sent to RMHP.

There are four special cars in this section:

(a) Charging Car: Takes coal from service bunkers to individual ovens

(b) Ram Car: Pushes the coke out of individual ovens

(c) Guide Car: Guides the coke during pushing operation

(d) Quenching Car: Receives the hot coke for quenching

The quality parameters of cleaned coal are:

Blend coal ash 15%

Ash in BF coke 19%

Fineness of crushing -3 mm (85%)

(3) Coal Chemicals Plant: By–product plant which recovers the chemicals from the

gas and allows clean gas to be used in coke ovens and other plant as fuel.

4 gas streams with capacity of 3300 cube meter/Hr each

This plant has four major sections:

(a) Benzol Plant(b)Tar distillation(c) MNCP(d) BOD plant

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Properties / Requirement of Coke for BF use:

• As fuel

• As reducing agent

• Must have high mechanical strength

• Must be in required size range

SINTER PLANT

Sintering is the process of agglomeration of fines by incipient fusion caused by heat available from the fuel contained in the charge. The objective of sinter plant is to provide good quality sinter, an efficient feed to Blast Furnace.

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The process of sintering started in 1940 and flourished in countries where there was coke shortage. Advantages of using sinter are:

(a) To utilize all waste of fines nature like Mill scale, Ferro Scrap, LD slag etc.

(b) Reduction in coke rate in Blast Furnace

(c) Increase productivity of blast furnace

(d) Smooth Gas Dynamics inside BF stack.

(e) To utilize Iron Ore fines and Coke breeze.

(f) Better Operation of Blast Furnaces as Sinter is engineered product

Input output model:

Plant capacity: 3.009 MT/annum

Machine capacity: - 2500 T/day (for each old m/c)

5184 T/day (for the new machine)

In DSP, there are 3 sintering machines whose details are as follows:

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Major equipments:

(a) Primary Mixing Drum: Materials are mixed in required proportions and

calculated amount of moisture added Drum fitted with paddles

(b) Nodulizing Drum:

Moist charge is rolled to nodulise the fines and decrease the size range of particles and consequently improve the permeability of sinter bed.

(c) Sinter mix Hopper:

To store the nodules before feeding to sintering machine

(d) Sintering machine:

Sinter mix is spread over hearth layer, which is a layer of previously sintered material.

Material is heated under a set of burners and suction is applied from bottom.

The heat travels down the bed and by the time the material reaches the discharge end, whole mass is sintered.

(e) Sinter Breaker:

Sinter is crushed here and passed through screens.

Various fractions of sinter are used as follows:

+25mm and +6 to -16mm Blast furnace

+16 to -16mm Hearth layer

-6mm Return fines re-circulated in sinter plant

-5mm Returns fines to RMHP

Sinter plant is a Heavy Power consuming plant and it consumes about 1/4 th of the total power.

There are 4 ESPs (Electrostatic Precipitators) provided for each machine which perform the process of cleaning the gases obtained during suction. These are vital as the gases have lot of dust particles.

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BLAST FURNACE

Blast Furnace is the most important part of an integrated steel plant. It is considered as the heart of an ISP. The objective of Blast Furnace is to take the raw material from RMHP, coke from Coke Ovens and Sinter from Sinter Plant and convert it into pig iron or ”Hot Metal”. Coke serves as the heat source and reducing agent while Limestone and Dolomite are used as flux, which combines with gangue to produce slag. A Blast Furnace is so called because it uses air blast as oxygen source for the process. The solid charging materials like sinter,sized iron ore,coke etc. are charged form the top of the furnace.The hot air blast at 11000c-13000c and 5.75 kg/cm 2 is blown from the tuyeres located at the bottom of the furnace.The oxygen from the air blast reacts with the coke and generates heat and carbin monoxide.These gases while ascending upwards reacts with the coke and generates heat and carbon monoxide.These gases while ascending upwards reacts with the descending charge materials.Eventually the charge melts and hot metal and slag are produced and tapped out.The top gases are collected and refined and used for preheating the blast.

Fig. Outer view of Blast furnace

There are four Blast Furnaces in DSP, out of which 3 are in running condition.

At present in Durgapur Steel Plant there are four Blast Furnaces of which the details are as following:

1. Kasturba 1323cu m. 1250 T/day

2. Kamala 1400 cu m. 1870 T/Day

3. Sharada 1400 cu m. 1820 T/Day

4. Durga 1800 cu m. 2340 T/Day

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Input – Output Model:

Sinter Iron ore lump

Coke

Hot Blast Hot Blas BF Gas Clean BF

Gas

Hot metal

Slag

Process:

Raw materials i.e. iron ore, Sinter and coke are charged into the furnace from top in required proportions. Air enriched with oxygen is preheated in stoves. Preheated air is blown through Tuyeres in the bosh region. These are symmetrically located openings. The raw material descending through various temperature zones are heated up and get smelted. The reducing gases rise up and go out through ascension pipes. The hot metal and slag obtained through smelting of raw materials trickle down and accumulate in the hearth, which is the bottom part of the furnace. The slag, being lighter than Hot Metal, floats on it.

The hot metal and slag are tapped through Tap Holes, drilled using drilling machines. The hot metal thus obtained is sent to SMS to make steel or to PCM to make pigs. The slag is either dumped in the slag yard or granulated in slag granulation plant (SGP).

Blast Furnace 3 and 4 have SGP and hence the slag coming out of these Furnaces is granulated.

The gas ascending through the descending column is called BF gas and has high calorific value of 850 Kcal/Nm3. It is used as fuel at many departments in the plant. This gas has to be cleaned before being used as fuel. For this purpose, a gas cleaning plant is located in the Blast Furnace area.

Gas Cleaning Plant:

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Blast Furnace GCP

SMS

PCM

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The gas coming out of Blast Furnace contains about 25-27 gm/Nm3 of dust and unless it is cleaned, it cannot be used as fuel. The cleaning process is done in four stages. In the first stage, the gas is subjected to a sudden expansion in primary dust catcher. Then, it is given a cyclonic motion in a secondary dust catcher. The gas coming out at this stage has about 5-7 gm/Nm3 of dust.

In the third stage, the gas is counter currently washed with water in gas washer. The gas coming out is then sent into a set of electrostatic precipitators, where it is cleaned to the maximum extent. The gas leaving ESP’s has a dust content of 9-11 mg/Nm3

Details of Furnaces:

#1* #2 #3 #4

Capacity (TPD) 1250 1820 1820 2340

Useful volume (m3) 1323 1400 1400 1800

No. of stoves 3 3 3 3

*not working

Design parameters:

Parameter BF #2 & 3 BF # 4

Blast Temperature 1100 c 1150 c

High top pressure 0.7kg/cm2 0.7kg/cm2

Sinter charge 75% 75%

Furnace Productivity 1.3 1.3

No. of cast/day 9-10 9-10

No. of tuyers 18 20

No. of tap holes 2 2

Blast period 60 minutes 60 minutes

SMS (STEEL MELTING SHOP)

SMS or Steel Melting Shop is the section where hot metal from Blast furnace is converted into steel. The process is Basic Oxygen Furnace or LD process.

This process was first used successfully in a place called Linz in Austria and then at Donawitz in Austria. The name LD process came from the names of these places.

Basic Oxygen Furnace was added under modernization of DSP. It has a capacity of 1.876 MTPA.

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SMS can be divided into 3 sections:

(a) Basic Oxygen Furnace

(b) Continuous Casting Plant

(c) New Lime Calcination Plant

Basic Oxygen Furnace:

Hot Metal coming out of the Blast Furnace is collected in ladles and poured into mixers. The mixers (2) serve the purpose of storing as well as homogenization of temperature and composition. Coke oven gas is used here to maintain the temperature at 1260o C. the quantity of raw materials for producing one tonne of steel are as follows:

Hot Metal 1073 kg

Scrap 65.9 kg

Iron Ore 15.6 kg

Briquetted lime 10.6 kg

Calcined Lime 81.3 kg

Dolomite 31.3 kg

Fe- Mn 1.11 kg

Fe- Si 1.32 kg

Al 0.15 kg

Coke Breeze 3.27 kg

The shop has three converters each having a capacity of 110-130T per heat. The converters were commissioned by Mannessmann Demag of Germany. Each converter has its own lance system for blowing oxygen at high pressure so as to form an emulsion on the surface of metal which increases the surface area to such an extent that separation of impurities takes place very fast.

The oxygen blowing rate through the lance is 415 Nm3/min. and the blowing pressure is 14.2 to 14.3 bars from top. The tap to tap time of BOF is approximately 57 minutes out of which oxygen blowing time is 18 min. the gas obtained from BOF converter has a calorific value of 2100 Kcal/Nm3 which acts as a fuel.

BOF has an online process monitoring system. The system uses VAX/VMS system which works on the principle of virtual memory. The higher level of computerization caters to the need of quick retrieval of data about operation parameters.

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(ii) Continuous Casting Plant:

CCP, one of the critical features of DSP is the first billet caster in any ISP in SAIL. The machines are designed and supplied by Concast Standard AG, Switzerland. Presently, we have two machines with six strands in each, capable of producing billets of sizes varying from 80 mm2 to 150 mm2.

Under traditional route, liquid steel is allowed to solidify into separate moulds and come out as ingots, which are then rolled to get the billets. Continuous casting route bypasses the steps of soaking and rolling in blooming and billet mill.

Technical Features of CCP:

No. of machines 2

No. of strands/machines 6

Design Limit 80 -150 mm2

Casting Radius 6m

Heat Size 110T (normal), 130T (max)

Casting time 85 min.

Shear Up cut pendulum type

Molten steel is taken to ladle treatment section. The purpose of ladle treatment is to homogenize the temperature and composition, floatation of non-metallic inclusions and to facilitate active slag metal reactions. A dummy bar is inserted in the mould, up to 100 mm with the help of pinch rolls. The mould is surrounded by 4 mm water jackets through which primary water is circulated internally. Primary cooling is thus done by demineralized water. Other zones are kept cool by industrial water.

The billets formed are cut to proper lengths and are allowed to cool in air and then packed and sent to stock yard.

(iii) NLCP (New Lime Calcination Plant):

NLCP came up during during modernization in 94-95. This plant came up to cater to the need of BOF. The main function of this plant is to produce lime from naturally available limestone. Lime is mainly required in steel making process to reduce sulphur and phosphorous content of steel. Presently, Limestone from Jaisalmer is used as input material for the plant.

There are three kilns (Annular kiln shaped), of capacity 300T/day , one is kept standby, each kiln is a vertical cylindrical structure. Limestone, which is charged from the top, gradually descends through the kiln, where it is subjected to controlled heating by two firing zones preventing the charge from direct exposure to base flame. Coke oven

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gas at 5500 mm water pressure is used as fuel for heating. Temperature range of heating is 12000 C - 1250o C

The calcination process is almost complete as the charge reaches the bottom portion of lower combustion zone and the calcined lime is discharged into a silo by Lime Discharging device.

NLCP has got bunkers and conveyors for storage, handling and supply of fluxes to converter shop.

ROLLING MILLS

The process of plastically deforming metal by passing it between rolls is known as rolling.

TYPES OF MILLS:-

A. PRIMARY MILLS Blooming & Billet Mill

B. FINISHING MILLS Section mill Skelp mill Merchant mill Wheel and axle plant

Semi Finished products of DSP Blooms:160 to 250x250 mm Billets:125x125 mm,100x100 mm Slabs:140 to 225x80 mm Ingots: fluted ingots, 8T ingot

BBM (BLOOMING & BILLET MILL)

Blooming and Billet Mill is the place where the Ingots are produced at the SMS are released (called soaking) and then rolled into different square sections called Blooms (section above 125x125mm) and Billets (sections upto 125x125mm). Slabs are also rolled here for use by skelp mill. Blooms and Billets are sold outside. Some blooms are used in the section mills and Wheel and Axle plant; billets of 100x100 mm are used in Merchant Mill.

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Process:-Soaking pit furnaces are used for reheating the ingots at 1280o C. There are 20 soaking pit furnaces with capacity 110T. Fuel used is CO and BF gases in the ratio of 1:4. The reheating time is usually 1.5 times the Track Time. After soaking the ingots are lifted by means of vertical ingot charger cranes for soaking. It is a two high charger reversible type with two 2X3000 HP DC motors at the mills speed of 0/40/60 rpm. Here 1200T shear is used to cut fish tail, and then the blooms are put in the bloom transfer bank.There is a two high reversible mill driven by 4500HP DC motor. The rolls are spring balanced and driven with a speed of 0/80/120 rpm.

Major Equipments:

Blooming mill

Soaking Pits:

20 in numbers and of 3 types

Welman type - Bottom fired with ceramic recuperators

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Ofulyns type - side fired with ceramic recuperators

Priest type - side fired with ceramic recuperators

(a) 42” Blooming Mill

2- high reversing type with twin motor drive

Driven by two 3000 HP DC motors

Speeds of 0/40/60 rpm

Roll diameters varies from 915 mm to 1100 mm, top roll hydraulically balanced and can be moved up and down, while bottom roll is fixed

Side guard type manipulators to guide the ingot through various passes

Generally rolled in 13 passes (19 passes required for special steel).

(b) Primary Hot Bloom Shearing & Stocking:

Front and back ends of blooms which develop fish tails are sheared using1200T shear

Shear can cut a max. cross section of 256 square inch.

(C) 32” Intermediate Mill:

2 high reversing mill driven by one 4500 HP DC motor

Roll diameter varies from 800 mm to 925 mm

Springs balanced rolls

Speed range of 0/80/120rpm

(d) 700 T Shear:

Blooms are cut to length with nominal blade load of 700 T

Important Parameters:

(a) Pit Time: This is the amount of time the ingots have to be placed in the soaking pits. This is equal to 1.5 times the track time, which is around 3 to 4.5 hrs for hot ingots and around 12 hrs for cold ingots.

(b) No. of passes in blooming mill:

13, in case of normal steel and 19, in case of special steel.

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Billet Mill

Blooms produced in Blooming Mill are further rolled into billets of various sizes. The capacity of Billet Mill is 0.957 tonne per annum. The products of this mill are 50 mm square to 125 mm square Billets and 140 to 240 mm * 75/80 mm skelp slabs.

Fig of Billet production

Major Equipments:

(a) Mill Train:

Continuous morgan design with 8 strands

Vertical rolls on first and fourth strands & remaining are horizontal, 1 to 4 are roughing stands each run by 800 HP DC motor (1 & 2) and 1000 HP DC motor (3 &4)

5 to 8 (finishing stands) driven by a single 700 HP synchronous motor

(b) Up and Down Cut Shear:

For emergency purpose

(c) Flying Shear:

Cuts materials in process. (maximum capacity 130 square inch)

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SKELP MILL

Skelp mill came up during the expansion of plant to 1.6 MTPA in late 60’s. It was designed and elected by a UK firm, Loewy Robertson Company Limited. Skelp is a narrow section with bevel edge with included angle of 70o. Mostly used for making pipes and tubes. The annual capacity of this mill is 0.25 million tonnes.

Input Output model:

Process:-

Skelp mill receives slabs from Billet Mill by rail transfer bogies. The slabs are taken on to charging table from the bogie. The slabs are fed to a reheating furnace by a Ram charger. The furnace is of side charge and side charging type. The furnace is fired by a mixture of coke oven and Blast Furnace gas in a ratio of 1:1.

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The furnace has a heating capacity of 60T/Hr. The slabs are sent to the mill section, which consists of 11 horizontal strands and 6 vertical strands. These are arranged as shown below:

E1-H1-H2-H3-H4-H5-E3-H6-COBBLE SHEAR-LOOPING THROUGH-H7-E4-H8-H9-E5-H10-E6-H11.

Where H refers to horizontal strands and E refers to vertical strands. The roughing mill constitutes strands from E1 to H6 while H7 to H 11 constitute the finishing mill.

After rolling, the skelp or strip is coiled and the coil is dispatched to customers.

MERCHANT MILL

Merchant Mill takes billets of size 100 mm2 from CCP and produces ribbed TMT bars of various diameters.

The capacity of Merchant Mill is 0.28 million tone per annum thermo mechanically treated (TMT) ribbed bars of dia. 16, 18, 20, 22, 25, 28 mm.

Grade- IS2062

TMT 415, TMT 500, TMT 550, TMT HCRM

Input: billet of 100mm2 and 9m long

Fig of TMT rods

Input – Output Model:

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Process:-

Reheating furnace has a two zone type arrangements for side charging and discharging. The output of furnace is 70 TPH. Temperature inside the furnace is 1250 –1300o C. Separating skids are used to placed the billets on the furnace charging table. The mechanism consists of stationary and power operated carry over skids .The fuel used is CO gas with 3000 BTU/ft3 of calorific value. The air for combustion is preheated in metallic recuperators.

By using push-out bar, billets are discharged from the furnace to the first mill stand. For this, there is a pinch roll arrangement near the furnace. A pendulum shear is located between the pinch roll and first stand to cut the front end of the billets.

The mill has 13 horizontal stands in which 7 are roughing, 4 intermediate and 2 are finishing stands. In between 7 & 8 stand, a crop cum cobble shear is provided to cut front end of all the rolled stocks passing out of the 7 th stand. It is also used for cutting the rolled stock into pieces in case cobble is formed.

Four 180° repeaters provided between 9 & 14 stands (13th stand is not there). These repeaters are provided to reduce the overall length of the mill.

After the finishing mills Thermax carriages are situated for spraying water at high pressure on the rolled bars (to impart required structure). There is a rotary shear, which

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cuts the rod into the pre determined lengths, which are then accommodated in the cooling beds. After this the bars are cut to final sizes (as per customer’s demand) in the Bar Shears and sent to dispatch area after bundling and strapping.

Apart from conventional rolling, Slit Rolling is also done where we get two rods parallel from a single billet. (for section 16 mm rolling)

Major Equipments:

Reheating furnaces:

Two–zone type arranged for charging and discharging

Capacity 70 TPH

CO gas of calorific value 3000 BTU/cu ft as fuel

Air preheated in metallic recuperators

(a) Pinch Rolls:

To pull out and feed billets into the first mill stand

Pendulum Shear:To cut the front end of billets

(b) Mill:

Continuous Morgan design with 4 repeaters

13 horizontal stands (1 to 7 Roughing Stands, 8 to 11 are Intermediate Stands and 12 to 13 are Finishing Stands)

Stand no. Drive

3, 4 & 5 400 HP DC motor

1 & 2, 6 to 9 500 HP DC motor

10 & 11 600HP DC motor

12 & 14 800 HP DC motor

(c) Crop cum Cobble Shear:

To cut front ends of rolled stock passing out of 7th stand.

Also used for cutting the rolled stock in case cobble is formed in intermediate and finishing mill.

(d) Repeaters:

Four 180o repeaters between 9 and 14 stands.

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Provided to reduce the overall length of the mill.

(e) Thermax Carriages:

3 in number

Sprays water at high pressure on the rolled bars. Finished rod receives intense cooling, resulting in formation of a martensite structure surrounding the ferrite-particle core.

(f) Rotary Shear:

To cut rods into predetermined lengths

(g) Bar Shear:

To cut rods into specified lengths as desired by customers

SECTION MILL

Blooms from blooming mill are taken and rolled in section mill to produce light and medium structural like Joists, Channels and Angles. The capacity of Section Mill is 0.212 million tone per annum.

Input – Output Model:

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Input -Blooms

Products:

Joists 200x100mm, 175x85mm, 150x75mm, 116x100mm

Channels 200x75mm, 175x75mm, 150x75mm, 125x65mm

Angles 150x150mm, 130x130mm, 110x110mm, 100x100mm

Major Equipments:

(a) Reheating Furnace:

2 continuous end charge end discharge type with11 burners each ,CO gas mixed with BF gas used as fuel

(b) Roughing Mill stands:

Rolls of 26” diameter and 72” barrel length,

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Two-high reversing, closed top type, driven by a 2500 HP DC motor at 90/120 rpm

Spring balanced top roll with a lift of 12”

Bobbin type gear is provided on the heads on the ingoing side.

(c) Intermediate Mill Stands:

2 stands of 24”x68”

Three-high non reversing open top housing type

Driven by a single 3000 HP DC motor at 0/90/120 rpm.

(d) Finishing Mill Stands:

24”x48” two- high non- reversing, open top housing type.

Driven by 1000 HP DC motor at 0/360/600rpm.

(e) Finishing End:

2 Hot Saws after the Finishing Stand.

(f) Straightening Machine:

3 cold straightening machines (two m/c having 3 rolls on the top & 4 at the bottom)

Bottom rolls driven by 165 HP motor and Top rolls are friction driven

Third machine driven by two 100 KW slip ring Induction motors having 4 top rolls and 3 bottom rolls.

WHEEL & AXLE PLANT

Wheel and Axle plant special feature of Durgapur Steel Plant. It is the only plant in public sector which produces wheel sets. The main customer of wheel sets is Indian Railways. This was commissioned in 1962 with a capacity to produce 45000 sets per year and subsequently raised to 76000 sets per year.

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The present capacity is as follows:

Wheels: 42000 tonnes/annum

Axles: 16000 tonnes/annum

Input:- Round ingot,12 sided fluted ingot of diameter 16” & 14”

Fig. of Wheel and axle

In Wheel and Axle plant of Durgapur Steel Plant, wheels are produced by pressing and rolling while axles are produced by forging. Subsequently both are heat treated and machined. For the ease of production, wheel manufacturing section and axle manufacturing sections are located in two different bays. Tested wheel and tested axles finally meet in assembly section. The existing wheel plant at Durgapur Steel Plant is sourced with bottom poured cast ingots from existing ingot casting facility of the plant for the production of wheels for locos and coaches.

The raw material for wheel is 12 side fluted bottom poured steel ingot of diameter 16”-14”.Below is a figure of ingot.

Input Output Model:

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Process:

This can be divided into two sections:.

(i) Process of wheel making:The 12 sided fluted ingots are sliced into number of blocks called cheese. After

physical inspection, blocks are heated in rotary hearth furnace for 6-8 hours to a temperature of 1220 o C.

The heated cheeses are descaled and fed to 63/12 MN forging & punching combination press. The block is subjected to upsetting, open die forging and punching. After this, wheel blanks are heated in batch type holding furnace to 1150o C. The wheel is then rolled in a computerized wheel mill, where shaping of tread profile by a tread roll, shaping of web portion by two web rolls and control of rim thickness by two edge rolls is performed. After rolling, the wheels are fed to a 20 MN Dishing press, where the form of the web is charged from flat ring to that of a truncated cone sloping from boss to rim. This prevents high internal stress during cooling and prevents warping of wheels. The wheel is then feed to a marking press of 3 MN, where Sl. No., Year and Cast No. are stamped on the back rim. The wheel is then subjected to heat treatment which includes quenching and tempering to give hard rim and tough core. Next comes the machining part, where rim face, boss face, rim blending, condemning glove, chucking glove are machined by means of CNC machines.

Finally, the wheels are subjected to strength testing in the form of Ultrasonic Test, Magnetic particle Test which are RITES certified.Process of axle making:

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Square bloom from blooming mill made of killed steel is the raw material for axle. These blooms are heated for 6-8 hours in continuous pusher type furnace after inspection. Blooms are forged in a 7 tonnes hand operated axle forging hammer. The process takes around 9-10 minutes and the finishing temperature is 850o C. It is then air-cooled.

Ultrasonic test is carried out, checking physical roundness of every axle is done. Axle is then sawed and is first rough turned and then finish turned.

The axles are inspected for dimensional accuracy at every stage of the process and for surface & diameter defects after completion.

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