Internship Report

PEOPLES STEEL MILLS LIMITED

Prepared by:

Names Roll Number

Dawood College of Engineering & Technology Degree Awarding Institute, Karachi.

DEPARTMENT OF METALLURGY & MATERIALS ENGINEERING

(Final year students.)

Table of Contents

Dedication Acknowledgments

Chapter#1 Introduction

Chapter#2 Process Flow Diagram

Chapter#3 Melting Shop (M-Shop)

Chapter#4 Bar Rolling Mill (Q-Shop)

Chapter#5 Slab & Bloom Rolling Mill (N-Shop)

Chapter#6 Forging Shop (R1,R2 & R3 Shop)

Chapter#1 INTRODUCTION

Peoples Steel Mills Ltd, a world class alloy and special steel manufacturing plant

located in Manghopir, Karachi Pakistan and spread over an area of 100 acres was

set-up by the Government of Pakistan in 1975 with Japanese assistance.

In order to keep pace with emerging technologies, the plant was upgraded in 1996

though a comprehensive balancing & modernization programs with the technical

assistance of  VAIS, INTECO and Bohler of Austria. The plant is now equipped

with modern melting, refining, degassing, electro slag re-melting and necessary

casting , rolling and forging facilities with an annual capacity of 70,000mt. Products

quality is assured through modern material testing facilities and well trained staff

The plant has the capability to produce steels according to all major international

quality standards and to date has manufactured more than 300 steel grades.

Peoples Steel enjoys the highest market share in the alloy and special steel market of

Pakistan. A diversified base of more than 200 customers includes high profile

illustrious end users in automotive, defense, machinery construction, special/high

rise buildings, transportation and engineering sectors in Pakistan. Components

manufactured from our steel are supplied by our customers to renowned European &

Japanese automobile manufactures.

In addition to manufacturing & supply of quality steels Peoples Steel is extending

it’s expertise in the following fields:

Material Testing & Analyzing-Chemical, Mechanical, NDT, Metallographic,

Failure Analysis.

Industrial Project & Services-Plant Fabrication & Installation.Seamless Pipe

Manufacturing–Pipe/Tubes up to 300mm diameter are expected to be available in

near future.

Chapter#2 PROCESS

FLOW

Chapter#3 ELECTRIC ARC FURNACE

The melting shop of PSM consists of following facilities:

Electric arc furnace.

Ladle furnaces

Ladle Vacuum Degassing Unit.

Electro Slag Re-melting furnace.

Continuous Casting Machine.

The brief processing and configuration of above processing unites is as follows:

3.0 Electric Arc Furnace:

In PSM there are two EAF in M- shop. The basic purpose of EAF is to melt the Steel

Scrape and provide oxidizing environment to remove phosphorous contents

(Dephosphorization).The electric arc furnace operates as a batch melting process

producing batches of molten steel known "heats".

3.0.1 Operation of an Electric Arc Furnace:

The electric arc furnace operating cycle is called the tap-to-tap cycle and is made up

of the following operations:

Furnace charging;

Melting;

Basic slag formation;

Tapping the steel;

Killing of steel( Deoxidation).

Refractory lining maintenance.

i. Furnace Charging:

The first step in the production of any heat is to select the grade of steel to be made.

Usually a schedule is developed prior to each production shift. Thus the melter will

know in advance the schedule for his shift. The scrap yard operator will prepare

buckets of scrap according to the needs of the melter. Preparation of the charge

bucket is an important operation, not only to ensure proper melt-in chemistry but

also to ensure good melting conditions. The scrap must be layered in the bucket

Chapter#3 ELECTRIC ARC FURNACE

according to size and density to promote the rapid formation of a liquid pool of steel

in the hearth while providing protection for the sidewalls and roof from electric arc

radiation.

Following is the classification of Steel Scrap used:

Home Scrape/ Shop returns:

Ferritic Stainless Steel

Maragin Steel

Tool Steel

Special alloy steel

Purchased Scrape:

Heavy mill Scrap 1 & 2

Sheratted Scrape

The total time of charging is 45min. In PSM Scrap yard there are 8 buckets of

different size ranges.

ii. Charge Melting: The EAF has evolved into a highly efficient melting apparatus and modern designs

are focused on maximizing the melting capacity of the EAF. Melting is

accomplished by supplying energy to the furnace interior. This energy can be

electrical or chemical.

Electrical energy is supplied via the graphite electrodes and is usually the largest

contributor in melting operations. Initially, an intermediate voltage tap is selected

until the electrodes bore into the scrap. Usually, light scrap is placed on top of the

charge to accelerate bore-in. Approximately 15 % of the scrap is melted during the

initial bore-in period. After a few minutes, the electrodes will have penetrated the

scrap sufficiently so that a long arc (high voltage) tap can be used without fear of

radiation damage to the roof. The long arc maximizes the transfer of power to the

scrap and a liquid pool of metal will form in the furnace hearth At the start of

melting the arc is erratic and unstable. Wide swings in current are observed

accompanied by rapid movement of the electrodes. As the furnace atmosphere

Chapter#3 ELECTRIC ARC FURNACE

heats up the arc stabilizes and once the molten pool is formed, the arc becomes

quite stable and the average power input increases.

Chemical energy is be supplied via several sources including oxy-fuel burners and

oxygen lances. Oxy-fuel burners burn natural gas using oxygen or a blend of

oxygen and air. Heat is transferred to the scrap by flame radiation and convection

by the hot products of combustion. Heat is transferred within the scrap by

conduction. Large pieces of scrap take longer to melt into the bath than smaller

pieces. In some operations, oxygen is injected via a consumable pipe lance to "cut"

the scrap. The oxygen reacts with the hot scrap and burns iron to produce intense

heat for cutting the scrap.

Oxidation of C, P, Mn, Si, Al:Once a molten pool of steel is generated in the

furnace, oxygen can be lanced directly into the bath. This oxygen will react with

several components in the bath including, aluminum, silicon, manganese,

phosphorus, carbon and iron. All of these reactions are exothermic (i.e. they

generate heat) and supply additional energy to aid in the melting of the scrap.

Oxidizing slag formation: The metallic oxides that are formed will end up in the

slag. Once enough scrap has been melted to accommodate the second charge, the

charging process is repeated. Once the final scrap charge is melted, the furnace

sidewalls are exposed to intense radiation from the arc. As a result, the voltage

must be reduced. Alternatively, creation of a foamy slag will allow the arc to be

buried and will protect the furnace shell. In addition, a greater amount of energy

will be retained in the slag and is transferred to the bath resulting in greater energy

efficiency.

Sampling and chemical analysis of the melt: Once the final scrap charge is fully

melted, flat bath conditions are reached. At this point, a bath temperature and

sample will be taken. The analysis of the bath chemistry will allow the melter to

determine the amount of oxygen to be blown during refining.

De-slagging: When sufficient amount of phosphrous has been oxidized and gone

in to slag the slage is removed.

iii. Basic slag formation: Basic slag is then formed by addition of flux and blowing of oxygen. The purpose of

this basic slage formation is that the furnace is taped at 17000C at this temperature

Chapter#3 ELECTRIC ARC FURNACE

P2O5 ,which has penetrated in to refractories and remaining in the melt, decomposes

resulting in increase in percentage of Phosphorous. But due to the formation of basic

slag this effect is prevented.

iv. Tapping the steel:When steel has got aimed( average of upper and lower limits) composition and

temperature Steel is tapped in preheated ladles by tilting slowly at an angle of 450.

v. Killing of steel( Deoxidation):During the tapping the steel is killed by using deoxidizers. Which include

Ferrosilicon, Ferromanganese, Ferrochrome, Aluminum & Silicomanganese. The

addition of these oxidizing agents is based on the composition of melt and cost. The

basic purpose of killing of steel is to maintain oxygen content from 100 ppm to 200

ppm.

3.0.2 Chemistry of process: At this stage excessive carbon, phosphorous, silicon and manganese oxidize. The

process is similar to that in Basic Oxygen Furnace. Basic oxidizing slag composed of

lime (CaO) and ion ore (FeO) is used during the oxidizing period. Gaseous oxygen is

blown into the melt for additional oxidizing and to stabilize the arc. Iron oxide

causes increase of Oxygen content in the molten steel according to the reaction:

(square brackets [ ] - signify solution in steel, round brackets ( ) - in slag, curly

brackets {} - in gas).

(FeO) = [Fe] + [O]

Oxygen dissolved in the melt oxidizes carbon, phosphorous, silicon and manganese:

[C] + [O] = {CO}

[Si] + {O2} = (SiO2)

[Mn] + 1/2{O2} = (MnO)

2[P] + 5/2{O2} = (P2O5)

Carbon monoxide partially burns in the atmosphere:

Chapter#3 ELECTRIC ARC FURNACE

{CO} + {O2} = {CO2}

The formed oxides are absorbed by the slag. CO bubbles floating up through the

melt result in refining of the steel from non-metallic inclusions and hydrogen

removal.

Gaseous products CO and CO2 are removed by the exhausting system. Oxidizing

potential of the atmosphere is characterized by the post-combustion ratio:

{CO2}/({CO2}+{CO}).

The oxidizing slag enriched with phosphorous and other oxides formed during this

period is removed from the furnace to a slag pot (de-slagging).

3.0.3 Refractory lining of an Electric Arc Furnace

Refractory linings of Electric Arc Furnaces are made generally of resin-bonded

magnesia-carbon bricks. Fused magnesite grains and flake graphite are used as raw

materials. When the bricks are heated the bonding material is cocked and turns into a

carbon network binding the refractory grains, preventing wetting by the slag and

protecting the lining the from erosion and chemical attack of the molten metal and

slag. During the process if rammed magnasite layer is eroded then process known as

gunning is applied to protect the lining.

3.0.4 EAF Configuration:Following is the configuration of electric arc furnace of PSM:

Furnace Capacity 16 tons

Electrode Consumption 3 Kg/ton

Power 5 MW

Oxygen Lance Pressure 2 bar

Carbon Electrode Diameter 12”

Furnace Efficiency 90%

Current 13000 amp

Voltage 400+

Taping Time 2 hr

Flux addition 2.5% of charge

Tapping temperature 17000C

Chapter#3 ELECTRIC ARC FURNACE

3.0.5 Addition:Following are the formulas used to calculate the amount of alloy addition during the

process:

Amount of alloying Element (Kg)= Aimed % of el ement−Analyzed %of Element%Yeild of Element∈ Additive

x Tonage

%age of alloying Element=amount of alloying element (Kg)

Tonagex%Yeild of Element ∈Additive

CHAPTER#3 LADLE FURNACE

Ladle furnace refining is the secondary reefing process. The purposes of secondary

refining are many:

Temperature homogenization and adjustment

Chemical adjustments for carbon, sulfur, phosphorus, oxygen

Precise alloying,

Inclusion control,

Degassing

3.1 Ladle FurnaceIn PSM there are two ladle furnaces in melting shop. In PSM the ladle furnace

operation is used to perform desulfurization. It is possible to remove sulfur at EAF

but the temperature of desulfurization is high enough that at this temperature

phosphorus reverse reaction stars. Therefore desulfurization is performed at LF. To

perform it a reducing slag is formed by the addition of CaO. The temperature of

molten steel is rase using electric arc similar to EAF. A porous plug; at the bottom of

ladle; is to provide nitrogen gas for stirring of the molten metal to promote

homogenization. Nitrogen is purged at 2bar .The ladle roof is typically a water-

cooled design with a refractory center or delta section and is configured to

coordinate with existing ladles such that the roof will completely cover the top

portion of the ladle when in the operating (i.e. fully lowered) position.

3.1.1 Process Chemistry:The most popular method of desulfurization is removal of sulfur from molten steel to

the basic reducing slag. Basic slag is a slag containing mainly basic

oxides: CaO, MgO, MnO, FeO. A typical basic slag consists of 35-60% CaO +

MgO, 10-25% FeO, 15-30% SiO2, 5-20% MnO. Transition of sulfur from steel to

slag may be presented by the chemical equation:

[S] + (CaO) = (CaS) + [O]

3.1.2 Alloy Addition:Following are the formulas used to calculate the amount of alloy addition during the

process:

CHAPTER#3 LADLE FURNACE

Amount of alloying Element (Kg)= Aimed % of element−Analyzed % of Element%Yeild of Element∈ Additive

x Tonage

%age of alloying Element=amount of alloying element (Kg)

Tonagex%Yeild of E lement∈Additive

3.1.3 Ladle Furnace Configuration:

Transformer 5MVA

Electrode Diameter 8 inches

Voltage 80-130V

Amperage 400-5000 Amp

Power Consumption 2500 KWH

Refining Time 90 min

Heat capacity 10-14 0C/100KWH

CHAPTER#3 VACUUM LADLE DEGASSING

3.2 Vacuum Ladle Degassing:The Melting Shop of PSM is equipped with Vacuum Ladle Degassing Unit. It is the

final treatment of molten steel before going to continuous casting unit. There are

different methods of Vacuum Ladle Degassing of steel some of them are as follows:

Recirculation Degassing (RH)

Recirculation Degassing with oxygen top lance (RH-OB)

Ladle Degassing (VD, Tank Degassing)

Vacuum Oxygen Decarburization (VOD)

Vacuum Ladle Degassing Unit in PSM is capable to perform two of the above

vacuum degassing treatments, VD & VOD.

3.2.1 Process Chemistry: Methods of vacuum ladled gassing utilize there action  of  deoxidation  by  carbon 

dissolved in steel according to the equation:

[C] + [O] = {CO}

where: [C] and [O] - carbon and oxygen dissolved in liquid steel; {CO} - gaseous

carbon monoxide.

Vacuum treatment of molten steel decreases the partial pressure of CO, which

results in shifting equilibrium of the reaction of carbon oxidation. Bubbles of carbon

monoxide form in the liquid steel, float up and then they are removed by

vacuum system.

In addition to de-oxidation vacuum treatment helps to remove Hydrogen dissolved

in liquid steel. Hydrogen diffuses into the CO bubbles and the gas is then evacuated

by the vacuum pump. Movement of the molten steel caused by CO bubbles also

results in refining the steel from non-metallic inclusions, which agglomerate, float

up and are absorbed by the slag. CO bubbles also favor the process of floating and

removal of nitride inclusions and gaseous Nitrogen.

As a result of vacuum treatment the oxygen content of molten steel reduced to 5 to

10 ppm.Steels refined in vacuum are characterized by homogeneous structure, low

content of non-metallic inclusions and low gas porosity. Vacuum degassing methods

are used for manufacturing large steel ingots, rails, ball bearings and other

highquality steels.

CHAPTER#3 VACUUM LADLE DEGASSING

3.2.2 Process Detail:The Vacuum Ladle Degassing Unit consist of following main parts:

Watering Plant( Vacuum Generator)

Vacuum Chamber(Pit Type)

Regulator( Monitor Vacuum)

Valves(Control Vacuum)

3.2.3 Vacuum Generation:Vacuum Ladle Degassing Unit maximum vacuum is achieved step wise, as follows:

S.N Vacuum Pumps Vacuum

Range(torr)

Time

1. 2-Rotary Pump 760-220 10 min

2. Ejector Pump E4 220-60 3min

3. Ejector Pump E3 60-6 3min

4. Ejector Pump E2 6-3.7 10min

Initially 2-rotary pumps generate vacuum up to 220 torr, then one rotary pump stops

and the ejectors pumps are started according vacuum achieved.

3.2.4 Ladle Degassing Process(VD): In order to perform Ladle Degassing, on ladle

with molten steel, which is arrived from Ladle

Furnace Unit, a ledle cover is placed. On this

vacuum cover a Silicon O-ring is placed as

vacuum seal and finally vacuum cover is placed.

The ladle is equipped with a porous refractory

plug mounted in the ladle bottom which is made

up of high alumina refractory. Through the plug

argon is supplied during vacuum treatment. There

is an addition hopper with vacuum lock on the chamber cover. The hopper is used

for adding alloying elements and also for oxygen lancing in VOD treatment.

CHAPTER#3 VACUUM LADLE DEGASSING

The reaction [C] + [O] = {CO} starting in the steel under vacuum conditions

causes stirring, which is additionally intensified by argon blown through the bottom

porous plug.Intensive stirring of the melt and the slag results in deep

desulfurization of the steel. Desulfurizing slags possessing high sulfur solubility are

used in this process. Argon and CO bubbles also favor the process of floating and

removal of nitride inclusions and gaseous nitrogen.

Benefits of Ladle Degassing (VD, Tank Degassing):

-Hydrogen removal (degassing);

-Oxygen removal (deoxidation);

-Deep sulfur removal (desulfurization);

-Carbon removal (decarburization);

-Precise alloying;

-Non-metallic inclusions (oxides and nitrides) removal;

-Temperature and chemical homogenizing.

3.2.5 Vacuum Oxygen Decarburization (VOD) In this method a vacuum chamber is equipped with a vertical water cooled lance

for blowing oxygen on the molten steel surface.

Vacuum Oxygen Decarburization (VOD)

method is used for manufacturing

Stainless steels. Oxidation of liquid steel

components under vacuum differs from that at

normal pressure: oxygen is consumed mainly by

the reaction [C] + [O] = {CO} rather than by

oxidation of chromium, which is the main

constituentof stainless steels.

VOD process allows to decarburize the

steel with minor chromium losses.

Oxidation reactions have also heating effect

therefore the treated metal may be heated to a required temperature without any

additional energy source.

After having the decarburization (oxidation) stage completed deoxidizers are

added to the steel in order to remove excessive oxygen. Then a Desulfurizing slag is

CHAPTER#3 VACUUM LADLE DEGASSING

added to the molten steel surface. Stirring of the melt and the slag caused by argon

blown through the porous bottom plug results in deep desulfurization of the steel.

At the end of the oxygen blowing period, the basicity of the slag is 1.8–2.5.

Combined with strong argon stirring, this slag provides effective sulfur removal.

Amount of Oxygen Blown=16(%C) + 8(%Si) + 6.2(%Al) + Total Tonnage of

ladle.

Benefits   of   Vacuum   Oxygen Decarburization (VOD):

-Deep carbon removal (decarburization). Low-carbon (<0.03%) content.

-Low losses of chromium in treatment of stainless steels;

-Hydrogen removal (degassing);

-Sulfur removal (desulfurization);

-Precise alloying;

-Non-metallic inclusions (oxides and nitrides) removal;

-Temperature and chemical homogenizing.

3.2.6 Argon Purging Ranges: VD – 2 bar.

VOD-6 bar.

CHAPTER#3 CONTINOUS 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.

3.3 Continuous Casting Process:

In PSM the continuous casting machine consist of three castig strans , two of them for bilit casting and one for bloom casting. The CC process detail is as follows:

3.3.1 Process Overview:

Steel after treatment from VD unit is taken taken to the continuous casting machine. The ladle is raised onto casting position above the tundish. Liquid steel flows out of the ladle into the tundish and then into a water-cooled copper mold. Solidification begins in the mold, and continues through the First Zone and Strand Guide. In this configuration, the strand is straightened, torch-cut, then discharged for intermediate storage or hot charged for finished rolling.

Casting: To start a cast, the mold 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 mold. The steel poured into the mold 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 mold along with the dummy bar.

Liquid steel continues to pour into the mold to replenish the withdrawn steel at an equal rate. The withdrawal rate depends on the cross-section, grade and quality of steel 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 mold, 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. 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: blooms, billets.

CHAPTER#3 CONTINOUS CASTING

The width-to-thickness ratio, referred to as the "Aspect Ratio", is used to determine the dividing line between blooms and slabs. An Aspect Ratio of 2.5:1 or greater constitutes an as-cast product referred to as a Slab.

3.3.2 Liquid Steel Transfer:

There are two steps involved in transferring liquid steel from the ladle to the molds. First, the steel must be transferred (or teemed) from the ladle to the tundish. Next, the steel is transferred from the tundish to the molds. Tundish-to-mold 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.

3.3.3 Tundish Overview:

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 molds. The tundish also serves several other key functions:

Enhances oxide inclusion separationProvides a continuous flow of liquid steel to the mold during ladle exchanges.

Maintains a steady metal height above the nozzles to the molds, 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 mold(s).

Product Sizes(mm2)

Bloom 250

Billet 110, 125, 150

CHAPTER#3 CONTINOUS CASTING

3.3.4 Casting Mold

The main function of the mold 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 mold is basically an open-ended box structure, containing a water-cooled inner lining fabricated from a high purity copper alloy. Mold 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.

Heat transfer from the steel shell surface to the copper mold outer surface Heat transfer through the copper mold Heat transfer from the copper mold inner surface to the mold cooling water

 3.3.5 Mold Oscillation

Mold 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 mold is reduced through the use of mold 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 mold.

3.3.6 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.

Parameters RangesTundish temperature 15500C - 15600CCasting speed 2.23 – 2.25 m/minRadiation source 5.2 microSV/hrStrand radius 7 m

CHAPTER#4 Q-SHOP

All the steel billet manufactured by the steel plant is catogrised by its specific chemical properties and stored in billet yard. The rolling mill then draws down on this billet by grade depending on final planned product.

4.1 Preheating of billet:

Once the appropriate billet grade is determined the billet must be reheated and is loaded into gas reheating furnace. The furnace is continually loading, so as onr billet enters the furnace another that is fully heated is rolled out ready for rolling process. The preheating furnace consist of two zones Top Zone & Soaking Zone. The reheating furnace capacity is as follows:

Billet Size(mm2)

No. of Billets

Time(hr)

110 135 3

125 115 4

150 97 5

The preheating temperature of billets ranges b/w 12200C - 12600C.The temperature above this range and overheating time can cause the billets to stick together. For complete combustion fuel to air ratio is maintained at 1:10, so that no heat loss take place.

4.2 Bar mill configuration: The bar rolling mill consist of three sections: Cross Country 3-Hi Roughing mill. Cross Country 2-Hi Roughing mill. Finishing/ straightening mill.

Products Ranges(mm)Flat Bar 50x6 – 120x50

Round Bar 15 – 80Deformed Bar 12 - 36

CHAPTER#4 Q-SHOP

4.3 Bar Rolling Defects:

Different defects can occur in rolled bars

Defects from improper mill practice

• Cracks

• Scratches

• Fins and laps

• Corner cracks:

Defects from improper roll pass design:

During rolling strains and heat are accumulated which may result in the development of defects. Just as an improper roll pass design may initiate and increase the defect size during rolling, a proper design may reduce the defects, and in the best case, even eliminate them.

4.4 Final Inspection:

Tensile Test Bend Test MPI

CHAPTER#5 N-SHOP

5.0 Slabing & Blooming Mill

Rolling is metal forming process in which metal stock is passed through a pair of rolls which exerts the compressive forces. Rolling process reduces the thickness or change the cross section of material.

5.1 Hot Rolling:Hot rolling is a metalworking process that occurs above the recrystallization temperature of the material. After the grains deform during processing, they recrystallize, which maintains an equiaxed microstructure and prevents the metal from work hardening. The starting material is usually large pieces of metal, like semi-finished casting products, such as slabs, blooms. If these products came from a continuous casting operation the products are usually fed directly into the rolling mills at the proper temperature. In smaller operations the material starts at room temperature and must be preheated. This is done in a gas- or oil-fired soaking pit for larger workpieces. As the material is worked the temperature must be monitored to make sure it remains above the recrystallization temperature. To maintain a safety factor a finishing temperature is defined above the recrystallization temperature; this is usually 50 to 100 °C (90 to 180 °F) above the recrystallization temperature. If the temperature does drop below this temperature the material must be re-heated before more hot rolling.

CHAPTER#5 N-SHOP

5.2 Mill Classification:

Furnace Delivery Table

Mill Approach Table

Mill Front Table

Turn Table

Feed Roll

Main Roll

Feed Roller

Mill Back Table

Shearing Entry Table

Shearing delivery table

Leveler Entry Table

Leveler

Leveler delivery Table

5.3 Preheating Furnace:

Preheating is the box type furnace used in the slabing & blooming mill to preheat the slab and bloom. Slabs or blooms are preheated. above the recrystallization temperature usually at 1250 °C. preheating furnace has two zones heating & soaking zone. They have different temperatures.

CHAPTER#5 N-SHOP

Zones Process value Setup temperature

Top zone 1220°C 1220 °CBottom zone 1209°C 1220°C Soaking zone 1263 °C 1260 °C

Refractory Material In Furnace : Refractory materials used in the preheating furnace areInsulation lining and refractory bricks.Electro cast bricks used for lining purpose.Fuel In Furnace: Natural gas and air used as fuel in furnace with 1:20 ratio.

5.4 Rollers:Working load: 800 – 900 tonRolls dia: 820-740 mmChilled layer on rolls: 60 mmWeight of one roll: 10 ton

5.5 Rolling Mill Input:

Slab and bloom is input for the rolling mill.

Slab:

Length: 1000 – 1300 mmThickness: 200 -250 mmWidth: 700 – 1000 mmMaximum passes for 250 mm thickness slab are 40 passes to achieve standard thickness of plate.

CHAPTER#5 N-SHOP

Out Put:

Out put of the mill is the plate which was deformed from slab.Plate:

Length: 13 mWidth: 1.5 mThickness achieved: 8-12 mm

Wastage from plate :

Burning rejection: 3% Shearing rejection: 5%

Defects in plate : Pitting Dimensional variation Cracks Piping Laminations

CHAPTER#6 Q-SHOP

Forging Process:

Forging is a term applied to a family of processes that induce plastic deformation through localized compressive forces applied through dies. The equipment can take the form of Hammers, Presses and machines.

6.1 R 1 ShopIn R1 shop there is the use of impression die drop forging to give the shape as required.

R1 process Sequence: Weight Calculation Length Calculation Pre Shaping (working load 500 kg) Die Forging (working load 3.1 ton) Piercing Trimming Straightening Inspection Shot Blasting Final Inspection

6.2 Impression-die drop forging:

Impression-die forging is also called closed-die forging. In impression-die work metal is placed in a die resembling a mold, which is attached to the anvil. Usually the hammer die is shaped as well. The hammer is then dropped on the work piece, causing the metal to flow and fill the die cavities. The hammer is generally in contact with the work piece.

CHAPTER#6 R-SHOP

R1 shop Input:Billet pieces of 75 mm dimension.R1 is used for 3-12 kg material. .Furnace:

Furnace is used to preheat the billet pieces at 1250C Furnace capacity is 100 pieces/batch. Gas and compressed air used as fuel in the furnace for 1:1 ratio.

R1 shop Products:

Gear blank, round bars, hollow sleeves, grate bars, pinion and cleat.

Defects:

Mismatching Pitting Waviness Cracks

6.3 R3 Shop

In R3 shop there is the use of press forging to give the shape as required.

Press Forging:

Press forging works by slowly applying a continuous pressure or force, which differs from the near-instantaneous impact of drop-hammer forging. The amount of time the dies are in contact with the work piece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.

CHAPTER#6 R-SHOP

R3 shop input:

Ingot casting and ESR casting of 720 mm dia. R1 used for 10-12 ton casting. Water hydraulic press has 1700 ton working load.

Furnace:

3 batch type furnaces are used for preheating the bars which has the 2,4 and 10 ton capacity.

Other furnace is boggy type furnace which has 10 ton capacity.

R3 shop output:

Round bar, rectangular bar, square bar, octagonal. Products range: 1100mm max dia and 180 min dia.

5 S SYSTEM