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SRMB

Leadership through innovation

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MODERN STEELMAKINGMODERN STEELMAKING -- PRELUDEPRELUDE

The iron and steel industry enjoys a high priority in theThe iron and steel industry enjoys a high priority in the

development plans of most countries , primarilydevelopment plans of most countries , primarily

because of the significant role of steel in theirbecause of the significant role of steel in their

industrial development and economic growth.industrial development and economic growth.

India's ranking in terms of per capita consumption ofIndia's ranking in terms of per capita consumption of

steel is at the 15steel is at the 15thth position internationally at 39 Kg.position internationally at 39 Kg.

From a crude steel output of 6.5 million tonnes sinceFrom a crude steel output of 6.5 million tonnes since

19651965

66, India is now the fifth largest producer of66, India is now the fifth largest producer of

steel in the world with a crude steel production ofsteel in the world with a crude steel production of

50.85 million tonnes per annum superseded only by50.85 million tonnes per annum superseded only by

China, Japan, USA and Russia. The growth from 2005China, Japan, USA and Russia. The growth from 2005

to 2006 had been a phenomenal 11.4to 2006 had been a phenomenal 11.4%.%.

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The role played by steel in the economic developmentThe role played by steel in the economic development

of a country can be visualized from the fact that evenof a country can be visualized from the fact that even

countries who do not possess any raw materials havecountries who do not possess any raw materials have

gone ahead with bold plans of steel developmentgone ahead with bold plans of steel development

based on imported raw materials.based on imported raw materials.

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MODERN STEELMAKINGMODERN STEELMAKING -- BASICSBASICS

Steel making involves removal of impurities as theirSteel making involves removal of impurities as their

respective oxides (except sulphur which is reduced).respective oxides (except sulphur which is reduced).

The oxides are eliminated either as gas (e.g. CarbonThe oxides are eliminated either as gas (e.g. Carbon

as carbon monoxide) or as liquid oxide product ofas carbon monoxide) or as liquid oxide product of

suitable chemical character known as slag.suitable chemical character known as slag.

Steel can be produced efficiently only if refining isSteel can be produced efficiently only if refining is

adequate i.e. Right quality slag is made and cleanadequate i.e. Right quality slag is made and clean

slag and metal separation is brought about.slag and metal separation is brought about.

Except sulphur, all the rest (carbon, silicon,Except sulphur, all the rest (carbon, silicon,

manganese, phosphorus) are removed throughmanganese, phosphorus) are removed through

oxidation processes and are favoured under oxidizingoxidation processes and are favoured under oxidizing

conditions of steel making.conditions of steel making.

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The present requirement of sulphur in steel isThe present requirement of sulphur in steel is

more stringent as continuous casting is invariablymore stringent as continuous casting is invariably

adopted to convert liquid steel into billets/bloomsadopted to convert liquid steel into billets/blooms

with a sulphur level of around 0.02with a sulphur level of around 0.02%% to avoidto avoidtransverse cracking.transverse cracking.

It is universally accepted that very low sulphurIt is universally accepted that very low sulphur

contents can only be produced through moderncontents can only be produced through modern

and efficient external deand efficient external de--sulphurisation techniquessulphurisation techniques

for hot metal from blast furnaces.for hot metal from blast furnaces.

Calcium carbide and magnesium bearing reagentsCalcium carbide and magnesium bearing reagents

injected with a carrier gas are found to lower downinjected with a carrier gas are found to lower down

sulphur to extremely low levels.sulphur to extremely low levels.

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MODERN STEELMAKINGMODERN STEELMAKING -- HISTORYHISTORY

Modern steel making is supposed to have begunModern steel making is supposed to have begun

with the advent of the Bessemer process ofwith the advent of the Bessemer process ofsteelmaking in the 1860s in the UK.steelmaking in the 1860s in the UK.

This was followed by open hearth processes, butThis was followed by open hearth processes, but

its productivity could not exceed beyond 35its productivity could not exceed beyond 35tons/hour as against that of 500 tons/hour fromtons/hour as against that of 500 tons/hour from

LD, OBM or Hybrid processes.LD, OBM or Hybrid processes.

The demands of increased productivity coupledThe demands of increased productivity coupledwith lower capital cost led to steelmaking in basicwith lower capital cost led to steelmaking in basic

lined furnaces, making basic slag, using oxygenlined furnaces, making basic slag, using oxygen

as the refining media to be generally known asas the refining media to be generally known as

basic oxygen furnace (BOF) or LD steel making.basic oxygen furnace (BOF) or LD steel making.

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Oxygen steel making is now universally adopted forOxygen steel making is now universally adopted for

steel production since 1950s to maintain efficiency andsteel production since 1950s to maintain efficiency and

economy, processes being faster, economical andeconomy, processes being faster, economical and

easily controllable.easily controllable.

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MODERN STEELMAKINGMODERN STEELMAKINGBOF/LD STEELBOF/LD STEEL

MAKINGMAKING

In an LD refining is complete in about 20In an LD refining is complete in about 20 -- 25 minutes25 minutes

of oxygen blowing and a tap to tap time of 40 to 60of oxygen blowing and a tap to tap time of 40 to 60

minutes is needed.minutes is needed.

The oxidizing conditions in LD are not conducive toThe oxidizing conditions in LD are not conducive to

desulphurisation. External desulphurisation of moltendesulphurisation. External desulphurisation of molten

iron in transfer ladles is the answer. Major steel plantsiron in transfer ladles is the answer. Major steel plants

around the world have adopted this process toaround the world have adopted this process to

achieve a sulphur level below 0.001achieve a sulphur level below 0.001%%..

Use of multi hole lances (4 to 7 hole lances) in largerUse of multi hole lances (4 to 7 hole lances) in larger

converters has cut down blowing time, improved theconverters has cut down blowing time, improved the

yield and increased lining life.yield and increased lining life.

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However, 90However, 90% of phosphorus in the metal is% of phosphorus in the metal is

removed in LD to 0.025%.removed in LD to 0.025%.

Lining life of 1000 heats are now common. LiningLining life of 1000 heats are now common. Lininglife of tarred dolomite lining in LD at TATA steellife of tarred dolomite lining in LD at TATA steel

has achieved the international norm of 1200 heatshas achieved the international norm of 1200 heats

with consequent cost advantages amounting towith consequent cost advantages amounting toalmost Rs.175almost Rs.175--200/Ton of liquid steel.200/Ton of liquid steel.

Methods have been devised for continuousMethods have been devised for continuous

monitoring of carbon and temperature during themonitoring of carbon and temperature during theblow and make midblow and make mid-- course corrections to attaincourse corrections to attain

correct turncorrect turn-- down conditions.down conditions.

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Heat times need to be further improved. ComparedHeat times need to be further improved. Compared

to 30 to 40 minutes obtained in large converters into 30 to 40 minutes obtained in large converters in

other countries, the heat time in India is aroundother countries, the heat time in India is around

one hour.one hour.

By intensifying blowing rates, improving operatingBy intensifying blowing rates, improving operating

practices and cutting down delays, it should bepractices and cutting down delays, it should be

possible to reduce heat time to 40 to 50 minutes.possible to reduce heat time to 40 to 50 minutes.

This is significant as even a one minute savingThis is significant as even a one minute saving

means an increase in production by 2means an increase in production by 2%.%.

From less than 3 million tonnes in 1957, there hasFrom less than 3 million tonnes in 1957, there has

been a spectacular rise in world LD capacity tobeen a spectacular rise in world LD capacity to

more than 50more than 50% of the total world production of% of the total world production of

1244 million tons.1244 million tons.

The changing pattern of steel makingThe changing pattern of steel making and theand the

increasing share of LD steel are illustrated in FIGincreasing share of LD steel are illustrated in FIG

1.1.

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CHANGING PATTERN OF STEELMAKINGCHANGING PATTERN OF STEELMAKING

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MODERN STEEL MAKINGMODERN STEEL MAKINGOBM/HYBRIDOBM/HYBRID

STEEL MAKINGSTEEL MAKING

Modifications to the basic LD process (generallyModifications to the basic LD process (generally

known as BOF) came in the form of OBM processknown as BOF) came in the form of OBM process

where oxygen with fluxes are blown through thewhere oxygen with fluxes are blown through the

bottom of the vessel.bottom of the vessel.

Further modification led to hybrid blowing whereFurther modification led to hybrid blowing where

top and bottom blowing simultaneously withtop and bottom blowing simultaneously with

oxygen has been successfully used and has theoxygen has been successfully used and has the

potential of being the favoured process for futurepotential of being the favoured process for future

steel making.steel making.

The OBM process (oxygen bottom maxhutte)The OBM process (oxygen bottom maxhutte)

developed in Germany in 1967 claim inherentdeveloped in Germany in 1967 claim inherent

advantages of a quieter blow and better mixingadvantages of a quieter blow and better mixing

that could be gained by blowing pure oxygenthat could be gained by blowing pure oxygenthroughthrough

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converter bottom along with an endothermicconverter bottom along with an endothermic

shielding of the oxygen stream with propane/shielding of the oxygen stream with propane/

natural gas to protect converter bottomnatural gas to protect converter bottom

refractories.refractories.

The proven advantages of the OBM process overThe proven advantages of the OBM process over

other oxygen steel making process are :other oxygen steel making process are :

InInstallation cost advantagestallation cost advantage

-- of OBM over BOF is between 5% to 8% for aof OBM over BOF is between 5% to 8% for a

new facility.new facility.

-- Lower vessel size (0.6 cum/ton of steel asLower vessel size (0.6 cum/ton of steel as

against 0.8 cum/ton of steel in case of BOF).against 0.8 cum/ton of steel in case of BOF).-- Low structural cost (no high bay furnaceLow structural cost (no high bay furnace

aisle, no complex elevated bin system).aisle, no complex elevated bin system).

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Improved yield and lower material usage:Improved yield and lower material usage:

-- 1.51.5% to 2% higher yield due to less FeO in slag.% to 2% higher yield due to less FeO in slag.

-- BetterBetter Recovery of ferro alloys due to lowerRecovery of ferro alloys due to lower

oxygen level in bath.oxygen level in bath.

-- 55%% -- 10% lower oxygen requirement due to10% lower oxygen requirement due tointimate and thorough mixingintimate and thorough mixing of oxygen in bath.of oxygen in bath.

Product quality:Product quality:

-- Phosphorus and sulphur removal very effective.Phosphorus and sulphur removal very effective.

Production rate:Production rate:

-- Use of oxygen blowing rate 25Use of oxygen blowing rate 25% higher then% higher then

BOF of same capacity shortens tap to tap timeBOF of same capacity shortens tap to tap timewith consequent increase in production rate bywith consequent increase in production rate by

10% compared to BOF.10% compared to BOF.

-- Higher metallic yields contribute to increasedHigher metallic yields contribute to increasedproductivity.productivity.

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MODERN STEELMAKINGMODERN STEELMAKINGELECTRIC ARCELECTRIC ARC

FURNACE (EAF) STEELMAKINGFURNACE (EAF) STEELMAKING

Steelmaking through EAF became a commercialSteelmaking through EAF became a commercial

practice at the beginning of the last century.practice at the beginning of the last century.

In EAF oxidizing and reducing conditions can beIn EAF oxidizing and reducing conditions can be

maintained at will during refining and a variety ofmaintained at will during refining and a variety of

steels can be manufactured with very low sulphur andsteels can be manufactured with very low sulphur and

phosphorus.phosphorus.

In view of the availability of power and that too atIn view of the availability of power and that too at

competitive rates with respect to other fuels like oil,competitive rates with respect to other fuels like oil,

oxygen, bigger EAF have come to use.oxygen, bigger EAF have come to use.

From a share of 8From a share of 8% in 1950, EAF share in total global% in 1950, EAF share in total global

steel production is now more than 30%.steel production is now more than 30%.

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This share is likely to go up in view of theThis share is likely to go up in view of the

increasing cost of fuel visincreasing cost of fuel vis--aa--vis power.vis power.

New EAFs are coming up for production of evenNew EAFs are coming up for production of even

mild steels with:mild steels with:

Design ModificationDesign Modification

-- Rapid melting technologyRapid melting technology

-- Water cooled panelsWater cooled panels-- Eccentric shell with bottom tappingEccentric shell with bottom tapping

-- Emission / noise controlEmission / noise control

Process ModificationProcess Modification-- Coupling with ladle refining furnace (LRF, VOD,Coupling with ladle refining furnace (LRF, VOD,

AOD, etc.)AOD, etc.)

-- Process automationProcess automation-- Foamy slag practiceFoamy slag practice

Ch M difi iCh M difi i

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Charge ModificationCharge Modification

-- Use of hot metalUse of hot metal

-- Use of DRI (sponge iron)Use of DRI (sponge iron)Capacities have increased to compete with otherCapacities have increased to compete with other

steel making processes to obtain desired economysteel making processes to obtain desired economy

of production.of production.Use of ultra high power (UHP) in place of regularUse of ultra high power (UHP) in place of regular

power supply results in saving of melting timepower supply results in saving of melting time

(30(30%%) and of refining time (10) and of refining time (10%%).).Very often UHP furnaces are used for meltingVery often UHP furnaces are used for melting

coupled with LRF for final refining. Net totalcoupled with LRF for final refining. Net total

transformer rating in coupled condition is muchtransformer rating in coupled condition is muchlower.lower.

Roof inserted waterRoof inserted water-- cooled lance for injectingcooled lance for injecting

oxygen in large EAF bring in economy inoxygen in large EAF bring in economy inmanufacture.manufacture.

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Use of hot metal from blast furnace along withUse of hot metal from blast furnace along with

sponge iron result in reduced power consumptionsponge iron result in reduced power consumption

for overall economy.for overall economy.

Heat time is not affected in an EAF when spongeHeat time is not affected in an EAF when sponge

iron used has a metalization of more than 92iron used has a metalization of more than 92%.%.

Hot metal and sponge iron in EAF route is 30Hot metal and sponge iron in EAF route is 30--40%40%

cheaper then hot metal and BOF combination forcheaper then hot metal and BOF combination for

equivalent production capacity.equivalent production capacity.

The clear advantages of the EAF are:The clear advantages of the EAF are:

-- Yield nearly 91%Yield nearly 91%

-- Furnace availability 96Furnace availability 96%%

-- Favourable cost pattern of electrical energyFavourable cost pattern of electrical energy

-- Wide range of furnace capacityWide range of furnace capacity

-- Flexibility in terms of irregular productionFlexibility in terms of irregular production

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MODERN STEEL MAKINGMODERN STEEL MAKINGINDUCTIONINDUCTION

FURNACE STEEL MAKINGFURNACE STEEL MAKING

For steel making, medium and high frequencyFor steel making, medium and high frequency

induction furnaces are universally adopted.induction furnaces are universally adopted.

It is essentially a process of melting and hardly anyIt is essentially a process of melting and hardly any

refining take place, a process wherein what goes inrefining take place, a process wherein what goes in

must come out.must come out.

Thin layer of dry slag (works as insulating cover) doesThin layer of dry slag (works as insulating cover) does

not take part in refining.not take part in refining.

Limited holding capacity and inability to control theLimited holding capacity and inability to control thecomposition of the melt except through carefulcomposition of the melt except through careful

selection of scrap appear as the chief draw backs ofselection of scrap appear as the chief draw backs of

the induction furnace from metallurgical andthe induction furnace from metallurgical and

commercial viewpoints.commercial viewpoints.

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In spite of inherent inadequacies as a melting unitIn spite of inherent inadequacies as a melting unit

for making quality steel, growth in mild steelfor making quality steel, growth in mild steel

capacity through induction furnace melting in Indiacapacity through induction furnace melting in India

has been a phenomenal 26has been a phenomenal 26% in 2005% in 2005 06 over06 over20042004 05 as against 7% through EAF melting.05 as against 7% through EAF melting.

During 2006During 2006--07 Mini Steel plants contributed 25.2007 Mini Steel plants contributed 25.20

million tonnes out of a total of 50.85 million tonsmillion tonnes out of a total of 50.85 million tonsproduced in India. EAF's share was 9.8 millionproduced in India. EAF's share was 9.8 million

tons. The rest 15.40 million tons being fromtons. The rest 15.40 million tons being from

induction furnace.induction furnace.A record number of 787 induction furnace unitA record number of 787 induction furnace unit

were in existence in 2005were in existence in 2005--06, secondary refining06, secondary refining

being absent in most cases.being absent in most cases.

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Except the Indian subcontinent, nowhere inExcept the Indian subcontinent, nowhere inthe world basic quality steelmaking employthe world basic quality steelmaking employ

the induction furnace route.the induction furnace route.

This stems from the fact that lot of smallThis stems from the fact that lot of small

time steel players have adopted this routetime steel players have adopted this route

involving low capital cost and lowerinvolving low capital cost and lowermanufacturing cost.manufacturing cost.

Under the existing conditions, manufactureUnder the existing conditions, manufacture

of steel through DRI route employingof steel through DRI route employinginduction furnace as the only melting unitinduction furnace as the only melting unit

can not achieve the norms set by thecan not achieve the norms set by the

relevant BIS standards.relevant BIS standards.

MODERN STEELMAKINGMODERN STEELMAKING QUALITY ANDQUALITY AND

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MODERN STEELMAKINGMODERN STEELMAKING QUALITY ANDQUALITY AND

COSTCOST

QualityQuality means attaining desired specification withmeans attaining desired specification with

respect to:respect to:

Chemical compositionChemical composition

CleanlinessCleanliness

Gas contentGas content

Cost is substantially affected by energyCost is substantially affected by energy

consumption and cost of raw materials e.g. Use hotconsumption and cost of raw materials e.g. Use hot

metal in EAF has a distinct cost advantage.metal in EAF has a distinct cost advantage.

Whole efficiency of a steelmaking shop can beWhole efficiency of a steelmaking shop can be

broadly assessed in terms ofbroadly assessed in terms of

Production RateProduction Rate

YieldYield

Quality of ProductionQuality of ProductionRefractory ConsumptionRefractory Consumption

LOOKING AHEAD GROWTH PROSPECTS

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LOOKING AHEADLOOKING AHEAD--GROWTH PROSPECTSGROWTH PROSPECTS

IRON AND STEEL INDUSTRY IN INDIAIRON AND STEEL INDUSTRY IN INDIA

While contributing almost 6While contributing almost 6% of the GNP, crude% of the GNP, crude

steel production has grown at a CAGRsteel production has grown at a CAGR

(cumulative annual growth rate) of 10.5% while(cumulative annual growth rate) of 10.5% while

capacity has shown a 7.5% growth over a periodcapacity has shown a 7.5% growth over a period

of 5 years between 2001of 5 years between 2001--02 to 200502 to 2005--06.06.

Given the pace and scale of infrastructure/Given the pace and scale of infrastructure/

construction activities, prospects of future growthconstruction activities, prospects of future growth

in the steel industries is directly linked with thein the steel industries is directly linked with the

growth in its downstream industries i.e. Regrowth in its downstream industries i.e. Re--rolling.rolling.

The most notable aspect is of course the entry ofThe most notable aspect is of course the entry of

global steel majors POSCO, Mittal Steel andglobal steel majors POSCO, Mittal Steel and

others to set up steel plants in the country, whichothers to set up steel plants in the country, which

are expected to alter the dynamics of the Indianare expected to alter the dynamics of the Indian

Iron and Steel Industr u on commencement.Iron and Steel Industr u on commencement.

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India has attained the status of the fifth largestIndia has attained the status of the fifth largest

crude steel producer in the world in 2007 and thiscrude steel producer in the world in 2007 and this

status will be positively affected once thesestatus will be positively affected once these

expansion projects become operational.expansion projects become operational.

The National Steel Policy has laid down the longThe National Steel Policy has laid down the long

term vision of growth for the Indian steel Industryterm vision of growth for the Indian steel Industry

and domestic steel entrepreneurs are pursuing anand domestic steel entrepreneurs are pursuing an

expansion plan that is ambitious by all standards.expansion plan that is ambitious by all standards.

The Vision: 110 millionThe Vision: 110 million ttonnes of steel productiononnes of steel productionby 2019by 2019 -- 20.20.

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SUGGESTED BIBLIOGRAPHYSUGGESTED BIBLIOGRAPHY

Making, Shaping and Treating of Steel, an ASTMMaking, Shaping and Treating of Steel, an ASTM

Publication.Publication.

An Introduction to Modern Steel Making by Dr. R.An Introduction to Modern Steel Making by Dr. R.H. Tupkary and V. R. Tupkary.H. Tupkary and V. R. Tupkary.

International Symposium onInternational Symposium on Fifty Years ofFifty Years of

MetallurgyMetallurgy at BHU in December, 1973. Paperat BHU in December, 1973. Paperpresented by Dr. M. N. Dastur onpresented by Dr. M. N. Dastur on Iron and SteelIron and Steel

Industry in IndiaIndustry in India..

The ASEAThe ASEA--SKF Steel Refining Process by M.SKF Steel Refining Process by M.Tiberg, T. Buhre, H. Herlitz of SKF Helefors SteelTiberg, T. Buhre, H. Herlitz of SKF Helefors Steel

works IFJ, April 1966.works IFJ, April 1966.

Electric Furnace RoundElectric Furnace Round-- Up The Magazine ofUp The Magazine ofSteel Producing, June 1966.Steel Producing, June 1966.

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ManufactureManufacture of Iron and Steel, Vol.I and II by G. R.of Iron and Steel, Vol.I and II by G. R.

Bashforth, An Asia Publication.Bashforth, An Asia Publication.

M. N. Jha et. Al., Tata Search , 1994, P.15.M. N. Jha et. Al., Tata Search , 1994, P.15.

Sanjay Kumar et. Al., Tata Search, 1994, P.35.Sanjay Kumar et. Al., Tata Search, 1994, P.35.

Iron Making and Steel Making by A. Chatterjee,Iron Making and Steel Making by A. Chatterjee,1996, 23(4), P. 293.1996, 23(4), P. 293.

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