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O

R

E

Blast furnace

PIG

IRO

N

Cupola Puddling Furnace

Bessemer ConverterO.H. Furnace

Electric FurnacesOxygen Furnaces

CAS

T

IRON

WROUG

HT

IRON

STE

EL

IRON AND STEEL METALLURGY

Most metals occur in nature as oxides, sulfides, chlorides, carbonates,

etc., and the critical step in converting these ores into metals, i.e., in

extraction metallurgy, is a process of chemical reduction. In most cases, ores are mined and then treated by various mechanical

and chemical metallurgical processes to extract the metals and convert

them into the metallic (chemically uncombined) form.

The recovery of metal from its ore involves three types of operations:

1. Ore dressing  separation of the metal containing mineral from the

gangue!. Concentration   preliminary chemical treatment that produces a

compound suitable for reduction to the metal". #eduction to the metal, possible $ith a subse%uent refining treatment.

&errous materials contain iron, and the one element people use more than

all other is iron. &errous materials are the most important metals'alloys in the metallurgical

and mechanical industries because of their very extensive use.

The $idespread use of ferrous alloys is accounted for by three factors:

1. Iron containing compounds exist in abundant %uantities $ithin the earths

crust.!. Metallic iron and steel alloys may be produced using relatively economical

extraction, refining, alloying and fabrication techni%ues.". &errous alloys are extremely versatile, in that they may be tailored to have

a $ide range of mechanical and physical properties.

The principal disadvantage of many ferrous alloys is their susceptibility to

corrosion.

Pig Iron

 

produced in a blast furnace

the first product in the process of converting iron ore into useful metal.

  the iron ore becomes pig iron $hen the impurities are burned out in a b

furnace. Though still containing some impurities, pig iron has a high m

content.It is the ra$ material for all iron and steel products.

It is of great importance in the foundry and in steel maing processes.

  *sual composition: "+- , 1+"- /i, 0.1+1- Mn, 0."+1.- 2, under 1./, balance is &e

 

2ig iron partly refined in a cupola produces various grades of cast iron.

 

3y puddling or shotting process, wrought iron is produced from pig iron

  /teel is produced from pig iron by various steel maing processes such

3essemer. 4pen+hearth, oxygen, electric and spray steel maing.

 

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Pig Iron Cassi!ication"

1. #asic Pig Iron *sed for steel maing and is lo$ in silicon (1.5- max.) to prevent

attac of the refractory linings of refining furnaces and to control slag

formation. It must be lo$ in / (0.0-) since / is an active impurity in steel and is

not eliminated in the refining furnaces. 2 normally is held to less than 1- and Mn to a range of 1+!-.

content varies from ".5+.-.

!. $oundr% Pig Iron It includes all the types that are used for the production of iron castings

*sual composition:

− /i: 0.5 ".5-

− Mn: 0. 1.!5-

− 2: 0.0"5 0.6-

− : " .5-

− /: up to 0.05-

− &e: remainder 

". $erroao%s are alloys of pig iron, each rich in one specific element.

They are used as additives in iron and steel industries, to control or 

alter the properties of iron and steel.e.g.

o Ferromanganese: pig iron containing 74-82% Mn

o Ferrosilicon: pig iron with 5-17% Si 

#LAST $URNACE

7lements of 3last &urnace onstruction:

A& LO'ER SECTION1. (earth (lo$er section) It is a cylindrical and usually lined $ith refractory carbon brics

It is built on the foundation and serves as a collecting basin (reserv

for the molten iron and its accompanying slag. 8ear the bottom of the hearth is the tap hole through $hich the mo

iron is removed and about 1.! 1. m above the tap hole is the cin

notch through $hich the molten slag or cinder is $ithdra$n. The tap hole and cinder notch are sealed $ith plugs of baed cl

9hen the level of molten products approaches the tuyeres, the plu

are removed, the slag is dra$n off the cinder notch and the iron fr

the tap hole.

 verage depth ; ".5 m

!. Tu%eres

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<ocated peripherally near the top of the hearth and they are the inlets

that admit the heated air necessary for combustion and chemical

reactions. There are from 10 to 1= tuyeres spaced at e%ual intervals around the

circumference of the furnace and they are connected to the refractory+

lined bustle pipe that distributes the air from the hot blast stoves. Made of u or bron>e and have internal diameters of 100 to 15mm

?olume re%uired through the tuyeres is about !@00 m"'min at a

temperature of about 000 and a pressure of 1+1. g'cm!. The hot air blast reduces fuel costs and maes possible the highly

efficient operation of modern blast furnace.

#& MIDDLE SECTION1. #osh

/melting >one and the hottest part of the furnace

7xtends up$ard from the tuyere level and has an out$ard slope of 

about !00 and a height of about ".= meters. This slope or contraction tends to compensate for the volume

reduction of solid charge as it changes to molten state and descends

into the melting >one in front of the tuyeres.

The osh-t!"ere section o# the #!rnace is in the melting $one and eca!se o# the high temperat!re watercooled &! or ron$e plates

are !sed to protect the re#ractor" lining.  nother function of the slope in construction is to intensify combustion

and to provide a more rapid fusion of the charge.

!. Inwa  It is the lining of the stac from the top of the bosh to the top of the

furnace. 

It tapers from bosh up$ard until the diameter at the top is about "

meters less than the bosh diameter.  This part of the furnace receives the charge and contains it in its

descent through the preheating and hot >ones.. *227# /7TI48

1. Stac) and Charging Mechanis*

<ocated at the top of the stac and consists of a pair of vertic

operating cone+shaped bell valves that provide gastight charg

mechanism. In operation, the charge is carried by sip hoist to the top of

furnace and dumped in a hopper. The top bell then opens, permitting the charge to fall to the bottom

the bell. The top bell then closes and the bottom bell opens, allo$ing

charge to enter the stac.

A. 27#I2B7#< /7TI481. (eating Sto+es

The stoves for heating the air blast utili>e gases $ith fuel value

about 100 3T*'ft" that leave the top of the furnace. The stoves are essentially checer+$or systems of fire bric that

as heat exchangers bet$een the burning $aste gases and the

blast.   system of dust catchers and gas cleaners lins the blast furnace

the air heating stoves.

Blast Furnace Charge:

1. Ore Bematite (&e!4"  contains 50+=5- &e) and'or magnetite (&e"4)

− Bematite is used in greater proportion than magnetite

The ore pieces are usually less than 100mm diameter.

!. Co)e It is hard and porousC it contributes to the porosity of the charge an

strong enough not to crush under the $eight of the charge column. /i>e is usually 100mm in diameter and has the =mm material usua

screened out.

2urposes of the coe:

a. 2roduces the heat necessary for the furnace operation

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b. 2rovides the reducing agent (4) re%uired to remove the oxygen

from the oxide.c. 2hysically supports the $eight of the descending charges $hile

providing a porous path for the ascending gases.

". $u, <imestone or dolomite

/i>ed bet$een !5 and 100 mm

<imestone decomposed to a4 and 4! and the lime reacts $ith the

siliceous impurities in the ore and coe ash to form a fusible slag. The slag, in addition to removing $astes, also helps in the control of 

chemical properties (usually the / content) of the iron. &luxes must form slags of lo$ viscosity and lo$ density so that the

slag $ill settle freely do$n through the charge (because of its lo$

viscosity) and float in a distinct layer on the iron in the hearth (because

of its lo$ density).

The $eight of the charge minus the fuel is no$n as the furnace burden.

4re, flux and coe are deposited in alternate layers in the proportions

re%uired by the operation.

The operating furnace is ept filled up to the stoc line and ne$ material isadded at the same rate as that at $hich the slag and molten iron form in

the smelting >one. /ince the operation involves the chemical reaction bet$een the solid

charge and the rising gases in the furnace, the charge must therefore be

uniformly porous to permit a uniform flo$ of gas through the interstices.

Principle of Operation:

A& #eha+ior in $ront o! the Tu%eres

Bot blast enters the furnace through the tuyeres around

circumference of the top of the hearth at a velocity of !00+"00 m's aa pressure of !+ atm.

− The pressure is necessary to push the reducing gases throu

the solid burden and to overcome the top pressure of

furnace. The velocity of the blast clears a Drace$ayE of gas and rapidly hurtl

coe in front of each tuyere.

− The race$ays extend out$ards 1+! m.

The race$ays are bounded in front, at the sides and belo$ by a rat

firm regions of lump coe $hich has bypassed oxidation during

descent through the furnace.

− This coe extends do$n$ards into the iron pool and perha

even to the hearth brics.

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The race$ays are also bounded above by lump coe, but in this case it

is loosely paced due to the rapid ascent of race$ay gas bet$een the

pieces. The bottom+most pieces of coe in this >one periodically fall into the

race$ays to be consumed by the incoming air, and hence the $hole

bed is al$ays gradually moving do$n to be resupplied at the top $ith

coe from above. The main physico+chemical process in this region is transfer of heat

from the ascending race$ay gases to the descending pieces of coeand droplets of iron and slag.

#& Reactions in the (earth- Tu%ere Racewa%s and #osh  lmost all of the solid material in the hearth and bosh is coe.

<i%uid iron and slag percolate through this coe to form pools in the

bottom of the hearth. Auring this percolation:

− #eduction is finali>ed

− &e becomes saturated $ith

− (a4)".2!45, Mn4 and /i4!  are partially reduced to become

impurities (Mn, 2, /i) in the metal.

9hen oxygen first hits coe in the tuyere race$ays it reactsimmediately to form 4!. This 4! then reacts further $ith coe to

form 4:

F 4! → 4!

F 4!  → !4   ∆ G1800 K 0

=−142000kJ 

 t the temperatures of the hearth and lo$er bosh (1@00+!00 G), the

above reactions almost go to completion. The tuyere gases then rise through the Dactive coeE >one, transferring

heat to the descending coe and drops of iron and slag as they pass.

C& The $usion .one

The region of loose paced coe above the race$ays is bounded

top by a Dfusion >oneE consisting of alternate layers of coe a

softening and melting gangue, flux and iron.

− The layered structure persisted from the original charg

se%uence.

−

Importance of the inverted *+shaped region:

i. It, and the gas pressure belo$ it, tend to support the furn

burdenCii. Its coe layers tend to distribute reducing gas rapidly acr

the furnace.

− This effect arises because the softened and partially me

gangue, flux and iron are virtually impervious to gas flo$

that the ascending gases must pass hori>ontally throu

the coe slits in order to pass into the top of the furnace.

The main physical process in the fusion >one is the melting of me

and slag, maing use of the heat in the ascending bosh gas.

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The slag at this point consists mainly of gangue and flux oxides (i.e. it

does not yet contain coe ash $hich is for the most part released in

the tuyere >ones) The metal is almost devoid of iron oxide by the time it is fully molten

(i.e. at the lo$er edge of the fusion >one)

− but in any event, any iron oxide $hich it might contain $ill be

fully reduced during its descent through the coe percolators.

D& Reduction A/o+e the $usion .one The iron+bearing material in the fusion >one is principally metallic iron.

 bove this >one the burden begins to include solid iron oxide,

specifically $ustite, &e0.64, and thus at this point the burden consists

of alternate layers of coe and solid gangue and flux oxides, solid

&e0.64 and solid iron. The gas entering this mixed burden region has risen directly from the

coe bed beneath the fusion >one so that its carbonaceous component

is virtually all 4. T$o cyclic reactions tae place in this mixed burden region:

#eaction (1): $ustite reduction

4 F &e0.64 → 0.6 &e(s) F 4! C  ∆ H 298

0=−17000kJ 

#eaction (!): coe gasification

4! F → !4 C   ∆ H 2980=+172000kJ 

The coe gasification reaction is highly endothermic, and it causes

rapid cooling of the ascending gases. 9ustite reduction reaction is slightly exothermic but its heat release

does not compensate for the cooling effect of coe gasification, $ith

the net result that the temperature of the ascending gas falls maredly

in this region.

E& 0inetics o! the Co)e Gasi!ication Reaction The rate of coe gasification slo$s maredly as temperat

decreases. The result is that coe gasification comes to a virtual halt belo$ ab

1!00 G This means that the cyclic reaction sho$n above cannot tae pla

belo$ this temperature. 4nce the rising gases have been cooled belo$ 1!00 G, little more

is regenerated.  ll subse%uent reduction further up the shaft relies upon 4 produ

beneath the 1!00 G isotherm.

$& Reactions in Regions a/o+e the 123340 Isother*

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 s the gas continues its ascent above the 1!00+G isotherm, the 4

component continues to react $ith $ustite to form solid iron and 4!

thereby approaching e%uilibrium for the $ustite reduction reaction

H#eactio (1)  t 1!00 G, the e%uilibrium p4' p4!  ratio for the $ustite reduction

reaction is !." and the carbonaceous portion of the gas $ould contain,

0- 4 and "0- 4!  independent of furnace pressure and the

concentration of other gases (8!, B!, B!4) in the shaft.

 t the bottom portion of the constant temperature or Dthermal reserveE>one of the furnace, 4 gases do not cool during their ascent through

this region since #eaction (1) is slightly exothermic.

G& Reduction o! (igher O,ides The rising gas eventually becomes too $ea in 4 to reduce

significantly more $ustite to &e. Bo$ever, it is still strong enough to reduce to reduce &e"4 to $ustite

by: #eaction ("): Magnetite reduction

1.! &e"4 F 4 → ".@ &e0.64 F 4! C∆ G1200

0=−8000kJ 

 pCO

 pCO2

=0.43 C 4 ; "1-C 4! ; =6-

&or the blast furnace to be operating at a steady state, the amount of 

$ustite produced by #eaction (") must of course, be the same as the

amount of $ustite reduced by #eaction (!). There is in fact more than enough 4 rising from the $ustite'&e >one

to accomplish this purpose, because:a. 7ach mole of 4 converted to 4!  by reaction $ith &e"4

produces ".@ moles of &e0.64Cb. The 4 concentration re%uired for &e"4'&e0.64 reduction is

much less than that re%uired for &e0.64'&e reduction, i.e. "1-

versus 0-. This excess of 4 results in:

a. reation of a vertical region in the furnace $here the hig

oxides have already been reduced to $ustite but $here the g

cannot reduce significant %uatities of $ustite to &e.b. #estriction of the unreduced higher oxides to a small he

near the top of the furnace, about the top %uarter of the sh

This >one is only of sufficient vertical depth for its $us

production rate to e%ual the rate of $ustite reduction lo$e

the furnace, i.e. it is shallo$ enough so that the 4 pass

through the >one only partially reacted. The region $here the iron+bearing material is virtually all $ustite

referred to as Dche*ica reser+e 5oneE. 3ecause very little reaction taes place in this >one, it is also

region of roughly constant temperature. This region forms the top portion of the ther*a reser+e 5one.

#eaction (): Bematite reduction

"&e!4" F 4 → !&e"4 F 4! C∆ G1200

0=−105000kJ 

 pCO

 pCO2

<10−4

Recent Developments in Blast Furnace Practice:1. InJections of oil gas and po$dered coal in the tuyere >one save about !0-

coe costs.!. 4xygen enrichment of the air blast results in more favorable ore+to+coe rat". Krading and sintering of ore into pellets containing limestone provide a m

easily controlled charge and greater homogeneity.. The control of blast furnaces by computers speeds charge calculations a

provides more rapid charge modifications during operations.5. Bigher top pressures increase the density of gases and permit a greater m

flo$ of gas $ith no increase in gas velocity.=. To improve efficiency, lo$ grade ores (!0+"0- &e) are concentrated by dry

and calcining, a mild heating $hich drives off $ater and 4!, and sometimes given more extensive beneficiation treatments, involving roast

to magnetite, follo$ed by magnetic concentration, to improve their &e conte. <o$ grade ores are mixed $ith rich ores (=0- &e)

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STEELMA0ING  The process of removing impurities from pig iron (and iron and steel scrap)

and then adding certain elements in predetermined amounts to arrive at

the desired chemical composition and properties in the final metal.

Methods of /teelmaing:

1. rucible 2rocess

!. 3essemer onverter 2rocess". 4pen Bearth 2rocess

. 4xygen /teel Mainga. <+A processb. <+A 2rocessc. Galdo 2rocess

5. 7lectric &urnacea. rc &urnaceb. Induction &urnace

=. /pray #efining 2rocess

CRUCI#LE PROCESS" a melting and alloying process only rather than a purification process such

as modern steel maing. 7xcellent %uality tool steel are used to be made in crucible furnaces but

since each crucible can hold only a small amount of metal, the process is

slo$, expensive and has been largely replaced by the electric furnace

melting

#ESSEMER CON6ERTER PROCESS" Invented by Benry 3essemer $ho received an 7nglish patent in 1@5=.

2rincipally applied for maing lo$ steel+selp, free cutting stoc, $elded

pipe, etc. This process consists of blo$ing compressed air up$ard through a

refractory+lined pear+shaped vessel, no$n as converter , containing

molten pig iron.

The vessel has openings (tuyeres) at the bottom through $hich the

enters. 8early all the /i and Mn, most of the , and some of the &e are oxidi>

by oxygen in the air that is blo$n through the molten pig iron. The oxidation reaction furnishes the necessary heat for the process a

the oxidi>ed &e, /i and Mn form a slag.

Basic Operation:

Molten pig iron from the blast furnace forms the charge of the converter old steel scrap may be added to control (reduce) the temperature

8o flux is added

/lag consists of oxides formed by the oxidation of the metalloids in the

iron. Auring the first stage of the operation, as air is blo$n, /i and Mn

oxidi>ed:

!&e F 4! → !&e4 C   ∆ H =−128,000cal

!&e4 F /i → !&e F /i4! C  ∆ H =−70,200cal

&e4 F Mn → &e F Mn4 C∆ H =−26,800cal

  These exothermic reactions provide most of the heat for the operatand raise the temperature of the bath considerably.

 The /i4!, Mn4 and some &e4 combine to form the slag:

&e4 F /i4! → &e4./i4!

Mn4 F /i4! → Mn4./i4!

 fter most of the Mn and /i are gone, the begins to burn

&e4 F → &e F 4

&e4 F &e" → &e F 4

!4 F 4! → !4!

becomes 4 in the bath and the 4 escaping from the bath burns

4! at the mouth of the 3essemer converter thereby giving rise to a lo

flame. 9hen the flame drops, the blo$ is over. The blo$ must be stopped Just before the is completely burned or e

the &e itself $ill be oxidi>ed.

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 t the end of the blo$, Mn is added as ferromanganese, $hich is about

@0- Mn !0- &e, to the blo$n metal to remove the residual oxygen in

the metal. /ince Mn has a greater affinity for oxygen than &e, the follo$ing

reaction taes place:

&e4 F Mn → Mn4 ( 'oins the slag ) F &e

3esides being deoxidi>er, Mn is desulfuri>er also:

Mn F &e/ → Mn/ F &e

Aepending upon the desired content of the final steel, some may also

be added in the form of coe, hard coal or graphite.

Acid #esse*er Process +s #asic #esse*er Process

Acid #esse*er Process #asic #esse*er Process

<ined $ith !5+0 cm of sandstone

or mica schist cemented in place

$ith mixture of ganister and fireclay.

<ined $ith burned dolomite.

− <ining lasts less and costs more

Aoes not eliminate 2 and / from

the material

#emoves 2 and to some extent /

8eeds more expensive grade of ore dopted for only highly phosphoric ores

Most of the heat re%uired is

supplied by the oxidation of /i, the

content of $hich should be at least

!-, indicating an acid 2ig Iron.

/lag and temperature controls are more

difficult.

2ig iron content:

; .5-/i ; 1.0 1.5-Mn ; not more than 0.0-2 ; 0.10- Max./ ; 0.05- Max.&e ; remainder 

2ig iron content:

; ".5-/i ; 1-Mn ; 1-2 ; 1.- or more/ ; 0.0=-&e ; remainder 

<ime is charged together $ith the pig

iron and some of the heat re%uired is

supplied by the oxidation of 2, the initial

content of $hich should be at least 1.-

Acid #esse*er Process #asic #esse*er Process

4peration follo$s the basic

operation discussed above

4peration is divided into ! blo$s:

1& $ore4/ow

− <asts for about 10+1! minutes and

corresponds to the ordinary blo$

of the acid process in $hich /i,

Mn, and are eliminated.

− The end of the blo$ is denoted bythe dropping of the flame

2& A!ter4/ow

− Taes place after the fore+blo$

and continues for "+5 minutes to

remove the 2

− Aense bro$n fumes of &e oxide

smoe are emitted during this

stage, since it is not possible to

oxidi>e 2 $ithout oxidi>ing &e.

2 cannot be removed earlier because

lime cannot assimilate the 2!45 until it

has become a fluid slag and &e4 is

re%uired to mae such a slag $ith a4

The &e4 content cannot rise until the

content is lo$.

#eactions that remove 2 and /:

2 F 54! → !2!45 C LB ; +"",@00 cal

!&e"2 F 11 4 → =&e4 F 2!45

"&e4 F 2!45 → (&e4)".2!45

(&e4)"2!45 F "a4 → (a4)".2!45 F "&e4

&e/ F a4 F → &e F 4 F a/

&e/ F " 4 → &e4 F /4!

The slag is then removed and the meta

is deoxidi>ed $ith Mn as $ell as / in

removed:

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&e4 F Mn → &e F Mn4

&e/ F Mn → &e F Mn/

OPEN (EART( PROCESS"

  process invented by

Garl 9ilhelm /iemens $hich is based on Regenerati+e Princi7e  of 

heating. #egenerative principle of heating involves preheating the fuel gas and air 

prior to their combustion in the furnace by periodically reversing the

directional flo$ of the gases such that the heat left by out+going gases is

trapped and used to preheat incoming gases. This help increase the

furnace temperature.

Basic Operation:

/crap metal, pig iron and flux and other alloying elements, are charged

into the furnace through charging doors. Beating is done by burning gaseous fuel.

The hot gases formed pass over the hearth to its opposite end, thus,

metal charge supported on the hearth is openly exposed to the flames a

is converted into molten metal.  side from being directly exposed to the flames, metal charge is a

heated by the radiation from the $alls and lo$ hot ceiling of the furnace  fter passing over the hearth, the products of combustion pass thro

one checer chamber and heat it. The directions of the flo$ of the gaseous fuel and air are then revers

thus preheating the fuel and air before they reach the hearth. The aiheated to about !00o& before it reaches the hearth.

This regenerative system speeds up the melting of the metal and develo

temperatures enough to melt the steel due to the alternate heating of

checers $hich results to the preheating of the fuel and air.

Acid O( $urnace +s #asic O( $urnace

Acid O7en (earth $urnace #asic O7en (earth $urnace

*ses acid furnace lining such

as silica firebrics and utili>es

acid slags for metal refining

 cid refractories are cheaper 

*ses a basic lining such as dolomite and crush

magnesite.

3asic refractories are more costly

Metal charge should have lo$

2 and pig iron and scrap

should have lo$ /

<imestone is re%uired to eep

the slag fluid.

Metal charge consist of pig iron and scrap iron

<imestone is needed to form slag

Iron ore may be added to burn excess if

present

/teel scrap and pig iron of lo$ grades can be

charged for removal of impurities such as exce

2 and /

3ecause of its simple

operation and care in

selection, it is often regarded

as superior to the basic open

hearth process

2roduces cheaper structural steels for a $ide

variety of $or.

  fairly expensive process

ho$ever, and is used for

maing high %uality and lo$

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alloy parts such as axles, $ire

ropes, springs, castings, and

piston rods

#asic O7erations

Acid O7en (earth $urnace #asic O7en (earth $urnace

  non+phosphoric solid pig iron is

charged first and then follo$ed by

the steel scrap

4xidation occurs during

melting, and a slag of

manganese oxide and silica

together $ith iron oxide from

the metal charge is formed.

Iron oxide from the metal scrap$ill also be formed during

melting. Iron oxide attacs the

siliceous hearth

 fter melting, iron ore (&e!4") or

millscale (&e"4  a purer form of

iron oxide) is added to continue

and complete the oxidation

 dditions of lime are also made to

control the slag.

<imestone is charge first, follo$ed by ore,

steel scrap and then solid pig iron.

9hen the temperature in the furnace

reaches 1!00o, the molten pig iron is

poured in and a rapid reaction begins

bet$een the lime and ferrous oxide of the

charge and the silicon, manganese,

phosphorus and carbon of the metal:

/i F !&e4 → /i4! F !&eC ∆B ; +0!00 cal

Mn F &e4 → Mn4 F &eC ∆B ; +!=@00 cal

!2 F 5&e4 → 2!45 F 5&eC ∆B ; +5=00 cal

F &e4 → 4 F &eC ∆B ; "=00 cal

In about t$o hours the charge is practical

molten. t this stage molten pig iron is

added to the charge

Auring the melting stage, most of themanganese and silicon get oxidi>ed by th

oxygen in the ore (&e4) and go to the slag

 t the end of the melting stage, ore /oi 

begins:

#eaction (d) taes place bet$een the

oxygen of the ore and the carbon of

molten pig iron. The evolution of 4 causes a violent

agitation of the metal as it escapes th

bath.

  significant purification of the charge

begins $ith ore boil.

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Acid O7en (earth $urnace #asic O7en (earth $urnace

3efore the ore boil is completed, the i*e /oi 

begins $hich is caused by the decomposition of

the limestone into lime and 4!:

a4" → a4 F 4!

4! F → !4

4 stirs the bath and brings lime to the slag. The

lime removes the phosphorus by the follo$ingreaction:

!2 F 5&e4 F "a4 → "a4.2!45 F 5&e

/ome sulfur is also removed:

&e/ F a4 → a/ F &e4

3oiling causes oxidation of a large part of the

metalloids $hich results to the formation of a

layer of basic slag on top of the molten metal.

 fter boiling has subsided, $oring period

follo$s, $hich consists of: #emoval of phosphorus

 dJustment of carbon content

 dJusting the temperature of the bath to a

point suitable for tapping the finished steel

Auring the $oring period, the bath is oxidi>ed by

the slag:

3oth the metal bath and the slag contain &e4

2art of the &e4 in the slag is continually

oxidi>ed to &e!4" by the flame gases, and

the &e!4" is reduced to &e4 by the carbon

and other elements in the metal bath. Thus

the slag serves as carrier of oxygen from the

furnace atmosphere into the bath.

9hen the heat of steel is finished, the molten

metal is tapped by opening the tap hole and th

steel runs into the ladle.

O8YGEN STEELMA0ING"

 

4xygen is used rather than air 

1& #asic O,%gen Proce

9#OP: or Li

Donawit5 9L4D: Process"  This process is fast and since the reactions are exothermic, no f

is needed  *sed largely for the treatment of basic pig iron fairly lo$

phosphorus (0.!5-)

Basic Operation:

 

The charge consists of a considerable %uantity of molten pig iron an

limiting amount of steel scrap.  <ime is added in the converter and sometimes fluorspar to increa

the slag fluidity.

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  The $ater+cooled oxygen lance is then lo$ered into the mouth of the

converter to a position about a meter above the surface of the charge

and then high purity oxygen is blo$n under considerable pressure.    very rapid reaction taes place bet$een the oxygen and the

elements of the molten pig iron (, /i, Mn and &e), forming oxides.  2art of the iron oxide reacts $ith the flux to form a basic slag, $hile the

remainder is mixed $ith the bath, through turbulence, and oxidi>es

impurities such as Mn and /i.

The oxidi>ed /i, Mn and 2 go into the slag that $as formed by theaddition of lime.

  and 2 are last to get oxidi>ed.

 

The chemical reaction of oxygen and fluxes $ithin the bath refines pig

iron and scrap into steel. The refining process approaches the end $ith

the oxidation and removal of the impurities such as , Mn, 2, and /i.  The oxidation reactions being exothermic provides more than enough

heat that could bring the temperature to above !000o. To prevent the

steel from getting too far above its melting point, cold scrap steel is

charged.<arge %uantities of 4 gas and fumes are evolved during oxygen

blo$ing and a long 4 flame forms.

  *pon completion of the refining process, i.e., $hen carbon flamedrops, the oxygen lance is $ithdra$n, the furnace is tilted and the steel

is tapped through a hole in the side near the top.

2& Lin54Donawit5 Ar/ed Center 9L4D4A4C: Process"  can treat pig iron $ith up to !.0- phosphorus

  consists of inJecting po$dered lime together $ith the oxygen Jet.

 

this helps remove more phosphorus from the molten metal

before the re%uired carbon content is reached.

Basic Operation:

  Molten pig iron and scrap are charged first, then the lime is added

  4xygen lance is lo$ered into the vessel and a Jet of high pressure pure

oxygen is introduced 

/i and mn burn first. Then the charge boils due to the oxidation of c.

  This first stage last in about 10+1! minutes and then the slag is pou

out.  The temperature of the molten metal, if necessary, is controlled by

addition of scrap.  The second stage of the process is commenced by the inJection

po$dered lime into the converter together $ith the oxygen Jet throu

the oxygen lance.  The lime goes in $ith the oxygen to the center of the oxida

reactions $here the temperature is extremely high and &concentration is high.

  The lime is continuously added to produce a strongly dephosphori>

slag in the reaction >one.  in this $ay, phosphorus is effectively removed before the re%ui

carbon content is reached.   s the desired composition of steels is reached, the metal is tap

and poured into moulds.

;& 0ado Process  Aeveloped in /$eden by 2rof. Galling

Basic Operation:

  harge cons

of molten pig

and scrap.

  /crap

proportion m

be as high as

compared $ith 3essem

converter since it has

higher operatingtemperature.

The scrap acts

coolant to reduce the h

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temperature produced during the blo$, but at the same time

improving thermal efficiency of the process.

  Iron ore may also be added for the same purpose as the steel

scrap. 

The converter is tilted further to another position $here lime and ore

are added.   fter being charged, the converter is tilted to the blo$ing position at an

angle !0o to the hori>ontal.

Purpose of rotation:a& to ensure efficient mixing and better slag+metal contact and

reactions/& to provide a large surface area of ironc& to oxidi>e impurities easilyd& to stir the bath for heat transfer thus preventing refractories

from being locally overheated by the 4 flame 

The chemical reactions taing place in this process are fundamentally

similar to those taing place in <+A process.  The use of oxygen allo$s the simultaneous removal of and 2 from

the pig iron containing 1.@5- 2.

ELECTRIC ARC $URNACE 9EA$:  It can melt up to 100- steel scrap since it utili>es an external source of 

energy (electric current)

  It can produce a $ide range of steels

1& Direct Eectric Arc $urnace 

Kenerally used for the production of high %uality carbon steels a

alloy steels

  It consists of a heavy steel shell lined $ith refractory bric and silica

acid lined furnaces and magnesite for basic lined furnaces.   Acid lining  is preferred $hen steel scrap containing lo$ s and

available so that removal of these elements is not re%uiredC

heats are produced much faster.

  Basic lining  is used $hen inferior steel scrap containing significamounts of s and p is availableC heats tae longer time than in a

lined furnaces.

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  The roof of the direct arc furnace consists of a steel roofing in $hich silica

brics are fixed in positions.  It may be charged either from the charging door $hich also serves for 

removing slag from the top of the molten metal or from the furnace roof 

$hich is made to lift off and s$ing clear of the furnace.  Aepending upon $hether it is a t$o phase or three phase electric furnace,

t$o or three graphite electrodes are inserted through the holes in the roof 

into the furnace.

 

7lectrodes can be raised up or do$n  7lectrode guides placed on the furnace roof are $ater cooled to

dissipate damaging heat. 

Basic Operation:

The interior of the furnace is preheated before placing the metal charge.

 fter preheating, the electrode pieces placed on the hearth are removed.

The furnace is charged $ith pig iron and steel scrap

The method of maing steel is the same method as described for open

hearth furnace. 4nce the cold charge is placed on the hearth of the furnace, electric arc is

dra$n bet$een the electrodes and the surface of the metal charge by

lo$ering the electrodes do$n till the current Jumps the gap bet$een theelectrodes and the charge surface.

2& (igh $re<uenc% Induction $urnace 9Coreess t%7e:   pplied for melting regular and special alloys and high %uality

steels in small %uantities.

 

s

o

refractory crucible placed centrally inside $ater cooled copper c

and paced into position by ramming dry refractory tightly bet$

the crucible and the copper coil $hich is pre+covered $ith

refractory dried into a hard mass.

Basic Operation:

/teel scrap is placed in the furnace as metal charge

  high fre%uency current is passed through the $ater cooled copper c

$hich act as the primary of a transformer and the metal charge becom

the secondary. Beavy alternating secondary currents induced in the metal charge

electromagnetic induction create heat because the metal charge crea

resistance to the passage of secondary currents. The secondary current associates $ith it a magnetic field $hich provide

magnetic stirring action on the molten metal, thereby speeding up

melting process and mixes up the metal charge uniformly.

Keneral dvantages of 7lectric rc &urnace:

a. *nlimited %uantity of scrap may be melt

b. 7asy temperature controlc. Aeep desulfuri>ationd. 2recise alloying

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LADLE RE$INING 9LADLE METALLURGY- SECONDARY RE$INING:

1& 6acuu* Lade Degassing *tili>e the reaction of the deoxidation by carbon dissolved in steel

by the follo$ing reaction:[C ]+ [O ]→ {CO }

$here H dissolved in li%uid steelC N + gaseous The method involves decreasing the partial pressure of 4 such

that the e%uilibrium is shifted to$ards the carbon oxidation

resulting to the formation of bubbles of carbon monoxide $hich is

then removed by the vacuum system. In addition to deoxidation, hydrogen dissolved in the steel is also

removed. Bydrogen diffuses into the 4 bubbles and the gas is

then evacuated by the vacuum pump. /tirring of the molten steel caused by the 4 bubbles also results

in the removal of nonmetallic inclusions $hich agglomerate, float

up and absorbed by the slag. 4 bubbles also favor the process of floating and removal of 

nitride inclusions and gaseous nitrogen.

T%7es o! 6acuu* Lade Degassing"

a& RECIRCULATION DEGASSING 9R4(:

onsists of a vacuum chamber having t$o snorels connected to the

chamber bottom. 4ne of the snorels is e%uipped $ith pipes

supplying  rgon. The snorels of the vacuum chamber are immersed into the ladle $ith

molten steel. <i%uid metal fills the chamber to a level determined by the atmospheric

pressure (.!ft'1."m).  rgon bubbles floating up in one of the snorels (up+leg) force the melt

rise in the snorel. Through the second snorel (do$n+leg) the molten

steel flo$s do$n bac to the ladle producing circulation. The circulation

rate may reach 150+!00 t'min. The recirculation degassing vacuum chambers are usually e%uipped $it

addition hoppers, through $hich alloying elements or'and desulfuri>atio

slag may be added.

3enefits of #B

• Bydrogen removal (degassing)

• 4xygen removal (deoxidation)

• arbon removal (decarburi>ation)• /ulfur removal (desulfuri>ation)

• 2recise alloying

• 8on+metallic inclusion removal

• Temperature and chemical homogeni>ation

/& RECIRCULATION DEGASSING '= O8YGEN TOP LANCE 9R(4O

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In this method a conventional

#ecirculation degassing (#B) vessel (chamber) is e%uipped $ith a vertical

$ater cooled lance for blo$ing oxygen on the molten steel surface. 4xygen intensifies the reaction >C? @ >O? BCO resulting in fast and

effective decarburi>ation.

4xygen also oxidi>es phosphorus lie in 3asic 4xygen 2rocess (342) orin oxidi>ing slag stage in 7lectric+arc furnace.

4xidation reactions have also heating effect therefore the treated metal

may be heated to a re%uired temperature $ithout any additional energy

source.

3enefits of #B+43:

• Bydrogen removal (degassing)

• &ast carbon removal (decarburi>ation)

• 2hosphorus removal (dephosphori>ation)

• /ulfur removal (desulfuri>ation)

• #eheating (precise alloying)

• 8on+metallic inclusions removal

• Temperature and chemical homogeni>ation

c& LADLE DEGASSING 96D- TAN0 DEGASSING:

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The ladle $ith molten steel is placed into a vacuum chamber. The ladle is

e%uipped $ith a porous refractory plug mounted in the ladle bottom.

Through the plug argon is supplied during vacuum treatment.   hopper $ith vacuum loc on the chamber cover is integrated for adding

alloying elements and'or slag components. The reaction H F H4 ; 4N starting in the steel under vacuum conditions

causes stirring, $hich is intensified by argon blo$n through the bottom

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

the steel. Aesulfuri>ing slags possessing high sulfur solubility are used in

this process.  rgon and 4 bubbles also favor the process of floating and removal of

nitride inclusion and gaseous nitrogen.

3enefits of <adle Aegassing:

• Bydrogen removal (degassing)

• 4xygen removal (deoxidation)

• Aeep sulfur removal (desulfuri>ation)

• arbon removal (decarburi>ation)

• 2recise alloying

• 8on+metallic inclusions (oxides and nitrides) removal• Temperature and chemical homogeni>ation

d& 6ACUUM O8YGEN DECAR#URI.ATION 96OD:

The chamber is e%uipped $ith a vertical $ater cooled lance for blo$

oxygen on the molten steel surface.

*sed for manufacturing stainless steels.

4xidation of li%uid steel components under vacuum differs from tha

normal pressure because oxygen is consumed mainly by the reaction

F H4 ; 4N rather than by oxidation of chromium, $hich is the m

constituent of stainless steels. Bence this process allo$s decarburi>at

of steel $ith minor chromium losses. 4xidation reactions have also heating effect therefore the treated me

may be heated to a re%uired temperature $ithout any additional ene

source.  fter decarburi>ation (oxidation) stage is completed, deoxidi>ers

added to the steel in order to remove excess oxygen.

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Aesulfuri>ing slag is then added to the molten surface. /tirring of the melt

and the slag caused by argon blo$n through the porous bottom plug

results in deep desulfuri>ation.

3enefits of ?4A:

• Aeep decarburi>ation

• <o$ losses of r in treatment of stainless steels

• Bydrogen removal (degassing)

• /ulfur removal (desulfuri>ation)

• 2recise alloying

• #eheating

• 8on+metallic inclusions (oxides and nitrides) removal

• Temperature and chemical homogeni>ation

e. LADLE $URNACE *sed for  

refining a

$ide variety

of steels in

$hich

degassing is

not re%uired.

The ladle is transported to the <& stand $here it is placed under a co

e%uipped $ith three graphite electrodes connected to a three+phase

transformer. The ladle bottom has a porous refractory plug, $hich is connected to

argon supply pipe at the <& stand. The <& stand is also e%uipped $ith an addition hopper mounted on

cover and a lance for inJection of desulfuri>ing agent. &umes formed during the operation are extracted through the cover.

Molten steel treated in <& is covered by a layer of desulfuri>ing slag.

Auring the treatment process, argon is blo$n through the bottom poro

plug providing continuous metal stirring. /tirring results in distribution

heat produced by the arcs, chemical homogeni>ation and desulfuri>at

of the steel by the slag.

 lloying elements and'or slag components may be added through hopper.

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If deep desulfuri>ation is re%uired active desulfuri>ing agents are inJected

into the melt through the inJection lance or in the form of cored $ire. 3esides refining operations, <& may serve as a buffer station before

continuous casting.

3enefits of <&:

• Aeep desulfuri>ation

• ontrollable reheating by electric po$er 

•  lloying

• Temperature and chemical homogeni>ation

• 8on+metallic inclusions removal

f. LADLE DESUL$URI.ATION

ons

of inJecti

desulfuri>ing agents (a, Mg, casi, cac!, caf !Fcao) to a molten steel to

effectively remove the sulfur.

InJection methods usually combine supply of a disperse desulfuri>ing

agent (po$der) $ith stirring by argon blo$ing.

  ladle $ith deoxidi>ed molten steel is transported to the inJection stand

$here it is placed under a cover, through $hich the inJection lance may

lo$er and immerse into the melt.

/teel treated in the stand is covered by a layer of desulfuri>ing slag hav

high solubility of sulfur and capable to absorb sulfides formed as a resu

of active agents inJection.

Aesulfuri>ation agents are inJected in argon stream. rgon bubbles

produce stirring of the molten steel and the slag promoting desulfuri>ati

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/tirring also provides thermal and chemical homogeni>ation of the melt.

9hen desulfuri>ing agents are inJected into molten steel in form of a cored

$ire containing po$der of desulfuri>ing agent stirring by argon bubbling

from the porous plug mounted in the ladle bottom is used.

&umes formed during the operation are extracted through the cover.

InJection of desulfuri>ation agents allo$s to achieve ultra+lo$

concentrations of / in steel (0.000!-)

g. LADLE4TO4MOLD DEGASSING

  method in $hich the mold is placed in a vacuum chamber.

The molten steel is poured from a tundish attached to the cover of t

chamber.

The tundish is continuously filled $ith the melt poured from the ladle.

The steel stream boils $hen it is falling to the mold cavity in vacuum d

to the deoxidation reaction H F H4 ; 4N Bydrogen dissolved in steel diffuses into the 4 bubbles and the gas

then evacuated by the vacuum pump.

Intensity of the deoxidation and degassing during <adle+to Mold pourin

indicated by the angle, at $hich the melt stream opens as a result of

bubbles formation.

Classification of Carbon Steels based on the degree of deoxidation:

1& 0ied stees  ompletely deoxidi>ed steels

  /olidification of $hich does not cause formation of 4.

Ingots and castings have homogeneous structure and no gas poro

(blo$holes)

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2& Se*i4)ied stees 

Incompletely deoxidi>ed steels containing some amount of excess

oxygen $hich forms carbon monoxide during the last stages of 

solidification.

;& Ri**ed stees

  2artially deoxidi>ed or non+deoxidi>ed lo$ carbon steels evolvingsufficient amount of carbon monoxide during solidification.

 

Ingots of rimmed steels are characteri>ed by good surface %uality and

considerable %uantity of blo$holes.

CLASSI$ICATION O$ STEELS #Y COMPOSITION

Car/on stees

<o$ carbon steels ( O 0.!5-)C Medium carbon steels ( ;0.!5- to 0.55-)C

Bigh carbon steels ( P 0.55-).

Aesignation system:

 merican Iron and /teel Institute (I/I) together $ith /ociety of utomotive

7ngineers (/7) have established four+digit ($ith additional letter prefixes)

designation system:

SAE 1888

$irst digit 1 indicates carbon steel (!+6 are used for alloy steels)C

Second digit indicates modification of the steel.

0 + 2lain carbon, non+modified

1 + #esulfuri>ed

! + #esulfuri>ed and rephosphori>ed

5 + 8on+resulfuri>ed, Mn over 1.0-

Last two digits indicate carbon concentration in 0.01-.

xample" /7 10"0 means non modified carbon steel, containing 0."0- of

carbon.

  letter prefix before the four+digit number indicates the steel maing technolog

  + lloy, basic open hearth

3 + arbon, acid 3essemer 

+ arbon, basic open hearth

A + arbon, acid open hearth

7 + 7lectric furnace

7xample: I/I 310!0 means non modified carbon steel, produced in acid

3essemer and containing 0.!0- of carbon.

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Ao% stees

<o$ alloy steels (alloying elements @-)C9

Bigh alloy steels (alloying elements P @-).

 ccording to the four+digit classification /7+I/I system:

$irst digit indicates the class of the alloy steel:

!+ 8icel steelsC

"+ 8icel+chromium steelsC

+ Molybdenum steelsC

5+ hromium steelsC

=+ hromium+vanadium steelsC

+ Tungsten+chromium steelsC

6+ /ilicon+manganese steels.

Second digit indicates concentration of the maJor element in percents (1 means

1-).

Last two digits indicate carbon concentration in 0,01-.

7xample: /7 51"0 means alloy chromium steel, containing 1- of chromium and

0."0- of carbon.

CLASSI$ICATION O$ STEELS #Y APPLICATION

Stainess stees"

 I/I has established three+digit system for the stainless steels:

!QQ series chromium+nicel+manganese austenitic stainless steelsC

"QQ series chromium+nicel austenitic stainless steelsC

QQ series chromium martensitic stainless steels or  ferritic stainless steelsC

5QQ series lo$ chromium martensitic stainless steelsC

Too and die stees"

Aesignation system of one+letter in combination $ith a number is accepted for t

steels.

The letter means:

9 + 9ater hardened plain carbon tool steelsC

4 + 4il hardening cold $or alloy steelsC

  + ir hardening cold $or alloy steelsC

A +Aiffused hardening cold $or alloy steelsC

/ /hoc resistant lo$ carbon tool steelsC

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T Bigh speed tungsten tool steelsC

M + Bigh speed molybdenum tool steelsC

B Bot $or tool steelsC

2 2lastic mold tool steels.

CLASSI$ICATION O$ CAST IRONS

1. 'hite cast irons 

hard and brittle, highly $ear resistant cast irons consisting

of pearlite and cementite.

produced by chilling some surfaces of the cast mold. hilling prevents

formation of  Kraphite during solidification of the cast iron.

*sed to mae brae shoes, shot blasting no>>les, mill liners, crushers,

pump impellers and other abrasion resistant parts.

!. Gre% cast irons 

produced at slo$ cooling and consisting of ferrite and dispersed

graphite flaes.

possess high compressive strength, fatigue resistance and $ear

resistance.

presence of graphite impart them very good vibration dumping

capacity.

*sed to mae gears, fly$heels, $ater pipes, engine cylinders, brae

discs, gears.

". Maea/e cast iron 

produced by heat treatment of $hite cast irons and consisting of ferr

and particles of free graphite.

they have good ductility and machinability. &erritic malleable cast iro

are more ductile and less strong and hard, than pearlitic malleable c

irons.

*sed to mae parts of po$er train of vehicles, bearing caps, steerin

gear housings, agricultural e%uipment, railroad e%uipment.

. Noduar 9ductie: cast irons 

grey cast iron, in $hich graphite particles are modified by magnesiu

added to the melt before casting. 

consists of spheroid nodular graphite particles in ferrite or pearlite

matrix.

possess high ductility, good fatigue strength, $ear resistance, shoc

resistance and high modulus of elasticity.

*sed to mae automotive engine cranshafts, heavy duty gears,

military and railroad vehicles.

DAY ! "#O$ A$D %&EE' (E&A'')#*Y ++ Prepared ,y- Prof. annie /oy &. #esa,al PA*E 2