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Processing ofProcessing of
Iron and SteelIron and Steel
CHAPTER 1CHAPTER 1
Iron OreIron Ore
is mined from the groundis mined from the ground
it is a rock that may contain only 30% ofit is a rock that may contain only 30% of
iron.iron.
is in chemical compound or the iron isis in chemical compound or the iron is
combined with oxygen or sulfur.combined with oxygen or sulfur.
is found intermixed in rock, gravel, clay,is found intermixed in rock, gravel, clay,sand or even mud.sand or even mud.
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The iron ore is chemical compoundThe iron ore is chemical compound
with oxygen or sulfur.with oxygen or sulfur.
Sulfur Oxygen
Iron
Silicon IronSulfur Oxygen
Iron
Silicon Iron
Sulfur
Sulfur Oxygen Iron
Silicon Iron
Oxygen Iron Sulfur
Types of iron oreTypes of iron oreIron ore Iron Compound % iron
Hematite Fe2O3 70%
Magnetite Fe3O4 65%
Siderite FeCO3 48%
Limonite 2Fe2O3 H2O 52% 66%
Taconite Various 22% - 40%
Hematite
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Iron ore is found intermixed inIron ore is found intermixed in
rock, gravel, clay, sand or mudrock, gravel, clay, sand or mud
Rock Gravel
Mud
ClayRock
Iron
Oxygen
Iron
Oxygen
Iron Ore ProcessingIron Ore ProcessingCrushing the stone by Gyratory crusher - (smaller pieces)
Milling process in the roll mill or ball mill (fine particles)
Separation process by magnetic separator
Floatation process
Impurities bubble to the top and are skimmed awayand leaving an iron rich mixture
The particle is immersed in a liquid
Iron ore (~70% iron)
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Iron Ore ProcessingIron Ore Processing(Explanation)(Explanation)
First, the large chunks of stone are brokenFirst, the large chunks of stone are brokenup by giant crushers such as Gyratoryup by giant crushers such as Gyratorycrusher.crusher.
These smaller pieces are then fed into rollThese smaller pieces are then fed into rollmill or rod mill and ball mill.mill or rod mill and ball mill.
The mill rotate and hardened steel rollersThe mill rotate and hardened steel rollersor ball rotate with the ore and steadilyor ball rotate with the ore and steadilypound it into finer particles.pound it into finer particles.
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After being crushed and milled, the rockAfter being crushed and milled, the rock
particles become so fine that they feel like sugarparticles become so fine that they feel like sugar
or dry sand.or dry sand.
In this condition the valuable iron ore particlesIn this condition the valuable iron ore particles
can be separated by magnetic separator fromcan be separated by magnetic separator from
others.others.
The strong magnetic will separate the iron oreThe strong magnetic will separate the iron ore
from others particles during separator rotates.from others particles during separator rotates.
Iron Ore ProcessingIron Ore Processing
(Explanation)(Explanation)
Next the powder goes to flotation process,Next the powder goes to flotation process,
where the particles are immersed in a liquid.where the particles are immersed in a liquid.
Impurities bubble to the top and are skimmedImpurities bubble to the top and are skimmed
away and leaving an iron rich mixture.away and leaving an iron rich mixture.
After magnetic separation and flotation the oreAfter magnetic separation and flotation the ore
may contain as much as 70 % iron.may contain as much as 70 % iron.
Iron Ore ProcessingIron Ore Processing(Explanation)(Explanation)
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Steel ProcessingSteel Processing
There are 2 basic steps in steelThere are 2 basic steps in steel
processing:processing:
Step 1Step 1 -- Iron ore is converted to pig ironIron ore is converted to pig iron
Step 2Step 2 -- Pig iron is made into steelPig iron is made into steel
Steps for Making SteelSteps for Making Steel
Blast
FurnaceSteel
Making
FurnaceIron ore
Pigiron
Steel
Step 1 Step 2
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The Blast FurnaceThe Blast Furnace
Blast FurnaceBlast Furnace
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The Blast FurnaceThe Blast Furnace
A blast furnace may be more than 250A blast furnace may be more than 250
feet high, taller than 12feet high, taller than 12--storey buildingstorey building
and 30 feet in diameter.and 30 feet in diameter.
Fire resistant brick lines the inside wall ofFire resistant brick lines the inside wall of
the blast furnace.the blast furnace.
PIG IRON PROCESSINGPIG IRON PROCESSING
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The blast furnace is charged with iron ore,The blast furnace is charged with iron ore,
limestone, and coke.limestone, and coke.
A blast of preheated air burns the coke,A blast of preheated air burns the coke,
producing heat to melt the iron, whichproducing heat to melt the iron, which
falls to the bottom of furnace.falls to the bottom of furnace.
C + OC + O22 = CO= CO22 + Heat+ Heat
COCO22+ C = 2CO+ C = 2CO
Reaction at high temperature, so Carbon dioxide will reduce to carbonmonoxide as below:
The molten limestone combines with mostThe molten limestone combines with mostof the impurities in the ore to form a slag,of the impurities in the ore to form a slag,which separates from the liquid ironwhich separates from the liquid ironbecause it is lighter and floats.because it is lighter and floats.
The liquid iron and the liquid slag areThe liquid iron and the liquid slag are
removed periodically from the bottom ofremoved periodically from the bottom ofthe furnace.the furnace.
FeS + CaO + C= CaS + FeO + COFeS + CaO + C= CaS + FeO + CO
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The liquid iron is poured into mold to formThe liquid iron is poured into mold to form
what is known as pig of iron.what is known as pig of iron.
Pig iron is hard and brittle.Pig iron is hard and brittle.
It contains considerable amounts ofIt contains considerable amounts of
dissolved carbon, manganese, silicon,dissolved carbon, manganese, silicon,
phosphorus and sulfur.phosphorus and sulfur.
Step 1: Iron OreStep 1: Iron Ore Pig IronPig IronIron ore + Limestone + Coke
(Charcoal) are put into the furnaceA blast of preheated air burns the
coke and produce the heat
Melting process of ironMelting iron falls to the bottom
Molten limestone mixed withimpurities in ore SLAG (lighter
and float)
Molten iron and molten slag areremoved from the bottom
Iron is poured into mouldPIG IRON
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Air
Ore+
Limestone+
Coke
Slag
Iron
Air
Cast into pig iron
In the Blast FurnaceIn the Blast Furnace
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Pig IronPig Iron
Contains considerable amounts ofContains considerable amounts of
dissolved 4dissolved 4--5% carbon, manganese,5% carbon, manganese,
silicon, phosphorus and sulfur.silicon, phosphorus and sulfur.
Hard and brittleHard and brittle
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PIG IRONPIG IRON
There are several types ofThere are several types of
converter/furnace that used in makingconverter/furnace that used in making
steel:steel:
Open Hearth FurnaceOpen Hearth Furnace
Basic Oxygen FurnaceBasic Oxygen Furnace
Electric Arc FurnaceElectric Arc Furnace
Step 2: Pig IronStep 2: Pig Iron SteelSteel
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Open Hearth FurnaceOpen Hearth Furnace
The oldest converter.The oldest converter.
Basically a large bowl made of firebrick.Basically a large bowl made of firebrick.
Molten iron
Hot Air Hot Air
Steel is cast into ingot
OHF ProcessingOHF Processing
Pig iron and scrap metal are putinto the furnace
Hot air is blown across the surfaceand produce the heat
Excess carbon and impurities areburned off
Refining process
At the end of the refining process,
desired amount of carbon oralloying elements are added
Molten steel is drawn and cast intoingots
STEEL
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Basic Oxygen FurnaceBasic Oxygen Furnace
It is a rapid process (10 times faster thanIt is a rapid process (10 times faster than
OHF).OHF).
Lower cost.Lower cost.
Molten iron
Oxygen
Lance
Pig iron + scrap metal
BOF ProcessingBOF Processing
Pig iron + scrap are dumped intothe furnace vessel
A lance is lowered from above intothe charge
Pure oxygen is blown through thelance
The oxygen burns off the carbonvery rapidly
Once the carbon is removed, the
lance is withdrawn
Desired amount of carbon and
alloying elements are added
Steel is cast into ingotSTEEL
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Electric Arc FurnaceElectric Arc Furnace
It requires about 440 kW/ton of steel.It requires about 440 kW/ton of steel.
Capacity range: 1Capacity range: 1 100 tons100 tons
No air is required for melting processNo air is required for melting process
Materials Outlet
Molten iron
EAF ProcessingEAF Processing
Pig iron + scrap are loaded intothe furnace
Electrode are lowered from the topof the furnace close to the iron
An arc is struck to the iron to meltthe iron and burn off the carbon
Steel is cast into ingot
STEEL