Chapter 2

1. Chapter 2:
Ferrous Metals
2.0 Iron Productions
1. Iron ores are main material in iron ingot production.
2. In mining process, the iron ore are in pure state. It also found
along with other substances such as oxide, sulphade, sulphur,
silicon, etc.
2.1 Types of Irons
2.2 Iron Ores Characteristics
1. GRADE – containing as much as possible iron oxide
2. COMPACTABILITY – not too compact or too brittle
3. PURITY – containing as less as possible impurities
4. SIMILARITY – containing similar composition to one another
2.3 Iron Production Process
Blast Furnace
1. It’s divided into 2 parts :
i. combustion chamber/ stove where the hot air from, blast into
the furnace
ii. fire bricks (furnace) to form a wide space (shaft) to
accommodate and discharge the heat
Types Characteristic
Magnetite Irons containing 72.4% irons, has magnetic properties and black
in colours.
Carbonate Irons containing less than 30% irons, others are carbon and
phosphorus.
Hematite Irons containing 40% - 65% irons and dark brown reddish in
colours and sometimes added with magnetite sulphade.
Limonite Irons containing 20% - 55% irons and 40% water, yellow
brownish in colours.
Pyrite Irons containing 50% irons and 50% sulphur, gold in colours
and found in crystalline structure.
Taconite Irons containing only 25% to 30% irons, reddish or blackish in
colours.
Sulphate Irons containing 50% sulphur, gold in colours and has few types
such as Phyrito Pyrite, Marcasite and Phynorite
Silicate Irons containing 50% silicon and divided into a few types such
as Kamosite, Stillprunite, Gururite and Minnesotite.
Siderite Irons containing 30% iron, yellow brownish in colours.

2. Part Function
Top The outside wall made by heat-proof material and the inside
wall covered with heat-proof ceramic
Supporting Part hearth – coated with carbon
bosh
stack - coated with aluminium silica
Pipe Channel waste gas pipe - to expel used gases
tuyere - to channeled hot air into the furnace
taphole - to expelled hot melt metal
slag taphole - to expelled slags
 Melting process:
 Raw materials (coke, pellet, sintered ore, iron ore, limestone)
solid raw materials used in this furnace and carried by a skip
car to the top of the furnace
1. tuyere made by brass and cooled with water
2. hot air blast stove used to heat the air up to 1100C
3. the air cooled and the used hot gases will flow repeatedly to the
opposite way from each other through the furnace
4. with the help of hot gases, the bricks lining will become hot and
will expelled heat to reheat the cooled air and it’s called
regeneration
5. the hot metal produced from the furnace every 2 hours
6. clays used to shut the hole will be drilled and after all the works
done, it will be shut back using clay gun
Chemical reaction in iron production from the blast furnace :
Iron ores + cokes + limestones + air slags + gases
3 important chemical processes in the blast furnace :
i. carbon from the coke burning with oxygen in the air blast
ii. oxide reduction to the irons
iii. flushing the gauge and ashes from the iron ores using the
limestone
The disadvantages:
i. high in cost and capital for operation
ii. controlling iron composition are weak
iii. small furnace using coke are uncompetant, huge production
from bigger furnace are no necessity.
The output (products) of the blast furnace :
i. the iron ingots contains 93% of basic irons, 3% - 5% of carbon,
silica, sulphur, phosphorus and manganese.
ii. besides, slags also can be used when separated from melting
irons in the furnace such as road ways and building blocks

3. 2.4 Steel Production
Basic Oxygen Process Furnace (BOP)
 Using pure oxygen.
 Basic oxygen process operation :
1. It can move horizontally and vertically
2. Melting metals and 30% scraps was charging into the furnace
before it changed into vertical position
3. High speed oxygen was blow in directly to the melting metal surface
as shown in figure 3. The oxygen was cooled with water
4. Half of the carbon in the materials changes into oxide in gases form
which then expelled from the furnace through its own channel
5. Other impurities also became oxide and then react with limestones
to form slags
6. The furnace was leaned to horizontal position to discharge melting
steels and then change into inverted position to disposed the slags
as shown in figures 4, 5 and 6
 Basic oxygen process outputs :
1. It can produce high quality steel faster with 80 tones per hour
2. The melting steel usually used to make steel ingots
Electric Arc Furnace
 This furnace has high ability in production and easier to handle.
 Low in oxygen rates made it suitable in producing steel alloy
because the metal did not react with the oxygen in the furnace.
 This furnace used widely and suitable for upgrading the steel,
produces tool steel and high quality alloy steel without using
charging materials.
 It can produce upto 120 tones of steels within 4 hours.
Fig 1 Fig 3Fig 2
Fig 4 Fig 5 Fig 6

4.  Electric Arc Furnace operation
1. Charging
Charge materials which containing steel scraps, iron ores, oxide irons
and limestones were added into the furnace.
Electric current flow to the carbon electrode to supply the electric arc.
2. Melting
The electric arc will melted the oxidize charge materials.
Silicon, manganese and phosphorus will start to oxidize and combined
with limestones to form slags.
Only the carbon electrodes are burning, therefore there is no metal
lost.
3. Slagging
The limestones, fluorspars and oxide irons are added to form slags.
After the reaction, it will form the needed steel compositions.
Sulphur then added to the slags as calcium sulphade.
The reaction are shown as below :
FeS + CaO + C CaS + Fe + CO
4. Finishing or tapping
The steel oxidized by aluminium, ferro-silicon or ferro-manganese to
retracted the steels.
Slags will be plucked or poured start from its surface and then will be
separated or tapped through a hole/ exit channel by leaning the
furnace.
 The advantages of electric arc furnace :
i. blazing process can be controlled and arranged efficiently
ii. no oxidation gases, so can produce high quality steels
iii. the temperature can be control accurately
iv. free from soils and smokes
Fig 24 : Melting process

5. 2.5 Plain Carbon Steel
Plain carbon steel is an iron carbon alloy containing 0.02 to 2%
carbon. All commercial plain carbon steels contains manganese,
sulphur, phosphorus and silicon impurities.
2.5.1 Iron-Carbon Phase Equilibrium Diagram
1. The Iron-Carbon Phase Diagram are a phase diagram that shows
the connection between amount of carbon and the changes of
internal structure by irons and steels while heated until reaching
their melting point.
2. Only ferrous metals could show the changes while it is heated.
3. First stage/ phase called lower critical temperature and the second
stage of changes called upper critical temperature.
4. The levels of lower critical temperature for every eutectoid steels
(0.8% carbon) are the same which it is about 723°C.
5. However, the upper critical temperatures are different depends on
the amount of carbon. The higher the amount (more than 0.8%),
the higher the temperature.
2.5.1.1 Irons, Steels and Cast Irons in the Iron-Carbon Phase
Equilibrium Diagram
1. Between the temperature of 1400C and 1537C, the solid irons
exist in body-centered cubic (BCC) and called as pearlite.
2. The temperature between 910C and 1400C, the crystalline
structures are face-centered cubic (FCC) called austenite.
3. The temperature 910C and below, the iron structures are body–
centered cubic (BCC) called ferrite.
4. At 1125C, cementite dissolvability in austenite irons is limited at
2% carbon only.
5. Cementite solid solutions in austenite called ferrite.
6. Eutectoid composition for ferrite and cementite called pearlite
which containing a lamellar structure consisting of alternate layers
of cementite and ferrite.
7. Ferrite and cementite only transformed from austenite with slow
cooling process. But with fast cooling process, the martensite will
transformed from austenite.
steel cast iron
Fig 1: Iron-Carbon Phase Equilibrium Diagram
liquid
1.0 2.0 3.0 4.0 5.0
700
900
1100
1300
1500
500
 + Fe3C
liquid + 


 + 
 + Fe3C
(pearlite)
liquid + Fe3C

 + 
liquid + 
Ledeburite
o
C
% C0

6. 2.6 Terminologies in Phase Diagram
1. Ferrite /  (alpha-iron)
Ferrite is very soft, ductile and of relatively low strength
2. Austenite /  (gamma iron)
Austenite is also a soft and ductile phase but stronger and less ductile
than ferrite
3. Cementite / Fe3C (iron carbide)
It is combinations of carbon with iron (Fe) to form iron carbide (Fe3C)
Cementite is a hard and brittle compound
4. Pearlite /  + Fe3C
A lamellar structure consisting of alternate layers of ferrite and
cementite
A pearlite has a variable hardness
5. Martensite
The fast cooling of steel from austenite phase results in the formation
of a martensite
Hard and brittle
6. Ledeburite
Consisting of a mixture of two phases, austenite and cementite.
7. Lower Critical Temperature
It is the temperature, during heating, at which pearlite changes to
austenite. This transformation occurs at a fixed temperature of 723C
irrespective of the composition of the alloy
8. Upper Critical Temperature
It is the temperature, during heating, at which last traces of cementite
change into austenite and the alloy becomes completely austenite and
it varies from 723C to 1148C depending upon the carbon content in
the alloy
Fig 2: Microstructure for various phase of steel

7. Ferrite
Austenite
Cementite
Pearlite
Martensite
2.7 Types of Carbon Steels
Types Characteristic
Low carbon steel Contains less than 0.3% carbon (<0.3% C)
Low strength, good machinability, high ductility,
formability and weldability
Applications : bridge structures, buildings, ships, vehicles,
nails, rivets
Good fabrication ductility characteristic and usually used
in annealing and normalizing conditions
Medium carbon steel Contains 0.3 – 0.8% carbon
High strength and ductility after heat treatment, stability,
tough and tensile strength
Applications : railways, wheels, shafts, gears, bolts
It can be quenched to form martensite and bainite if using
media for quenching such as water and brine
High carbon steel Contains more than 0.8% carbon (>0.8% C)
Low in strength, high in hardness and wear resistance
after heat treatment
Applications : moulds, hammers, knives, milling cutters
Also known as tool steel
Tempering process can accelerate martensite formation
and maintain the low strength properties

8. 2.8 Alloy Steels
1. Alloy steel may be defined as carbon steel to which one or more
elements are added to get some beneficial effects.
2. Main purposes :
i. to improve the quality of steels
ii. to improve steel characteristics
iii. to make it suitable for engineering works
iv. to make it easier for heat treatment process
3. The commonly added elements to achieve these properties :
i. increase tensile strength
ii. increase hardness and toughness
iii. higher hardenability
iv. changeability for critical temperature
v. increase wear and abrasive resistance
vi. higher corrosion and oxidation resistance
vii. maintaining higher hardness (red hardness) at temperatures
up to 600C, due to the presence of alloy carbides
viii. higher temperability, and maintain the hardness and strength
at elevated temperatures (creep strength)
2.8.1 Alloying elements and the effects
Nickel increase the strength, hardness and toughness
increase the machineability in finishing process
improves the corrosion resistance of steels
Chromium increase the strength and hardness
machineability
Manganese increase hardness and machineability
act as oxidation agent at higher temperature
high finishability
Silicon deoxidizer, fixing oxidation resistance at high
temperature increase the critical temperature for
heat treatment
Molybdenum easier for hardnessability
increase the tensile strength and creep at higher
temperature
Vanadium deoxidation, promotes the fine grain formation
Cuprum gives resistance to corrosion and act as strengthened
agent
Aluminium deoxidation, promotes the fine grain formation and
formed as nitriding steel
Boron increase the hardenability properties
Plumbum repairing the machineability properties
Bismuth repairing the machineability properties

9. 2.8.2 Main Classes, Element Contents and Alloy Steels
Applications
Stainless steel Contains at least 12% chromium.
Chromium or nickel forms an oxide layer which protects the
underlying steel alloy from corroding.
App:
Tool steel Contains 0.6-1.5% carbon
High hardenability, Wear and corrosion resistance, Cannot
be reshaping, Require high toughness and resistance to
shock.
App:
Structural steel Contents : nickel, manganese, chromium, molybdenum.
High strength ,toughness, resistance to softening at elevated
temperatures, resistance to corrosion, good weldability,
workability , high hardenability.
App:
Magnetic steel Form in 2 methods :
Hard magnet – used to produce permanent magnet
Soft magnet – use to produce impermanent magnet
Heat resistance
steel
Contains chromium, nickel, silicon and manganese, others
are carbon and bismuth (30% carbon, 3.5% bismuth).
High resistance to corrosion and oxidation.
High in hardness and used for high temperature cutting.
2.9 Cast Irons
1. An alloy of iron and carbon containing 2 – 4% carbon.
2. Carbon content form in two ways:
a) cementite (Fe3C)
b) graphite (Fe+C) as free carbon when the cementite is
decomposed
2.9.1 Factors In Carbon Forming
Cooling / Solidifying Process Rate
The cooling rate depends on the thickness and type of die/mould.
1. Slow cooling : caused the carbon separated as graphite,
producing grey cast iron
2. Rapid cooling : prevent the change of graphite and maintain it
hardness and difficult to machined, producing white cast iron
Heat Treatment
1. With long heating process, white cast iron will be forming
graphite structure and are used to produce malleable steel.
High Carbon Contents
1. With high carbon contents, the cast irons will have the
tendency to solidify as grey cast irons.
2. The strength and hardness of irons increased with the
increasing of carbon.
Alloying Elements
Silicon - The higher silicon contents, causing higher resistance and
good magnetic properties
Sulphur - Causing the cast irons to be harden, embrittle and weak
Phosphorus - Increasing strength, hardness and improving the
resistance of corrosion
Manganese - Causing strength, toughness and high wear resistance,
hard to machine because of the hardness

10. 2.9.2 Structures, Properties and the Usages of Cast Irons
Grey cast iron Present in the form of graphite flakes,
and shows a grey surface on the fracture.
Properties : easy to machine, good wear
resistance, high compressive strength
(140 -415 MPa)
Applications : gear boxes, base plates,
bearing brackets
White cast iron Present in the form of cementite, it is
called white cast iron because it shows a
white fractured surface.
Properties : brittle, low in impact
resistance, low in shock resistance
Applications : wearing plates, pump
liners, grinding balls
Malleable cast iron White cast irons heat treated to produce
castings which are bendable or malleable,
increase ductility.
The heat treatment will : increase tensile
strength, improve the ductility, improve
the malleability.
Applications : automobiles (steering
brackets, support brackets, shafts
brackets, camshafts), agricultural
machineries (tractors), machine tools and
electrical industries.
Nodular cast iron Contains large amounts of carbon in the
form of graphite nodules (spheres).
Properties : high strength, high toughness
and ductility, can be welded and
machined.
Applications : automotive parts (piston,
crankshafts, gears), dies (punch dies,
sheet metal dies).
2.10 The Advantages of Cast Irons
1. Widely used in industries as for :
i. cheaper and machineable
ii. low melting point (1140 - 1200oC) compared to steels
iii. liquidity and formability in casting
iv. wear resistance and moistureability