Material Sciences

1. CHAPTER 2
FERROUS MATERIAL

2. IRON
• Production of iron : Blast furnace
• Production of steel :
a)Basic Oxygen Furnace
b) Electric Arc Furnace

3.  Chemical symbol: Fe
 Iron melts at 1353C and boils at 2700 C
 The purest iron comes from the sky in the form of
meteors.
 Pure iron does not rust in water; iron rust because it
contains impurities.
 Pure iron is seldom used in industry because it is too
soft (can be scratch with the fingernail).
IRON

4.  Cast iron
 Wrought iron
 Steel
Iron is used in 3 forms:

5. • Iron ore is not pure as it comes from iron mines.
• Types of iron ore:
• a) Hematite (Fe2O3)
• b) Magnetite (Fe3O4)
• c) Pirite
• d) Limonite
• e) Taconite
Iron Ore

6. 1. Magnetite (Fe3O4)
 Containing of 72.4% ferum.
 Black, grey blackist in colour.
 Magnetic minerals.
 In rock or sediment rock.
Iron Ores

7. 2. Hematite (Fe2O3)
 Containing of 40-65% ferum.
 Grey blackist or red chocolate in colour.
 Common ore for iron.
 In rock.
Iron Ores

8. 3. Limonite (Fe2O3.3H2O)
 Containing of 20-55% ferum with 40% water.
 Yellow, orange, red chocolate, chocolate black.
 Found in loose and sedimentary soil.
 Known as dehydration hematite.
Iron Ores

9. 4. Iron Carbonate
 Containing ≤30% ferum.
 Example: siderite
 Color ranges from yellow to dark brown or black.
 Found in sedimentary rock.
Iron Ores

10.  1) Grade : composition of iron ore
 2) Compactness : moderate
 3) Purity : low impurity
 4) Uniformity (in composition )
Characteristics of Iron Ore

11.  Making pig iron is the first step in the purifying of iron
and the making of steel.
 Pig iron is produced when the impurities are burned
out of iron ore in a blast furnace.
Pig Iron

12. Blast Furnace
It is called a blast furnace because a blast of hot air is forced
into it near the bottom.
A blast furnace looks like a tall chimney on the outside:
*15m – 30m high
*6m – 9m in diameter
*covered on the inside with special
bricks or clay that can withstand
great heat.

13. BLAST FURNACE PROCESS
Iron ore (2 tons) + Coke{purified form of coal} (1 ton) +
limestone (0.5 ton) + hot air (4 tons)  pig iron (1 ton) + slag +
gas
Iron ore – comes from iron mines
Coke – The coke is added to provide the main chemical reagents
(carbon and carbon monoxide) for the iron ore reduction
Flux – The flux, limestone and/or dolomite, is added to combine
with ash in the coke and gangue in the ores, to produce a slag
that rises to the top of the pool of molten pig iron that collects
in the crucible.

14. BLAST FURNACE

15. Blast Furnace:Equipmenta) Skip car (conveyors) – are used to deliver the blast
furnace charge to the top of the furnace
b) Bosh – is an inverted conical section in which the
melting starts.
c) Receiving hopper – the blast furnace charge is loaded
into the receiving hopper
d) Hearth – is an intricately constructed crucible-like
vessel upon which the vertical shaft portion of the
furnace sits. All the molten metal and slag collect in
the hearth before being drained.
e) Bells (large and small) – prevents gas from escaping
from the furnace while it is being charged.

16.  f) Bustle pipe – encircles the blast furnace and delivers the hot
blast air from the hot-blast line to the furnace
 g) Stack – is the upper portion of the furnace where the burden
is pre-heated
 h) Injection lance – is inserted into the blowpipe that leads up to
the tuyeres
 i) Iron and slag notches – the molten iron is removed from the
hearth through the iron notches. The metal is placed into
transfer ladles, while the slag may be transferred to slag pots
 j) Tuyeres – the hot blast air is delivered to the furnace through
water-cooled openings called tuyeres. The tuyeres are located at
the top of the hearth
Blast Furnace Equipment

17.  1) The iron ore, coke and limestone are dumped into the top of
the blast furnace, which holds about 1000 tons.
 2) The burning coke and the blast of very hot air melt the iron
ore.
 3) The limestone mixes with the ashes of the burnt coke and
with the rock and earth of the iron ore. The mixture forms a
waste that is called slag.
 4) Because the molten iron is heavier than the slag, it drips to
the bottom of the furnace.
 5) The furnace is emptied (called tapping) through a tap hole at
the bottom. The melted iron flows out into a ladle for transfer to
a steel furnace or into a trough and then into iron pig molds.
Blast Furnace: Process
Description

18.  The oxygen in the iron oxides is removed by a series of chemical
reactions:
1) 3Fe2O3 + CO = CO2 + 2 Fe3O4 Begins at 450 C
2) Fe3O4 + CO = CO2 + 3 FeO Begins at 600  C
3) FeO + CO = CO2 + Fe Begins at 700  C
or
FeO + C = CO + Fe
 The coke is ignited by this hot blast and reacts to generate heat:
C + O2 = CO2 + Heat
Since the reaction takes place in the presence of excess carbon at a
high temperature, the CO2 is reduced to carbon monoxide:
CO2 + C = 2CO
* The product of this reaction, carbon monoxide is necessary to reduce the
iron ore.
Blast Furnace: Chemical Reaction

19.  The limestone descends in the blast furnace and remains a solid
while going through its first reaction as follows:
CaCO3 = CaO + CO2
This reaction requires energy and starts at about 875C.
The CaO formed from this reaction is used to remove sulphur
from the iron which is necessary before the hot metal becomes
steel. This sulphur removing reaction is:
FeS + CaO + C = CaS + FeO + CO
* The CaS becomes part of the slag.
Blast Furnace: Chemical Reaction

20. BASIC OXYGEN FURNACE
•To make steel from pig iron, it is necessary to
remove carbon and other impurities.
•In the BOP, pure oxygen is blown into the
molten iron through a water-cooled lance that
enters through the top of the furnace.

21.  The use of pure oxygen enables the chemical
composition of the steel to be controlled very
accurately. Thus, BOP steel is of very high
quality.
 The use of pure oxygen results in higher
furnace temperatures, thereby shortening the
time required to convert the pig iron to steel.
 (a BOP furnace can produce about 300 tons of
Advantages of using pure oxygen

22. Basic Oxygen Furnace (BOP)

23. BOP: Process Description

24. Basic Oxygen Furnace
(Relau Asas Oksigen)

25. The BOP furnace is tilted on its side for charging. Molten iron
and scrap are charged into its mouth.

26. It is then tilted to an upright position, and pure oxygen is
blown into the furnace under high pressure, thus burning out
the impurities

27.  Burned lime, converted from limestone, is also
added to the furnace with the oxygen to increase
the removal of impurities.
 When the impurities have been burned out of the
molten iron, the necessary elements (such as
carbon, nickel, chromium and others) are added to
meet the specifications for the steel required.
Cont.

28. The furnace is then emptied by tilting it on its side and pouring
the molten steel into a large ladle

29. ELECTRIC ARC FURNACE

30. ELECTRIC ARC FURNACE

31. Electric Arc Furnace

32. The Electric Arc Furnace Process

33. Advantages of Electric Arc Furnace
•The electric arc process is used when close control of
temperature and exact amounts of alloying elements are
important.
•Higher temperatures can be reached than with other
steel-making furnaces.
•Electric arc furnaces are good for making high-carbon
steel, steels alloyed with metals that have high melting
points, and stainless steels.

34.  Powerful electric arcs bridge the air gap between large
carbon electrodes and the metal to be melted.( The metal
serves as the other electrodes)
 The arcs produce the heat required to melt the metal.
 100% iron and steel scrap can be used.
 Temperature control is very good. This makes possible very
close control of the grain structure of the steel.
Cont.

35.  Furnace charging
 Melting
 Refining
 De-slagging
 Tapping
Furnace Operations

36.  The roof and electrodes are raised and are
swung to the side of the furnace to allow the
scrap charging crane to move a full bucket of
scrap into place over the furnace.
 The scrap falls into the furnace and the scrap
crane removes the scrap bucket.
 The roof and electrodes swing back into place
over the furnace. The roof is lowered and
then the electrodes are lowered to strike an
Furnace Charging

37.  The roof of an arc furnace removed, showing the three
electrodes
Furnace Charging

38.  Melting is accomplished by supplying energy to the
furnace interior. This energy can be electrical or
chemical. Electrical energy is supplied via the graphite
electrodes and is usually the largest contributor in
melting operations.
 Once the final scrap charge is fully melted, flat bath
conditions are reached. At this point, a bath
temperature and sample will be taken. The analysis of
the bath chemistry will allow the melter to determine
the amount of oxygen to be blown during refining.
Melting

39.  Refining operations in the electric arc furnace have traditionally
involved the removal of phosphorus, sulfur, aluminum, silicon,
manganese and carbon from the steel.
 These refining reactions are all dependent on the availability of
oxygen. Oxygen was lanced at the end of meltdown to lower the
bath carbon content to the desired level for tapping. Most of the
compounds which are to be removed during refining have a
higher affinity for oxygen that the carbon. Thus the oxygen will
preferentially react with these elements to form oxides which
float out of the steel and into the slag.
Refining

40.  De-slagging operations are carried out to remove
impurities from the furnace. During melting and
refining operations, some of the undesirable
materials within the bath are oxidized and enter the
slag phase.
 The furnace is tilted backwards and slag is poured out
of the furnace through the slag door.
De-slagging

41.  Once the desired steel composition and
temperature are achieved in the furnace, the
tap-hole is opened, the furnace is tilted, and
the steel pours into a ladle for transfer to the
next batch operation (usually a ladle furnace
or ladle station).
 During the tapping process bulk alloy
additions are made based on the bath analysis
and the desired steel grade.
Tapping

42.  An electric arc furnace (the large cylinder) being tapped
Tapping

43. KINDS OF STEEL

45. There are two main kinds of steels:
a) plain carbon steels
b) alloy steels
Plain carbon steels are divided into three main
groups:
1) Low-carbon steel (mild steel)
2) Medium-carbon steel
3) High-carbon steel

46. Plain carbon steel
Fe-C Phase Diagram

47.  Ferrite : is an interstitial solid solution of carbon in
alpha iron. Ferrite dissolves considerably less
carbon than austenite, with maximum amount
being 0.025%C at 723ºC. Ferrite is nearly pure iron.
 Cementite: Fe3C is a compound of iron and carbon
referred to as iron carbide. Cementite contains
6.67% C and 93.3% Fe. Cementite is so hard it can be
machined only by grinding.
definition:

48.  Pearlite : is a lamellar aggregate of ferrite and
cementite formed from the eutectoid
decomposition of austenite during slow cooling.
Pearlite has the microstructural appearance of
fingerprints.
 Austenite : (γ-Fe) is an interstitial solid solution of
carbon in gamma iron. The solid solubility of
carbon in austenite is a maximum of 2.08% at 1148ºC
and decreases to 0.8% at 723ºC.
definition:

49.  Upper critical temperature (point) A3 is
the temperature, below which ferrite starts to form as a
result of ejection from austenite in the hypoeutectoid
alloys.
 Upper critical temperature (point) ACM is
the temperature, below which cementite starts to form
as a result of ejection from austenite in the
hypereutectoid alloys.
 Lower critical temperature (point) A1 is
the temperature of the austenite-to-pearlite eutectoid
transformation. Below this temperature austenite does
not exist.
definition:

50. Plain Carbon Steels

51.  Contains between 0.05% to 0.30% carbon
 Good weldability and machinability.
 Low tensile strength, very ductile and soft.
 Application : body for washing machine, wire, steel
pipe, screw and nuts.
 Low carbon steel is also used for forge work, rivets,
chains and machine parts that do not need great
strength
Low-Carbon Steel

52.  Contains 0.3% to 0.6% carbon.
 Medium carbon steel is stronger than low carbon
steel. It is also more difficult to bend, weld and cut
than low carbon steel.
 Balances ductility and strength and has good wear
resistance
 Medium carbon steel is used for bolts, shafts, car
axles, rails and other parts or tools that require strong
metal.
Medium-Carbon Steel

53.  Also known as carbon tool steel
 Contains between 0.6% to 1.5% carbon
 The best grades of this steel are made in electric
furnaces
 It is used to make such tools as drills,
taps,dies,reamers,files,cold chisels,crowbars and
hammers.
 It is hard to bend, weld and cut
High-Carbon Steel

54.  1) Silicon
 - a chemical element found in rocks. It gives hardness
to iron.
 2) Sulfur
 - a yellow, flammable nonmetal. Too much sulfur
makes these metals weak and brittle, causing cracks.
A little sulfur is added to some steels for better
machinability.
Other Elements in Steel

55.  3)Phosphorus
 - a poisonous, active nonmetal. It causes brittleness and
coarse grain in iron and steel.
 4) Manganese
 - a grayish white metal, hard and brittle. It resembles iron
but is not magnetic. It is used in making steel.
Cont

56. Alloy Steels

57. cont
•Alloys steels are made by combining steels with
one or more other elements.
•These elements are usually metals.
•They are intentionally added to obtain properties
that are not found in plain carbon steels.

58. The main purpose is to improve its mechanical
properties such as:
 Improve tensile strength
 Improve toughness
 Wear resistance
 Corrosion resistance
 Resistance to heat
 Improve properties by heat treating
The purpose for alloying the steel

59.  1) Chromium (chrome)
 - gives hardness to steel, and toughens it. It also
makes the steel’s grain finer and causes the steel to
resist rust, stains, shocks, and scratches.
 - chromium is the basis for stainless steel (contains 11%
to 26%)
 It has a lasting, bright, silvery gloss.
Effects of Alloying Element

60.  Some important uses for stainless steel:
-sinks
-tableware
-pots and pans
-cutting tools
-dental tools
-automobile parts
-fine measuring tools and instruments
cont

61.  2) Cobalt
- an important metal used in making cutting tool alloys (these
alloys include high-speed steels, cast alloys and cemented
carbides)
-its ability to improve the hardness of cutting tools when they
are hot or even red-hot.
cont

62.  3) Manganese
- a hard, brittle, grayish-white metal.
- It purifies and adds strength and toughness to steel.
- Manganese steel remains hard even when cooled slowly.
- It is so very hard that it is difficult to cut, so it is usually cast
into shape.
Cont.

63.  4) Molybdenum
-a silvery white metal, it adds strength and hardness to steel
and allows it to stand heat and shocks.
-molybdenum steel is used for automobile parts, high grade
machinery, wire as fine as 0.01 mm in diameter, ball bearings
and roller bearings.
Cont.

64.  5) Nickel
- Adds strength and toughness to steel.
- Nickel steel does not rust easily and is very strong and hard.
- It is used for wire cables, shafts, steel rails, automobile and
railroad car axles and armor plate.
Cont.

65.  6) Tungsten
-a rare, heavy, white metal that has a higher melting point
than any other metal.
-tungsten adds hardness to steel.
-it gives steel a fine grain and allows steel to withstand heat.
- Tungsten steel is used extensively for making cutting tools.
These tools need no special hardening treatment and will
withstand high temperatures.
Cont.

66.  7) Vanadium
- a pale, silver-gray metal. It is brittle and resists corrosion.
- Vanadium steel can withstand great shocks.
- It is used for springs, automobile axles and gears and other
parts that vibrate when in use.
- Vehicles used in heavy construction commonly used
vanadium steel.
Cont.

67.  8) Chromium-vanadium steel
- is hard and has great tensile strength.
- It can be bent double while cold and is easy to cut.
- is used for automobile parts such as springs, gears,
connecting rods and other parts which must be strong and
tough but not brittle.
Cont.

68. Types of alloy
steel
Magnetic steel
Tool and
mould steel
Structure steel
Corrosion
resistance steel
Heat resistance
steel
Alloy steel

69.  Alloy elements: Cr, Ni, P, Si, Mn, Mo, Cu is added to
increase strength solid solubility hardening.
 Increase ability to metal forming and weldable.
 High strength, high toughness and resistance to stress.
 Application : beams, shaft
Structure Steel

70.  Alloy elements : Al, Si, Cr
 High Cr ~12% Cr resistance to high temperature
corrosion
 Cr reacts with oxygen to form chromium oxide
and prevent the steel from corrode.
 Application : gas turbine, engine casing and
aircraft frame, cutlery.
Corrosion Resistance Steel

72.  Forming of carbide and nitride.
 Carbide : V, W, Cr forms highly hardness carbide
such as Fe4W2C – hardness and strength
increase.
 High Speed Steel (HSS)- contains14-22%W, 4%Cr
and 1%V forms hard carbide heat resistance.
 Nitrida : Ti and Al forms Ni2Ti, NiAl, Ni3Ti –
improves ductility and toughness.
 Maraging steel – rocket and high speed air
craft.
Heat Resistance Steel

73.  High hardness and wear resistance.
 Use for cutting, shaping or forming such as rolling,
drawing.
 Have high carbon contents 0.6-1.3%.
 Contain elements such as Cr, Co, Mn, Mo, Ni, Si, W, and
V to form various alloy carbides and help increase the
hardness, wear resistance and elevated-temperature
softening resistance.
Tool Steel

74.  Contain Cr and Ni as the principal alloying elements.
 Have low-to-medium carbon content and a total alloy
content of 1.5-5%.
 It is special tool steel which is to be heat treated.
Mould Steel

76.  Ferromagnetic metals in room temperature are Fe, Co and Ni.
 Tough and durable, inexpensive to produce, maintains strong
magnetism when miniaturized and can produce a stable
magnetic force in spite of temperature changes or vibration.
 Magnetic steel is used to form magnet induction
 Mashima & Alnico
Magnetic Steel

77. CAST IRONS

78. Cast iron is pig iron that has been remelted and
poured into a mold.
Iron cools in the shape of a useful machine
part or article.
An object made this way is called a casting.

79. Basic elements in cast iron
 Iron
 Carbon : 2.8 to 3.6%
 Silicon :1.0 to 3.0%
 Manganese : 0.4 to 1.0%
 Magnesium : 0.03 to 0.05%
 Phosphorus : 0.05 to 1.0%
 Sulfur : 0.1 to 0.35%
Cast Iron

80. Properties of cast iron:
1. Tensile strength moderate180-350MPa
2. High compression strength.
3. Immersion capacity good.
4. High wear resistance
5. Good machinability
6. Low impact resistance and ductility
Cast Iron

82. 1. Cooling rate:
High - stable cementite
- white cast iron
- hard and brittle
Low - cementite forms to ferrite and graphite
- gray cast iron
- ductile
2. Carbon content– increase of carbon lower the melting
temperature and more graphite are formed→ gray cast
iron
Cast Iron Properties Effects

83. 3. Cross-section Size
Wide - low solidify rate
- graphite
- gray cast iron
Small - vs wide cross-section
4. Content of other elements:
silicon - high liquidity → graphite → gray cast iron
sulfur - cementite stable, forms MnS → white cast iron
Manganese – combine with sulfur to form MnS
Fosforus - liquid steel→ graphite → gray cast iron
Cast Iron Properties Effects

84.  A) Gray Cast Iron
 B) White Cast Iron
 C) Malleable Iron
 D) Ductile Cast Iron
Kinds of Cast Iron

85. Types of cast
iron
Nodular cast iron
White malleable
Cast iron
Gray cast iron
White cast iron
Black malleable
cast iron

86.  Most carbon is in a free state.
 It is scattered in the form of graphite flakes
throughout the crystalline grain structure of the
metal.
 This arrangement of carbon makes the cast iron
brittle. Thus, it fractures easily from sharp blows.
 It has a gray crystalline color where fractured.
Gray Cast Iron (1.7%C to 4.5%C)

87. Microstructure of Gray Cast Iron

88.  It is so named because of a white, crystalline color at
the fracture when broken.
 White cast iron is made by rapid cooling the molten
pig iron.
 Most of the carbon in white cast iron is in chemically
combined state.
 It forms a hard substance called cementite,Fe3C.
White Cast iron (2%C to 3.5%C)

89.  White cast iron is so hard that it cannot be machined except
by grinding.
 Its direct use is limited to castings requiring the surfaces to
withstand abrasion and wear.
 The major use of white cast iron,however, is making
malleable cast iron.
Cont.

90. Microstructure of White Cast Iron

91.  Malleable iron is cast iron that has been made soft, tough,
strong and malleable.
 When white cast iron is heated at a high temperature for
100-120 hours, it is converted to malleable iron.
 This heat treatment process, called malleableizing, takes
place in heat treatment furnace.
Malleable Cast Iron (2%C to 2.6%C)

92.  Metal is malleable, it can be hammered into
different shape without cracking.
 Heat treatment changes the arrangement of the
carbon from its combine state as cementite to free
carbon.
 At the prolonged high temperature, the free carbon
comes together to form clusters or globule.
 The surrounding iron then becomes soft and
machinable.
 They are used for making tough castings for
automobiles, tractors and many kinds of machinery
parts.
cont

93. Microstructure of White Malleable Cast Iron

94. Microstructure of Black Malleable Cast Iron

95.  Also known as nodular iron or spheroidal graphite
iron.
 The carbon is in the free state.
 It is in small, rounded lumps carbon clusters called
nodules.
 The iron surrounding the tiny balls of graphite is so
tough and machinable.
Ductile Cast Iron

96.  Ductile cast iron is produced very much like gray cast iron.
 Magnesium alloys and certain other elements are added to a
ladle of gray iron before it is poured into molds to make
castings.
 These additives and proper heat treatment cause the
carbon in the molten iron to form balls or nodules as it cools
and becomes solid.
Cont.

97.  Ductile cast iron has properties similar to malleable iron.
 It is tough, machinable, and possesses many of the
characteristics of steel.
 It is used for making tough castings for automobiles, farm
machinery and many other kinds of machinery.
Cont.

98. Microstructure of Ductile Cast Iron