Introduction
Properties
Occurrence
Uses
Metallurgy
Introduction
Properties
Occurrence
Uses
Metallurgy
Introduction
Iron or ferrum (latin word)
Elemental symbol: Fe
Atomic number: 26
Elemental group: Transition element
Metallic iron was known and used for
ornamental purposes and weapons in
prehistoric ages. The earliest specimen
still extant, a group of oxidized iron beads
found in Egypt, dates from about 4000 BC.
The archaeological term Iron Age properly
applies to the period when iron was used
extensively for utilitarian purposes, as in
tools, as well as for ornamentation.
Physical Properties
Iron is soft, malleable, and ductile.
Iron is easily magnetized at ordinary
temperatures; it is difficult to magnetize
when heated, and at about 790° C (about
1450° F) the magnetic property disappears.
Pure iron melts at about 1535° C (about
2795° F), boils at 2750° C (4982° F), and
has a specific gravity of 7.86.
The atomic weight of iron is 55.847.
Chemical Properties
It
combines
with
the
halogens
(fluorine, chlorine, bromine, iodine,
and astatine), sulfur, phosphorus,
carbon, and silicon.
It displaces hydrogen from most dilute
acids.
It
burns
in
oxygen
to
form
ferrosoferric oxide, Fe
3
O
4
(magnetite).
Chemical Properties
When exposed to moist air, iron becomes
corroded, forming a reddish-brown, flaky,
hydrated ferric oxide commonly known as
rust.
When iron is dipped into concentrated nitric
acid, it forms a layer of oxide that renders it
passive—that
is,
it
does
not
react
chemically with acids or other substances.
The protective oxide layer is easily broken
through by striking or jarring the metal,
which
then
becomes
active
again.
Occurrence
Metallic iron occurs in the free state in only a
few localities, notably western Greenland. It is
found in meteorites, usually alloyed with
nickel.
In chemical compounds the metal is widely
distributed and ranks fourth in abundance
among all the elements in the earth's crust;
next to aluminum it is the most abundant of
all metals.
Occurrence
The principal ore of iron is hematite, which
is mined in the United States in
Minnesota, Michigan, and Wisconsin.
Other important ores are goethite,
magnetite, siderite, and limonite (bog
iron).
Occurrence
Pyrite, FeS, the sulfide ore of iron, is not
processed as an iron ore because it is
too difficult to remove the sulfur.
Small amounts of iron occur in
combination in natural waters, in plants,
and as a constituent of blood.
Uses of Iron
Iron is used in processed forms, such as
wrought iron, cast iron, and steel.
Commercially pure iron is used for the
production of galvanized sheet metal and of
electromagnets.
Iron compounds are employed for medicinal
purposes in the treatment of anemia.
Iron
is
also
used
in
tonics.
Uses of Iron
The most important ferrous compound is
ferrous sulfate (FeSO
4
), called green vitriol
or copperas. It usually occurs as pale-green
crystals containing seven molecules of
water of hydration. It is obtained in large
quantities as a by-product in pickling iron
and is used as a mordant in dyeing, as a
tonic medicine, and in the manufacture of
ink
and
pigments.
Uses of Iron
Ferric oxide or hematite, an amorphous red
powder, is obtained by treating ferric salts with
a base or by oxidizing pyrite. It is used both as
a pigment, known as either iron red or Venetian
red; as a polishing abrasive, known as rouge;
and as the magnetizable medium on magnetic
tapes and disks.
Ferric chloride, obtained as dark-green, lustrous
crystals by heating iron in chlorine, is used in
medicine as an alcoholic solution called
tincture
of
iron.
Uses of Iron
Ferric ferrocyanide (Fe
4
[Fe(CN)
6
]
3
), a dark-
blue, amorphous solid formed by the
reaction of potassium ferrocyanide with a
ferric salt, is called Prussian blue. It is used
as a pigment in paint and in laundry bluing
to correct the yellowish tint left by the
ferrous salts in water.
Potassium ferricyanide (K
3
Fe(CN)
6
), called
red prussiate of potash, is obtained from
ferrous ferricyanide (Fe
3
[Fe(CN)
6
]
2
; also
called Turnbull's blue), and is used in
processing blueprint paper.
Metallurgy of Iron
Reduction of iron oxide in the Blast furnace.
Materials:
• Concentrated iron ore
• Coke
• Blast of hot air
• Flux
Reactions taking place in the Blast
furnace
•
Combustion of Coke
C
(s)
+ O
2(g)
CO
2(g)
+ heat
CO
2(g)
+ C
(s)
2CO
(g)
•
Reduction of Fe
2
O
3
2Fe
2
O
3(s)
+ 3C
(s)
4Fe
(l)
+ 3CO
2(g)
Fe
2
O
3(s)
+ 3CO
(g)
4Fe
(l)
+ 3CO
2(g)
Reactions taking place in the Blast
furnace
•
Calcination
CaCO
3(s)
+ heat CaO
(s)
+ CO
2(g)
•
Slag formation
CaO
(s)
+ SiO
2(s)
CaSiO
3(l)
(slag)
CaO
(s)
+ Al
2
O
3(s)
Ca(AlO
2
)
2(l)
1.
A blast furnace forces
in extremely hot air
through a mixture of ore,
coke, and limestone,
called the charge.
Iron Blast furnace
2. Carts called skips dump the
charge into the top of the furnace,
where it filters down through bell-
shaped containers called hoppers
.
Iron Blast furnace
3.
Once in the furnace, the
charge is subjected to air blasts
that may be as hot as 870° C
(1600° F).
4.
The waste metal, called slag,
floats on top of the molten pig iron.
Both of these substances are
drained, or tapped, periodically for
further processing.
Products of the Blast furnace
Pig iron - 93-95% Fe, 3-5% C, 1%
Si, 0.1- 0.3% P, <1% S
Waste gases – CO
2
and CO
Slag – CaSiO
3
and Ca(AlO
2
)
2
Principal products of Iron
Cast iron
Wrought iron
Steel
CAST IRON
•
This is pig iron melted with scrap
Iron. It is the least pure of all forms
of iron containing 93% Fe & 5% C.
WROUGHT IRON
•
The purest form of iron produced
when impurities are removed. It
contains 0.5% impurities.
STEEL
•
A form of iron which usually contains
0.1 to 2% carbon.
STEEL
Carbon
steels
Carbon
content
Uses
Low carbon
steel
< 0.3%
Rivets,
wires, nails
Medium
carbon steel
0.3% to
0.8%
Railroad
rails, axles
High carbon
steel
0.8% to 2%
Tools,
springs, files
Steel Making
•
Bessemer Process
•
Open-Hearth Method
•
Basic Oxygen Process