

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