Iron is a chemical element with the
symbol Fe (from Latin: ferrum) and atomic number
26. It is a metal in the first transition series.
Like other group 8 elements, iron
exists in a wide range of oxidation states, −2 to +6,
although +2 and +3 are the most common.
Pure iron is soft (softer than aluminum), but is
unobtainable by smelting. The material is significantly
hardened and strengthened by impurities, such as carbon,
from the smelting process.
Iron metal has been used since ancient times,
though copper alloys, which have lower melting
temperatures, were used first in history. It is Discovered
Carbon Contents In Iron:
. A certain proportion of carbon (between
0.002% and 2.1%) produces steel, which may be up to 1000 times
harder than pure iron.
Crude iron metal is produced in blast furnaces, where ore is reduced
by coke to pig iron, which has high carbon content.
Iron chemical compounds, which include ferrous and ferric
compounds, have many uses. Iron oxide mixed with aluminum
powder can be ignited to create a termite reaction, used in welding
and purifying ores. It forms binary compounds with the halogens and
the chalcogens. Among its organ metallic compounds is ferrocene,
the first sandwich compound discovered
Mechanical properties can
be determined the variety of test,
1. Brinell test,
2. Rockwell test and
3. The Vickers hardness test
The mechanical properties of iron are significantly
affected by the sample's purity,
Name, symbol, Atomic Number
Group, period, block
Standard atomic weight
iron, Fe, 26
8, 4, d
[Ar] 3d6 4s2
2, 8, 14, 2
Density (near r.t.)
Liquid density at m.p.
1811 K2800 °F 1538 °C, ,
5182 °F 2862 °C, 3134 K,
Heat of fusion
Heat of vaporization
Molar heat capacity
Phase diagram and allotropes:
Iron represents an example of allotropy in a metal.
There are at least four allotropic forms of iron, known
as α, γ, δ, and ε.
As molten iron cools it crystallizes at 1538 C into its
δ allotrope, which has a body-centered cubic (bcc)
crystal structure. As it cools further to 1394 C, it
changes to its γ-iron allotrope, a face-centered cubic
(fcc) crystal structure.
At 912 C and below, the crystal structure again
becomes the bcc α-iron allotrope, or ferrite. Finally, at
770 C (the Curie point, Tc) iron becomes magnetic.
Naturally occurring iron consists of four stable
5.845% of 54Fe,
91.754% of 56Fe,
2.119% of 57Fe,
0.282% of 58Fe.
Of these stable isotopes, only 57Fe has a nuclear spin (−1/2).
The nuclide 54Fe is predicted to undergo double beta
is stable with 30 neutrons
is stable with 31 neutrons
is stable with 32 neutrons
According to big bang theory, Iron is
created by extremely large, extremely hot (over 2.5
billion Kelvin) stars through the silicon burning
process. It is the heaviest stable element to be
produced in this manner.
Supernovas also create additional forms of
stable iron via the r-process.
Iron is the sixth most abundant element
in the Universe, and the most common refractory
element. It is formed as the final exothermic stage of
stellar nucleosynthesis, by silicon fusion in massive
It makes up about 5% of the Earth's crust, both the
Earth's inner and outer core are believed to consist
largely of an iron-nickel alloy constituting 35% of the
mass of the Earth as a whole.
Chemistry and Compounds
Iron forms compounds mainly in the +2 and +3 oxidation
states. Traditionally, iron(II) compounds are called
ferrous, and iron(III) compounds ferric.
The most common are iron (II, III)
oxide (Fe3O4), and iron(III) oxide (Fe2O3).
Fe + 2 HX → FeX2 + H2
. The best known sulfide is iron pyrite (FeS2),
also known as fool's gold owing to its golden luster.
Coordination and Organometallic compounds:
Several cyanide complexes are known. The most
famous example is Prussian blue, (Fe4(Fe[CN]6)3).
Potassium ferricyanide and potassium ferrocyanide are
also known; the formation of Prussian blue upon reaction
with iron (II) and iron (III) respectively forms the basis of
a "wet" chemical test.
Ferrocene is an extremely stable complex. The first
sandwich compound, it contains an iron(II) center with
two cyclopentadienyl ligands bonded through all ten
History of Iron
Iron objects of great age are much rarer than
objects made of gold or silver due to the ease of corrosion of
iron. Beads made from meteoric iron in 3500 BC Wrought
iron is an iron alloy with a very low carbon (0.1 to 0.25)
content in contrast to cast iron, and has fibrous inclusions,
known as slag up to 2% by weight.
Cast iron was first produced in China during 5th
century BC, but was hardly in Europe until the medieval
Cast iron was used in ancient China for warfare,
agriculture, and architecture. During the medieval period,
means were found in Europe of producing wrought iron
from cast iron (in this context known as pig iron) using
Steel was first produced in antiquity by using a
bloomer. Blacksmiths in Luristan in western Iran were
making good steel by 1000 BC. Wootz steel by India and
Damascus steel by China were developed around 300 BC
and 500 AD.
The production of iron or steel is a process containing two
main stages. The first stage is to produce pig iron in a blast
furnace. The second is to make wrought iron or steel from pig
iron by a further process.
90 % of all mining of metallic ores is for the
extraction of iron. iron ores hematite (nominally Fe2O3)
2 C + O2 → 2 CO
Fe2O3 + 3 CO → 2 Fe + 3 CO2
2 Fe2O3 + 3 C → 4 Fe + 3 CO2
Small amounts of pure iron can be made
through the purification of crude iron with carbon
monoxide. The intermediate in this process is iron
pentacarbonyl, Fe(CO)5. The carbonyl decomposes on
heating to about 250 C to form pure iron powder.
Fe + CO → Fe(CO)5 (250 C) → Fe + 5CO
2Fe2O3 + 3C → 4Fe + 3CO2
Direct Iron Reduction:
"Direct iron reduction" reduces
iron ore to a powder called "sponge" iron or "direct"
iron that is suitable for steelmaking.
2 CH4 + O2 → 2 CO + 4 H2
Fe2O3 + CO + 2 H2 → 2 Fe + CO2 + 2 H2O
Iron is the most widely used of all the metals,
accounting for 95% of worldwide metal production. Its low
cost and high strength make it indispensable in engineering
applications such as the construction of machinery and
machine tools, automobiles etc .
Pure iron is quite soft, it is most commonly combined with
alloying elements to make steel.
Pig iron is not a saleable product but it can be converted into
steel and wrought iron.
Iron compounds are pervasive in industry as
well being used in many niche uses. Iron catalysts are
traditionally used in the Haber - Bosch process for the
production of ammonia and the Fischer-Tropsch process for
conversion of carbon monoxide to hydrocarbons for fuels and
Powdered iron in an acidic solvent was used in the Bechamp
reduction the reduction of nitrobenzene to aniline.
There are many compounds of Iron that are used in daily life.
Iron is abundant in biology. Iron-proteins
are found in all living organisms, ranging from the
evolutionarily primitive Achaea to humans.
The color of blood is due to the hemoglobin, an ironcontaining protein. As illustrated by hemoglobin, iron is
often bound to cofactors, e.g. in hems.
Iron is a necessary trace element found in nearly all living
organisms. Iron-containing enzymes and proteins.
The most commonly known and
studied "bioinorganic" compounds of iron (i.e., iron
compounds used in biology) are the heme proteins: examples
are hemoglobin, myoglobin, and cytochrome P450.
Health and diet:
Iron is pervasive, but particularly rich sources
of dietary iron include red meat, lentils, beans, poultry, fish,
leaf vegetables, watercress, tofu, chickpeas, black-eyed peas,
blackstrap molasses, fortified bread, and fortified breakfast
It is occurs when there is free radical of ferrous
iron atom. It is very toxic and could damage DNA,
proteins, lipids, and other cellular components.
Thus, iron toxicity occurs when there is free iron
in the cell, which generally occurs when iron levels
exceed the capacity of transferring to bind the iron.
Steel is an alloy of iron and a small amount
of carbon. Carbon is the primary alloying element, and its
content in the steel is between 0.002% and 2.1% by
Additional elements may be present in steel:
manganese, phosphorus, sulfur, silicon, and traces of
oxygen, nitrogen and aluminium.
Iron is found on Earth in the form of Magnetite and Hematite
and then we pure by removing the Oxygen from them.
Small quantities of iron were smelted in ancient times, in the
solid state, by heating the ore buried in a charcoal fire and
welding the metal together with a hammer, squeezing out the
Smelting results in an alloy (pig iron) that contains too much
carbon to be called steel.
To inhibit corrosion, at least 11% chromium is added to steel so
that a hard oxide forms on the metal surface
Sulfur, nitrogen, and phosphorus make steel more
The density of steel varies based on the alloying
constituents but usually ranges between
7,750 and 8,050 kg/m3
7.75 and 8.05 g/cm3
At room temperature, the most stable form of iron is
the body-centered cubic (BCC) structure called ferrite
The most common are annealing and quenching and
Types of Steel
Steel is basically an alloy of iron and carbon with a
small percentage of other metals such as nickel,
chromium, aluminum, cobalt, molybdenum, tungsten etc.
Steel is considered to be carbon steel when
no minimum content is specified or required for
chromium, cobalt, columbium [niobium], molybdenum,
nickel, titanium, tungsten, vanadium or zirconium.
Steels contain up to 0.30% C.
Steels are similar to low-carbon steels except that
the carbon ranges from 0.30 to 0.60% and the manganese from 0.60
Steels are experimental alloys containing 1.25 to
High-Strength Low-Alloy Steels:
The HSLA steels have low carbon
contents (0.05-0.25% C) in order to produce adequate formability
and weld ability, and they have manganese contents up to 2.0%.
Low-alloy steels constitute a category of ferrous materials that
exhibit mechanical properties superior to plain carbon steels as
the result of additions of alloying elements such as nickel,
chromium, and molybdenum. Total alloy content can range
from 2.07% up to levels just below that of stainless steels,
which contain a minimum of 10% Cr.
As with steels in general, low-alloy steels can be classified
Chemical composition, such as nickel steels, nickel-chromium
steels, molybdenum steels, chromium-molybdenum steels
Heat treatment, such as quenched and tempered, normalized
and tempered, annealed.
Low-carbon quenched and tempered steels:
Combine high yield strength (from 350 to 1035 MPa) and
high tensile strength with good notch toughness, ductility,
corrosion resistance, or weld ability.
Medium-carbon ultrahigh-strength steels:
They are structural steels with yield strengths that can
exceed 1380 MPa.
It used for ball and roller bearing applications are
comprised of low carbon (0.10 to 0.20% C) case-hardened
steels and high carbon (-1.0% C) through-hardened steels.
Chromium-molybdenum heat-resistant steels:
It contain 0.5 to 9% Cr and 0.5 to 1.0% Mo. The carbon content
is usually below 0.2%.
History Of Steel Making
Steel was known in antiquity, and may have been
produced by managing bloomeries, or iron-smelting facilities, in
which the bloom contained carbon.
Steel was produced in large quantities in Sparta around 650BC.
Wootz steel and Damascus steel:
Wootz steel was produced in India
by about 300 BC However; the steel was an old technology in India
when King Porus presented a Steel sword to the Emperor Alexander
in 326 BC
Modern Steel Making
Originally using charcoal, modern methods use coke, which
has proven more economical.
Processes Starts from Bar Iron:
In these processes pig iron was "fined" in a finery forge to
produce bar iron (wrought iron), which was then used in steelmaking.
The production of steel by the cementation process was
described in a treatise published in Prague in 1574 and was in
use in Nuremberg from 1601.
Process Starts from Pig Iron:
The modern era in steelmaking began with the introduction
of Henry Bessemer's Bessemer process in 1855, the raw
material for which was pig iron.
The steel industry is often considered an indicator of economic
In 1980, there were more than 500,000 U.S. steelworkers. By
2000, the number of steelworkers fell to 224,000.
Between 2000 and 2005, world steel demand increased by 6%.
Shanghai Baosteel Group Corporation and Shagang Group.
ArcelorMittal is however the world's largest steel producer.
2008, the steel industry faced a sharp downturn that led to
ThyssenKrupp offered the plants for sale at under $4 billion.
High strength low alloy steel has small additions (usually
< 2% by weight) of other elements, typically 1.5%
manganese, to provide additional strength for a modest
Low alloy steel is alloyed with other elements, usually
molybdenum, manganese, chromium, or nickel, in
amounts of up to 10% by weight to improve the harden
ability of thick sections.
Stainless steels contain a minimum of 11% chromium,
often combined with nickel, to resist corrosion.
Iron and steel are used widely in the construction of roads, railways, other
infrastructure, appliances, and buildings.
Most Large Structure buildings contain the skeleton of steel, such as
stadiums and skyscrapers, bridges, and airports, are supported by a steel
construction, aerospace, white goods (e.g. washing machines), heavy
equipment such as bulldozers, office furniture, steel wool, tools,
and armour in the form of personal vests or vehicle armour (better known
as rolled homogeneous armour in this role).
So Iron and Steel have many application