Iron is a silvery-white or grayish metal that is ductile, malleable, and one of three naturally magnetic elements. It has a high tensile strength and melting point of 1,538°C. The mechanical properties of iron and its alloys can be evaluated using hardness tests like the Brinell test, Rockwell test, and Vickers hardness test which measure the material's resistance to plastic deformation. Chemically, iron is very reactive and readily combines with oxygen to form rust, as well as reacting with hot water, steam, acids, and many other elements.

1. GENERAL PROPERTIES OF IRON
Physical
Mechanical
Chemical

2. ____Iron____

3. ____Physical
Properties____
• Iron is a silvery-white or grayish metal. It is ductile and malleable.
Ductile means capable of being drawn into thin wires. Malleable
means capable of being hammered into thin sheets. It is one of only
three naturally occurring magnetic elements. The other two
are nickel and cobalt
• Iron has a very high tensile strength. Tensile means it can be
stretched without breaking. Iron is also very workable. Workability is
the ability to bend, roll, hammer, cut, shape, form, and otherwise
work with a metal to get it into a desired shape or thickness.
• The melting point of pure iron is 1,538°C (2,800°F) and its boiling
point is about 2,862°C (5,182°F). Its density is 7.874 grams per
cubic centimeter. The melting point, boiling point, and other physical
properties of steel alloys may be quite different from those of pure
iron.

4. ____Mechanical
Properties____
The mechanical properties of iron and its alloys can be evaluated
using a variety of tests, including the Brinell test, Rockwell
test and the Vickers hardness test.
The Brinell scale characterizes the indentation hardness of
materials through the scale of penetration of an indenter, loaded
on a material test-piece. It is one of several definitions of
hardness in materials science.
It was the first widely used and standardized hardness test
in engineering and metallurgy.

5. ____Brinell Test____
The typical test uses a 10 millimeters
(0.39 in) diameter steel ball as an
indenter with a 3,000 kgf (29 kN;
6,600 lbf) force. For softer materials, a
smaller force is used; for harder
materials, a tungsten carbide ball is
substituted for the steel ball. The
indentation is measured and hardness
calculated as:
where:
P = applied force (kgf)
D = diameter of indenter (mm)
d = diameter of indentation (mm)

6. ____Rockwell test_____
The Rockwell scale is
a hardness scale based on
the indentation hardness of a
material. Indentation hardness tests
are used to determine
the hardness of a material to
deformation. The examined
material is indented until an
impression is formed.
When testing metals, indentation
hardness correlates linearly
with tensile strength.

7. ____Vickers Hardness
Test____
The Vickers hardness test was
developed as an alternative to the
Brinell method to measure
the hardness of materials.
The Vickers test is often easier to use
than other hardness tests since the
required calculations are independent of
the size of the indenter, and the
indenter can be used for all materials
irrespective of hardness. The basic
principle, as with all common measures
of hardness, is to observe the
questioned material's ability to resist
plastic deformation from a standard
source. The Vickers test can be used
for all metals and has one of the widest
scales among hardness tests.

8. The unit of hardness given by the test
is known as the Vickers Pyramid
Number (HV) or Diamond Pyramid
Hardness (DPH). The hardness number
can be converted into units of pascals,
but should not be confused with a
pressure, which also has units of
pascals. The hardness number is
determined by the load over the surface
area of the indentation and not the area
normal to the force, and is therefore not
a pressure.

9. The HV number is then determined by the
ratio F/A where F is the force applied to the
diamond in kilograms-force and A is the
surface area of the resulting indentation in
square millimeters. A can be determined
by the formula
where d is the average length of the
diagonal left by the indenter in millimeters.
Hence,
The unit of hardness given by the test is known as the Vickers
Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The where F is in kgf and d is in millimeters.
hardness number can be converted into units of Pascal's, but
should not be confused with a pressure, which also has units of
Pascal's. The hardness number is determined by the load over the
surface area of the indentation and not the area normal to the
force, and is therefore not a pressure. where F is newtons and d is millimeters.

10. Chemical Properties
Iron is a very active metal. It readily combines with oxygen in
moist air. The product of this reaction, iron oxide (Fe 2 O 3 ), is
known as rust. Iron also reacts with very hot water and steam to
produce hydrogen gas. It also dissolves in most acids and reacts
with many other elements.