GENERAL PROPERTIES OF IRON\\ Physical\\ Mechanical\\ Chemical

____Iron____

____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.

____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.

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, asmaller force is used; for hardermaterials, a tungsten carbide

 ball issubstituted for the steel ball.

Theindentation is measured and

hardnesscalculated as:

where:P = applied force (kgf)D = diameter of indenter (mm)d = diameter of indentation

(mm)

____Brinell 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.

____Rockwell test_____

The Vickers hardness test wasdeveloped 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.

____Vickers Hardness Test____

The unit of hardness given by the test

is known as the Vickers PyramidNumber (HV) or Diamond

PyramidHardness (DPH). The hardness

number can be converted into units of 

pascals,but should not be confused with

apressure, 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.

 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 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.

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,

where F is in kgf and d is in millimeters.

where F is newtons and d is millimeters.

Chemical PropertiesIron is a very active metal. It readily combines

with oxygen inmoist 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.