____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 evaluatedusing a variety of tests, including the Brinell test, Rockwelltest and the Vickers hardness test.The Brinell scale characterizes the indentation hardness ofmaterials through the scale of penetration of an indenter, loadedon a material test-piece. It is one of several definitions ofhardness in materials science.It was the first widely used and standardized hardness testin engineering and metallurgy.
____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)
____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.
____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 materials 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.
The unit of hardness given by the testis known as the Vickers PyramidNumber (HV) or Diamond PyramidHardness (DPH). The hardness numbercan be converted into units of pascals,but should not be confused with apressure, which also has units ofpascals. The hardness number isdetermined by the load over the surfacearea of the indentation and not the areanormal to the force, and is therefore nota 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, The unit of hardness given by the test is known as the VickersPyramid 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 Pascals, butshould not be confused with a pressure, which also has units ofPascals. The hardness number is determined by the load over thesurface area of the indentation and not the area normal to theforce, and is therefore not a pressure. 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 ), isknown as rust. Iron also reacts with very hot water and steam toproduce hydrogen gas. It also dissolves in most acids and reactswith many other elements.