The Term ‘property’ in a broader sense, may be defined as the quality, which defines the specific characteristics of a metal. A detailed study of all the properties of a metal provides a sound basis for predicting its behavior in manufacturing shop and also in actual use. As a matter of fact, the following properties of a metal are important for an engineer, to enable him in selecting suitable metals for his various jobs.
Physical properties – These include shape, size, color, luster, specific gravity, porosity, structure, finish etc.
Mechanical properties – These include elasticity,plasticity, ductility,brittleness, hardness, toughness, stiffness, resilience, creep, strength, malleability, Machinability etc.,
Thermal properties – These include specific neat, thermal conductivity thermal expansion, latest heat, thermal stresses, thermal shock etc.
Electrical properties – These include conductivity, resistivity, relative, capacity, dielectric strength etc.
Magnetic properties – These include magnetic and non magnetic etc.,
Chemical properties – These include atomic weight, equivalent weight, molecule weight, acidity, chemical composition, conosion etc.
Mechanical properties – The mechanical properties of a metal are those properties which completely define its behavior under the action of external loads or forces.
- Elasticity – The term ‘Elasticity’ may be defined as the property of a metal by virtue of which it is able to retain its original shape and size after the removal of the load. The elasticity is always desirable in metal used in machine tools and other structural members.
- Plasticity – The term ‘Plasticity’ may be defined as the property of metal by virtue of which a permanent deformation takes place, when ever it is subjected to the action of external for us. The plasticity of a metal depends upon its nature and the environmental conditions. This property finds its use in forming, shaping and extruding operations of metal.
- Ductility – The term ‘Ductility’ may be defined as the property of a metal by virtue of which it can be drawn into elongated before rupture takes place. It depends upon the grain size of the metal crystals. The measures of the ductility of a metal are its percentage elongation and percentage reduction in the cross sectional area before rupture.
- Brittleness – The term Brittleness’ may be defined as the property of a metal by virtue of which it will fracture without any appreciable deformation. This property is opposite to the ductility of a metal. Cast Iron and glass are the example of brittle materials. This property finds its importance for the design of machine tools, which are subject to sudden loads.
- Hardness – The term v Hardness’ may be defined as the property of a metal by virtue of which it is able to resist abrasion, indentation and scratching by harder bodies. It i s measured by the resistance of the metal which it offers to scratching.
- Touchness – The term ‘ Toughness’ may be defined as the property of a metal by virtue of which it can absorb maximum energy before fracture takes place. Tenacity and Hardness of a metal are the measures of its toughness, The importance of toughness is in the selection of a material where the load increases beyond the elastic limit.
- Stiffness – The term ‘ Stiffness’ maybe defined as the property of a metal by virtue of which it resists deformation. The stiffness of a metal is of importance while selecting it for a member or a component of a machine. Stiffness of a metal is also made use in graduating spring balances and spring controlled measuring instruments.
- Resilience – The term ‘Resilience’ may be defined as the property of a metal by virtue of which it stores energy and resists shocks or impacts. The resilience of a metal is of great importance in the selection of materials used for various types of spring.
- Creep – The term ‘Creep’ may be defied as the property of a metal by virtue of which it deforms continuously under a steady load. Generally, the creep occurs in steel at higher temperature. Creep is always considered while designing IC engines, boilers, turbines etc.
- Strength – The term’ Strength’ may be defined as the property of a metal by virtue of which it can with stands an external force or load without rupture. The strength of a metal is the most important property which plays a decisive role in designing various structures and components.
- Malleability – The term ‘Malleability’ may be defined as the property of a metal by virtue of which it can be deformed into thin sheets by rolling or hammering without rupture. It depends upon the crystal structure of the metal.
- Machinability – The term ‘Machinability’ may be defined as the property of a metal which indicates the ease with which it can be cut or reinoved by cutting tools in various machining operations such as turning, drilling, boring milling etc. The machinability of a metal depends upon the mechanical and physical properties of the metal, chemical composition of the metal microstructure of the metal and the cutting conditions.
- Ductility – The term percentage of Elongation is the maximum increase in the length expressed as percentage of original length.
Increase in length
Percentage Elongation = ————————— X 100
The term percentage reduction of cross sectional area is the maximum decrease in cross- sectional area, expressed as the percentage of the original cross- sectional area.
Decrease in cross – sectional area
Percentage reduction in cross sectional area =————————————————— X 100
Original cross sectional area