Classification of Rolling mills...

Classification of Rolling mills Rolling is the process of plastically deforming metal by passing it between rolls. It is the most widely used forming process, which provides high production and close control of final product. Leonardo da Vinci invented the first rolling mills but only after a few centuries rolling mills became important for the steel industry. In its simplest form, a rolling mill (Fig 1) consists of two driven rolls in a mill stand with a screw down. The work piece to be rolled is passed through the rotating rolls to get the desired shape. Fig 1 A simple rolling mill But in practice rolling mills are not that simple. They are quite complicated and they are of several types. Though all the rolling mills utilize the same principle of rolling but they differ in many ways. The classification of mills can be done in many ways. These are described below. Classification based on temperature of rolling Under this classification, rolling mills are classified according to the temperature of the metal to be rolled. Based on this classification rolling mills are basically of two types: (i) hot rolling mill (ii) cold rolling mill. Hot rolling mills – In these mills, rolling is done above the recrystallization temperature of the metal. During rolling in these mills the grains, which deform during the process of rolling, recrystallize, maintain an equiaxed microstructure and prevent the metal from work hardening. In this type of rolling hot rolled metals have very little directionality in the mechanical properties and deformation induced residual stresses. Cold rolling mills – In these mills, rolling is done below the recrystallization temperature of the metal. Rolling in these mills which is normally done at the room temperature, increases the strength of the metal through...