The objectives of plastic forming include obtaining a desired shape and improving other attributes, such as mechanical properties. For example, during plastic forming of steels, large crystals that exist inside cast steel body become broken into small, elongated crystals, thus transforming this usually brittle cast iron into a ductile and tough material. To accomplish this, it is often necessary to reduce the cross section of a cast structure to one-tenth or even less of its original cross section area.

Rolling is conducted by applying external mechanical forces to overcome the strength of the solid material. This process is limited not only by the power exerted by tools, but also by the plasticity manifested by the workpiece. Plasticity increases with temperature, while the resistance to plastic deformation of a heated solid decreases. This is why the hot rolling processes are carried out at elevated temperatures: solids are heated using high capacity reheating furnaces before they are shaped. Cold rolling is also broadly applied as a secondary process for making a variety of products of smaller cross-sectional dimensions. For metallic materials, and especially for steels, a distinction between cold and hot working is due to the occurrence (or absence) of recrystallization processes within the internal structure of the material. When a steel is formed at temperatures above 0.5^.Tm, (where Tm = melting temperature in degree Kelvin) the phase transformation called recrystallization converts the internal structure into newly formed polycrystals. If a steel is formed at temperatures below 0.3^.Tm, recrystallization processes do not usually take place, which means that the internal structure will preserve the orientation and geometry introduced by the deformation process itself. 

Hot rolling of steel is relatively new technique, probably due to the fact that steel was not available in large quantities until the end of seventeenth century. By the end of seventeenth century, hot mills using grooveless (“flat”) rolls were being employed to reduce the thickness of cuboids into sheets. At the present time, hot rolling mills can produce up to one mm thickness, but the usual minimum thicknesses are larger especially when rolling velocity reaches 15 m/s and over. Steel wire can be hot rolled with diameters as small as 5 mm at velocities as high as 100 m/s. Perhaps the major drawback of hot rolling is the surface oxidation. Loss due to oxidation increases with the surface area and temperature of the rolled steel.