What is mechanical working of metals ?

Subsequent to casting, further shaping operations are frequently desirable either to produce a new shape or to improve the properties of the metal. Shaping in the solid state may be divided into "non-cutting shaping" or "non-chipping shaping" such as forging, rolling, pressing, etc., and "cutting shaping" or "chipping shape giving" including the machining operations of  various machine tools. Non-cutting shaping are referred to as mechanical working processes. 

Mechanical working of metal is simply a plastic deformation performed to change dimensions, properties and /or surface condition by means of mechanical pressure. Mechanical working may be either hot working or cold working depending on temperature, and strain rate such that recovery processes take place simultaneously with the deformation.

Plastic deformation above recrystallization temperature, but below the melting or burning point, is hot work. Some metals, such as lead and tin, have a low re-crystalline range and can be hot-worked at room temperature, but most commercial metals require some heating.

Plastic deformation below the recrystallisation temperature is cold work. Although normal room temperatures are ordinarily used for cold working of steel, temperatures up to the recrystallisation range are sometimes used. In cold working , recovery processes are not effective. It is , therefore, important to realize that the distinction between hot working and cold working does not depend upon any arbitrary temperature, but also on the recrystallisation temperature of deformation.