Cold working is the process of strengthening material by changing its shapes without the use of heat. In this process, the material is deformed below the recrystallization temperature. The recrystallization temperature generally varies between one third to half the melting point of most of the metals. The major cold working process is rolling, bending and drawing etc.
Cold rolling is widely used for strengthening the metal, in which work is compressed between two rollers due to this grain size decreases so strength and hardness increases And Ductility decrease.
During cold working, the microstructure is permanently deformed with the grains being elongated in the direction of the applied forming stress.
EFFECTs ON GRAIN SIZE : –
Since in cold working material is pressed by roller so due to compressive force materials get compressed and the grains of the material comes close to each other and small gains which are known as Fine-grain. After the cold working process material becomes brittle in the structure and hardness of material increases.
Cold working is a metal forming process it is generally done for materials which have high recrystallisation or melting point temperature. It’s also called work hardening process or work strengthening process because it increases strength and hardness.
In this process strain hardening is take place so the materials obtained from cold working can not go for further deformation or in other words after the strain hardening, the maximum amount of deformation that can be given is limited.
Cold worked items suffer from a phenomenon known as spring back, or elastic spring back. After the deforming force is removed from the workpiece, the workpiece springs back slightly. The amount of material springs back is equal to the yield strain.
The most common application of this process is steel, aluminium, nickel, titanium and copper etc.