What is Cold Rolling?
Definition: Cold rolling is a metal rolling operation which is carried out at (or near) the room temperature and the plastic deformation occurs when it is passed through the rollers.
What is Cold Rolled Steel?
Cold rolled steel (also known as CR steel) is a steel which is roll-pressed at (or near) the room temperature to get the desired shape.
In cold rolling operation, the temperature of the metal remains below its recrystallization temperature.
In cold rolling, the strength of the metals increases by around 20% due to strain hardening.
The surface finish of the cold rolled steel (or any other metals) increases and higher dimensional accuracy is achieved.
The cold rolled components include sheets, strips, rods and bars.
The cold rolled metals are usually smaller in size as compared to hot rolled metals.
Cold rolling operation requires a four high rolling mills or cluster rolling mills as the size of the workpiece is small and they are also hard as they are at room temperature.
The amount of thickness that a cold rolling mill can reduce is less than that compared to hot rolling mills.
In cold rolling operation, there are series of shaping operations and the workpiece may be passed through the rollers multiple times to get the final desired shape.
Cold rolled steel examples/uses
The uses/examples of cold rolled steel are;
- Cold rolled steel sheets
- Cold rolled rods
- Cold rolled strips
- Fan blades
- Metal furniture
- Metal cabinets
#1) Cold rolled steel sheets
These are the steel sheets prepared by cold rolling operation.
Steel sheet having more thickness is passed through the flat rollers, and the output sheet with required dimensions is obtained.
This sheet will have more hardness as before (because of strain hardening).
As I mentioned earlier, the surface finish obtained by cold rolling is good and dimensional accuracy is also high.
#2) Cold rolled rods
In this picture, you can see the steel rods manufactured by cold rolling.
#3) Cold rolled strips
Metal strips can also be manufactured by flat cold rolling at room temperature.
The metal strip having higher thickness is passed through the rollers and finally the metal strips of desired dimensions are obtained.
#4) Fan blades
Cold rolled sheets are used for making the blades of fans for boats, ceiling fans, table fans, etc.
#5) Metal furniture
Chairs, tables, beds and other furniture can also be made by using cold rolled sheets and rods.
#6) Metal cabinets
Metal cabinets can also be manufactured from the cold rolled metal sheets.
Advantages of cold rolling
Advantages of cold rolling are listed below.
- In cold rolling operation, 50% to 80% deformation of metals is possible.
- The scale formation as well as oxidation of the metal is negligible which ultimately gives higher dimensional accuracy and better surface finish.
- Workpieces or sheets with thinner walls can be rolled using cold rolling.
- Final properties of the cold rolled metals are easily controllable.
- The strength of the cold rolled metals is high as they undergo strain hardening.
Disadvantages of cold rolling
Disadvantages of cold rolling are listed below.
- Very large amount of forces are required to perform cold rolling operations.
- Small reduction in thickness may lead to surface stresses and non uniform stress distribution.