Summary

Hi guys In this lecture we study the  main Differentiate between Hot rolling and Cold rolling so let's discuss further information,

Differentiate between Hot rolling and Cold rolling

Hot Rolling

Hot rolling carried out to roll ingots into slabs,billets. On further hot rolling plates.l, bar rounds, structural shapes and rails are obtained. Because of limitations in equipment and workability if metal rolling is done is progressive steps.

Hot rolling is a manufacturing process used to shape metal into various forms like sheets, bars, or coils. It involves heating the metal above its recrystallization temperature, making it easier to deform. The heated metal is then passed through a series of rollers, which apply pressure to shape it into the desired thickness and shape. 

Hot rolling is typically used to create larger and thicker metal pieces with a wide range of shapes and sizes. It's commonly used in industries like construction, manufacturing, and transportation to produce items like beams, rails, and large metal plates.

Hot rolling

 

Cold rolling:-

Cold rolling is a process used in manufacturing to shape metal sheets and strips. It involves passing the metal through a pair of rollers at room temperature, which compresses and elongates the material, reducing its thickness and altering its surface finish.

 Unlike hot rolling, where the metal is heated before rolling, cold rolling is done at ambient temperature. This method is commonly used to produce thinner and smoother metal sheets with precise dimensions, often used in industries like automotive, construction, and appliances.

For many purpose particularly where steel strip has to be blanked and form in presses it made by a process of cold rolling

Object of cold rolling-

1) To secure improved surface finish.

2) To obtain small and more uniform thickness than is possible in hot rolling.

3) To give the metal improved Physical properties by combining the cold work with suitable heat treatment.

Cold rolling

Cold rolling is employed to finish bars, rods, sheets, and strips of most common metals because of this process provide better dimensional accuracy, good surface finish and improved physical properties.

Comparison between hot rolling and Cold rolling

What is difference between Hot rolling and Cold rolling?

Hot rolling	Cold rolling
1. Metal is fed to the rolls after being heated above the condensate temperature.	1. Metal is fed to the rolls when it is below  the condensate temperature.
2. Rolled metal does not show work hardening effect.	2. After being cold rolled metal shows work hardening effect.
3. Co- efficient of friction between the rolls and stock is higher.	3. Co- efficient of friction between the rolls and stock is lower.
4. Experimental measurements are difficult to make.	4. In cold rolling experimental measurements easily carried out.
5. Heavy reductions in area of the workpiece can be obtained.	5. Heavy reductions are not possible.
6. Yield stress varies with the temperature varies with each pass therefore hot rolling presents more problem formulating a theory than cold rolling.	6. Theoretical analysis can be easily carried out and considerably developed theory is available.
7. Mechanical properties are improved by breaking cast structure and refining grain size.  The strength  of metal increases.	7. Hardness increases excessive cold working generate cracks. Reduces ductility. Cold rolling increases.
8. Rolled radius is generally larger than used in cold rolling.	8. Rolled radius is generally smaller.
9. Very thin sections not obtained by hot rolling. Hot rolling sheets less than 1.25 mm thickness is not economical.	9. Aluminum foils as thin 0.020 mm can made.

In this lecture we study the Differentiate between Hot rolling and Cold rolling in machine tools and processes hope you understand well.

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