Hot and cold working of metals

. advantage and disadvantage of hot working metal

. advantage and disadvantage of cold working of metal

Working on metals

This involves the manipulation of metals /materials when in the solid state

Examples of working are forming, rolling, forging etc.

Working processess can be classified

Hot working

Cold working 

Hot working 

Hot working is done at a suitable high temparature so that any damage to the grains is repaired. The temparature required varies from metal to metal.

Examples of hot working

Forging, rolling, extrusion et

Advantage of hot working

-hot working is relatively a low cost process

-refinement of grain from cast structure is possible.

-the scale givea some protection against corrosion during storage.

After the process also the product will be in the fully annealed condition, suitable for further cold working.

Disadvantage of hot working

-poor surface finish is likely

-dimensional inaccuracy is possible due to shrinkage on cooling

-geometrical accuracy is possible due to distortion on cooling

Cold working

Cold working is done at room temaprature. Due to the reason the grains become distorted.

Cold working increases the  hardness and strength of the material at the expense of ductility, and the metal is said to be work hardened. This work hardening increases the strength and rigidity.

Cold Woking must not be used for large deformation unless the metal is frequency heat treated to keep it ductile.

Examples of cold Working

Sheet metal pressing, rivet head forming, cold extrusion etc

Advantage and disadvantage of cold working

-good surface finish, high dimensional and geometrical accuracy is possible

-at times this process is used for finishing a previously hot worked part. Due to this the processing cost may be more

-materials lack ductility due to work hardening and are less suitable for bending etc.