Learn with steem || Tutorial class 2 || Mechanical Engineering|| Topic- Rolling process || 25 % beneficiary set to Null

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Namaste Steemit,

Hello friends, how are you all, hope all is well, today I am going to write my second post about my in front of you subject. Now todays post is based on my previous post so before start to read my post please check my previous post. Link is given at the end of my post.

ROLLING

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Definition- The process of plastically deforming metal bypassing it between rolls it's called or rolling process.

• Most widely used, high production rate and closed tolerance.
• The Friction between the rolls and the metal surface produces a high compressive stress.
• Hot working (unless mentioned cold rolling)
• Metal will undergo bi axial compression.

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Hot Rolling

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• Done above the recrystallization temperature.
• Results in fine grain structure.
• In hot rolling the surface quality and final dimensions are very less accurate.
• Breakdown of ingots into blooms or billets is done by hot rolling.

This is followed by further hot- rolling into plate, sheet, rod, bar, pipe and rail.

• Hot rolling is terminated when the temperature falls to about 50 to 100 degree Celsius above the recrystallization temperature.

COLD ROLLING

• Done below the recrystallization temperature.
• Products are sheet, strip, foil etc. With good surface finish and increase mechanical strength with close product dimensions.
• Performed on four- high or cluster type rolling mills because it generate high force and power.

Lubrication for rolling

• In Hot rolling of ferrous metal is done without a lubricant.
• Hot rolling of non- ferrous metal of wide variety of compounded oil and use emulsions and fatty acids
• Generally Cold rolling lubricants are water soluble oils, low- viscosity lubricants such as mineral oils, emulsions paraffin and fatty acids.

HOT vs COLD ROLLING OF METALS

Hot Rolling	Cold Rolling
Generally Metal is fed to the rules after being heated above the recrystallization temp.	In this case Metal is fed to the rules when it is below its recrystallization temp.
The Rolled metal does not show work hardening effect.	After being cold rolled the metal shows the work hardening effect
You can see the heavy reduction in the workpiece.	Heavy reduction is not possible in this case.
Mechanical properties is improved.	In this case Hardness increases excessive cold working generates cracks.
Blow holes and other similar defect present in the ingot are removed.	Ductility of the metal reduces.
Due to hot rolling very thin sections are not obtained . Hot rolling of sheets less than 1.2 mm in thickness is not econ.	Cold rolling increases the tensile strength and yield strength of steel metal.
The hot rolling is widely used in ferrous as well as non ferrous industry for steels, aluminium, copper, brass, bronze, magnesium, Nikhil and zinc alloy to change ingot into billets, slabs, sheets, bars, rods, wires and tubular shapes.	Aluminium foil as thin as 0.020 mm can be made.
The hot roll surface finish is not good.	The cold roll surface is smooth and free from oxide.

I hope you liked this tutorial series of mechanical engineering subject and please tell me in the comments, what you liked in this tutorial.

Note- First you read my previous post Link

Beneficiaries of this post:

@steemindiaa: 10%
@null: 25%