Product Knowledge Essar Metals

8/12/2019 Product Knowledge Essar Metals

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PRODU T KNOWLEDGE


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An Introduction of Iron Making and Steel Making

Process Flow Diagram


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Cold Rolled Steels

Introduction to Cold Rolling

Processing of CRCA and Essar SteelCapability

Properties and Surface Characteristics of Cold Rolled Steel (CRCA)

Defects in Cold Rolled Steel

Applications of CRCA


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Cold Rolled Steels

What is Cold Rolling ?

process by which hot rolled strip or stock is introduced between rollers

and then squeezed or compressed to the desired thickness

Amount of strain introduced determines the properties of the finished

product


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Cold Rolled Steel

Introduction to Cold Rolling


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Cold Rolled Steels

Why is Cold Rolling done ?

Good Formability

Superior Surface Finish

Reasonable Strength


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Cold Rolled Steels

Commonly used Grades of Cold Rolled Steel

D/DD - Drawing/Deep Drawing Simple forming/bending

applications

EDD - Extra Deep Drawing Deep Drawn components

IF - Interstitial Free Critical Draw and Stretch

Components in terms of

geometry of the component,type and depth of draw and

press parameters


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Cold Rolled Steels

Chemical Composition Typical Ranges

%C %M

n

%Si %S %P %Al N,

ppm

%Ti %Nb

D/DD 0.05 0.3 0.02 0.01 0 0.05 70

EDD


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Cold Rolled Steels

Process flow of Cold Rolled Steel

Pickling (to remove oxides

and scales)Cold Rolling in reversing or

tandem mill to desired

thickness

Annealing (batch or

continuous)for stress

relieving

Skin passing to remove Luder lines,

develop mech prop,impart desired

surface finish improve flatness

Inspection,

Finishing

Dispatch


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Cold Rolled Steels

Pickling

Why is Pickling done ?

To remove scales and oxide layers present on the surface of hot rolled

steel

Make the steel surface suitable for cold rolling

Scales and oxide layers are harder than steel and hence hinder

the process of cold rolling of low carbon steel.


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Cold Rolled Steels

Pickling

Hows scale and oxide removal are achieved?

Hot rolled strip is passed through tanks containinghydrochloric acid wherein the acid dissolves the

oxide layer

The strip is then rinsed with water to remove anyexcess acid. dried and the strip is ready for cold

rolling


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Cold Rolled Steels

Cold Rolling

Hot rolled Pickled Coils are reduced to the desired thickness

Achieved either in;

Reversing Cold Rolling Mills : Thickness achieved byrepeated passes through thesame rolling stand back andforth

or

Tandem Cold Rolling Mills : Thickness achieved throughseries of rolling stands intandem


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Cold Rolled Steels

Annealing

Why annealing is done?

Steel Coils are hard and brittle after Cold Rolling

Has Elongated grain Structure

Not suitable for end use


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Cold Rolled Steels

Skin Passing

Why is Skin Passing Done ?

To remove Yield point by supplying load

To prevent occurrence of stretcher strains in annealed steel

To impart desired surface finish - matte on the strip surface

To improve strip shape


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Cold Rolled Steels

Skin Passing

What are Stretcher Strains?

Generated due to the yield point phenomenon

exhibited by cold rolled and annealed low carbon

steel sheet/strip

Appears as discrete bands on the strip surface


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Cold Rolled Steels

Defects in cold Rolled Steels

Surface Defects

Rolled in Scales

Left over oxides formed during hot rolling Rolled into the sheet surface remaining unremoved even after pickling

Slivers

Defect mainly caused by alumina inclusions entrapped during steel

making/casting operations Gets elongated linearly by rolling

Leads to cracking/failure during drawing operation


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Cold Rolled Steels


Surface Defects

Roll Marks

Defect transferred to the strip from the rolls Appears at regular intervals in the rolling directions Caused due to scratches on rolls , foreign substance sticking to

rolls, metal pick up on rolls during strip breakage


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Cold Rolled Steels


Surface Defects

Sticker Marks

Semi circular marks on the surface of the strip. Generates due to sticking tendency of subsequent coil wraps

Sticking tendency is due to any of the following reasons Higher tension of the coils being taken for annealing Higher soaking time/temperature Poor shape of the strip


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Cold Rolled Steels

Application of Cold Rolled Steel (low Carbon)

Automobile components

Panels for White Goods/Appliances

Packaging (Drums ,Barrels and Containers)

Furniture

Electrical Panels

General Engineering


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Cold Rolled Steels

Application of Cold Rolled Steel (low Carbon)

Exposed Component

UN-exposed Component Critical draw Components

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