HR Coils

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STEEL

WORLD OF STEEL

HR Coils

Presented By:-

Subhajit Karmakar.

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TEELHot rolling is a hot working metalworking process where large pieces of metal, such as slabs or billets, are heated above their re-crystallization temperature and then deformed between rollers to form thinner cross sections.

What is HR Coils?

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Process at a Glance:-PROCESS AT A GLANCE

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TEEL1. The Hot Rolling Process:-

The starting material is usually large pieces of metal, like semi-finished casting products, such as slabs, blooms, and billets.

In continuous casting, rolling mill is mostly integrated to save energy.

 for larger work pieces  gas- or oil-fired soaking pit

 for smaller work pieces induction heating.

 a finishing temperature is defined (50 to 100 °C above the recrystallization temperature) If the temperature does drop below this temperature the material must be re-heated before more hot rolling.

Manufacturing Process:-

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2. ReheatingCritical to the Hot Strip Mill is its walking-beam reheat furnace, state-of-the art equipment that replaced and now outperforms three older- (pusher-) style furnaces.

3. DescalingAfter exiting the reheat furnace, the slab passes through a descaling unit, an enclosure employing two pairs of

spray headers that blast the intensely hot slab with 1,500 psi pressurized water to remove the 1/8-inch thick layer

of oxidized iron that forms at the surface of the slab in the oxygen-rich atmosphere of the reheat furnace.

4. RoughingThe roughing mill is made up of six independent rolling mill stands, the last four of which incorporate small

vertical rolling mills called edgers. Slabs heated in the furnace until they glow bright orange-yellow are rolled

through one stand at a time to produce so-called transfer bars suitable for finish rolling.

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TEELApproximately 96% of steel is continuously cast (the remaining - ingots ).

After hot rolling the cooling should be done uniformly else residual stress is generated due to shrinkage that affects the mechanical properties.

Mill scale is the oxide layer formed on the surface due to reaction with atmosphere at high temperatures.

Pickling is done with HCl to remove this scale.

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5. Edging

At the very high temperatures at which the steel is rolled in the roughing mill, it is very plastic and ‘flows’ easily like cookie dough beneath a rolling pin. Consequently, as the slab is reduced from eight to nine inches thick to the final bar thickness of one to one and one-half inches, bars tend to spread width-wise by a few inches at their extremities, and by as much as an inch through the body.

6. Descaling

It is Descaled by the low pressure headers. After descaling by the low-pressure headers, the bar is pinched by a pair of pneumatically-actuated rolls to mechanically loosen any remaining scale, which, as the processing temperatures cool off, becomes increasingly sticky even as it returns ever more slowly to the surfaces of the still red-hot steel.

7. Cropping

The head- and tail-ends of nearly every transfer bar are cropped by a pair of large steel drums each with a shear blade extending along its length.

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TEEL8. FinishingPrior to the finish rolling operation, the head- and tail-ends of the transfer bar will be sheared to square them up, helping to ensure proper threading and tail-out. A final two-stage descaling operation is performed to clean off the scale that has grown on the bar during roughing.

Controlling Factors:-I. Temperature Control

II. Gauge Control

III. Flatness & Crown

IV. Laminar Cooling

V. Coiling

VI. Coil Handling

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TEELUsages Of HR coils:-

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TEELGeneral structures:-

Simple cross sections, such as rail tracks, storage tanks, storage bins, tubes & pipes, cold-rolled steel,

Automotive parts:-

High-pressure gas cylinders, oil well pipes, pipelines , bearing plates for buildings and other structural applications.

Other Applications:-

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Application of HR coils in Various product manufacturing:-Tube making

Manufacture of Hamilton and other poles, flanging applications

Manufacture of pipes mostly for oil and gas sector

Cold reduction and for manufacture of galvanized sheets

General structural applications

Strapping, cycle chain

Manufacture of electrical equipment

Structural fabrication

Various applications in auto sector

Manufacture of corrosion resistant structural materials

For high tensile structural applications

Manufacture of propeller shaft

Manufacture of fork for two wheelers

Manufacture of wheel disc

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TEELTypes of HR Coils:-

Hot-rolled Coil

Hot-rolled Sheets

Checkered Plate

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TEELDominated by 6-7 players:-

•  Main :  SAIL, TISCO, Jindal Steel

•  Secondary : Essar Steel, Jindal Vijayanagar Steel Ltd (JVSL), Jindal Iron and Steel Company     (JISCO), Uttam Steel

• The global market price of HR Coils is regarded as an indicator of the market trend of all its downstream products in the flat product segment.

• Its downstream products like CR Sheets / Coils, GP/GC Sheets, Electrical Steel, Sheets, Tinplate, Pipes etc. play a vital role in the industrial development of a country.

Major players :-

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Some More User:-•Railways•Power •Irrigation•Coal •Oil•Product & Technology•Furniture makers•Consumer durables•Agricultural Implements 

User segments •Pipes & tubes and CR coils major users of HR coils

•CR coils used mainly for automobiles, consumer durables, general engineering, construction as galvanized products

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Products, characteristics and application

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