CST ARCELOR BRAZIL Compact hot strip mill - SMS … ARCELOR BRAZIL Compact hot strip mill FLAT ROLLING MILLS ... also included a hot skin-pass mill and a ... Layout of hot strip mill

CST ARCELOR BRAZILCST ARCELOR BRAZILCompact hot strip mill

FLAT ROLLING MILLS

Hot Strip Mills

SMS metallurgy

Companhia Siderúrgica de Tubarão (CST)in Vitoria, Brazil, had chosen SMS Siemagto supply a complete 1,880-mm compacthot strip mill which went on stream in2002. We implemented this turnkey pro-ject as the leader of an international con-sortium which comprised Toshiba Corpo-ration, VAI-UK and SMS Siemag Ltda. Inaddition to the hot strip mill, the projectalso included a hot skin-pass mill and ashear line for hot-rolled strip. The firststrip was rolled on August 31, 2002.Right from the start of production, thehot strip mill exceeded the contractuallyagreed capacity.

Until that time, Companhia Siderúrgicade Tubarão had operated a fully inte-grated steelworks with two continuouscasting facilities. With the new hot stripcomplex, the Brazilian steelmaker hasexpanded its product range to includehot-rolled coils. We had already suppliedseveral facilities to the Vitoria works:

1979 Slabbing mill1995 Two-strand continuous slab caster

No. 11997 Blast furnace No. 2 for maximum

4,000 t /day1998 Two-strand continuous slab caster

No. 2 for twin-casting1999 RH plant

TURNKEY PROJECTTURNKEY PROJECT

Hot Strip MillsSMS SIEMAG

2

Continuous casting plants, slab yard and hot strip mill (from right to left) form one functional unit.

Strip travel between thefinishing stands.

Transfer bar in the coilbox.

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CONTENTS

Introduction 2

Integration into theexisting steelmaking plant 4

Product range 6

Furnace and roughing mill 8

Coilbox and crop shear 10

Finishing mill 12

Cooling system and coilers 14

Technology packages 16

Slab.Transfer bar.

INTEGRATION INTO THE EXISTINGSTEELMAKING PLANTINTEGRATION INTO THE EXISTINGSTEELMAKING PLANT

Layout of hot strip mill and roll shop.


4

To ensure high cost-effectiveness of theproduction line, the new hot strip millwas arranged close to the existing con-tinuous casting facilities.

Right after casting, roller tables conveythe slabs from the two casters to theslab yard from where one of the fivecranes carries them either to the speci-fied storage location, or into one of thetwo heat-insulating pits for controlledcooling of special materials, or directly tothe furnace approach roller table. Thanksto the short transport routes, a largeshare of the slabs can be hot-charged.

On their way from the slab yard to thehot strip mill, the slabs have to overcomea level difference of 6.0 m. Because ofthe nearby ocean, the rolling mill waserected on an elevated level to preventproblems with groundwater. Anotheradvantage of this arrangement is that theutility supply systems (oil systems, pres-sure-water station, etc.) that are normallyaccommodated in the cellar are moreeasily accessible.

The coil storage area. Automatically actuatedcoil car.

5

Mandrel-less coilbox

Homogeneous transfer-bar temper-atureSmall finished-strip thicknesses incase of harder materials

Hydraulic adjusting systems

and loopers

Low frictionSmall moment of inertiaClose thickness tolerancesStable strip flow

CVC technology

Flat and reproducible strip profilesExcellent strip flatnessFlexible rolling programLonger rolling programs

Roll-gap conditioning

(roll cooling, roll-gap cooling,

roll-gap lubrication)

Excellent strip surfaceLonger roll service livesReduced rolling forces

TECHNICAL FEATURES AT A GLANCE

25

20

15

10

5

0

[ 100

,000

t ]

Production recordsJune 2006 233,019 tAugust 2006 246,249 tSeptember 2006 235,829 tDecember 2006 234,005 t

2002 2003 2004 2005

2,34

0,78

0

1,94

3,10

7

1,19

2,04

5

2006

2,70

8,59

5

Continual increase of production(First strip: August 31, 2002).

PRODUCT RANGEPRODUCT RANGE


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So far a supplier of high-quality slabs,CST is now also producing premium-quality hot strip on the new rolling mill.The company soon managed to branchout into the market for vehicle externalskin. In addition, the product spectrumincludes hot strip for carbody elements,pipes for gas and oil pipelines, ship-build-ing, household appliances and the con-struction industry.

The products feature close tolerances in geometrical dimensions and materialproperties as well as excellent surfacequality. Our TGHR Thin-Gage Hot Rollingtechnology package enables the produc-tion of high-quality hot strip down to aminimum gage of 1.0 mm. The rollingmill is moreover able to roll stainlesssteels.

The current nominal capacity of the hotrolling mill amounts to 2.0 million t /year,a value that has already been exceededby nearly 20% in 2005. The rolling millwas designed so that capacity can beboosted in steps to 3.4 million t /year, and then to 4.2 million t /year.

High-quality slabs cast on CST’scontinuous casters.

Cold rolling and galvanizingDistribution centersMechanical tubingCold rollingAutomotive

Pipelines and casingsAutomotive wheelsCivil constructionDrawingOther applications

5 %5 %

2 %

43 %

20 %

9 %

1 %

6 %

3 %

6 %

7

SLAB DATA

Steel grades Structural steelsULC steelsIF steelsHigh-carbon steelsHigh-strength, low-alloyed steels

Slab thickness 200 to 250 mmSlab width 750 to 1,955 mmSlab length 4,500 to 11,500 mmSlab weight max. 40 t

STRIP / COIL DATA

Strip thickness (1.0) 1.2 to 16.0 mmStrip width 700 to 1,880 mmCoil inside diameter 762 mmCoil outside diameter2,100 mmSpecific coil weight max. 22.5 kg/mmTotal weight max. 40 t

Fields of application of CST’s hot strip in 2006.

FURNACE AND ROUGHING MILLFURNACE AND ROUGHING MILL

As soon as the bay crane has placed theslab on the furnace approach roller table,it is weighed on the slab weighing rollertable and then carried to the slab charg-ing machine. Inside the 400-t/h walking-beam furnace, the slab is heated fromcharging temperature to approx. 1,250 °C.To maximize furnace utilization, especiallywhen handling short slabs, the furnace is equipped with two separately drivenwalking-beam sections. Following dis-charging, the heated slab is placed onthe hot-side furnace roller table. For emergency situations, an extensionroller table is available to return the slabto the slab yard.

During passage through the hydraulichigh-pressure descaling system (primarydescaler and spraying headers for descal-ing in the roughing stand), furnace scaleis removed from the slab surface. Five toseven passes are run in the four-highreversing stand to roll the slab down tothe desired transfer-bar thickness. Theedger attached on the entry side servesto set the transfer-bar width. The maxi-mum net width reduction is 75 mm.Space has already been reserved forinstallation of a second roughing stand.


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The heated slab is dis-charged from the furnace.

The slab leaving the primary descaler.

Slab charging into the furnace.

Roughing stand with attached edger.

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TECHNICAL DATA

Walking-beam furnace

Digital burner technology (for optimal

combustion and reduced gas consumption)

Production capacity (per furnace) 400 t /h

Maximum slab length

single-row operation up to 11,500 mm

Maximum slab length

two-row operation up to 5,500 mm

Edger

Roll diameter 1,200 to 1,100 mm

Maximum edging force 7,000 kN

Maximum width

reduction 85 mm per pass

Gap 700 to 2,050 mm

Main drive 2 x 1,500 kW

Rated torque at the rolls 2 x 463 kNm

Roughing stand

Work roll diameter 1,250/1,150 mm

Backup roll diameter 1,530/1,350 mm

Barrel length 2,050 mm

Rolling force 40,000 kN

Main drive motors

- Nominal rating 2 x 7,500 kW

- Rated torque 1,433 kNm

Roller table from the slabyard to the furnace.

COILBOX AND CROP SHEARCOILBOX AND CROP SHEAR


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During the final pass, the roughing standand the coilbox, which serves as heataccumulator, operate in tandem mode.Due to temperature equalization, thehead and tail of the transfer bar featurean identical temperature level as they runinto the finishing mill. This results in con-stant rolling-force and speed levels in thefinishing mill, which in turn assists rollingof ultra-thin strip (down to 1.0 mm) withhigh coil weights.

Transfer from the coiling station to theuncoiling station is accomplished withoutmandrel, thus avoiding local temperaturedifferences on the inner windings. Inaddition, this smooth process preventssurface damage.

The coilbox attains high coiling speeds.To implement very short cycle times, onetransfer bar can be coiled while anothertransfer bar is running from the uncoilingstation into the finishing mill.

The drum-type shear crops the transfer-bar head and tail, with an automatic crop-length optimization system ensuring mini-mum crop ends. To optimize the contourof the crop cut, the drum-type shear isequipped with one knife each for headand tail cropping.

Before the material runs into the finishingmill, it is freed from fresh scale by meansof the finishing mill’s descaler.

Coiling of the transfer bar. Uncoiling begins. Uncoiling.

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TECHNICAL DATA

Mandrel-less coilbox

Transfer-bar thickness 20 to 40 mm

Transfer-bar width 700 to 1,880 mm

Entry speed max. 3.0 m/s

Coiling speed max. 4.5 m/s

Uncoiling speed max. 2.0 m/s

Drum-type crop shear

Design rotating drum

Maximum strip

cross-section 40 x 1,880 mm

Maximum shear force 12,000 kN

Transfer-bar speed during

cutting 0.4 to 1.5 m/s

Number of shear knives

per drum 2/180° offset

Drum-type shear.

Entry side of the finishing mill with coilbox, crop shear and descaler.

To attain maximum product quality, thesix-stand finishing mill incorporates awhole range of high-tech control and actuating elements. All of the stands areequipped with fully hydraulic AGC cylin-ders (Automatic Gage Control) for roll-gapsetting and thickness control, as well asCVC systems (Continuously VariableCrown) for profile, contour and flatnesscontrol. The roll conditioning system,which comprises the roll and interstandcooling systems, the anti-peeling deviceand the roll-gap lubrication system, safe-guards top strip surface quality along withextended work-roll service lives.

Another feature of the new rolling mill is our technology package for thin-striprolling (TGHR – Thin-Gage Hot Rolling).High-speed AGC systems, combined withlow-inertia hydraulic loopers for stands F1 to F3 and segmented tensiometerloopers for stands F4 and F5, permit cost-effective production of thin strip withgages so far attained only through coldrolling.

The step-wedge system in the last finish-ing stand keeps the passline constantdespite different work roll diameters.Thanks to a high-speed roll changingdevice, the work rolls can be changedautomatically in just a few minutes. Locomotives transport the work rolls from the rolling bay straight to the rollshop and back.

FINISHING MILLFINISHING MILL


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Finishing stand with CVCshifting system.

Stable strip flow betweenthe stands.

The six-stand finishing mill.

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TECHNICAL DATA

Finishing mill

Total rolling force 40,000 kN

Work rolls:

Diameters F1 to F3 820/720 mm

Diameters F4 to F6 700/620 mm


Backup rolls:

Diameters F1 to F6 1,530/1,350 mm


Bearings Morgoil® bearings

Main drive motors:

- Nominal rating 6 x 8,000 kW

Fully-automatic roll change.

LAMINAR-FLOW COOLING

LINE

After leaving the finishing mill, the stripruns through the laminar-flow cooling linewhich comprises 13 groups with micro-zones and two groups with trimmingzones to set the desired coiling tempera-ture. The X-Pact® cooling model serves toselect the cooling rates and coiling tem-peratures so that the specified materialproperties will be attained within closetolerances.

COILERS

At the end of the hot strip mill, two coil-ers with associated hydraulic sideguidesand pinch roll units coil the rolled strip atvery short strip cycle times. All adjustingfunctions are implemented in servo-hydraulic mode. The Step Control systemfor the wrapper rolls ensures that striptension is built up very quickly and in amanner protecting both the mechanicalequipment and the material to be coiled.In addition, marks on the inner windingsare prevented.

The downstream coil handling systemconveys the coils by means of walkingbeams to a transfer station from whereautomatically actuated coil cars carrythem to the coil storage area.

COOLING SYSTEM AND COILERSCOOLING SYSTEM AND COILERS


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The laminar-flow cooling line withelevated tank in the background.

Hydraulic sideguides upstream ofthe pinch roll unit and the coiler.

Coil hauloff.

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Laminar-flow coolinggroups.

TECHNICAL DATA

Laminar-flow cooling system

Total flow volume 9,750 m3/h

Cooling groups

- with microzones 13

- with trimming zones 2

Coilers

Thickness range 1.0 to 16.0 mm

Maximum coil weight 40 t

Maximum outside diameter 2,100 mm

Mandrel diameter (spread) 762 mm

Mandrel drive

- Motor rating 800 kW

- Nominal torque 1,433 kNm

TECHNOLOGYPACKAGESTECHNOLOGY PACKAGES

A WINNING COMBINATION

OF PROVEN TECHNOLOGY

AND NOVEL SYSTEMS

Stable production of the high share ofultra-thin strip is ensured by the seg-mented tensiometer loopers that areinstalled downstream of stands F4 and F5 of the finishing mill. These systemsdetect and measure the strip tension dis-tribution across the strip width, and thisdata serves as input information for stripflow control as well as profile, contourand flatness control.

With the aid of proven control elements,high-speed hydraulic adjusting systemsand low-friction loopers, the strip flowcontrol system safeguards stable stripflow also when handling ultra-thin strip,and minimizes strip tail-end crashes.

Profile, contour and flatness control isimplemented through the proven CVCtechnology (work-roll shifting and bend-ing). CVC plus technology systems offer a wider profile control range, and can be retrofitted with but minimal work oreffort. The desired strip profile is attainedby selecting the adequate CVC shiftingposition. Strip flatness is measured bymeans of the tensiometer loopers down-line of F4 and F5 and the flatness mea-suring system on the exit side of F6, and controlled via the work-roll bending systems.


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Control pulpit for the roughing and finishingmills, overlooking the finishing mill.

Tensiometer looper for stable stripflow and good strip flatness.

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Finishing stand with hydraulic adjusting, CVC shifting and work-roll bending systems.

Screenshot of the finishing mill process.

Stands F1 to F3 and F4 to F6 eachrequire rolls with just one contour whichreduces the amount of work in the rollshop and the number of required rollsets as compared to conventionallyground rolls.

The process model for profile, contourand flatness control cyclically calculatesthe elastic deformation, the thermal crownand the amount of wear of the roll sets,and ascertains the resultant contour ofthe strip cross-section.

Knowing exactly what the strip contour islike makes it possible to minimize profileanomalies by means of contour-optimizedshifting strategies. This allows greaterflexibility in program planning with a largevariety of finished-strip dimensions andmaterial strengths within one rolling pro-gram, or the successive rolling of a largernumber of strips with the same width.

These technological functions for ensur-ing stable production of hot strip withinclose tolerances in terms of geometricaldimensions and material properties wereimplemented in combination with SMSSiemag’s X-Pact® automation systems.

TECHNOLOGY PACKAGESTECHNOLOGY PACKAGES


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Control pulpit in the coiler area.

X-Pact® automation systems are easyto maintain.

Coiler with AutomaticStep Control.

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Das neue Vorgerüst wird in die Wal-zlinie geschoben.

X-PACT® AUTOMATION COM-

PONENTS IN THE CST HOT

STRIP MILL

Strip-thickness and mass-flow

control

Roll gap control under load (AGC) withdynamic correctionof disturbing variablesThickness control via thickness-gagemonitorAutomatic leveling by means of the RollAlignment Control for stable strip flowHighly dynamic loop- and strip-tensioncontrol for constant strip tensionfrom the head to the tail “Flying” gage changes for thin strip ofless than 1.2 mm

Strip profile, contour and flat-

ness control

Process model for profile, contour andflatness control (PCFC)More flexibility in planning the rollingprogram through contour-optimizedwork-roll shifting strategiesControl of CVC shifting positionsControl of work-roll bending forcesFlatness control through tensiometerloopers at back of F4 and F5, and the flatness measuring system downline of F6

Control of coiling temperature

Process model to pre-calculate and con-trol the cooling rates and the coilingtemperature to achieve the desiredmaterial properties

Coiler controls for uniform and

straight-edged coils

Control of hydraulic sideguidesControl of pinch roll gapsControl of wrapper rolls including Auto-matic Step Control

Checking the proper functioning without extra measuring instruments.

SMS SIEMAG AG

Hot Rolling Mills Division

Wiesenstrasse 3057271 Hilchenbach, Germany

Phone: +49 (0) 2733 29-1616Fax: +49 (0) 2733 29-2832

E-mail: [email protected]: www.sms-siemag.com

MEETING your EXPECTATIONS

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“The information provided in this brochure contains a general description of the performance characteristics of the products concerned. The actual products may not always have thesecharacteristics as described and, in particular, these may change as a result of further developments of the products. The provision of this information is not intended to have and willnot have legal effect. An obligation to deliver products having particular characteristics shall only exist if expressly agreed in the terms of the contract.”

Documents

CST ARCELOR BRAZIL Compact hot strip mill - SMS … ARCELOR BRAZIL Compact hot strip mill FLAT ROLLING MILLS ... also included a hot skin-pass mill and a ... Layout of hot strip mill