Spray Nozzles for Secondary Cooling in Continuous Casting ... · In Continuous Casting the...

Spray Nozzles for Secondary Cooling inContinuous Casting Machines

Lechler - Advanced Spray Technology Based on 125 Years Experience

Today’s steel producers haveto operate in a tougher en -viron ment than ever before,caused by:

� Customer demand forimproved quality

� Constant pressure on costs

� Fluctuating demand

� Tighter pollution controls

Pioneers in harnessingspray technology to steelproduction

Nozzles and spray systemsare used in virtually everystage of steel production andtheir performance can have amajor impact on product quali -ty and manufacturing costs.For over 125 years, Lechlerhas pioneered developmentsin spray technology for all stages of primary metals pro-duction, designing, develop ingand manufacturing productsof outstanding reliability andperformance. All accompa-nied by expert advice basedon a thorough knowledge ofthe industry, providing bothconventional and innovativesolutions.Today, Lechler offers the mostcomprehensive range of nozz-les and spray systems for iron,steel and non-ferrous metalsproducers. From secondarycooling for continuous casting

to shape control in cold rollingmills and descaling, Lechlerhas a proven solution.

Lechler - synonymous withquality

The Lechler policy of conti-nuous improvement and meti-culous inspection is evidenceof our commitment to wholelife quality. From development,through manufacture to instal-lation, Lechler products aresubject to continuous qualitymanagement. State of the arttest and inspection methods,often in excess of our ISO9001 certification, guaranteethe durability, reliability andlongevity of Lechler spraynozzles and systems.

Automated production forconsistent performance

Many of Lechler’s automatedmanufacturing processeshave been custom developedto guarantee not only opti-mum productivity, but alsoconsistency of product para-meters to exacting tolerances.Not only does every nozzlelook like another of its type,but their spray characteristicswill also be identical - guaran-

teed. This applies to every oneof the 20,000 plus nozzle vari-ants in our product portfolio,which differ by size, materialand spray characteristics.

Serving steel producersworldwide

Lechler is a truly internationalcompany, offering sales andtechnical support to the metalsindustry worldwide. In additionto over 500 employees at ourMetzingen headquarters inGermany, affiliated companieshave plant and offices in theUSA, the UK, India, China,France, Belgium, Sweden, Finland and Hungary. We alsohave a network of sales officesand representation coveringmany other countries.

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3

Spray Cooling Methods

In Continuous Casting thesecondary cooling system hasan important influence on thequality of the cast products.Two different spray coolingmethods are possible:1. Conventional cooling, viasingle fluid nozzles using onlywater.2. Airmist cooling via ‘twinfluid’ nozzles using compres-sed air and water.

Whilst single fluid nozzlesystems are less expensive toinstall and run, consumingless energy, twin fluid systemshave three significant advanta-ges in continuous casting,which outweigh initial and run-ning costs:

� Wider water control range,typically from a ratio of 1:5up to 1:25.

� Higher Heat Transfer Coeffi-cient values at identicalnozzle flow rates.

� Larger water and air bores,which virtually eliminatenozzle clogging.

For these reasons, airmistcooling is the favouredmethod for modern slabcasting.

Heat transfer considerations

Careful evaluation of dataobtained by measurementshas confirmed that heat trans-fer depends on two major fac-tors - the density of the spray-ed water and its kineticenergy.

The degree to which one orthe other factor dominatesdepends on the nozzle designand operating conditions. Thisis due to a condition calledthe Leidenfrost Phenomenon,in which a steam/vapour layerprevents the sprayed watermaking direct contact with thetarget surface.

However, when water dropletswith a high kinetic energybreak through this vapourlayer, the heat transfer coeffi-cient is significantly increased,with consequent higher cool -ing efficiency.The configuration of nozzles is

dependant on slab size andspray height - a single spraynozzle, a pair of nozzles or aseries of nozzles are installedbetween the support rollerscovering the full width of theslab. The arrangement is desi-gned to ensure a uniformliquid distribution across theslab width throughout all ope-rating conditions.

Foot roller installations

For installations in the narrowgap between the mould andfoot rollers, an array of singlefluid flat jet nozzles( Lechlerseries 660, 664 or 665) isoften used. These are speci-fied due to their narrow spraypattern, but oval cone nozzles(Lechler series 400) can alsobe used.

Bending and straighteninginstallations

For these applications, stan-dard single fluid flat jet nozzlesand 148 series Block nozzlesare generally installed with alarge overlap, due to theirparabolic liquid distribution.This aids uniform liquid distri-bution across the slab widththroughout the turndown ratiorange (minimum to maximumwater flow/pressure). It alsocontributes to safety as, if anozzle clogs, the two adjoiningnozzles will cool its targetarea, preventing that section ofthe slab surface from recei-ving no cooling at all.

In zones further down thestrand, a single flat jet nozzlecan be installed in each rollergap. To cover the slab width,it is recommended that wideangle flat jet nozzles with 120°up to 140° spray angles, oreven with rectangular spraypatterns, are specified. Choice can be made fromseries 100 Twinorifice Block,Mastercooler or Slabcoolernozzle types.

More common in moderncasting plants is a multi-nozzlearrangement of airmist nozzlesin every gap, providing veryuniform liquid distributionacross the full width of theslab from minimum to maxi-mum water flows. This arran-gement also facilitates edgecontrol by allowing the outernozzles to be switched on andoff.

Mastercooler and Slabcoolernozzles are designed to provi-de such extremely uniformspray patterns.

Efficient Secondary Cooling - a Prerequisite for OptimisingSteel Quality

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Choose the Right Nozzle for Your Application

Twin Fluid Nozzles

Single Fluid Nozzles

Product Slab Thin Slab Bloom Billet Beam-Blank Round

Spray pattern

.

5

Twin Fluid Nozzles

Example of nozzle type

Flat jet/parabolic

Full cone/circular

Flat jet/parabolic

Flat jet/even

100.XXX

138.XXX

148.XXX

124.XXX128.XXX

X

X

X

X

X

X

X

X X(Tip)

150°

30°60°90°

30°60°90°120°140°

90°130°or

to suit

min.

max.

min.

max.

min.

max.

min.

max.

1,5

1,8

0,45

0,95

0,5

0,95

0,7

16

28

60

14

25,2

19

70

3,8

41

5,5

13,5

2,0

4,2

1,6

8,5

1,7

29

23,5

40

10

18

18

50

3,2

37

16

42

6,5

13,6

4

28

5

65

13

20

4

7,2

16,5

28

1,4

26

3/8 NPT3/8 BSPP Console

Console

1/4 NPT 1/4 BSPP Console

Console

3/8 NPT3/8 BSPP Console

Console

3/8 NPT3/8 BSPPConsole

Console

Slab

Billet,Bloom

Billet,Bloom,Slab

Slab,Thinslab

1:101:20

1:15

1:35

1:7

Product no. VWater [l/min] and

VAir [Nm3/hr] at 2 bar air constant

Spray angle

Nozzle size from

– up to

Turn dow

n ratio

at 2 bar air (1 bar/7 bar water)

ApplicationsMaterial Connection

(acc. to size)Advantages/Features

Spray characteristics/

water distribution

� Finest dropletspectrum

� Wide turndown ratio offlow rate

� Large, freecross sections

� Strong flowimpuls

� Quick andeasy cleaning

� Patentedmixing insert

� Self aligningtip

� High HTCvalues

� Stable sprayangle at allpressures and flows

� Uniform waterdistribution

� Nozzle lenghtto suit

Water

Air

Water

Air

Water

Air

Brass

303 SS

Brass, nickel plated1 bar

Water2 barWater

7 barWater

Water Air

..

Subject to technical modifications.

Twin Fluid Nozzles

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Flat jet/even

Flat jet/even

184.XXX

186.XXX

X

X

X

X

X(Tip)

X(Tip)

min.

max.

min.

max.

2,25

8

2,25

8

9,8

60

9,8

60

3,6

18

3,6

18

9,5

55

9,5

55

8,6

50

8,6

50

6,8

23,5

6,8

23,5

3/8 BSPP 1/2 BSPP

Console

3/8 BSPP 1/2 BSPP

Console

Billet,Bloom,Slab,thinslab

Billet,Bloom,Slab,Thinslab

1:5(1:8*)

1:5(1:8*)

Product no. VWater [l/min] and

VAir [Nm3/hr] at 2 bar air constant

Spray angle

Turn dow

n ratio

at 2 bar air (1 bar/7 bar water)

ApplicationsMaterial Connection

(acc. to size)Advantages/Features


water distribution

� High HTCvalues

� Stable sprayangle at allpressuresand flows



Other features possible:– 2 piece pipe– Bent pipe– Oval spray

� High HTCvalues

� Stable sprayangle at allpressuresand flows



Other features possible:– 2 piece pipe– Bent pipe– Oval spray

Water

Air

Water

Air

Water

Air

Brass

303 SS

Brass, nickel plated1 bar

Water2 barWater

7 barWater

Water Air

80°90°100°120°130°or tosuit

80°90°100°120°130°or tosuit

Nozzle size from

– up to

..

* In case of variable air pressure Subject to technical modifications.


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Example ofnozzle type

Flat jet/parabolic

Flat jet/parabolic

Flat jet/rectangu-lar, even

Flat jet/rectangu-lar, even

660.XXX

652.XXX

664.XXX

656.XXX

X

X

X

X

X

X

–

–

–

–

–

–

60°90°120°

60°90°120°

60°90°120°

60°90°120°

min.

max.

min.

min.

max.

min.

max.

0,71

7,07

0,71

4,45

28,28

4,45

28,28

1,00

10,0

1,00

6,3

40,00

6,3

40,00

1,87

18,71

1,87

11,79

74,83

11,79

74,83

Dovetail Retaining nut3/8 BSPP

Retaining nut3/8 BSPP

DovetailRetaining nut3/4 BSPP

Retaining nut3/4 BSPP

Slab, Bloom:footroller area, first segments

Slab, Bloom:single nozzlearrangement

1:2,65

1:2,65

1:2,65

1:2,65

Product no. VWater [l/min] min/max

at p [bar]

Spray angle

Turn dow

n ratio

(1 bar/7 bar water) Material Connection

(acc. to size)Applications Advantages/

Features


water distribution

� Compact, definedspray pattern

� High energyspray jet

Brass

303 SS

1,0

2,0

7,0

Brass, nickel plated

.



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Full cone/circular,even


Full cone/square,even

Full cone/square,even

460.XXX

468.XXXSZU

468.XXXSZUQ

464.XXX

X

X

X

X

X

X

–

X

–

–

–

X

45°60°90°120°

45°60°90°120°

90°

60°75°85°115°

min.

max.

min.

max.

min.

max.

min.

max.

0,76

7,58

0,76

7,58

1,36

7,58

0,95

7,58

1,0

10,0

1,0

10,0

1,8

10,0

1,25

10,0

1,65

16,51

1,65

16,51

2,97

16,51

2,06

16,51

1/8 BSPT1/4 BSPT3/8 BSPT

Retaining nut3/8 BSPT

Retaining nut3/8 BSPT

1/4 BSPT3/8 BSPT1/8 NPT1/4 NPT

1:2,2 up to1:2,5

1:2,2 up to1:2,5

1:2,2

1:2,2


at p [bar]

Spray angle

Turn dow

n ratio

(1 bar/7 bar water) Material Connection


Features


water distribution

Brass

303 SS

1,0

2,0

7,0


.


� Stable spray angle




Billet, Bloom(Rounds):as well as Slabcaster fornarrow side orfootroller area

Billet, Bloom

(Rounds):as well as Slabcaster fornarrow side orfootroller area

Thin slab, Slab(footroller area)

Thin slab, Slab (footroller area)


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Full cone/oval,even


422.XXX

400.XXX

486.XXX

X

X

X

–

–

–

X

–

–

60°90°120°

90°

45°50°65°80°90°

min.

max.

min.

max.

min.

max.

0,71

11,31

3,37

5,1

1,5

9,85

1,0

16,0

4,45

6,85

2,1

14

1,87

29,9

7,34

11,31

3,95

26,1

1/4 BSPT3/8 BSPT

1/8 BSPT1/4 BSPT1/8 BSPT

1/4 BSPT inner3/8 BSPT inner

1:2,6

1:2,2

1:2,6


at p [bar]

Spray angle

Turn dow

n ratio

(1 bar/7 bar wate r) Material Connection


Features


water distribution

Brass

303 SS

1,0

2,0

7,0



.

Billet, Bloom(Rounds):

Thin slab, Slab(e.g. footrollerarea)

Billet castersfrom

CONCAST

� Large freecross sections,noncloggingsensitive

� Stable sprayangle

� Stable sprayangle

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Improved Performance Measurement Optimises Nozzle Design

The basis for optimising thedesign of nozzles is the abilityto accurately and preciselymeasure and analyse perfor-mance. Lechler has developedits own techniques to producereliable data on volume, dro-plet size, liquid distributionand heat transfer. Such data isthen applied in the develop-ment, design and manufactureof nozzles to optimise theirperformance.Every nozzle comes with com-plete documentation detailingits performance characteri-stics, typically including:

� Water/air flow diagram� Water flow diagram� Spray width diagram� Liquid distribution diagram� Heat Transfer Coefficient

diagram (on specialrequest)

LIQUID DISTRIBUTION SINGLE NOZZLE (Example)

Pro.-No.: 124.688.35.33.00.0 Date: 20.03.95 Liquid Pressure: 2,00 bar Liquid Flow rate: 4,60 l/min Air Pressure: 2,00 bar Air Flow Rate: 7,30 m3/h i.N. Remark:

Nozzle Height: 80 mm Spray Width: 368 m Mes. Point Dist.: 16 m

1

00,45 1,05 1,02 1,02 1,07 1,15 1,06 1,13 1,09 1,04 1,11 0,91

0,73 1,09 1,02 1,01 1,11 1,07 1,08 1,11 1,04 1,05 1,07 0,50

Comparative Value to Mean Value

Spray Width Diagram (Example)Pressure-Flowrate-Diagram (Example)

p= 1.00 barp=2.00 barp=4.00 barp= 7.00 bar

Liquid Distribution Single Nozzle (Example)

11

Heat Transfer Coefficient Measurement

When designing coolingsystems for ContinuousCasting plants, engineersneed to know the heat transfercoefficient to determine thespecific nozzle arrangement,taking into account the surfaceconditions of the metal to becooled.

The heat transfer can be affected by the LeidenfrostPhenomenon, which resultswhen, due to the high surfacetemperatures, the water eva-porates so intensely that a filmof steam completely coversthe surface, preventing thecoolant reaching the hot metal.

The measurement of the heattransfer coefficient (HTC) hasto cover the full range of surfa-ce temperatures that canoccur in spray cooling proces-ses in the metals industry.

Lechler measure the HTC bymeans of the ‘Moving NozzleTest’, in which a steel plate isheated to 1200°C in inert gasand then cooled down to thetemperature of the sprayedwater.

The HTC fluctuates as thenozzle moves over the thermo -couple, with maximum HTC,signified by the peak values,occurring when water directlyimpinges on its position.

The objective is to simulatespray cooling of a movingsteel strand. The spray is restricted by twocylindrical shapes represen-ting the rolls used in conti-nuous casting. Both the nozzleand ‘cylinders’ are installed ina moveable bed, enablingthem to be moved parallelwith, and longitudinally to, theplate.

When the desired temperaturehas been reached, the com-puterised control retracts thedeflector and starts the quen-ching by switching on thenozzle motor. This moves thenozzle from left to right withthe deflector open and rever-ses with the deflector closed.

The plate measures 600 x 320 mm with a thick-ness of 24 mm, and 24 ther-mocouples are uniformly po sitioned 3 mm below thequenched surface to measuretemperatures.By continuously recording thedata from these thermocou-ples a complete distribution ofheat transfer rates can becomputed. A typical result is shownbelow, where the surface tem-perature from one thermo -couple has been recorded.

Lechler GmbH Precision Nozzles · Nozzle SystemsP.O. Box 13 2372544 Metzingen / GermanyPhone: +49 (0) 71 23 962-0Fax: +49 (0) 71 23 962-333

E-Mail: [email protected]: www.lechler.de

Edition 04/04

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World Headquarters Lechler Companies Sales Offices

Belgium: Lechler S.A./N.V. · Avenue Mercatorlaan, 6 · 1300 Wavre · Phone: (10) 225022 · Fax: (10) 243901 · [email protected]: Lechler Intl. Trad. Co., Ltd. · Beijing Office · Rm.1305 CTS Plaza · No.2 Bei San Huan Dong Lu · Phone: (86) 1064661986, Fax: (86) 1064660196 · [email protected]: Lechler Oy · Kalliotie 2 · 04360 Tuusula · Phone: (358) 98709844 · Fax: (358) 98709847 · [email protected]: Lechler France, S.A. · Immeuble CAP2 C51 · 66-72, Rue Marceau · 93558 Montreuil · Phone: (1) 49882600 · Fax: (1) 49882609 · [email protected] Britain: Lechler Ltd. · 1 Fell Street, Newhall · Sheffield, S9 2TP · Phone: (0114) 2492020 · Fax: (0114) 2493600 · [email protected]: Lechler (India) Pvt. Ltd. · Plot # A-109 · Road # 18 · Wagle Industrial Estate · Thane-400 604 · Phone: (22) 25811196 · Fax: (22) 25821262 · [email protected]: Lechler AB · Box 158 · 68324 Hagfors · Phone: (46) 56325570 · Fax: (46) 56325571 · [email protected]: Lechler S.A. · Avda. Pirineos 7 · Oficina B7, Edificio Inbisa I · 28700 San Sebastián de los Reyes, Madrid · Phone: (34) 916586346 · Fax: (34) 916586347 · [email protected]: Lechler Inc. · 445 Kautz Road · St. Charles, IL. 60174 · Phone: (630) 377-6611 · Fax: (630) 377-6657 · [email protected]

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