research article development of intermediate cooling...

Research ArticleDevelopment of Intermediate Cooling Technology andIts Control for Two-Stand Plate Rolling

Fei Zhang12 Wei Yu3 and Tao Liu3

1National Engineering Research Center for Advanced Rolling Technology University of Science and Technology BeijingBeijing 100083 China2School of Electrical Computer amp Telecommunications Engineering University of Wollongong Wollongong NSW 2522 Australia3Engineering Research Institute University of Science and Technology Beijing Beijing 100083 China

Correspondence should be addressed to Fei Zhang zhfeicngmailcom

Received 4 May 2016 Revised 21 October 2016 Accepted 10 November 2016

Academic Editor M Junaid Khan

Copyright copy 2016 Fei Zhang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In a plate rolling production line thermomechanically controlled processing is critical for plate quality In this paper a set ofintermediate cooling equipment of a two-stand platemill with super density nozzles medium pressure and small flow is developedBased on a simplified dynamic model a cooling control scheme with combined feedforward feedback and adaptive algorithms isput forwardThe new controlled rolling process and the highly efficient control system improve the controlled rolling efficiency byan average of 1766 The proposed intermediate cooling system can also effectively inhibit the growth of austenite grain improvethe impact toughness and yield strength of Q345B steel plate reduce the formation of secondary oxide scale on the plate surfaceand the chromatic aberration of the plate surface and greatly improve the surface quality of the steel plate

1 Introduction

Thermomechanical control processing (TMCP) is a micro-structural control technique combining controlled rollingand controlled cooling The mechanical properties intro-duced to the steel through TMCP route are virtually equiv-alent to those obtained by heat treating conventionally rolledor forged steel It can be optimized by control of phasetransformation of austenite with cooling technology duringor after hot rolling process [1 2] By appropriate choice ofdeformation temperature and strain rate the strength of steelcan be increased The strength of TMCP steel is higher thanof normalized steel of the same composition [3 4] ThusTMCP steel has a leaner composition (lower alloy content)than conventional normalized steel of the same strength

Controlled rolling and controlled cooling technology iswidely used inmedium and heavy plate production and playsan important role in the performance of the products on theside But during controlled rolling process the rolling in thetemperature range of partial recrystallization region betweenthe recrystallization and nonrecrystallization zone must bestopped for temperature holding to avoid the appearance

of mixed grain structure which will affect the quality ofthe products Generally the temperature holding process iscompleted by air cooling of swinging intermediate slab onroller table [5] The cooling process of slab in the air is arelatively slow process of temperature drop which affectsthe production efficiency The production capacity of platemill using controlled rolling generally decreases by 26ndash30Therefore improving the cooling efficiency and reducingthe holding time are an important means to improve theproduction efficiency and comprehensive properties of theplate [6 7] One of the effective ways is the water coolingin rolling process namely the intermediate cooling (IC)process

IC technology is to install cooling equipment betweenthe roughing mill (RM) and the finishing mill (FM) of atwo-stand plate production line to reduce holding time andincrease production capacity Research shows that the watercooling of intermediate slab in temperature holding processcan reduce holding time and improve the rolling efficiencyunder the premise that nomechanical properties of the prod-uctswould be reduced [8ndash11] But before finishing rolling therereddening process of intermediate slab should be finished

Hindawi Publishing CorporationJournal of Control Science and EngineeringVolume 2016 Article ID 4192186 9 pageshttpdxdoiorg10115520164192186

2 Journal of Control Science and Engineering

Roughing millPyrometer Pyrometer

Water cooling section

Air cooling section

PyrometerFinishing mill

Figure 1 Schematic layout of the production line

after water cooling to reduce the temperature gradient alongthickness direction and avoid affecting the rolling process[12] Experiments have proved that the temperature drop ofintermediate slab by water cooling during controlled rollingcan reduce 15ndash20 of the holding time and improve therolling efficiency to a certain degree [13] Combined with theactual situation of a plate mill with a roll width of 3000mmwe designed the water cooling equipment before the finishingmill for rapidly reducing temperature of intermediate slab tocontrol finishing rolling temperature as shown in Figure 1

2 Overview of Intermediate Cooling

21 Rolling Force Model The IC section is located betweenthe RM and the FM and the main components include sixgroups of 650mm spacing coolers Basic parameters of theIC technology and equipment are as follows

The thickness and width range of intermediate slab are40ndash110mm and 1600ndash2850mm respectively the startingtemperature the ending temperature and the rereddeningtemperature of intermediate slabs are separately 1050ndash1030∘Cbelow 950∘C and 880ndash950∘C the roller spacing of roller tableis 650mm the length of cooling zone is 39m the length ofthe longest intermediate slabs is 12m the pressure of coolingwater is 04MPa the distance between the centerline of RMand the centerline of finishing mill is 78m and the distancebetween the centerline of RM and the centerline of the firstgroup of coolers is 26345m the cooling mode is multipur-pose interrupt cooling (MULPIC) of one pass or swing thecooling water is turbid circulating water Cooling productmainly includes high-strength low-alloy intermediate slabssuch as shipbuilding plate and structural plate

22 Equipment IC equipment comprises filtration systemwater supply pipe flow regulation device spraying and cool-ing device measuring instruments and automatic controlsystem The working IC equipment is shown in Figure 2

Mechanical system is the main equipment of acceleratedcooling after rolling system and is the basis of acceleratedcooling The mechanical system primarily consists of thefollowing subsystems water supply and water recycling sys-tem water distribution system high-density laminar systemedge masking system side spray system and front and rearblowing system The main part of the water supply systemis the pumping system whose task is to provide cooling

Figure 2 Working intermediate cooling equipment

water to meet the requirements of the temperature and flowfor the cooling system when the plate is cooled and whichconsists of a number of variable frequency drive pumpsand high pressure pumps for water supply Cooling watercirculation system mainly consists of outside plant coolingtowers cooling ponds and other components

Medium pressure water passes through the water tankin the workshop after being filtered and then is assigned toevery cooler Water out of the coolers directly passes throughthe trench of the IC section and then returns to the watertreatment system Water distribution system consists of themedium level water tank and the water distributor in theworkshop The medium level water tank has steady flowwater buffer and exhaust function The main function ofthe water distributor is to evenly distribute the water in themedium level water tank to each cooler so as to realize theuniform cooling of the steel plate The side masking systemcan automatically adjust the horizontal water spraying of thecooling manifold according to the different widths of thesteel plate to improve the control precision of the horizontaltemperature of the steel plate

The side masking system can improve the cooling effi-ciency and capacity of cooling water and improve the coolinguniformity of steel plate The blowing system can guaranteeplate surface cleaning when the plate enters and leaves thecooling zone improve the surface quality of steel plate andimprove the detection accuracy of the plate temperature

23 Technological Process Themost basic type of IC includesrecrystallization type controlled rolling unrecrystallizationtype control rolling and (120572 + 120573) two-phase region typecontrolled rolling In the actual production process engineersgenerally take the combination of the above two or three basic

Journal of Control Science and Engineering 3

types of controlled rolling based on the rolling equipmentcapacity the product performance requirements and thecost-benefit analysis Adopting TMCP mode from the hightemperature recrystallization type controlled rolling to unre-crystallization type controlled rolling or (120572 + 120573) two-phaseregion type controlled rolling on the one hand can avoidrolling in the austenite recrystallization zone and prevent themixed crystal austenite and on the other hand can changethe traditional air-cooled temperature holding and reduceholding time and in addition can relieve the productioncapacity pressure caused by the short distance of roller tablebetween the RM and the FM

The technological process is briefly described as follows

Step 1 The intermediate slab enters the controlled coolingzone after roughing rolling

Step 2 Determine the cooling scheme according to themeasured temperature and the calculated thickness of theintermediate slab

Step 3 When the intermediate slab enters the cooling zonethe front blowing system is turned on to prevent the coolingwater from returning along the slab surface and affecting thenormal work of measurement instruments and sensors whenintermediate slab is being cooled in the controlled coolingzone

Step 4 The corresponding cooling manifolds are openedaccording to the cooling scheme

Step 5 After the intermediate slab has left the cooling zonethe rear blowing system promptly blows away the residualwater on the slab surface to prevent the warping headphenomenon of the slab caused by uneven cooling of theupper and lower surface of the slab during finishing rollingprocess

Step 6 After the intermediate slab has left the coolingzone the rereddening is implemented to achieve uniformtemperature of the intermediate slab so as to prevent thenonuniform microstructure defects

3 Temperature Model and Control Scheme

31 Rolling Force Model The moving steel plate can beconsidered as a mass flow that is conveyed along the coolingroller table from the entry (roughing rolling) to the exit(finishing rolling) Over this period of time the steel plateexchanges energy with the environment by convection andradiation

The entry and exit locations of a slab are defined asthe geometrical boundary of the dynamic model of thecooling process Pyrometers are installed at the entry and exitlocations to provide temperature measurements The wholecooling section is divided into 119876 subcooling zones and eachintermediate slab is divided into 119899 segments Each segment ofthe plate is tracked by the controller in real time

The surface temperature profile 119879 of a plate in the coolingsection can be described as a function of run-out time z [14]

119879 = 119880119908 + (119879119890 minus 119880119908) sdot 119890minus119875119911 (1)

where 119880119908 and 119879119890 represent environment temperature andentry temperature respectively And 119875 is a model coefficientwhich is determined by the plate thickness entry speed heattransfer and conduction of the plate The value of 119875 can becalculated as [14]

119875 = 1198871(1 (1198861 + 1198862) 119865 + ℎ11989611198872) 1198872ℎ1198962 (2)

where 1198871 is the thermal conduction coefficient and 1198872 isthe heat conduction coefficient They are determined byempirical curves The empirical parameters 1198961 and 1198962 areconstant and ℎ is the thickness of the plateTheheat exchangecoefficients 1198861 and 1198862 are for the upper and lower surface ofthe slab respectively These two factors are estimated withadaptive genetic algorithm 119865 is a coefficient depending onwater tank pressure water temperature and plate speed Itsvalue is determined using experimental data for specific plantand operation conditions

32 Feedforward Control Algorithm There are typically 12electric flow control valves and 12 pneumatic valves in thecooling section located in a number of cooling zones Thecooling zones and the valves in each zone are coded in asystematic sequence in preparation for control

Feedforward control is activated as soon as a plate entersthe cooling section The plate is divided into segmentsaccording to sampling time As the sampling time is fixed thelength of each segment may vary with the plate speed Basedon model (1) the exit temperature of each segment can bepredicted by the following formula in discrete form

119879 (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908) sdot exp (minus119875119898119899119911119898119899) 119875119898119899119911119898119899 = 119876sum

119894=119898

119875 (119894 119899) 119911 (119894 119899) (3)

where119876 is the total number of cooling zones For the 119899th slabsegment entering themth subcooling zone the environmenttemperature 119880119908 and the entry temperature 119879119890(119898 119899) areavailable from the sensors The value of 119875 is calculated using(2)

For a given reference exit temperature 119879119903 the objectiveof the feedforward control is to minimize the difference 119889between the predicted exit temperature 119879ℎ(119876 119899) and 119879119903

119889 = 1003816100381610038161003816119879ℎ (119876 119899) minus 1198791199031003816100381610038161003816 (4)


If 119879119878 is set to an expected exit temperature function and119879119878(119876 119899) is equal to 119879119903 the control change can be determinedby the following conversion

119879ℎ (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908)sdot exp[minus 119876sum

119894=119898

119875 (119894 119899) 119911 (119894 119899)] 119879119878 (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908)

sdot exp[minus 119876sum119894=119898

119875 (119894 119899) 119911119878 (119894 119899)]

(5)

where 119911119878 is the run-out time that is determined such that119879119878(119876 119899) is equal to 119879119903 From (5)

119879ℎ minus 119880119908119879119890 minus 119880119908 = exp[minus 119876sum119894=119898

119875 (119894 119899) 119911 (119894 119899)] (6)

119879119878 minus 119880119908119879119890 minus 119880119908 = exp[minus 119876sum119894=119898

119875 (119894 119899) 119911119878 (119894 119899)] (7)

Combining (6) with (7) yields

ln119879ℎ minus 119880119908119879119878 minus 119880119908 = 10038161003816100381610038161003816119875119898119899119911119898119899 minus 11987511989811989911991111987811989811989910038161003816100381610038161003816 (8)

The change of run-out time is calculated as follows

Δ119911 = 10038161003816100381610038161003816119911119898119899 minus 11991111987811989811989910038161003816100381610038161003816 = ln ((119879ℎ minus 119880119908) (119879119878 minus 119880119908))119875119898119899 (9)

It is assumed that the slab speed V is constant withina cooling zone and the change in the activated coolinglength of the cooling zone corresponding to the segment isdetermined as

Δ119871 = V sdot Δ119911 = V sdot ln ((119879ℎ minus 119880119908) (119879119878 minus 119880119908))119875119898119899 (10)

The change in cooling length is implemented by adjustingthe number and the flow of open cooling valves as thedistance between valves is fixed

33 Feedback Control Algorithm As soon as the first segmententers the finishing rolling zone its temperature is measuredto start the feedback control The measured temperaturevalues replace the corresponding predicted values in thefeedforward control

For a measured cooling temperature function 119879119908 thechange of the cooling length Δ119871119891 can be obtained as follows

Δ119871119891 (119898 119899) = V sdot ln ((119879119908 minus 119880119908) (119879119878 minus 119880119908))119875119898119899 (11)

34 Adaptive Control Algorithm In order to further improvethe control accuracy with the measured cooling temperature

Tr Controller

minus

minusminus

+

+

+

U Plant

K Adaptive controller

Prediction model

Tf

ΔT

Tp

Figure 3 Block diagram of adaptive control scheme

a correction factor119870 is introduced to fine-tune the value of 119875in model (3) as follows

119879119908 (119898 119899) = 119879119906 + (119879119890 (119898 119899) minus 119879119906)sdot exp[minus 119876sum

119894=119898

119870 (119894 119899) 119875 (119894 119899) 119911 (119894 119899)] (12)

119870(119898 119899) is determined using the exit temperature mea-surements according to the following adaptive rule

119870 (119898 119899) = 119870 (119898 119899 minus 119897) + 119870119891 [119870119906 minus 119870 (119898 119899 minus 119897)] (13)

where 119870119891 is a filter coefficient and 119870119906 is determined by

119870 (119898 119899 minus 119897) = 1119875 (119898 119899 minus 119897) 119911 (119898 119899 minus 119897)sdot ln 119879119908 (119898 119899 minus 119897) minus 119880119908 (119898 119899 minus 119897)119879119878 (119898 119899 minus 119897) minus 119880119908 (119898 119899 minus 119897)

(14)

The initial value of119870(119898 119899) for the first plate segment hasto be assigned by experience using previous data

The control scheme is illustrated in Figure 3 where 119879119903 isthe reference temperature119879119891 is the feedback temperature119879119901is the predicted temperature and 119880 is the control value

4 Intermediate Cooling Control System

41 System Structure The control system structure isdesigned as three levels Level 0 is the field device levelwhich mainly includes sensors valves and A-C and D-Cdigital drives Level 1 (L1) is the basic automation levelwhich consists of programmable logic controllers (PLCs)and microcomputers that manage the functional logic of thesystem the single device control and the interface with thesensors Level 2 (L2) also known as the process automationlevel consists of minicomputers that handle technologicalprocess and production targets and provide the user withtools for plant supervision and diagnostics The appliedautomation control system designed for the intermediatecontrol is shown in Figure 4

42 Process Automation Level (L2) Process automation levelmainly referring to the process computers and correspondingapplication programs is responsible for setting calculation of


IC HMI RM HMI

IC PLC

Remote IO station

Drives

Meters

Actuators

Drives

Meters

Actuators

Ethernet

Profibus-DP

Remote IO station

PLC before ICroll table

FM HMI

PLC after ICroll table

MM


process model sending set value (opening mode steel plateby the speed of cooling zone and the regulating value ofthe valve) to L1 and realizing the human-machine interface(HMI) between L1 and L2 The communication between L2computers or with other devices is via Ethernet

L2 workflow is described as follows in the roll bite oflast roughing pass HMI computer delivers PDI parameterslike size grade and finishing temperature to L2 computerwhich calculates the preset values and sends the results tothe PLC when the head of intermediate slab reaches theentrance pyrometer L2 computer calculates dynamic settingbased on starting temperature and then sends the regulatedsignal to the PLC when intermediate slab passes throughthe exit pyrometer L2 computer records the cooling flowslab speed opening mode ending temperature rereddeningtemperature and so forth for model self-learning of the nextintermediate slab of the same specification

43 Process Automation Level (L2) L1 uses Siemens PLCS7-300 as the master control station and Siemens ET200 asremote IO station L1 functions are as follows

(1) The Head and Tail Tracking Control PLC calculatesthe position of intermediate slab according to signalof the HMDs and other sensors

(2) Speed Control of Roller Table and Swing Control ofIntermediate Slab Based on L2 Setup

(3) Flow Control of the Cooler The function moduleregulates the opening position of the correspondingelectric control valve to control the water flow of thecooler and open or close each group of manifoldsaccording to the model setup and tracking results

(4) Signal Measurement and Collection PLC collects thesignal from the sensors for validity check and processcontrol

(5) Communication with the Process Control ComputersPLC receives commands from L2 and transmits thecollected signals to L2

44 Human-Machine Interface (HMI) HMI system is animportant component of the IC control system as well asthe window of human-machine interaction The function ofthe control system is divided into manual semiautomaticand automatic modes which are selected by the operatorThe operator sends command to the control system via HMIand at the same time monitors the running state of thesystem HMI system mainly completes the task of processmonitoring display report output online parameter settings(the speed parameters the edge masking length of the slabhead and tail the number of the nozzle groups the flow ofthe spay nozzles etc) model correction fault alarm trendrecording pump station remote monitoring and so on Thehome screen is shown in Figure 5

5 Application Effect

51 Production Efficiency Improvement According to theholding time of AC the delivery time the rolling timeand the number of intermediate slabs it can be calcu-lated that under the premise of guaranteeing temperatureuniformity IC can reduce cooling time and improve pro-duction efficiency By comparing the temperature fields ofintermediate slabs of 40ndash110mm under different processconditions the changes of the theoretical value of productionefficiency improvement under the condition of single-slabcontrolled rolling and multislab alternately controlled rollingare obtainedThe production efficiencies of the single-slab ICand the multislab alternate IC are improved by 23ndash87 and491ndash145 respectively where the single-slab IC means to


Figure 5 Home screen of HMI

cool plates one by one and the multislab alternate IC refersto the simultaneous cooling of a plurality of slabs

The improvement value Δ120578SS of the production efficiencyof the single-slab IC is derived from

Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)

where 119905119878 is the saved time 119905AC is the air cooling time 119905WC isthe water cooling time 119905IC is the intermediate cooling timeand 119905RT is the rereddening time after IC

The improvement valueΔ120578MS of the production efficiencyof the multislab alternate IC is derived from

Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905AC = 119905TAC119899 + 119905IN lowast (119899 minus 1) 119905WC = 119905TWC119899 + 119905IN lowast (119899 minus 1) + 119905TN

(16)

where 119905119878 is the saved time of each plate 119905AC is the air coolingtime of each plate 119905WC is the water cooling time of each plate119905TWC is the total water cooling time 119905IN is the slab intervaltime 119905TN is the transport time and 119899 is the number of slabs

In actual production because of the operation reasonor the logical limit of the control system the productionefficiency improved by IC is certainly not as high as thetheoretical value Comparedwith the conventional controlledrolling process the IC process has higher production effi-ciency Figure 6 shows that the production efficiencies ofsingle-slab IC and multislab alternate IC are improved by upto 7913 and 2265 respectively for rolling thickness from63mm to 25mm and by 3036 and 1267 respectively

Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100

40 50 60 70 80 90 100 110 12030Intermediate bloom thickness (mm)

Single-bloom theoretical valueMultibloom theoretical value

Multibloom actual valueSingle-bloom actual value

Figure 6 Comparison of the actual value and the theoretical valueon production efficiency improvement of intermediate cooling

for rolling thickness from 76mm to 46mm As can be seenIC effectively improved the production efficiency of controlrolling

52 Mechanical Property Improvement In order to inves-tigate the differences of production mechanical propertiesbetween IC and conventional AC we tested the effects oftwo different processes on the mechanical properties of theQ345B steel platewith the same specificationThemechanicalproperties of the steel plate are shown in Table 1 The resultsshow that IC can effectively improve impact energy and yieldstrength but cannot significantly change the elongation Thisis because IC inhibits the recrystallization grain growth andrefines the austenite grains

The microstructure at room temperature of Q345 steelproduced by high efficiency controlled rolling process isshown in Figure 7 The surface microstructures of both sidesand the center are fine ferrite and pearlite And the ferritegrain size number at 14 thickness position of steel plate is104ndash106 The core microstructure is even smaller and isaccompanied by a small amount of banded structure ForQ345 steel which is produced by the conventional TMCPprocess the ferrite grain size number at 14 thickness positionis only 86ndash91

53 Alloy Reduction Effect Niobium (Nb) is an importantmicroalloying element added in high-strength ship plate andit can effectively improve the strength and toughness of thefinished plate But Nb is expensive and high Nb content inthe alloy leads to high cost By using intermediate coolingmaterial composition optimization and process parametersoptimization Nb content gradually reduces from an averageof 200 ppm to about 120 ppm under the premise of ensuringthe qualified and stable performance of high-strength shipplateThus the goal of reducing cost and improving efficiencyis achieved The yield strength distribution of the steel platebefore and after optimization is shown in Figure 8 from


Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m

(a) Surface after AC

100 120583m

(b) Core after AC

100 120583m

(c) Surface after IC

100 120583m

(d) Core after IC

Figure 7 Microstructure of Q345 steel after AC and IC

400 420 440 460 480380Yield strength (MPa)

0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy

380 400 420 440 460 480 500Yield strength (MPa)

05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy

Figure 8 Statistical histogram of yield strength of steel plate before and after optimization

which it can be found that the peak interval is slightlyincreased and the fluctuation range is basically unchanged

54 Alloy Reduction Effect As shown in Figure 9 IC andAC are compared in terms of surface quality It can be seenthat intermediate cooling which reduces the formation ofsecondary oxide scale on the plate surface and the chro-matic aberration of the plate surface greatly improves thesurface quality of the steel plate Because of lowering thesurface temperature of the intermediate slab intermediatecooling reduces the formation of Fe2O3-based secondaryiron oxide scale promotes the formation of FeO and Fe3O4

and converts FeO into uniform and dense oxide scale withstrong adhesion composed of Fe3O4 + Fe at low temperatureTherefore this kind of steel plate not only has smooth surfacebut also has good resistance to atmospheric corrosion inthe process of transportation and storage which has beenvalidated by experiments [15]

6 Conclusion

Based on the analysis on IC process and equipment a coolingcontrol scheme with combined feedforward feedback andadaptive algorithms is proposed The IC control system


(a) Intermediate cooling (b) Air cooling

Figure 9 Comparison of surface qualities of steel plates under different cooling conditions

realizing uniform cooling effectively shortens the coolingtime and improves the average controlled rolling efficiencyby 1766

The intermediate cooling can effectively inhibit thegrowth of austenite grain and improve the impact tough-ness and yield strength of Q345B steel plate By using thismechanism the alloy-reduced production of high-strengthshipbuilding steel containing Nb and Q345B steel containingAls is carried out

The formation of secondary oxide scale on the platesurface and the chromatic aberration of the plate surface arereduced and the surface quality of the steel plate is greatlyimproved

Competing Interests

The authors declare that there are no competing interestsregarding the publication of this paper

Acknowledgments

This work is partially supported by the National NaturalScience Foundation of China (51404021) Beijing MunicipalNatural Science Foundation (3154035) and the FundamentalResearch Funds for the Central Universities (FRF-TP-15-061A3)

References

[1] N Shikanai S Mitao and S Endo ldquoRecent developmentin microstructural control technologies through the thermo-mechanical control process (TMCP) with JFE Steelrsquos high-performance platesrdquo JFE Technical Report 11 2008

[2] E P Silva P M C L Pacheco andM A Savi ldquoOn the thermo-mechanical coupling in austenite-martensite phase transforma-tion related to the quenching processrdquo International Journal ofSolids and Structures vol 41 no 3-4 pp 1139ndash1155 2004

[3] A Kojima M Fujioka M Hoshino G Shigensato M Kanekoand M Tanaka ldquoProgress of high performance steel platesrdquoNippon Steel amp Sumitomo Metal Technical Report no 110 pp3ndash7 2015

[4] K Nishioka ldquoMarket requirements of thermomechanicallyprocessed steel for the 21st centuryrdquo Steel World vol 5 no 1pp 61ndash67 2000

[5] W Huo Study onModel to Control Intermediate Cooling Processfor Plate Rolling Northeast University ShenYang China 2009

[6] Y Tian S Tang BWang ZWang andGWang ldquoDevelopmentand industrial application of ultra-fast cooling technologyrdquoScience China Technological Sciences vol 55 no 6 pp 1566ndash1571 2012

[7] R Song D Ponge and D Raabe ldquoInfluence of Mn contenton the microstructure and mechanical properties of ultrafinegrained C-Mn steelsrdquo ISIJ International vol 45 no 11 pp 1721ndash1726 2005

[8] S W Thompson D J Vin Col and G Krauss ldquoContinuouscooling transformations and microstructures in a low-carbonhigh-strength low-alloy plate steelrdquo Metallurgical TransactionsA vol 21 no 6 pp 1493ndash1507 1990

[9] B K Panigrahi ldquoProcessing of low carbon steel plate and hotstripmdashan overviewrdquo Bulletin of Materials Science vol 24 no 4pp 361ndash371 2001

[10] B Hutchinson ldquoMicrostructure development during cooling ofhot rolled steelsrdquo Ironmaking amp Steelmaking Processes Productsand Applications vol 28 no 2 pp 145ndash151 2001

[11] A Bakkaloglu ldquoEffect of processing parameters on themicrostructure and properties of an Nb microalloyed steelrdquoMaterials Letters vol 56 no 3 pp 263ndash272 2002

[12] L-Y Jiang C-J Zhao J-H Shi G Yuan X-Q Wang and Q-X Huang ldquoHot rolled strip re-reddening temperature changinglaw during ultra-fast coolingrdquo Journal of Iron and Steel ResearchInternational vol 22 no 8 pp 694ndash702 2015

[13] P J Heedman S P Rutqvist and J A Sjostrom ldquoControlledrolling of plates with forced-water cooling during rollingrdquoMetals Technology vol 8 no 9 pp 352ndash360 1981

[14] G van Ditzhuijzen ldquoThe controlled cooling of hot rolled stripa combination of physical modeling control problems andpractical adaptionrdquo IEEE Transactions on Automatic Controlvol 38 no 7 pp 1060ndash1065 1993

[15] X-J Wang X-G Li T-S Yang S-B Guo J-Y Li and C-FDong ldquoAnalysis of pitting corrosion of hot-rolled X70 micro-alloyed steel plates in storage conditionrdquo Journal of Iron andSteel Research vol 22 no 6 pp 26ndash44 2010

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Roughing millPyrometer Pyrometer

Water cooling section

Air cooling section

PyrometerFinishing mill

Figure 1 Schematic layout of the production line

after water cooling to reduce the temperature gradient alongthickness direction and avoid affecting the rolling process[12] Experiments have proved that the temperature drop ofintermediate slab by water cooling during controlled rollingcan reduce 15ndash20 of the holding time and improve therolling efficiency to a certain degree [13] Combined with theactual situation of a plate mill with a roll width of 3000mmwe designed the water cooling equipment before the finishingmill for rapidly reducing temperature of intermediate slab tocontrol finishing rolling temperature as shown in Figure 1

2 Overview of Intermediate Cooling

21 Rolling Force Model The IC section is located betweenthe RM and the FM and the main components include sixgroups of 650mm spacing coolers Basic parameters of theIC technology and equipment are as follows

The thickness and width range of intermediate slab are40ndash110mm and 1600ndash2850mm respectively the startingtemperature the ending temperature and the rereddeningtemperature of intermediate slabs are separately 1050ndash1030∘Cbelow 950∘C and 880ndash950∘C the roller spacing of roller tableis 650mm the length of cooling zone is 39m the length ofthe longest intermediate slabs is 12m the pressure of coolingwater is 04MPa the distance between the centerline of RMand the centerline of finishing mill is 78m and the distancebetween the centerline of RM and the centerline of the firstgroup of coolers is 26345m the cooling mode is multipur-pose interrupt cooling (MULPIC) of one pass or swing thecooling water is turbid circulating water Cooling productmainly includes high-strength low-alloy intermediate slabssuch as shipbuilding plate and structural plate

22 Equipment IC equipment comprises filtration systemwater supply pipe flow regulation device spraying and cool-ing device measuring instruments and automatic controlsystem The working IC equipment is shown in Figure 2

Mechanical system is the main equipment of acceleratedcooling after rolling system and is the basis of acceleratedcooling The mechanical system primarily consists of thefollowing subsystems water supply and water recycling sys-tem water distribution system high-density laminar systemedge masking system side spray system and front and rearblowing system The main part of the water supply systemis the pumping system whose task is to provide cooling

Figure 2 Working intermediate cooling equipment

water to meet the requirements of the temperature and flowfor the cooling system when the plate is cooled and whichconsists of a number of variable frequency drive pumpsand high pressure pumps for water supply Cooling watercirculation system mainly consists of outside plant coolingtowers cooling ponds and other components

Medium pressure water passes through the water tankin the workshop after being filtered and then is assigned toevery cooler Water out of the coolers directly passes throughthe trench of the IC section and then returns to the watertreatment system Water distribution system consists of themedium level water tank and the water distributor in theworkshop The medium level water tank has steady flowwater buffer and exhaust function The main function ofthe water distributor is to evenly distribute the water in themedium level water tank to each cooler so as to realize theuniform cooling of the steel plate The side masking systemcan automatically adjust the horizontal water spraying of thecooling manifold according to the different widths of thesteel plate to improve the control precision of the horizontaltemperature of the steel plate

The side masking system can improve the cooling effi-ciency and capacity of cooling water and improve the coolinguniformity of steel plate The blowing system can guaranteeplate surface cleaning when the plate enters and leaves thecooling zone improve the surface quality of steel plate andimprove the detection accuracy of the plate temperature

23 Technological Process Themost basic type of IC includesrecrystallization type controlled rolling unrecrystallizationtype control rolling and (120572 + 120573) two-phase region typecontrolled rolling In the actual production process engineersgenerally take the combination of the above two or three basic














119879 = 119880119908 + (119879119890 minus 119880119908) sdot 119890minus119875119911 (1)


119875 = 1198871(1 (1198861 + 1198862) 119865 + ℎ11989611198872) 1198872ℎ1198962 (2)





119894=119898

119875 (119894 119899) 119911 (119894 119899) (3)



119889 = 1003816100381610038161003816119879ℎ (119876 119899) minus 1198791199031003816100381610038161003816 (4)




119894=119898

119875 (119894 119899) 119911 (119894 119899)] 119879119878 (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908)


119875 (119894 119899) 119911119878 (119894 119899)]

(5)



119875 (119894 119899) 119911 (119894 119899)] (6)


119875 (119894 119899) 119911119878 (119894 119899)] (7)












Tr Controller

minus

minusminus

+

+

+

U Plant


Prediction model

Tf

ΔT

Tp




119894=119898

119870 (119894 119899) 119875 (119894 119899) 119911 (119894 119899)] (12)





(14)







IC HMI RM HMI

IC PLC

Remote IO station

Drives

Meters

Actuators

Drives

Meters

Actuators

Ethernet

Profibus-DP

Remote IO station


FM HMI


MM

















Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)



Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC


(16)



Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation






















119879 = 119880119908 + (119879119890 minus 119880119908) sdot 119890minus119875119911 (1)


119875 = 1198871(1 (1198861 + 1198862) 119865 + ℎ11989611198872) 1198872ℎ1198962 (2)





119894=119898

119875 (119894 119899) 119911 (119894 119899) (3)



119889 = 1003816100381610038161003816119879ℎ (119876 119899) minus 1198791199031003816100381610038161003816 (4)




119894=119898

119875 (119894 119899) 119911 (119894 119899)] 119879119878 (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908)


119875 (119894 119899) 119911119878 (119894 119899)]

(5)



119875 (119894 119899) 119911 (119894 119899)] (6)


119875 (119894 119899) 119911119878 (119894 119899)] (7)












Tr Controller

minus

minusminus

+

+

+

U Plant


Prediction model

Tf

ΔT

Tp




119894=119898

119870 (119894 119899) 119875 (119894 119899) 119911 (119894 119899)] (12)





(14)







IC HMI RM HMI

IC PLC

Remote IO station

Drives

Meters

Actuators

Drives

Meters

Actuators

Ethernet

Profibus-DP

Remote IO station


FM HMI


MM

















Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)



Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC


(16)



Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












119894=119898

119875 (119894 119899) 119911 (119894 119899)] 119879119878 (119898 119899) = 119880119908 + (119879119890 (119898 119899) minus 119880119908)


119875 (119894 119899) 119911119878 (119894 119899)]

(5)



119875 (119894 119899) 119911 (119894 119899)] (6)


119875 (119894 119899) 119911119878 (119894 119899)] (7)












Tr Controller

minus

minusminus

+

+

+

U Plant


Prediction model

Tf

ΔT

Tp




119894=119898

119870 (119894 119899) 119875 (119894 119899) 119911 (119894 119899)] (12)





(14)







IC HMI RM HMI

IC PLC

Remote IO station

Drives

Meters

Actuators

Drives

Meters

Actuators

Ethernet

Profibus-DP

Remote IO station


FM HMI


MM

















Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)



Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC


(16)



Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










IC HMI RM HMI

IC PLC

Remote IO station

Drives

Meters

Actuators

Drives

Meters

Actuators

Ethernet

Profibus-DP

Remote IO station


FM HMI


MM

















Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)



Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC


(16)



Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













Δ120578SS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC

119905WC = 119905IC + 119905RT(15)



Δ120578MS = 119905119878119905AC 119905119878 = 119905AC minus 119905WC


(16)



Prod

uctio

n effi

cien

cy im

prov

emen

t (

)

0102030405060708090

100










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table1Optim

ized

inpu

t-to-hidd

enlayerw

eights

Num

ber

Rolling

code

Grade

Thickn

ess(mm)

Yieldstr

ength(M

Pa)

Tensile

strength(M

Pa)

Elon

gatio

n(

)Coldbend

ing

Impactenergy

(J)

Coo

lingmod

e1

0926086

Q345B

16375

555

28Intact

147128113

IC2

0922087

Q345B

16385

540

29Intact

1511

6414

6IC

30922088

Q345B

16390

545

30Intact

159134173

IC4

0922089

Q345B

16345

535

29Intact

1027272

AC5

0922090

Q345B

16350

525

32Intact

1199292

AC


100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










100 120583m


100 120583m

(b) Core after AC

100 120583m


100 120583m

(d) Core after IC



0

10

20

30

40

50

60

Rolli

ng n

umbe

r

(a) High Nb alloy


05

10152025303540

Rolli

ng n

umbe

r

(b) Low Nb alloy





6 Conclusion








Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation















Competing Interests


Acknowledgments


References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









research article development of intermediate cooling...

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