DOC

Research,Development,and

By Zachary Lawson,2014-07-24 02:03
6 views 0
Research,Development,andand, and,And

    Research,Development,and

;(1.CentralIronandSteelResearchInstitute,Beijing100081,China;2.CapitalIronand

    ;SteelGroupCompany,Beijing100041,China) ;Abstract:Theresearch,production,andapplicationofVNmicroalloyedhighstrengthrebarsinChinawerere

    ;viewed.Enhancednitrogeninvanadium-containingrebarspromotestheprecipitationoffi

    neV(C,N)particles,and

    ;markedlyimprovestheprecipitationstrengtheningeffectivenessofvanadium.

    ;Therefore,vanadiumaddedtoVNmi

    ;croalloyedrebarscanbereducedby40%ocomparedtothesamestrengthlevelofvanadium-

    containingrebars.

    ;Keywords:highstrengthreinforcedbar;VNmicroalloying;precipitationstrengthening

    ;Reinforcingbars,38thebiggeststeelproducts ;inChina,accountforaboutonefourthofthetotal

    ;steelproduction.Inrecentyears.theproduction ;andconsumptionofhotrolledrebarsinChinahas

    ;increaseddramatically,withfastdevelopmentofthe ;nationalbuildingindustry.AsshowninFig.1.the ;totalannualrebarproductionin2004approaches71rail

    ;liontons,nearlyfivetimesasmuch38thatin1995. ;However,therebarproductmixhasnoobvious ;change3syet,andisstilldominatedbygrade2re

    ;barsinChinabuildingmarket.Atpresent,near ;8Ooftherebarproductionisgrade2rebars.with ;minimumyieldstrengthof335MPa,intheChinese ;market.However,inthedevelopedcountries.the ;rebarsforbuildinghavebeenupgradedtograde3re

    ;bars,withanyieldstrengthof400MPaorabove. ;Forexample,grade4rebarswithyieldstrengthof ;500MPahavebeenwidelyusedinGermany[.A

    ;largenumberofapplicationexperiencesindicatethat ;rebarconsumptioncanbesavedbv14ifthe

    ;strengthoftherebarsareupgradedfromgrade2to ;grade3.Therefore,therewillbe3greatsocialand ;economicbenefitsifsubstitutionofgrade3reb3rs ;forgrade2rebarsispromotedinChina.

    ;Inthepresentstudy,theresearch,production, ;andapplicationofhigh——strengthrebarstotheVN

    ;microalloyedprocessinChinawerereviewed. ;Fig.1ProductionofrebarsinChinainpastdecade ;1ExperimentalResearchofVNMicroalloyed

    ;HighStrengthRebars

    ;Themicroalloyingprocessismainlyadopted ;todevelophighstrengthweldablerebars,allover ;theworld[.Duringrebarproduction.3high ;rollingspeedandhighfinishrollingtemperatureare ;quitesuitablefortheapplicationofthevanadiummi

    ;croalloyingtechniqueinrebaralloydesign[.The ;latestrebarstandardissuedinChinaalsorecom

    ;mendstheuseofvanadiummicroalloyingtoproduce ;grade3rebarswiththeminimumyieldstrengthof ;400MPaL.However,vanadiumadditionwill ;markedlyraisetheproductioncostofrebars.Itis ;knownthatthemicroalloyingelementtakeseffectby ;Biography:YANGCaifu(1965

    ),Male,Doctor,Profess0r;E-mailyangcaifu@cisri.com.c”;RevisedDate:Ap

    28,2006

    ;,f-I00_J0.I0-IJ

    ;

    ;?

    ;82?JournalofIronandSteelResearch,Internationa1V01.15 ;precipitationofitscarbonides/nitrides.andmicroal

    ;loyednitrideshavenoticeablybetterstrengthening ;effectivenessthancarbonides,asthenitrideparticles ;arefinerandmorestable.Anumberofresearchre

    ;suitsindicatethatnitrogenisacosteffectiveal-

    ;loyingelementinvanadiummicroalloyedsteels,and ;thestrengtheningeffectivenessofnitrogeninvana

    ;diumbearingsteelcanreachastrengthincrementup ;toabout6MPaper0.0010ofnitrogen.TheSUC

    ;cessfulapplicationofVNmicroalloyedtechnology

    ;tohighstrengthrebarshelpstodevelopacost-ef-

    ;fectivemethodforgrade3rebarproductioninChi

    ;na[691

    ;.

    ;1.1Effectofnitrogen

    ;Fig.2showstheeffectofnitrogenonthe ;strengthofvanadiumbearingrebarstee1.Withthe

    ;samevanadiumcontent,thestrengthofVNsteelis

    ;muchhigherthanthatofvanadiumstee1.Itcanbe ;seenthatwiththeenhancementof0.0100inni

    ;trogen,theyieldstrengthandtensilestrengthofV

;Nsteelincreaseby117.5MPaand135MPa.re

    ;spectively,comparedtovanadiumstee1.Theresults ;showthatnitrogenmarkedlyimprovesthestrength

    ;eningeffectivenessofvanadiuminsteel.which ;meansthatnitrogenisaveryeffectivestrengthening ;elementforvanadiumbearingrebars.

    ;1.2Vanadiumdistributionandprecipitationinrebars ;Vanadiumdistributioninvanadiumcontaining

    ;steelandVNsteelisshowninFig.3.Invanadium- ;containingsteel,vanadiummainlyexistsassolidso

    ;lutionaccountingfor56.3ofthetotalvanadium ;content,whereas,only35.5ofvanadiumprecipi- ;tatesintheformofV(C.N).Theresultsreveal ;thatmostofthemicroalloyingelementinvanadium- ;containingsteeldoesnotworktowardprecipitation ;00

    ;垂芎5o0

    ;

    ;?

    ;400

    ;0.11V0.0085%N

    ;steel

    ;0.12%V0.018%N

    ;steel

    ;Fig.2Thestrengthofvanadium-containingsteeland,Nsteel ;100

    ;Vv(c,N)

    ;VMaC

    ;Vsoluble

    ;V-containingsteelV-Nsteel

    ;Fig.3Vanadiumdistributioninvanadium-containing ;steelandV-Nsteel

    ;strengtheninganditisawasteofvanadiulT1.Onthecon- ;trary,inV-Nsteel,70ofvanadiumforrnsV(C,N)pre

    ;cipitatesandonly20dissolvesinthematrix. ;Hence,nitrogenadditionaltersvanadiumdistribu

    ;tioninsteel.andpromotestheprecipitationofvana

    ;diumdissolvedinthematrix.thusimprovingthe ;precipitationstrengtheningofvanadium. ;Table1liststheresultsofV(C,N)precipitate ;volumesinvanadiumcontainingsteelandVNstee1.

    ;ItcanbeseenthattheamountofV(C,N)precipi

    ;tareinVNsteelisovertwiceasmuchasthatnva

    ;nadiumcontainingstee1.Itisclearthattheenhanced

    ;nitrogeninVNsteelpromotesvanadiumprecipitation ;markedlyanditshouldbeoneofthemainreasonsfor ;thestrengthimprovementinVNstee1.

    ;Fig.4showsthesizedistributionofV(C,N) ;precipitates.Thefractionoffineparticleswithasize ;oflessthan10nminvanadiumcontainingsteels

    ;iust21.1,whereas,thefractionisupto32.2in ;VNstee1.Astheresultshows.nitrogenadditionin ;steelnotonlypromotesprecipitationofV(C,N), ;butreducestheaveragesizeofV(C,N)particles, ;andgreatlyincreasesthefractionoffineparticlepre

    ;cipitates,whichalsomakesagreatcontributionto

    ;wardincreasingthestrengthinVNstee1.

    ;Table1MasspercentofV(C.N)precipitatesin ;vanadium-containingsteeland,Nsteel

    ;???0

    ;八王r号高rB0写唇nq葛卫口

    ;

    ;Issue2Research,Development,andProductionofVNMicroalloyedHighStrengthRebars?83?

    ;Particlesize/nm

    ;Fig.4ParticlesizedistributionofV(C,N)precipitatesin ;vanadium-containingsteel(a)andV-Nsteel(b) ;1.3StrengtheningmechanismofV.Nrebars ;Onthebasisofnumerousresearchresults,the ;strengthofmicroalloyedsteelsRcanbeexpressed ;by[:

    ;R85.74-37wM4-83ws4-17.4×D.+RPR(1)

    ;whereWM,sarethecontentofmanganeseandsil

    ;icon,respectively;thesecondandthethirdterms ;denotemanganeseandsiliconsolidstrengthening, ;respectively;theforthtermdenotesgrainrefine

    ;mentstrengthening;andRPRdenotesprecipitation ;strengthening.

    ;Accordingtotheexperimentalresultsofferrite ;grainsizeandyieldstrengthfortestedsteels,the ;contributionofeachstrengtheningmechanismtothe ;yieldstrengthofvanadiumrcontainingsteelandVrN

    ;steelisshowninFig.5.Itcanbeseenthatthe ;strengthdifferencebetweenvanadium-containingsteel ;2OMlnsjv--containingV--Nrebar

    ;rebar

    ;Fig.5Strengtheningmechanismof20MnSi,vanadium- ;containingrebar,andV-Nrebarsteel

    ;andVNsteelmainlyresultsfromdifferentcontri ;butionsofprecipitationstrengtheningandgrainre ;finementstrengthening.Thecontributionofprecipi ;tationstrengtheningandgrainrefinementstrengthe ;ningontheyieldstrengthforV_Nsteelisover70%. ;2ProductionandPropertiesofV__NMicroal_. ;loyedRebars

    ;2.1Optimizationofchemicalco~itionforV-Nrebars ;Onthebasisofresearchstudiesinthelaborato

    ;ry,thestrengtheningcapabilityofvanadiumandV

    ;Nmicroalloyinginhighstrengthrebars,produced ;bytheconverterandcontinuouscastingprocess, ;havebeencompared,usingmillscaletrials.The ;railltrialresultsareshowninFig.6.Itcanbeseen ;thattheV-Nrebarscontainingvanadiumof0.03

    ;0.09andvanadiumcontainingrebarswithvanadi

    ;umof0.060.14reachalmostthesame

    ;strengthleve1.Themilltrialresultsalsoindicate ;thatthestrengtheningcapabilityofvanadiuminVN

    ;steelismuchstrongerthanthatinvanadiumcontai

    ;ningstee1.Thus,foragivenstrengthrequirement, ;thevanadiumcontentinVNmicroalloyedsteelcan

    ;bemarkedlysavedwhencomparedwithvanadium

    ;containingstee1.

    ;Theregressionresultsonthestrengthdataof ;themilltrialrebarsindicatethattheyieldstrengths ;ofvanadiumcontainingsteelandVNsteelcanbe

    ;expressedasperthefollowingformulae: ;Vanadiumcontainingsteel

    ;RR(20Ms.)4-1056×v(2)

    ;VNsteel

    ;R一尺(20Msi)4-1994×7.ov(3)

    ;where7.ovisthemasspercentofvanadium. ;Itcanbeseenclearlyfromtheregressionre

    ;suitsthatthestrengtheningeffectofvanadiuminthe ;VNrebarsisalmostdoublewhencomparedwith ;thatofthevanadiumcontainingrebars.

    ;VanaeliUlTIeonten%

    ;Fig.6Effectofvanadiumonthestrengthforthe ;milltrialscalerebars

    ;u

    ;Bd?

    ;Bd??pl,d

    ;

    ;JournalofIronandSteelResearch.InternationalVoI.15 ;Theoptimizedcompositionsofgrade3rebarswith ;vanadium.containingandV_-Nmicroalloyedprocess ;aregiveninTable2.ThevanadiumcontentinVN

    ;microalloyedgrade3rebarswithminimumyield ;strengthof400MPacanbereducedto0.02

    ;0.04,andisonlyhalflevelinV-Femicroalloyed ;grade3rebars.

    ;2.2ProcesscOnsideratiOn

    ;Iti8easytocontroltheproductionprocessfor ;V-Nmicroalloyedgrade3rebars.Asamatteroffact, ;therei8essentiallynodifferenceintheproduction ;processofVNmicroalloyedgrade3rebarscom-

    ;paredtothatof20MnSgrade2rebars.Forachie- ;vlngthemaximumpreclpltatlOnstrengthenlng ;effect.iti8necessarytomakesurethattherei8full ;dissolutionofvanadiumcarbonitridesduringsoa

    ;king.ItisnotdifficulttodissolveV(C,N)precipi

    ;tatesfullyinvanadiumcontainingsteelbecauseof

    ;itshighsolubility,hence,thebillet8reheatingtem

    ;peratureisnottoohigh,andnormallyitisreheated ;to11501200?.Theacceleratingcoolingprocess ;isgenerallyusedafterfinishrolling,forrefiningthe ;finalferritegrainsize.

    ;Steadyrecoveryofvanadiumandnitrogenis ;vcryimportanttocontrolthefluctuationofthere

    ;bar8properties.Thestatisticalresultsfromanumber ;ofindustrialproductiondatashowsthatthescatterof ;thevanadiumcontenti8verynarrow(4-0.002)inV- ;Ngrade3rebarsmicroalloyedbytheNitrovanalloy,an ;additiveofvanadiumandnitrogen.Incontrast,thescat

    ;terinthevanadium-containingrebarsteeladdingfer

    ;rovanadiumreachesthelevelof-+-0.01andi8almost ;5timeshigherthanthatinV-Nrebars.

    ;NitrogencontentinVNsteelsdependsonthe

    ;vanadiumaddition.Therailltrialresultsshowthat ;foroptimizedindustrialoperations,wheneach ;0.01ofvanadiumi8added,0.O010ofnitrogen ;isaddedforNitrovan12andabout0.0013ofni- ;trogeni8addedforNitrovan16.

    ;2.3PropertiesofVNrebars

    ;2.3.jTensileproperties

    ;ThemechanicalpropertiesofVNmicroalloyed

    ;grade3rebarsaregiveninTable3andTable4,and

;theeffectoftherebarsizeonthemeehanicalproper

    ;tiesi8showninFig.7.Itcanbeclearlyseenthatthe

    ;mechanicalpropertiesofVNmicroalloyedrebars ;arequitestable.Theyieldstrengthfluctuatesbe

    ;tween425MPaand500MPawithafluctuation ;scopeof75MPa,althoughthetensilestrengthfluc

    ;tuatesbetween575MPaand660MPa,withafluc

    ;tuationscopeof85MPa,andelongationi8between

    class ;19and32.Allkindsofrebarsmeetone

    ;antiquakerequirements,wherethetensile/yield

    ;strengthratioi8higherthan1.25. ;Table2Thechemicalcompositionofgrade3rebarsinmasspercent

    ;N0te:1)ThenumberafterRes.isenhancednitrogenfromv_Nalloyadditive.

    ;Table3MechanicalpropertiesofV?Nmicroalloyedhot-rolledrebars

    ;460

    ;450

    ;430

    ;465

    ;445

    ;450

    ;425

    ;455

    ;440

    ;445

    ;490

    ;500

    ;485

    ;490

    ;485

    ;500

    ;475

    ;480

    ;500

    ;465

    ;478

    ;482

    ;463

    ;478

    ;468

    ;474

    ;447

    ;467

    ;458

    ;455

    ;600 ;59O ;585 ;605 ;590 ;590 ;575 ;605 ;595 ;59O ;640 ;640 ;62O ;640 ;645 ;660 ;640 ;625 ;610 ;625 ;631 ;625 ;616 ;622 ;62l ;623 ;608 ;6l4 ;602 ;608 ;29 ;26 ;26 ;22 ;24 ;l9 ;22 ;2O ;22 ;l8 ;32 ;33 ;29 ;29

;27

    ;3l

    ;29

    ;23

    ;24

    ;25

    ;3O

    ;28

    ;27

    ;26

    ;25

    ;26

    ;25

    ;22

    ;23

    ;22

    ;1.32 ;1.30 ;1.33 ;1.3O ;1.33 ;1.3l ;1.36 ;l_3l ;1.31 ;1.34 ;M加毖? ;

    ;Issue2Research,Development,andProductionofVNMicroalloyedHighStrengthReb

    ars?85?

    ;700 ;600 ;500 ;r./3 ;400 ;35

    ;

    ;25 ;0

    ;

    ;15

    ;Table4MechanicalpropertiesofV.Nmieroalloyedcoilingrebars

    ;10203040

    ;Diameterofrebars/mm

    ;Fig.7Effectofrebarsizeonthestrengthand ;theelongationofV.Nrebars

    ;2.3.2Strainaging

    ;Thestrain-agingindex.thatis,theincreasein ;flowstressafteraginginaprestrainedsample,was

    Nrebars.By ;usedtoevaluatethestrainagingofV

    ;therequirementofthenationalstandardonthe ;strainagingtest,theprestrainwasselectedas5, ;andtheagingas250?for1h.

    ;Table5showstheresultsofthestrainagingevalu- ;ationofVNrebarsand20MnSirebars.Theresults ;showthatnostrainagingphenomenonoccursinVN

    ;rebars,butasignificantstrainagingresponsecanbe ;seennthe20MnSgrade2rebars.

    ;2.3.3Weldability

    ;Fourtypicalweldingmethodsforrebarjoints,in_ ;cludingflashbuttwelding(FBW),gas-pressurewelding ;(GPW).shieldmetalarcwelding(SMA),anddec

    ;troslagpressurewelding(ESPW),havebeenusedto ;evaluatetheweldabilityofVNmicroalloyedrebars.

     ;ThetestingresultsinTable6showthatVNmicro

    ;alloyedhot——rolledribbedrebarshaveexcellentweld——

    ;abilityandaresuitableforthedifferentwelding ;processesmentionedearlier.

    ;2.3.4Low-cyclefatigue

    ;Fig.8showsthecurveofthefatiguelifeofVN

    ;and20SiMnrebars.Theexperimentalresultsindi

    ;catethatthefatiguepropertyofVNrebarsisalittle

    ;betterthanthatof20SiMnrebars.

    ;Table5Eff~tofagingonthepropertiesofV.Nrebars ;Table6Themechanicalpropertiesofweldingjoints ;Note:discurvatureforcoldbending;andaisdiameterofsample.

    ;

    ;Journa1ofIronandStee1Research.1ntemationa1Vo1.15 ;

    ;

    ;

    ;300

    ;250

    ;200

    ;150

    ;100

    ;4567

    ;Strain/%

Report this document

For any questions or suggestions please email
cust-service@docsford.com