优化铸造生铁工艺

1、ProcessoptimizationrequirementsforHighstrengthDuctileIroncastings1. Inputmaterials:Amongthevariousinputmaterialsinvolvedinductileironmanufacturethereareafewcriticalonewhichwillneedspecialattention.1.1. PigIron:Thequalityandquantityofpigironplaysanimportantroleinductileironproperties.Ideallyyoushould

2、useSorrelpigironorequivalent.ThispigironisCanadianandexpensive.Itisessentiallymeantforhighstrengthductileirons.Therearecloseequivalentsalsoavailablewhichcanbetriedlaterinmassproductionforcostreduction.Fortrialpurposesitwouldbebesttosecureareasonablequantityofsorrelifpossible.ItisalsoavailableinChina

3、.Incaseyoucannotgetsorrelpigironforyourtrials,IwouldsuggestthatyoutrytheChinesepigironQ10forlowsiliconpigorQ12forhighersiliconpig.OnetypicalspecificationsofSorrelforductileironisgivenbelow:Carbon:2.5-3.2%Silicon:Max0.5%Manganese:Max0.1%Phosphorus:Max0.03%Sulfur:Max0.03%(desirable0.01%)Chromium:mMax0

4、.07%Titanium:Max0.02%DesulphurizationshouldbedonewithCalciumCarbide.LowersulfurisveryimportantforductileironsincethenodularizingeffectofMagnesiumisreducedwhenexcessivesulfurispresenttoformMgSwhichgoesintoslag.PleasenotethatlowTiandSareessentialforductileiron.1.2. Nodulizer:TypicalSpecis:CHEMICALCOMP

5、OSITION(%):Mg:4.756.25Si:44.048.0Ce:0.95-1.20GENERALAPPEARANCE:GraySilverlusterSIZE:540mm:Max.8%ofsmallersizepermissibleItmayhelptoadd0,0035%TelluriumalongwiththenodularizerintheBigladle.1.3. Inoculant:Idealinoculantfortheductileironwouldbetheonecontainingasmall%ageofMg.TypicalonewhichwasusedinUSAwa

6、sAA50Dorequivalentoffollowingspec:CHEMICALCOMPOSITION(%):Si:46.00-50.00;Ca:0.60-0.90;Mg:1.00-1.50Al:0.50-1.25;Fe:BalanceGENERALAPPEARANCE:GraySilverlusterSIZE:27mm:Max.10%ofsmallersizepermissibleIfthisinoculantisnotavailableyoucanuseanygoodFeSiinoculantsuchasSuperseedwhosespecis:CHEMICALCOMPOSITION(

7、%):Si:73.00-78.00Ca:0.10max.Sr:0.60-1.10Al:0.50max.GENERALAPPEARANCE:SilverygraycrystallineSIZE:26mm(allfinessievedout)Pleasenotethatthesizeofinoculantisimportantforproperinoculatingactioninthegiventime.1.4. Tincanbeaddedinsmalldosagesof0.012-0.014%withinoculantforincreasingthetensilestrengthofducti

8、leiron.1.5. Alternatively,Bismuthupto0.007%canbeaddedalongwiththeinoculantintothetransferladle.1.6. Siliconcarbide:Labreagentqualityoftypicalspec:Si:55%C:38%.ItisusefultoaddSiCattwostagesinsmalldosesforrejuvenatingnucleationsites.Firstadditionof0.2%oftotalchargeweightismadeinthemeltingfurnacewhenthe

9、alloyingelementsareaddedintothecharge.Thesecondadditionof0.1%isaddedafterthemetalhasbeenhalfuseduporiftherehasbeenadelayofover20minutesinpouringouttheentiremelt.2. Processoptimization:Severaltrialswillneedtoberuninordertodeterminethemostoptimumchemistryandprocess.Inordertoachievehighertensilewithhig

10、herelongationtwooptionscanbetried:Option1:thisoptionwilladoptchemistryverysimilartowhatyouhavealreadytriedandfinetuneitforincreasingthetensileandtheelongation.Generallytheseductilematerialsneedheattreatmentforachievingthedesiredproperties.IamnotsureyouareOKwithheattreatedmaterialornotOption2:thisopt

11、ionwouldbeaferriticmicrostructurenodularironwhichwasusedseveraldecadesagoinUSAforsimilarapplicationsasyours.Thiswillusehighercarbonandsiliconanddoesnotrequireanyheattreatmentaftercasting.Inboththeseoptionsthemainvariableswillbethechemicalcomposition.Therestoftheprocessofchargemake-up,melting,nodular

12、izingandinoculatingtreatments,temperatures,etc.willbeidenticalandhencethesewillbedetailedinthelastsectionofthisplan.Option1:LowCEductileironwithpearlitic-ferrriticmicrostructure:Si:2.10Mn:0.15Cu:0.50Targetchemistry:C(total):3.50P:0.10max.S:0.03max.Cr:0.10Mo:0.20Otherelementsmaybepresentasimpurities.

13、Inthisprogramthevariantstobetriedafterthefirstbasetrialwillbe- varyingtheCandSiforahigherorlowerCEdependingontheresultfromthebasetrial.IftensileisstilllowdecreasetheCEinstepsof0.05andvice-versa.- increasingCuto0.8%- addingNifrom0.7to2.0%instages- addingtinwithinoculantinquantityof0.012%.Heattreatmen

14、twillnormallyberequiredforthismaterial.Option2:FerriticNodularIron:OnesuggestedchemistryandpropertiesofanodularferriticductileironwhichwaspopularinUSAisasfollows:CHEMICALCOMPOSITION(%):C(total):3.00-4.00Si:4.00-5.50Mn:0.10-0.30P:0.10max.S:0.03max.Mg:0.01-0.06Otherelementsmaybepresentasimpurities.MIC

15、ROSTRUCTURE:Graphite:Predominantlyspheroidalwithothertypesofgraphitenottoexceed20%ofanyfield.Matrix:Predominantlyferritic,withwelldispersedpearlite.Pearlitenottoexceed40%ofthetotalmatrix.Carbidesshallbesmall,welldispersed,andnottoexceed5%ofanyfield.PHYSICALANDMECHANICALPROPERTIES:Hardness90-108HRBTe

16、nsileStrength:515MPamin.(75,000psimin.)YieldStrength:345MPamin.(50,000psimin.)ModulusofElasticity160,000MPatypical(23x106Psitypical)Elongation7-15%in50.8mm(2")Forthecrosssectionsyouareworkingwith,IwouldsuggestthatyoutryCarbonat3.2%andSiliconat4.2%.Dependinguponthepropertiesachievedwiththisyouca

17、ntrytomodifytheCE.3. FoundryProcesscommontobothoptionsabove:3.1. Chargemakeup:Scrapandreturningmaterials:60-65%Scrapsteel:10%max(Avoidasfaraspossible)PigIron:25-30%(highqualitypigsuitableforductileiron.ShouldhaveminimumS,TiandAl)SiC:(Si:55%,C:38%):0.2%(calculatedintothecharge)Otheralloyingelements:C

18、alculatedformeantargetpercentageFerrosilicon&Ferromanganese:CalculatetherequiredweightaccordingtothecontentsintherawmaterialandadditionsintheChargemake-up.Inoculants:BigladlewithMgcontentifpossible-0.3%.Smallpouringladlenormalsuperseedorequivalent-0.2%.(Sncanalsobeaddedasanoption)NOTE1:Amountofm

19、oltenmetalinthebigladleandinthepouringladlemustbeaccuratelyweighedwithaloadcellwithanaccuracyof10kgsothattheinoculantaddedisaccurateforthatweight.NOTE2:Allinputmaterialshouldbeaccuratelyweighedwithsuitableweighingbalancesandshouldalsobetotallydryandmoisture-free.3.2. MeltingandPouring:Thebestfurnace

20、forthismeltingisamediumfrequencyinductionfurnacewithfrequencyaround400Hz.Sequenceofinputmaterialchargingandoperatinginstruction:Chargingthefurnace:Firstchargeintothefurnace50%ofthecalculatedPigIronand50%Returns,andheatitupto1100C.NextaddcalculatedquantityofFeCr,FeMn,Cu,Mo,SiC,etcandthentopupwiththeb

21、alance50%PigIronand50%returns.Heatthemeltupto1380°C-14000Candholdatthistemperaturetilltheanalysisofthemoltenironchemistryisconfirmed.CarboncontentshouldbecheckedonLECOtypeofequipment.TheanalysesofSi,Mn,P,S,Cr,Cuetcarebasedonaspectrometerreading.Oncethechemistryisconfirmedsuperheatthemeltupto156

22、0C-1580CandpreparefortappingthemetalintotheBullLadle(Bigladleinwhichnodularizationtreatmentistobedone.Ifmoltenironisnotqualified,donotsuperheatbutreadjustchemistryat1380C-1400Candrecheck,tillitisqualified.Nodularization:Tapoutthemetalatsuperheattemperatureintoapreheated(minimum750C)TundishorBullLadl

23、e(BigLadle)intowhichthecalculatedquantityofNodularizerFeSiMg5andTellurium(ifdesired)hasbeenplacedatthebottomcoveredwithnodularironsmallscrappieces.Theweightofmetalpouredshouldbeaccuratelyreadoutontheloadcell.Inoculation:PourtheMgtreatedmetalintothetransferorpouringladlewhichwaspreheatedtomorethan750

24、Candisattachedtoaloadcellforaccurateweighmentofthemetalpouredintoit.Whenmoltenironvolumereachesabout1/3thisladle'scapacity,add0.4%inoculantsand0.007%Bismuthor0.012%Tin(ifdesired).Thegrainsizeofinoculantshouldbe4-8mmandtheweightoftheinoculantandotheradditionsifanyshouldbemeasuredaccuratelybyadigi

25、talscaleofappropriatecapacityandaccuracy.Totalmetalpouredinladleshouldbeaccuratewithin10kgasieenonladleweighingscaleSlagging-offmustbeimplementedbeforepouring,addprotectiveagenttoremovetheimpuritiesonmoltenironsurface.Pouringtemperature:Thetemperatureofpouringintothemoldsshouldbe1430C-14600C.Checkandrecordeveryladlet