抛丸清理机对板材轧辊进行抛丸处理外文文献翻译中英文翻译外文翻译Word格式文档下载.docx
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抛丸清理机对板材轧辊进行抛丸处理外文文献翻译中英文翻译外文翻译Word格式文档下载.docx
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V.I.Meleshko,A.P.Kachailov,V.G.Boikov,
V.L.Mazur,T.P,KobkaandI.I.Krivolapov
Atthepresenttime~muchattentionisbeingdevotedtoincreasingthequalityofrolledproducts,partieularlysheet.Toasignificantdegreethisdependsuponthepreparationoftherollsurface.Manyplantsareengagedinimprovingthequalityofworkingtherollsurfaceinpreparingthemforrolling.ThisarticlewaswrittenbypersonnelfromZaporozhstalPlant,MagnetogorskMetallurgicalCombine,theInstituteforFerrousMetallurgy,Dnepropetrovsk,andMagnetogorskMiningandMetallurgicalInstituteonthisveryrealproblem..
Thesurfacemicrorelief,orroughness,ofcoldrolledconstructionalsheethasaninfluenceonthemechanicalandproductionpropertiesofmetal,andalsoonthefinishqualityofpartsmadefromthissheet.Thefinalsurfacemicroreliefofthinsheetsteelisformedinaskinpassonworkroilswhichhavebeengivenaroughfinishwithmetalshot.
Normallytheroughsurfacefinishontheworkrollsofskinpassstandsisproducedinpneumaticandrotorshotblastingmachines.Experienceintheirusehasshownthatthepneumaticmachinesusedinthecountry'
ssteelplantsdonotfilltheneedforhighqualityblastingofrollsurfaces.
In1969theInstituteforFerrousMetallurgy,Dnepropetrovsk,didworkontheSM-2shotblastingmachineinNo.1ColdRoilingMillofZaprozhstalPlant,whichrevealedanumberofshortcomingsinitsconstruction.
ToprovidesheetwiththesurfaceroughnessrequiredbythespecificationsofVolgaAutomobilePlant(Ra=0.8-1.6g),thebasicrequirementsforthedesignofshotblastingmachinesweredetermined,Themachinemustprovide:
1.aconstantshotsizeduringoperation,inotherwords,effectiveremovalofshotofthespecifiedsizefrom
wornshot;
2.thepossibilityofcontrollingairpressureinthecollectoroftheshotblastmachineduringstableoperations;
3.thehandlingofworkrollsofdifferentdiameters(400-500mm)withoutspecialequipmentonthemachine;
;
4.simplicityincontrolandconvenienceinmaintenance.
Fig.1
TheSM-2machine(Fig.1)consistsofastationaryclosedchamber!
withatrolleyonwheelsaadmovab!
enozzles2~whichundertheactionofcompressedairdischargeshotontotherollsurface,awormconveyor8,anelevatorwithaseparator4,theshotblastequipment5,andanexhaustsystem6.Theequipmentismountedonaspecialfoundation1905mmbelowthefloorlevelThelengthofthemachinewiththetrolleyoutis15fl00ram,theheight4070ram,andthewidth4600mr~Thedimensionsoftherollshandledare400-500mmindiameterand2000-4000mminlength.Thetotalweightoftheequipmentis15tons.
Asresearchhasshown,thedynamicsofthewearofaworkingmixtureofabrasiveandtheoriginalconditionoftheshotchangesduringoperation.Duringblasting,theshottakesonawidersizerangeandisworndown,formingmanyfineparticles.Theconditionsunderwhichthepartsareblasteddependuponthesizeoftheshotused.Thecontaminationofthespecifiedsizebyfineparticlesdisruptstheprocess,producingapoorqualitysurfaceontherollsandconsequentlyonthesheet.Toeliminatetheseproblemsitisnecessarytoeitherregularlymeasurethecompositionoftheshotandmakeappropriatechangesintheblastingsequence,whichisdifficulttodoinpractice,ortoscreentheshotduringoperationofthemachinetoprovidethespecifiedparticlesize.
Stabilityintheblastingprocessisalsodeterminedbythequantityofshotdeliveredtothenozzles.Itwasexperimentallyestablishedthatsupplying0.3-0.4kg/secofshottothetwonozzlesinoperatingwithanairpressureof2.5-4.0atmprovidedstableoperation.Equippingthemachinewithscreeningdevicesisaneffectivemethodformaintainingaconstantshotsizemix.ThisisconfirmedbothbydataintheliteratureandbyexperienceintheoperationofSM-1andTsKb_P-1shotblastmachinesatZaporozhstalPlant.
Theshotisdeliveredtothesurfaceoftherollbytheshotblastequipment,thechamberofwhichisdividedbytwodiaphragmswithchargingventsintothreecompartmentsandisequippedwithanelectropneumaticcontroldevice.Theworkingmixturefromtheuppercompartmentofthechamberdropstothelowerandthentothecollector.Duringoperationofthemachine,theventsareclosed(turnedon).Theshotispouredineitherafterturningoffthevalvesbytheelectropneumaticcontroldevice,oraftershuttingdownthemachinebytheoperator.Whenitisturnedoff,theventdescends,andbetweenitandthediaphragmacirculargap5mmwideisformed.Theventisaconewithaslopeofabout30%Theshotdropsslowlythroughthisgapbutnotcompletely,andthereforeitincreasestot0ram.Theloadingventsarealternatelyturnedonbythecontroldevice.ThefirsttimetheSM-2machinewasrepaired,itwasdiscoveredthatthecontroldevicefrequentlydidnotoperatebecauseofcorrosionoftheparts.Withnormalchargingofabrasive(375kgaccordingtothenameplate),blastingmustbestoppedaftereachalternatepassofthenozzles,sinceafteranotherpasstheshotinthelowercompartmentisinsufficient,andduringblasting,Withnonoperationofthecontroldevice,itdoesnotdropfromtheuppercompartmenttothelower.Deliveryofthenextportionofshotmustbedoneonlyaftertheoperatordisconnectstheshotblastequipmentfromtheairsystem.Inthiscasebothchargingventsareopened,andtheabrasiveisfedtothelowercompartment.Continuousoperationofthemachineforthreeorfourpassesofthenozzleswithnonoperationofthecontroldeviceandthedeliveryofshotdescribedabovebecamepossibleafterincreasingthestandardchargeto650kg.However,thebasicsolutionofthisproblemisstableoperationofthecontroldevice.
Theusedshotiscollectedbythecollectingbunkeroftheworkingchamberanddropsintothereceivingchuteofthewormconveyor.Theplatesparalleltothewormconveyorareatagreaterangle,andthoseperpendicularareatlessofanangle,whichtendstocollectshotonthem.Therefore,afterblastingonerollitisnecessarytoshutthemachinedowntopushtheaccumulatedshotontothescrewconveyor.Toeliminatethisshortcoming,itispossibletolengthenthescrewconveyor,whichishalfthelengthoftheworkingchamber.Inaddition,thesmallerplateisremovedcompletely,andtheparallelplatesareelongatedtocorrespondwiththelengthofthewormconveyor.
Thecompressedairsuppliedtothecollectoroftheshotblastequipmentisdriedbyanoilmoistureseparator.However,thismethodofdryingisinadequate.Watervaporcondensesinthemainlineandintheshotblastequipment,andasaresultshotstickstogetherinthelowercompartmentandformsasolidmass.Thesolidmassclogstheverticalchannelsalongwhichtheabrasiveistransportedtothecollectoranddisruptstheoptimumratioofshottoairintheblast.Thishasadetrimentaleffectontheblastingprocessandthequalityoftherollsurface.Thepresenceofmoistureintheaircausescorrosionoftheequipmentandcausesoperationofthepneumaticequipmentofthemachinetobepoorer.Therefore,indesigningshotblastequipment,itisnecessarytospecifyequipmentfordryingtheair.Foreignfirms,forexample,usespecialdryingequipmentutilizingwaterabsorbingsubstancessuchassilicagelandactivatedaluminafordryingcompressedair.
Themechanismformovingthenozzlehasanumberofshortcomings.Applicationofthejetofabrasivematerialontotherollisthroughanozzlemountedinanelbowshapedgun(Fig.2).Ashortcomingofthegunisthethrottlingofthemixtureofcompressedairandshotwheretheverticalandhorizontalchannelsjoin.Thejunctionisarightangle,whichcausesquickwearingawayoftheelbow.Thecrosssectionsofthechannelsandnozzlewasincreased.However,withanincreaseinthenozzlediameterfrom10to12mm(theallowablemaximum)theconsumption
ofairincreasedfrom13to19mS/h,whichchangedtheratioofshottoairintheblast.However,thisratiomustbekeptconstant.Sinceduringblastingitisdifficulttomakecorrections,itwasnecessary~oimprovethedesignandincreasethewearresistanceoftheparts.
Fig.2
Forthispurposeanewdesignofblastguns,inwhichthediameterofthechannelswasincreased(Fig.2b)andtheshapeofthetransitionfromthechanneltothechannelandnozzlewaschanged,wasproposedandtested,Thenewnozzledesignismuchmoreeffective.Afterfivemonthsofoperation,noticeablesignsofwearintheelbowandnozzlehavenotbeenfound,whiletheolddesignelbowsworeoutinamonth.
Theblastgunsaremovedalongtherollbyaconveyorbelt.UndertheactionoftheweightofthetroJ.leyandoscillationscausedbyitsmovementalongtheguidesonwhichshotfallingfromthesurfaceoftherollsaccumulates,thebeltgetsoutofalignment.Asaresult,theimpactofthestreamofshotonthesurfaceisnotatarightangle,butglancing,whichproducesapoorersurfacequality.Placingastripundertheguneliminatedthisproblem,andtherollsurfacequalitybecamesatisfactory.
InthefirstperiodofoperationthecompressedairtntheSM-2machinewasobtainedfromtheshopmaini'
ine,whichhasapressureof6atm.Accordingtoreadingsonamanometerplacedbeforethecollectoroftheshotbtaatunit,theairpressureinitdidnotexceed4.0aim.Withthispressure,evenwiththeuseofthefinestshot(DChK-0.8),theroughnessoftherollsisattheupperlimit(Ra=2.7#).
Therefore,itwasnecessarytoreducetheworkingpressureoftheair.Anairval
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