机械加工工艺夹具类外文文献翻译中英文翻译外文翻译.docx
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机械加工工艺夹具类外文文献翻译中英文翻译外文翻译.docx
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机械加工工艺夹具类外文文献翻译中英文翻译外文翻译
TOOLWEARMECHANISMSONTHEFLANKSURFACEOFCUTTINGINSERTS
FORHIGHSPEEDWETMACHINING
5.1Introduction
Almosteverytypeofmachiningsuchasturning,milling,drilling,grinding...,usesacuttingfluidtoassistinthecosteffectiveproductionofpartsassetupstandardrequiredbytheproducer[1].Usingcoolantwithsomecuttingtoolsmaterialcausesseverefailureduetothelackoftheirresistancetothermalshock(likeAL2O3ceramics),usedtoturnsteel.Othercuttingtoolsmaterialslikecubicboronnitride(CBN)canbeusedwithoutcoolant,duetothetypeoftheirfunction.TheaimofusingCBNistoraisethetemperatureoftheworkpicetohighsoitlocallysoftensandcanbeeasilymachined.Thereasonsbehindusingcuttingfluidscanbesummarizedasfollows.
®Extendingthecuttingtoollifeachievedbyreducingheatgeneratedandasaresultlesswearrateisachieved.Itwillalsoeliminatetheheatfromtheshearzoneandtheformedchips.
®Coolingtheworkpieceofhighqualitymaterialunderoperationplaysanimportantrolesincethermaldistortionofthesurfaceandsubsurfacedamageisaresultofexcessiveheatthatmustbeeliminatedorlargelyreducedtoproduceahighqualityproduct.
Reducingcuttingforcesbyitslubricatingeffectatthecontactinterfaceregionandwashingandcleaningthecuttingregionduringmachiningfromsmallchips.Thetwomainreasonsforusingcuttingfluidsarecoolingandlubrication.
CuttingFluidasaCoolant:
Thefluidcharacteristicsandconditionofusedeterminethecoolantactionofthecuttingfluid,whichimprovestheheattransferattheshearzonebetweenthecuttingedge,workpiece,andcuttingfluid.Thepropertiesofthecoolantinthiscasemustincludeahighheatcapacitytocarryawayheatandgoodthermalconductivitytoabsorbtheheatfromthecuttingregion.Thewater-basedcoolantemulsionwithitsexcellenthighheatcapacityisabletoreducetoolwear[44].
CuttingFluidasaLubricant:
Thepurposeistoreducefrictionbetweenthecuttingedge,rakefaceandtheworkpiecematerialorreducingthecuttingforces(tangentialcomponent).Asthefrictiondropstheheatgeneratedis
dropped.Asaresult,thecuttingtoolwearrateisreducedandthesurfacefinishisimproved.
CuttingFluidProperties
Freeofperceivableodor
Preserveclaritythroughoutlife
Kindandunirritatedtoskinandeyes.
Corrosionprotectiontothemachinepartsandworkpiece.
Costeffectiveintermsofftoollife,safety,dilutionratio,andfluidlife.[1]
5.1.1CuttingFluidTypes
Therearetwomajorcategoriesofcuttingfluids
NeatCuttingOils
Neatcuttingoilsarepoorintheircoolantcharacteristicsbuthaveanexcellentlubricity.Theyareappliedbyfloodingtheworkareabyapumpandre-circulatedthroughafilter,tankandnozzles.Thistypeisnotdilutedbywater,andmaycontainlubricityandextreme-pressureadditivestoenhancetheircuttingperformanceproperties.Theusageofthistypehasbeendecliningfortheirpoorcoolingability,causingfirerisk,proventocausehealthandsafetyrisktotheoperator[1].
®WaterBasedorWaterSolubleCuttingFluids
Thisgroupissubdividedintothreecategories:
1.Emulsion`mineralsoluble'white-milkycolorasaresultofemulsionofoilinwater.Containfrom40%-80%mineraloilandanemulsifyingagentbesidecorrosioninhibitors,besidebiocidetoinhibitthebacteriagrowth.
2.Microemulsion`semi-synthetic'inventedin1980's,haslessoilconcentrationand/orhigheremulsifierratio10%-40%oil.Duetothehighlevelsofemulsifiertheoildropletsizeinthefluidaresmallerwhichmakethefluidmoretranslucentandeasytoseetheworkpieceduringoperation.Otherimportantbenefitisinitsabilitytoemulsifyanyleakageofoilfromthemachinepartsinthecuttingfluid,acorrosioninhibitors,andbacteriacontrol.
3.Mineraloilfree`synthetic'isamixofchemicals,water,bacteriacontrol,corrosioninhibitors,anddyes.Doesnotcontainanymineraloils,andprovidesgoodvisibility
.23totheworkpiece.bareinmindthatthelackofmineraloilinthistypeofcutting
fluidneedstotakemoreattentiontomachinepartslubricationsinceitshouldnotleaveanoilyfilmonthemachineparts,andmightcausesealsdegradationduethelackofprotection.
5.1.2CuttingFluidSelection
Manyfactorsinfluencetheselectionofcuttingfluid;mainlyworkpiecematerial,typeofmachiningoperation,machinetoolparts,paints,andseals.Table5-1preparedatthemachinetoolindustryresearchassociation[2]providessuggestionsonthetypeoffluidtobeused.
5.1.3CoolantManagement
Toachieveahighlevelofcuttingfluidsperformanceandcosteffectiveness,acoolantrecyclingsystemshouldbeinstalledinthefactory.Thissystemwillreducetheamountofnewpurchasedcoolantconcentrateandcoolantdisposable,whichwillreducemanufacturingcost.Iteitherdonebythecompanyitselforberentedout,dependsonthebudgetandmanagementpolicyofthecompany[1].
Table5-1Guidetotheselectionofcuttingfluidsforgeneralworkshopapplications.
Machining
operation
Workpiecematerial
Freemachining
andlow-
carbonsteels
Medium-
Carbonsteels
HighCarbon
andalloysteels
Stainlessand
heattreated
resistant
alloys
Grinding
Cleartypesolubleoil,semisyntheticorchemicalgrindingfluid
Turning
Generalpurpose,solubleoil,semi
syntheticorsyntheticfluid
Extreme-pressuresolubleoil,
semi-syntheticorsynthetic
fluid
Milling
General
purpose,
solubleoil,
semisynthetic
orsynthetic
fluid
Extreme-
pressuresoluble
oil,semi-
syntheticor
syntheticfluid
Extreme-pressuresolubleoil,
semi-syntheticorsynthetic
fluid(neatcuttingoilsmaybe
necessary)
Drilling
Extreme
pressuresoluble
oil,semi
syntheticor
syntheticfluid
GearShapping
Extreme-pressuresolubleoil,
semi-syntheticorsyntheticfluid
Neat-cuttingoilspreferable
Hobbing
Extreme-pressuresolubleoil,semi-syntheticor
syntheticfluid(neatcuttingoilsmaybepreferable)
Neat-cutting
oils
preferable
Bratching
Extreme-pressuresolubleoil,semi-syntheticorsyntheticfluid(neat
cuttingoilsmaybepreferable)
Tapping
Extreme-pressuresolubleoil,semi-syntheticor
syntheticfluid(neatcuttingoilsmaybenecessary)
Neat-cutting
oils
preferable
Note:
someentreisdeliberatelyextendovertwoormorecolumns,indicatingawiderangeofpossibleapplications.Otherentriesareconfinedtoaspecificclassofworkmaterial.
AdoptedfromEdwardandWright[2]
5.2WearMechanismsUnderWetHighSpeedMachining
Itisacommonbeliefthatcoolantusageinmetalcuttingreducescuttingtemperatureandextendstoolslife.However,thisresearchshowedthatthisisnotnecessarilytruetobegeneralizedovercuttinginsertsmaterials.Similarresearchwascarriedoutondifferentcuttinginsertsmaterialsandcuttingconditionssupportingourresults.Guetal[36]haverecordedadifferenceintoolwearmechanismsbetweendryandwetcuttingofC5millinginserts.Tonshoffetal[44]alsoexhibiteddifferentwearmechanismsonAL2O3/TiCinsertsinmachiningASTM5115,whenusingcoolantsemulsionscomparedtodrycutting.Inaddition,AvilaandAbrao[20]experienceddifferenceinwearmechanismsactivatedattheflankside,whenusingdifferentcoolantsintestingAL2O3lTiCtoolsinmachiningAISI4340steel.Thewearmechanismsandthebehaviorofthecuttinginsertsstudiedinthisresearchunderwethighspeed-machining(WHSM)conditionisnotfullyunderstood.Therefore,itwastheattemptofthisresearchtofocusonthecontributionsincoatingdevelopmentandcoatingtechniquesofnewlydevelopedmaterialsinordertoupgradetheirperformanceattoughmachiningconditions.Thisvaluableresearchprovidesinsightintoproductiontimesavingsandincreaseinprofitability.Costreductionsareessentialinthecompetitiveglobaleconomy;thusprotectinglocalmarketsandconsistinginthesearchofnewones.
5.3ExperimentalObservationsonWearMechanismsofUn-CoatedCementedCarbideCuttingInsertsinHighSpeedWetMachining
Inthissection,theobservedwearmechanismsarepresentedofuncoatedcementedcarbidetool(KC313)inmachiningASTM4140steelunderwetcondition.Theoverallperformanceofcementedcarbideunderusingemulsioncoolanthasbeenimprovedintermsofextendingtoollifeandreducingmachiningcost.Differenttypesofwearmechanismswereactivatedatflanksideofcuttinginsertsasaresultofusingcoolantemulsionduringmachiningprocesses.Thiswasduetotheeffectofcoolantinreducingtheaveragetemperatureofthecuttingtooledgeandshearzoneduringmachining.Asaresultabrasivewearwasreducedleadinglongertoollife.Thematerialsofcuttingtoolsbehavedifferentlytocoolantbecauseoftheirvariedresistancetothermalshock.Thefollowingobservationsrecordedthebehaviorofcementedcarbideduringhighspeedmachiningunderwetcutting.
Figure5-1showstheflanksideofcuttinginsertsusedatacuttingspeedof180m/min.TheSEMimageswererecordedafter7minutesofmachining.Itshowsmicro-abrasionwear,whichidentifiedbythenarrowgroovesalongtheflanksideinthedirectionofmetalflow,supportedwithsimilarobservationsdocumentedbyBarnesandPashby[41]intestingthrough-coolant-drillinginsertsofaluminum/SiCmetalmatrixcomposite.Sincethecuttingedgeistheweakestpartofthecuttinginsertgeometry,edgefracturestartedfirstduetotheearlynon-smoothengagementbetweenthetoolandtheworkpiecematerial.Also,thisisduetostressconcentrationsthatmightleadtoacohesivefailureonthetransientfilletedflankcuttingwedgeregion[51,52].Thesameim
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