机械加工机械类外文翻译中英文翻译Word格式文档下载.docx
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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
Extreme-
pressuresoluble
oil,semi-
syntheticor
syntheticfluid
fluid(neatcuttingoilsmaybe
necessary)
Drilling
Extreme
oil,semi
GearShapping
semi-syntheticorsyntheticfluid
Neat-cuttingoilspreferable
Hobbing
Extreme-pressuresolubleoil,semi-syntheticor
syntheticfluid(neatcuttingoilsmaybepreferable)
Neat-cutting
oils
preferable
Bratching
Extreme-pressuresolubleoil,semi-syntheticorsyntheticfluid(neat
cuttingoilsmaybepreferable)
Tapping
syntheticfluid(neatcuttingoilsmaybenecessary)
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].Thesameimageofm