Process performance

Steel

Usually,acertainprocessingtechnologyisadopted.Thematerialisfirstmadeintoparts,andthenthepartsareassembledintoamachineorstructure,whichrequiresthematerialtohavetheperformancetoadapttotheprocessingtechnology.Generally,theprocessperformancetestisusedtodeterminewhetherthematerialissuitableforacertainprocessingtechnology(thatis,theprocessperformanceofthematerial).Theprocessperformancetestmethodisusuallytosimulatetheactualproductionprocess.

Cuttingperformance

Cuttingperformance(ormachinability)referstotheabilityofmetaltoacceptcuttingprocessing,thatis,thedifficultyofcuttingmetaltomeettherequirementsoftheworkpiece.Thisisnotonlyrelatedtothechemicalcompositionandmechanicalpropertiesofthemetalitself,butalsorelatedtothecuttingprocess(suchastoolgeometry,durability,cuttingspeed,andfeedrate,etc.).Althoughtherearemanyfactorsthataffectthecuttingperformance,themostimportantthingisthenatureofthemetalitself,especiallythehardness.WhenthemetalhardnessisHB150~230,thecuttingperformanceisthebest.

Weldingperformance

Weldingperformance(orweldability)referstowhethermetalscanbeweldedwiththeusualweldingmethodsandprocesses,andmetalswithgoodweldabilitycanbeweldedwiththeusualweldingmethodsWeldingwithtechnology;metalswithpoorweldabilitycannotbeweldedwiththeusualweldingmethodsandprocesses,butmustbeweldedwithspecificweldingmethodsandprocesses.

Whenweldingmetal,aheat-affectedzoneisformednearthewelding(seam).Intheheat-affectedzone,duetoweldingheatingandcooling,theinsideofthemetalchanges,whichmaycausecracksinthemetalduringcooling.Inthissense,theso-calledweldabilityreferstowhetherthemetalispronetocracksduringwelding.Ifcracksarepronetooccur,theweldabilityispoor.

Thechemicalcompositionofsteelhasagreatinfluenceonweldingperformance.Steelhaslowcarboncontentandgoodweldingperformance.Therefore,thesteelusedafterweldinghasacarboncontentoflessthan0.17%;highcarboncontentmakesiteasytohardenaftertheweldingiscooled,andtheincreaseinbrittlenessofthesteelwillcausecracks.Whenthemanganesecontentinthesteelis<1.6%,theweldingperformanceisbetter,andwhenthemanganesecontentis>1.6%,theweldingperformanceispoor.Thehighcontentofphosphorusandsulfurinsteelispronetoembrittlement,whichaffectstheweldingperformance.

Theimprovementofweldingmethodsandprocesseshasopenedupabroadwayfortheuseofweldingmethodstomanufacturemetalstructures(usingweldingmethodstomanufacturemetalstructuresisbetterthanriveting).Atthesametime,correspondingly,itisrequiredtoresearchandproducemorekindsofmetalmaterialssuitableforwelding.Weldingperformanceisamoreimportantprocessperformanceofmetalmaterials.Insomecases,thequalityofweldabilityisoftenthekeytodeterminingwhetherthematerialcanbeused,especiallyforordinarycarbonstructuralsteelandlow-alloystructuralsteel.

Coldbendingperformance

Metalmaterials(suchassteelplates)areoftensubjectedtocoldbending(undernormaltemperature)whenused.Ifnocracksoccurduringcoldbending,thematerialhasgoodcoldbendingperformance.Therefore,thecrackingtendencyofcoldbendingcanbeusedtomeasuretheperformanceofcoldbending.

A180°coldbendtestisgenerallyusedtoidentifythecoldbendperformanceofmetalmaterials.ThebendingtestisshowninFigure1.Thesampleisrectangularwithathicknessofamm,andthediameterofthebendingindenterforbendingisdmm.Formetalmaterialswithdifferentchemicalcompositionsanddifferentusagerequirements,therelationshipbetweendandacanbebentatd=0ord=0.50,d=a,d=2a,andd=3aaccordingtorequirements.

Afterthesampleisbent,thereisnocrackontheoutside,insideandsideofthebentpart;fractureordelaminationisconsideredasqualified.Ifthevelvetmaterialislarge,thecoldbendingperformanceisgood.

Stampingperformance

Somepartsofautomobiles,tractors,anddailyenamelutensilsarestamped.Therefore,metalmaterialsarerequiredtohaveexcellentstampingperformance.

Cuppingtest(showninFigure2)isusuallyusedtoidentifythestampingperformanceofmetalmaterials.Onthecupping(orElixen)testingmachine,thepunchpresses(punches)theplate-shapedsampleataspeedof5-25mm/min(thelowerlimitspeedisusedinthelaterperiod),andthesampleisgraduallydeformed(fromasmallshallowpittoLargedeeppit);untilthefirstcrackisfoundinthereflectoronthetestingmachineinstrument.Thenumberofgraduations(mm)indicatedbytheinstrumentisthenumberofcupping(depth).Thelargerthecupprotrusion(depth)number(mm),thebetterthestampingperformanceofthematerial.

Coldupsettingperformance

Forstandardpartssuchasbolts,screwsandrivets,theheadsofthesepartsshouldbecold-headedduringmanufacture,andthematerialsofthesepartsarerequiredtohavegoodcoldupsetting.performance.Thecoldupsettingtestisatestmethodinwhichmetalmaterialscanwithstandaspecifieddegreeofupsettingdeformationinacoldstate(normaltemperature),andtocheckwhethertherearedefects.

ThecoldupsettingtestisshowninFigure3.Whenthediameterorsidelengthofthesampleis<15mm,itisforgedwithahandhammer;whenthediameterorsidelengthis>15mm,itisforgedtothespecifiedheightwithaforgingpress(orpress):

x=h1/h=2/5or1/2,ornegotiatedbythesupplierandthebuyer.Intheformula,handh1aretheheight(mm)ofthesamplebeforeandafterupsetting,respectively.

Afterforgingtothespecifiedheight,checkthesideofthesample,iftherearenocracks,splits,tears,folds,etc.,thecoldupsettingqualityisconsideredqualified.

Polymermaterials

Viscosity

Mostpolymermaterialsareinaviscousfluidstateduringtheformingprocess,whichfacilitatesitsflowandforming.Iftheviscosityistoohigh,theformingqualityoftheproductwillbeaffected.Therefore,theappropriateviscosityshouldbedeterminedaccordingtothetypeandperformanceofthematerial,theformingmethodandtheequipment.

Themainfactorsaffectingviscosityarepolymermolecularweight,temperature,pressure,andshearrate.Increasingtemperatureandreducingpressurehavesimilareffects,whichcanreducetheviscosityofthepolymermeltandimproveitsfluidity;thehigherthemolecularweightofthepolymer.Themoreseveretheentanglement,theworsethefluidity;theviscosityofthepolymermeltwilldecreasewiththeincreaseoftheshearrate.

Shrinkage

Shrinkagereferstotheremovalofthemoldedproductfromthemold.Thephenomenonofdimensionalshrinkageaftercoolingtoroomtemperatureforseveralhours.Themainreasonsfortheshrinkagearethermalexpansionandcontractionofthepolymer,thecompressibilityandelasticrecoveryofthepolymer,thecrystallizationofthepolymermelt,andthemolecularorientationofthepolymermelt.Theformingshrinkageratecanbeexpressedas:

Themainfactorsthataffecttheshrinkagearetheproductitself(typeofmaterial,structuralshape,etc.),formingconditions(formingpressure,formingtemperature,formingtime,etc.),moldvariables(moldStructure,moldtemperature,gatedesign,etc.).Productswithcomplexshapes,smallsizes,thin-walled,porous,etc.,havelessshrinkage;thegreatertheformingpressure,thestrongertheelasticrecoveryoftheproduct,andthesmallertheshrinkage:thehighertheformingtemperature,thegreaterthermalexpansionandcontraction.Thegreatertheshrinkage;thelongertheformingtime,thelongerthecoolingtimeandthesmallertheshrinkage,buttoolongcoolingtimewillaffectproductionefficiency.

Hygroscopicity

Hygroscopicityreferstothesensitivityofvariousadditivesinthepolymertowater.Thegreaterthehygroscopicityofthematerial,themorelikelyitistoundergohydrolysisduringtheformingprocess,resultingindefectssuchasbubblesorroughsurfaceintheproduct,andalsoaffectingitselectricalproperties.Therefore,thepolymerandadditivesshouldbedriedbeforeforming.

Orientationeffect

Orientationeffectmeansthatthefibrousfiller(suchasshortglassfiber,woodflour,etc.)andpolymerinthematerialwillbearrangedinparallelalongtheflowdirectionduringforming.Ifthereisanorientationeffectintheproduct,theproductwillappearanisotropy.Whenformingthickandlargeproducts,theorientationeffectshouldbeactivelyeliminatedtoavoiddeformationorcrackingoftheproduct.

Solderability

Thermoplasticscansoftenatacertaintemperatureuntilviscousflow,andthenhardenagainaftercooling.Inthisreversiblechangeprocessthatcanberepeatedmanytimes,thechemicalpropertiesofmacromoleculesremainunchanged.Therefore,thermoplasticshavegoodweldabilityandcanbeweldedtoform.