锻压emphasis.docx

锻压emphasis.docx

《锻压emphasis.docx》由会员分享，可在线阅读，更多相关《锻压emphasis.docx（12页珍藏版）》请在冰点文库上搜索。

锻压emphasis

ReviewandQuestion

Chapter13RollingofMetals

1、Whatisthedefinitionoftherolling?

theprocessofreducingthethickness（orchangingthecross-section）ofalongworkpiecebycompressiveforcesappliedthroughasetofrolls（轧辊）.

3、Whatistheflatrolling?

FlatrollingorRollingisdefinedasthereductionofthecross-sectionalareaofthemetalstock,orthegeneralshapingofthemetalproducts,throughtheuseoftherotatingrolls

Astrip（带料/条料）ofthicknesshoenterstherollgap（辊缝/辊隙/辊间距离）andisreducedtothicknesshfbyapairofrotatingrolls,eachrollbeingpoweredthroughitsownshaftbyelectricmotors（电动机）.

4、Whatisthedifferencebetweenaplateandasheet?

Platearegenerallyregardedas

（1）havingathicknessgreaterthan6mm,are

（2）usedforstructuralapplications,suchasmachinestructures,shiphulls,boilers,bridgesandnuclearvessels.

Sheetsaregenerally

（1）lessthan6mmthick;theyareprovidedtomanufacturingfacilitiesasflatpiecesor

（2）asstripincoilsforfurtherprocessingintovariousproducts.

7、Explaintheadvantagesanddisadvantagesofthefrictionduringtherolling.

DisadvantageOfFriction

Althoughfrictionisnecessaryforrollingmaterials,

（1）energyisdissipatedinovercomingfriction;thus,increasingfrictionmeansincreasingforcesandpowerrequirements.

Furthermore,

（2）highfrictioncoulddamagethesurfaceoftherolledproduct.Acompromisehastobemade,onewhichincludeslowcoefficientsoffrictionbyusingeffectivelubrication（润滑）.

9、Describethedifferencebetweenabloom,aslab,andabillet.

Slab

（1）usuallyrectangularincross-section.

（2）Slabsarerolledintoplatesandsheetslater.

Bloom

（1）usuallyhasasquarecross-section,atleast150mmontheside.

（2）Bloomsareprocessedfurther,byshapingrolling,intostructureshapes,suchasI-beamsandrailroadrails.

Billets

（1）areusuallysquare,withacross-sectionareasmallerthanblooms;

（2）theyarelaterrolledintovariousshapes,suchasroundrodsandbars,byetheuseofshapedrolls.

11、Whatisthehotrollingandcoldrolling?

Therollingpracticewhichisdoneabovetherecrystallization（再结晶）temperatureofthemetaliscalledhotrolling

coldrollingiscarriedoutatroomtemperature

12、Whatisthedifferencebetweencaststructureandwroughtstructure?

Thecharacteristicsofacaststructure（铸造结构）:

（1）typicallydendritic（树枝状的）,

（2）includescoarseandnonuniformgrains.

（3）usuallybrittle（易碎的）andporous（多孔的）

Thecharacteristicsofawroughtstructure（锻造结构）:

（1）finergrainssize

（2）enhancedductility（柔韧性）

13、Whatisthedifferencebetweenhotrollingandcoldrolling?

?

AdvantagesofHotrolling

•reducegrainsize

•improvestrengthandductility（塑性/延展性/柔韧性）

–breakingupbrittlegrainboundaries（晶界）

–closingup（压合/压实）internaldefects（内部缺陷）,especiallyporosity（多孔性）

Comparedtohotrolling,coldrollingproducessheetandstripwithmuchbetter:

（1）surfacefinish（becauseoflackofscale）,

（2）dimensionaltolerances

（3）mechanicalproperties（becauseofstrainhardening）.

14、Whatisscale?

Scaleisadefectoftherollingproductsdevelopedduringhotrolling.

16、Whatistheshaperolling?

Straightandlongstructureshapes,suchassolidbars（withvariouscross-section）,channels,I-beams,andrailroadrails,arerolledbypassingthestock（原料）throughasetofspeciallydesignedrolls.

17、Makealistofsomepartsthatcanbemadebyshaperolling.

•Variousshapescanbeproducedbyshaperolling

–bars

–channels（槽钢）

–I-beams（工字梁）

–railroadrails

•VariousshapescanbeproducedbyRingRolling

largeringsforrockets（火箭）andturbines（涡轮）

-gearwheelrims（边缘带齿的轮子）

-ball-bearingandroller-bearingraces（滚珠轴承与滚柱轴承环）

-flanges（法兰盘）

-reinforcingrings（增强环/补强环）forpipes.

Chapter14ForgingofMetals

3、Whatdothetypicalforgedproductsinclude?

bolts（螺栓）andrivets（铆钉）,connectingrods,shaftsforturbines（涡轮）,gears（齿轮）、handtools,andstructuralcomponentsformachinery,aircraftrailroads,andavarietyofothertransportationequipment.

4、Whataretheadvantagesoftheforgingparts?

?

Metalflowandgrainstructurecanbecontrolled,soforgedpartshavegoodstrengthandtoughness;theycanbeusedreliablyforhighlystressedandcriticalapplications

5、Whatisthedifferencebetweencastparts,cuttingpartsandforgingparts?

铸造件（Casting）有inevitable缺陷，如晶粒粗大、结构疏松、具有多孔，其组织和性能均较差。

切削件（Machining）的内部晶粒大小和结构不改变，且其金属纤维组织被切断了，使得零件强度下降。

锻造件（Forging）在经受了塑性变形和再结晶，粗大的树枝状结晶组织被破碎，疏松和孔隙被压实、焊合，内部组织和性能都得到了提高

9、Whatistheopen-dieforging?

Open-dieforgingisthesimplestforgingprocess.Itcanbedepictedbyasolidworkpieceplacedbetweentwoflatdiesandreducedinheightbycompressingit.

10、Whatisthedifferencebetweenidealforgingandactualforging?

Uniformdeformationofthebilletunderidealconditions.Becauseconstancyofvolumeismaintained,anyreductioninheightincreasesthediameteroftheforgedpart.

Inactualoperations,thepartdevelopsabarrelshape;thisdeformationisalsoknownaspancaking（压扁）

causedbyfrictionalforcesatthedie-workpieceinterfaces

–canbeminimizedifaneffectivelubricantisused

–causedbythermaleffects（热效应）inhotforgingcanbe

minimizedbyusingheateddies

14、Whatisthedifferencebetweenopen-dieforgingandimpression-dieforging？

Inimpression-dieforging,theworkpieceacquirestheshapeofthediecavities（impressions）whilebeingforgedbetweentwoshapeddies.

15、Whatistheflash?

Howtoformtheflash?

Whatisthesignificanceoftheflash?

flash,whichisexcessmetalthatissubsequentlytrimmedoff.

thatsomeofthematerialflowsoutwardandformsaflash,

Becausethethinflashcoolsrapidlyandhashigherfrictionalresistancethandiecavity,itsubjectsthematerialinthediecavitytohighpressures,therebyencouragingthefillingofthediecavity.

22、Whatisthedifferencebetweenfulleringandedging?

Infullering,materialisdistributedawayfromanarea

Inedging,materialisgatheredintoalocalizedarea

33、Whatisthesignificanceoflubricationtotheforgingprocess?

1）Becauselubricantsgreatlyinfluencefrictionandwear,theyaffecttheforcesrequiredandtheflowofthemetalindiecavities;

2）Theycanactasathermalbarrierbetweenthehotworkpieceandtherelativelycooldies,slowingtherateofcoolingoftheworkpieceandimprovingmetalflow.

3）Lubricantsserveasapartingagentwhichinhibitstheforgingformstickingtothediesandhelpsinitsreleasefromthedie.

34、HowtoApplylubricantsinforging?

Inhotforging,thelubricantsisusuallyapplieddirectlytothedies;

Incoldforging,thelubricantsisusuallyappliedtotheworkpiece.

35、Whatistheforgeability?

Forgeabilityisgenerallydefinedasthecapabilityofamaterialtoundergodeformationwithoutcracking

Chapter15ExtrusionandDrawingofMetals

1、Whatistheextrusionprocess?

Intheextrusionprocess,abillet（generallyround）isforcedthroughadie,inamannersimilartosqueezingtoothpastefromatube.

2、Whatkindofproductscanbemadebyextrusion?

Almostanysolidorhollowcross-sectionmaybeproducedbyextrusion,whichcancreateessentiallysemifinishedparts

Typicalproductsmadebyextrusionarerailingsforslidingdoors,tubinghavingvariouscross-section,structuralandarchitecturalshapes,anddoorandwindowframes.

5、Whatisdrawing?

Drawingisanoperation,developedbetweenA.D.1000and1500,inwhichthecross-sectionofsolidrod,wire,ortubingisreducedorchangedinshapebypullingitthroughadie

6、Whatkindofproductscanbemadebydrawing?

Drawnrodsareusedforshafts,spindles,andsmallpistonsandasrawmaterialforfastenerssuchasrivets,bolts,andscrews.Inadditiontoroundrods,variousprofilescanalsobedrawn.

8、Whatisthedifferencebetweendirectextrusion,indirectextrusion,HydrostaticExtrusionandlateralExtrusion

Directextrusionalsoiscalledforwardextrusion,aroundbilletisplacedinachamber（container）andforcedthroughadieopeningbyahydraulically-drivenramorpressingstem.Themetalflowsinthesamewaythatthepressingstemmoves

Inindirectextrusion（reverse,inverted,orbackwardextrusion）,thediemovestowardthebillet.

Thedirectionofthemetalflowsisoppositetothatthatthepressingstemmoves

Inhydrostaticextrusion,thebilletissmallerindiameterthanthechamber,whichisfilledwithafluid,andthepressureistransmittedtothebilletbyaram.Unlikeindirectextrusion,thereisnofrictiontoovercomealongthecontainerwalls.

Anothertypeofextrusionislateral,orside,extrusion

10、WhatisCCD?

Circumscribing-circlediameter,abbreviatedCCD,isaparameterdescribingtheshapeoftheextrudedproduct.Itisthediameterofthesmallestcircleintowhichtheextrudedcross-sectionwillfit

11、Whatistheshapefactor?

Thecomplexityofanextrusionisafunctionoftheratiooftheperimeteroftheextrudedproducttoitscross-sectionalarea,knownastheshapefactor.

13、Whatcausesthedeadzone?

wherethemetalatthecornersisessentiallystationary（静止的）

–mainlyduetofriction

Theparametersrelatedtothediezone

Ø

（1）dieangle,a:

a↑,diezone↑（a大，死区大，但制品表面质量好；a小，死区小，制品表

面质量差。

）

Ø

（2）friction:

externalfriction↑,diezone↑

Ø（3）R:

R↑,diezone↑

Ø（4）temperature:

T↑→externalfriction↑→diezone

15DescribeusualQuestionsinExtrusion

1、diewearcanbeexcessive;

2、coolingofthehotbilletinthechambercanbeaproblemwhichresultsinhighlynonuniformdeformation;

3、Thebilletmaydevelopanoxidefilmunlessheatedinaninert-atmosphere.

Thisfilmcanbeabrasive,anditcanaffecttheflowpatte