已阅读5页,还剩2页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
JournalofUniversityofScienceandTechnologyBeijiregVolume13,Number1,February2006,Page60MaterialsEvaluationofthemold-fillingabilityofalloymeltinsqueezecastingHaiyingZhang),ShumingXing),QinghuaZhang,JianboandWenLid)1)SemisolidFormingResearchCenter,BeijingJiaotongUniversity,Beijing100044,China2)ShijiazhuangLocomotiveDepot,Shijiazhuang050000,China3)DepartmentofMaterialandEngineering,HebeiUniversityofScienceandTechnology,Shijiazhuang050018,China(Received2004-12-13)Abstract:Themold-fillingabilityofalloymeltinsqueezecastingprocesswasevaluatedbymeansofthemaximumlengthofAr-chimedesspiralline.Atheoreticalevaluatingmodeltopredictthemaximumfillinglengthwasbuiltbasedontheflowingtheoryoftheincompressibleviscousfluid.Itwasprovedbyexperimentsandcalculationsthatthemold-fillingpressureandvelocityareprominentinfluencingfactorsonthemold-fillingabilityofalloymelt.Themold-fillingabilityincreaseswiththeincreaseofthemold-fillingpressureandthedecreaseofthepropermold-fillingvelocity.Moreover,thepouringtemperaturerelativelyhaslessef-fectonthemold-fillingabilityundertheexperimentalconditions.Themaximumdeviationoftheoreticalcalculatingvalueswithex-perimentalresultsislessthan15%.Themodelcanquantitativelyestimatetheeffectofeveryfactoronthemold-fillingability.Keywords:squeezecasting;processparameters;mold-fillingability;theoreticalcalculation;experimentalevaluation1.IntroductionThemold-fillingabilityofalloymeltcandirectlyaffecttheinnerqualityandsurfaceroughnessoftheproducts,andisregardedasabasicprobleminthefieldofmaterialformingprocess,especiallyinthere-searchesofnewmaterialsandprocesses.Inthetradi-tionalcastingtechnology,theevaluationofthemold-fillingabilityiscarriedonbymeasuringthemaximumfillinglengthofaspiral-linespecimen;however,thisevaluationislimitedforcastingmaterials,mouldma-terials,pouringtechnologiesandformingmethods.Henceinspecialcastingprocesssuchassqueezecasting,semisolidmetalcasting,lostfoamcastingandsoon,itisanewproblemtoevaluatethemold-fillingabilityofalloymelt.S.M.Xinginvestigatedthemold-fillingabilityofsemisolidalloyinthemoldwithmanyholesofdifferentdiametersunderapressure,andproposedatheoreticalformulaofthefillinglength11.Recently,JulioAguilar2designedameandersampleofAZ91alloywithalengthof2420mmtoevaluatethefillingabilityofalloysinthedie-castingprocess.Becausethereisnotanavailableformulatopredictfillinglength,thisevaluationmethodisnotconvenientinengineering.T.J.Zhang3investigatedtherelationshipbetweenmagneticfluxdensityandinputvoltageaswellasdistance,andfoundthatthemold-fillinglengthofthemeltincreasesrapidlywiththeincreaseoftheaveragemagnetic-fluxdensity,andCorrespondingauthor:HaiyingZhang,E-mail:thattheuppersteelmoldissuperiortotheuppergyp-summold.Moreover,inresearchingonhighpressurediecasting,S.Kulasegaram4,Z.Liu5,andClearyPaul6studiedthemold-fillingabilityofalloysbysimulations.E.N.Pan7studiedtheeffectsofpour-ingtemperature,coatingthicknessetc.onthemold-filingabilityoflostfoamA356alloy,thecalculatedflowlengthbasedonamodifiedEPCFlow-Solidificationequationshowedagoodagreementwiththeexperimentalresults.Theevaluationmethodofmold-fillingabilitymainlyincludesthreetypes,ex-perimentalevaluation,theoreticalcalculation,andsimulation.Theexperimentalevaluationmethodisabasiconebecauseofitsintuitionaleffects,butitislimitedfortheexperimentalconditionsandisdifficultforpopularuse.Thesimulationmethodisnotcon-venientinengineeringthoughitismoreexactthantheexperimentalmethodingivenconditions.However,thetheoreticalcalculationmethodcanbeusedcon-venientlytopredictthefillingabilityofvariousalloysinvariousprocesseswithoutanyspecialequipment.Squeezecastingisanewformingtechnologythatisexpectedtobewidelyusedinthefuture.However,thefillingabilityofalloymeltintheprocessisnotclear.Studiesevaluatingthemold-fillingabilityofalloymeltinsqueezecastingarefew.Inthisarticle,ex-perimentalevaluationandtheoreticalcalculationarecombined,andamathematicalmodelforcalculatingmold-fillingabilityisobtained.H.Y.Zhngetal.,Evaluationofthemold-fillingabilityofalloymeltinsqueezecasting612.Experimentalevaluationofthemold-fillingabilityinsqueezecastingBasedonspiral-linespecimeningravitycasting,aspecialspiral-line-specimenmoldisdesigned(showninFig.l),whichisusedforexperimentalevaluationofthemold-fillingabilityofalloymeltinsqueezecasting.ThemoldismadeofH13steel.Itsconstruc-tionmainlyincludesthreeparts,theuppermold,thelowermold,andthepunch.Fittedontheglide-pieceoftheformingdevice,theuppermoldhasanAr-chimedesspiral-linecavitywithatotallengthof1350mm.Thelowermoldisfittedontheworktableoftheformingdevice;itsmold-cavityisthecylindricalpressingchamber.Inthesidewallofthepressingchamber,thereisarunnerthatconnectswiththeAr-chimedesspiral-linecavity.Thepunchconnectswithmold-fillingpistonoftheformingdevice.Theformingdeviceisthedouble-actionhydraulicpresseswhichhasthefunctionssuchasmold-locking,mold-filling,ejecting,andmold-fillingvelocitytransiting.Theprocessparameterssuchasmold-fillingpressure,pressingvelocity(mold-fillingvelocity)etc.canbesetandtheexperimentaldatacanbesavedautomaticallybyacomputercontrollingsystem.Theformingtypeisinverted-extrusioninwhichthealloymeltinthecyl-indricalchamberispressedintotheArchimedesspi-ral-linecavitythroughtherunnerinvertedtothepunchmovingdirection.3Fig.2.Archimedesspiral-linespecimen.Aftermelting,alloymeltispouredintothecylin-dricalchamberofthelowermold,theuppermoldmovesdowntooclosetothelowermoldunderahy-draulicpress.Then,thepunchdropsnearthealloysurfacewithafastvelocityandthenpressesthealloymeltwithaslowvelocityintotheArchimedesspiral-linecavity.Keepingasettime,theuppermoldde-tacheswiththelowermold,andtheArchimedesspi-ral-linespecimenisobtained(showninFig.2).Fi-nally,thelengthsoftheArchimedesspirallinesaremeasured.3.Mathematicalevaluationofthemold-fillingability3.1.DatapreparationThegeometricaldimensionsofthepressingcham-ber,therunnerandthespiral-linecavityareshowninFig.3.Fig.1.Spiral-line-specimenmold:1-thepunch:2-theuppermold:3-thelowermold:4-thepressingchamber.diFig.3.Schematicdiagramofthemold.1-thepunch:2-thepressingchamber:3-therunner;4-thespirallineDuringthemold-fillingprocessinsqueezecasting,thereexiststwotypesofforces:oneisthedrivingpowersthatforcealloymelttoflowtotheArchimedes62J.Univ.Sci.Technol.Beijing,Voh13,No.1,Feb2006spiral-linecavity;theotheristheresistantpowerswhichblockoffflowingandcausethepressurelosing.Whenthedrivingpowersarelessthantheresistantpowers,alloymeltwillstopfilling,andthefillinglengthreachesthemaximumlengthL,simultane-ously.Thedrivingpowersmainlyincludethemold-fillingpressureprovidedbythepunchandthegravityofalloymelt.Itisconsideredthatthegravityisfarlessthanmold-fillingpressurethatcanbeignored.Theresistantpowersmainlyincludethefrictionre-sistanceandthepartialresistance.Hencetheconditionsforkeepingalloymeltfillingcanbedescribedbythefollowingequation:P2F(1)wherePisthemold-fillingpressureandFisthetotalresistanceofthefrictionresistanceandthepartialresistance.Insqueezecasting,alloymeltcanberegardedasastable,incompressibleviscousfluid.Thatistosay,thealloydensitypisaconstantinthefillingprocess.Supposetheviscositycoefficientofalloymeltvkeepsaconstantinthewholemold-fillingprocess.Thepressureprovidedbythepunchinthepressingchamberisnamedasmold-fillingpressureP.Themovingvelocityofthepunchisregardedastheaver-ageflowiligvelocityVofalloymeltinthepressingchamber(namedasmold-fillingvelocity).Basedonthecontinuousequationoffluid,theaveragevelocityofalloymeltintherunnerisVo=AV/Aoandtheav-eragevelocityofalloymeltinthespiral-linecavityisVl=AV/Al,whereA,Ao,Alarethecross-sectionareaofthepressingchamber,therunner,andthespiral-linecavity,respectively.Supposethewholepressingchamberispouredwithalloymeltatthebeginning,themovingheightofthepunch(thedescendheightofalloymeltinthepressingchamber)isHandconsequentlythelengthfilledspirallineisL.Basedonthemassconservationlaw,therelationshipofHandLisHZ-A1LA3.2.Frictionresistance(1)Frictionresistancegeneratedfromthealloymeltflowinthepressingchamber.WhentheReynoldsnumberislessthan2300,theflowingstateofalloymeltisregardedasalaminarflow,andwhentheReynoldsnumberismorethan4000,theflowingstateisregardedasaturbulentflow.Otherwise,theflowingstateisatransitionalflowstateinterveninglaminarflowwithturbulentflow.TheReynoldsnumberofthealloymeltflowinthepress-ingchamberisRe=VDlv,whereDisthediameterofthepressingchamber.Ifitisalaminarflow,thefrictionresistancecoefficientist1=641Re8.Basedonthemomentumtransmitequationofthein-compressibleviscousfluid,thefrictionresistanceinthepressingchamberisHpV202ReD02313.6HpV2-313.6HpvVFl=9.8t1-=-(34Ifitisaturbulentflow,thecoefficientoffrictionS,sothefric-0.129-0.129resistanceiscl=Re0.2-fVD)O(UJtionresistanceisIHpV20.632HpV2-0.632HpV2F1=9.8&-=-D2D.(,),.12(3b)(2)Frictionresistancegeneratedfromtheflowofalloymeltintherunner.Similarly,theReynoldsnumberofthealloymeltflowintherunnerisRe0=VoDo/v=AVDo/Aov,whileDoisshownintheFig.3.TheReynoldsnumbervarieswiththedifferenceoftheflowvelocityandtherunnerdimension.Sotheflowingstateisalaminarfloworaturbulentflowunderdifferentconditions.Ifitisalaminarflow,thecoefficientoffrictionresis-tanceist2=641Re0=64Aov/AVDo,andhencethefrictionresistanceisHpVo2-313.6Hp(AV)2-313.6HApvVF2=9.852-Do2ReoDoAo2AoDo2(44Ifitisaturbulentflow,thecoefficientoffriction,therefore-I0.129resistanceisl2=-Reoo.12AVD.thefrictionresistanceis-F2=9.852,-HpVo2=_0.632Hp(AV)DO2Reo0.12DoAo20.6328pA2V0.12AVDo(3)FrictionresistancegeneratedfromthealloymeltflowintheArchimedesspiral-linecavity.H.Y.ZhangetaL,Evaluationofthemold-fillingabilityofalloymeltinsqueezecasting63AccordingtothedimensionoftheArchimedesspi-ral-linecavity,themaximumofd/D1isonly0.1,dandD,areshowninFig.3,sothecoefficientofpartialresistanceisverylittle,thealloymeltflowintheAr-chimedesspiral-linecavityisregardedastheflowinthedirectpipeandthepartialresistanceisignored.TheReynoldsnumberisdenotedasRel=Vldlv=AVd/Alv.Thecoefficientoffrictionresistanceforalaminarflowist3=/Rel=64A1v/AVd,thereforethefrictionresistanceisLpV12d2Re,dA12Ald313.6LP(AV)-313.6LApvVF3=9.853-=-(54Ifitisaturbulentflow,thecoefficientoffriction-resistanceist3=-0129,andhencetheRelo.fAVd)12frictionresistanceis-F3=9.853I-LpV12=-0.632Lp(AV)2d2Re10.2dl0.632LApV3.3.PartialresistanceWhenalloymeltflowsfromthepressingchambertotherunnerandthentothespiral-linecavity,thepartialresistanceisgeneratedfromthemomentumlosingcausedbychangesinflowvelocitydirectionandinflowspace.Whentheflowingstateisaturbu-lentflow,theresistancelosingincreasesproportion-allywiththesquareofaveragevelocityandisshowninthefollowingequation8:whereKPartisthecoefficientofpartialresistance.Whenthemeltflowfromthepressingchambertotherunner,thecoefficientofpartialresistanceisasshowninthefollowing
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2024年中学美术教研组工作计划
- 2024年主任护师专业技术工作总结
- 2024年为患病同学捐款倡议书
- 2024年中小学教师考核述职报告
- 镍钴矿在新材料研究中的重要应用
- SY-T 6644-2018 使用注入压力操作阀的连续气举设计及施工作业规程
- 2024年福建省中考语文模拟测试卷
- 线材芯线绞距
- 小学一年级寒假作业
- 出国事务处理授权
- 初中道德与法治-走进老师教学设计学情分析教材分析课后反思
- 信息化项目管理办法-团队建设与管理策略
- 水电解质代谢紊乱诊断治疗指南
- 2023届上海市静安区高三二模作文题目解析:道路坎坷不平人心也不平
- 广告创意文化知到章节答案智慧树2023年吉林大学
- 风电基础工程清单报价汇总表
- 美世-职位说明书与任职资格管理
- 院内按病种分值付费(DIP)专题培训
- 医院临床科室质控分析总结报告表模板
- 运输物流公司简介范文
- 机械设备点检员(三级)考试题库-上(单选题)
评论
0/150
提交评论