低压铸造和重力铸造(共6页).doc

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1、精选优质文档-倾情为你奉上 低压铸造和重力铸造 Low pressure casting and high pressure casting低压铸造是液体金属在压力作用下充填型腔，以形成铸件的一种方法。由于所用的压力较低，所以叫做低压铸造。其工艺过程是：在密封的坩埚（或密封罐）中，通入干燥的压缩空气，金属液在气体压力的作用下，沿升液管上升，通过浇口平稳地进入型腔，并保持坩埚内液面上的气体压力，一直到铸件完全凝固为止。然后解除液面上的气体压力，使开液管中未凝固的金属液流坩埚，再由气缸开型并推出铸件。Lowpressurecastingisamethodofmoltenmetalfillsthec

2、avityunderthepressureandthenformsthecasting.duetothepressureisnothigh,soitiscalledlowpressurecasting.Thetechnicalprocessis:inthehermeticcrucible(orsealedpot)injectingthedrycompressedair,moltenmetalundertheeffectofgaspressuregoesupalongthepipethenthroughthegateplacidlyrunintothecavity,thenkeepthegasp

3、ressureuppertheliquidinthecrucibleuntilthecastingsolidificationtotally.thenremovethegaspressuretomaketheunfreezingmetalinthepipeforopeningrunbackintothecrucibleandatthesametimeusethecylinderopencavitytodetrusionthecasting.低压铸造独特的优点表现在以下几个方面：Theuniquecharacteristicsoflowpressurecastingperformedasbelo

4、w:1液体金属充型比较平稳；Moltenmetalfullthecavitysmoothly.2铸件成形性好，有利于形成轮廓清晰、表面光洁的铸件，对于大型薄壁铸件的成形更为有利；Theformingpropertyisgoodandinfavorofformingtheedgeshapenessandsurfacebrightandclean.Itisfavorableforthelargecastingpartswiththinsectioncasting3铸件组织致密，机械性能高；Thetissueofcastingisdensification,andmechanicalbehavior

5、ishigh.4提高了金属液的工艺收得率，一般情况下不需要冒口，使金属液的收得率大大提高，收得率一般可达90。低压铸造独特的优点表现在以下几个方面：Theuniquecharacteristicsoflowpressurecastingperformedasbelow:1液体金属充型比较平稳；Moltenmetalfullthecavitysmoothly.2铸件成形性好，有利于形成轮廓清晰、表面光洁的铸件，对于大型薄壁铸件的成形更为有利；Theformingpropertyisgoodandinfavorofformingtheedgeshapenessandsurfacebrightand

6、clean.Itisfavorableforthelargecastingpartswiththinsectioncasting3铸件组织致密，机械性能高；Thetissueofcastingisdensification,andmechanicalbehaviorishigh.4提高了金属液的工艺收得率，一般情况下不需要冒口，使金属液的收得率大大提高，收得率一般可达90。低压铸造独特的优点表现在以下几个方面：Theuniquecharacteristicsoflowpressurecastingperformedasbelow:1液体金属充型比较平稳；Moltenmetalfulltheca

7、vitysmoothly.2铸件成形性好，有利于形成轮廓清晰、表面光洁的铸件，对于大型薄壁铸件的成形更为有利；Theformingpropertyisgoodandinfavorofformingtheedgeshapenessandsurfacebrightandclean.Itisfavorableforthelargecastingpartswiththinsectioncasting3铸件组织致密，机械性能高；Thetissueofcastingisdensification,andmechanicalbehaviorishigh.4 提高了金属液的工艺收得率，一般情况下不需要冒口，使

8、金属液的收得率大大提高，收得率一般可达90。Improve the yield rate of the molten metal,normally dont need the dead head,and make the yield rate a high improvement,usually can achieve 90%.此外，劳动条件好；设备简单，易实现机械化和自动化，也是低压铸造的突出优点。inaddition,workingconditionisgood,equipmentsisnotcomplicatedandeasytorealisemechanizationandautoma

9、tionarealsothehighlightadvantage.重力铸造是指金属液在地球重力作用下注入铸型的工艺，也称浇铸。广义的重力铸造包括砂型浇铸、金属型浇铸、熔模铸造、消失模铸造，泥模铸造等；窄义的重力铸造专指金属型浇铸。Gravitycastingisthatmoltenmetalrunintothemouldwiththepressureofearthgravity,itisalsonamedpouringcasting,generalizedpouringcastingincl.Sandcasting,metalmouldcasting,investmentcasting,eva

10、nescentmoldcastingandmuddiecasting,ect.Narrowlypouringcastingisthemetalmouldcasting.把金属材料做成所需制品的工艺方法很多，如铸造、锻造、挤压、轧制、拉延、冲压、切削、粉末冶金等等。其中，铸造是最基本、最常用的工艺。Therearemanywaystomakethemetalmaterialsintotherequestedgoods,suchas,casting,forging,extrsion,rolling,madrelling,punching,cutting,powdermetallurgy,ect.A

11、mongthem,castingisthemostbasicandcommontechnology熔化的金属液注入用耐高温材料制作的中空铸型内，冷凝后得到预期形状的制品，这就是铸造。所得到的制品就是铸件Themoltenmetalbeinginjectedintothemediumaltitudemouldmadebyheat-resistingmaterial,thenfreezingtotheshapeasanticipated,thatistheprocessofthecasting.andthefreezingpastsisthecasting.铸造可按铸件的材料分为黑色金属铸造（包括

12、铸铁、铸钢）和有色金属铸造（包括铝合金、铜合金、锌合金、镁合金等）。精密铸件厂专业从事有色金属铸造，重点是铝合金和锌合金铸造。Castingcandividetoblackmetalcasting(incl.Castiron,caststeel)andnonferrousmetals(incl.Aluminiumalloy,copperalloy,zincalloy,magnesiumalloy,ect.).Precisioncastingfactoryarespeciallyengagedinnonferrousmetalcasting,andaluminiumalloyandzincall

13、oyaretheemphasises.按铸型的材料分为砂型铸造和金属型铸造。精密铸件厂对这两种铸造工艺都得心应手，并自行设计、制造这两类铸造模具。Accordingtothematerial,castingcandevidetosandmouldcastingandmetalmouldcasting.Precisioncastingisfacilitywiththetwotypesofcastingsanddesignbythemselvesandproducethetwotypsesmoulds.压力铸造是指金属液在其他外力（不含重力）作用下注入铸型的工艺。广义的压力铸造包括压铸机的压力铸造

14、和真空铸造、低压铸造、离心铸造等；窄义的压力铸造专指压铸机的金属型压力铸造，简称压铸。Pressurecastingispointedthatmoltenmetalrunintothemouldwiththeexternalforce(excl.thegravity).Generizedpressurecastingincludethediecastingmachinecastingandvaccumcasting,lowpressuecasting,centrifugalcasting,ect.Andnarrowlypressurecastingisspeciallypointedtomet

15、aimouldcasitngofthediecastingmachine.Andforshortisdiecasting.6 砂型铸造是一种以砂作为主要造型材料，制作铸型的传统铸造工艺。砂型一般采用重力铸造，有特殊要求时也可采用低压铸造、离心铸造等工艺。砂型铸造的适应性很广，小件、大件，简单件、复杂件，单件、大批量都可采用。砂型铸造用的模具，以前多用木材制作，通称木模。铝合金模具或树脂模具,然价格有所提高，但仍比金属型铸造用的模具便宜得多，在小批量及大件生产中，价格优势尤为突出。此外，砂型比金属型耐火度更高，因而如铜合金和黑色金属等熔点较高的材料也多采用这种工艺。但是，砂型铸造也有一些不足之处

16、：因为每个砂质铸型只能浇注一次，获得铸件后铸型即损坏，必须重新造型，所以砂型铸造的生产效率较低；又因为砂的整体性质软而多孔，所以砂型铸造的铸件尺寸精度较低，表面也较粗糙。不过，精密铸件厂集多年的技术积累，已大大改善了砂型铸件的表面状况，其抛丸后的效果可与金属型铸件媲美。sandmouldcastingisafoundrytechnologythatusingthesandasthematerialofthemouldtomakethemould,andusuallysandcastingusegravitycasting,andsometimesifhavespecialrequirement

17、salsoadoptlowpressuecasting,centrifugalcasting,ect.Sandcastinghaveawideflexibility,produceofsmallsizeparts,largesizeparts,simpleplexone,singleton,masscanalladopt.Sandcasting,previouslysandcastingusethewoodenmould,nowusethealuminumalloymouldorresinmould,thecostofaluminumalloymouldandresinmoldarehight

18、hanwoodenmold,butinthebasssproduce,theadvantageofcoststandout.sandmoldhasabetterrefractonessthanmetalmould.socooperalloyandferrousmetalwhichmettingpointishighusuallyusethistypetechnology,butsandcastinghastheshortage,becausethemouldcanuseonlyonce.,aftercasting,themouldisdamaged.andneedremakethenewmou

19、ld.theproductionefficiencyislow,alsothebulkpropertyofsandissoftandporous,thenthecastingpartshavealowprecisionandsurfaceisrough.afteryearsaccumulationoftechnology,thesurfaceappearancehaveagoodimprovement,andaftershotblastingthesurfaceappearancecomparefavourablywithmetalmouldcasting.7 金属型铸造是用耐热合金钢制作铸造

20、用中空铸型模具的现代工艺。金属型既可采用重力铸造，也可采用压力铸造。金属型的铸型模具能反复多次使用，每浇注一次金属液，就获得一次铸件，寿命很长，生产效率很高。金属型的铸件不但尺寸精度好，表面光洁，而且在浇注相同金属液的情况下，其铸件强度要比砂型的更高，更不容易损坏。因此，在大批量生产有色金属的中、小铸件时，只要铸件材料的熔点不过高，一般都优先选用金属型铸造。但是，金属型铸造也有一些不足之处：因为耐热合金钢和在它上面做出中空型腔的加工都比较昂贵，所以金属型的模具费用不菲，不过总体和压铸模具费用比起来则便宜多了。对小批量生产而言，分摊到每件产品上的模具费用明显过高，一般不易接受。又因为金属型的模具

21、受模具材料尺寸和型腔加工设备、铸造设备能力的限制，所以对特别大的铸件也显得无能为力。因而在小批量及大件生产中，很少使用金属型铸造。此外，金属型模具虽然采用了耐热合金钢，但耐热能力仍有限，一般多用于铝合金、锌合金、镁合金的铸造，在铜合金铸造中已较少应用，而用于黑色金属铸造就更少了。Permanentmetalcastingadopttheheat-resistingsteelalloytomakethecavity.metalmouldcanusegravitycastingandpressurecastingandcanbeusedtimeandagain.everytimepouringca

22、ngotacastingpart,lifeislongandproductionrateishigh.thecastingprodecedbymetalmouldnotonlythedimentionalaccuracyishighandsurfaceappearanceisgoodbutalsocangotahigherintensitythanthesandcastingwiththesamemoltenmetalandnoteasytobedamaged.Metalmouldcastingalsohavesomeshortages:thepriceofheat-resistingstee

23、lalloyandcavitymakingishigh.sothemouldcostishigh,.Itisnotcheaptouseonthesmallbulkproduction.anditisnotavailableforthetoolargesizeparts.soitisnotusewidelyinthelimitedquantitiesorlargesizepartsproduction.inaddition,theheat-resistingislimitedofthesteelalloy.sometalcastingisonlyusedinaluminiumalloy,zinc

24、alloy,magnesiumalloynotincooperalloycasting,itisstilllessinferrouscasting.8压铸是在压铸机上进行的金属型压力铸造，是目前生产效率最高的铸造工艺。压铸机分为热室压铸机和冷室压铸机两类。热室压铸机自动化程度高，材料损耗少，生产效率比冷室压铸机更高，但受机件耐热能力的制约，目前还只能用于锌合金、镁合金等低熔点材料的铸件生产。当今广泛使用的铝合金压铸件，由于熔点较高，只能在冷室压铸机上生产。压铸的主要特点是金属液在高压、高速下充填型腔，并在高压下成形、凝固，压铸件的不足之处是：因为金属液在高压、高速下充填型腔的过程中，不可避免地

25、把型腔中的空气夹裹在铸件内部，形成皮下气孔，所以铝合金压铸件不宜热处理，锌合金压铸件不宜表面喷塑（但可喷漆）。否则，铸件内部气孔在作上述处理加热时，将遇热膨胀而致使铸件变形或鼓泡。此外，压铸件的机械切削加工余量也应取得小一些，一般在0.5mm左右，既可减轻铸件重量、减少切削加工量以降低成本，又可避免穿透表面致密层，露出皮下气孔，造成工件报废.Diecastingisonthediecastingmachinewithmetalmould,isthehighestproductionrateincastingindustyatpresent.diecastingmachinedividetoho

26、tchamberdiecastingmachineandcoldchamberdiecastingmachine.hotchamberdiecastingmachineautomationoshighandmaterialwastageissmall.productionefficiencyishighcoldchambermahines.butduetothemachinepartsheat-resisitingislimited.,socanonlybewidelyusedinamuminumalloycastingandmagnesiumcastingwithlow-meltingpoi

27、nt.,atpresentthemeltingpointofaluminiumalloyisalittlehighsocanonlyproduceoncoldchamperdiecasingmachine.,Thecharactericsofdiecastingisthatmoltenmetalfullthecavitywithhighpressueandhighspeedthensolidificationandshapeunderhighpressure.theshortageofdiecasting.:whenmoltenmetalfullthecavitywithhighpressue

28、andspeed,itisunavoidtowraptheairinthecavitythenoccurporosityundertheskin.soaluminumalloycanotgotheattreatment.andzincalloycannotpowdercastingbutcanpainting,.otherwise,theinternalpoosityofthecastingwillthermaldilationwhenmeettheheatthenmadethecastingpartstransformationorbubble.andthenallowanceofthemeachanicalcuttingandmachiningshouldbesmall.usually in 0.05mm.Itnotonlycanreducetheweightofthecastingpartsandmachiningallowancecost,butalsocanavoidthesurfacestratumcompatumwithmakingtheporosityoutsidetomaketheworkpiecediscardasuseness.专心-专注-专业