制造技术(中英文课件)

patterns

（模样）MouldingSand（型砂）Lesson4Review背砂冒口冷铁直浇口横浇道型芯上砂箱下砂箱中砂箱BackingsandRiserChillSprueRunnerCoreCope-uppermouldingflaskDrag-lowermouldingflaskCheek-intermediate

mouldingflaskPatternsmaterialspatternmaterials:（模样材料）theusualpatternmaterialsarewood,metalandplasticsThemostcommonlyusedDisadvantages:absorptionofmoisture（吸水）distortions（变形）、dimensionalchanges（尺寸变化）

Advantages:theeasyavailability（易于使用）,thelowweight（轻）,easilyshaped（易于成型）,relativelycheap（价格便宜）

(1)woodVarietiesofwood:pine(松树),mahogany(桃花心木),teak(柚木),walnut(胡桃木),deodar(喜马拉雅雪杉),plywoodboard(胶合板),particleboard(刨花板)Patternsmaterials(2)Metalpatterns:usedforlargescalecastingproductionMaterials:castiron,brass（黄铜）,aluminum,whitemetal(3)plastics:lowweight,easierformability（可成形性好）,smoothsurface（光滑表面）,durability（耐久力）,dimensionallystable（尺寸稳定）andcleanedeasily（易于清洁）patterns

numberofcastingsproducedbeforepatternequipmentrepairPatternmaterialPatternCore

Smallcastings20002000Hardwood(under600mm)60006000Aluminium,plastic100,000100,000CastironMediumcastings(600-1,800mm)1000750Hardwood30003000Aluminium,plasticLargecasting(above1,800mm)200150Softwood500500HardwoodmetalreinforcedTypeofPatternsTypeofpatterns(模样的类型)Singlepiecepattern（单块模）:（2）Splitpatternortwopiecepattern（分块模）TypeofPatterns（3）Gatedpattern（浇口模）wherethegatingandrunnersystemareintegralwiththepattern.(浇口和浇道系统与模样合为一体）（4）Copeanddragpattern

（两箱造型模）TypeofPatterns（5）Loosepiecepattern（活块模）：isusedwhenwithdrawingthepatternfromthemouldisnotpossible.（6）Followboardpattern（成型底板造型）TypeofPatterns（6）Sweeppattern（刮板模）:usedtosweepthecompletecastingbymeansofaplanesweep(平面扫描）.Thisreducesthecostofthreedimensionalpattern.（7）Skeletonpattern（骨架模）:madeofstripsofwood,isusefulgenerallyforverylargecasting.TypeofPatternsPatterncolourcode(模样的颜色代码)Redororangeonsurfacesnottobefinishedandleftascast;Yellowonsurfacestobemachined;Blackoncoreprintsforunmachinedopenings.Yellowstripesonblackoncoreprintsformachinedopenings.Greenonseatsofandforloosepiecesandloosecoreprints.Diagonalblackstripswithclearvarnishontostrengthentheweakpatternsorshortenacasting.PatternscolourcodeMouldingmaterialsareusedinmanufacturingmouldsandcores:Mouldingsand

(型砂)Systemsand

(系统砂)Rebondedsand(加粘土回用砂)Facingsand(面砂):Thissandisusednexttothepatterntoobtaincleanerandsmoothersurfaces.Seacoal（煤粉）SlowlyburnReducinggases(还原性气体）CreateasmallgaspressureMoltenmetalispreventedfromenteringintothesilicagrains.MouldingSandPartlingsand(分型砂)：sprinkled(喷洒）onthepatternandtothepartingsurfacesofthemouldhalves.WashedsilicagrainsPreventtheadherenceofthemouldingsandThishelpsineasywithdrawalofthepatternandeasierseparationofthecopeanddragflasksatpartingsurface.Backingsand(背砂，填充砂)：itiscontainstheburntfacingsand,mouldingsandandclay.Themouldingflaskiscompletelyfilledwithbackingsand.MouldingSandThechoicofmouldingmaterialsisbasedontheirprocessingproperties:(根据工艺性能选择造型材料)Refractoriness(耐火性能):itistheabilityofthemouldingmaterials

towithstand(抵抗)thehightemperatureofthemoltenmetalsothatitdoesnotcausefusion.MouldingSandGreenstrength(湿强度):the

mouldingsandthatcontainsmoistureistermdasgreensand.Thegreensandshouldhaveenoughstrengthsothattheconstructedmouldretainsitsshape.Drystrength(干强度):whenthe

moistureinthemouldingsandiscompletelyexpelled（排出）,calleddrysand.①retainthemouldcavity(保持型腔）②withstandthemetallostaticforces（抵抗金属重力作用）Hotstrength(热强性):Afterallthemoistureiseliminated,thesandwouldreachahightemperaturewhenthemetalinthemouldisstillintheliquidstate.holdtheshapeofmouldcavity.(保持型腔的形状）Permeability(透气性):Duringthesolidificationofacasting,largeamountsofgasesaretobeexpelledfromthemould.Thisgasevolutioncapabilityofthemouldingsand.（是气体逸出的能力）MouldingSandMouldingsandcompositionSilicasand(含硅砂):itisthemajorportionofthemouldingsand(upto96%)Therest:alumina(Al2O3),Sodium(Na2O+K2O),magnesiumoxide(MgO+CaO)(about2%)Mainsource:riversandFusionpoint（熔点）:1450℃forCastiron;1550℃for

steels.Zirconsand(含锆砂):itisazirconiumsilicate(ZrSiO4).Thetypicalcomposition:ZrO2–66.25%,SiO2–30.96%,Al2O3-1.92%,Fe2O3-0.74%Fusionpoint:2400℃.Veryexpensive,lowcoefficientofthermalexpansion,highthermalconductivity,highchillingpower,highdensity.Usedtoprecisioninvestmentcasting.MouldingSandChromitesand(含铬砂):Thetypicalcomposition:Cr2O3–44%,Fe2O3-28%,SiO2–2.5%,CaO-0.5%,Al2O3+MgO-25%,Fusionpoint:1800℃.Itisusedtomanufactureheavysteelcastings.(e.g.austeniticmanganesesteelcastings)Olivinesand(橄榄石砂):Thetypicalcomposition:fosterite(Mg2SiO4）,fayalite(Fe2SiO4)Itcanbeusedforarangeofsteels.MouldingSandMouldingSandClay(粘土):bindingagents(粘结剂）Themostpopularclaytypesare:Kaolinite（高岭石）orfireclay（耐火泥）andbentonite（膨润土）Al2O32SiO22H2OAl2O34SiO2

H2OnH2O(1)Kaolinite:（高岭石）meltingpoint:1750℃to1787℃.(2)bentonite:（膨润土）meltingpoint:1250℃to1300℃.absorbmorewaterTherearetwotypesofbentoniteWesternbentonite(钠基膨润土）:withsodiumasadsorbedion.Betterswellingproperties(较好的膨胀性）Southernbentonite(钙基膨润土）：withcalciumionMouldingSandTherest:lime(石灰），alkalies(碱）andotheroxides.Water:clayisactivatedbywater,itdevelopsthenecessaryplasticity(可塑性）andstrength（强度）.Thenormalpercentagesofwater:from2to8.ComparativepropertiesofmouldingsandswithvariousclaysMouldingSand2.TestingsandpropertiesMoisturecontent(（水含量）Samplepreparation:asampleofthestandard（标准试样）.e.g.(1)Sampleof50gIsdried105℃to110℃(2h)Thesampleisweighed(2)Moistureteller（水分测定仪）:utilisecalciumcarbide(碳化钙）

CaC2+2H2OC2H2+Ca(OH)2Acetylene（乙炔）claycontent（粘土含量）Samplepreparation:asampleofthestandard（标准试样）.e.g.(1)Sampleof50gIsdried105℃to110℃(2h)Thedriedsample475mldistilledwater25mlNaOHMouldingSandSandgrainsize（砂粒尺寸）采用筛分法测定Asandsamplewhichisdevoid(全无）ofmoistureandclay

Placedonthetopsieve(筛）ofasieveshaker（振筛机）withgraduallydecreasingmeshsizes(网格尺寸）ASTM（标准)（筛号）MESHINGOPENING(筛孔尺寸）/mm61220301002003.3271.6510.8330.5890.1470.074MouldingSandSandgrainsizedistribution(筛孔号）GrainFinenessNumber(GFN平均粒度)GFN=∑Minfi∑fiMi=第i级筛的相乘因素fi=第i级筛的剩余量MouldingSandPermeability（透气性）Astandardpermeabilitytestistomeasu