CastingDr. Young-Bin ParkDepartment of Industrial and Manufacturing EngineeringFAMU-FSU College of EngineeringFall 2006EIN 3390C/4390C Manufacturing Processes and Materials Engineering1Metals Processed by CastingSand casting –60%Investment casting –7%Die casting –6%Permanent mold casting –11%Centrifugal casting –7%Shell mold casting –6%Source: Jonathan Colton, Georgia TechEIN 3390C/4390C Manufacturing Processes and Materials Engineering2EIN 3390C/4390C Manufacturing Processes and Materials Engineering 3Examples of Cast Products Transmission valve body Hub rotor with disk-brake cylinderTransmission housing EIN 3390C/4390C Manufacturing Processes and Materials Engineering4Examples of Cast Products Polaroid PDC-2000 digital camerawith a AZ191D die-cast, high-puritymagnesium case Two piece Polaroid camera case made by hot-chamber die-casting processExpendable Mold CastingSand castingShell moldingLost-foam castingInvestment castingVacuum castingEIN 3390C/4390C Manufacturing Processes and Materials Engineering5Sand MoldEIN 3390C/4390C Manufacturing Processes and Materials Engineering6Sand CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering7PatternEIN 3390C/4390C Manufacturing Processes and Materials Engineering8EIN 3390C/4390C Manufacturing Processes and Materials Engineering 9CoreInserts made from sand and used to form internal cavities or passages. Placed in the mold cavity to form the interior surfaces of the casting.Chaplet : Metal support used to anchor the core in placeEIN 3390C/4390C Manufacturing Processes and Materials Engineering 10Shell MoldingExpendable-Pattern (Lost-Foam) CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering11Investment Casting (Lost-Wax) EIN 3390C/4390C Manufacturing Processes and Materials Engineering12Investment Casting(a) Wax pattern assembly(b) Ceramic shell around wax pattern(c) Wax is melted out and the mold is filled with molten superalloy(d) Cast rotor produced to net or near-net shapeEIN 3390C/4390C Manufacturing Processes and Materials Engineering13 Investment CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering14EIN 3390C/4390C Manufacturing Processes and Materials Engineering 15Investment CastingAdvantages –Complex shape –Good surface finish (R a = 1-2 microns)–Close dimensional tolerances –Suitable for high melting point alloysDisadvantages –Labor intensive–CostlyApplications–Gears, cams, valves, jewelryEIN 3390C/4390C Manufacturing Processes and Materials Engineering16Vacuum CastingA mixture of fine sand and urethane is molded over metal dies and cured with amine vapor.The mold is partially immersed into molten metal.The vacuum draws the molten metal into the mold cavities. Suitable for thin-walled complex shapes with uniform propertiesEIN 3390C/4390C Manufacturing Processes and Materials Engineering 17Permanent Mold Casting EIN 3390C/4390C Manufacturing Processes and Materials Engineering 18Permanent Mold CastingAdvantages:–Reusable mold that maintains strength at hightemperature (typically made from a metal such ascast iron, steels, ceramics, refractory metal alloys)–Superior heat conduction•Higher cooling rate•Finer grain size•Better part strength–Mold cavity and gating systems are integral partsof the mold–Good dimensional stability–Good surface finish (R a = up to 1-2 microns)–Easier to automate (higher production volume)EIN 3390C/4390C Manufacturing Processes and Materials Engineering 19Permanent Mold CastingDisadvantages:–Suitable for casting low melting point metals, e.g., Al, Mg, Zn, Cu, etc.–More prone to hot tears (due to lower deformation strength of metal dies)–Not suitable for intricate shapes–Thermal gradient across the mold is critical.–Thermal shock needs to be prevented, as it may lead to thermal fatigue and failure.–Measures for thermal shock:•Preheat mold.•Provide cooling channels where the characteristic thickness is large.EIN 3390C/4390C Manufacturing Processes and Materials Engineering 20Permanent Mold CastingProcess parameters–Clamping force–Injection pressure–Die size and capabilityApplications–For making nonferrous metal parts of relatively intricate shapes for mass production (Ferrous metals can also be cast.)Again, thermal balance in the mold is critical.EIN 3390C/4390C Manufacturing Processes and Materials Engineering 21Hot-Chamber Die CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering 22Hot-Chamber Die CastingFor casting low melting point metals, e.g., zinc, tin, lead, etc.Average injection pressure = 15 MPa (can be as high as 35 MPa)High production rates, e.g., 900 parts/hr for Zn parts, 18,000 parts/hr for zipper teethSimilar to injection molding of plasticsEIN 3390C/4390C Manufacturing Processes and Materials Engineering 23Cold-Chamber Die CastingNo furnace 20-70 MPaFor casting highmelting point metals, e.g., Al, Mg, CuEIN 3390C/4390C Manufacturing Processes and Materials Engineering 24Cold-Chamber Die CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering25Centrifugal CastingSide viewUses the inertial forces caused by rotation to distribute the molten metal into the mold cavitiesHollow cylindrical parts (pipes, gun barrels), axisymmetric parts (wheel with spokes)EIN 3390C/4390C Manufacturing Processes and Materials Engineering 26Centrifugal CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering 27Centrifugal CastingEIN 3390C/4390C Manufacturing Processes and Materials Engineering 28Squeeze CastingSolidification of molten metal under high pressure combination of casting and forgingApplied pressure is between die casting and forgingEIN 3390C/4390C Manufacturing Processes and Materials Engineering29Casting Turbine BladesDirectional solidificationProduction of single crystal bladeProduction of blades with longitudinal grain boundariesEIN 3390C/4390C Manufacturing Processes and Materials Engineering 30Casting Design RulesEIN 3390C/4390C Manufacturing Processes and Materials Engineering 31Casting Design RulesUniform cross-sections (or thickness) and smooth, gradual transitionsAvoid sharp corners to reduce stress concentrationEIN 3390C/4390C Manufacturing Processes and Materials Engineering 32Casting Design RulesFlats–Avoid large flats, which may potentially lead towarpage and surface nonuniformities–Break up with ribs and serrationsShrinkage–Design patterns with shrinkage allowance, i.e. usesmaller patterns–Range:•Aluminum: 1.3%•Ferrous metal: 0.8-2.0%•Aluminum-bronze: 2.1%EIN 3390C/4390C Manufacturing Processes and Materials Engineering33Casting Design RulesParting lines–Design along flat planes–Corner/edge incorporation–Reduce core usageEIN 3390C/4390C Manufacturing Processes and Materials Engineering34EIN 3390C/4390C Manufacturing Processes and Materials Engineering35Casting Design RulesDraft angles–Necessary for pattern or part removal in permanent mold casting–Range: 0.5-2 degrees –Influences tolerancesTolerances–Production cost increases as tolerance decreases –Sand casting: 1/32”-1/16”on 12”surface –Shell molding:•0.020”for steel •0.015”for cast iron •0.003”best achievable–Include machining allowances, if necessaryEIN 3390C/4390C Manufacturing Processes and Materials Engineering36ExamplesChill(X)(O)(X)(O)(X)(O)(X)Too sharpToo roundDraft anglesGradual thickness change2. Bad for core placementShrinkage cavityEIN 3390C/4390C Manufacturing Processes and Materials Engineering37Examples(X)(O)Uniform thickness for uniform cooling and shrinkage prevention(X)(O)Inclination is better for porosity and residual stress prevention.(X)(O)Continuous core is better.EIN 3390C/4390C Manufacturing Processes and Materials Engineering 38Examples(X)(O)Uniform thicknessUniform thicknessExamplesEdge reinforcement(X)(O)Uniform thickness is required (ribs). EIN 3390C/4390C Manufacturing Processes and Materials Engineering39Modeling and SimulationEIN 3390C/4390C Manufacturing Processes and Materials Engineering40Directional SolidificationEIN 3390C/4390C Manufacturing Processes and Materials Engineering41SimulationEIN 3390C/4390C Manufacturing Processes and Materials Engineering42SimulationEIN 3390C/4390C Manufacturing Processes and Materials Engineering43SimulationEIN 3390C/4390C Manufacturing Processes and Materials Engineering44。