MCHE 3920 REVIEW QUESTIONS WITH VERIFIED ANSWERS LATEST UPDATE 2024

MCHE 3920 REVIEW QUESTIONS WITH VERIFIED ANSWERS LATEST UPDATE 2024 Material properties of casts - Answers high stiffness and strength even at elevated temperatures The oldest metal castings date back to - Answers 5000 BCE Three main benefits of casting - Answers form freedom, strength, and character Cavity that defines the negative shape of the product - Answers mold Pouring "top down" leads to - Answers oxidation and loss of material properties, especially ductility An advantage for pouring "bottom up" is - Answers air inside the mold or vapors released during casting can evacuate more easily Is it better to have a metal with high or low viscosity for complex molds? - Answers low Adding carbon to steel has what benefits for casting? - Answers lower melting temperature, viscosity, and shrinkage The ratio of a mixture where viscosity and melting point reach the minimum - Answers Eutectic Composition Castings have a much _____ alloy content than the typical compositions of wrought alloys - Answers higher Higher alloy content reduces what mechanical properties? - Answers toughness., ductility, and fatigue strength Why are lower filling speeds (laminar flow) preferred for casting? - Answers Minimum free surface area (oxidation) Flow speeds for casting are laminar below ___ m/s and turbulent above __ m/s - Answers .5, 1 When metal solidifies before a mold is fully filled - Answers cold running What are ways to prevent cold running? - Answers Filling from multiple gates, increasing thickness What is a downside of filling from multiple gates? - Answers More finishing required What is a downside of increasing thickness when casting? - Answers Adds weight and cost Filling a cast quickly at high pressures has what tradeoff? - Answers Poorer material properties A metal mold for casting - Answers Die The inlet channels of casting die - Answers runners The outlet channels of a casting die - Answers risers Pour weight of a cast should be ____% or more of the weight of the casting itself - Answers 40 Minimizing surplus in pouring in casting by mold design - Answers Methoding ratio of volume to surface area (casting) - Answers Thermal modulus Chvorinov's Rule applies well to relatively _____ castings because the volume of material involved determines the speed of solidification - Answers large For thin-walled castings (less then 4mm thick), Chvorinov's Rule strongly _____________ the solidification time - Answers underestimates Three main quality issues in casting of metals - Answers porosity formation, internal stresses, distortion Porosity increases when percent shrinkage ________ - Answers increases What causes internal stresses in casting? - Answers Temperature differences during cooling for thick and thin sections If the temperature stresses in casting exceed ________, we get deformation or internal stresses based on the surrounding mold - Answers yield stress What categories of alloying elements are found in casting metals? - Answers improve processability, properties, impurities For a given casting alloy, a ______ casting will have poorer properties than a _______ one - Answers big, small High melting point powders added before pouring a casting - Answers innoculants What are the positives of sand casting? - Answers Can deal with all common casting metals, cheap, wide range of sizes What are the negatives of sand casting? - Answers fragile, low filling speeds and pressures, poor conductors of heat, qualities, tolerances. Lower mold half in a sand mold - Answers Drag Higher mold half in a sand mold - Answers Cope Hollow products can be casted using _________ - Answers sand cores Downward channel in a sand mold - Answers sprue The feeder is located where on a sand cast? - Answers highest point in thickest part Atmospheric pressure steel die casting is called _______ - Answers Gravity die casting Advantages of gravity die casting are ___________ - Answers good tolerances, short cycle times, no machining required Disadvantages of gravity die casting include __________ - Answers low fill speed, limited size and weight, only Al and MG Low pressure (2 to 5 bar) steel die casting is called - Answers low pressure die casting Advantages of low-pressure die casting - Answers fine details, high quality from laminar flow Which metals can be low-pressure die cast? - Answers Mg, Al What is usually made from low-pressure die casting? - Answers alloy wheels High pressure (2000 bar) steel die casting is called - Answers High pressure die casting Disadvantages of high pressure die casting - Answers expensive, cannot use sand cores, poor quality What metals can be high-pressure die cast? - Answers Zn, Al, Mg Advantages of high-pressure die casting? - Answers thinner products, fast cooling, short cycle times, no processing, high tolerances In investment casting, _____ is used to produce a pattern - Answers wax Sheet metal forming has ____ production volume - Answers high Design process is iterative and involves continual tradeoffs between ___________ - Answers function, quality, cost Casting: Cooling from liquid to solid is accompanied by ________ in volume - Answers Reduction Casting: Rate of volume reduction is __________ in solidification range - Answers highest Energy from Tpouring to Tsolidus - Answers Specific heat, liquid phase Energy from Liquid to solid phase transition - Answers Latent heat of solidification Energy from Tsolidus to RT - Answers Specific heat, solid phase How to account for casting shrinkage that occurs after solidification? - Answers bigger mold, 1-2%