Chapter 10- MAE 183 A
A riser in casting is described by which three of the following:
source of molten metal to feed the casting and compensate for shrinkage during solidification
Heating a metal from room temperature to pouring temperature in a casting operation depends on all of the following properties except which one:
thermal expansion
10.13 Total solidification time is defined as which one of the following:
time between pouring and complete solidification
Casting is a process in which molten metal flows into a mold where it solidifies in the shape of the mold cavity; the term casting also applies to the part that is made by this process: true or false?
true
10.17 According to the empirical relationship in the previous question, total solidification time is proportional to which one of the following quantities:
(V/A)2; where A = surface area of casting, Hf = heat of fusion, Tm = melting temperature, and V = volume of casting
Two important relationships that determine the flow of molten metal in casting are which of the following:
Bernoulli's theorem, Chvorinov's rule
10.16 The empirical relationship that determines total solidification time in casting is known as which one of the following:
Chvorinov's rule
10.15 A eutectic alloy is a particular composition in an alloy system for which the solidus and liquidus are at the same temperature: True or false
True
10.20 To minimize the damaging effects of shrinkage, it is desirable for the regions of the casting most distant from the liquid metal supply to freeze last: True (b) false
True
Which of the following metals would typically be used in die casting (three best answers): (a) aluminum, (b) cast iron, (c) steel, (d) tin, (e) tungsten, and (f) zinc?
aluminum,zinc
In casting, a flask is which one of the following:
box which holds the cope and drag
In casting processes, a runner is which one of the following:
channel in the mold leading from the downsprue to the main mold cavity
The upper half of a sand‐casting mold is called which one of the following:
cope
Sand casting is which of the following types of casting process
expendable mold
10.14 During solidification of an alloy when a mixture of solid and liquid metals is present, the solid‑liquid mixture is referred to as which one of the following:
mushy zone
During solidification of an alloy when a mixture of solid and liquid metals is present, the solid-liquid mixture is referred to as which one of the following:
mushy zone
10.18 Solidification shrinkage in casting is defined as which one of the following: (a) liquid contraction during cooling prior to solidification(b) liquid contraction during cooling and solidification(c) contraction during the phase change from liquid to solid(d) thermal contraction of the solidified casting during cooling to room temperature.
contraction during the phase change from liquid to solid
Any internal surfaces of a casting are determined during the casting process by means of which one of the following:
core
Metal inserts in the walls of a sand mold cavity designed to remove heat from the molten metal more rapidly than the surrounding sand are called:
external chills
In hot-chamber die-casting machines, molten metal is poured into an unheated chamber from an external melting container, and a piston is used to inject the metal under high pressure into the die cavity: true or false?
false
10.21 The passageway between the riser and the main cavity must have a small cross‐sectional area to minimize waste of casting metal: True or false
false Although it is desirable to minimize waste of casting metal, the cross-section area of the passageway must be large enough to avoid premature freezing.
A factory that performs casting operations is called which one of the following:
foundry
10.23 Relative to the V/A ratio of the casting itself, the V/A ratio of the riser should be
greater
Which of the following qualifies as a precision-casting process (two correct answers):
investment casting, plaster-mold casting
( 2 answers) Turbulence during pouring of the molten metal is undesirable for which of the following reasons (two best answers):
it increases erosion of the mold surfaces, it increases the formation of metallic oxides that can become entrapped during solidification,
10.11 Turbulence during pouring of the molten metal is undesirable for which two of the following reasons:
it increases the formation of metallic oxides that can become entrapped during solidification, it increases erosion of the mold surfaces
A misrun is which one of the following defects in casting: (a) globules of metal becoming entrapped in the casting, (b) metal is not properly poured into the downsprue, (c) metal solidifies before filling the cavity, (d) microporosity, and (e) "pipe" formation?
metal solidifies before filling the cavity,
A riser in casting is described by which of the following (three correct answers): (a) an insert in the casting that inhibits buoyancy of the core, (b) gating system in which the sprue feeds directly into the cavity, (c) metal that is not part of the casting, (d) source of molten metal to feed the casting and compensate for shrinkage during solidification, and (e) waste metal that is usually recycled?
metal that is not part of the casting, source of molten metal to feed the casting and compensate for shrinkage during solidification, and (e) waste metal that is usually recycled?
The pattern that determines the geometry of the casting in expendable mold processes is usually made
oversized
To allow for shrinkage that occurs in the metal during solidification and shrinkage, the size of the mold cavity must be made which of the following:
oversized
An irregularity in the surface of the casting caused by erosion of the sand during pouring is called which one of the following sand casting defects:
sand wash
Which two of the following riser types are completely enclosed within the sand mold and connected to the main cavity by a channel to feed the molten metal:
side riser
10.19 Shrink rules used to achieve the desired dimensions of patterns and molds have graduated scales that are
slightly elongated