Engineering Materials Chapter 10: Fundamentals of metal casting

Solidification shrinkage in casting is defined as which one of the following?

Contraction during the phase change from liquid to solid

The upper half of a sand-casting mold is called which of the following?

Cope

Any internal surfaces of a casting are determined during the casting process by means of which of the following?

Core

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

Relative to the dimensions of the casting, the pattern that determines the geometry of the casting in expendable mold processes is usually made oversized, the same size, or undersized?

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

The shrinkage cavity that occurs in some castings resulting from restrictions in the amount of molten metal available to feed those cavities is called which one of the following by foundrymen?

Pipe

According to the empirical relationship in the previous question, total solidification time is proportional to which one of the following quantities, where A = surface area of casting, Hf = heat of fusion, Tm = melting temperature, and V = volume of casting?

(V/A)^2

A casting has a volume = 80 cm^3, surface area = 160 cm^2, and total solidification time = 1.5 min. The riser to be used in the mold for this casting has a V/A ratio = 0.7. The total solidification time of the riser is the closest to which one of the following?

3 minutes

The unit energy for melting and pouring a certain casting metal = 1000 J/g, its density = 5.0 g/cm^3, and the volume of the casting = 600 cm^3 including riser and gating system. The total heat required to raise the temperature of the metal to the pouring temperature is closest to which one of the following?

3000 kJ

In casting processes, a runner is which one of the following?

A channel in the mold leading from the downsprue to the main mold cavity

Two important relationships that determine the flow of molten metal in casting are which of the following?

Bernoulli's theorem, and continuity law

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?

Blind riser, and side riser

In casting, a flask is which one of the following?

Box which holds the cope and drag

Solidification shrinkage occurs in all metals with the exception of which one of the following?

Cast iron with high carbon content

The empirical relationship that determines total solidification time in casting is known as which one of the following?

Chvorinov's rule

Sand casting is which of the following types of casting processes?

Expendable mold

Casting is only suited to ferrous metals such as cast iron. True or False?

False

The volume of the riser must always be greater than the volume of the casting in order to avoid premature solidification of the riser. True or False?

False

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, and why?

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

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 or False, and why?

False. The regions most distant from the liquid metal supply must freeze first to maintain the supply of molten metal to the remaining parts of the casting.

The spiral mold test is a test for which one of the following properties of the casting metal?

Fluidity

A factory that performs casting operations is called which of the following?

Foundry

Relative to the V/A ratio of the casting itself, the V/A ratio of the riser should be equal, greater, or smaller?

Greater

Turbulence during pouring of the molten metal is undesirable for which two of the following reasons?

It increases erosion of the mold surfaces, and it increases the formation of metallic oxides that can become entrapped during solidification

A riser in casting is described by which three of the following?

Metal that is not part of the casting, source of molten metal to feed the casting and compensate for shrinkage during solidification, and waste metal that is usually recycled.

Shrink rules used to achieve the desired dimensions of patterns and molds have graduated scales that are __________?

Slightly elongated

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

Total solidification time is described as which one of the following?

Time between pouring and complete solidification.

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

A riser in a sand casting mold is a reservoir in the mold that serves as a source of liquid metal to compensate for shrinkage of the casting during solidification. True or False?

True

Casting is a shaping 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