ME 2653 Review for test 1

The term "green compact" refers to a P/M part:

after compaction but before sintering

This is NOT classified as a family of materials in engineering:

alloys

The parts produced by Powder metallurgy

are of high dimensional accuracy

example of ceramic materials

cements

In the following figure, which casting process is schematically represented?

centrifugal casting

Which of the following processes use a rotating mold to complete the casting solidification?

centrifugal casting

This segment of the gating system has the smallest cross-section area and controls the flow of molten metal

choke

The P/M step in which we try to produce uniform high density in the part is:

compacting

This step in P/M processing is used to impart sufficient strength to permit handling and transportation, but does not produce the final density and final strength.

compacting

Powder metallurgy is a ___ manufacturing process.

consolidation

When a hot solid (like a just-cast casting) cools to room temperature, it will generally

contract(shrink)

The top segment of a mold, pattern, or flask

cope

This solid shape is inserted into a mold to produce a hole or internal cavity

core

These projections on a pattern create additional cavities in a mold that are used to locate and anchor cores. Both the projections and the created cavities are called ___.

core print

Which of the following processes is limited to non-ferrous metals:

die casting

When a squeeze is applied, the greatest compaction is observed (check reference book before answer):

directly beneath the squeeze head

This vertical portion of a gating system conducts metal down to the mold cavity

down sprue

This taper is incorporated into patterns to permit withdrawal from a sand mold

draft

The bottom half of a mold, pattern or flask

drag

the bottom half of a mold, pattern, or flask

drag

example of polymer material

epoxies

In permanent-mold casting, the metal mold does not need to be preheated before pouring

false

One of the disadvantages to use Permanent-mold casting is that you cannot insert cores in the molding.

false

This open box surrounds the upper and lower segments of a sand mold

flask

This is NOT a typical process of the casting family:

forging

What kind of defects could dissolved gases generate in the final piece during casting?

gas porosity

The total "plumbing system" that conveys liquid metal from the outside of the mold to the mold cavity

gating system

one of the first metals used by man

gold

The process below that would produce the weakest cores would be:

green sand

Surface cracking of die casting dies at low cycle count caused by extreme rates of surface temperature change is called (check reference book before answer!)

heat checking

The defect which can occur in a casting if the mold design applies too much constraint during the solidification process (check reference book before answer):

hot tears

Which of the following effects of increased superheat is considered to be a positive change?

increased fluidity

The strength of a P/M part increases as the density ___.

increases

These small openings connect runners to mold cavities

ingate

A material that is added to the mold to slow the cooling of a riser is (check reference book before answer):

insulation sleeve

Which casting process cannot be used if you want to cast many parts using the same mold?

investment casting

Which of the following processes requires a pattern for each piece?

investment casting

When graphite is used as a lubricant in P/M:

it usually remains in the material, providing carbon as an alloy element

example of composite material

kevlar- frp

One of the disadvantages of the centrifugal casting process can be:

limited shapes

The main difference between permanent-mold and die casting is that (in) die casting:

liquid metal is not pouring by gravity

One alternate name sometimes used for investment casting is

lost wax

Machining processes, such as lathe turning, drilling and milling, would be classified in this group of manufacturing processes:

material removal

In atomization,

molten metal is forced through a small orifice and broken up by a stream of compressed air

Compared to other molding sands such as zircon, foundry silica sand is ___ to produce "burn-on" defects.

more likely

This is the simplest and cheapest type of pattern, often used when producing small quantities of a part.

one-piece pattern

The interface between the cope and drag segments of a mold, pattern, flask or core.

parting line

The mold cavity is often formed by packing mold material around this shaped block that resembles the part to be produced

pattern

When liquid metal flows between the sand grains, this defect is produced, resulting in a metal/sand mix adhering to the surface of a casting.

penetration

Which casting process would have the lowest cost for a very high production quantity

permanent mold

This part of the gating system first receives the stream of molten metal

pouring cup

In order to insure fill of thin sections during investment casting one might

preheat the mold before pouring

This additional reservoir of liquid metal is positioned inside a mold to compensate for solidification shrinkage

riser

These features may be incorporated into a gating system to help prevent contaminated metal from entering the mold cavity

runner extensions and walls

It typically has the highest metal-mold ratio (check reference book before answer):

shell

This compaction process is used in P/M with relatively thin, single thickness, products.

single action pressing

Which of the following tool is most likely manufactured by powder metallurgy?

sintered carbides

In P/M, a protective atmosphere is generally required during this operation:

sintering

this polymer was commonly used in old times

skins

What could be an advantage of using Shell molding when comparing with regular sand casting?

smoother surfaces

material developed after the iron age

steels

why specific atmospheres are used during the sintering of the PM part?

to protect from oxidation

One of the disadvantages of Sand casting is that their products could have a rough finishing surface

true

Powder metallurgy can effectively combine immiscible materials as well as metals and ceramics.

true

In order to nucleate a solid phase from the liquid, the temperature must decrease to below the equilibrium melting point. This is called

undercooling

What is the least expensive pattern material for sand molding processes? This is typically used for low production quantities (10pcs to 20,000)

wood

Which alloy group might be cast with hot chamber die casting

zinc alloys

According to the Fe-C diagram, where is the eutectic point located?

1147 degrees C

Because of the clay and water binder, the green sand you used in lab would have to be used within about ___ from the time of mixing (i.e. its bench life).

2-3 hours

what is the ideal temperature for sintering steel alloys?

2000 degrees F

A graphite insert inside the casting part that is used to increase the heat flow locally is called (check reference book before answer):

A internal chill

The "chill zone" of a cast structure is

A layer of fine equiaxed crystals at the casting surface next to the mold wall

In general, what is a shell in casting processes?

A mold made from sand and resin

Mixing or blending in P/M is performed to:

Add lubricants Combine different chemistry materials All of the options Combine different sizes and shaped powders

Green compressive strength measures the strength of mold material (check reference book before answer):

After compaction but before the pour

For casting surfaces to be finished by machining operations

An additional layer of stock is added to the casting design to insure machining clean up

Which type of alloy would be more difficult to cast without shrinkage defects (check reference book before answer!):

An alloy with a long freezing range

The most common technique of powder manufacture is known as:

Atomization

Which of the following is NOT a true statement about the casting process? (See your textbook)

Cast products must be entirely solid. They cannot contain hollow sections or internal cavities.

The top segment of a mold, pattern, or flask

Cope

This solid shape is inserted into a mold to produce a hole or internal cavity

Core

The two main subgroups of casting processes are:

Expendable mold and multiple-use mold

Repressing after sintering can be performed with the same dies used for compaction.

False

Why might the mechanical properties of a permanent mold casting be higher than a sand mold casting?

Fine grain size due to more rapid solidification

Which of the following statements is FALSE about Eutectic point:

Higher temperatures than melting point of constituents

Compaction and sintering are combined into a single operation during:

Hot isostatic processing

A cold shut casting defect is

Incomplete fusion of two fill fronts in the mold cavity due to the onset of solidification before fill was complete.

what is true related to the term "green part" in PM?

It is obtained after compacting the powders

The first foundry lab used this technique to make the aluminum paperweights

Jolt/Squeeze Mold Making with a Match Plate

This is usually of the least concern among the three dimensional changes listed

Liquid metal contraction

The following is a characteristic of a dry sand mold (check reference book before answer):

May be stored for long periods of time before pouring

The shaped void within a mold that fills with molten metal and ultimately produces the cast product

Mold cavity

Intricate three-dimensionally-complex shapes can be made by this P/M technique that has similarities to die casting.

P/M injection molding

what happen when the part is transferred to the high-temperature section of the sintering furnaces

Porosity is reduced All of the options are valid Develop the strength of the part Bonding of particles

"Directional solidification" means that the solidification (check reference book before answer!):

Proceeds from the edges of the casting towards the riser location

Which can be the best definition of casting process?

Process where a liquid metal is poured in a mold

This additional reservoir of liquid metal is positioned inside a mold to compensate for solidification shrinkage

Riser

Compaction in P/M is generally performed at ___ temperature.

Room

The horizontal portion of a gating system that channels molten metal from the sprue to the gates

Runner

To be effective, risers should have ___.

The least amount of surface possible, to cool slowly

A misrun is when

The metal freezes before the mold cavity is completely filled