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Me 37 > Chapter 13 > Flashcards

Chapter 13 Flashcards

1
Q

Materials engineering

A

The study of the structure, properties, processing, and performance of engineering materials and the systems interactions.

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2
Q

Materials processing

A

The devienne and technology through which a material is converted into a useful shape with structure and properties that are optimized for the prosper service environment.

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3
Q

Casting

A

Liquid flows into and assumes the shape of a prepared container after solidifying

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4
Q

Material removal

A

Remove selected segments from oversized pieces.

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5
Q

Machining

A

The mechanical cutting of materials

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6
Q

Deformation processes

A

Exploit the ductility or plasticity of certain materials to produce a desired shape by mechanically moving or rearranging the solid.

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7
Q

Consolidation processes

A

Build a desired shape by putting smaller pieces together.

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8
Q

Powder metallurgy

A

Manufacture of a desired shape from particulate material, can involve casting.

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9
Q

Additive manufacturing or direct digital manufacturing

A

Includes a variety of processes developed to directly convert a computer drawing to a finished product by a layer by layer deposition of material.

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10
Q

Step one of casting

A

A container must be produced with a cavity having a desired shape and since (mold cavity) with due allowance for shrinkage. Mold material must withstand high temps.

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11
Q

Multiple use molds

A

Can be quite costly, but can be used multiple times

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12
Q

Single use molds

A

Preferred for the production of smaller quantities. Can not be used over and over.

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13
Q

Step 2

A

À melting process must be capable of providing molten material at the proper temperature, in the desired quantity, with acceptable quality, at a reasonable cost.

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14
Q

Step 3

A

A pouring technique must be devised to introduce molten metal into the mold.

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15
Q

Step 4

A

The solidification process should be properly designed and controlled. Shrinkage must not produce voids.

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16
Q

Step 5

A

It must be possible to remove the cast from the mold. With single use molds they are broken apart and destroyed after each cast, but multiple can be harder to remove

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17
Q

Step 6

A

Various cleaning finishing and inspection operations may be required after the casting is removed from the mold.

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18
Q

Pattern

A

An approximate duplicate of the final casting

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19
Q

Flask

A

The ridged metal or wood frame that holds the molding aggregate

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20
Q

Cope

A

In a horizontally parted two part mold, the top half of the flask is called this.

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21
Q

Drag

A

The bottom half of the flask is called this.

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22
Q

Core

A

A sand shape that is inserted into a mold to produce the internal features of a casting such as holes or passages.

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23
Q

Core boxes

A

Cores are produced in word metal or plastic tooling and are known as this.

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24
Q

A core print

A

A feature added to the pattern and is used to locate and support a core within the mold.

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25
Q

Mold cavity

A

A shaped hole into which the molten metal is poured into.

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26
Q

Rose

A

An additional void the the mold that also fills with molten metal. It provides a reservoir of additional liquid that can flow to compensate for any shrinkage.

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27
Q

Gating system

A

The channels that deliver the molten metal to the mold cavity.

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28
Q

Pouring cup

A

Portion of the gating system that recurved the molten metal and controls its delivery to the rest of the mold.

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29
Q

Sprue

A

From the pouring cup the metal travels down a sprue.

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30
Q

Runners

A

Horizontal channels that the metal travels down following the sprue.

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31
Q

Gates

A

Entrances into the mold cavity

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32
Q

Vents

A

May be included in a mold or core to provide an escape for the gases present.

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33
Q

Parting line or parting surface

A

Interface that separates the cope and stage halves of the flask.

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34
Q

Draft

A

Describes the taper ok the pattern that permits it to be withdrawn from the mold.

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35
Q

Casting

A

Process and the product when molten metal is poured and solidified in a mold.

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36
Q

Solicitation

A

Molten material is poured and allowed to freeze into shape

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37
Q

Gas porosity or solidification shrinkage

A

Casting defects

38
Q

Nucleation

A

Occurs when stable particles of solid form from within the molten liquid. Solid state had a lower energy than the liquid.

39
Q

Undercooking

A

The difference between the melting point and the actual temperature of nucleation is known as this.

40
Q

Nucleation event

A

Produces a crystal or grain in the final casting. These grains can enhance mechanical properties.

41
Q

Inoculation grain refinement

A

Introducing solid particle for enhanced mechanical properties

42
Q

Second stage of solidification process

A

Growth, which occurs as the heat of fusion is extracted from the liquid material.

43
Q

Directional solidification

A

Solidification interface sweeps continuously through the material, and can be used to ensure a sound casting.

44
Q

Faster rates of cooling

A

Produce product with finer grain size and superior mechanical properties

45
Q

Chill zone

A

The rapid nucleation that occurs when molten metal contacts the cold mold walls and a randomly oriented crystals are predicted in the surface of a casting. As additional heat is removed, the grains of the zone grow inward.

46
Q

Columnar zone

A

Thin coin as grains produced by the crystals continuing to grow.

47
Q

Equiaxed zone

A

New crystals occurs in the interior of the casting as this region is produced

48
Q

Dross or slag

A

Can be trapped in the casting and impart surface finish machinability and mechanical properties. Lower pouring temperature cna reduce this or superheat.

49
Q

Gating systems and dross

A

They can be designed to prevent it from flowing into the mold cavity. Filters can be inserted into the feeder channels of the mold.

50
Q

Gas porosity

A

Bubbles formed by amounts of dissolved gas.

51
Q

How to stop gas porosity

A

Prevent the gas from dissolving into the molten metal. Perform the melting under vacuum, or a flux. Superheat temps kept low.

52
Q

Vacuum degassing

A

Sprays molten metal through a low pressure environment. The amount of dissolved gas in reduced.

53
Q

Gas flushing

A

Passing small bubbles of inert or reactive gas through the metal resolved the bubbles.

54
Q

Dissolved gas can react

A

With something to produce a low density compound that can be removed with the slag.

55
Q

Museums and cold shuts

A

Defects produced as the metal begins to freeze before it had completely filled the mold.

56
Q

Fluidity

A

The ability of a metal to flow and fill a mold

57
Q

Fluidity is dependent on

A

Composition freezing temperature and the freezing range of the metal or alloy. Also surface tensions of oxide films. Most important is the pouring temp or amount of superheat.

58
Q

High pouring temp

A

Higher fluidity.

59
Q

Penetration

A

A casting surface that contains small particles of sand because the metal is too runny and flowed into voids.

60
Q

To minimize heat loss

A

Use shirt channels with round or square cross sections.

61
Q

Gates attached to thickest sections of a casting to control what

A

Shrinkage

62
Q

Turbulent flow

A

Tends to promote absorption of gases, oxidation of the metal, and erosion of the mold. Gating systems are designed to minimize this.

63
Q

Sprue well

A

Can be used to dissipate the kinetic energy of the falling metal and prevents splashing or turbulence.

64
Q

Choke

A

Serves to control the rate of metal flow. If choke is located near base of sprue, the flow is slowed and rather smooth.

65
Q

Runner extensions and runner wells

A

Because the first metal to enter the mold can likely contain contaminated, these will help trap it and keep it from tendering the cavity. Effective with aluminum casting as aluminum oxide have same density as molten aluminum.

66
Q

Three stages of shrinkage

A

1 shrinkage of the liquid as it cools to the temp where solidification occurs. 2 solidification shrinkage as the liquid turns into solid. 3 solid metal contraction as the solidified material cools to room temp.

67
Q

Metals that expand

A

Not all metals shrink during solidification, some actually expand.

68
Q

How can casting. Prevent solidification

A

They can be designed to have solidification occur where freezing begins rather est away from the fed gate and then move towards it.

69
Q

Alloys with large freezing ranges

A

Create shrinkage pores as they have a period of time when the material is in a slushy condition.

70
Q

Pattern makers contraction

A

Casting will contact further as it cools to room temperature after solidification.

71
Q

Hot tears

A

If the mold provides contraint during the time of contraction, cracking can occur.

72
Q

Risers must

A

Solidify after casting

73
Q

Riders should

A

Be designed to conserve metal

74
Q

Yield

A

Casting weight divided by the goal weight of the metal poured, it is clear that there is a motivation to make the risers as small as possible, yet still able to perform their task.

75
Q

Top riser

A

Sits on top of a casting. Have a shorter feeding distance, and occupy less space within the flask.

76
Q

Side risers

A

Located adjacent to the mold cavity and displaced horizontally along the partying line.

77
Q

Blind riser

A

If the riser is contained entirely within the mold. Blind riser is this

78
Q

Open riser

A

Open to the atmosphere. Top riser is this.

79
Q

Live risers

A

Receive the last hot metal that enters the mold and generally do so at the time when the metal I. The cavity has already begun to cook and solidify.

80
Q

Dead risers

A

Fill with metal that had already flowed through the mold cavity.

81
Q

Top risers are

A

Dead risers

82
Q

Risers apart of gating system are

A

Live risers

83
Q

Expendable mold processes

A

A new mold must be created for each casting

84
Q

Reusable mold

A

A permanent mold, can be used again.

85
Q

Pattern

A

A physical prepresentstion of the object to cast, modified dimensionally to reflect the casting process and the material being cast.

86
Q

Allowances

A

Modifications incorporated into a pattern. Most important is the shrinkage allowance

87
Q

To produce the desired final dimensions

A

The pattern must be slight larger than the room temperature casting.

88
Q

Draft

A

Incorporated at all pattern surfaces that are parallel to the direction of withdraw to prevent damage to the mold.

89
Q

Machining allowance or finish allowance

A

Added when smooth machines surfaces are required

90
Q

Distortion

A

An additional allowance. Depends greatly on the configuration of the casting.

91
Q

If a casting is to be made in a multitude metal mold

A

All pattern allowances should be incorporated into the machines cavity.

92
Q

Core allowances

A

All allowances to the casting should be applied to the cores that create holes and interior passages.

Me 37 (14 decks)

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