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CAT B- Mod 6 Materials and Hardware > 6.1- Aircraft Materials- Ferrous > Flashcards

6.1- Aircraft Materials- Ferrous Flashcards

1
Q

Where does the word ferrous come from?

A

Latin for ferrum, referring to metals and alloys.

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2
Q

What is important about any alloy containing iron?

A

It is ferrous and magnetic.

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3
Q

What is iron in the periodic table?

A

Fe, atomic number 26.

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4
Q

What are pure irons properties?

A

Ductile, soft and easily formed.

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5
Q

What is the density of pure iron?

A

7.9g/cm³

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6
Q

How is oxidisation of pure iron reduced?

A

By alloying with carbon and other elements.

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7
Q

How is iron produced?

A

Mixing iron ore with coke and limestone and submitting it too hot air.

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8
Q

What is the slag?

A

The reaction of limestone with impurities in the iron and coke, it sits on the top.

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9
Q

What percentage of cast iron is carbon?

A

3.8-4.7%

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10
Q

What is the issue with cast iron?

A

Due to its high carbon content it is brittle.

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11
Q

Cast iron isn’t often used on aircraft, but where can it be found?

A

Valve guides due to its porosity allowing it too hold lubricant and piston rings.

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12
Q

How many tonnes of steel is made annually?

A

1.6 billion tonnes.

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12
Q

How is steel made?

A

Cast iron is re-melted, pure oxygen is then forced in, combining with carbon and burning. A controlled amount of carbon is then put back in.

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13
Q

What happens to the ingots of molten steel after they solidify?

A

They are heated to 1200C, and rolled.

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14
Q

What are the considerations for alloy selection?

A

Service Temp
Strength
Stiffness
Fatigue
Fabricability

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15
Q

How much carbon is in steel?

A

Up to 2%. Most common is 0.15% to 1%.

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16
Q

What happens when the carbon content of iron reaches 6%?

A

The metal is too brittle, it cannot be formed, machined, processed or used.

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17
Q

What is tensile strength?

A

Withstand stress in tension.

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18
Q

What is compressive stress?

A

Withstand pressing or squeezing.

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19
Q

What is shear strength?

A

Withstand stress acting coplanar with a material cross section.

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20
Q

What is torsional strength?

A

Resist rotational shear.

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21
Q

What is flexural strength?

A

Bending strength.

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22
Q

What is fatigue strength (endurance)?

A

Resist repeated loading.

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23
Q

What is impact strength?

A

Ability to resist shock.

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24
Q

What is hardness?

A

Resist cutting, penetration and abrasion.

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25
Q

What is malleability?

A

To be bent, formed or shaped without cracking or breaking.

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26
Q

What is ductility?

A

To be drawn into wire stock, extrusions or rods.

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27
Q

What is brittleness?

A

Tendency to break or shatter.

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28
Q

What is conductivity?

A

Enables it too carry heat or electricity?

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29
Q

What is thermal expansion?

A

To expand when heated and shrink when cooled.

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30
Q

What is elasticity?

A

Return to its original shape after normal stretching or bending.

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31
Q

What is toughness?

A

Resist tearing or breaking when it is bent or stretched.

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32
Q

What is fusibility?

A

The ability of a metal to be joined by heating and melting.

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33
Q

Name some of the more common alloying ingredients.

A

Carbon, sulphur, silicon, phosphorus, nickel and chromium.

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34
Q

What happens when carbon is alloyed with iron?

A

Iron carbites in cementite form are made.

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35
Q

What decreases when carbon content increases?

A

Malleability and weldability.

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36
Q

What percentage is a low carbon steel?

A

0.1-0.3

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37
Q

What percentage is a medium carbon steel?

A

0.3-0.5

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38
Q

What percentage is a high carbon steel?

A

0.5-1.05

39
Q

What does sulphur do and how can it be counteracted?

A

Makes it brittle and manganese.

40
Q

What does silicon do as a alloying agent?

A

Hardener, and in small quantities ductility.

41
Q

In low carbon steels what can silicon cause?

A

Bad surface finish.

42
Q

What does phosphorus do as a alloying agent?

A

Raises the yield strength and resistance to atmospheric corrosion.

43
Q

What is the most amount of phosphorus used to avoid brittleness?

A

0.05%

44
Q

What does nickel do as a alloying agent?

A

Strength, hardness and yield strength.

45
Q

What does chromium do as a alloying agent?

A

Wear and corrosion resistance.

46
Q

What does molybdenum do as a alloying agent?

A

Reduces grain size, better impact strength and elastic limit.

47
Q

Is Chrome Molybdenum alloy the most commonly used?

A

Yes

48
Q

What is the SAE designation for chrome-moly?

A

4130 (1% moly 0.3% carbon)

49
Q

Heat treated 4130 has how many times more tensile strength than 1025?

A

4 times.

50
Q

What does vanadium do as a alloying agent?

A

When combined with chromium, produces strong, tough, ductile steel alloy.

51
Q

What does tungsten do as a alloying agent?

A

High melting point.

52
Q

Where is tungsten used?

A

Breaker contacts in magnetos and high speed cutting tools.

53
Q

Where is vanadium used?

A

Tooling

54
Q

Where is molybdenum used?

A

Engine parts

55
Q

Where is chromium used?

A

Balls and rollers or bearings.

56
Q

What does CRES contain?

A

Large amounts of chromium and nickel.

57
Q

What is cres well suited for?

A

High temp areas such as firewalls and exhausts.

58
Q

What is the only time that cres needs a protective coating?

A

When in contact with light weight alloys.

59
Q

What three categories of stainless steel are there?

A

Austenitic
Ferritic
Martensitic

60
Q

What are 200/300 series stainless steels?

A

Austenitic

61
Q

How does an austenite structure form?

A

When steels are heated to above their critical range (800 to 925f) and held there.

62
Q

How can austenite steels be hardened?

A

Cold working, heat treatment only anneals them.

63
Q

What series are ferritic stainless steels?

A

400, chromium is the main alloying element.

64
Q

What are some of the characteristics of ferritic stainless steels?

A

Magnetic, good ductility and welded easily.

65
Q

How are ferritic stainless steels hardened?

A

Cold rolling.

66
Q

What is martensitic stainless steels?

A

Essentially a high carbon version of ferritic, with higher chromium. The combination offers heat treatment options and corrosion resistance.

67
Q

How are steels classified?

A

Society of Automotive Engineers (SAE) system, 4 digit system.

68
Q

What do the 4 SAE digits represent?

A

First digit- principle alloying element
Last two- carbon percentage

69
Q

What SAE numbers are carbon steels?

A

10xx
11xx
12xx
15xx

70
Q

What SAE numbers are Manganese steels?

A

13xx

71
Q

What SAE numbers molybdenum steels?

A

40xx
44xx

72
Q

What is a eutectoid?

A

A metal that can exist in more than one different form at the same temp.

73
Q

What cubic form is ferrite?

A

Body centre cubic

74
Q

What cubic form is Austenite?

A

Face centred cubic, it can absorb more carbon than ferrite.

75
Q

What is cementite also known as?

A

Iron carbide

76
Q

What is pearlite?

A

Two phased lamellar structure composed of alternating layers of alpha-ferrite (88%) and cementite.

77
Q

How is pearlite formed?

A

By eutectoid reaction when austenite is slowly cooled below 727c.

78
Q

In simple terms how is steel hardened?

A

Raised above critical temp, steel becomes austenite and absorbs carbon in solid state. Then quenched and carbon is trapped.

79
Q

What are the important factors in heat treatment?

A

Carbon content, temp and time taken to cool.

80
Q

What is a BCT crystal?

A

Body centred tetragonal structure- martensite, stronger harder and more brittle than BCC.

81
Q

What happens above the critical temp to the structure?

A

Goes from BCC to FCC.

82
Q

What is quenching?

A

Rapidly cool a material in medium such as water, oil or air.

83
Q

What is annealing?

A

It softens and releases stress in the metal.

84
Q

How does annealing work?

A

Heat to 10c above critical and heat soak, then cooled slowly.

85
Q

What is the normalising process?

A

Heating steel to 38c above critical limit and soaking for prescribed time, then cooled at room temp.

86
Q

What steels are best suited to case hardening?

A

Low carbon low alloy steels.

87
Q

What two methods are used to case harden?

A

Carburising and nitriding.

88
Q

What is carburising?

A

Heat treatment process that diffuses carbon into the surface of a metal?

89
Q

What is nitriding?

A

Diffuses nitrogen into it to increase hardness.

90
Q

What are the three methods of carburising?

A

Pack- fire clay container
Gas- carbon monoxide
Liquid- sodium cyanide bath

91
Q

How is nitriding carried out?

A

Hardening and tempering, heated to 540c and surrounded with ammonia gas.

92
Q

What parts are commonly nitrided?

A

Engine crankshafts and cylinder walls for wear resistance.

93
Q

What carbon content can flame hardening be carried out on?

A

At least 0.4% after normalisation.

94
Q

What is induction hardening?

A

The same has flame hardening but using a coil surrounding the metal.

CAT B- Mod 6 Materials and Hardware (14 decks)

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