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Mod 6 > Ferrous Metals > Flashcards

Ferrous Metals Flashcards

1
Q

How is steel made?

A

Pure iron is smelted and mixed with carbon and other additives based on the type of steel desired.

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2
Q

Restrictions of steel

A

High density

Susceptible to corrosion

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3
Q

What percentage of an aircrafts structure is steel?

A

9-16

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4
Q

What are the main advantages of steel?

A

High modulus of elasticity

High strength

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5
Q

What are the alloy selection considerations?

A 
Service temperature
Strength
Stiffness
Fatigue properties
Fabricallity
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6
Q

Effects of carbon in steel

A

Primary hardening element
Allows steel to be heat treated
Hardness increases with carbon percentage up to around 1.05%

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7
Q

Low carbon steel percentage and uses

A

0.1-0.3%

Manufacture of safety wire and secondary structures

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8
Q

Medium carbon steel percentage and applications

A

0.3-0.5%

Machining or surface hardness is desired

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9
Q

High carbon steel percentage and uses

A

0.5-1.05%

For extreme hardness as in springs, filed, and cutting tools

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10
Q

Effects of sulphur in steel

A

Increases machinability in free machining steel

Reduces ductility and weld ability with increasing content

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11
Q

Effects of manganese on steel

A

Increases strength and hardness, but not as much as carbon
Decreases ductility and weldability but not as much as carbon
Has a significant effect on hardenability

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12
Q

Effects of silicon on steel

A

One of the principal de-oxidisers
Detrimental to surface quality in low carbon steels
Less effective than manganese at increasing rolled strength and toughness

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13
Q

Effects of phosphorus on steel

A

Increases strength hardness and corrosion resistance

Reduces ductility

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14
Q

Effects of nickel on steel

A

Increases hardenability and impact strength

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15
Q

Effects of chromium on steel

A

Increases corrosion and oxidisation resistance
Improve high temperature strength
Increases hardenability

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16
Q

What is chromium used with to achieve superior mechanical properties?

A

Nickel as a toughening element

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17
Q

Effects of vanadium on steel

A

Increases yield and tensile strengths

Small amounts can significantly increase the strength

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18
Q

Effects of molybdenum on steel

A

Increases hardenability
Secondary hardening of quenched steels
Increases creep strength in low allow steel at elevated temperatures

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19
Q

Effect of titanium on steel

A

Improves toughness

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20
Q

What is the AISI?

A

American iron and steel institute

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21
Q

First two digits in a steel designation represent what?

A

Primary alloying element

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22
Q

Second 2/3 digits in steel designation represent what?

A

Carbon percentage in the alloy

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23
Q

What type of steel is 10XX?

A

Pure carbon steel

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24
Q

41XX steel type

A

Chromium and molybdenum alloys

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25
Q

43XX type steels

A

Nickel, chromium, and molybdenum alloys

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26
Q

52100 steel

A

Chromium alloy with 1% carbon

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27
Q

93XX steel type

A

Same as 43XX but with a different ratio.

28
Q

What are the 2 heat treatment processes used to soften metal?

A

Tempering

Annealing

29
Q

How is steel hardened?

A

It gets heated above its critical temperature for a uniform dispersal of carbon in the iron matrix before it gets quenched in water, oil, or brine depending on the quench speed required

30
Q

What has the fastest and slowest quenching speeds for oil, water and brine?

A

Oil- slowest
Water- medium
Brine- fastest

31
Q

How is annealing done?

A

The steel is heated 50degrees above its critical temperature and left to cool slowly.

32
Q

What can’t be hardened?

A

Pure iron
Low carbon steels
Wrought iron

33
Q

What is normalising?

A

Relieving stresses from metals by heating it to 100F above upper critical temperature, soaking it for a period, and leaving it to cool at room temperature

34
Q

What is a ferrite state?

A

Pure iron. has a body centred cubic lattice that absorbs .02% carbon

35
Q

What is a austenite state?

A

Face centred cubic that can absorb up to 2% carbon

36
Q

What is cementite?

A

Chemical compound of iron and carbon, the more carbon the higher the cementite level and hardness, but leaving the metal more brittle

37
Q

What is pearlite?

A

2 phased laminar structure made of alternating alpha ferrite (88%) and cementite (12%)

38
Q

What is CRES?

A

Corrosion-resistant steel

39
Q

What does the 3 digit system refer to?

A

200 and 300 series- austenitic

400 series- martensitic or ferritic

40
Q

What are the 200 and 300 series alloys?

A

Chromium nickel

Chromium nickel manganese

41
Q

How much carbon is in the 400 series CRES?

A

Below 0.1%

42
Q

How are austenitic CRES hardened and heat treated?

A

Hardened through cold working

Can only be annealed

43
Q

Can ferritic CRES be heat treated?

A

No, they can only be work or strain hardened due to the low carbon levels.

44
Q

What are the martensitic 400 series alloys?

A

Straight chromium alloys

45
Q

How are martensitic CRES hardened?

A

By cooling them from high temperatures

46
Q

What could the 200 and 300 series CRES be used for?

A

Under water applications

47
Q

What could the ferritic CRES be used for?

A

Piping and tubing

48
Q

What could the martensitic CRES be used for?

A

Turbine blades

49
Q

Some disadvantages of CRES

A

Hard to cut or form, so technician needs to be experienced.

Can lose corrosion resistance to high temperatures

50
Q

What makes up precipitation hardened steel?

A

Very little carbon
15-17% chromium
4-7% nickel
Other alloying elements

51
Q

What can precipitation hardened steels be used for?

A

Airframes that need high strength and corrosion resistance.
Marine environments
Elevated temperature locations

52
Q

What are high strength, low alloy steels and what to applications?

A

Iron based alloys that are hardened to very high strengths

Application is based on strength range required but higher ranges can be used for landing gear.

53
Q

What is hydrogen embrittlement?

A

A phenomenon that causes the hydrogen in some metals to mitigate to areas such as grain boundaries when under load.
The hydrogen can also combine with the carbon to make methane which creates pressure that can cause cracking.

54
Q

What metals are mainly affected by hydrogen embrittlement?

A

Ferrous and titanium

55
Q

How can hydrogen embrittlement be avoided?

A

By a baking operation at 385F if the cracking has not initiated and the part is bare and porous

56
Q

What should you be aware of when reworking steel alloys?

A

Hydrogen embrittlement
Stress concentration
Untempered martensite

57
Q

When does stainless steel need protection and how is it protected?

A

Only when in contact with light weight alloys.

Cadmium plating, zinc spray, chromium passivating

58
Q

How are other steels protected?

A 
Cadmium plating and layer of paint
Phosphating and paint
Aluminium spray
Hard chromium plating
Chemical nickel plating
Silver plating, not in contact with aluminium
59
Q

What is galvanic corrosion?

A

Corossion caused by 2 dissimilar metals coming into contact with each other, based on how far apart in the nobility scale they are.
Typically an electrolyte is also needed to start the corrosion.

60
Q

What can be case hardened?

A

Ferrous metals

61
Q

What are the 2 methods of case hardening?

A

Carburising

Nitriding

62
Q

What are the 3 types of carburising and how are they done?

A

Gas similar to pack but with a carbon rich atmosphere instead.
Pack- heating component while packed with carbon rich material
Liquid heating the material in a bath of sodium or barium carbide

63
Q

How is flame hardening done?

A

By heating the material above its upper transitional level and quenching it immediately afterwards.

64
Q

What is induction hardening?

A

Heating up the material with a magnetic coil, then shutting off the coil and quenching the material in water.

65
Q

What is nitriding?

A

By heating up the metal in an ammonia rich environment, the nitrogen can penetrate the surface and harden the material, while leaving it with a better surface finish compared to carburising.

Mod 6 (8 decks)

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