6.1- Aircraft Materials- Ferrous

Question 1

Iron in its pure form has what characteristics?

Answer 1

Soft, malleable and ductile.

Question 2

How is cast iron formed?

Answer 2

Molten iron with more than 2% carbon poured into a mould.

Question 3

How is iron extracted from iron ore?

Answer 3

Mixed with coke and limestone and heated in a furnace. Iron sinks to the bottom.

Question 4

How is steel made using pure iron?

Answer 4

Pure iron is remelted in a furnace where carbon is introduced.

Question 5

Why is the use of steel restricted for aircraft?

Answer 5

High density

Susceptible to corrosion.

Question 6

What are some of the characteristics considered when picking an alloying element?

Answer 6

Service temp
Strength
Stiffness
Fatigue Properties
Fabricability.

Question 7

What does using carbon as an alloying element do?

Answer 7

Allows heat treatment of steel

Hardness and tensile strength are increased.

Question 8

Low carbon steel contains what percentage of carbon?

Answer 8

0.1-0.3%

Question 9

High carbon steel contains what percentage of steel?

Answer 9

05.-1.05%

Question 10

What does using sulphur as an alloying element do?

Answer 10

Decreases ductility and weld ability.
Normally kept at low levels, or paired with manganese
Improves machineability.

Question 11

What does using manganese as an alloying element do?

Answer 11

Contributes to strength and hardness

significant effect on hardenability of steel

Question 12

What does using silicon as an alloying element do?

Answer 12

Deoxidiser

Detrimental to surface quality in low carbon steel.

Question 13

What does using phosphorus as an alloying element do?

Answer 13

Increases strength, hardness and corrosion resistance

Decreases ductility.

Question 14

What does using Nickel as an alloying element do?

Answer 14

Increases hardenability and impact strength.

Question 15

What does using chromium as an alloying element do?

Answer 15

Increase corrosion/oxidation resistance

increase hardenability and high temp strength.

Question 16

What does using molybdenum as an alloying element do?

Answer 16

Produces secondary hardening of steel during quenching.

Question 17

What does using vanadium as an alloying element do?

Answer 17

Increases yield strength and tensile strength.

Question 18

What does using titanium as an alloying element do?

Answer 18

Improve toughness.

Question 19

What system is used to give designations to low carbon steels?

Answer 19

AISI (American Iron and Steel Institute).

Question 20

What do the first two digits refer to in AISI (steel designation)?

Answer 20

Specific alloying element.

Question 21

What do the last two digits refer to in AISI (steel designation)?

Answer 21

Percentage of carbon

It is the last three digits in a 5 digit designation.

Question 22

What does a 10xx refer to?

Answer 22

Plain carbon steels (carbon and manganese).

Question 23

What does a 41xx refer to?

Answer 23

Chromium and Molybdenum alloy steels.

Question 24

What does a 43xx refer to?

Answer 24

Nickel, chromium and molybdenum alloy steels.

Question 25

What does a 52100 refer to?

Answer 25

Chromium alloy with 1% carbon.

Question 26

What does a 93xx refer to?

Answer 26

Nickel, chromium and molybdenum alloy steels but in a different ratio to 43xx steels.

Question 27

If you saw a steel with designation 4340 what is its breakdown?

Answer 27

Nickel-chromium-molybdenum alloy with 0.4 carbon.

Question 28

What is the specific name of Nickel-Cobalt alloy with 0.3% carbon?

Answer 28

9Ni-4Co.30C 9 refers to percent of Nickel 4 refers to percent of cobalt.

Question 29

European designations differ slightly where can you find information on them?

Answer 29

Metallic material list in the SRM.

Question 30

What does SAE stand for?

Answer 30

Society of Automotive Engineers.

Question 31

What does annealing do?

Answer 31

Softens carbon steel to malleable state.

Question 32

What does quenching do?

Answer 32

Hardens to a state nearly as rigid and brittle as glass.

Question 33

What does tempering do?

Answer 33

Decrease hardness which increases ductility and toughness of quenched metal.

Question 34

Quenching often produces stresses in steel, what process relieves these?

Answer 34

Tempering.

Question 35

Why is accurate temperature control needed during tempering?

Answer 35

To ensure consistent replication of properties.

Question 36

What are the most accurate methods of temperature measuring?

Answer 36

Pyrometers and thermocouple controlled ovens.

Question 37

What is a less accurate way of measuring temperature of the metal during treatment.

Answer 37

Observing the colour, it is possible but not accurate and only possible with high carbon steels.

Question 38

What colour ranges does high carbon steel have whilst heating?

Answer 38

Yellow- brown- purple- blue.

Question 39

What can't be done to pure/wrought or extremely low carbon steels?

Answer 39

They can't be heat treated due to not having a hardening element.

Question 40

How is steel hardened?

Answer 40

Heated above critical temp, so that carbon dispenses through iron matrix. Then rapidly cooled by quenching.

Question 41

What liquids can be used to quench?

Answer 41

Water, oil, brine. | Oil is the slowest quench and brine the fastest.

Question 42

What happens if the quench is too quick?

Answer 42

The structure becomes martensite, a super saturated solution of carbon in the iron matrix.

Question 43

What is wrong with having a martensite structure?

Answer 43

Its far to brittle and hard for most uses.

Question 44

What is the process of annealing?

Answer 44

Heating to 50°F above critical temp and allowing it to soak, then slowly cooling in the furnace or a bath of hot sand.

Question 45

What is normalising?

Answer 45

Relieving stresses from machining or welding.

Question 46

How is normalising carried out?

Answer 46

Heating steel to 100°F above critical temp and soaking. It is then cooled at room temp.

Question 47

What does normalising do to the structure in terms of the carbon particles?

Answer 47

Allows the carbon to precipitate out of the austenitic structure.

Question 48

What do the two axis of the carbon phase diagram display?

Answer 48

% of carbon content and temperature.

Question 49

What is a metal called that can exist in two forms at the same temp?

Answer 49

Eutectoid.

Question 50

What is ferrite?

Answer 50

Pure iron, BCC that will absorb 0.02% carbon.

Question 51

What is austenite?

Answer 51

FCC iron, can absorb up to 2% carbon.

Question 52

What is cementite?

Answer 52

Chemical compound of carbon and iron, the more carbon the more cementite. But will be harder and more brittle. >2% carbon.

Question 53

What is pearlite?

Answer 53

Two phase lamellar structure, which alternating layers of alpha-ferrite (88%) and cementite (12%).

Question 54

What are the important factors in heat treatment of carbon steel?

Answer 54

Carbon content, temperature and time taken to cool.

Question 55

Since the 1940's stainless steel has also been known as what?

Answer 55

CRES- corrosion resistant steel.

Question 56

What are the key characteristics of CRES?

Answer 56

Corrosion resistance, strength, toughness and resistance to high temps.

Question 57

CRES doesn't use the SAE system but instead uses what?

Answer 57

A 3 digit system.

Question 58

What are the 200 and 300 series of CRES known as?

Answer 58

Austenitic.