INTRODUCTION & AIRCRAFT MATERIALS FERROUS

Question 1

A body is said to be perfectly elastic if?

Answer 1

If a material can be deformed and then return to its original shape

Question 2

What are the three forms of simple stress?

Answer 2

Compression, tension, shearing

Question 3

Define “toughness” as a property of material.

Answer 3

The ability of a material to be deformed without breaking

Question 4

4. The three most important light weight structures in aircraft structure are…….?

Answer 4

Aluminium, magnesium and titanium

Question 5

5. The selection of materials should be a compromise between what?

Answer 5

between the quality of the material to fulfil the requested function and all costs

Question 6

What are the material characteristics of iron?

Answer 6

Density: 7.86 kg/m3 melting point: 1539 degrees C, soft, corrode easily, dense, malleable

Question 7

7. How is iron used to manufacture steel?

Answer 7

A mix of iron ore and coal (carbon) is heated in a blast furnace to create molten in which steel is then made from

Question 8

8. What process is used to make steel less corrosive?

Answer 8

It can be made less corrosive by turning it into stainless steel and adding chrome, phosphorous etc

Question 9

What principle element is used in steel alloy to create hardness?

Answer 9

Carbon

Question 10

10. What percentage of carbon is present in a low, medium and high carbon steels

Answer 10

Low 0-0.3 medium 0.3 – 0.5% and high is 0.5 to 1.5%

Question 11

What is the purpose of phosphorous as an alloying element?

Answer 11

Strength, hardness and corrosion resistance

Question 12

12. What system is used to identify steel alloys?

Answer 12

AISI or SAE

Question 13

13. What is the purpose of tempering in relation to carbon steel?

Answer 13

Tempering is used to relieve stress

Question 14

14. What heat treatment process is used to make steel soft and ductile?

Answer 14

Annealing

Question 15

15. What process is used to relieve stress in high strength steel after machining?

Answer 15

Normalising

Question 16

16. What choice of quenching mediums are there for steel after heat treatment?

Answer 16

Water brine and oil

Question 17

17. What does CRES stand for?

Answer 17

Corrosion resistant steel

Question 18

18. What are the three general groups that stainless steel are divided into based on their structure?

Answer 18

Austenite, ferretic, martensitic

Question 19

19. Name four disadvantages associated with stainless steel.

Answer 19

Difficult to cut, Greater coefficient of expansion, not suitable for a high temperature environment e.g engines, experience technicians required and hard to weld.

Question 20

20. What is “Hydrogen Embrittlement” and what materials does it affect?

Answer 20

Hydrogen concentrations react with carbon forming methane and causing cracks

Question 21

21. If hydrogen embrittlement is suspected what must be done?

Answer 21

Heat or oven heating

Question 22

22. What protective treatments are on offer for ferrous materials other than stainless steel?

Answer 22

Galvanic corrosion, case hardening, plating, painting

Question 23

What number series of CRES are known as austenite (non-magnetic)

Answer 23

200 & 300

Question 24

What are the disadvantages of CRES.

Answer 24

Difficult to cut
Greater coefficient of expansion
Not suitable in a high temperature environment
Experienced technicians required
Low temperature coefficient
Bends when drilling

Question 25

Austentic steel alloys typically contain what amount of chromium and nickel?

Answer 25

18% or more chromium | 3.5% to 22% nickel

Question 26

Ferritic 400 series contain how much chromium?

Answer 26

15-30%

Question 27

Can martencitic steels be heat treated?

Answer 27

Yes

Question 28

What are the benefits of precipitation hardening?

Answer 28

Hardened to very high strength | Excellent corrosion resistance

Question 29

What is hydrogen Embrittlement?

Answer 29

The hydrogen will migrate to the grain boundaries or voids in the metal. At high temperature hydrogen concentrations react with carbon forming methane and causing cracks.

Question 30

What methods are there to removing hydrogen embrittlement?

Answer 30

Re-heating | Pickeling

Question 31

What is galvanic corrosion

Answer 31

Galvanic corrosion is corrosion caused by the reaction between two dissimilar metals when placed against each other in an assembly

Question 32

What is case hardening.

Answer 32

Case hardening is when a low carbon steel is placed in a carbon rich environment to create a hardened layer around the outside which is hard, durable and load bearing.

Question 33

What is carburising?

Answer 33

Carburising produces a thin layer of high carbon steel on the surface of a low carbon steel component.

Question 34

What are the three methods of carburising?

Answer 34

Gas - CO2 Pack - charcoal Liquid - cyanide