Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MAT2730 - Metals > Process routes > Flashcards

Process routes Flashcards

1
Q

P_____ –> S______ –> P_______

A

Process –> Structure –> Properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

List problems caused by rolling

A
  • flatness poor (solution is to pull it)
  • cavity
  • edge defects
  • crocodile defect (material explodes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why would crocodile defect (material explodes) occur during rolling

A
  • incorrect temp
  • too ‘greedy’ - doing too much too soon
  • incorrect strain rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Name a Ti-Al based alloy that is used in engine blades

A

Ti - 6Al - 4V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is Titanium so expensive

A

Due to the process it needs to undergo to become usable.

This process is called: The Kroll process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the Kroll process

A
  1. Energy needed to separate is 125MWhr/Tonne
  2. It is a batch process over 5 days
  3. Produce TiCl4 from TiO2 and Cl2
  4. React TiCl4 with magnesium to produce Ti
  5. Chip out Ti sponge
  6. Cost £5/kg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Name three processes used to procure Titanium

A
  • Kroll process
  • Hunter process
  • FFC process (electrolytic process)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the limitations of using FFC process (Fray, Farthing, Chen)

A
  • produces powder

- therefore further processing is required (additive layer manufacturing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What conditions should Titanium be melted in

A

Should be melted in a vacuum to avoid recombination with N

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why are higher grade alloys remelted once or twice

A

To ensure homogeneity and freedom of regions that may have picked up N, O or C

These are then forged more easily into ingots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What ways can Titanium be remelted and which is best

A
  1. Use a consumable arc (VAR method)
  2. Use a plasma beam with a water cooled copper crucible (skull melting

‘2’ has an advantage in that more time is available for inclusions to be dissolved or removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Difference between slabs and billets

A

Slabs - further processed and rolled into sheet/plates

Billets - processed into bar, rod, wire or tubes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Definition of solidification

A

how metal solidifies from molten state and resultant structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Definition of fluid flow

A

How easily the metal flows

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Definition of heat transfer

A

Shrinkage, causing defects due to how slow/fast cooling takes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Name three types of casting

A
  • Sand casting
  • Investment casting
  • Pressure/gravity casting (permanent mould)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

List the advantages of casting in general

A
  1. Extremely versatile
  2. Porosity is kept to a minimum
  3. Can produce a final product
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe sand casting

A
  1. A pattern is made in sand
  2. Molten metal is poured in
  3. It is left to cool
  4. The sand is broken away to procure product
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

List advantages and disadvantages of sand casting

A

A:
- can produce very large products

D:

  • poor surface finish
  • poor tolerances
20
Q

Describe investment casting (lost-wax process)

A
  1. A pattern is made out of wax
  2. The wax mould is coated and toughened
  3. After heat treatment a ceramic mould is formed and the wax is melted out
  4. Molten metal is poured into ceramic mould and left to cool
  5. Ceramic mould is broken off using vibrations
21
Q

List advantages and disadvantages of investment casting

A

A:

  • a number of moulds can be combined into one larger mould for pouring (TREE)
  • good surface finish
  • good tolerances can be achieved

D:

  • limited in size
  • relatively expensive
22
Q

Describe pressure/gravity casting

A
  1. Suck molten metal upwards into cast
  2. Solidifies under pressure
  3. This can the be repeated
23
Q

List advantages and disadvantages of pressure/gravity casting

A

A:

  • can create lots of complex components
  • Best tolerances
  • Best finish

D:
- limited size

24
Q

Describe centrifugal casting

A
  1. Spin molten metal whilst solidifying

can be used for composites

25
Q

List three solid state processes

A
  1. Forging
  2. Rolling
  3. Extrusion
26
Q

Describe the extrusion process

A
  1. A round billet is placed into a chamber and forced through a die opening by a ram
  2. The die dictates the final shape
  3. This is carried out in elevated conditions depending on the material
27
Q

What temperature should Mg, Pb, Steel and Ti be at during extrusion

A

Mg - 450
Pb - 22
Steel/Ti - 800/1100

28
Q

What two types of extrusion are there

A
  1. Direct extrusion

2. Indirect extrusion

29
Q

What is the difference between direct and indirect extrusion

A

Direct - the billet slides relative to the container walls

Indirect - the die moves towards the billet

30
Q

What can be needed during extrusion to help the process

A

lubricant

31
Q

What parameters effect extrusion

A
  • temperature
  • speed
  • friction factor (effects finish)
32
Q

Equation for extrusion ratio

A

R = Ao / Ar

Ao = xarea of billet
Ar = xarea of die
33
Q

Equation for extrusion pressure

A

P/σ = a + bln(R)

R = extrusion ratio

34
Q

Equation for extrusion strain rate

A

Extrusion strain rate
= 6vln(R) / D

D = diameter of billet
v = speed
35
Q

What are the defects that can be caused due to extrusion

A

Surface cracks - sometimes not visible to naked eye

Piping - occurs when there are impurities in the billet

36
Q

Describe the rolling process

A

The process of reducing the thickness (gauge) of a workpiece by compressive forces applied through a set of rolls

37
Q

What type of rolling equipment is used for thin sheet of high strength materials

A

cluster (Sendzimir or Z) mill

38
Q

List defects caused by rolling and how can they be reduced

A

Surface defects - due to inclusions in the material, scale, rust or roll markings

reduced by: prior treatment of the ingot

Structural defects - wavy edges, cracking, alligatoring

reduced by: better control of homogenisation prior to rolling

Anisotropy

39
Q

Describe the forging process

A

The permanent deformation of a material by heating and using force to change its shape

40
Q

What is forgeability

A

Capability of a metal to undergo deformation without severe surface cracking

41
Q

Equation for the upsetting force

A

P = σ( (1 + 2μr) / 3h )

42
Q

Why does barrelling take place during forging

A

Due to tools being a different temperature will cause non-homogenous cooling

43
Q

Difference between open and impression die forging

A

open:
deformation of specimen between two platens

impression:
take 2 dies and squeeze material down into desirable shape

44
Q

What is closed die forging

A

similar to impression forging but with no excess material

45
Q

What is near net shape forging

A

3D printing basically, and creates a shape close to final product

46
Q

What is isothermal forging

A
  • Dies are heated to the same temperature as workpiece

- this means more control over homogenisation

47
Q

List the defects caused by forging

A
  1. Surface cracking
  2. Buckling or lapping (due to excess material)
  3. Anisotropy

MAT2730 - Metals (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions