Brainscape's Knowledge GenomeTM

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


See full index

BDS3 DMS > Stainless Steel and Wrought Alloys > Flashcards

Stainless Steel and Wrought Alloys Flashcards

1
Q

how are wrought alloys shaped

A

by cold working

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

what are uses of wrought alloys

A

wires (orthodontic) and partial denture clasps

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

what is the composition of steel

A

iron - 98%
carbon - 2%
chromium
manganese

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

what is the function of chromium in steel

A

improves tarnish resistance

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

how many solid state changes does iron go through with temperature

A

2
this is known as allotropic

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

what happens to iron at temperatures over 1400 degrees

A

BCC lattice structure, low carbon solubility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what happens to iron at temperatures between 900 and 1400

A

FCC lattice - higher carbon solubility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what happens to iron at temperatures under 900 degrees

A

BCC lattice structure - low carbon solubility

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

what is austenite and when does it exist

A

it is the initial solid solution which exists at high temperature

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

what is ferrite and when does it exist

A

it’s a very dilute solid solution
exists at a low temperature

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

when does cemenite exist

A

low temperatures

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

what is pearlite

A

eutectoid mixture of ferrite and cemenite

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

what is the definition of an alloy

A

2 metals that form a common lattice structure, are soluble in one another and form a solid solution

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

why is marsenite not a desired product

A

it is hard and brittle

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

what does fast cooling of austenite result in

A

pearlite

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

what does fast cooling of austenite result in

A

martensite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does tempering of martensite, a distorted lattice thats hard and brittle, give

A

pearlite

18
Q

how is martensite tempered

A

heated to 450 then quenched

19
Q

what are the four constituents of stainless steel

A

iron
carbon
chromium
nickel

20
Q

what level of chromium is required to regard steel as stainless

A

at least 12%

21
Q

what causes stainless steel to be corrosion resistant

A

chromium oxide layer

22
Q

what can stainless steel be attacked by that is very important to remember

A

chlorides

23
Q

what are the benefits of nickel

A

improves fracture strength
improves corrosion resistance
lowers austenite to martensite transition temperature

24
Q

what two forms does stainless steel come in

A

autentic
martensitic

25
Q

what is the martensitic stainless steel used for

A

dental instruments

26
Q

how does autentic stainless steel prevent from converting to martensite

A

contains sufficient chromium and nickel

27
Q

what is autentic stainless steel used for

A

dental equipment that isn’t cutting edge
orthodontic wires
sheet forms for denture bases

28
Q

does stainless steel heat harden

A

no

29
Q

how is the presentation of stainless steel when cast

A

soft/ malleable

30
Q

why can stainless steel NOT be manipulated repeatedly

A

due to rapid work hardening

31
Q

what is cold working

A

work done on metal/ alloy at a low temperature below the recrystallisation temperature and causes slip

32
Q

what is slip

A

dislocations collect at grain boundaries which results in a stronger/ harder material

33
Q

what are wrought alloys used for

A

wires and RPD clasps

34
Q

what are 18 chromium -8 nickel stainless steel wires used for

A

ortho appliances (springs and clasps)
partial dentures (clasp arms)

35
Q

what are the grades of 18-8 stainless steel

A

soft
half hard
hard
spring temper

36
Q

when does weld decay occur

A

between 500 and 900 degrees celsius

37
Q

what causes weld decay

A

chromium carbides precipitate at grain boundaries and the alloy becomes brittle which limits manipulation of the wire - less chromium in the centre of the solid solution makes it more susceptible to corrosion

38
Q

how do you minimise weld decay

A

low carbon content steel
stabilised stainless steel

39
Q

what does stabilised stainless steel consist of

A

contain small amounts of titanium or niobium
forms carbides preferentially
not at grain boundaries

40
Q

advantages of using stainless steel as denture base

A

fracture resistant
corrosion resistant
high polish attainable
high thermal conductivity
high impact strength

41
Q

what are disadvantages of stainless steel as a denture base

A

possible dimensional inaccuracy
loss of fine detail during many stages
difficulty to ensure uniform thickness

BDS3 DMS (6 decks)

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