EMTL 250 > Module 3 > Flashcards

Module 3 Flashcards

(66 cards)

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1
Q

What is carburization?

A

Heating a piece in a carbon-rich environment to allow carbon to dissolve into the surface.

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2
Q

What is surface hardening?

A

A process to increase abrasion/wear resistance of a material. (Increase the hardness of the surface)

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3
Q

What is the purpose of carburization?

A

To increase the surface hardness of the piece.

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4
Q

What is nitriding?

A

Heating a piece in a nitrogen-rich environment to allow nitrogen to diffuse into the surface. (Increase hardness of the surface)

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5
Q

What is the purpose of nitriding?

A

To increase the surface hardness and wear resistance of the piece.

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6
Q

What are the advantages of low temperature carburizing?

A

No quench required, can be used for high temp service

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7
Q

What is flame hardening?

A

The use of a heat source to heat the surface, forming martensite.

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8
Q

What is hard facing also known as?

A

Hard Surfacing, Overlay, or Cladding

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9
Q

What is FSS?

A

Ferritic Stainless Steel

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10
Q

What is SCC?

A

Stress Corrosion Cracking

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11
Q

What are some applications of FSS?

A

Cutlery, furnace parts, fridge doors, etc.

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12
Q

What is the purpose of cladding?

A

Wear resistance

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13
Q

What determines the depth of hardening in flame hardening?

A

The time spent heating the surface.

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14
Q

What is the alloying element in Martensitic Stainless Steel?

A

Chromium

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15
Q

What are the alloying elements used in low temperature carburizing?

A

Cr, Al, Ti, V, Nb, etc.

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16
Q

What is the carbon content in Martensitic Stainless Steel?

A

0.2% MIN

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17
Q

What is the characteristic of martensite in Martensitic Stainless Steel?

A

Quench hardenable and allotropic

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18
Q

What is the transition temperature?

A

The temperature at which a material changes from being ductile to brittle.

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19
Q

How are two different materials fused together in hard facing?

A

Welding or High temperature spraying or explosives

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20
Q

What is the hardenability of martensitic stainless steel?

A

High

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21
Q

What does ‘18/8’ mean in relation to ASS properties?

A

18% Chromium, 8% Nickel

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22
Q

What are the material limitations for flame hardening?

A

Low carbon content and low hardenability.

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23
Q

What are the mechanical properties of ASS?

A

High Ductility, Strength, Toughness, Best general corrosion resistance

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24
Q

What is the basic 18/8 grade of ASS used for?

A

Indoor Applications

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25
What is the ductility of low carbon martensite?
Low
26
What is the purpose of adding Mo to ASS grade 316?
Extra defense against pitting
27
What is precipitation hardening stainless steel?
Stainless steel with added copper and heat treatment for increased strength
28
What is the reaction between carbon and chromium in martensitic stainless steel?
Chromium Carbides
29
What is an example of a very hard surface used in hard facing?
Tungsten Carbide
30
What has the best general corrosion resistance?
ASS
31
Why is austenite in ASS considered 'meta-stable'?
Minimal nickel addition is not enough to truly stabilize it at room temperature (It wants to be FCC but is BCC)
32
What is sensitization?
Loss of corrosion resistance in stainless steel due to the formation of Cr-Carbides
33
What is the role of the transition temperature in FCC stabilization?
It acts as a FCC stabilizer, countering the BCC structure of chromium.
34
What is the composition of 17-7 PH stainless steel?
17% chromium, 7% nickel, 4% copper
35
What happens when ASS work hardens?
Atoms move and form martensite
36
What temperature range causes sensitization?
Between 500C and 900C
37
What are the applications of precipitation hardening stainless steel?
Chemical piping, heat exchangers, offshore structures, rebar
38
What is intergranular corrosion?
Corrosion that occurs along the grain boundaries of a material
39
In what type of applications is hard facing used?
Extreme abrasion applications (e.g. Earth moving)
40
What is the purpose of aging heat treatment in precipitation hardening stainless steel?
To form hard and brittle intermetallic compounds
41
Why is Nickel used as a stabilizer in ASS?
Nickel is used as a stabilizer in ASS because it has an FCC structure.
42
What are the advantages of precipitation hardening stainless steel?
Increased strength
43
What is the composition of Austenitic Stainless Steel?
Chromium (12% MIN), Carbon (0.08% MAX), Nickel (7-22%).
44
What is weld decay?
Sensitization in a narrow band near the weld toe
45
What is a low carbon grade?
A grade with a low carbon content.
46
What is creep?
High temperature plastic deformation
47
How does surface deposit contribute to corrosion?
It blocks oxygen, preventing the formation of the oxide layer | the start of pitting
48
Is FCC magnetic?
FCC is not magnetic.
49
What is added to creep resistant steel to prevent creep?
Chromium/ Tungsten/Molybdenum as a carbide former
50
What is the structure of Austenitic Stainless Steel at all temperatures?
Austenite (FCC) at all temperatures.
51
What do Chromium Carbide Precipitates do in creep resistant steel?
Act as 'locks' and resist creep
52
In which environments does SCC occur?
SCC may occur in chloride environments, such as salt water.
53
Why does the pit grow deeper into the piece?
Oxygen concentration is lowest at the base of the pit
54
What is High Strength Low Alloy Steel (HSLA) also known as?
Microalloyed steel
55
What breaks down the Cr-Oxide layer?
Chlorides, which are more reactive than oxygen
56
What is the purpose of hot rolling?
To reduce the thickness of the steel
57
What can sensitization cause?
Corrosion next to the weld, leading to rapid failure
58
What does the breakdown of the Cr-Oxide layer cause?
Pitting
59
What is pitting?
A type of corrosion.
60
What are the mechanical properties of Austenitic Stainless Steel?
Great ductility, good strength, and great toughness, best general corrosion resistance
61
What is the purpose of controlled cooling?
To achieve the desired cooling rate
62
What is the purpose of the Thermo-Mechanical Controlled Process (TMCP)?
To heat a slab and dissolve all precipitates
63
How can sensitization be prevented?
Fast cooling, using a stabilized grade with Titanium or Niobium additions, and solution heat treatment
64
What is the purpose of coiling?
To facilitate transportation and allow the formation of Vanadium Carbides/Nitrides
65
What is the purpose of the Roughing Mill in the TMCP process?
To hot roll the slab down to a thickness of ~1"
66
What is the significance of FCC structure in terms of transition temperature?
FCC structure has no transition temperature.
EMTL 250
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