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MMET 207 > Chapter 14 > Flashcards

Chapter 14 Flashcards

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1
Q

Define corrosion

A

Corrosion is the gradual destruction of materials, usually metals, by chemical reactions with their environment.

Corrosion can lead to significant structural and economic issues in various industries.

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2
Q

List and explain problems caused by corrosion

A
  • Structural failure
  • Decreased lifespan of materials
  • Increased maintenance costs
  • Safety hazards
  • Environmental damage

Corrosion can compromise the integrity of structures and components, leading to potential accidents.

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3
Q

Understand why corrosion occurs

A

Corrosion occurs due to the electrochemical reactions between metals and their environment, often involving moisture, oxygen, and electrolytes.

Factors such as temperature and pH can influence these reactions.

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4
Q

Understand Galvanic series chart: know relative positions of steel, tin, magnesium, aluminum, zinc, platinum & carbon/graphite

A

The Galvanic series chart ranks metals based on their electrochemical activity in a specific environment, with magnesium being most active and platinum least active.

This ranking helps predict corrosion behavior when different metals are in contact.

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5
Q

Explain active/passive, anode/cathode

A
  • Active: Corroding metal that loses electrons
  • Passive: Metal that forms a protective layer
  • Anode: Electrode where oxidation occurs
  • Cathode: Electrode where reduction occurs

Understanding these terms is crucial for analyzing corrosion processes.

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6
Q

Know requirements for corrosion to occur

A
  • Presence of an electrolyte
  • Anode and cathode
  • Electrical connection between anode and cathode
  • Corrosive environment

Without these conditions, corrosion cannot take place.

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7
Q

Define electrolyte

A

An electrolyte is a substance that produces an electrically conducting solution when dissolved in water or another solvent.

Common examples include salts, acids, and bases.

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8
Q

Explain electrochemical corrosion process and galvanic cell

A

The electrochemical corrosion process involves oxidation and reduction reactions in a galvanic cell, where electrons flow from anode to cathode through an external circuit.

This flow of electrons is responsible for the corrosion of metals.

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9
Q

What metallurgical conditions affect corrosion, how and why?

A
  • Alloy composition
  • Microstructure
  • Surface finish
  • Heat treatment

These factors influence the susceptibility of metals to corrosion through changes in their electrochemical properties.

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10
Q

What environments affect corrosion and why?

A
  • Moisture
  • Salinity
  • Temperature
  • pH levels

Different environments can accelerate or inhibit corrosion based on their chemical properties.

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11
Q

How operating conditions can affect corrosion

A
  • Temperature variations
  • Pressure changes
  • Flow rates
  • Chemical exposure

These conditions can alter the rate and type of corrosion experienced by materials.

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12
Q

List types of corrosion as discussed in class – be able to explain

A
  • Uniform corrosion
  • Pitting corrosion
  • Galvanic corrosion
  • Crevice corrosion
  • Stress corrosion cracking

Each type has distinct mechanisms and characteristics that impact material integrity.

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13
Q

Corrosion allowance and corrosion rates – how to use and determine

A

Corrosion allowance is the extra thickness added to materials to account for expected corrosion loss over time, while corrosion rates are measured in mils per year (mpy) to estimate material degradation.

Proper calculations help ensure safety and longevity of structures.

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14
Q

What is the only conditioning you need to know for this test?

A

Stress relieving

No special purpose surface treatments are required.

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15
Q

What microstructures result from hardening steels?

A

Martensite or martensite and cementite

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16
Q

How does carbon content relate to heat treatment results?

A

It defines microstructure in equilibrium or when hardened

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17
Q

What does OQT stand for?

A

OQT

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18
Q

What microstructure does OQT indicate for a low carbon steel?

A

Ferrite and pearlite

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19
Q

What microstructure does OQT indicate for a hypereutectoid steel?

A

Cementite and pearlite

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20
Q

What is a good summary for the heat treatments?

A

Figure 13-33

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21
Q

What do you need to know about the specific alloy contents for the 41xx, 43xx, and 52xxx series?

A

You need to know the specific alloy contents (not percentages) for these series.

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22
Q

What should you be familiar with regarding the groups of steels?

A

You should be familiar with the groups and what their purposes are.

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23
Q

What is carbon equivalency and how does it relate to?

A

Carbon equivalency relates to weldability.

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24
Q

What is HSLA steel?

A

HSLA steel is High-Strength Low-Alloy steel.

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25
What is a weathering steel and what major alloying element does it have?
Weathering steel is a category of steel that has major alloying elements like copper.
26
What heat treating processes should you know and what do they involve?
You should know annealing, hardening, spheroidizing, martempering, austempering, tempering, stress relief, and normalizing.
27
What is the relationship between tempering temperature and hardness?
There is a relationship between tempering temperature and hardness, tensile strength, impact strength, and ductility.
28
What are surfacing hardening methods?
Surfacing hardening methods include flame and induction hardening.
29
What elements can be diffused in diffusion treatments?
Elements that can be diffused include carbon and nitrogen.
30
Define hardenability.
Hardenability refers to the ability of steel to harden in depth when quenched.
31
What affects hardenability?
Factors affecting hardenability include alloy content and cooling rate.
32
What are the carbon content ranges for low, medium, and high carbon steels?
Low carbon: 0.05-0.25%, Medium carbon: 0.25-0.60%, High carbon: 0.60-1.50%.
33
What is the numbering system for plain carbon steels and alloy steels?
The numbering system helps determine carbon content and alloy content.
34
Fill in the blank: The soak time for heat treating processes is ______ per inch of thickness.
one hour
35
True or False: The equilibrium diagram is valid for low alloy steels but may require slow cooling.
True
36
What is grain growth and how is it affected?
Grain growth is affected by heating and cooling rates.
37
What are time temperature transformation curves used for?
They are used to understand phase transformations in steel.
38
What is the importance of table 14-9?
It summarizes material properties based on alloying elements.
39
What is the difference between contact quench and other quenching mediums?
Contact quench involves direct contact with the cooling medium, affecting cooling rates.
40
What are the properties obtained from each heat treating process?
Properties include increased hardness, improved ductility, and reduced residual stresses.
41
What should you review at the end of the chapter?
Summary points and definitions of key terms.
42
Fill in the blank: The carbon content for any series can be determined through the ______.
numbering system
43
What are the categories of tool steels?
Defined by specific alloys and prefixes that indicate their properties ## Footnote Refer to Figure 15-1 and Table 15-1 for detailed classifications.
44
What do the prefixes in tool steel classifications signify?
They indicate specific properties or types of alloys ## Footnote Each prefix corresponds to a certain characteristic of the steel.
45
What do the numbers in tool steel classifications represent?
Specific alloys ## Footnote The numerical designation helps in identifying the composition of the steel.
46
What does Figure 15-2 summarize?
Carbon alloy and tool steels hardening properties ## Footnote It provides a visual representation of the hardening characteristics.
47
What is safety in hardening?
Considerations and practices to prevent accidents during the hardening process ## Footnote Safety protocols are crucial in handling high-temperature processes.
48
What are eutectic structures?
Specific microstructures formed during the solidification of alloys ## Footnote They consist of two or more phases that are in equilibrium.
49
What are eutectic networks?
Networks formed by eutectic structures that can affect material properties ## Footnote They can enhance or diminish the mechanical properties of the steel.
50
What is severe banding?
A phenomenon where there is a pronounced segregation of phases in the microstructure ## Footnote It is undesirable as it can lead to inconsistent mechanical properties.
51
Why are eutectic structures and severe banding undesirable?
They can lead to inconsistent mechanical properties and reduced performance ## Footnote Uniformity in microstructure is essential for predictable behavior.
52
What are the characteristics for hardening and use of tool steels?
Include hardness, toughness, wear resistance, and ability to retain edge ## Footnote These characteristics determine the suitability of tool steels for various applications.
53
What microstructure is produced by hardening 4340 steel?
Martensite ## Footnote Martensite is a hard microstructure formed when steel is rapidly cooled.
54
What phases are present after 52100 steel has been raised above the Ac3, soaked for the appropriate time, then oil quenched?
Austenite and Martensite ## Footnote Austenite transforms to martensite upon rapid cooling.
55
A welded steel structure is raised to 1100 F and held for 1 hour per inch of thickness. What probably is being done to it?
Post-weld heat treatment ## Footnote This process helps to relieve stresses and improve mechanical properties.
56
What is the result of heating a 1020 steel 50 F above the Ac3, soaking for the appropriate time, then furnace cooling?
Fine pearlite ## Footnote Furnace cooling allows for a controlled transformation of austenite into pearlite.
57
When should martempering be used? Austempering?
Martempering is used for high hardenability steels; Austempering is used for medium to low hardenability steels. ## Footnote Martempering reduces distortion; Austempering allows for better toughness.
58
What is the result of spheroidizing a 1090 carbon steel? How would it be done? Why is it done?
Spheroidizing results in a softer, more ductile microstructure. It is done by heating to just below the Ac1 and holding for an extended period. It is done to improve machinability and formability. ## Footnote Spheroidizing helps in preparing steel for further processing.
59
The annealing process includes a furnace cool of the heat-treated part.
True
60
Carbon has the greatest influence on the hardness for high carbon steels.
True
61
The customary heat treating rule is to allow soaking for 1 ½ hours per inch of thickness.
True
62
The grain size immediately above the Ac3 is very small.
False
63
Martensite has a body centered tetragonal structure.
True
64
Induction hardening produces a special martensitic structure that does not require tempering.
True
65
Methane or carbon monoxide may be introduced to a furnace to produce a carburizing atmosphere.
True
66
Tempering requires a part to be heated above the Ac1 and cooled in air.
True
67
High residual stresses can be induced by heat treating, mechanical working, and welding.
True
68
Metallurgical conditions that may inhibit corrosion are inclusions and grain boundaries.
True
69
Interstitial carbon weakens an iron crystal lattice.
False
70
Furnace atmospheres should be controlled to prevent scaling during heat treatment.
True
71
Hardenability is the ability to form martensite.
True
72
Stress relieving is actually a quenching technique.
False
73
Martempering is used to minimize quenching distortion and reduce thermal shock.
True
74
Spheroidizing improves machinability and increases ductility.
True
75
AISI designations for steel include information about carbon content as well as alloy content and type.
True
76
Tool steels are classified by use, such as hot work, shocked, and low speed.
True
77
Sulfur, phosphorus and lead added in recommended ranges improve the machinability of steels.
True
78
Cooling curves indicate the metallurgical structure achieved with various cooling rates.
True
79
HSLA or high strength light additive steels are not normally hardened by heat treating.
True
80
81
Which alloy group produces fine grains, corrosion resistance, and harden-able qualities?
Alloy group with specific elements for desired properties ## Footnote Typically, stainless steels or high alloy steels are selected for these characteristics.
82
What is a characteristic of medium carbon steels?
Moderate strength and hardness with good ductility ## Footnote Medium carbon steels typically contain 0.3% to 0.6% carbon.
83
Which cold work tool steel has 1% carbon?
AISI D2 ## Footnote D2 is commonly used for cold work applications.
84
What will be the structure of a 1060 steel when heated to 1700 F and cooled slowly to room temperature?
Pearlite and ferrite ## Footnote Slow cooling allows for the formation of pearlite in the microstructure.
85
Which steel should not be welded due to problems with cracking?
High carbon steel ## Footnote High carbon steels are prone to cracking during welding due to their hardness.
86
What effects does annealing have on steels?
Increases ductility, reduces hardness, relieves stress ## Footnote Annealing is a heat treatment process used to alter the physical and sometimes chemical properties of a material.
87
Which surface hardening method requires at least 0.40% carbon and uses a water quench?
Case hardening ## Footnote Case hardening processes require specific carbon content for effective hardening.
88
What heat treat process is described for a 1040 steel?
Soak 50-100 F above the Ac3, water quench ## Footnote This treatment is designed to achieve desired mechanical properties.
89
What heat treating process involves heating above the ACM and soaking for thickness, then cooling in air?
Normalizing ## Footnote Normalizing is used to refine grain structure and improve mechanical properties.
90
How does an increase in tempering temperature affect mechanical properties?
Reduces hardness and increases toughness ## Footnote Tempering is a process that alters the properties of hardened steel.
91
Which AISI designation describes a chromium-molybdenum steel with 0.3% carbon?
AISI 4130 ## Footnote AISI 4130 is commonly used in automotive and aerospace applications.
92
Which steel has the highest hardenability?
AISI 4340 ## Footnote AISI 4340 is known for its excellent hardenability.
93
What structure results from soaking a hardenable steel at austenitizing temperature, quenching, and holding in molten salt?
Martensite ## Footnote This process enhances hardness and strength.
94
What is the microstructure of a tool steel in the hardened, non-tempered condition?
Martensite ## Footnote Martensite is a very hard microstructure formed from rapid cooling.
95
What heat treating process involves heating just below the Ac1, soaking for up to 72 hours, and air cooling?
Tempering ## Footnote This method is often used to improve toughness after hardening.
96
What effect does an increase in alloying elements have on a TTT diagram?
Increases the transformation start and finish temperatures ## Footnote More alloying elements can stabilize the austenite phase.
97
What microstructure would a 4140 OQT 1300 steel have?
Tempered martensite ## Footnote OQT indicates oil quenching and tempering processes.
98
Iron nitrides are desirable in surface hardened metals because they ______?
Increase wear resistance ## Footnote Iron nitrides improve the surface hardness and fatigue strength.
99
Which microstructure is produced by austenitizing a 52100 carbon steel then water quenching?
Martensite ## Footnote Water quenching from austenitizing temperature leads to a hard martensitic structure.
100
Which alloying element added to low alloy steels increases toughness and improves hardenability?
Molybdenum ## Footnote Molybdenum enhances the properties of low alloy steels significantly.

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