Exam II Review Sheet Flashcards by Grace Williams

Define Corrosion

The deterioration of a material or its properties because of reaction with its environment.

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List and explain problems caused by corrosion

That’s stupid. Don’t answer that.

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Why does corrosion occur?

What is one of the only metals found as a metal (not made) in nature?

Occurs in metals because most metals are not in their natural state until they return to the ore form (via corrosion) in which we found them.

Gold! Fun fact

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Table 6-1

What are the relative positions of steel, tin, magnesium, aluminum, zinc, platinum, carbon, and graphite on galvanic series chart?

Mg (tippy top)
Zn (numero 2)
Al (4, after galvenized steel)
Low Carb Steel -> CastIron -> Stainless
Sb (more mid, still high)
Zn, Cu, Ni alloys (low mid)
Passive stainlesses
Au, Ti (second, third last)
Platinum (dead last)

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Explain active/passive and anode/cathode

Passivity: a surface condition that inhibits electrochemical action between the metal and its environment. Occurs when metal in environemnt known for being aggressive to that metal is not attacked. The formation of a protective film.

Protective part = anode, Protected part = cathode

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What are the requirements for corrosion to occur?

Anode, cathode, electrical current, potentiall difference, and electrolyte.

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Define electrolyte

Solutions containing dissolved ions.

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Explain electrochemical corrosion process and galvanic cell.

Basically, the exchange of ions between an anion and a cation vis oxidation and reduction processes. A galvanic cell is a battery example of this ion exchange.

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What metallurigal conditions affect corrosion and why?

1) Chemical segregation
2) Presence of multiple phases
3) Inclusions
4) Cold work
5) Nonuniform stresses

Because they create anodic areas!

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How do operating conditions affect corrosion?

As these _ _ _ _, corrosion increases:
1) Intended service life (inc)
2) Temperature (inc)
3) Velocity (inc)
4) Concentration (inc)
5) Impurities (inc)
6) Aeration (only one that affects corrosion depending)

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What are the 8 types of corrosion?

1) Uniform
2) Pitting
3) Crevice
4) Galvanic
5) Stress Corrosion Cracking
6) Intergranular attack
7) Dealloying
8) Erosion

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Define uniform corrosion.

All surfaces exposed to corrodent corrode uniformly.

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Define pitting corrosion.

Local corrosion damage characterized by surface cavities.

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Define crevice corrosion.

A local attack in a crevice between metal to metal surfaces or between metal to nonmetal surfaces.

One side of crevice must be exposed to corrodent (stick out).

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Define galvanic corrosion.

When two dissimilar metals are electrically connected, one become an anode and beginsto corrode by galvanic cell action.

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Define stress corrosion cracking.

Spontaneous corrosion-induced cracking of a material under static stress, either applied or residual.

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Define intergranular attack corrosion.

Occurs at grain boundaries. Caused by alloy segregation at grain boundaries and grain boundaries become chemically dissimilar to the actual grain itself.

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Define dealloying corrosion.

One constituent of metal alloy is preferentially removd from the alloy, leaving an altered residual microstructure.

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Define erosion.

Wear from environmental factors.

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List and explain the 4 types of erosion.

1) Liquid Impingement: material removal due to the action of an impinging stream or droplets of fluid (can be gas or liquid).
2) Liquid Erosion: Like impingement, but liquid attack is perpendicular to metal from high velocity. (know cuz grooves in material)
3) Slurry Erosion: material removal due to the combined action of corrosion and wear from abrasives particles.
4) Cavitation Erosion: material removal by teh action of imploding bubbles. (Ti has best resistance to this).

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How to use and determine corrosion allowance and corrosion rates.

Corrosion Allowance is material added to lengthen life of material despite corrosion and is determined by corrosion rates which are determined by simple immersion tests.

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Define stress relieving.

Achieves dimensional stability (good for machine parts for design engineers) and is preferable to normalizing and annealing. Usually 100-200 degrees F below the transformation temperature.

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What is the result composition of hardening steels?

If happen fast enough, is martensite. If slow, return to original stuff.

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What is OQT? What microstructure does this indicate for a low carbon steel and hypereutectoid steel?

Optimal Quenching Temperature (temp above AC3). Indicates BCT for low carbon steel and cementite for hypereutectoid.

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What alloy is contained in 41xx series?

Molybdenum

What alloy is contained in 43xx series?

Chro-moly

What alloy is contained in 52xx series?

High chromium

What alloy is contained in 10xx series?

Carbon

What alloy is contained in 11xx series?

Resulfurized carbon | Also kinda maybe phosphurous? (NO WELD)

How do you know carbon content in a metal based on its series number?

The last 2 or 3 digits of the number give the *points* of carbon that te metal has.

# Table 14-9 Aluminum (<2%) | Chemical Symbol:

- aids nitriding - restrict grain growth - remove oxygen in steel making | Al

# Table 14-9 Sulfur and phosphorous (<0.5%) | Chemical Symbol:

- adds machinability - reduces weldability, ductility, and toughness | S and P

# Table 14-9 Chromium (0.3-4%) | Chemical Symbol:

- increases oxidation/corrosion resistance - increases hardenability (a lot) - increases high-temperature strength (HSS) - can combine w/ carbon to form hard, wear resistant microconstituents | Cr

# Table 14-9 Nickel (0.3-5%) | Chemical Symbol:

- promotes an austenitic structure (FCC) - increases hardenability (a little) - increases toughness | Ni

# Table 14-9 Copper (0.2-0.5%) | Chemical Symbol:

- promotes tenacious oxide film to aid atmospheric corrosion resistance | Cu

# Table 14-9 Manganese (0.3-2%) | Chemical Symbol:

- increases hardenability, lowers hardening temperature - promotes an austenitic structure (FCC) - combines with sulfur to reduce its adverse effects | Mn

# Table 14-9 Silicon (0.2-2.5%) | Chemical Symbol:

- removes oxygen in steelmaking - improves toughness - increases hardenability | Si

# Table 14-9 Molybdenum (0.1-0.5%) | Chemical Symbol:

- promotes grain refinement - increases hardenability - improves high temperature strength | Mo

# Table 14-9 Vanadium (0.1-0.3%) | Chemical Symbol:

- promotes grain refinement - increases hardenability - will combine with carbon to form wear-resistant microconstituents | V

# Table 14-9 Boron (0.0005-0.003%) | Chemical Symbol:

- added in small amounts to form wear-resistant microconstituents | B

# Table 14-9 Lead (<0.3%) | Chemical Symbol:

- added only to aid machinability | Pb

# Table 14-9 Nitrogen (<0.1%) | Chemical Symbol:

- acts like carbon in strengthening | N

What is **carbon equivalency** (CE)?

It is a general equation used to predict cracking in welding or weldability of a material by multiplying each alloy by a specific ratio reflecting that alloy's effect on hardening. | Higher CE == bad welding. Lower CE == good for welding!

What is an SAE designation number?

The number that categorizes a metal with numbers that describe its alloys and carbon content. | Preferred system in US, as opposed to ASTM.

If SAE steels are mostly for machine design, structural steel is covered by what other specification?

ASTM

What ASTM specification refers to SAE designations?

**ASTM A 29** grade "SAE designation"

What is the UNS designation for SAE specifications?

**G** ##xx**0**

Harder tempers make it so functionability can be maintained with less material.What does this mean for harder tempers and money in relationship?

Harder tempers == less money spend

What type of finishing (hot or cold) is cheaper and is more stable in machining?

Hot, BUT has poorer surface finish than cold.

What is the difference between hardenability and hardness?

**Hardenability**: the ease with which a material can be hardened. **Hardness**: simply the degree of hardness

Section thickness has a profound effect on the ability of a piece of steel to _ _ _ _ _ . When a section is thicker than **0.5 in**, we should start to consider a material's _ _ _ _ _ _ _ .

Harden! Hardenability!

Define austenitizing.

Heating a steel hot enough to transform room temperature structures in steel to austenite.

Define case hardening.

Hardening just the surface of a steel

Define cold rolled.

Steel rolled at room temperature

Define core properties.

The attributes (strength, hardness) of the substrates of a case hardened steel.

Define dual phase.

A metal with a second phase in a host phase. | Like ferrite with martensite islands.

Define formability.

The ease and chances of success (no failures) in bending and drawing, etc.

Define free-machining.

Metas containing additives to facilitate chip formation and improve tool life.

Define hardness traverse.

The process of taking microhardness readings in small increments inward from a casehardened surface.

Define HSLA steels.

Steels with alloy additions that strengthen withour the need for customer heat treatment.

Define jominy.

A steel hardenability test in which the end of a heated bar is water quenched.

Define mill-heat treated steel.

Steel that is already hardened when purchased from the manufacturer.

Define ultra-high-strength steel.

Steel with yield strengths greater tan 250,000 psi

Define weathering steel. | What steel category does it fall under?

Steel with copper additions to promote the formation of a tenacious oxide when exposed outdoors. | Falls under HSLA steel!

What is HSLA?

**High-Strength Low-Alloy Steel**: a type of carbon steel enhanced with small amounts of alloying elements to increase strength, toughness, and potentially corrosion resistance, making it suitable for applications requiring a good strength-to-weight ratio.

What is B steel?

Alloy steels with **boron** desginated in SAE with xx**B**xx or in UNS as "G xxxx1".

What is H steel?

Alloy steels with *guaranteed* hardening characteristics. Usually having 40 points of carbon.

# Which heat treating process is defined below? 1) Temperature raised to: 2) Soaktime: 3) Method of cooling: Slow cooling 4) Gained properties: 5) Why:

Annealing