Lab Final Exam! Flashcards by Grace Williams

Q

What are the 8 labs done? (define each a little)

A

1) Tensile Testing: test tensile strength
2) Hardness Testing: test surface hardness
3) Impact Testing: hammer tests impact strength
4) Metallography: make sample for inspecting microstructure
5) Jominy Test: test hardenability effects of different alloys
6) Heat Treating: used 3 quench methods for 3 types of cooling
7) Lead-Tin Solidification Diagrams: alternative to Fe3C diagram
8) Pack Carburizing: infuse carbon with pure C and heat in box

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Q

What are the 5 steps for Tensile Testing?

A

Place machined specimen in th tensile tester
Apply tensile load, increasing until sample breaks
During loading, at intervals measure tensile load and measure length
After sample breaks, put broken ends together and measure length
Calculations

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Q

In tensile tesing…

How calculate stress?

A

Force divided by area (F/A)

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Q

In tensile tesing…

How calculate strain?

A

(final length - original length) / (original length)

aka, change in length over original length

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Q

In tensile tesing…

How calculate modulus of elasticity?

A

Stress / Strain

BUT only in straight portoin of graph

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Q

In tensile tesing…

How calculate percent elongation?

A

Final strain x 100

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Q

What term matches this definition?

When the behavior is elastic but not proportional.

A

Proportional Limit

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Q

What term matches this definition?

When the material begins plastic deformation.

A

Yield Strength

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Q

What term matches this definition?

The highest strength achievable.

A

Tensile Strength or Ultimate Tensile Strength (UTS)

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Q

What term matches this definition?

Strength when the material breaks.

A

Breaking strength

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Q

What term matches this definition?

Stretch, related to percent elongation.

A

Ductility

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Q

What term matches this definition?

Measure of stiffness of the material.

A

Modulus of Elasticity

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Q

Define hardness.

A

Measure of metal’s resistance to indentation.

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Q

What are the different types of hardness tests? What’s the difference?

A

Rockwell
Brinell
Vickers

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Q

What are the 5 you need to know about Rockwell hardness testing?

A

1) Minor load: Preplaced load to set indentor
2) Major load: Primary load to determine hardness
3) Indentor: Diamond or ball based on material
4) Notation: HRA, HRB, HRC, HRN, & HRT (pre-# means H value)
5) Setup for different scales: 60, 100, 150, 45, 30 (respective majors)

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Q

Which Rockwell Hardness Test notations are regular or superficial?

A

Regular: HRA, HRB, HRC
Superficial: HRN, HRT

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Q

What is a charpy impact test?

A

A test in which a hammer slams into the middle of a sample that has a V-notch on the other side of the sample to create a high stress point.

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Q

What is the ductile to brittle transition temperature (DBTT)?

What materials experience this?

A

The “S” shaped curve showing a material’s change from ductile to brittle (or vice versa) due to temperature.

BCC materials!

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Q

In a DBTT, what goes of x-axis and y-axis of chart?

A

x-axis: temperature
y-axis: impact strength

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Q

What is the difference between a longitudinal and transverse specimen for impact testing?

A

Longitudinal specimens have grain boundaries that lay long-ways while transverse specimens have grain boundaries in line with where the impact will occur.

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Q

What is potential energy level is the hammer set to prior to an impact test?

A

Maximum potential energy.

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Q

What are the regular mounting press settings for the Metallography lab?

A

1 1/4” mold, 4200 psi

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Q

What are the steps for using the regular mounting press for the Metallography lab?

A

1) Set press mold and psi
2) Relieve pressure before openning
3) Open top of press
4) Turn black knob on front of press toward close arrow
5) Use handle to raise ram
6) Place metal sample face down on ram
7) Slowly open black knob to lower ram
8) close knob when ram is dropped
9) Fill space with 2 scoops of Phenolic or bakelite powder
10) Ensure seal by cleaning surrounding metal
11) Close but do not over tighten (will break it)
12) Raise pressure to just above “preload”
13) Maintain pressure for 1 minute
14) Raise presure to mark matching settings
15) Maintain for seven mintues
16) Release pressure and pump handle to remove sample
17) Allow cool for 8 minutes then put into water

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Q

What do you label a specimen after it has been pressurized from the Metallography lab?

A

Label with section number, material abbreviation, and group letter

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What are the 4 numeric levels of grit on the grinder?

240, 320, 400, & 600

Define **polishing**.

Media is alumnia aka Aluminum Oxide

What are the contents of *etching*?

95% alcohol, 5% nitric acid (nital) with added *acid* | May be used for ferrous materials

# Describe: Gray Cast Iron (GCI)

Ferrite, pearlite, and graphite flakes

# Describe: 1095 Water Quenched and Tempered (1095 WQ&T)

Martensite, ferrite, and cementite

# Describe: 4340 Annealed (4340 A)

Ferrite and pearlite

# Describe: Ductile Cast Iron (DCI)

Ferrite, pearlite, graphite spheroids

# Describe: 4340 Water Quenched (4340 WQ)

Martensite

# Describe: Pig Iron (PI)

Pearlite, cementite, graphite flakes

# Describe: Malleable Cast Iron (MCI)

Ferrite, graphite nodules

# Describe: 1095 Water Quenched (1095 WQ)

Martensite and cementite

# Describe: Spheroidized Martensite

Cementite Spheroids and ferrite

# Describe: Pack Carburized Steel

4 Layers: Inner = 75% ferrite, 25% pearlite 2nd = 75% pearlite, 25% ferrite 3rd = 100% martensite Outer = Martensite and free cementite

Define **Jominy Test**.

Determines effect of alloying elements on microstructure development at different cooling rates - hardnability specifically.

What hardness scale (letter) is used in the Jominy Test?

Scale A

What 3 materials were tested in the Jominy Test lab and their alloys?

1) AISI 1045 (Mn .89) 2) AISI 4140 (Mn .79, Ni 0.01, **Cr 1.01**, Mo 0.22) 3) AISI 4340 (Mn 0.75, **Ni 1.74**, Cr 0.77, Mo 0.30)

Which of te 3 materials had the highest hardenability? Why?

4340 > 4140 > 1045 More alloy means more retain of *interstitial* carbon means more martensite and more hardenability.

What 3 materials were heat treated in the heat treatment lab?

1) AISI 1018 Steel 2) AISI 4140 Steel 3) AISI 52100 Steel

What 3 quench methods were used during the heat treatment lab? (fastest to slowest)

1) Water Quench 2) Oil Quench 3) Air Quench

How did the cooling rates affect the materials' hardness?

The slower the cool, the less hardness is retained. So the slowest, Air Quench, was the softest. The fastest, Water Quench, was the hardest.

What is the heating and cooling process for **annealing**?

Heat to above critcal point, hold (soak) at temperature, then slowly cool.

What is the heating and cooling process for **hardening**?

Heat above upper critical temperature to form austenite, hold (soak) for time, then rapidly cool.

What is the heating and cooling process for **tempering**?

Heat already quenched steel to below critical point, then air cool to relieve internal stresses.

How was the solidification diagram plotted for the Lead Tin lab?

Temperature vs time

Draw the solidification diagram for lead and tin including all 8 components (list them).

1) Liquidus lines and points 2) Solidus lines and points 3) Eutectic 4) Eutectoid 5) Mushy zones 6) Area of liquid 7) Area of solid 8) Undercooling

How is pack carburizing done? (time & temp)

1) Heat sample to 1650 F or let stand for 8 hours 2) Heat to AC3 +50 F (1650 F) for 30 min; air cool (internal uniformity) 3) Heat to AC1,3 + 50 F (1400 F) for 20 min; water quench (casing uniformity)

What 2 alloys can you add to a pack carburizing metal to control *where* the carburizing happens?

Nickel or boron

This process refines grains: Grains become well _ _ _ _ _ _ _ after heating and well _ _ _ _ _ _ _ after cooling.

Refined, organized

What kind of steel was tested during the Cold Work lab?

Austenitic stainless steel (FCC)

As thickness was reduced in the Cold Work lab, what happened to the metal's hardness and magnetism? Why?

Hardness and Magnetism both *increased* because the microstructure is disloacted into a magnetic martensitic structure from the FCC.

What effect did the two cooling rates from water and air have on the hardness after heat treating in the Cold Work lab? Why?

No effect because austenitic will stay austenitic is no phase change so no martensite will form upon cooling at mom-equilibrium rates.

What category of testing is Vickers?

*Hardness* testing of both ferrous and non-ferrous metals.

How is the Vicker's test *different* from the Rockwell test?

The Vicker's uses a **diamond cone indentor**, takes measurments from a microscope, and measures diameter of diamond instead of depth.

What are the 8 steps of conducting a Vicker's hardness test?

1) Place sample under microscope 2) Adjust black knob for resolution 3) Choose HV 1 on screen (1 kg load) 4) Press green button to begin test 5) Find two parallel lines through microscope 6) Fit lines onto shape and record measurements 7) Generate hardness values 8) Use values in calculations

What are D1 and D2 in the Vicker's hardness test?

The two diameters of the square indentation that are averaged to get the actual diameter used in calculations.