Lab Assignment: Steel Lab 1

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MATS 322 Steel Lab Assignment 1

Due July 30th at 11:59 PM (Submit through Gradescope)

Name: _____________________________________________________________________

Student ID #: _______________________________________________________________

Please use this file as a template for your HW assignment and write your answers in the blank space after each question.

From Lab For tensile testing, six 1018 steel tensile bars were homogenized at 950°C and then each was subjected to one of the following heat treatments:

• water quenching (WQ) • water quenching followed by a 1 hour anneal at 300°C (WQ + 300) • water quenching followed by a 1 hour anneal at 500°C (WQ + 500) • Oil quenching (OQ) • Air cooling (AC) • Furnace cooling (FC)

1. On the next page is the TTT diagram for 1019 steel, which also works for 1018 steel. This is useful for

determining expected microstructures when cooling from above the eutectoid. Neatly and clearly draw the continuous-cooling path for the steel for each cooling process (WQ, OQ, AC, FC). You will need to estimate as best you can the time to quench to room temperature based on the lab videos.

2. What is the expected microstructure (along with very lax, estimated relative amounts of each component) of

the WQ, OQ, AC, and FC samples?

WQ: ____________________________________________________________

OQ: ____________________________________________________________

AC: ____________________________________________________________

FC: ____________________________________________________________

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3. What phases are expected in the WQ specimens annealed at 300 and 500°C?

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4. How do you expect the microstructure of the annealed 1018 steel bars to vary with temperature? 5. Martensite is on the TTT diagram but is not on the phase diagram of steel. How do you explain the formation

of martensite in steel?

For the following questions use the tensile test data posted along with this assignment on Canvas. The data is for a sample that was Water Quenched and Tempered at 300℃. The data has already been cleaned up for you: the initial non-linear portion removed, the blip from removing the extensometer erased, and the extra data post- fracture at the end of the test wiped from existence. Even the nonsensical data from after the extensometer was removed was totally, and without regret, obliterated.

Here is some information about the dimensions of the sample, measured before and after testing: Average initial diameter in the gauge length, do: 5.83 mm Average final diameter near the fracture, df: 4.34 mm Initial gauge length, Lo: 61.50 mm Final gauge length, Lf: 64.91 mm Attach the following plots to the end of the assignment. The calculations you find will go on the next page. 6. Plot the engineering stress-strain curve. For full credit be to include a descriptive caption and label the plot

axes, the 0.2% yield offset, the ultimate tensile strength (UTS), and final fracture point (𝜎𝜎𝑇𝑇).

7. Plot the true stress-strain curve. For full credit be to include a descriptive caption and label the plot axes, the

0.2% yield offset, the ultimate tensile strength (UTS), and final fracture point (𝜎𝜎𝑇𝑇𝑇𝑇).

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8. What are the main differences between the engineering stress-strain plot and the true-stress strain plot? Why do they occur?

9. For full credit be sure to give your answers using the indicated units!

Calculate the modulus of elasticity, E: _____________ GPa This comes from the slope of the extensometer data. Don’t forget to convert units to GPa!

Calculate the 0.2% Offset Yield Strength, σy: ______________ MPa

This is the intercept between engineering stress-strain plot and 0.2% yield offset plots.

Find the ultimate tensile strength, UTS: _______________ MPa This is the maximum stress on the engineering stress-strain plot.

Calculate the percent elongation: __________________%EL

This is the last point on the corrected engineering stress-strain plot.

Calculate the percent % reduction of area: ______________ %RA Calculate Ao and Af from the diameter measurements and use those to find %RA.

Calculate the toughness (total fracture energy): _______________ MJ/m3

This is found from the area under the true stress/strain plot, make sure the final point of the plot is calculated first! For simplicity, you may assume the plot from the UTS to final point of true stress/strain plot is linear.