Heat Treatment of Steel



Reports must conform to the following format:

Title Page
Standard format from lab manual.

Abstract
For each of the heat treatments, please list values for yield strength, ultimate tensile strength, hardness, and elongation. In addition, please include hardness data for the quenched sample.

Introduction
Please describe the importance of understanding the iron-carbon phase diagram. Why is the heat treatment of steel important both technologically and historically?

Results
1. Please prepare engineering stress-strain diagrams for each of the following heat treatments
a. as-received
b. quenched and tempered
c. annealed
Make sure tin include properly labeled axes and titles on the plots. Use ink for any hand drawn plots.

2. Present tables for each of the heat treatments tested for which the data is available. Include yield strength, ultimate tensile strength, hardness, and elongation. Make sure to include the appropriate units and scales for the data presented. Please see attached sheet for table format and information to include. Please include data for each of the boxes with an X in it.

Heat Treatment of 4140 Steel
Property
As-Received
Annealed
Quenched
Quenched and Tempered
Exp. Yield Strength (psi)
X
X
  
X
Lit. Yield Strength (psi)
  
X
  
X
Percent Difference in Yield Strength (%)
  
X
  
X
Exp. Ultimate Tensile Strength (psi)
X
X
  
X
Lit. Ultimate Tensile Strength (psi)
  
X
  
X
Percent Difference in UTS (%)
  
X
  
X
Exp. Hardness
X (include scale)
X (include scale)
X (include scale)
X (include scale)
Lit. Hardness
  
X (include scale)
X (include scale)
X (include scale)
Hardness Difference
  
X (number difference)
X (number difference)
X (number difference)
Exp. Elongation(%)
X
X
  
X
Lit. Elongation (%)
  
X
  
X
Elongation difference (%)
  
X
  
X

Discussion
Please answer the following questions in this section
1. What phases produced the hardest material?

2. a. What is the minimum temperature needed for the hardening heat treatment of a 1020 steel?
b. How did you select this temperature?

3. From the hardness data obtained for the as-quenched 4140 sample, use the chart on page 328 of your test to find the cooling rate for the sample as it cooled through 700 °C. What is this value?

4. Samples of 4140 and 1040 have been quenched and tempered identically. The inside of the 1040 sample has a different microstructure from its surface. The 4140 sample has the same micro structure on the inside as well as the outside. Please explain why this has happened.

5. You are asked to produce a high precision, steel shaft. Beginning with an as-received sample, place the following processing steps in the correct order. Use each step only once. After each step, place a relative hardness value (low, moderate, high) indicating the hardness of the material following the step. For instance: tempering, moderate hardness.

tempering
bulk material removal (turning)
heating for hardening
surface grinding
quenching

6. Why would you not want a high material hardness during bulk material removal?

Conclusions:
Please include the answers to the following questions in this section:
1. What were the trends that you saw with the heat treatment of the steel?
2. Which phases produced the hardest material?
3. What did tempering do to the hardness of the as-quenched sample?

References
Please include the references that you used to find the literature data for your tables.

Appendix
Original data sheets.
Sample calculations of % elongation, strain at failure