Homework assignments are given below.
Please see the course schedule
and/or announcements
for due dates and other relevant information.
(Scope: Ch.1, 2, Notes I,II)
1. The SAE designation 10XX indicates a plain carbon steel.
What is indicated by the designation if the first two numbers are:
(a) 11 ______________________________________
(b) 12 ______________________________________
(c) 15 ______________________________________
2. Ferrous alloys with up to 2% carbon are commonly termed _________________________ , while alloys with higher carbon content are termed ______________________________.
3. What are the two essential conditions for smelting a metal from its ore?
4. Large-scale modern smelting of iron is most commonly performed in a reactor known as a ___________________________ . In this process, the vessel is charged with __________________ , __________________ , and __________________ , and injected with hot _______________ .
5. The product of this reactor is a rather impure iron, known as “hot metal” or “ ________ iron”.
6. List the five principal impurity elements found in iron produced in this reactor.
7. The process of steelmaking involves removal of a large amount of the impurities above. List four steelmaking processes.
8. Make a table and list the composition and typical values for yield strength,
tensile strength, hardness, elongation, and fracture toughness for each the following materials.
Please list all references completely.
• 1018, 1045, 1075 plain carbon steels
• 4130, 4140, 4340, 5210, 8620 alloy steels
• M1, T1, and H10 Tool steels
• 18Ni(350) Maraging Steel
• 304, 430, 410, and 17-4PH stainless steels
9. Plot (i) tensile strength vs elongation and (ii) tensile strength vs fracture toughness. Label each data point. State any observed trends regarding composition and properties
(Scope: Krauss Ch.3,4,9; Course Notes Ch.4-6)
1. (a)Compute the weight percent of carbon in austenite if all of octahedral sites are occupied by a carbon atom. (b) Compute the weight percent of carbon in ferrite if all similarly aligned octahedral sites are occupied by a carbon atom.
2. Write the most common slip systems for (a) ferrite and (b) austenite.
3. Why is the Ar1 always lower than the Ac1,with the A1 between the two? Determine the Ac1 and Ac3 for a 4340 steel (use Eqs. 3.3 and 3.4).
4. Classify each of the following elements as either an austenite stabilizer or ferrite stabilizer: C, Cr, Mn, Mo, Ni, Si, Ti, W.
5. What is the difference between indigenous and exogenous inclusions?
6. Compare killed, capped, and rimmed steel in terms of surface finish and chemical homogeneity. What steel compositions and/or applications are each of these typically used for?
7. If a steel has 0.040 wt% S, how much Mn is required to combine with all of the contained sulfur?
8. Compute the microsegregation profile you might expect to see after solidification of a 1020 steel. Assume this persists upon cooling through the austenite regime. How might this influence the room temperature micorstructure?
9. Define and distinguish between plate, sheet, and strip, as related to steel product forms.
10. Describe the purpose/effect of Cu, B, Al, Mo, and Cr additions in steels.
(Scope: Krauss Ch.5,6,10,17,19)
1. Make a scale (computer) drawing to show the crystal structure of ferrite, austenite,
and martensite. For each structure, show at least four unit cells and (an example of) the location of the carbon atoms.
2. Use a 3D (computer) sketch to show the relationship between the parent austenite
and martensite crystal structures. On your sketch, clearly show that the Kurdjumov-Sachs
orientation relationship holds.
3. Plot the Ms temperature as a function of carbon content. Estimate and
plot (on the same axes) curves to show the temperature required for 25%,
50%, 75%, and 95% martensite.
4. Briefly compare and contrast lath and plate martensites in terms of structure
and growth mechanisms. Briefly discuss the factors that favor one type over the other.
5. While bainite formation clearly has characteristics of a diffusive transformation,
it exhibits some athermal characteristics. Describe this athermal character and discuss
its cause.
6. Describe upper and lower bainite, pointing out their primary differences in
terms of both microstructure and growth mechanisms.
7. Plot the "martensite start" and "bainite start" temperatures as a function of composition
by superimposing them on the phase diagram.
8. What alloying additions promote bainite formation and result in "bainitic steels"?
What is the advantage of using a bainitic steel. Indentify one bainitic steel alloy and
application. Give the composition, alloy name/number, and describe its principal use(s).
(PLEASE DO YOUR OWN WORK)
9. Use the CT diagram for 1038 steel in Fig.10.10 to determine:
(a) the critical diameter
for this steel upon (i) oil quenching and (ii) air cooling;
(b) the range of diameters
that will give 100% bainite at the center of an air-cooled round bar.
10. Use Figs. 16.18-16.21 along with Table 16.2 to determine:
(a) the critical diameter for 1045 steel in a water quench with violent circulation, where
the average grain diameter is 30 microns;
(b) the required quench severity (H-value) to give thru-hardening in a 0.25-inch diameter
bar of 1080 steel with the same grain size(as in (a));
(c) the required H-value to give thru-hardening of a 4140 steel bar of
diameter 0.75 inches.
