Metal 259 - Fall-1995 - Exam 2

Par time - 14 min. (Time required to read questions and write answers)

Only answers placed in the space provided will be considered.
Diagrams and drawings, where appropriate, are welcome.

1. (0) Put your social security no. on the line above now.

2. (6) Classify the materials in the composition regions below.

3. (6) List the phases present at equilibrium at room temperature in the composition regions below.

4. (10) Discuss the difference in mechanical properties of two 1080 steel bars, previously at equilibrium, that are heated to 800°C and 675°C and quenched in water. Give the reasons for the difference.

5. (10) Discuss the difference in mechanical properties of two 1040 steel bars, previously at equilibrium, that are heated to 800°C and 900°C and quenched in agitated ice brine. Give the reasons for the difference.

6. (12) It is desired to harden a 1" dia. 8645 shaft to a depth of 0.10" to obtain maximum wear resistance at the surface. Specify the approximate austenitizing temperature and the quenching medium, and suggest tempering temperature and time. Show your work.

7. (6) What class of stainless steels would you choose for the manufacture of chemical laboratory sinks? Why are the other types probably not suitable?

8. (10) Discuss briefly the reason for the spectacular difference in the mechanical properties of ordinary grey cast irons and nodular cast irons?

9. (10) From the curves below for a 1080 steel, what phase or phases is/are the product of the heat treatment?

10. (10) From the curves below for a 1080 steel, what phase or phases is/are the product of the heat treatment?

11. (10)

a. Why is untempered martensite so brittle?

b. Why is tempered martensite not brittle?

12. (10) List and describe three methods for the case hardening of steels.