1. Why are metals heat-treated ?
2. Identify the important reasons why metals are annealed.
3. What is the most important heat treatment for hardening steels?
4. What is the mechanism by which carbon strengthens steel during heat treatment?
5. What information is conveyed by the TTT curve?
6. What function is served by tempering?
7. Define hardenability?
8. Name some of the elements which have the greatest effect on the hardenability of steel.
9. Indicate how the hardenability alloying elements in steel affect the TTT curve.
10. Define precipitation hardening?
11. How does carburizing work?
12. Identify the selective surface hardening methods.
13. Which of the following are the usual objectives of heat treatment (three best answers):
(a) increase hardness,
(b) increase melting temperature,
(c) increase recrystallization temperature,
(d) reduce brittleness,
(e) reduce density, and
(f) relieve stresses?
14. Of the following quenching media, which one produces the most rapid cooling rate:
(a) air,
(b) brine,
(c) oil, or
(d) pure water?
15. On which one of the following metals is the treatment called austenitizing be performed:
(a) aluminum alloys,
(b) brass,
(c) copper alloys, or
(d) steel?
16. The treatment in which the brittleness of martensite is reduced is called which one of the following:
(a) aging,
(b) annealing,
(c) austenitizing,
(d) normalizing,
(e) quenching, or
(f) tempering?
17. The Jominy end quench test is designed to indicate which one of the following:
(a) cooling rate,
(b) ductility,
(c) hardenability,
(d) hardness, or
(e) strength?
18. In precipitation hardening, the hardening and strengthening of the metal occurs in which one of the following steps:
(a) aging,
(b) quenching, or
(c) solution treatment?
19. Which one of the following surface hardening treatments is the most common?
(a) boronizing,
(b) carbonitriding,
(c) carburizing,
(d) chromizing, or
(e) nitriding.
20. Which of the following are selective surface hardening methods (three correct answers):
(a) austenitizing,
(b) electron beam heating,
(c) fluidized bed furnaces,
(d) induction heating,
(e) laser beam heating, and
(f) vacuum furnaces?
21. How much time is required for austenite to transform to 50% C ?°pearlite at 600
22. Calculate the microstructure of a 0.77 wt% C steel that has the following heat treatment ga) instantly quenched from the C°region to 500 b) held for 5 s C.°c) quenched instantly to 250
23. C and°What will happen if the resulting microstructure is held for 1 day at 250 then cooled to room temperature ?
24. Estimate the quench rate needed to avoid pearite formation in a) 0.5 wt% C steel b) 0.77 wt% C steel c) 1.13 wt% C steel C°
25. Calculate the time required for austempering at 5 above the Ms temperature for a) 0.5 wt% C steel b) 0.77 wt % C steel c) 1.13 wt % C steel
