This set of Heat Treatment of Metals and Alloys Multiple Choice Questions & Answers (MCQs) focuses on “Steels Processes – Stress Relieving”.
1. What is the purpose of stress relieving?
a) To increase internal stresses
b) To reduce internal stresses
c) For structural improvements
d) To increases the brittleness
View Answer
Explanation: The main purpose of stress relieving is to reduce internal stresses. This helps in reducing brittleness and improves ductility and machinability.
2. Which one of the following operations does not develop internal stresses?
a) Cold working
b) Shot peening
c) Welding
d) Cutting
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Explanation: Internal stresses are generated in steels by different processes like solidification, machining, cold working, welding, shot peening, phase transformation, etc. Internal stresses are not developed during cutting process.
3. Which one of the following statements is correct?
a) Microstructural changes occur during stress relieving
b) No microstructural change occur during stress relieving
c) Internal stresses improve ductility
d) Internal stresses decrease brittleness
View Answer
Explanation: During stress relieving, no microstructural changes take place. Due to presence of internal stresses, ductility decreases and brittleness increases.
4. Retained austenite has greater dislocation density than original austenite.
a) True
b) False
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Explanation: Retained austenite has greater dislocation density than original austenite. They also have higher imperfections which can be attributed to the localized deformation of retained austenite.
5. Which one of the following statements is correct?
a) Presence of internal stress improves fatigue strength
b) Presence of internal stress avoids fatigue failure
c) Presence of internal stress reduces fatigue strength
d) Presence of internal stress improves ductility
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Explanation: Presence of internal stresses affects the fatigue strength of material adversely. It reduces the fatigue strength greatly. Their effect is more adverse in case of brittle materials than ductile materials.
6. Which one of the following statements is incorrect?
a) Presence of internal stress improves dimensional stability
b) Presence of internal stress leads to stress corrosion cracking
c) Presence of internal stress enhance the tendency of steel towards warpage
d) Presence of internal stress enhance the tendency of steel towards dimensional instability
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Explanation: Presence of residual stresses is not desirable. Presence of internal stress enhances the tendency of steel towards dimensional instability and warpage. Steels with residual stresses under corrosive environment undergo stress corrosion cracking.
7. Which one of the following statements is correct regarding stress relieving?
a) Heating of steel is done above upper critical temperature
b) Heating of steel is done between upper and lower critical temperature
c) Heating of steel is done below lower critical temperature
d) Heating of steel is done once above upper critical temperature and then below lower critical temperature
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Explanation: During stress relieving, steel is heated to a temperature below lower critical temperature. It is then followed by holding at this temperature for sufficient time.
8. During stress relieving non uniform cooling is done.
a) True
b) False
View Answer
Explanation: During stress relieving, steel is heated below lower critical temperature which is followed by holding at this temperature then uniform cooling is done. Uniform cooling is very important as non-uniform cooling will itself generate stresses.
9. For grey cast iron, what is the temperature range for stress relieving?
a) 600-650°C
b) 400-450°C
c) 538-590°C
d) 460-510°C
View Answer
Explanation: For grey cast iron the recommended temperature range for stress relieving is 538-590°C. In the temperature range of 538-565°c about 80% of the residual stresses are removed. When heated at 590°C 85% of stresses can be relieved.
Sanfoundry Global Education & Learning Series – Heat Treatment of Metals and Alloys.
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