Engineering Materials and Metallurgy Questions and Answers – Interrupted Quenching

This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Interrupted Quenching”.

1. Quenching of austenite steel for martempering is done using __________
a) Furnace
b) Still air
c) Cooling tower
d) Hot oil
View Answer

Answer: d
Explanation: For martempering, the steel is first heated above its critical range to make it austenitic. Then it is quenched in hot oil or molten salt above martensite start temperature.

2. How can temperature differences between center and surface be prevented?
a) Refined grain structure
b) Cooling to room temperature
c) Hot working
d) Addition of silicon
View Answer

Answer: b
Explanation: Cooling the steel at moderate to room temperature prevents temperature differences between center and surface. This is usually done in air. The resulting microstructure of martempered steel is untempered martensite.

3. Martempering process is usually employed in _________
a) Alloy steels
b) Cast irons
c) Composites
d) Ceramics
View Answer

Answer: a
Explanation: Martempering is an interrupted quenching process which eliminates some disadvantages of rapid cooling. It is used to minimize stresses, distortion, and cracking of steels. This process is usually used in alloy steels.

4. Martempering is otherwise known as __________
a) Interrupted quenching
b) Marquenching
c) Austempering
d) Isothermal quenching
View Answer

Answer: b
Explanation: Interrupted quenching is a technique of eliminating the disadvantages caused by rapid cooling. This consists of two methods, martempering and austempering. Martempering is also known as marquenching, and austempering is also known as isothermal quenching.

5. Austempering forms a _________ structure.
a) Pearlite
b) Bainite
c) Spherodite
d) Cementite
View Answer

Answer: b
Explanation: Austempering is an isothermal heat treatment process used to reduce distortion caused by quenching and to make tough and strong steels. It forms a bainite structure and is otherwise known as isothermal quenching.
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6. It is necessary to carry out _________ after martempering.
a) Refining
b) Tempering
c) Surface hardening
d) Cyaniding
View Answer

Answer: b
Explanation: Untempered martensite structure is transformed into tempered martensite structure by conventional tempering heat treatment processing rapid quenching. This is rarely needed in austempering.

7. Which of the following is not a disadvantage of austempering?
a) Needs to be cold worked
b) Needs special bath
c) Can be used for limited steels
d) Can only be used for small sections
View Answer

Answer: a
Explanation: Austempering experiences a number of disadvantages compared to quenching and tempering. It needs a special molten salt bath and can be used only for a limited number of steels. Furthermore, only small sections up to 9 mm thickness can be used.

8. Why are bigger sections not used in austempering?
a) Unable to cool
b) Does not fit in the working apparatus
c) Decreased strength
d) Cannot be cut
View Answer

Answer: a
Explanation: Big sections cannot be used for austempering as they cannot be cooled rapidly to avoid the formation of pearlite. As a result, only small sections up to 9 mm thickness are suitable for this operation.

Sanfoundry Global Education & Learning Series – Engineering Materials & Metallurgy.


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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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