This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Annealing – 11”.
1. For which of the following purposes, annealing is not done?
c) Stress relieving
d) Decreasing brittleness
Explanation: Annealing refers to a wide group of heat treatment processes and is performed primarily for homogenization, recrystallization or relief of residual stress in typical cold worked or welded components.
2. Depending upon the ______ under which it is performed, annealing eliminates chemical or physical non-homogeneity.
a) humidity conditions
b) temperature conditions
d) weight of the component
Explanation: Depending upon the temperature conditions under which it is performed, annealing eliminates chemical or physical non-homogeneity produced of phase transformations.
3. How many types of annealing are there?
Explanation: Few important variants of annealing are;
• full annealing
• isothermal annealing
• spheroidise annealing
• recrystallization annealing
• stress relief annealing.
4. In case of full annealing of hypo-eutectoid steels, it is heated to a temperature _____
a) above upper critical temperature
b) above lower critical temperature
c) to a critical temperature
d) recrystallization temperature
Explanation: The steel component to above upper critical temperature of ferrite for hypoeutectoid steels and above lower critical temperature for hypereutectoid steels by 30-50⁰C.
5. During full annealing of steel, the component needs to be held above lower or higher critical temperature for _____ per cm of the thickness.
a) 5 min
b) 13 min
c) 20 min
d) 25 min
Explanation: The steel component to above upper critical temperature for a definite holding (soaking) period of at least 20 minutes per cm of the thick section to assure equalization of temperature throughout the cross-section of the component and complete austenization.
6. In the final stage of full annealing, a steel component is cooled _____
a) rapidly using jet of water
b) using blast of liquid which a mixture of water and some anti-corrosion powder
c) slowly in the furnace
d) slowly in air
Explanation: The final step in the full annealing of steel, is to cool the hot steel component to room temperature slowly in the furnace, which is also called furnace cooling. Rapid cooling is done in the quenching process.
7. The full annealing is used to _____
a) increase the hardness
b) to decrease ductility
c) to refine the grain structure
d) to decrease machinability
Explanation: The full annealing is used to relieve the internal stresses induced due to cold working, welding, etc., to reduce hardness and increase ductility, to refine the grain structure, to make the material homogenous in respect of chemical composition, to increase the uniformity of phase distribution, and to increase machinability.
8. Iso thermal annealing is done in _____ steps.
Explanation: Isothermal annealing consists of four steps. The first step is heating the steel components similar as in the case of full annealing. The second step is slightly fast cooling from the usual austenitizing temperature to a constant temperature just below A1. The third step is to hold at this reduced temperature for sufficient soaking period for the completion of transformation and the final step involves cooling the steel component to room temperature in air.
9. Isothermal annealing requires less time than that for full annealing.
Explanation: Due to isothermal annealing, the annealing time is reduced especially for alloy steels which need very slow cooling to obtain the required reduction in hardness by the full annealing. Also, more homogeneity in a structure is obtained as the transformation occurs at the same time throughout the cross section.
10. Isothermal annealing is primarily used for _____
a) high carbon steels
b) low carbon steels
c) aluminium alloy
Explanation: Isothermal annealing is primarily used for medium carbon, high carbon and some of the alloy steels. Due to this Improved machinability and surface finish is obtained after machining as compared to that of the full annealed components.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
To practice all areas of Manufacturing Processes, here is complete set of 1000+ Multiple Choice Questions and Answers.