This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “Heat Treatment of Steels”.
1. Which of the following alloying element can be used to deoxidize steels?
Explanation: Cerium, calcium, magnesium, manganese and titanium can be used to deoxidise steel.
2. Which of the following processes will one use on hardened steel to reduce brittleness?
Explanation: Tempering is a process of heating to lower critical temperature, then maintaining it at temperature followed by slow cooling to relieve stress and reduce brittleness, increase ductility.
3. Which of the following material in the final structure of steel increases the strength of steel?
Explanation: The amount of martensite remaining in the final structure is correlated with the strength of the steel.
4. Which of the following is defined as the ability of the structure to transform into martensite?
Explanation: Hardenability is defined as the ability of the structure to transform into martensite.
5. Which of the following has the highest hardness number?
b) Tempered martensite
d) Fine pearlite
Explanation: Martensite is the hardest and the most brittle microstructure of steel. It has a higher hardness number than tempered martensite, fine pearlite and pearlite. Tempered martensite is harder than fine pearlite.
6. Jominy end-quench test is used to determine the hardness of a material.
Explanation: Jominy end-quench test is a test used on a material by quenching using a jet of water to determine the hardenability of the material.
7. In a hardnability curve which of the following is true:
a) Hardness increases as distance from quenched end increases
b) Hardness decreases as distance from quenched end increases
c) Hardness increases as martensite decreases
d) Hardenability curve is a straight line
Explanation: In a hardenability curve, which is made by keeping hardness number on y-axis and distance from a quenched end at the x-axis. The hardness number decrease as the distance from the quenched end increases.
8. Which of the following is formed less when cooling rate is decreased?
b) Fine pearlite
Explanation: As the cooling rate decreases with increase of distance from the quenched end, more pearlite and bainite is formed and therefore hardness number decreases.
9. Hardness number decreases with an increase in carbon content in steel.
Explanation: The above statement is false. The hardness number increase with the increase in the carbon content in steel as more martensite is formed with the increase in carbon content.
10. Which of the following statement is false?
a) Greater ratio of surface area to volume, more the hardening effect
b) Cooling is faster in water than oil
c) Spheres cool faster than irregular shaped objects
d) Precipitation hardening can also be called age hardening
Explanation: The statements greater ratio of surface area to volume, more the hardening effect, cooling is faster in water than oil and precipitation hardening can also be called age hardening are true. Spheres cool slower than irregular shaped object.
Sanfoundry Global Education & Learning Series – Materials Science.
To practice all areas of Materials Science, here is complete set of 1000+ Multiple Choice Questions and Answers.