This set of Materials Science Question Bank focuses on “Iron-Carbon Systems”.
1. What is maximum solubility % of carbon and temperature range that α-ferrite exist?
a) 0.05% and 273°c to 910°c
b) 0.025% and 273°c to 910°c
c) 2.1% and 910°c to 1394°c
d) 0.05% and 910°c to 1124°c
View Answer
Explanation: Interstitial solid solution of C in BCC iron. Max solubility of C is 0.025% and it exists from 273°C to 910°C.
2. What is maximum solubility % of carbon and temperature range that Austenite (Ɣ) exist?
a) 0.05% and 273°c to 910°c
b) 0.025% and 273°c to 910°c
c) 2.1% and 910°c to 1394°c
d) 0.09% and 1394°c to 1539°c
View Answer
Explanation: Interstitial solid solution of C in FCC iron has a 2.1% max solubility of C and exists from 910°C – 1394°C.
3. What is maximum solubility % of carbon and temperature range that δ-ferrite exist?
a) 0.05% and 273°c to 910°c
b) 0.025% and 273°c to 910°c
c) 2.1% and 910°c to 1394°c
d) 0.09% and 1394°c to 1539°c
View Answer
Explanation: δ-ferrite (BCC) exists over the temperature range of 1394°C to 1539°C and the maximum solubility of C is 0.09%.
4. What is the % C content in Cementite (Fe3C)?
a) 6.67%
b) 0.025%
c) 2.1%
d) 0.09%
View Answer
Explanation: It is an intermetallic compound. C content in Fe3C is 6.67%.
5. What is the hardest phase of Fe-C system?
a) Graphite
b) Bainite
c) Martensite
d) Cementite
View Answer
Explanation: Cementite is the hardest phase in the Iron-Carbon system whereas martensite is not a phase because it is metastable in nature.
6. What is eutectoid temperature?
a) 727°c
b) 768°c
c) 1146°c
d) 1495°c
View Answer
Explanation: The eutectoid temperature (727°C) during heating and cooling is Ac1 and Ar1 respectively. Eutectoid reaction is a reaction that transforms one solid into two different solids on cooling.
7. At what temperature Fe turns paramagnetic while heating?
a) 727°c
b) 768°c
c) 1146°c
d) 1495°c
View Answer
Explanation: At 768°C. Iron converts from ferromagnetic to paramagnetic and this temperature is known as curie temperature. It is also called as A1 isotherm in iron carbon phase diagram.
8. What is the value of eutectic temperature?
a) 727°c
b) 768°c
c) 1146°c
d) 1495°c
View Answer
Explanation: The eutectic temperature for Fe-C system is 1146°C. The eutectic reaction is a reaction that transforms one liquid phase into two solid phases on cooling.
9. What is the value of peritectic temperature?
a) 727°c
b) 768°c
c) 1146°c
d) 1495°c
View Answer
Explanation: The peritectic temperature is at 1495°C for the Fe-C system. The peritectic reaction is a reaction that transforms one liquid and solid to another solid on cooling.
10. Carbon steel containing 9,1% ferrite is cooled from the region of austenitic (727 °c). What is the percentage C content in the steel?
a) 0.05% C
b) 0.1% C
c) 0.2% C
d) 0.3% C
View Answer
Explanation: Let c be Carbon content. Applying the lever rule
0.091 = (6.67 – c)/(6.67 – 0.025)
c = 0.1% C.
Sanfoundry Global Education & Learning Series – Materials Science.
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