This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Transformation of Steel and Cast Iron”.
1. Composition up to 0.008% carbon is considered as _________
a) Pure iron
b) Steel
c) Cast iron
d) Annealed steel
View Answer
Explanation: In general, the different types of ferrous alloys are steel, iron, and cast iron. Pure iron is composed of 0.008% carbon, whereas steel and cast iron contain 0.008-2.0% and over 2% respectively.
2. Steels containing 0.8% C are called ________
a) Eutectoid
b) Hypoeutectoid
c) Hypereutectoid
d) Mild eutectoid
View Answer
Explanation: In general, the different types of ferrous alloys are steel, iron, and cast iron. Steels are further subdivided as eutectoid, hypoeutectoid, and hypereutectoid. Eutectoid steels contain 0.8% of carbon content.
3. How much carbon does hypoeutectoid steel contain?
a) <0.8%
b) 0.8%
c) >0.8%
d) 8%
View Answer
Explanation: In general, the different types of ferrous alloys are steel, iron, and cast iron. Steels are further subdivided as eutectoid, hypoeutectoid, and hypereutectoid. Hypoeutectoid steels contain less than 0.8% of carbon content, whereas hypereutectoid steels contain over 0.8%.
4. Eutectoid steel is heated at __________
a) 150oC
b) 450oC
c) 750oC
d) 950oC
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Explanation: For the transformation of eutectoid steel, a sample of 0.8% steel is heated at 750oC. It is held at this temperature until a transformation begins.
5. Transformation in eutectoid steels is named as _________
a) Austenitizing
b) Carburizing
c) Decarburizing
d) Nitriding
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Explanation: For the transformation of eutectoid steel, a sample of 0.8% steel is heated at 750oC and held at that temperature. Due to this, the structure becomes homogeneous austenite. This process is known as austenitizing.
6. Cooling of hypoeutectoid steel post heating forms __________ ferrite.
a) Proeutectoid
b) Posteutectoid
c) Hypereutectoid 2.08%
d) Mild eutectoid
View Answer
Explanation: 0.022-0.8% carbon steel is heated at around 875oC and held at this temperature. This results in the formation of homogeneous austenite. Then the steel is cooled to about 775oC, due to which pro-eutectoid ferrite will nucleate and grow at austenite grain boundaries.
7. Slow cooling of hypereutectoid steel results in formation of __________
a) Proeutectoid cementite
b) Posteutectoid cementite
c) Proeutectoid ferrite
d) Proeutectoid austenite
View Answer
Explanation: Over 0.8% carbon steel is heated at around 925oC and held at this temperature. This results in the formation of austenite. Then the steel is slowly cooled to form proeutectoid cementite which will nucleate and grow at austenite grain boundaries.
8. A mixture of austenite and cementite is called ___________
a) Ferrite
b) Ledeburite
c) Pearlite
d) Bainite
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Explanation: Slow cooling of eutectic cast iron leads to precipitation of austenite of cementite. This combination of austenite and cementite is called ledeburite. This reaction occurs at 1148oC.
9. Cooling of austenite of eutectoid composition at 723oC results in formation of ________
a) Ledeburite
b) Sphereoidite
c) Pearlite
d) Bainite
View Answer
Explanation: The eutectic reaction of cast iron occurs at 1148oC. Below the eutectic temperature, the cast iron consists of austenite crystals and ledeburite. Cooling of this alloy below 723oC transforms austenite into pearlite.
10. Heating of 4.8% cast iron at _______ results in the formation of liquid metal.
a) 450oC
b) 650oC
c) 950oC
d) 1450oC
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Explanation: If a sample of 4.8% cast iron is heated to about 1450oC for a sufficient time, its structure becomes a homogeneous liquid metal. If this cast iron is slowly cooled, cementite crystals nucleate and grow in the liquid phase.
11. Transformation of hypoeutectic cast iron is applicable for the composition of cast iron of ________ carbon.
a) 2.0-4.3%
b) 4.3%
c) 4.3-5.0%
d) Over 5%
View Answer
Explanation: Transformation of hypoeutectic cast iron can be seen for the composition of cast iron between 2.0-4.3%. For eutectic cast iron, this composition is 4.3% carbon, whereas, for hypereutectic cast irons, it is 4.3-5.0% carbon.
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