250+ TOP MCQs on Plain Carbon Steels and Answers

Machine Design Multiple Choice Questions on “Plain Carbon Steels”.

1. Ductile cast iron is
a) Also called nodular cast iron
b) Also called spheroidal graphite cast iron
c) Carbon is present in form of spherical nodules
d) All of the mentioned
Answer: d
Clarification: Ductile cast iron, also called as nodular cast iron or spheroidal cast iron consists of carbon in the form of spherical nodules in a ductile matrix.

2. Grey Cast iron is formed when
a) Carbon content in the alloy exceeds the amount that can be dissolved
b) Carbon content in the alloy is less than the amount that can be dissolved
c) Carbon content in the alloy is equal to the amount that can be dissolved in the alloy
d) None of the mentioned
Answer: a
Clarification: Grey Cast iron is formed only when carbon is present exceeds the solving capacity.

3. White cast iron is formed when
a) Graphite flakes are formed
b) Most of the carbon content in the alloy forms iron carbide
c) No iron carbide is formed
d) None of the mentioned
Answer: b
Clarification:White cast iron is formed when most carbon in alloy forms iron carbide and there are no graphite flakes.

4. The term high alloy steels is used for alloy steels containing more than ___ of alloying elements.
a) 10%
b) 20%
c) 50%
d) 70%
Answer: a
Clarification: The term high alloy steels is used when alloying elements exceed 10%.Low and medium alloy steels are those when this figure is less than 10%.

5. Which of the following are true about low carbon steels?
a) Carbon content < 0.3%
b) Also called as mild steel
c) Are soft and ductile
d) All of the mentioned
Answer: d
Clarification: Low carbon steels contain carbon <0.3%. Because of low carbon, it is soft and ductile.

6. Which of the following are true for high carbon steels?
a) Carbon content=0.4%
b) Respond readily to heat treatments
c) Have much ductility as compared to low and medium carbon steels
d) Easy to weld
Answer: b
Clarification: High carbon steel have carbon % >0.5 and hence have less ductility. They are difficult to weld.

7. Which of the following are true?
a) 7C4 grade steel is more ductile than 10C4
b) Yield strength of 40C8 is greater than of 30C8
c) Hardness of 30C8 is greater than of 40C8
d) None of the mentioned
Answer: a
Clarification: The number before “C” indicates measure of carbon. Hence a) is true as higher the carbon, lower the ductility.

8. In the designation “xCb” which of the following are true?
a) x indicates 100 times the average % of carbon
b) b indicates 100 times the average percentage of manganese
c) x indicates 10 times the average percentage of carbon while b indicates 100 times the average percentage of manganese
d) b indicates 100 times the average % of carbon
Answer: a
Clarification: X indicates 100 times carbon % and b indicates 10 times manganese %.

9. Which of the steel in given options is best suited for auto mobile bodies and hoods?
a) 7C4
b) 10C4
c) 30C8
d) 40C8
Answer: a
Clarification: For automobile application like manufacturing bodies, ductile material is preferred.

10. Which of the following steel given in options respond fastest and easily to heat treatment?
a) 7C4
b) 10C4
c) 30C8
d) 40C8
Answer: d
Clarification: Alloys with higher carbon % respond willingly to heat treatment.

11. Which of the following given steels is popular with the name of machinery steel?
a) Low carbon steel
b) Medium carbon steel
c) High carbon steel
d) None of these
Answer: b
Clarification: It has ductility and can be heat treated easier than low carbon steel.