Question

Which among the following pairs of percentage of carbon and the property of cast iron is true?

• A. 0.2 to 2.0% C, forms steel alloy
• B. 0.2 to 2.0% C, very soft
• C. 4.0% C, hard and brittle
• D. Less than 0.2% C, very soft

Hint:

Cast iron with a higher carbon content (more than 2%) is generally hard and brittle, while steel with a lower carbon content is more ductile.

Answer 1

The Correct Option is C

Step 1: Understanding the composition of cast iron.
Cast iron is an alloy of iron with a higher carbon content than steel, typically ranging from 2.0% to 4.0% carbon. As the carbon content increases, the hardness and brittleness of the material also increase.
Step 2: Analyzing the options.
(A) 0.2 to 2.0% C, forms steel alloy: This is incorrect because steel contains less than 2.0% carbon, and this option does not accurately describe cast iron.
(B) 0.2 to 2.0% C, very soft: This is incorrect as this range of carbon corresponds to steel, not cast iron, which is not very soft.
(C) 4.0% C, hard and brittle: This is correct. Cast iron with a carbon content of 4.0% is hard and brittle.
(D) Less than 0.2% C, very soft: This is incorrect as such a low carbon content would correspond to wrought iron, which is not cast iron.
Step 3: Conclusion.
The correct answer is (C) 4.0% C, hard and brittle.