Question

Carbon content of pig iron made by blast furnace is

• A. 3.5 to 4.2
• B. 2.3 to 3.5
• C. 4.0 to 5.2
• D. 0.8 to 1.8

Hint:

Memorize the approximate carbon content for different iron-carbon alloys:

• Pig Iron: \(\sim\)3.5% - 4.5%

• Cast Iron: 2.11%

• Steel: \(\sim\)0.02% - 2.11%

• Wrought Iron: 0.08%

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Pig iron, also known as hot metal, is the immediate product of smelting iron ore in a blast furnace. It is a crude, high-carbon form of iron. The environment inside the blast furnace hearth is extremely hot (around 1500°C) and rich in carbon from the coke. Under these conditions, the molten iron becomes saturated with carbon.

Step 2: Detailed Explanation:
The amount of carbon that can dissolve in liquid iron is a function of temperature. In the blast furnace hearth, the liquid iron is in direct contact with incandescent coke, leading to maximum carbon dissolution.

• The iron-carbon eutectic point is at 4.3% carbon. The composition of pig iron is typically around this point.

• The range

3.5% to 4.2% (or sometimes cited up to 4.5%) is the standard accepted carbon content for pig iron. It also contains other elements like silicon, manganese, phosphorus, and sulfur.

• Option (B) 2.3 to 3.5% is more typical for cast irons, which are produced by remelting pig iron.

• Option (C) 4.0 to 5.2% is too high. The solubility of carbon in iron does not typically exceed the eutectic composition of 4.3% under blast furnace conditions.

• Option (D) 0.8 to 1.8% is the range for high-carbon steels.


Step 3: Final Answer:
The typical carbon content of pig iron produced by a blast furnace falls within the range of 3.5 to 4.2 percent.