During refining of liquid iron to steel , CaO plays various roles, out there which of the following is most important

Options

A. To make a slag with `SiO_2` formed
B. To prevent oxidation of sulphur
C. To prevent higher concentration of phosphorus in steel
D. To make a very fluid slag

Answer

To solve the question regarding the role of CaO during the refining of liquid iron to steel, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question revolves around the refining process of liquid iron into steel, specifically focusing on the role of calcium oxide (CaO).

2. **Identify the Roles of CaO**: CaO is known to play several roles during the refining process, including:
- Acting as a flux to remove impurities.
- Helping in the formation of slag.
- Preventing the absorption of certain elements, such as phosphorus.

3. **Focus on the Most Important Role**: Among the various roles that CaO plays, we need to determine which one is the most significant. The refining process aims to improve the quality of steel by minimizing impurities.

4. **Evaluate the Role of Phosphorus**: Phosphorus is an undesirable element in steel as it can lead to brittleness. CaO helps to prevent the higher concentration of phosphorus in the steel, which is crucial for maintaining the desired properties of steel.

5. **Conclusion**: Based on the analysis, the most important role of CaO during the refining of liquid iron to steel is to prevent the higher concentration of phosphorus.

6. **Select the Correct Option**: Given the options provided in the question, we conclude that the correct answer is option C.

### Final Answer:
The most important role of CaO during the refining of liquid iron to steel is to prevent the higher concentration of phosphorus in the steel. Therefore, the correct option is C.

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