Cupola practice — charge composition control: Evaluate the statement: “In a cupola furnace, the proportion of steel scrap in the charge controls the grade of cast iron produced.”

Introduction / Context:
The cupola is a shaft furnace used to melt and refine cast iron. The final composition and hence the grade of iron depend strongly on the charge makeup, including pig iron, steel scrap, foundry returns, coke, and flux. Understanding how steel scrap proportion influences chemistry is essential for controlling carbon and silicon levels.

Given Data / Assumptions:

• Cupola charge may include pig iron, steel scrap, and returns, plus coke and flux.
• Steel scrap is relatively low in carbon and silicon compared to pig iron.
• Target grades vary by required carbon, silicon, and mechanical properties.

Concept / Approach:
Increasing steel scrap in the charge dilutes carbon and silicon, pushing the melt toward lower carbon and silicon contents unless compensated by carburisers and ferrosilicon additions. This directly affects microstructure (e.g., pearlite/ferrite balance) and mechanical properties, thereby controlling the grade produced. Operators tune additions and the scrap ratio to hit specification.

Step-by-Step Solution:
Recognize that steel scrap introduces low C and low Si to the bath.More scrap → lower base C and Si levels.Adjustments via carburiser/ferrosilicon set final composition and grade.Thus, the steel scrap proportion is a key lever in grade control; the statement is correct.

Verification / Alternative check:
Foundry practice guides explicitly recommend controlling scrap/pig ratio to meet grade chemistry and hardness targets.

Why Other Options Are Wrong:
Limiting to specific iron types is unnecessary; scrap proportion matters broadly.

Flux influences slag chemistry and sulphur but does not alone fix carbon and silicon to set grade.

Common Pitfalls:
Assuming coke rate or blast alone determines grade; while important, charge chemistry via scrap ratio is fundamental.

Final Answer:
Correct