Wrought Iron and Pig Iron – Identify the Incorrect Statement Among the following statements about wrought iron quality and pig iron manufacture, which one is NOT correct?
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ABlisters in finished wrought iron are caused by reaction between iron oxide and carbon producing gas
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BRough edges on finished wrought iron are due to red shortness at forging temperatures
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CCharcoal pig iron can be manufactured from magnetic ore (Fe3O4) in suitable furnaces
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DNon-sulphurous fuel is not necessary for manufacturing wrought iron
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EAll statements are correct
Answer
Correct Answer: Non-sulphurous fuel is not necessary for manufacturing wrought iron
Explanation
Introduction:Process metallurgy questions often mix facts about defects and fuel/ore choices. Here, the objective is to detect the incorrect statement that conflicts with established practice for making wrought iron and pig iron.
Given Data / Assumptions:
- Wrought iron historically contains slag stringers and is forged at high temperature.
- Pig iron can be produced from various iron ores depending on furnace practice.
- Sulphur in fuel/charge promotes red shortness (hot brittleness) in iron products.
Concept / Approach:
Quality wrought iron demands minimizing sulphur pickup. Using sulphur-bearing fuel results in red shortness and ragged edges, so non-sulphurous fuel is in fact necessary. Statements on blistering (gas from reactions during finishing) and rough edges (red shortness) are consistent with metallurgical behavior.
Step-by-Step Solution:
1) Evaluate (a): Blisters from gas (e.g., CO) generated by reaction between oxides and carbon during working—metallurgical texts support this.2) Evaluate (b): Red shortness (often from sulphur) causes ragged edges in wrought iron—consistent with observations.3) Evaluate (c): Magnetite (Fe3O4) can be reduced to make pig iron, including charcoal routes—possible in suitable operations.4) Evaluate (d): Claims non-sulphurous fuel is not necessary—this contradicts practice; low-sulphur fuel is preferred to prevent hot brittleness.Verification / Alternative check:
Historical puddling/finery and later processes emphasize low sulphur fuels; quality standards penalize sulphur content for wrought products.
Why Other Options Are Wrong:
(a) and (b) describe known defect causes. (c) is feasible with appropriate furnace chemistry. (e) cannot be correct because (d) is incorrect.
Common Pitfalls:
Assuming “all of the above” when one subtle fuel-quality statement is wrong; overlooking the specific role of sulphur in red shortness.
Final Answer:
Non-sulphurous fuel is not necessary for manufacturing wrought iron