Answer: Deoxidises and desulfurises the melt: Mn + S → MnS (slag); Mn + FeO → MnO + Fe.
- A Deoxidises and desulfurises the melt: Mn + S → MnS (slag); Mn + FeO → MnO + Fe
- B Deliberately increases the carbon content of the finished steel under typical conditions
- C Acts mainly as a flux to lower the slag's melting point according to standard textbooks
- D Lowers the overall temperature required during steel production in general practice
Correct answer: A. Deoxidises and desulfurises the melt: Mn + S → MnS (slag); Mn + FeO → MnO + Fe
Explanation: Manganese (as FeMn) is added to steel to remove dissolved oxygen (deoxidation) and sulfur (desulfurisation), preventing hot shortness and porosity.
An Ellingham diagram plots ΔG° of oxide formation against temperature for different metals; whichever line is LOWER (more negative ΔG°) at a given temperature reduces the oxide of any metal whose line sits above it - the basis of carbon reduction (Fe, Zn) vs electrolytic reduction (Al, Mg, Na) decisions.
Concept context
The science of extracting metals from ores and refining them for use. Covers concentration methods, reduction techniques, refining processes, and the thermodynamic principles that govern metal extraction.