Steelmaking processes: pick the single correct statement about open-hearth and Bessemer practices. (Focus on homogeneity and impurity removal, especially phosphorus and sulphur.)

Difficulty: Medium

Correct Answer: Engineers prefer open-hearth steel for structural work because it is more homogeneous and better controlled.

Explanation:


Introduction:
This question contrasts classic steelmaking routes. Open-hearth (Siemens–Martin) historically offered superior control over temperature and composition, yielding homogeneous steels favored for structural members. Bessemer routes varied in impurity removal capability depending on lining (acid vs basic).


Given Data / Assumptions:

  • Open-hearth permits prolonged refining and sampling.
  • Bessemer's rapid blow limits fine compositional control.
  • Phosphorus removal requires a basic slag; sulphur is more difficult and typically not removed effectively in Bessemer.


Concept / Approach:
Homogeneity and control are key in structural steel. Historically, open-hearth produced reliably uniform steel, while phosphorus removal is effective only with basic linings (Thomas process). Sulphur removal is limited and usually addressed in other stages or by selecting low-S raw materials.


Step-by-Step Solution:

1) Evaluate A: claims open-hearth is less homogeneous — contradicts practice; reject.2) Evaluate B: aligns with the rationale for structural preference — accept as correct.3) Evaluate C: sulphur removal is not effectively handled by Bessemer; reject.4) Evaluate D: basic Bessemer is specifically developed to handle high-phosphorus iron; reject.


Verification / Alternative check:
Historical specs and texts cite open-hearth's uniformity and the role of basic slags for phosphorus; sulphur control typically requires separate desulphurization or basic open-hearth/BOF practices, not acid Bessemer.


Why Other Options Are Wrong:

  • A: Inverts the widely accepted comparison.
  • C: Overstates Bessemer's ability; sulphur remains problematic.
  • D: Thomas (basic) process is precisely to treat high-P pig iron.


Common Pitfalls:
Assuming “all processes remove all impurities”; ignoring the difference between acid and basic linings; conflating phosphorus and sulphur behavior in slag chemistry.


Final Answer:
Engineers prefer open-hearth steel for structural work because it is more homogeneous and better controlled.

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