Steelmaking — The Duplex Process The “duplex process” of steelmaking refers to a combination of which two primary processes?

Introduction / Context:
Before basic oxygen furnaces became dominant, duplexing was used to optimise refining, productivity, and cost by splitting the steelmaking operation across two vessels. Understanding which combinations were employed explains how phosphorus and sulphur were best removed while exploiting the rapid decarburisation capability of the Bessemer process.

Given Data / Assumptions:

• Historical steelmaking context: Bessemer and open-hearth practices.
• Objective: fast initial refining followed by precise finishing with impurity control.
• Phosphorus removal requires a basic slag environment.

Concept / Approach:
In a common duplex route, metal was first blown in an acid Bessemer converter for rapid decarburisation, then transferred to a basic open-hearth furnace for finishing, including phosphorus and sulphur removal using basic slags. This pairing balanced speed with chemical control, producing cleaner steel than a single-stage blow could achieve economically at the time.

Step-by-Step Solution:
Stage 1: acid Bessemer → quick decarburisation.Stage 2: basic open hearth → refine chemistry; remove P and S with basic slag.Outcome: improved composition control and quality.Thus, “acid Bessemer and basic open hearth” correctly names the duplex combination.

Verification / Alternative check:
Metallurgical histories describe duplexing variants; this acid-to-basic sequence is the widely cited classic arrangement.

Why Other Options Are Wrong:
Other pairings do not provide the desired combination of rapid blow and effective phosphorus removal.

Common Pitfalls:
Assuming both stages must use the same slag practice; in duplexing, roles are intentionally different.

Final Answer:
acid Bessemer and basic open hearth