Steelmaking processes — choose the correct statements regarding heat supply and oxidation mechanisms in basic Bessemer, open-hearth (Siemens–Martin), and Siemens processes.

Introduction / Context:
Classic steelmaking routes include the Bessemer converter and the open-hearth (Siemens–Martin) furnace. Understanding where heat comes from and how oxidation occurs is foundational to process classification and historical exam questions. Each method relies on different thermal balances and oxidants to refine pig iron into steel.

Given Data / Assumptions:

• “Basic Bessemer” refers to the basic-lined (Thomas) converter variant.
• Open-hearth refers to regenerative, reverberatory furnaces (Siemens–Martin).
• “Siemens process” here alludes to Siemens–Martin practice using ore as an oxidant.

Concept / Approach:

In the Bessemer converter, oxidation of impurities within the metal (C, Si, Mn, P in the basic process) releases substantial heat, so the metal itself supplies the heat to keep the bath molten—colloquially phrased as “the steel heats the converter.” In the open-hearth process, the furnace (regeneratively heated by preheated air/gas) supplies external heat to the steel bath. In Siemens–Martin practice, iron ore can be charged to provide oxygen, oxidizing impurities in pig iron to refine the metal. Therefore, all three statements are acceptable in the standard exam framing.

Step-by-Step Solution:

Verification / Alternative check:

Metallurgical histories and process descriptions corroborate these simplified distinctions between converter and open-hearth operations.

Why Other Options Are Wrong:

Selecting only (a), (b), or (c) omits other equally true statements, making “all the above” the comprehensive choice.

Common Pitfalls:

Interpreting (a) too literally: it means heat is generated in the bath, not that solid steel is a fuel. Also, not distinguishing between acid and basic linings in Bessemer practice.

Final Answer:

all the above