Ironmaking — identify the variety of pig iron typically used as the charge stock for manufacturing wrought iron in traditional processes.

Introduction / Context:
Pig iron—the product of the blast furnace—is categorized by silicon content, carbon state (combined vs graphitic), and appearance. Different downstream refining processes (wrought iron puddling, basic steelmaking, foundry casting) prefer particular pig varieties. The question focuses on which pig iron suits the conversion to wrought iron, a low-carbon, slag-fibred iron once widely used for structural work and forgeables.

Given Data / Assumptions:

• Wrought iron production (e.g., puddling or finery processes) requires feed with low silicon and low graphitic carbon.
• Pig iron varieties include grey, white, mottled, and special designations (e.g., Bessemer pig).
• Refining aims to decarburize and remove impurities efficiently.

Concept / Approach:

White forge pig has most carbon in the combined form (Fe₃C) and contains comparatively low silicon. This composition facilitates rapid oxidation of carbon and impurities during puddling/finery without excessive slag foaming or graphitic inclusions. Grey or foundry pig, rich in silicon and graphitic carbon, is suited to casting, not wrought iron refining. Mottled pig is intermediate and less desirable. “Bessemer pig” is tailored for steelmaking in the Bessemer converter (phosphorus/ silicon constraints depending on process), not for wrought iron.

Step-by-Step Solution:

Verification / Alternative check:

Historical metallurgy texts specify “white forge” pig as the preferred feed for puddling to wrought iron due to oxidation kinetics and slag behaviour.

Why Other Options Are Wrong:

Bessemer pig — Intended for steelmaking constraints, not wrought iron.
Grey/foundry pig — High Si and free graphite → poor for refining to wrought.
Mottled pig — Intermediate properties; not optimal.

Common Pitfalls:

Assuming any low-cost pig is interchangeable; overlooking the role of silicon and carbon form in refining reactions and slag control.

Final Answer:

White forge pig