The name "pig iron" originates from the distinctive way the molten iron was cast into ingots in early foundries, which visually resembled a sow suckling her piglets.
The Historical Origin of the Name
The term "pig iron" dates back to a traditional casting method used before hot metal was directly charged into steel plants. In this process, molten iron was poured into sand molds laid out in a specific configuration.
- The "Sow": A main channel, or runner, would be formed in the sand, into which the hot liquid iron flowed. This central runner was colloquially referred to as the "sow."
- The "Pigs": From this central "sow" runner, smaller, perpendicular channels branched out into individual molds where the iron solidified into ingots. These individual ingots, fed by the main runner, were called "pigs."
The entire arrangement—the large main runner connected to numerous smaller ingots—created a visual analogy to a sow (a female pig) feeding her litter of sucking piglets. This vivid resemblance led to the adoption of the term "pig iron" for these cast ingots, a name that has persisted to this day.
What is Pig Iron?
Pig iron is an intermediate product of iron-making, typically produced in a blast furnace from iron ore. It has a very high carbon content (usually 3.8–4.7%), along with significant amounts of silica, manganese, phosphorus, and sulfur.
| Key Characteristics | Description |
|---|---|
| High Carbon Content | Makes it brittle and not directly usable for most applications without further processing. |
| Primary Use | Historically, the main raw material for producing steel and cast iron. |
| Physical Form | Traditionally cast into small, roughly oblong ingots for easy handling and transport. |
Evolution of Production
While the name remains, modern iron and steelmaking facilities often employ continuous casting methods for hot metal, which are far more efficient than the old sand bed casting. However, when hot metal needs to be stored, transported over long distances, or traded, it is still solidified into ingots that are referred to as pig iron.
