granulated steel

Granulated steel is steel produced from pig iron that has been broken into small pellets or granules before remelting and refining. The granulation step, typically achieved by pouring molten pig iron into water or by mechanical crushing of solidified pig iron, increases surface area and makes the subsequent melting and chemical treatment more efficient. This approach sits between direct pig iron casting and modern scrap-based steelmaking, useful when controlling the composition of the charge is critical.

The granulation itself is a physical preparation stage. Water-granulated pig iron forms small, irregular fragments as the liquid metal cools rapidly on contact with water; mechanical granulation breaks cooled pig iron into coarser, more uniform chips or pellets. Either method yields a material with far more surface area per unit weight than a solid pig iron ingot, which accelerates oxidation and diffusion during the remelting phase in a cupola, electric furnace, or other remelting vessel.

Granulation allows the steelmaker to burn off excess carbon, silicon, and other impurities more readily than would occur if solid pig iron were simply remelted. The increased surface area exposes more of the charge to oxygen and flux action. This is especially valuable when the pig iron composition is high in silicon or when precise final composition is required without excessive oxygen injection or scrap dilution. The practice was more common before electric arc furnaces and consistent scrap supplies became standard.

Modern use of granulated steel is limited. Contemporary steelmaking typically relies on scrap, direct reduced iron, or controlled pig iron addition to charge materials. However, granulation remains relevant in foundries and secondary steel mills where pig iron of known composition is a primary feedstock and remelting efficiency justifies the granulation step. The term itself is declining in English-language technical literature, having been largely superseded by more specific descriptions of the raw materials and melting method used.