Slag consists of oxidic materials which are largely insoluble in molten metals, and
instead separate from them to form a separate layer on top of the molten metal.
A distinction is made between basic and acidic slag.
Function and reuse
Slag has a lower density than the metal, which is why it forms a separate layer on top of it; the slag layer also insulates the melt thermally and shields it from atmospheric oxygen[1]. Processed metallurgical slag is widely reused as a secondary raw material, for example as ground granulated blast-furnace slag in cement production or as aggregate in road construction[1].
References
- Emergency reference (secondary source): Wikipedia: Slag. Retrieved 27 Aug 2026.