A

David

Darling

slag

industrial slag

Slag is waste formed as an upper, molten layer in the smelting of ores and refining of metals, notably iron and steel. It consists of impurities, oxides, and ash, with a limestone flux, and serves to remove unwanted substances and to protect the metal from oxidation. Solidified slag is used as aggregate, for road making, and as a phosphate fertilizer.