Secondary metallurgical slag (SECS) is generated during production and refining of high-quality steels by secondary metallurgical processes. Today, the production of different grades of high-quality steels without metallurgical processes like alloy handling, degassing, heating, stirring and decarburisation is unimaginable.

The crude steel from basic oxygen or electric arc furnaces is treated in order to achieve the required chemical composition and appropriate temperatures for casting. For these purposes different processes are applied and thus different slag types can be generated. Examples include slags form processes like Ladle Furnace treatment (LF), Vacuum Degassing (VD), Argon Oxygen Decarburization (AOD) and Vacuum Oxygen Decarburization (VOD). 

Secondary metallurgical slag (SECS) typically have high CaO-contents and low oxidation levels. Some of these slags can chemically disintegrate to a fine powder and therefore are used as fertiliser. Coarse grained SECS is usually recycled in other metallurgical processes.