Maas Hermann, Abratis Horst, Raeune Claus: Method of treating metal melts with a purging gas during the process of continuous casting. Rheinstahl Huettenwerke, Kleeman Werner W, June 3, 1975: US3886992 (75 worldwide citation)

A method of, and apparatus for, treating metal melts during continuous casting, wherein the teeming metal is enclosed to a point below the surface of the metal pool in the continuous casting mold to avoid contact with the ambient atmosphere and the surface of the pool is covered with a layer of slag ...