Abstract: A method of continuously casting steel in an open-bottom mould, with an addition of aluminum to molten steel, as the latter enters the mould, includes the addition of a fluxing agent to the molten steel, as the latter enters the mould, to fluidize viscous slags and thereby to mitigate detrimental surface characteristics which would otherwise be produced in the steel, when cast, as a result of such slags. Preferably, the fluxing agent is a metal oxide, e.g. manganese oxide, silicon oxide, boron oxide or sodium oxide, or a mixture of metal oxides, provided as a coating on an aluminum wire, which wire may constitute the aluminum addition. The invention further includes a steel additive comprising such a coated aluminum wire.