Abstract: A method for the rapid desulfurization of steel melts having oxygen available for reaction of less than 0.01% wherein the temperature of the melt is raised above 1500.degree. C, and a desulfurizing slag is injected into the melt using a non-oxidizing carrier gas. The slag is in a finely divided state and is specially prepared by mixing calcium oxide, calcium fluoride and aluminum oxide with silicane dioxide and heavy metal oxides, melting the mixture and cooling the melt to prefuse the slag. Thereafter, the prefused slag is comminuted into the finely divided state. This slag has a liquidous temperature such that the particles thereof become liquid at a temperature at least 150.degree. C below that of the steel melt and the particles are sufficiently small such that they become liquid immediately on contacting the melt. The process is advantageous in that it provides more rapid desulfurization and more complete desulfurization than prior art techniques.