Abstract: A flux powder for use during the continuous casting of steel, containing Portland cement, a fluxing agent and a carbon carrier. The carbon carrier possesses a grain size of less than 1 .mu., the powder having an aluminum oxide content in the range between 2 - 12 percent by weight, and a lime-silica ratio adjusted between 0.7 and 1.0 through the addition of quartz powder. The carbon carrier is carbon black containing carbon in an amount of 2 - 8 percent by weight, and wherein the carbon black is present as powder carbon black. The powder carbon black can be in the form of lamp black.