Abstract: A mold flux for the continuous casting of steel (including ultra low carbon steel) comprises refractory metal oxide, at least one fluxing agent, a binder, and expandable graphite in the amount of 0.3-1.0% by weight, the expandable graphite having a size less than about 80 mesh, and the flux in the form of spherical granules 200-500 microns in diameter. The binder typically comprises between about 8-14% weight soda ash, or between about 4-7% by weight lithium carbonate, or a combination of soda ash and lithium carbonate wherein double the percentage of lithium carbonate plus the percentage of soda ash is between about 8-14%. The flux may additionally include--especially where ultra low carbon steel is being continuously cast--starch and MnO.sub.2 to reduce slag rim, improve thermal insulation, and reduce carbon pickup.

Abstract: A granular mould flux for use in the continuous casting of steel comprises refractory metal oxide, one or more fluxing agents, a binder and 0.1% to 3% by weight based on the weight of the flux of an expanding agent such as expandable perlite, expandable vermiculite or expandable graphite.