Process for insulating molten steel during continuous casting

In a process for producing high quality steel through a continuous casting process, said process including pouring molten steel from a ladle into a tundish and then into a mold, wherein an slag is provided on top of the molten steel in the tundish to absorb impurities and to help insulate the molten steel therein, the improvement which comprises

• providing a basic slag which comprises a combination of CaO, MgO, Al.sub.2 O.sub.3, and a reactive metal oxide selected from the group consisting of Li.sub.2 O, SrO.sub.2, TiO.sub.2, Na.sub.2 O, BaO, wherein the composition contains SiO.sub.2 in an amount less than 15% by weight, wherein the slag maintains a melting and crystallization temperature of at least 1450.degree. C. while absorbing and retaining at least 10% by weight Al.sub.2 O.sub.3 therein;
• spreading the slag over the molten steel in the tundish while maintaining the temperature of the molten steel at least at 1535.degree. to maintain the fluidity of the slag;
• and
• retaining the molten steel in the tundish for a sufficient period of time to provide absorption of all excess Al.sub.2 O.sub.3 from the molten steel into the slag.