US Patent 7776162 Steels with few alumina clusters

A steel having few alumina clusters prepared by casting liquid steel deoxidized with Al, with the addition of one or more rare-earth metals (REM) selected from the group of Ce, La, Pr and Nd in which:(a) The REM-oxide-content in oxide-based inclusions consisting mainly of alumina and REM-oxides is 0.5 to 15 mass % of said oxide-based inclusions, or(b) The mass ratio of total REM to total oxygen (T.O.), REM/T.O., in liquid steel is not less than 0.05 and not more than 0.5, in addition to (a), or(c) The total REM-content is not less than 0.1 ppm and less than 10 ppm and the dissolved-REM-content is less than 1 ppm.