PURPOSE: To prevent the generation of the streak flaws of a steel ingot obtd. by using the oxidized film preventive agent for a high-Mn steel ingot contg. specific ratios of C, SiO2, Al2O3 and CaO.

CONSTITUTION: The oxidized film preventive agent for the high-Mn steel ingot consisting essentially, by weight%, of ≤10 C, ≤5 SiO2, 20 to 50 Al2O3 and 20 to 50 CaO is used. The C is a component having a function to suppress combustion. The preventive agent dissolves into molten metal and can no longer prevent the oxidation of the surface layer of the steel ingot if the content thereof exceeds 10%. The SiO2 is best if not incorporated into the preventive agent. The content thereof is required to be confined to ≤5wt.%. The Al2O3 and CaO are the components to lower the m.p. of the preventive agent. The need for subjecting the steel ingot to ESR is eliminated.