A kind of covering agent for molten steel and its preparation method. The components of the steel cover agent (wt%) are: 1~8 Na2O, 0~7 F-, 3~40 Al2O3, 5~40 CaO, 0~2 Fe2O3, 0.5 to 10 foaming agent, 1~20 binder and residual MgO and SiO2, wherein, (CaO+MgO) /SiO2 is 2~10. The covering agent is porous, and its particle size is 0.1 ~ 15mm. The preparation method of the invention comprises the following steps: the covering agent in the stirred tank blowing agent and binder water mixing liquid is prepared, using mechanical stirring the liquid and the covering agent for the other components of mix mixing slurry, the slurry forming, drying, crushing, screening. When the steel is covered by ladle and tundish in the steel mill, it can realize good heat preservation, absorb inclusion, avoid molten steel and other metallurgical functions. The preparation method is simple, and the preparation cost can be saved.
Appearance: light blue solid particles
Grain size: 20 - 60 mesh >95%, 18 - 40 mesh >95%,
50 - 70 mesh >95%, 40 - 60 mesh >95%
Bulk density: 1.2g/cm3
Ingredients: total effective component >99%
SiO2:69 - 76%
AI2O3:8 - 14%