Abstract: System of a factory for the open casting heats IF steel slab cleanliness variation on the slab level provide the basis for rational judgment, the use of oxygen and nitrogen analysis, quantitative metallographic examination and other tests detect large inclusions of a steel open casting furnace second IF steel slab cleanliness research. The results showed that, at 4 m distance from the dummy bar head in slab w(T.O)=35.3 ×10^-6,w(N)=48.7× 10^-6, microscopic inclusions content was 8.5/mm², steel secondary oxidation serious, which contains trace elements La, microscopic inclusions proportion of Ce, respectively 33 %and 55 % by the ladle slag and tundish slag greater impact. At 16 m distance from dummy bar head, w(T.O)=18.7×10^-6, slab has greatly improved cleanliness. With casting cleanliness is more gentle upturn, 28 m away from the dummy bar head , w(T.O)decreased to 16.3×10^-6, the cleanliness of the slab continuous casting furnace 2, 3 stove heats consistent with normal.

Key words:  IF steel, first heat of a sequence, cleanliness, inclusions