Study On The Distribution Of Non-metallic Inclusions In Electrical Si-Steel Slab

The quality of non-oriented electrical Si-steel is seriously effected by the type, quantity, size and distribution of non-metallic inclusions exist in the steel. Currently, the two main deoxidazing processes used to produce electrical Si-steel in domestic steel companies are Al deoxidizing process and Si deoxidizing process. But the research on the distribution of non-metallic inclusions in electrical Si-steel is relatively rare on both Al deoxidizing process and Si deoxidizing process.In this paper, a kind of non-oriented electrical Si-steel from a domestic steel company was taken as a research subject.Through industrial tests and sample analysis, the variation of inclusion type, number and area fraction in tundish and continuous casting slab by different deoxidizing process was systematically studied. Under the conditions of this paper, the main conclusions are as follows:(1) During steady-casting state, the main types of non-metallic inclusions consist of Al2O3, Al2O3-MnS, Al2O3-AIN and Al2O3-MgO by Al deoxidation, the number and area fraction of non-metallic inclusions are 25.9/mm2 and 0.0031% respectively; and the main types of non-metallic inclusions consist of Al2O3, SiO2, Al2O3-SiO2 by Si deoxidation. A small amount of Al2O3-MnS and Al2O3-MgO was also detected simultaneously. The number and area fraction of non-metallic inclusions are 29.2/mm2 and 0.0086% respectively.(2) Non-metallic inclusions, which contain trace of K and Na, were found in the slab of electrical Si-steel during the process of casting starting and casting ending. Compared to steady-casting state, the number and area fraction of non-metallic inclusions increased significantly, which indicates that the slag entrapment and secondary oxidation phenomenon are serious in the continuous casting crystallizer during the process of casting starting and casting ending.(3) During the process of casting starting, ladle change, and casting ending, the number and area fraction of non-metallic inclusions in tundish increased slightly compared to the steady-casting state, which indicates that the flow field of tundish should be further optimized during unsteady-casting states.(4) The reasonable length of cutting head is 6m for Al deoxidation, and 4m for Si deoxidation.