Investigation On Behavior Of Inclusions In Steel During The Continuous Casting Process

20#steel and cold-rolling slab steel(LZ06)are two important products of the third Steelmaking factory of Lianyuan Iron and Steel Corporation.This paper aims at the two steels and studies the behavior of inclusion in steel at the process of continuous casting from below six aspects so that some methods can be expected to improve the quality of steel. Addtionally,this paper discussed the function of the tundish used in Luan steel.(1) Inspecting the development of inclusion in melt steel when pouring from ladle to tundish.(2) Inspecting the effect of tundish and the tundish flux on removal of inclusion.(3) Inspecting the development of inclusion in melt steel when flowing from tundish to mould.(4) Inspecting the effect of mould flux on removal of inclusion(5) .Inspecting the sorts ,distribution,size,appearance and origin of inclusion in cast.(6) Inspecting the change of inclusion's size and appearance in cast after rolled The conclusion:1. From ladle to tundish ,the average value of the content of TO in LZ06 is increased 57.6ppm and 142ppm in 20# steel .The average value of the content of N in LZ06 is increased 21.9ppm and 30.6ppm in 20# steel. The reoxidation of melt steel is serious.and many slags of the ladle enter the tundish The result of electrolyzing 20# steel shows the gross of inclusion in melt steel is reduced the half ,which indicates many inclusion is removed in tundish.2.In these four sorts of inclusion-A,B,C and D,most of them are small,which can be seen from the result of metallo graphic examination .the result of probe examination shows the biggest inclusion is only 17.7u m in cast.The two facts can say those big inclusion are maybe removed in tundish by floating or other methods ,which accords with the result of eletrolyzation. These results also show the covering in tundish plays an instrumental role in absorbing inclusion.3. From tundish to mould, the average value of the content of TO is increased 15ppm in LZ06 and 41.6ppm in 20# steel. However ,the average value of the content of N changed litter with 2ppm increased in LZ06 and almost unchanged in20#.These results show the reoxidation in melt steel is reduced and the flux in the mould absorbing inclusions well.4 ^ Comparing the content of TA1 of melt steel in tundish and in cast ,the average value of the content of TAl is decreased from 29.4ppm to 21.8ppm and 7.6ppm is reduced in LZ06 .As for 20#,the value is decreased from 25.4ppm to 18.3ppm and 7.1ppm is reduced.The result gives the further confirmation that the flux in mould absorbed inclusion effectively .5> The main component of inclusions is silicate and sulphide is the second .The main component of sulphide is MnS;Most inclusions are spherical . The outer layer of these spheres is MnS and the inside is silicate .The pure AlaOa inclusion is almost not seen in cast. Among those partical and block inclusions ,most of them are SiO2 and some are MnS and few are FeS;Most inclusions are under lOum.Thoseinclusions which are smaller than 10 u m accout for 94% in the two steels; Quite a few inclusions distribute in the center area of cast and the area which is 1/4 thickness of cast distance from the inside arc of cast ;Most oxidate inclusions derive from ladle slags, covering in tundish and the deoxidation of melt steel.6. After rolled,the spherical inclusions in cast become spindly with MnS in outer layer and silicate in the center. Some plastic inclusions (such as the inclusions whose main component is MnS) become zonal.7. The effect of tundish removing inclusion is remarkable...