Inclusion Behavior of LCAK Steel in Tundish Pouring Process

The variations of inclusion characteristic of LCAK in tundish and normal slabs produced by BOF-Ar stationCC processes were studied by systematically sampling in different pouring time and nomal slabs of steel production. Analysis methods mainly include total oxygen and nitrogen content analysis, optical microscopy, scanning electronic microscope(SEM), and energy dispersive X-ray spectroscopy(EDS). The results show that: Total oxygen content at the starting and end of ladle pouring is higher than the middle pouring, which indicate that there exists re- oxidation during ladle change practice. The inclusions in tundish and normal slabs are classified into three types according to their morphology and composition: alumina inclusions; MnS inclusions; tundish flux inclusions or ladle slag inclusions. Inclusions of tundish and slab mainly contain Al2O3 inclusions with the size of 1-4 μm,also there are lots of MnS inclusions in the slab result in the rising of the number density. The number of bubble+alumina inclusions increases on steel of higher sulphur content. To sum up, at the stage of starting and end of pouring after the exchange of ladle, re-oxidation is the main reason which restrain the quality of the slab.Meanwhile, the sulfur content in steel should be controlled in a certain range in order to decrease the bubble+alumina inclusions and also avoid the precipitation of MnS inclusions during the solidification process.