Study on Cleanliness of IF Steel Production for ASP

The total oxygen content,nitrogen content as well as evolution behavior of the inclusions during RH refining and continuous casting in IF steel production were investigated.The following results were found.Firstly,the average total oxygen content and nitrogen content in the slab were 29×10^-6 and 35.7×10^-6 respectively,and calcium treatment were responsible for nitrogen pick-up.Lumpy,bar-like single alumina inclusions and loose groups were observed in steel bath the first minute after Al addition,and the fluid flow enhanced the formation and densification of clusters within the next 1~2 min.The addition of Ti resulted in the formation of Al-Ti-O complex inclusions which were changed into sphere as time passed.77% of the inclusions were between CaO·2Al₂O₃ and CaO·6Al₂O₃ after the calcium treatment.In addition to spherical Ca-Al-Ti-O-S complex inclusions,rectangular or multi-dentate TiN inclusions precipitated during solidification were found in the slab.Ultimately,the macro-inclusions were mainly from entrapment of SEN deposits,ladle drainage sand,mold powder and so on.