Abstract
In the current study, the nozzle clogging behavior and inclusion composition in Al-killed Ca-treated steels were observed to investigate the relationship between the liquid fraction of non-metallic inclusions and the clogging possibility of the submerged entry nozzle. Clogging materials were mainly MgO-Al2O3 with less than 20% liquid phases, while most of the inclusions were full liquid CaO-Al2O3-MgO in tundish at the casting temperature. Thus, it was proposed that the nozzle clogging can be effectively avoided by modification of solid inclusions to partial liquid ones rather than full liquid ones. There was a critical value of liquid fraction of inclusions causing the nozzle clogging. A critical condition of the inclusion attachment on the nozzle wall was a function of cosθN−S+cosθI−S<0. With the increase of T.Ca content in steel, the evolution route of inclusions was solid MgO-Al2O3→liquid CaO-Al2O3-MgO→solid CaS and CaO. To avoid the clogging of the submerged entry nozzle (SEN) under the current casting condition, the appropriate T.Ca concentration range in Al-killed Ca-treated steels can be enlarged from the 100% liquid inclusion zone of 10–14 ppm to the 20% liquid inclusion zone of 4–38 ppm.
Highlights
The submerged entry nozzle (SEN) is the key lining refractory to connect the tundish and the mold during steel continuous casting (CC) [1,2,3]
With the CaO content in CaO-Al2 O3 -MgO inclusions increased to 20%, the contact angle between inclusion and steel is still larger than 110◦, indicating the higher clogging possibility of solid inclusions
The nozzle clogging behavior and inclusion composition in Al-killed Ca-treated steels were observed to investigate the relationship between the liquid fraction of inclusions and the clogging possibility of the submerged entry nozzle
Summary
The submerged entry nozzle (SEN) is the key lining refractory to connect the tundish and the mold during steel continuous casting (CC) [1,2,3]. Inclusions in Al-killed Ca-treated steels were modified to full liquid by Ca treatment to avoid the SEN clogging [26,27,28], while the insufficient and excess Ca can only partially modify inclusions to liquid ones [29,30]. The partial liquid calcium aluminate was the target composition of inclusions in Al-killed Ca-treated steels [31]. It is still unclear if the partial liquid Al2 O3 -CaO inclusions clogged the SEN during the casting process. To reveal the relationship between inclusion liquid fraction and submerged entry nozzle clogging during the CC of Al-killed Ca-treated steels, the nozzle clogging behavior and inclusion composition were analyzed using automated SEM/EDS inclusion analysis (ASPEX). The T.Ca in the current Al-killed Ca-treated steel was in the range of the 9–12 ppm
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