Dependence of the Clogging Possibility of the Submerged Entry Nozzle during Steel Continuous Casting Process on the Liquid Fraction of Non-Metallic Inclusions in the Molten Al-Killed Ca-Treated Steel

Authors :: Weijian Wang
Ying Ren
Lifeng Zhang
Weifu Li
Yi Wang
Source :: Metals, Vol 10, Iss 1205, p 1205 (2020), Metals, Volume 10, Issue 9
Publication Year :: 2020
Publisher :: MDPI AG, 2020.
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 cos&theta N&minus S+cos&theta I&minus S&lt 0. With the increase of T.Ca content in steel, the evolution route of inclusions was solid MgO-Al2O3&rarr liquid CaO-Al2O3-MgO&rarr 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&ndash 14 ppm to the 20% liquid inclusion zone of 4&ndash 38 ppm.

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