Formation behavior of ar bubbles on reaction product layer between porous submerged-entry nozzle and molten steel deoxidized by Al and/or Ti

To investigate Ar bubble formation behavior on reaction product layers with a Ti addition to Al-killed steel, tests were performed to gauge the reaction between molten steels and the inner layer of submerged-entry nozzles (SEN) with and without Ar gas purge. Molten steel chemistry, the microstructure and chemistry of reaction product layer, bubble shape and wettability were compared among the tested runs with Al and/or Ti deoxidation. Air bubble formation was observed on the actual SEN inner layer with sliding gate in water model tests. Reaction product layers grew thick and porous with Al-killed steel. Conversely, the layers grew thin and dense with Al-Ti killed steels. Ti-killed steel exhibited the thinnest product layer. Layer thickness appeared to be related to the wettability of steel on the product layers since Al-killed steel exhibited the lowest wettability and Ti-killed steel the highest among the three cases. Ar purge did not have much effect on the reaction behaviors of the tested steel grades. However, reaction product layer formation was suppressed by forming a wide hemispheric bubble in the Al-killed run, while the [T2] addition to Al-killed steel hardly suppressed it due to lack of bubble formation In the SEN delivery system, the [T2] addition to Al-killed steel is predicted to shorten the steel ejection zone for bubble formation toward the sliding gate on the SEN inner wall.