Effect of Refractory Materials on Inclusion Deposition of Immersion Nozzle in Continuous Casting and Mathematical Modeling of Inclusion Deposition

Abstract

New immersion nozzle materials preventing inclusion deposition have been investigated by laboratory scale test. A new mathematical model has been proposed to explain the behavior of inclusion in the turbulent boundary layer near the nozzle and deposition rate of inclusions in the molten steel has been numerically evaluated.
(1) The quantity of deposited inclusions has drastically decreased in the materials composed with high Al₂O₃ in comparison with Al₂O₃-C one. There is no deposition of inclusions on the material composed with pure Al₂O₃, (Sapphire).
(2) About 30% of the inclusions less than 20μm in diameter reach at laminar sublayer and they are forced to move onto the refractory wall due to the interfacial tension gradient between inclusions and molten steel, formed by concentration gradient of silicon etc. in molten steel.
(3) Deposition rate of inclusions in the molten steel was evaluated to be 0.75μm/s (1.35 mm thickness in 30 min) which is almost equal to the experimental results.