Model experiment of swirl effect in bottomless immersion nozzle on molten steel flow in slab CC mold

摘要

The characteristics of molten steel jet flowing out from the immersion nozzle in the continuous casting mold control the flow pattern in the mold, thereby strongly influencing the quality and productivity of the cast steel slabs. We proposed a new method to establish a reasonable flow pattern in the mold by imparting a swirling motion to the flow in the immersion nozzle without the bottom. The following results were obtained from a water model study. (1) A quite stable swirling flow being established in the immersion nozzle without the bottom when the swirling velocity exceeded a critical value of 0.8 m/s, under this condition there existed no separation on the inner wall of the immersion nozzle. (2) When the swirling velocity was higher than 0.8 m/s, the fluid on the symmetry plane of the immersion nozzle moved along the curved inner wall of the nozzle. Accordingly, the outlet-flow was directed outwards as well as downwards, while a weak upward flow, i.e., inflow was observed around the vertical nozzle axis near the outlet of the nozzle. As a whole, the fluid flow near the guide plane of the nozzle was directed downwards. (3) The fluctuation of the surface flow, i.e., the flow on the meniscus of the mold was strongly suppressed due to the appearance of the S-shaped flow pattern in the transverse sections. As a result, swirl motions around the immersion nozzle were also suppressed. In addition, both the fluctuations of the mean velocity components and the turbulence components of the flow in the mold became very small, being preferable conditions for continuous casting.