Design of a Submerged Entry Nozzle for Thin Slab Molds Operating at High Casting Speeds

Abstract

A submerged entry nozzle (SEN) for thin slab casters operating at casting speeds as high as 7.5 m/minute was developed based on fundamental grounds of boundary-layer theory and water modeling experiments. Experimental techniques included tracer injection to observe overall fluid flow patterns, high speed video camera and image analysis to follow dynamic changes of meniscus levels and particle image velocimetry to measure water speeds in the mold. This design was compared with two other SEN designs of nozzles under current commercial use at various thin slab casters. Direct comparisons of mathematical simulations and experimental results among the three SEN's evidenced that this new SEN yields very stable flows which are independent from casting speed and nozzle immersion depth. Fluid flow developed by this SEN consists of a double roll pattern without generation of superficial vortices. The two other SEN's yield instable discharging jets due to and excessive shearing effects with the surrounding fluid inducing severe dissipation of kinetic energy which promotes severe tailing effects inducing strong meniscus oscillations. The proposed design has reported good industrial performances and a longer operating life because the slag protection belt suffers less wear thanks to smaller velocities of the bath in contact with the SEN wall.

Flow Behavior in the Slab Mold under Optimized Swirling Technology in Submerged Entry Nozzle

“…That is, slag entrapment does not occur with swirling technique, and some steel grades should be combined with other flow control technique to enhance surface velocity to avoid stagnation on the meniscus. And the casting speed is even 7.5 m/min in some condition, 19) only one technique cannot control the flow good enough. Besides, electromagnetic swirling technology in SEN does not only optimize the whole velocity vectors in the mold but also solves scabbing in the nozzle.…”

“…And it is difficult to measure the velocity distribution in practical continuous casting process, then model experiments using low temperature alloy or water are widely adopted until this day. [18][19][20][21][22][23][24] Therefore, hydromechanical model experiment for slab continuous casting is carried out to understand how to optimize the swirling technology. The swirling flow is generated by mechanical blade as Yokoya et al in this study.…”

Physical Modeling of Asymmetrical Flow in Slab Continuous Casting Mold due to Submerged Entry Nozzle Clogging with the Effect of Electromagnetic Stirring

“…Some properties of mercury and molten steel are listed in Table 2. Froude number, 29,30) Magnetic interaction parameter, 31) and Magnetic shielding number are chosen to guarantee the similar- where u is flow velocity of liquid metal; g is acceleration of gravity; L is characteristic length of model; σ is conductivity of liquid metal; B is magnetic flux density; ρ is density of liquid metal; μ is permeability of liquid metal; f is frequency of the power. According to the same Froude number, the ratio of the actual casting speed and the physical casting speed should be 5 .…”

Influence of Continuous Steel Casting Conditions on Behavior and Stability of Liquid Mold Slag During Slab Casting – Physical Modeling

“…One of the concepts to improve the unit cost of steel production relies on increasing the casting speed. For this purpose, a special funnel-shaped mold for thin slab casting has been developed, enabling casting with speeds exceeding 5.0 m/min [2][3][4][5]. Moreover, attempts have also been made to improve casting efficiency by increasing the speed in the casting of conventional slabs.…”