Measurements of Molten Steel Surface Velocity and Effect of Stopper-rod Movement on Transient Multiphase Fluid Flow in Continuous Casting

Abstract

Surface velocity of the molten steel in the mold is critical to final product quality during continuous casting of steel, and is one of the few flow parameters that can be measured in the plant to validate fluid flow models. Surface velocity was measured using two different sensors: Sub-meniscus Velocity Control (SVC) devices and nail dipping, to evaluate their performance, and to quantify surface velocities in a commercial steel caster under different casting speeds, argon gas fractions, and mold widths. A correlation between the height difference of the solidified lump on the nail and surface velocity is confirmed and extended. Reasonable agreement between the two sensing methods was obtained, both in trends and magnitudes for both time-averaged velocity and transient flows. Transient CFD models are applied to simulate multiphase flow of steel and gas bubbles in the Submerged Entry Nozzle (SEN) and mold and are validated with nail dipping measurements. To obtain the transient inlet boundary conditions for the simulation, two semi-empirical models, a stopper-position-based model and a metal-level-based model, predict the liquid steel flow rate through the SEN based on recorded plant data. The model system was applied to study the effects of stopper rod movements on transient flow in the SEN and mold. Mold level fluctuations were calculated using a simple pressure method and compared with plant measurements. The results show that severe stopper rod movements cause significant disturbances of the meniscus level, which may cause slag entrapment, leading to sliver defects in the final product.

Physical and Numerical Investigations of Mould Flux Entrainment into Liquid Steel

“…empirical formula (4) yields the correct trend in the increase of the critical velocity with increasing oil viscosity; however, the calculated values are unrealistically large. The closest to the author's investigation results is empirical model (5). The discrepancies between the author's investigations and other empirical models provided in the literature can be explained by the following factors: the different experimental technique employed, the differences in interfacial boundary geometry and the sensitivity of the phenomenon in question on the interfacial tension and liquids viscosity.…”

“…For this reason, the behaviour of liquid slag layer on the liquid steel surface in mould is an important and often investigated problem of modern continuous steel casting process. The research take different forms, including plant measurements [4,5], investigations -basing on the similarity numbers: Webber (We), Froude (Fr), Reynolds (Re) and Capillary (Ca) -using the oil-water physical models [6,7] and also numerical simulations [8,9].…”

Effect of Submerged‐Entry Nozzle (SEN) Design on Fluid Flow and Heat Transfer in a Thin‐Slab Steel Caster

“…The mean and variations of the surface velocities are very close to but slightly lower than previous measurements by Yavuz with a wider mold width, which leads to higher surface velocities under the same casting speed. This observation is in line with previous work by Liu and Thomas …”

Review on Modeling and Simulation of Continuous Casting

“…With higher gas fractions, it is more accurate to solve an extra continuity equation and complete extra set of transport equations for the gas phase, coupled together with the fluid continuity and transport equations, in order to enforce the total volume fraction to equal 100% everywhere. This Eulerian–Eulerian approach has been applied successfully in many previous studies of argon‐steel flow in the continuous casting mold region . Asymmetric, oscillating flow is observed if gas fractions are excessive .…”

“…Computational models of the nozzle have included the slide-gate, [62][63][64] the stopper rod, [65,66] or the refractory-funnelnozzle semi-open-pouring flow control system, [67] which greatly affects the flow in both the nozzle and the mold cavity. [68] Many models have simulated the important effects of argon gas injection on turbulent flow inside the nozzle, [62][63][64] and also in the mold.…”